designv11-36.json

[
    {
        "image_filename": "designv11_36_0002547_piae_proc_1920_015_011_02-Figure14-1.png",
        "original_path": "designv11-36/openalex_figure/designv11_36_0002547_piae_proc_1920_015_011_02-Figure14-1.png",
        "caption": "FIG. 14.-Clyno Standard Model.",
        "texts": [
            " 13, Plate I-it is to be regretted that on this type at present the ends of the springs are held solidly, and as the spring is compressed they move out of line, or rather, in the normal position they are out of line, and as the spring is further compressed they move into line, which comes to the same thing, as at one position they are being distorted. The carrier is sprung on this machine, so that if an extra passenger at PENNSYLVANIA STATE UNIV on June 5, 2016pau.sagepub.comDownloaded from is carried, the springs on the rear wheel would have to support the extra weight. I n some machines a spring is fitted on each side of the wheel, an example of which is shown in Fig. 14. In this design, i f one spring is made or becomes a little weaker, or has a different set to i t s fellow, or if the deflection ratios are different, it svould piit side strains on the main spindle bearing. One designer told the author that he had ridden such a lnachine for some way nit11 tl spring on one side only, and it had worked quite well; this wonld probably be so for short distances and while the bearing was in good order, but the twisting strains on the bearing mould he severe. The position nould be improved i f the springs were bridged across, with a central point of contact for the spring> and wheel"
        ],
        "surrounding_texts": []
    },
    {
        "image_filename": "designv11_36_0002549_jiee-1.1917.0030-Figure20-1.png",
        "original_path": "designv11-36/openalex_figure/designv11_36_0002549_jiee-1.1917.0030-Figure20-1.png",
        "caption": "FIG. 20.",
        "texts": [
            " Let us consider the root-mean-square distribution of current and energy density or B2 in such a transmission including the transmitting and receiving circuits. The air-gap density on the outer side of the transmitting coil at C is zero as there is no reason why the lines of force should cross the air-gap in the manner shown dotted rather than pass wholly through iron as shown in the full lines. The same applies to the outer side of the receiving coil, also shown dotted. We may therefore conceive the function of the primary coil as being that of increasing the air-gap density from zero at C to\u00bbO A at O (Fig. 20). The primary current density (amperes per cm. length) which is constant is shown in curve II. When the density has reached the value O a at O due to the action of the primary coil, it begins to be reduced by the action of the short-circuited coils as we proceed from O to the right towards p. The current shown in curve II is now reversed, and instead of building up the density to still higher values begins to reduce it again. When we reach /> the remainder of the density is absorbed by the receiving coil, on the further side of which it is again zero"
        ],
        "surrounding_texts": []
    },
    {
        "image_filename": "designv11_36_0002792_paiee.1918.6594157-Figure5-1.png",
        "original_path": "designv11-36/openalex_figure/designv11_36_0002792_paiee.1918.6594157-Figure5-1.png",
        "caption": "FIG. 5 F IG. 6",
        "texts": [
            " T h e rat io \u2014 7 7 ^ - is theredtL fore a rat io of magne tomot ive forces and can also be replaced by the rat io of . the corresponding ampere t u r n s ; ampere t u rns re quired to drive th rough the airgap \u03c7 an infinitesimal increase d \u0392 in flux density, divided by the ampere t u r n s per pole required to drive t h r o u g h the magnet ic circuit of the machine with the cor rect airgap the. same increase in flux dens i ty . ^Looking closer into the approximat ions which we int roduced in formula (3), we find: If \u03c7 is large a n d if t he magnet iza t ion characterist ic were a s t ra ight line (Fig. 5 ) , tjie sum B2 + \u0392\u03bb would actual ly be greater t h a n 2B. I n Fig. 5 the va lue ^ 1 is shown dot ted in. If, however, the characterist ic is strongly curved (Fig. 6), B2 + Bx will be slightly smaller t han 2 B. For ha rd pulling over, when \u03c7 reaches the greates t possible value, the sa tura t ion will in any case be high enough t h a t t he curva tu re of the character is t ic is marked . We are therefore certain tha t , on this score, formula (3) does no t give too low values for the extreme case. A very impor t an t question is, now: How does the expression of formula (3) change with growing excitation"
        ],
        "surrounding_texts": []
    },
    {
        "image_filename": "designv11_36_0002616_piae_proc_1916_011_012_02-Figure18-1.png",
        "original_path": "designv11-36/openalex_figure/designv11_36_0002616_piae_proc_1916_011_012_02-Figure18-1.png",
        "caption": "FIG. 18.",
        "texts": [
            " The worm wheel bearings shown in Fig. 17 are roller bearings of the cheese roller type without cage of any kind. These are in fact the bearings on which the balance gear box is WORM QEAR A N D W O R M OEAR MOUNTING. 105 mounted, and the worm wheel itself forms the central seotion of the balance gear box. The thrusts were of a specially designed type, and consisted of balls in a flat cage between two perfectly flat ground and hardened thrust washem, the balls being arranged in a spiral manner,* Fig. 18. The object of this arrangement, i.e., the spiral distribution of the balls, is that each ball ma3 bear on a different part of the flattened surface, so distributing the wear; a further advantage is, that if the balls vary amongst themselves aa to diameter, as is commonly the caae, each ball will form its own race and will soon be taking its due proportion od the 10ad-h markings on the thrust r a m frequently gave evi- denoe of this action. The degree of inaccuracy amongst balls of nominally the same diameter is cowonly less than one tenthouculndth of an inch"
        ],
        "surrounding_texts": []
    },
    {
        "image_filename": "designv11_36_0002713_t-aiee.1913.4765036-Figure1-1.png",
        "original_path": "designv11-36/openalex_figure/designv11_36_0002713_t-aiee.1913.4765036-Figure1-1.png",
        "caption": "FIG. 1",
        "texts": [
            " Tests were made on numerous grades of brushes, in vaxi- 559 560 ERBEN AND FREEMAN: [Feb. 27 ous types of brush holders, operating in both directions of rotation and through wide ranges of speed and pressure. The data thus obtained give the friction of brushes when carried in commercial brush holders. We are not yet prepared to give the full and complete results of these tests, as many of the results are now being verified. We show, however, on Curve 1 the coefficient of friction obtained at various speeds with one type of graphite brush operated at an angle of 37' deg. leading. Fig. 1 shows what is meant by various angles, leading and trailing. Test was also made to show the eifect of temperature on coeffi- cient of friction by enclosing a commutator in an asbestos-lined box, placing resistance grids under the commutator for a source of heat and piping a blower to the box to regulate and hold the temperature at various values. Tests were made at various speeds and at 40, 60, 75 and 100 deg. cent., and it was found that the change in input to motor over wide ranges in temperature was so slight as to be negligible in commercial applications",
            " We will later present similar curves showing coefficient of friction values with various types of brushes when operated at different angles. Application of Data on Brushes. Assuming the coefficient of friction as shown on curve to be applicable to the type of brush holder used, the friction should be calculated, as follows: P X SX VX FX 746w 33,000 When W = Watts loss, brush friction. P = Total applied pressure on brushes. V = Velocity, commutator or ring, in ft., per. min. F = Coefficient of friction. S = Sine of angle A (Fig. 1). For example, on a commutator 25 in. (63.5 cm.) in diameter running 2500 ft. (763 m.) per minute with 60 grade S brushes 2.30 0 U_ .20 U. 0 UJ.100 2000 2500 3000 3500 4000 4500 5000 FT. PER. MIN. CURVE 1.-COEFFICIENT OF FRICTION, GRADE S BRUSHES Angle 37' deg. leading. Approx. 2 lb. per brush applied pressure at an applied pressure of 2 lb. (0.907 kg.) per brush operating at 37' deg. angle. F = 0.05 (Curve 1). S = 0.783. 60 X 2 X 0.793 X 2500 X 0.05X76 = 270wattsW= ~~~33,000 Contact Resistance"
        ],
        "surrounding_texts": []
    },
    {
        "image_filename": "designv11_36_0002574_pime_proc_1861_012_010_02-Figure8-1.png",
        "original_path": "designv11-36/openalex_figure/designv11_36_0002574_pime_proc_1861_012_010_02-Figure8-1.png",
        "caption": "Fig. 8. Transverse S e h n .",
        "texts": [],
        "surrounding_texts": [
            "machine made any of the changes required in the winding or spoolchanging movements. Mr. WEILD said the only purpose of the notched wheel was to shift the driving belt from the outside pulley driving the winding apparhtus to the inside pulley driving the change movements, and back again alternately. The arrangement was commonly known as Roberts\u2019 contact pulley, originally used in the self-acting mule, for making intermittent movements with alternate intervals of rest. Mr. F. J. BRAMWELL observed that neither of the three driving pulleys was really R loose pulley, and since the middle one had the strap always on and was consequently always running, the driving power was always ready for shifting the belt at the instant when required; so that the continuous driving of the machine was kept up without intermission, though each portion of it stood still in turn. The SEURETARY had seen the self-acting winding machines at work a t Huddersfield, and could confirm the statements as to their satisfactory working : the great speed of winding, and the effective manner in which the winding was suddenly stopped dead when completed, were very striking; and also the steady and gradual action of the succeeding change movements in fastening off and cutting the thread and changing the spools, The working of the machine appeared very perfect and complete, and was stated by the proprietor to be thoroughly successful. Mr. WEILD remarked that one great difficulty that had been experienced a t first in getting the machine to work was to stop the winding a t the right moment when the spools were full. In winding by hand, the motion being controlled by the winder could be gradually retarded, so as to stop exactly a t the end of the last layer of thread ; but in the machine the great momentum of the winding parts revolving a t such a high speed rendered it impossible to stop a t the right point, until the powerful friction break was adopted, consisting of a strap passing round a friction pulley of large diameter. By this means the minding was stopped dead at the proper point, but without any shock, and the gearing and spools were all held quite stationary while the change movements were pcrformed. at UNIV NEBRASKA LIBRARIES on June 6, 2016pme.sagepub.comDownloaded from SPOOLING IIIACHINE. 71 The CHAIRMAN moved a vote of thanks to Mr. Weild, which was passed, for his very interesting paper, and the trouble he had taken in preparing the drawings and model by which its ingenious action was exhibited so completely. The following paper was then read :- at UNIV NEBRASKA LIBRARIES on June 6, 2016pme.sagepub.comDownloaded from S P O O L I N G MACHINE. S P O O L I N G MACHINE. at UNIV NEBRASKA LIBRARIES on June 6, 2016pme.sagepub.comDownloaded from Fig. 7. Thread F ~ & i y . n S P O O L I L G I CACHINE. at UNIV NEBRASKA LIBRARIES on June 6, 2016pme.sagepub.comDownloaded from S P O O L I N G M A C H I N E . Tmverse Motion, I I, at UNIV NEBRASKA LIBRARIES on June 6, 2016pme.sagepub.comDownloaded from S P O O L I NC M A C H I N E . PzUA 1.Q Diaqrams of Cams perfunrLizy CXu.np Movemp,aik I 0' 36'' 67. 90' 120' 150' a UO. 24Q' 270' 3OU' 330' 360' at UNIV NEBRASKA LIBRARIES on June 6, 2016pme.sagepub.comDownloaded from"
        ]
    },
    {
        "image_filename": "designv11_36_0002616_piae_proc_1916_011_012_02-Figure50-1.png",
        "original_path": "designv11-36/openalex_figure/designv11_36_0002616_piae_proc_1916_011_012_02-Figure50-1.png",
        "caption": "FIG. 50.",
        "texts": [
            " exists in the demonstration, a proof may be given that the velocity of approach and separation of the particles is in fact definitely the measure of the frictional rubbing or sliding velocity; it is a point which might, perhaps, otherwise be challenged. I n Fig. 49 the triangle of velocities is given for two particles C WORM GEAR AND WORM GEAR MOUNTING. 167 and D . Let these particles after a brief interval of time occupy positions c1 and dl respectively. Then the tangents of the contact faces must be parallel to the line cld,, for if they be otherwise than parallel the faces will either be in the act of interpenetrating as in Fig. 50 or in the act of emerging from interpenetration as in Fig. 51. As neither of these conditions is permissible, the tangent to the contact faces a t the point CD (where the two particles are momentarily in contact) is strictly parallel to the path of the separation of the particles, and therefore the velocity of the particles along their path of separation is necessarily and in fact the velocity with which the contact surfams are sliding one upon the other. I do not know what Mr. Bostoclc nieans when he says, \u201cNow it is generally supposed t"
        ],
        "surrounding_texts": []
    },
    {
        "image_filename": "designv11_36_0002547_piae_proc_1920_015_011_02-Figure3-1.png",
        "original_path": "designv11-36/openalex_figure/designv11_36_0002547_piae_proc_1920_015_011_02-Figure3-1.png",
        "caption": "FIG. 3.-Douglas 3$ h.p. Helical Spring Model.",
        "texts": [
            " along the middle rail, the w n h of the springs bieing hingeid by the s e a t pillar lug, and the ieax ends shackled on to a stay that went over the wheel. Unfortunately, the author did not test this machine himself; he has been told, though, that the early reports were good. The next experimental Douglas machines that came out were two 34 h.p. machiqes, one fitted with rear springing; the at PENNSYLVANIA STATE UNIV on June 5, 2016pau.sagepub.comDownloaded from machines oame down to the 3rd Heavy Repair Shop from up the line, where they had evidently had hard work. Helical springs were fitted as shown in Fig. 3, which is self-explanatory. The bracket on the middle rail anchoring the forward end of the springs was bToken, and this was repaired. !The author rather believes that a new middle rail was also put in., The spring cages skowwd that the movemlent had bean to the end of its travel fairly often and fairly hard., The machin,e was good and very comfortable to ride, but the springs were too stiff to be responsive to the light shocks. As far as the author mimembers, there was no appreciable wtear on the pins, or the main spindle, bearings",
            " The comparative merits of helical and leaf at PENNSYLVANIA STATE UNIV on June 5, 2016pau.sagepub.comDownloaded from THE S P K I N O I S G OF MOTOR CYCLES. 63 springs have been already discussed, and as the author has intimated, for this work he prefers the laminated leaf spring. Satisfactory designs have, however, been got out with helical springs for the rear springing, and there is no reason why they should not give very efficient results. The Douglas 33 h.p. machine, which is sprung at tbe rear with helical Springs and is a very original design, is shown in Fig. 3: the author is, however, unable to describe it fully as it is being experimented with further. The illustration is self-explanatory. The author has ridden one of these machines, which was sent over -to France for test purposes; it was very comfortable to ride and was well made, the only criticism is that the springs xvere of necessity rather stiff, the allowable movement of the wheel being small. Another well known machinre which has helical springs for the rear springing is the Matchless, Fig. 13, Plate I-it is to be regretted that on this type at present the ends of the springs are held solidly, and as the spring is compressed they move out of line, or rather, in the normal position they are out of line, and as the spring is further compressed they move into line, which comes to the same thing, as at one position they are being distorted"
        ],
        "surrounding_texts": []
    },
    {
        "image_filename": "designv11_36_0002530_piae_proc_1909_004_009_02-Figure10-1.png",
        "original_path": "designv11-36/openalex_figure/designv11_36_0002530_piae_proc_1909_004_009_02-Figure10-1.png",
        "caption": "FIG. 10.",
        "texts": [],
        "surrounding_texts": [
            "(MEMBER.) The subject of pneumatic springs for road vehicles is one to which I havo given a great deal of time and attention (luring the past nine or tcw years. I n developing an invmtion of this kind, whivh in its pracdicd apldication involves consitlerable cltanges in the design of ~taridarcl parts, the financial ciificulties are hy far the grcatebt. A firm with their works employed at their fullest capnrity and earning profits, naturally say that it is not business to disturb the works organization. On the other hand, when business is slack and profits arc small, or non-existent, there i s no money avui1J)Ie for cxprnsive expcririientq. Tn spite of these difficulties, tho technical success that has bern clearly demonstrated, even at an F w l y dago of niy esperiment8, has I )ew imdouhted, and cominrrcial surcess in tlie vwy near future i s , I hopo. almost assured Air spriiigs have ninny p ropd ies in common with steel springs, nnd it mill hc nocessnry to disr i iss springs in gwera l fairly fully, in orrlrr to bring out c l r ~ r l y the merits and tlwnarits of steel and air ILS tlie spring mcdiuiu. Springs foT IZoad Vchicks.-If a springless vehicle moves over an itnewn road, thr whole of the mass o\u20ac the vehicle! is subjected to a mries of irregular accelcrations i n a vertical direction. The force recyuireil t o produce the vertical acceleration is proportional to tb e mass partaking of the vertical acceleration and to the vertical iicceloration at the instant. The object of introducing springs in a road vehicle i r to i~ciliico tlie mass of that portion of the veliide SI-I 41t1J. G Pneumatic Springs for Road Vehicles. at UNIV OF VIRGINIA on June 9, 2016pau.sagepub.comDownloaded from whicli partakes of the verticd acvelemtion duo to the ii.~egularitics in tlic road burface. The prieutuattc tyro, in running over n small obstade on an otherwise smooth road, is ideal in this respect, since the mass partaking of the vertical acceleration is merely that of the small portion of the tyre in the neighbourhood of the obstacle. I n a less degree, this applies to tho solid rubber tyre. Rut the pneumatic tyre is of little value as a spring when the road ,surface is .fairly smooth, but wavy or lumpy. The adequate discussion of tliii Peature of the pneumatic tyre would rcquire a l'aper to itself, ancl want of apace prevents further discussion here. Generally speaking, the smaller thB mass between the springs and the point of contact with the ground, the more perfect will be the springing. This consideration has led to tho design of innumerable types o\u20ac spring wheel8 which 'I shall refer to late].. Leaving spring wheels aside \u20acor the moment, the less the mass of the wheel, axle and parts partaking of the vertical movement of the axle, the more advantageously is the springing applied. This at once suggests thc much-debated question of live a r k vorsus chain drive ; but wc engineers learn by every day experience that in designing siich a cvxnplox article as a motor car, the designer iTho places undue importance on any one element is lint likely to produce the most desirable result. It is far from my mind to express the opinion that the live axle is inferior to the chain drive, on account of the greater un-sprung mass, well knowing that the springing of tho vc~hicle is only one of the many factors to be considered by the designer. VwticnE Accr?wntion.-The sertical acceleration given to the un-sprung part of a vohiclc is a question of pure lrinernatics, ririd if thc speed of the vehicle nncl the shape of the irregularities of tho road surface are Irnown, the vwtical arcelemtion ran hc c~nlculnted. Without going ntin ittely into this aspect of the problem, it is desirable that sonic rough notion of the inagnitiide of the vc~tical accolerations should be linown. I.et us assume that a rigid wheel 30 inches iliamc+er is running on a level road, and sncldenly encounters a n obstavle 1 inch high ; let the sped of the vnhicle he 222 miles per hour, i e., 3Y feet per w w m d . Fig. 1 s h o w tho wheel as it first touches the ohstaide, tlltj point of contact of thrl ahecl with tho horizontal surface o P the groiind 1)eing then 5 ; inches, or say half a foot behind the obstacle. '!'be wntro of the whec.1 mows forward the diatance of half a foot THE INCORPORATED INSTIT~J'l?IO~ OF AUTOMOBILE ENOIWEERB. at UNIV OF VIRGINIA on June 9, 2016pau.sagepub.comDownloaded from in one sixty-sixth part of EL second, and ill the same time the mhcel is lifted verticdly 1 inch If it i b assunied that the acceleration is constant during this tinie, the calculation of the acceleration can be done by using tho well-known formula in elementary mechanics, s == i d 2 , where s is the vertical space moved through, a the vertical acceleration, and t the time. Substituting these values, we find that the acceleration is 726 ft./sec2, i .e . , 22 times the acceleration due to gravity alone. The force required to produce this acceleration, i .e. , the additional upward reaction on the wheel, over and above its own dead weight, is 22 times its weight. The centra of the whcrl h i n g vcrtically over the obstacle, i t is f i f ill moving vrrf~rally ijpwards wit11 a ccrtain vclocity T h e average vertical vclority chiring the upward acceleration is 66 inches per s~~coiid, and the final velocity a t tho end of the :tcceler,ztion, i .~., \\\\lion the wntrc of the whecl i4 vrrtically over the obstacle, is twice tliis amount, i . e . , 11 feet per second. The wheel will continue rising, being prillcd tlomn by gravity, and it will rise in the air a Eiirthcr distanrc of nearly 2 feet, aud will remain in the air nearly two-thirds of a second hefore reaching the horizontit1 road surface. If the lintJar speed of the vohic.10 be doubled, lhc vrrtiwd arcclrr:ition is four times as great ; if the linear speed of the wheel be trcblcd, giving a racing track spred of 67; miles per hour, the vertical arcelcration is nine times as great, i .e . , 198 times that due 0 2 at UNIV OF VIRGINIA on June 9, 2016pau.sagepub.comDownloaded from to gravity, while the wheel will remain in the air nearly two secondh. The possibility of the wheel remaining in the air for even n small friwtioii of a second without driving contact with the road, is of great iinportaiice as bearing on the durability of tyres. With the engine running a t 1,200 revolutions per minute, if a driving wheel leavcs contact with the ground for even a quarter of a second, in this poriod the engine makes five revolutions, and the energy of the explosions is expended in accelerating the driving mechanism including the driving wheel. Therefore when the tyre reaches the ground its linear speed is faster than that clue to the speed of the car, and it scrapes on the ground, wearing the tyre, aud possibly damaging the road surface. In a motor car the road wheel is pressed downwards by the spring, and is not in the air so long as in the simple case above diicussed. I n a car in which the back axle load is 1,800 lb., and the weight of the back wheels, axle, and all masses moving with the axle is, say, 200 lh., the downward ncceleratioii of the wheel, which begins a t the instant the centre of the wheel is verticdly o \\ e r ihe obstacle, is six times that due to gravity, i.e., equal to 192 feet per second per second. If tlie car is travelling at 22; miles per hoim, and the wheel mcountcrs an obstacle as in Pig. 1, the dimensions being as atated above, tlie wheel will rcmairi in the air about one-fifteenth part of H semiid. If with thr? m n e conditions, tho speed of tho car is dont)led, thc. tiiiie the wheel hangs in the air will he approximately do~hleil . Jf the weight of tlie 1111-sprung 111iLsS he smaller rclutively to the total wheel load, the time the wheel himgs in the air will bc rodwed. li'cailicncy (If' ~!'spl.in~s.--'l'o d i 4 p a spring for n road veliiclc the ilitta required are -the riornial load to he carried, tlie distance tho hpring may be conipressed beyoiid that clue to the normal load, and the correspoiiding maximum load on the spring when compressed to the maxiinum. For example, if tlic! spring may he compressed, say, 3 inches further than the amount due to the iiornial load, and if the corresponding instantaneous maximum load on tho spring be 5 0 per cwnt. greater than the normal load, then the spiing, if it is of ihc orciinary type in vhich the compression is proportional to the load btcadily applied, ail1 be coinpressed at nornial load to the extent of 6 inches, reckoned from the position of no load, while the maximuin compression will be 9 inches. THE INCORPORATED INSTIT~J'l?IO~ OF AUTOMOBILE ENOIWEERB. at UNIV OF VIRGINIA on June 9, 2016pau.sagepub.comDownloaded from The (\u2018 resilicnce \u201d of a spring is a term used with various meanings. Here I shall ii\u2018e it to mean the eiiergy stored iu the spring when subjrcted to its niaxuimum load. With this definition the resilience l? i.i equal to one-half the product of the niaxinirim load into the masiiiium deflection, which may he wrnpression or cxtension-that is, TZ==~We-wliere W is the mnxirnuni load and c the corresponding compression Tn ruotor car tleliigii the eliiiiinatiori of all uniieces\u2018ary weight is a most iinportaiit factor always to h e remembered by the designer. Probably the inost effective steel epring, so fa r as giving gretLte8t resiliency for thc least possible weight of material, is a very long wire or tie-rod subjected to tonsioii. It is shown in text -hooks of applied mechenios that the r e d i e n c ~ j of fiuch a tension rod is ? Y / 2 E , where IT is the volume of the tie-rod, f is the tensile stress produced by the load, and X is the modulus of elasticity of the inaterid. Combining the two formula? just written, we may write V=WeKp. The weight of the tierod is proportional to its volume. The above formula therefore shows that the weight of the spring must b~ proportional to the resiliertcy required--i.r., directly proportiond to the prodiict of the maxininni load W and the i i i ax i~ i iu~) deflection r , and invr rs~ly proportional to the square of t h o maximum s t r e s f\u2019 produced by the inaxiniuni load. A similar formula oan be used for a spring of any design, for helical or \u20acor 1amin:~tcd springs, but in these cases a larger numei-ical co-efficient is required, since each individual particle of iiietal i n the spring is not subjected to the maximum strcssf, but this maximum stress is limitcd to the material on the outsidc surfaces of thc. coils of the hclis, or of the leaves of the lnminated spring, as tlic case may be. Weiyht of Spinys.-Steol sibrings of whatever design or general armngemcnt, must have a rniniiiLum weight in order to (sivo a recluired niiiouirt of resiliency. and ho~c 1 he material of 1 lie s11riiigq is disposed is a inntter of soeondnry iinportancc A sl\u2019ririg irii~de from steel that can be safely subjcctcd t o a stress of 60 tons per square inch will give four times the resiliency of a spring inad0 from steel that can only bc safely suhjected to it stresh of X) toris per square inch. Hence tbe great practical importance of I iav ing steel springs made from the most suitable material. In i h i r springs, the weight of t h e resilinnl, inpdiuni, the compressed air, is pra(.ticidly nc~gligihlv. Tho weight of tlic air spring t lc~i~ i ids O L I tho diiiierisiuris of tho l)lunger and of tlie air qli i idw, which at UNIV OF VIRGINIA on June 9, 2016pau.sagepub.comDownloaded from riiitst, 01 courbc', kc dcsiglied to withstand the air pressure. A conipiiriqoii of tlie weiglit, of a steol spring aud an air spring for O(luil1 iobiliencaj will bc given by nie Inter on.\" LLerc it is sufficient to sax that an air sptiiig can be made having greater resiliency tlmn i5 pr.ic ticable for I L strel spring, and of niuch less weight. L [ J U ~ - ( o n i ~ i w s ~ ~ o n C'ururce.--The principal properties of a spring are c.xhibited by drawing its load-compression curve, in which the load may be set off along n Irorizontal axis, and the corresponding rotrrpressiou along a vertical axis. The work done in comprrssiug tho spriI,g is the11 represented l ~ p the area included betweeii the C I W V V , the vertical itxi&, aiid tlie horizontal ordinate corresponding t o the corn1)wssioii of the spring. I f the compression is proport ioi id to the load, the load-compression curve is a straight line l)a$sing through the origin. Let 0 P Q, Fig. 2 . be the load-compression curve of a spring between the road wheel and the chussis of the vehicle, in which the * See Author'& ielnalks, p. 111. THE INCORPORATED INSTIT~J'l?IO~ OF AUTOMOBILE ENOIWEERB. at UNIV OF VIRGINIA on June 9, 2016pau.sagepub.comDownloaded from normal load carried by thc spring is W, and tho compressiori of tlic spring uatler the load is I f . Then if the vehicle is irioviiig yriic~ltlg, and the road wheel has to mount it11 obstacl(. of height h , tho total cleforniation of the spring is 1% + h, and thP iri\\tantaiieous loatl OII the spring.is ( W + w), wherc tu is the upward additional forccb coiurnunic.,zted to the frerne CJf tho vrliicle and (xmiiig tho vertical acceleri~tion thoreof. Fiwni the geonietiy of the hgurc, I t is easily seen that 20 = Wh;tT. Therefoie if the cornproshion B of tho spring under the nornial load W be large, the upward accelerating force due to aii ohbtaclo of given height will be sirdl. In other words, the lesh the inclination of the load-defoni~ctt ion ciirvc to thv vertical axis 0 Y, the lolis is the verticd acceleration given to tho frame. Y \u2019 h \u2019 clt)it,od ( UI\u2019VP 0\u2019 1\u2019 (2\u2019 i5 i l iu I o r t d - c ~ o i ~ ~ ~ i r c ~ ~ ~ i o ~ i w i b t \u2019 f r J i (L stiffer spriiig flrau t h o sprirrg rrliIewntetl i)y 111u ( \u2018 I I ~ V U O I \u2019 11. 1 ) ) ,~prut!/s.--\\Vitlt t~ coi i ipo~sod-i~ir wpririg it ~b iiiiu h iuot c! oasy to obtaiii a load-cuiiipressio~i curve having a. sinall iiicliu:~tiiiii to tho vertical axis than is t ho caso witli u stcel ~y~riiig. 13\u2019ig. d i h intended to illustrate i n a purely tliagrariimatio foriii tho priiiLip1c.b involved in the application of BIL air &ping. to a. load vehicle. Tlic axle of the road wheel JV is :tttached by a rod or the equivaloiit t u a piston P which is free to move up and down in the cylinder C. The upper end of tlic cylinder C is iu conirnunicatioii u itli u reservoir It fixed to tho chassis, iuto which air call bo 1)uiiipud. at UNIV OF VIRGINIA on June 9, 2016pau.sagepub.comDownloaded from Tho under side of the piaton is exposed to atmospheric p)ressur(x, and the T ertical travel of the piston in the cylinder is of course liinited. If a load be p l a c ~ t l 011 the chassis while the pr~ssure of the air in the rwervoir is that of the ittmosphere, the chassis ill be in its lowest position relatively t u the road surface, the piston will press on the ui)l)er end oi tlieuylinder, and the load will be traiisuiittecltlirough tho solid c~ i ine~ t io i~s . The vehicle is then practically spriiigless. But if a i r he pimped iiito the ieservoir until the ail. pressure oii the piston is juat equal to the load on the chassis, them will bc no pressure bcjtueen the piston and the top end of the cyliiider. Ou p i n p i n g riioro air into the reservoir the cliassis will rise arid will he airsuppo i td . For exarriple, i f the. total whoc~l load is 1,000 lb., and the ,wen of the 1)iaton 10 square inches, a pressure of 1001h. per hqwre iiicli wi l l be required for blie ttir in tht. reservoir. If this pressure is exceeded tlie pistoll will be Islomi into coutdct h i th the l o w c ~ endof the cylinder, arid w l i c t i i thc>presiirie iii tlie reservoir is less, the pistoii wil[ t)o iri contact \\\\ ith tlie tol) eiid of (he c j lind(hr. Witli thct piston floating iibout midway in the iylirrder, if the road w h e l l i i~s to iiioiiiit :LII obstd(*le, the I\u2019istun i b forced iipwiirds iii tlii. ( yliiider, t l i ~ total voluirie of :Lir uiider picasuro is dightly 1-educed, arid the pressui (\u2019 per square inch is slightly increased. Ity niaking the volume of air enclosed in the reservoir large conipared with the volunie sncpt through by the yistoii iu rising a gil c\u2019n distance, tho ~ \u201d X C P ~ S force producing vertical .trceleration of the chassis can be reduced to a miiiiirium. \u2019l\u2019hua, if th9 strolrc of the piston in the cayliiider be four i d l e s , r t i i ~ l tho air 1)wssiiiu IS hud i t h a t riormally the pistonis in the middle uf its strokc iii tlici cylinder, tlie road wheel will be able to surmount a i l ubstu~le of slightly less thali two inches height, or will be able to tlrol) iiito :I l iu le iit the road sliglitly less than two iiiches in depth, M ithuut appreciably affec tiirg the supporting force oil the chassis. lu pd(ticC 1 fiiid it best to have the air pressure in the reservoir iiighfiy 111 ~ ~ ( e s b of that above demibed, 60 that norinally tho pi-hon IS pressing dightly against the bottom of the air cylinder. [Jiider these conditions the full stroke of the air spring is available for the road wheel iii inounting obstaclos, and there is no relative ~riovement of piston and cylinder wlirri the road surface is absolutely nii iooth. B u t n hen the road nlioel dips into a hollow, tho whole vc~liic~le drol\u2019s, :md when thc road wheel is rising out of the hollow, tlko piston first riscs in tlw ail c-yliridor, and the cahnssis is therl gcintly liftod b j tlic excess air ]t)r\u2019ussure. THE INCORPORATED INSTIT~J'l?IO~ OF AUTOMOBILE ENOIWEERB. at UNIV OF VIRGINIA on June 9, 2016pau.sagepub.comDownloaded from PNEIlMATIC SPRINGS FOR ROAD VEHICLES. 95 Any combination of a cylinder, piston and piston rod, may be u x e d for air air spring ; the ordinary tyre pump is a good example of such an air spring. But with the usual types of pistons and plungers that arc inet with i n engines and pumps, no matter how perfect the piston packing may be, there is a slight leakage. The obvious solirtion is to have ail air pump driven by the engine which continually pumps air to replenish that lost by the leakage from the compressed air reservoir. Tho replenishment F I G . 4. may be controlled by a valve which can be opwatecl eitbcr by the driver, or automatically. This is the mothod adopted in the Cowey system of air springing which was exhibitetl at Olyinpia in Noveintier, 1909. I n the system of air spriiiging which 1 have invcwted, I cmploy a rolling packing mitten which permits of the piston or plunger being a11 easy, practical fit in tho air cylinder, and at the sarric time provides uu absolutely air-tight joint. at UNIV OF VIRGINIA on June 9, 2016pau.sagepub.comDownloaded from 96 'I'H F, INCOILYORA'I'EI) INS'fr'TU'rION OF AUlOMORlLE ENGINEERS. Pig. 4 is a half-sectional view of an air spring adapted to form tlie saddle pillar of a bicycle. The air cylinder and the plunger are each niadc in two parts suitably screwed together; in screwing them together provision ib made for fastening the ends of the mittcn to the cylinder and plunger respectively by air-tight joints. The pztrts aro all inado of stampings from sheet steel. The lower part of tho air cylinder 2 is closed at the lowor cnd, while its upper cnd is provided with a flange for the rcception and fastening of the larger end of the rolling packing mitten. The lower part 5 of thc plunger is an easy sliding fit iiiside the lower part 7 of the cylinder Tho lipper part 2ZA of the plunger is closed at the upper end, which is reduced to seven-eighths of an inch ill diameter, to form an extcrnal pin to which the saddle clip can be clamped iu the usual way. Tho sniallcr end of the mitten is pressed between a conical surface on the upper part of the plunger and a retaining ring 6 , when the two parts of the plunger arc screwed together. Siniilarly, tlie larger end of the mitten is pressed between an inside conical surface on the cap /iA and the end 01 the air cylinder I , when the screw ring 3' is screwed up tight on the cap. The plunger is guided mechanically by the neck of the cap ,$A and by the air cylinder 1. To prevent the saddle twisting relatively to the cylinder, the outer surface of the plunger 2A is provided with a number of fine rriooth longitudinal grooves, which fit in corresponding grooves through which the compressed air is forced by an ordinary cycle pump, is fastened to the lower end of a central bolt, which is provided at its upper end with a stop washer 35 against which the rubber washer 30' rests. When air is pumped into the saddle pillar, the plunger is forced upwards until the in-turned flange of tho lower part 5 comes in contact with the rubber washer ,?6. The cornplete saddle pillar is fastened by a clip 68 encircling the neck of the cap $ A , and jointed to the end of a tubular post 6'; ~vhicli s clamped in the usual way in the down tube of' the bicyclr. The lower end of the cylinder is attached to thc back stays of the bicj d e by moans of universal clips 62, G6 ; the distancse apart of clips 66 can be varied by a screxwed distance piece to fit the hack stays of the bicycle. Big. 5 , Plate XVII., shows the parts separated ready for thc removal of an old mitten and the insortion of a new one. This is effected by unscrewing tho ring 3 from the cap &4, when the latter can be removed from the plunger. Tho two parts of tho on t t e inner surface of the neck of the cap 4 A . The valve 51, at UNIV OF VIRGINIA on June 9, 2016pau.sagepub.comDownloaded from plunger RA and 6 are then unscrewed, when the retaining ring and tlie mitten can be removed. Pig. 6, Plate XVII., shows a bicycle fitted with th r saddle pillar, and with air spring front forks. The air spring of the front fork is the same as that sliown in Fig. 4, with the exreption that there are no grooves on tlw plrrnger and cap; the bottom of the cylinder is fixed to the crowii to which the fork-sidcx are brazed, while the small pin at the top of the plungw is tljspensed Kith, a n d a pin joint fastrning, which cwrics the valvc, is provided for attachment to the end of a short brackct projecting from the head clip. Fig. 7 , Plate XVIlI. , illustrates a bicycle in which both wheels are mounted on air spring forks, the chain stays being attached to the frame by a joint concentric with tho crank axle. Pig. 8, Plate XVIII., illustrates a motor bicycle in which both wheels are mounted on air spring forks. i n the latter case the back wheel spindle is fixcd brtveen two triangular swing plates ; these arc jointed to the ends of the rigid frarnc, to which also the onds of the air spring forks arc jointed. The arrangement of the rigid forks, air spring front forks and swing p1atc.s provides for practically absolute 1:ttrral rigidity, whilc it allows perfect freedom of vertical movement of the wheels relatively to the framo while passing over a rough road. The inside dianieter oE tho cylinder I of the air spring, Figs. 4, 5, 6 and 8, is 2 inches; the outsidr diametor of the cap 4A is 14 iuches. The supporting area, measured to the middle of the bend of the mitten, is about 3 square inches. The stroke of the plunger relativeiy to the cylinder is 2 inches. By the arrangement of the joints in the swing plates on the lower ends of the forke, it will be seen that the vertical inovenient of the wheel relatively to the frame is greater than the strokc of the plunger in the c3yhdeJ- of tho air spring, and amounts to about 2: inches in Wig. 6. I i o l l i y Packing .M~tt~n.--The rolling packing mitten is built up of two laycrs of parallel tlireads arrdiiged close togcther side by sidr, the lnyers crossing each other a t a sniall angle, from loo to 15\u2019 with the axis of tho niittcn ; thus, a thread of one lager CJ ossrs tlit tiircads of the other layer at an anglc of from 20\u00b0 to 30\u00b0. A layer oi indiarubber is vulcariised to the fabric on the inside surface of thc niitten, and this layer of rubber is relied upon for making the mitten impervious to air. Another layer of rubber is vulcaniscd on the outside of the mitten with the object of preserving the fabric as it rolls from tho plungcr to tho cylinder or vice i m s 8 . This construction at UNIV OF VIRGINIA on June 9, 2016pau.sagepub.comDownloaded from !I 8 'I'H 14; 1 NCO R PO R A'lXI) IN STPTCTI ON OF AUTO &I 0 HILB ENGIK EERS. re11 d ~ r s the mitten practically inextensible longitudinally, so that it is able to support the air pressure where it bridgos over the small distance hctwmu the surfaces of tho plunger and air cylinder. I t also ronders tlie mitten elastic r.idially or circumfereutially, so that it ciiii instantly adapt itself to the diffcrent diaineters of the plunger anil air cylinder as it rolls from the one on to tlie other. The in5ide lnycr of rubber on which Elir-tightness depends is contiii uoucly *upporfed I J ~ tlie fdlric. 15 the earliest experiments the mitten was made with a single layer of lougitndinal threads irribctldod in rubber, but it was found that tho circumferential stretching and shortening which takes place continuously during the action of the spring was concentrated locally at the thinnest part of the rubber, and a puncture very soon occurred. The two edges of thc mitten are thickened so that they can be fastened respectively to the plunger and to the air cylinder, malting air-tight joints with both. Uurcibility of tJir. Mitten -The stress 011 the fabric of the mitten cwisists of tno components. The first is the tension due to the air pwssure in tlie spring ; even with comparatively great pressures tliis stress is relatively small. For example, allowing three-eighths oU an incili between the two surfaces of the 1J section of the mitten iii position i n the spring, each inch length of section of the niitteii lias to support tho air pressure on tliree-sixteenths of a square inch. With an air pressure of 100 Ib. per square inch this amounts to less than 20 lb. per linear inch of scction of the mitten. The second stress on the fabric of the mitten is that due to the continual bending and straightening. If an individual thread is subjected to no stress when straight, i.e., when lying on the surface of the plunger or air cylinder, it is bent into a circular arc when it reaches the pait forming the bridge between the plunger and iLir cylinder, and its inner part is compressed and its outer part vxtended. Superposing on thrsc stresses the tension due to the iiir pressure, tlic inner fabric of the thread is subjected to a tensile <tress, and the outer fabric to a greater tensile stress. Tlierefore the durability of the mittrn, or its length OP life, is dependent 011 thr. number of strokes tho plunger makes ielatively to tho air chylinder, and also to the air pressure inside the air cylinder. This is borne out by actual experience. I t should be noted that the inner layer of rubber of the mitten is always in (*ontact with the sanie air coilfined irisido the spring. I kind that tlie rubbor part of tho iiiitten docs not perish however at UNIV OF VIRGINIA on June 9, 2016pau.sagepub.comDownloaded from P N E U M A T I C SPRINGS FOR ROAD Vb>HlCI,E*. 99 long it may be kept a t rest inside the air spring. When the mitten actually fails it is by the disintegration of a part of the fabric ; at the point of failure the rubber is not supported, a ininute burst of the rubber layer occurs, and the air gradually leaks. The first air spring made had an external diameter of 18 inches, the mitten had not much space to turn on itself, and its life was short. The diameter of the air spring was gradually increased until the largest diameter of the air cylinder on which the mitten rolls is Z& inches in the air spring now placed on the market by Air Springs, Ltd., of Stafford, for pedicycles and motor bicycles. Testing this mitten in the works under a total load of 180 Ib., it is found that over three million double strokes are required to produce failure. The experiments with gradually increasing sizes of mittens show that the durability becomes greater the larger the air spring. For a motor car of medium weight, the diameter of the air spring cylinder will be $4 inches, and the thiclmesa of the mitten will be the same as in those at present used for bicycles. The space allowed betmean the plunger and the air cylinder for the mitten to turn on itself will be about the same as at present. The supporting area of this air spring will be s1ight)ly over 7 square inches, and the ratio of the dinmetera of the plunger and air cylinders being nparer to unity than is the case with smaller mittens, the durability of the mitten may he expected l o be much greater than that stated above. 11 question that is oftcn put is, naturally, how long does the iiiitteri last, or what mileage will it r u n 011 :L bicycla or motor bicaycale ? The conversion into milengc? of the three million doublc strokes nientioned ribove w s required to destroy the itlitten cannot br dolie offhand, as the nunibur of strokes the plunger makes in the cylinder of the air spring depeiicls on the roughness of the road, and on tho pressurc to which the air spring is pumped, This much, however, can be said, under the comparatively liglit load on a pedicycle, a i d the slow speed of travelling, we have not yet worn out a mitten by actually travelling on the road. On the front fork of the motor bicycle, the life of the mitten is from 2,000 miles to 5,000 miles, while on a back air spring fork of a heavy motor bicycle it is appreciably less, a thousand miles being about the average. A larger air spring 3 inches in external diameter is recommended for the back air spring of a heavy motor bicycle, and, for the sake of uniformity of at UNIV OF VIRGINIA on June 9, 2016pau.sagepub.comDownloaded from 1'attePn, tho front air spring should be of thc! saiiie diameter, 60 .that the same mitten will fit cithcr front or back air spring. Air Springs f i r Motor Cars.-In this division of the subject I should have praferrcd to say nothing at this stago, since the c\\periiiicwts ah-eady mndo hitvc not I)ccn on stanilarcl cais. 'It will he sufficient to say that mc have had R sinall CBP wc.ighing about 7 or 8 c w t , made hy Afessrs. James & Urowne, Limited, fitted with four small air springs of the same diameter as those used on THE INCORPORATED INSTIT~J'l?IO~ OF AUTOMOBILE ENOIWEERB. at UNIV OF VIRGINIA on June 9, 2016pau.sagepub.comDownloaded from motor bicycles. Tho experiments made in running this car over rough roads, when compared with those made on pedicycles and motor bicycles, clearly show that the heavier the voliicle the more luxurious is the comfort obtainedd by the use of air springs, but the air spriugs on this car were clearly too small, from the point of view oi durability of the mitten. Fig. \u20183 is a half-sectional view of a11 air spring suitable for a niotor car. This design is somewhat differont from that shown in Fig. 4, in that the central retaining bolt is dispensed with, and the large elid of the mitten is held in a tubular holder If, the end of which is adapted to squeeze a rubher ring R against the end of the cylinder, making an air-tight joint therewith, when the screw-cap C is screwed up. The end of the mitten-holder also forms a stop, limiting the outward stroke of the plunger. With thiR design, upon unscrewing the rap (\u2018 the plunger, mitten, and mitten-holder can be withdrawn from the oylinder, and the mitten is then easily accessible. Joint pieces are fastened to the ends of the cylinder and of the plunger, to connect the air spring to the chassis, road Rheel axle, or axlr rasing, respectively, the valve being inserted in one of the joint pirces. The diameter of the air cylinder is 3; inchos; the diameter of the plunger 2 ; inchefi ; the stroke 3 inches j the supporting area for calculation, 7 squarc inches ; tho volume of air enclosed when the plunger is fully oxtended is 87 cubic inches ; the volume of air displaced by a full stroke of plunger, 21 cubic inches. The partn are 0.05 inch thick, and the air spring can resist a proof test to an air pressure of 500 lb. per square inch. The air spring being adapted to resist rncrely an axial load, when used in a motor car 1:itcral constraint must bc provided between the wheel axle of the chassis, in addiliori to the longitudinal constraint. This involves a re-dosign of certain parts of tho chassis. Pig. 10 shows one suitable sketch design of a live axle. I t is to be remembered that air springs cannot resist the torque, so that torque rods are absolutely necessary. The live axlo casing, torque rods t and the two diagonal rods d form a rigid pyramidal structure having its vertex at Y secured to the chassis by a universal joint. The two side radius rods r complete the necessary constraint of the live axle, and ensure that it will always remain approximately at right angles to the longitudinal axis of the car. The diagonals cl in combination with the radius rods r ensure that the road wheels cannot move laterally relatively to the chassis, at UNIV OF VIRGINIA on June 9, 2016pau.sagepub.comDownloaded from 102 T H E IXCORPORA\u2019I l b l f TNSTlTU\u2018rION OF AC\u2019TOLIOHII,E ENGINEERS. while the two road wheels are free to niove vertically, oither separately or simultaneously under the control of the air spring. The design of the front axle can be provided for with equal facility Load- Compression Curve of the Air Sprifig.-Pig. 11 shows a typical load-compression curve for an air spring. RR is set of? vertically, equal to the stroke of the plunger in the air cylinder. The point 0 is niarked in the saiiie vcrtical line, so that the ratio AO/AB is equal to the ratio of the total volume of contained air to the volunie displaced by the full stroke of the plungcr. Then, drawing a horizontal axis, O H , to represent tho axis of load, the load-compression curve for the spring will be an adiabatic, having tho asyniptotes OA and OH. Tho curve in Fig. 11 is drawn for a spring in which the volume displaced by the full stroke of the plunger is one--fourth the total volume, xhich corresponds nearly to tho spring illustrated in Pig. 9. If the air is pumped to such a at UNIV OF VIRGINIA on June 9, 2016pau.sagepub.comDownloaded from pressure that under the riorinal load the plunger i i forc Aed outwads till it just touchefi the stop, tho point C on the curve will correspond to the normal load. If the air pressure be slightly less, tho normal load may corre\\pond to the point U in the curve j while if the air is pumped to a higher prrssure than that qietitiecl above, the normal load will he represented by the point 13. With the air pressure such that the point U represmts the norrnal lciad, the Rpring will be adjiistcd to give the groittcst (mnfoit, sill( e 1 wo-thirds of the strolro of the spring n ill be aveilahle for sulmouriting obstacales arid one-third will be ava1l:ible w h m tho road wl~ec~l dips iiito hollows, without commminicatirig much vertical acceleration to the chatssis. R E C Fro. 11. The air pressure should always bo such that the l'lunger never strikes the hottom of the air cylinder. Tf this is attended to there is absolute certainty that the stresses on th(. c%assi?, in travelling over the iqoughest road, will never exceed those due to the load BF. If the sir pressure in the spring is such that the normal load is represented by the point E, then when the road wheels surmount an ohstacle equal in height to thc stroke of the plunger, thevariable force causing the upward acceleration of the chassis is represented by the horizontal ordinates between the vertical EG and the curve CP. This average force is greater than that corresponding to th(A air pressure for which the point C represents the iiormd load, and SHARP H at UNIV OF VIRGINIA on June 9, 2016pau.sagepub.comDownloaded from still greater than that for which tlie point I) represents t h nornial I'i.r&aZ ~rnnlpzclsa conznmriica~ed to the (~hns~is.-Iffbe the average Eorco producing vertical acceleration of the chassis while tho road whcel i< surnioiintiiig an obstacle, and t be the time during uhich it acts, i .~ . , tho time taken by the road wheel to pass on to the obstarle, then the vertical momentum given to tlie c1msbiC: is ft =I!Lo/g, whwe M i s the mass of the chassis and v the vertical velocity c-ominunit :Ltc(l. Broic tliis wc obtain u==yff /W. Tlie grmter tho lincur speed of the CILI' the shorter will be tlto tiiiie t , and the smaller tlie valne of .f the less will be the vertical velocity v communicated I o the c8h:Lssis. Comparing the load-roinpression rurve of an air qtiiing l+g. 11, and of n steal spring, Pig. 2, it will he sem t h t t I i o Forcc f procIucing tlie verbical wcelcration is relativnly smallrr in thr. case of the air spring. The value o f f can be rcducetl to as littlr as rnay h e desired in practice hy simply increasing the total volunie of air confined in the air spring, while keeping the volunie of air displnced by the plunger constant. FIowevcr, the air spring shown in Fig. !-f probably gives as romfortable riding as can be desired. Period 9 1 Osrilhtion of n ~ ~ r i l z ~ 7 - s ~ ~ p p o r t e d ~ ~ i s . s . - - I f a heavy ninss is suspended b y a spring, it has a certain position of equilibrinm. If ilkturbed from this position, it will continue oscillating until tho energy of the initial disturbance has been expended in frictional resistanre. If the load compression eiirw of the spring is n straight linc, the time of oscillation is given by the formida, T = 27 /\" where T is the lime in seconds reqnirecl for the conipleto up and down oscillation, W is tho wciglzt in pounds supported, and B the force in pounds requircd to produce ono foot extension or compression oP the spriiig. The period of oscillation T is independent of the ainplitude of the oscillation, arid affords a ready means o l r i d r i n g R quick estimate of the efficiency of the springing of a car. The relative value of the springing dzould I)? reckoned as proport ioiial lo tho square of the pmiotl of osrillntion. Thus by Btancling on the toot board nnd communic&ng a sei-ici of impulses to the c*hassi~ w l u l t ~ the vur is a1 rest, tlie chassis is 5et osrillating np antl down. A very quick period of oscilintion indirates that thc spriuging is tl&c%ive. A long period of osdlation indicxntes i1ior(i cffic+.nt s1)riiigirig. This test applied to tlie bicyc lc antl motor Iiicyc.le load. 14'9' THE INCORPORATED INSTIT~J'l?IO~ OF AUTOMOBILE ENOIWEERB. at UNIV OF VIRGINIA on June 9, 2016pau.sagepub.comDownloaded from shown, gives nn indication of the luxury of riding tlicni over rough roads. ~'j'hock Absorbsrs.-It may be asked whether the air spying hexing so rosilicnt does not require a shock absorber, or whcttier thc air spring resembles a shock absorber. 'l'he nature of the action oC a shock nbsorbcr c an be reprcsentml 0 1 % the load-rolupression diagram of the ipriiig In Pig. 12, O T Y L is the l,,ad-corripression ciwvc of tho spring, thcl p i t i t P correspondl; to the norinal load. Whilc the wheel is i u r n ~ o r i r i t i r i g an obstacle, the spring is being fintlrier compressed, and the fi ir t ionxl resistunw of thc shock absorhci adds to the upward reaction coiiiniiinicated l o the d u i 4 s , i t s iiidicated by tho line AB. \\Vlic.ri the wheel is I moving domiwards n,way from the chassis, i . ~ . , when running donm tlic fa r side of n,n ohsteole or running down the ne:ircT side of :I holIo\\r, t ho upward reaction on tho chassis and t,hc dowvnn.:i.rtl push o f t I i ( 1 spring on the axle is lessened, a s indicatod h y tlic: liiio CJ) . The ~ l i 0 ~ 1 x absorber, therofore, :Ilthough it ni:iy l ~ c viv-y efftv;tive i n (1aiiil)irig oiit tlie vertical oscilla.tion of the spriiig after passing 0 ~ ~ 1 - :in o h t u d e , nlso practically stiffens the spi,itig wl i i l o i t is twi i ig couipr(?sscd, and wealiens i t whilc boing extcucletl. Froin i i S T I I ( ! ~ of Fig. 12, I: should expect, other things h i n g cv~u:tl, th:it u c:ir fitted wi th shorlr a'risorbei s would have its road wheels 11:uiging longer iii the air aftor passiug over an obstaclc than n siniil:Lr car without ehoc.l< uhsorbcrs. I should therefore expect tho car wit!i the shock ahorhe r to he inore severe on t h e f;yres, then :L h i r n i l i t r T I 2 at UNIV OF VIRGINIA on June 9, 2016pau.sagepub.comDownloaded from car tvithoat shock a1)sorlms. liut on this point 1 hnvc. no a r tud r e b i i l t , (Jf oxlterience to communiratc, 1101' do I renic\\inlocr that this point has heen discussed a nyahere. Ail S p i n y s j i r Awopiunm-No apology is needed for disrussing aeroplanes in a paper on road vehicles, sirice the greater nnmboi- of acrcrpianes at present in existence have nwor left terrtr j 1 . 1 7 ~ ~ ~ ; B hilo of those aeiopltlpes that liave adiially flow 11, thc mtio bctwecii thc ~ i i i i o slieiit iii tlie air to thc tirue spent 011 tlit: groiintl ii p r o h b l y soiiiothing like oiie minute to one month ; :it all events, tlie ,idaptation of air springs f,o acroplaues has alrcady been inve-,tigated. Tho aeroplane air spring should combine in a T ri--y simple manner the resilience required for running ovor :L rough surface for the starting run preliminary to flight, and, at t h e sanie time, should provide for absorbing the ,shock due to a too sudden descent. An air spring for an aeroplane with a worl,ing stroke of, say, 12 i n c h , can be made on the linos of Fig I), retaining the same diarnetors of plunger and air cylindw, Init increasing the length. I%y fitting II plate mross tho inner end of tlie plunger, so as to reduce the volume of air enclosed in the air \\ p i n g whrn the plimger is at the eiid of its innel strolrci relatively to the air cylinder, the ratio betweon tlie volumes of air cndosed wi th tho plunger at the t x o extremes of its stroke can be inereasod. I n other words, the air pressure when the plunger is a t the end of its innrr stroke may be made three, foul', or five timcs as grcat AS the normal load. Thus, referriug to Pig. 11, tho part, AB, may (VITPspond to a stroke of four inches, to bc utilized for the stnrtiiig run, the small inclination of the curve, CF, rhowing that very little slioc~k is coiiirnunicated to the chaqbis. The distanc e, AK, w o d d then correspond to the fnll iiiwnrd 12 iiiches stroke of the plringer, the correspoiiding load on the si riiig bring then, K , I<, fou r tiines as great a$ tho total woight of the acroplano, AC. The energy which the air spring is capable of absoybing is indicated by the t~rerl, CK,I<, inc>Iided between tlitr curve and the two straight lines. DoublP Telpscopic Azs Springs.-l?ig. 14 is a half sectional view showing a double telescopic air spring, the contained air being in froe communication bctwern all tho parks. The cent1 a1 tiilie forms th(k cylinder for tlie inner plunger, and d h o f o r m the plunger for thfl outer c~yliiider. The details of thc parts show slight niodifications as corqared with Pig. 10, hut, without cleucribing them in dotail, they can he followed from tho drawing. There are two mittens used. The relative stroke of the inner plunger is ;; inclics ; THE INCORPORATED INSTIT~J'l?IO~ OF AUTOMOBILE ENOIWEERB. at UNIV OF VIRGINIA on June 9, 2016pau.sagepub.comDownloaded from PNEUMATIC SPRIXGS FOR ROAL) VEHICLES. 107 the stroke of tho central plunger relatively to the outer cylinder is 2Q inches, thus giving ti total stroke of 59 inches. The drdwiug 8 1 ~ 0 ~ s the air spring fully co~upresseed. If this air spring is used UII H, raid vuhicIc the air sliould be pumped to such tt Immure that I F I G . 14. when supporting the normal load the middle plunger is b l o w n out to its fullest extension relatively to the outer air cylinder, while the inner plunger is just ready to begin its outward stroke relatively to the central plunger. The load-compression c*urve for this spring (Fig. 15, analogous to Fig. 11) would sliow a curved portion CF, at UNIV OF VIRGINIA on June 9, 2016pau.sagepub.comDownloaded from at a very slight incliriatiou to the vertex a i i s OA, the vcrtical distalice A13 cwrespondiiig to the 3-inoh stroke of tlie inner plimgcr. Yroni the point l! on the load-oxteiisioii curvc there ~ o i t l c l bc i~ mtide~i chaiige to 2% Iiori;..onlal line PY, , the ratio UF, to lib' Iwirrg cqual to the ratio betwceii the supporiiiig areas of the outer aud i~ iuer air springs. From B, tlic load-conilwcisioni curvo theu follon 8 another adiabatic, tho working hoight BK, being 2: inches and corresponding to the stroke s f the outer air spring. The point on the load-exteiision curve corresponding to the nornial load shoiiltl lie on the straight 1cu-t PP, , iicnr to tlie p i n t 3'. \\Vith this air spring SO adjusted, when tho wheel surmounts an obstacle, the outer air spriiig wurild be com1)resd., a d when the wheel di1)s into a l~ol!ow the inner air spring n ould extend. THE INCORPORATED INSTIT~J'l?IO~ OF AUTOMOBILE ENOIWEERB. at UNIV OF VIRGINIA on June 9, 2016pau.sagepub.comDownloaded from ADVANTAG ~8 ASU DISA~)VANTAGES 01.7 h a SPRINGS. C'omfort.-The great comfort to the passengcr obtainable by the me of air springs has already becn sufficiently discussod, and n o d not he further eriforced hem. ifcllustnbzlit~.--Tlle springs are instantly itdjustable by a frw strokes of the purnp to suit the load to be carried. A steel spring ruay give corufortablc riding when tlie car is,fully loaded, and bc very iniperfect when the ctir is trttvelliiig with a light load. L(y/itness.-Witlr the springs suitably adjusted, there is absolute jnsitranev against the frame being subjected to force9 of unknown iiiagriitude in travelliiig over rougli roads, in fact thc stresoes on tlie cEiaFhis :Lrc rendered quit0 determinate, and the vehicle may, Ilierefore, b~ m:tdt. lighter than hitherto 1)oshible. h i this connection I iiiay my that oiie of the first iiiotor bicycles fitted with air spriiigs carried a twin cylinder Clenient eiigine 68mrn. x 7Smm. ; the stceringhead of tlie bicycle was that of an ordinary roadster bicycle, a i d proved quite struiig eltough for all roquiremcnts. Of course, if it liad befn ridden with the front air spring deflated the results would huvc beeii disastrous. I may also add, that in the niotor bicycles now exhibited no attempt lias beeii made to lighten any of the llarts, beariiig in mind that the iriachines may pass into the hands of riders who may somotinies use them with tho air springs deflated. /2elia6ility.--Thero are no parts to break, air preserving its elasticity for cvor; the only perishable part is the mitten, which can be quickly renewed. A complete air spring can be carried on tho car, the attachment of the air spring between the chassis and whwl axle being effectotl very easily. /<;fJL'rt on [I'yres.--Froni the fact that the air spring has a rriucli flattor load-compression curve than a stcul spring, the downsard forccx e x d e d in keeping tho tyre on the ground after it has suriiiountocl a n obstacle is greatw tliaii with steel spring5, ant1 therefort. therc irj lesh wear and lettr on the tyres. In this coiiiiectivn the air spring niotor bicycles have sltown greiLt durability under this head. To iealiso to the ful l t h o increased endurance of tho tyre, thcl wherls and lnr t s parthking of the vertical movemeiits of tho whoels should be made as light as possible The tgres can be lllade smaller than heretofore, and the initial outlay and running cost w i l l be reduced. I n this connection, the endurance of the 2% inch who& in tho air spring iiiotor bicyclc lias been shown to at UNIV OF VIRGINIA on June 9, 2016pau.sagepub.comDownloaded from be gwater than that of 26 inch wheels on a rigid-franie bicycle. However, as the owner of the vehicle probably will not care to have the wheels and tyres smaller than a standard size, the smallest standard size tyro sliould be used. If the diameter of the tyres is reduced, the cross section should be increased to give equal load carrying capacity. The load carrying capacity may be approximately estimated by rriultiplying the diameter by the cross section. Thtis, a tyre 25 inches by 4 inches would have a load carrying capacity approximately equal to that of n tyre 30 inches by 3E inches. 7 ' 1 1 ~ wheel diameter8 being reduced, the toque oil the differential axle is reduced and thc torque from the brakes is reduced ; the complete live axle can therefore be made lighter, thus further reducing the un-sprung mass. Grrnter Speed.-The driving wheels being kept in closer driving mitact with the ground, less engine powel* is wasted i n accelerating the whct?ls in the air. In other words, greater speed should be attained for tho same engine power. The g r e h r the engine power, the greater, probably, is the extra speed to be obtained. D~sndvantages.-The only disadvantage is one inlierent to the attainment of gre:Lter perfection, i e., the emall amount of trouble required to adjust the air spring for the conditions. On a motor bus, for example, where the wheel load varies considerably from vehicle empty to vehicle fully loaded, some mechanical means, probably automatic, may be necessary to keep the air springs inflated to a pressure corresponding to the load at the inetant. On a touring car, however, a few strokes of the pump, or a little air let out of the air spring, will be all that is necessary in the way of wl justrnent. THE INCORPORATED INSTIT~J'l?IO~ OF AUTOMOBILE ENOIWEERB. at UNIV OF VIRGINIA on June 9, 2016pau.sagepub.comDownloaded from 111 THE UISUUSSlON At tho conclusion of the paper I\u2019rofessor SHABP said: I had intended t o hava prepared an appendix on the coiriparntivo weight of steel springs and air springs, but that is noi iiecassayy; it will suffice i f I give a digest of the result. Profossor Low, in hix \u2018\u2018 Pocket-Book for Mechanical Engineers,\u201d gives a formula for locomotive laminated she1 springs, and from this I\u2019oriiiuh, which I think wc can rely on, bearing in inind I\u2019rofessor Low\u2019s earc in writing anything to which he gives his name, I find that the weight of laminated loconiotive springs conies out at 25 lb. lo r each inch-ton of resilience provided. Now, this actual air Ispring that I have here can be used to support a quarter of ti ton; if i t is loaded to a quarter of a ton its yield is 2 in . ; its weight is 2 Ib., so that this small spring is capable of a much greater resilience than a locomotive steel spring. I t shows 4 lb. weight per inch-ton resilience, and therefore there is ail ttdvantagc of 6$ to 1 in favour of the air spring. 1 think that o n tho larger sizes such as would be suitable for motor ears, the advantage possibly may be still greater. The President (Ur. 11. S. HELE-SHAW): I would like to say in proposing a vote of thanks to Professor Sharp that wo have had to-night the benefit of his close and continuous study of i h o hubject for over ten years. I would recall to your minds f lie beginning of tho practical development of the piieurnatic i,yre, and especially 1 would like to recall the labours of Michelin, who produced a classical research on the subject. He treated graphically, for the first time, the effect of riding over obdacles upon a pneumatic tyre, and carried a pointer to indicate that effect. Ile also rode bicycles with solid rubber and with iron tyres, and he showed curves illustrating the difference in the efrect produced by the different kinds of tyre in riding over obstacles. The curves showed that the bicycle jumped up inany times higher when ridden over an obstacle with iron tyres than it did when ridden over the same obstacle with pneumatic tyres, and for the same reason that we have had so lucidly given to 11s to-night by ProfesEior Sharp. I have tried the effect of riding at UNIV OF VIRGINIA on June 9, 2016pau.sagepub.comDownloaded from over siruilar obstacles with a rriachiiie fitted with otic of Professor Sharp's piicuiiiatic springs, and I could scarcely lccl aiiy juiiiy> even when passiiig on or o1l a kcrb-stolio. 1 Iciiew, of c o ~ l r ~ w , that I was ieidiiig up and down sucli a licrb-stoiic, bu t Iiad i? iiof bccn for ~ u c l i previous lriiowledgo I do iiot bclievc I should hnvc lrnown that I t.vm goiiig ovci it. The piicitmLttjc sprinp, i n combination with the piciiniattc~ 1 hlot out cverythiiig iii the way 01 violciit osci a \\o iy wiooth path. I wish, therefore, to coiigra,tulatc Pro- S h q 011 llaviiig achieved a practical result ;Lftcr nil thew of labour. I bclievc his greatest dilfkulty has beeii nitli icgani to the niitten, for 1 have watched Professor S h a ~ p ior sovcrd years struggling with thk cyucstioii, b u t he sccni\\ iiow to have ovcrconie that trouble iii his preseiit tlcisigii, \\tliicli has expailsion iii o w dircctioii, but iio elongation iii llic other. A t the rccerit Motor Show tlierc were other air spriiip exhibited, on the Crosslcy car for instaiice, bo that iiiolor-car iiialiers nre i iot .v cvideiitly titrniug their attenticxi to the pncuniatic springiug o l cars. A !)art from a i r springs, the geiieral qtic\"ioii of tlie spriiigis the subject of iiiitcli cuiisideratioii; it is probably oiw of blic i~iost iiuportaut queskioiia: iii tho design of the car at lie presoiit nioiiieut, and is intimately coiiriected with that uf speed. With thc slow moving dray i t is possiblo .to clo without sp~iiigs, and not fcel anything of a shock, but directly speed is increased, effective springs become essential. I was going to say soinetliiiig about shock absorbers, but the Ru t l io~ has explained the differciice botivceii a slioclr absorlwr am? a spring so clearly that 1 need iiot fitrtlior allude 10 tlic iiiatter. I will now ask you to give Professor Sharp a hearty vote of thanks for his most interesting and valuable paper. Colonel R . E. CKOMPTON: The last t h e 1 was asltod to uoiiiineiice a discussion it was 011 a, subject vory cognate to this, namely. on spring wheels. On that occasioii I was accused of being severe on the Author of the paper, but I believo Professor Sharp substantially agreed with all I theii said. It is a groat plcasure to inc to be i n hearty agreement with Professor Sharp this evening, and, being a learner inlore than a critic, T will confine my remarks to asking a few qucstioiis. Fo r many years I Elavo followed with groat interest Professor Sharp's labours in dovclopiiig t l io iiiiporfaiit quosfion of tlio uso of air Nprings, THE INCORPORATED INSTIT~J'l?IO~ OF AUTOMOBILE ENOIWEERB. at UNIV OF VIRGINIA on June 9, 2016pau.sagepub.comDownloaded from aiid Iia\\ c aln a j s iiitcndcd to coiiie to liiiii fur advice iii tlesigiiiiig sucli hpriiigs for coiiiiiicrcial veliiclcs. Thcic l i a b c frcq ueiitly 1 o tra\\crse rough ground, as rough, in fact, as that ~\\LiicIi acroplancb have t o traverse kicforc t h y rise froiii t h e groiiiid, as piiitcd o u t I)y thc Aiitlior. rlllierefo~~o fij)riiigs liai iiig groat i ~ i i p e (11 action a ic IWC 1 vcliiclcs iiilcndrtl for use 111 the oolonic~ tairly successful in 1ny tlcsigiis with steel springi, bu l I \\\\is11 Proiessor Sharp had had hib ideas far enough ad\\ anced tno ago, 6\u20190 that 1 could have cnibodied tliciii n ith conlitlcticc iii iiiy dcsigiis at tliat time. Wlieii I approached him he was not tlieii ready. I tliiiilr we iriust all agreo that in this paper he has slionii ihal hc has fairly and successfully grappled with the springing probleni. This question of applying springs to heavily loaded yehicler is a complex one; conimercial vehicles uiay niahc long journeys with empty trains, returniiig with the train fully loadcd When the trains arc ruriiiing viiipty, tlic spccd is riaturally highcr tliaii whcii tho trains arc full , so that t h o slwiiigiug coiiditioiis iir the two cases are very dificreiit 111 1tio oiic caw we have high speed with cmpty waggons, in the other, low speed a id loaded waggons. I t appears that I\u2019rofcssor Sharp Iia5 givcri us a means of meeting this difficulty, as by altering tho ail* coinpression on the two journeys it semis likely that we can obtain satisfactory conditions lor both. So too with a heavy gun which must sometimes be taken off tho road across broltea country at a fairly high speed, sometimes it will be taken over hard roads at a higher speed, and then agaiii, it must be put iiito position for firing. Profcssor Sharp\u2019s dcvico I tliirik will meet all three conditioiis. I am anxious that he should give us some idea as to how far he can go in using very large air springs to carry heavy loads, that is to say whethcr lie will use groups of cylinders not exceeding Gin. diameter, or single cylinders of large diameter. if hc uses multiple cylinders, arc they to be arranged in group3 longitudinally t o the cliassis, or can they be arranged transversely, that is, with their axes parallel to the axle below them? Professor J. B. HENDERSON: When we first tacklo the problem oe Ilio springiiig oP a c a ~ i t scoiiis vory sitrq)lc, for so long as the Cb . I ha\\ e bcc11 v3ry There is another poiiit 011 which I am curioui; at UNIV OF VIRGINIA on June 9, 2016pau.sagepub.comDownloaded from car 1s on the level, the wheels will rise and fall over the ripples OIL the road, without nioving the car, provided the forces between the car and the axles are constant. Such a condition is praclieall) obtained i f the car body is supported on the pistons of four air cylinders, which are connected with an air reservoir of very large capacity. Rut the springs have othor lunctioris to perform besides that of consuniiiig the ripples on tho road surlac(> They have to accelerate the a r body vertically when aiiy gixdicmt is enoouritered on the road. With the abovc arrangeirteirt of air cylinders and very large reservoir, the pistons would kiiocli on the ends of the cylinders at the boginiiing and ond uf cvcry gradient. This knoclririg can only bo avoided by inirwlucing other special springs to produce t_he acceleration or by reducing the volume of tho resorvoir so that tho air pressure ilia\\ vary as the piston moves through the cylinder. This variatioir of pressure as the piston moves, at once does away wilh tho 1)obbibility of entirely preventing the road vibrations I\u2019rom reachlug the car body. Tho \\ p i i i g are kept as flexible as possible in order to consume the l\u2019l])\\Jleb, aiid at the same time they must be strong enough to mcclcrate the car body within a given range of motion, under ~ 1 1 tho practical oonditions of accelerations met with on very w a ~ y and rutty roads. The modern introduction by some inalrcrs of light llesible springs in series with the main springs, improves tho power of consuming ripples, but unless the available range of motion of the car body relatively to the axles is inorcased, they simultaneously reduce the vertical acceleration obf,iinable without the Icar \u201c bumping oa its springs,\u201d in other woids, they reduce the energy which can be stored in the spring5 \\ d h tho given range of motion. Now, the amount of energy which the aprings have to storo t u prevent \u201cbumping\u201d has been determined by :t process ol\u2019 evolution through innumerable failures of car springs ; hence, in oomparing springs of different kinds it is essential to compare thcm on tho basis of the energy which they can store with the same given deflection. I would like to ask Professor Sharp i f he has made this the basis of his comparison. Z\u2019rofessor Sharp states in the paper that the rcsiliencc is a maximum i f the material is in simple tension; but the resilience in torsion is still greater in the ratio of 20 : E or approximately 1\u20193 : 1, although the material is not all subjected to the inaxinium The final solution is 0110 of compromise. -b THE INCORPORATED INSTIT~J'l?IO~ OF AUTOMOBILE ENOIWEERB. at UNIV OF VIRGINIA on June 9, 2016pau.sagepub.comDownloaded from initial stress. A close-coiled spiral spring is there\u20acore the most econoniical of inaterial of all springs Tho design Professor Sharp ha5 &on n is extrciiioly ingenious. I should like to ask him i f he iiitcndr to lubricate the sliding sleeves, as hc obviously will havo trouble with oil getting oil tho rubber. Professor Sharp draws a coinparison betneon t hc woighi ~ l \u2018 bp ing pi& unit !oad wapportcd in his air spring h l f e r and L I I the metallic springs in a heavy locomotive, much to the dotrinient of the latter. But i t is evident that hc is forgetting alfogcther the influence of dimensions, and also tho diITercnt conditionr of design. Why doesn\u2019t he coinpara if, with the might per uiiit load supportcd i n the spiral springs for thc fronl, E o r h or t,lio bicyclc which his air buffer replaces? The couipsrisoii would then be a good one. In similar st,ruoi,ures the m t i o 01 woiglil of any part to strength oE tlic part i ne reas s proportioiially to the linear diineiisions; hence ihe larger a structure is the greater will be the ratio of the weight of spring to strengSlh oi\u2019 spring., i . e . , the ratio of m i g h t 01 spring to load carried I think i t is a pity Professor Sharp in his introdriction eorninils himself to a numerical example which has no praclicnl moaiiing. Re assumes infinite rigidity in a wheel, and a n obstructiorr, i i i i c l then deals with an average force I3ut i f the wheel, obstruction, and ground were infinitely rigid, the Porw would be infiii ito. Hence. in all practical cases, the obslruclion, or lyre, mubt yioltl, and somewhat more pract ical conditions niiqht have been assumed. I understand, however, that Professor Sharp has written this paper at a weck\u2019s notice to 811 a gap caused by Mr. Lancherter\u2019s illness, and I therefore present these comments in n o spirit of carping criticism. Ile certainly deserves great credit for presenting such a good paper in the time a t his disposal. Mr. DOUGLAS L~ECHMAN: It must be grtting on for fen or eleven years since I had the first introduction to Professor Sharp\u2019s invention. I did not try i t LIP and down kerb-stones, bul I tried it over baulks of timber in a ball-rooin, and the effect was most surprising. 1 have always understood that tho most cfkctive spring obtainable is a gas. I do not know vvhcther Professor Sharp, on page 91, is merely spcaking of metallic springs whcn he says the most effective s p i n g is a very long wire or lie-rod. Professor SHARP. I referred to steel springs. Mr. MARK BARR: I have nothing to add to tho discussion, at UNIV OF VIRGINIA on June 9, 2016pau.sagepub.comDownloaded from pt wliai, i s of a, conipliincntary naturc. I rcuionil)er r on a niarhiric fitted with onc of Professor Sharp's air springs, taking it OT or bricks and other things, and experiencing iiothing in the may of trouble. I shut niy eyes when riding over a kcrlnstone, arid I did not know that I had riddeli over ii, 'Phis I swear to. RTON: I ha le had some expcriciicc of I'roprings i i r tlic cnrly days; he was kind onougli l o S L L ~ J ~ ~ Y ine nith some which I Iittcd to n motor tricycle. From iiiy c.ipcrienco of llicir working it secms t o ino illat ihcrc is sonicthing about theiii vliicli is independoiit of all iIi(? t ie l ail5 of c~o~~striirtion. Pcihaps Prol'cswor Sharp, froin his latcr rxpcrirnco, iiiay lia\\c overconic the particular clificulty to whirh T wish lo rcfci. l'liore sccnih t o i ny iriind to be n radical dcfcct wi ih air slwiiigs whcn the springs do not all lie and function in 0110 ~)lanti, as i q tho case with :L hirycle; when all are in one plane tho thing is a perfect success. These bicycles, now exhibited with new inittens and new construction, leave no doubt i n my iiiintl that thcy, or any vehicle i n which the springs all oscillate i i i oiic planc, are hixilrions; hiit in a vohiclc lipving three point rc Conics a groat difficulty. Ti, is this. If the \\rtiirlc is to br luxurious it rnrist be supported liy air v~liicli aro just a sinall pcrconiago aliovc what is lie lrold the wcighi i n snspcnsion. Conscqneiitly, mhcii t is supported at three points i n a horizontal plane ovor tho grotind, with a very slight oxccss of pressure, tho question of 1:~lcral stability comes i n . Whcn you are ilcaling with triryclcs i i i which tho livc load is a considerable proportioii of thil weight of the. vchiclc, lhero is a want, of lateral hlabiliiy, uiitl il goei tltfivn \\ t r y mncli oil one sidr ~vifhoiit a siiffiriciit ' I righiing ovcry forco. Coiiseq~iciitly, i n 1113' iricyclo, I l'oiiiid a grrat, deal of insiability. Thmc is :t critiral poilit i n i l r r inflation of these air springs which, i f (.xcoctld on ihe lowcr sitic, give9 a foeling of inrtnhility and dangcr. Thcw air springs i n r i d l)c piiinpcd irp very hard, and 717hen this ha^ h e n tlonc. thc advnritages of air suspension arc lost. I should Iilro to ask I'rofessor Sharp \\\\Jhat he has doiic to niert tho difficulty which arism from applying theso springs to vchiclw which nocd suspriisioii i n a liorimnial plane. Mr T I I [ . IJODNS1'7 n: I wonld like to endorm tho rcinarlis o f pixyioiis spralwr9 witli rcfi\"rd i o i h o qnality of' ilir p p e r , THE INCORPORATED INSTIT~J'l?IO~ OF AUTOMOBILE ENOIWEERB. at UNIV OF VIRGINIA on June 9, 2016pau.sagepub.comDownloaded from but aR tiin0 is short I will not ondaavonr t o say inore in that mspect. I: do not want to appear to beli.ttlo t.he -117orlr that Profeisor Sharp has done in coniioction with pneumut.ic springs, far from it. I can look forward to the time when pneumat.ic spdngs will onablo us 'to have much choapcr tyros. :I shoiild lilw Professor Sharp to txplain. one point, and I sEioulil lilro him to put it forward in a way that can be absorbed by my brain. In the cuwo OIL page 105, he hw shown what is practi.cally !L straiglit; line. I .imagine tliat a spring will be .useit as D stop whon the piston gets to the end of its stroke. We can. rel?rosont; that as a draight line going of at mine stccper angle froin the other cu.rve. Si~.ppose wo hiivo 811. t?xtremcly lorig and thin laminated spring so as to givo u period of vibration equal to that wliich Professor Sharp geB from his bi.cyclo. It wou.ld bc riiuch. too weak to carry a car i n the ordinary way. If abovc that we piit a spiral spring with a rubber buffer to tako the plam of the steoper part, of tho curve, tho difleronrfi between tho total effect of the springing in such a system, aad t h t of Profeswr Sharp's, seems tc., me to be that i l l the l.i~ttt?r a CI.WVO will represent the relation of deflection to load, and that in tho former it will he rcpresentod by a straight liiio. !l!heii, of noursc, tioii in either cam. Wou1.d Professor Sharp mind explaining what tho actiiril. iliflerence won.ld. hc in. thwc two Rystfims of springi.n.g? I havo :not had the good. fort;unej like the provioun spor~korfi, to knmi Profosxor Sharp, hit frorri my e yer icnce of .pti.eimati.c wwpen.siori I lamw it has a vast mperiority over oRior rnotliot'ls of Niupnsion, but :I shori.ltl :l.iko him t o piit, i.1; in iL way thrtt, :I can -understand. Mr. J . Srr~r~mni:,awn Wna~irm: I have givon a good deal of attention. to the qucstion of the porfeot running of vohicles OI.I rails, and if anyone w a d 3 staridad definitions to worl~ from, I: fihall bo plcased to refer him to soine which I: think might 'bo wry useful. I got out a set of cfefinition.s for: vohic~lcs riiming on plane surfaces wliich I embodied in a papor r e d , beforo t.hu Civil and Mechanical ISngineers Society, Dcceinber 3rd, 1.908. * 'I: think Professor Sharp would bo able to d.eal with this su2)jei?l; on rather more solid and fundamental, Rimplo geomct.ri.cal linov i.T I i n l iad s.0111~ siinh d.e:fin.itionR. J Pahlislied in thr Trnrnrcny cntd llniltrcry JVog-ld, JMI. Znd, 1909. - \\ - v h tho . shp i s rea(:hotl. the Atriigllt; line repro~~ri.l;r tho rola- at UNIV OF VIRGINIA on June 9, 2016pau.sagepub.comDownloaded from l\u2019rofcssor SHARP, in replying on thc discussion, said : Mr President and gentlcnien, I havc to thank you for the coiigratulator) terms in which you have referred to my paper, and to include Colonel Cromptcn particularly. With regard to tho Coloiicl\u2019s qucry as to springs with hoavy loads, I do not see that aiiy tcchiiical difbculty will arise in rnalring air springs of v e ~ y big dianictcrs. In fact, as I havc already said in the papcr, the \\ulnerablc part of tho spring i 3 the mittcn, and for all sims of air springs I purpose ur inf i practically thc sanic f liiclrrioss of fabric that 1 liave lierc. Tlic function oC tho mitten is to bridgc over the narrow space between the cylinder and thc plungcr in which wc iiiust allow it tro turn upon itself. rT 1 may bc allowed to suppleniciit niy rmiarks, 1: inty add o m or 1,no sketches in ansirwing this point riioro in dctail WitE rcgard to Professor Hendcrson\u2019s rcmmks, I do iiot look Li1)ou i t as a queiiioii of t h o rcsiliciicy of torsion spring3 ai coiii- pared with tic-rods. Rcferring to the forinulm he quoted, viz , f 72H andfL/4C, I thiiik in the formula relating to the resilience of a tie-rod in tension the factor f represents the tonsilo stresi; 01% tlic material, whereas i n tho torsional formula it rcpr oriothcr thing allogcther; it is the shmring slross \u20181\u201911 question as to lubrication is pmrtical one. In lubricating such an air spring o m may vas(.lino or grcasc inside tho piston, but the outer snrfaclo, namoly, thal part, of thc pluiigri which is guided in the nccli, mid on which the riiitteii rolls, ii lubricatcd with dry grapliilc., and, in practim, a little dust cap is uscd which fastcns round thc neck, excluding d w t and grit from the rubbing surfaces. W;th rcgard to hir query as to tho influcnce of dimensions and his romparison of the wcights of strcl and air springs, I riiay be allowed to say that in the air spring the weight rcquirctl i s i l i ~ weight, of i h e cnvelope coiitaining the reriliciit medium. 011 turning to Cotterill\u2019s \u2018\u2018 Applied Mechanics,\u201d i t will be fouiid that the weight of such a strueturc is proporlional to tho resilicnce of i h o air, just as the \\vciglit of a steel spring is proportional to the ciiergy it can store up. Mr Chatterton has raisecl a point which is very irriportant; it iq one of the points whicah made me expross the wish that I should have liked to have road the paper at a later (lato. Rut without spending much time in an5wering tho question fully, I may just indicatc by a diagram the po\u2019sibiliiy of gctfing iuore than I have already stated THE INCORPORATED INSTIT~J'l?IO~ OF AUTOMOBILE ENOIWEERB. at UNIV OF VIRGINIA on June 9, 2016pau.sagepub.comDownloaded from PNRUMA'I'IC: SPRTNCrS IWlt ROAD VRITTC1,ES. 119 F I G . 16. The diagram (Fig. 16) represents the cross section of a motor ciir, showing two road wheels of the vehicle. When the vehicle moves along the straight the reactions are vcrtiral and equally divided 1)cItween the two whools. Suppose I arrsiigc the air springs A and tie rods T at an angk, both being jointed at one end to a sleeve on which the road mhcel brarings are mounted, arid at the othcr end jointed to the chassis frame, the two sleeves being freely mouiitcd on itii axle, vhich preserves the alinement of t h wheels. Tho SHARP. I at UNIV OF VIRGINIA on June 9, 2016pau.sagepub.comDownloaded from 120 THE INCORPORATETI IR\u2019SFITUTION OF AUTOMOBIJX ENGINEERS. dingrain of forces for the air springs and tie rods when the vehicle is moving along the straight is sliowu by the first pair of triangles, the force A,) to be supported by the air spring being much greater than the normal wheel load N. \u2018L\u2018hu mutual forces between the sleeve and axle do not affect this diagram, hut they constitute a coupl(~ oyual to N multiplied by tho porpendicular distance of the point of intersection of A and T from the line of action of N. Buppose, next, thtat t,he vehicle is tuvning to the right, and that the radial or cantrifiigal forco is half the vertical load. Let G I bc tho virtual mass-centre of the load carried by the axle, then the resultant of the reactions R at the two road wheels passes through Q,, and intersecting the ground nearer the left wheel, the vertical load V on the left wheel is greater than N, while the vertical load V on the right wheel is less than N. The pair of diagrams (No. 1) show the forces A on the right and left air springs, on the supposition that the horizontal components H are proportional to the vertical components V. R for the right-hand wheel is now just about equal to A,, and is in the same direction; there is now zero force on the left tie rod. Thus the left air spring does not tend to lei tl,e left side of the vehicle either sink or rise. The force A on the right air spring is now less than the force A, to which it was i i i i tdly pumped up, and the right air spring tends to let the right side of the vehicle rise. The point Q k in the diagram has been chosm 80 that the ve &a1 loads on the right and left hand wheels are respectively two-thirds and one and one-third the normal load N. II\u2019 the mass-centre is relatively lower, as at Gz, or thc wheel track relatively greater, it may be possible that the left side of the vehicle ~ l lay rise and the right hand sink, the air springs giving a niovernent to the body of tho vehicle analogous to that automatically obtained in R bicycle. The point Gr, has heen chosen in the diagram such that the vortical loads on the right and left hand wheels are resi,ectively * 8 and 1.2 times the normal load N. The pair of diagrams No. 2 now show the eorces A on the air springs. I n the left diagram R is coiisiderably less than A,, the force to which the air spring was pumped up. The left air spring therefore tends to to its fullest extension, lifting the left side of the vohicle. Jn thr right diagram A is greater than A,, and the right side of the vehicle sinks. The PRESIDENT asked if Mr. Chatterton\u2019s springs were vertical. Mr. CHATTERTON: Practically. at UNIV OF VIRGINIA on June 9, 2016pau.sagepub.comDownloaded from PNMJMATIC SPRINGS FOR ROAD VEHICIZS. 121 The PRBSIDRNT: 1 think Professor Sharp ha.: answered I hc y liestion thoroughly. BRTON: It is a difficult question. I\u2019rofessor SIIARP (continuing). With regard to Mr I louns6eld\u2019E rcmarks, it was far froin my mind to suggest that there w i t s ally virtiio in an air spriiig as compared with a stccl spring TC t ho load-conipression curve for a long steel spring is tho same a , that Tor an air spring, the primary propertie.: of the l w o iprings would be the sanic This raises a point that I should liLe to have raised in the papor. If you do have a long h twI apririg of this kind, its own tnass is a consideration to he iLdtlodi l o l h e un-sprung load. The greater part of the weight or suoli a. jpring is in the middle, SO that the spring itsell\u2019 is nol, spring supported. On the other hand, tho caritilever springs used on liarichester cars are better in this respect. 12 at UNIV OF VIRGINIA on June 9, 2016pau.sagepub.comDownloaded from PNEUMATIC SPRINGS FOR ROAD VEHICLES Plate XVII , at UNIV OF VIRGINIA on June 9, 2016pau.sagepub.comDownloaded from PNEUMATIC SPRINGS FOR ROAD VEHICLES. Plate XVII I . at UNIV OF VIRGINIA on June 9, 2016pau.sagepub.comDownloaded from"
        ]
    },
    {
        "image_filename": "designv11_36_0002547_piae_proc_1920_015_011_02-Figure8-1.png",
        "original_path": "designv11-36/openalex_figure/designv11_36_0002547_piae_proc_1920_015_011_02-Figure8-1.png",
        "caption": "FIG. 8.",
        "texts": [],
        "surrounding_texts": [
            "several long springs working in combination, care would have to be taken to see that the springs did nok foul each other, and numerous guides would be required, while there would &o have to be many small pins and eyes, bolts, etc. FIGI. 9 With extension springs it would be difficult to work in a cornbEnation type, and the oinly suggestion is to change the action from the non-progressivse type to a, resultant action in which the load was no longer directly proportional to the deflection. This at PENNSYLVANIA STATE UNIV on June 5, 2016pau.sagepub.comDownloaded from THE SPlZINGIKG OF MOTOR CYCLES. 57 could be done without much difficulty by altiering the leverage of the spring on the links as it way extended, or by inoreasing tha rate a t whioh it was extended for a given movement of the wheel. Experience hes shown that in parallel mound extension springs, the safe valuie of the stress per sq. in. is only about two-thirds of that fon open coiled coinpression springs of the same dimensions; other considenations may, hoivever, outweigh this disadvantage. The author believes that pneumatic springs h w e been used on motor cycles yeam ago,* and they have much to recommend them if the mechanical difficulties can be overcome. A last alternative is the volute or conical spring, which can be made to practically any rate of progression, and it would seem to be worth while experimenting with this type. I n one type of front fork, conical springs acting in conipression are dmady fitted, but they are short and ane only very slightly taper. A conical spying is not satisfacLory when used in extension, as sufficient load to fully stress the smaller or stiffer coils cannot be applied without distorting thee larger coils. Blefore leaving this side of the springing question, it would be as well to discuss the merits or demerits of friction, and this has lately been a much debated question. For perfectioa, a damping rlevice which would come into action after the first big deflection either way, after the wheel has passed its normal position, is desirable. I f the author could not have this, however, he would prefer to have friction in the springing of a motor cycle rather than none a t all, chiefly la steady the springs and damp out oscillations, this especially when the machine is travelling over a, road with more or lesls regular undulations which happen to fit in with the natural period of the motor cycle suspension. The objection to friction, as pointed out by Mr. G. H. Baillie in his! paper before the Institution in 1913,: is that it increases the change of accderation, and change of acceleration causes that jerk which is uncomfortable to the rider or passenger. I n the caste of a car, as there is very little danger from the cumulative effect of regular undulations on the springing (which would be greater with no friction in the springs), comfort is the first considwation. On a motor cycle, however, the case is different; the machine is in a state of unstable equilibrium, and as * SeeProc. I.A.E. Vol. IV. pa 87. + See Proc. I.A.E. Vol. VII. p. 451. at PENNSYLVANIA STATE UNIV on June 5, 2016pau.sagepub.comDownloaded from 58 THE INSIIlUT1ON OF AUTOMOHI1,R ESGINEERS. this cumulative effect on springing could be very dangerous, the extra or excessive comfort must be a very secondary consideration. On a considerable number of machines now horizontal springs are also fitted on the front forks ; the wheel is thus sprung in two directions, and that these springs do useful work can be appreciated by siding a machine SO fitted. In the author\u2019s opinion, however, these are only useful when vertical springs are too stiff, and on a front fork fitted with reasonably flexible springs the horinontal springs would not be required, especially as the motor cycle front forks (are already a t an angle of ab\u2019out 30 degrees to the vertical in the direction of the shock. A point that has b\u2019een raised in objection to these horizontal springs is that the steering lead is continually changing, and that there would be danger when riding round a curve. A inovenlent of ab\u2019out one inch is fairly usual on these horizontal springs, which would be lfr in. to 2 in. on the wlieel. I n the author\u2019s experience, these horizontal springs do not have any particular effeclt on the steering, although i t is possible that they might at high speeds. The question arises as to whether it should be arranged that the springs give lateral support to the forks. That the laminated springs do give lateral support on most makes of cars is well known; at the same time it should be remembered that a certain ainount oE side play on the axles of the ordinary touring car does not matter, while on a motor cycle practically no play at all can be allowed. The question is a compromise, and the author only says that if possible it would be better to arrange that suitable faces should give lateral support, and the springs take their direct load only. On the type of spring which is fittied with an eye and shackles, if the bearing in the spring eye is to work nioely, it must have some clearance on tihe sides, s o that biefore the spring clan help in the lateral stability the bearing i n which the rear fork is hinged must have worn enough for the fork to rock over and take up this clearance. In the gmthor\u2019s opinion, by the time this biearing is wjorn to that extent it ,requires renewing. In the A.B.C. type of springing, Fig. 10, the spring does give lateral support to the wheel, as it is b b h d solidly at each end to the frame and the rear fork respectively. DQaling with the eye of the leaf spring, on several makes shackle plates and pins of good proportions are employed, and on the Royal Ruby patented roller bearings as shown in the upper part of Fig. 4 are fitted to eliminate lateral play, and they should at PENNSYLVANIA STATE UNIV on June 5, 2016pau.sagepub.comDownloaded from work well. The author thinks, however, that these shackles are a refinement, and he would recommend in a great inany cases simply a flat end to the spring and no eye. A roller for the spring to work against is unnecessary, it should simpIy work against a fiat face; a t the end of the back of the spring should be a crosspiece, with possibly a rubber buffer to catch the spring on rebound or when the wheel drops into a hole. An objection tao &is type is that there would be a tapping noiw if the end of ihe spring left this face, but the author has ridden a maohine so fitted, and he experienoed no inconvenience. This hype is ,much cheaper to make, and the possible noise could hardly be counted a slerious objection until the motor cycle engine is more silent ,than it is at preslent. English designers throughout s h d d remember Ford gractioe a liktle more-eheap and sinipls and doesn\u2019t look nbe, b\u2019ut the public gets used to it, and it works -Ford taught the public, and didn\u2019t let the public teach him. It would be as well to compare the different designs of front forks, of which there seem to be three distinct types. The most usual k the paralleI link motion type, whcere the links oonneat from the top of the front forks to the head of the frame, then the type i~ on the Triumph and the Beardmore Precision, where the front fork i s hinged at the crown, a d lastly the design which seems to be popular on American machines, and which is also embodied in the Phelan and Moore front forks, where the con- at PENNSYLVANIA STATE UNIV on June 5, 2016pau.sagepub.comDownloaded from 60 THE INS'l ' lTtiTIO~ OF AUTOMOBILE ENGINEERS. necting link coineb straight off the wheel spindle. I t would be hard to say which type is best, as they are, in Cioimiion with mosti engineering problems, a conipromise ; of the three, the author prefers the first mentioned, where the links bridge from the top1 of the front forks to the l i e d . The bearings in this type are long, easy to lubricate, easy to adjust, accessible, simple and out of the dirt, and in practice they stand up quite well. The tendency is now to make the link spindles of larger diameter, as on the Douglas type shown in On the P. &: M. and American type, there is the advantage that when uring helical springs, the angular movement of one at PENNSYLVANIA STATE UNIV on June 5, 2016pau.sagepub.comDownloaded from THE SPRINGING OF MOTOR CYCLES. 61 end of the spring in relation to the other when bieing compressed or extended is less than with the first nientioned link motion type, and another advantage is that there will ble slightly less unsprung weight. When the wheel is in front of the bearing it hinges from, it would seem t.hat one advantage of this type is delstroyed; if the wheel is behind the bearing, it is trailing, and its position could be such that it would be readily responsive to road shocks from a large range of directions. A t the same timr, howlever, the at PENNSYLVANIA STATE UNIV on June 5, 2016pau.sagepub.comDownloaded from"
        ]
    },
    {
        "image_filename": "designv11_36_0002629_jiee-1.1907.0063-FigureI-1.png",
        "original_path": "designv11-36/openalex_figure/designv11_36_0002629_jiee-1.1907.0063-FigureI-1.png",
        "caption": "FIG. I.\u2014Retardation Curve.",
        "texts": [
            " At any point on it corresponding to a speed of n revs, per minute, the value of \u00bb, \u2014 n2 is obtained by scaling the difference in height of the curve at 1907.] OF THE LOSSES IN MOTORS. 441 speeds nt and n2 at equal horizontal distances on either side of n. The value of t, the time interval corresponding to the difference nx \u2014 n2, must be taken so small that the curve is practically straight within these limits. Usually the time interval between two successive readings would be suitable. Arnold* has shown that instead of the expression n nx \u2014 t the subnormal to the curve at the point corresponding to speed n may be taken. Thus in Fig. i\u2014 \u00abi \u2014Jh\u2014Hn _ A B _ A B_ t a n a _ g p _ - _ and the watts spent in retardation at point P = K x A B , Thus it is only necessary to measure the length of the subnormal A B and to multiply this length by the constant K. In my own measurements I have found it best to measure off the length tz \u2014 ta as first described, employing spring-bow dividers for the purpose, rather than to measure the subnormal. Determination of K.\u2014The chief variations in the form of the experimental determination of losses by this method, as proposed by various experimenters, are to be found in the method adopted for the determination of K"
        ],
        "surrounding_texts": []
    },
    {
        "image_filename": "designv11_36_0002549_jiee-1.1917.0030-Figure11-1.png",
        "original_path": "designv11-36/openalex_figure/designv11_36_0002549_jiee-1.1917.0030-Figure11-1.png",
        "caption": "FIG. 11.",
        "texts": [
            " triangle, which as it is of very general application it may be of interest to give. We gave above a general solution of the quadratic equation in complex quantities for any values of the coefficients. We have now to consider what are the values of the coefficients in the case we arc considering. The equation which results from the differential equation in the case of rotor resistance is (;-2//()S 2 \u2014T-S-;/> = o. Hence c = \u2014jp; a = t'lfi; b = \u2014 v (see page 455); and following the construction we must draw our circle passing through the extremity of O B = ; ^ (see Fig. 11) and touching the real axis (since a = o). Since O B is at right angles to the real axis it is a diameter of the circle. We saw in general that O P = fcS= \u2014 i'S in this case. Hence our speed construction will be as follows :\u2014 Dr'aw the locus of the current vector S2 = (pic) cot 9 as before, and also the circle as above. Corresponding to any current vector OI draw a line O C to cut the circle, 458 CREEDY: ELECTRIC WAVE PHENOMENA making an angle 2 $ with O E. Join B C ; P will be the point where B C cuts O I"
        ],
        "surrounding_texts": []
    },
    {
        "image_filename": "designv11_36_0002530_piae_proc_1909_004_009_02-Figure15-1.png",
        "original_path": "designv11-36/openalex_figure/designv11_36_0002530_piae_proc_1909_004_009_02-Figure15-1.png",
        "caption": "FIG. 15.",
        "texts": [
            " 107 the stroke of tho central plunger relatively to the outer cylinder is 2Q inches, thus giving ti total stroke of 59 inches. The drdwiug 8 1 ~ 0 ~ s the air spring fully co~upresseed. If this air spring is used UII H, raid vuhicIc the air sliould be pumped to such tt Immure that I F I G . 14. when supporting the normal load the middle plunger is b l o w n out to its fullest extension relatively to the outer air cylinder, while the inner plunger is just ready to begin its outward stroke relatively to the central plunger. The load-compression c*urve for this spring (Fig. 15, analogous to Fig. 11) would sliow a curved portion CF, at UNIV OF VIRGINIA on June 9, 2016pau.sagepub.comDownloaded from at a very slight incliriatiou to the vertex a i i s OA, the vcrtical distalice A13 cwrespondiiig to the 3-inoh stroke of tlie inner plimgcr. Yroni the point l! on the load-oxteiisioii curvc there ~ o i t l c l bc i~ mtide~i chaiige to 2% Iiori;..onlal line PY, , the ratio UF, to lib' Iwirrg cqual to the ratio betwceii the supporiiiig areas of the outer aud i~ iuer air springs"
        ],
        "surrounding_texts": []
    },
    {
        "image_filename": "designv11_36_0002669_s0370164600007653-Figure3-1.png",
        "original_path": "designv11-36/openalex_figure/designv11_36_0002669_s0370164600007653-Figure3-1.png",
        "caption": "FIG. 3.",
        "texts": [
            " Of the twelve inflexional tangents only four are real, viz., the four asymptotes, each of which meets the curve in four points at infinity. Since the curve is unicursal, its quadrature can be effected by means of elementary transcendents. Its quadrature depends on the integral J(i sin2 26> + 9 cos2 2(9)/cos2 26, which can be expressed in.terms of elliptic transcendents. Triseetion of an Angle by means of the Ruler, the Compass, and a Sextic, Trisectrix Template. Let a template be constructed, one of whose edges, 0 A (fig. 3), is the a;-axis of the sextic trisectrix when represented by the equation (3), and the other the branch A E of the trisectrix. Then we may trisect any given angle UOX (<135\u00b0) as follows:\u2014 Place the template so that its 0 falls on the 0 of the given angle, and :O A on one of the arms, say O X. Mark the point P where the curved edge of the template meets the other arm O U. With 0 A as radius and 0 as centre, describe a circle; and with half 0 P as radius, and the middle point of O P as centre, describe Core terms of use, available at https://www"
        ],
        "surrounding_texts": []
    },
    {
        "image_filename": "designv11_36_0002547_piae_proc_1920_015_011_02-Figure5-1.png",
        "original_path": "designv11-36/openalex_figure/designv11_36_0002547_piae_proc_1920_015_011_02-Figure5-1.png",
        "caption": "FIG. 5.-3rd H. R. Stop Spring Design on Triumph Machine.",
        "texts": [
            " AfOer some running, this middle rail showed signs of sagging, and i t was changed for one of a bea-,ier gauge, after which i t gave no trouble. The machine was, of course, only built up as an experiment. The deflection from the pormal, as far as the author can nemember, was 3 in. to 4 in , and it was a very comfortable machine to ride. Another deqign, which ma3 got out by the author, was the fitting of rear springing to a standard Triumph machine. There waa nothing particuhrly original ,ablaut the design, the general arrangement of which can be seen from Fig. 5. The carrier and rear mudguard wene unsprung. The spring had a flat end, with no eye or shackle, but behicd Rhe end was a CTOSS bar, which caught the spring m sebound or whlen the nmr wheel dmppe62' into a bole. The details Qf bhle main spindle bearing can be seen in Fig. 17. Grooves were turned just inside the bushes to collect any dust and mud, etc. Ithat might work in. This d<esign was simple and substantial ; facilities and time did not allow at PENNSYLVANIA STATE UNIV on June 5, 2016pau.sagepub"
        ],
        "surrounding_texts": []
    },
    {
        "image_filename": "designv11_36_0002563_jiee-1.1899.0014-Figure6-1.png",
        "original_path": "designv11-36/openalex_figure/designv11_36_0002563_jiee-1.1899.0014-Figure6-1.png",
        "caption": "FIG. 6.",
        "texts": [
            " In order to measure the initial torque, a beam having a radius of 3*5 feet is fixed to the shaft, and the pull in pounds measured at this radius by a spring balance, the armature being brought to its zero position by raising the spring balance by aid of a rope passing over a pulley. The actual observations of pull are at the best rough, since the readings when small are seriously affected by the friction of brushes and bearings, but they are sufficiently accurate for the purpose of this paper. Fig. 2A shows details of the armature, and Fig. 6 gives details of the field and armature stampings. The primary or stationary portion, Fig. 6, is wound with two circuits marked respectively A and B. These circuits are so distributed that two-phase currents are required to give an approximate rotating magnetic field for starting purposes, and when once started the motor is intended to work on the single phase. The conductors are placed in holes, the main winding B consisting of 156 bars, and having a resistance of \"038 ohm. The auxiliary winding A has 144 bars, and resistance '045 ohm. The conductors A B in the stationary portion are not parallel with the axis of the machine ; that is to say any one conductor would not lie in a plane or be co-planar with the axis of the machine.. The angular-distance between the plates at the extreme ends of the core is the pitch of one tooth. The secondary or armature, Fig. 6, is wound three-phase with three circuits, C D E, which are pooled together at one end, and connected respectively to three rings insulated on the shaft. These rings are connected through brushes to a non-inductive rheostat capable of varying the resistance externally inserted in each circuit by steps as follows : open circuit, 2*37, 1*03, 0*42, 0*13 ohms at about 150 C, and short circuit; the ends of these three external resistances in the rheostat remote from the brushes are pooled together. Each armature circuit has 48 bars, and a resistance of -025 ohm, the bars being placed in holes in the armature",
            " v is the leakage coefficient. B is induction in C.G.S. units per square cm. r1=r^=r3=resistance of each armature circuit='025 ohm. pl=p2=p3=extra non-inductive resistance in each armature circuit; these can have values 00, 2*37, 1*03, 0*42, 0*13, and o ohms. nx = n2=n3=conductor turns respectively on each armature circuit C, D, E. = 24\u00ab yx yz >3 are the currents in the armature circuits respectively, in amperes. ex e2 e3 are the electromotive forces of the respective armature circuits C, D, E, in Fig. 6 ; that is, they are the potential differences between the ends of the respective circuits corrected for current into resistance '025 ohm. THE MAGNETIC CIRCUIT. Let the horizontal lines // (Fig. 3) represent the surfaces of the armature and the bored face of the stationary portion straightened out. The ordinates represent induction density; the areas induction. The windings A, B, are diagrammatically represented 00000 a n c j \u2022 \u2022 \u2022 \u2022 \u2022 respectively. The lower row of large circles represent the armature conductors",
            " If the distribution were represented by a sine curve, this coefficient would be -85, and has been obtained graphically. Referring to the figures, *37/\"83 = -446, and '6J6/S3' = -814 in io6 C.G.S. units. Of these it appears that -339 and '635, in io6 C.G.S. units, gets into the air space; that is, the leakage is 24 and 22 per cent, respectively. The fact is there is serious leakage across the teeth in this machine, but the coils 1, 2, 3, etc., have a thickness of *2 mms. and are covered with one layer of silk, so that they account for a portion of the air space. Coming now to the characteristic curve. In Fig. 6 the length of the air space (lx) measured radially lies between \u202215 and *2 cms.; the area of the air space Az is taken to be 210 sq. cms.; l2 is taken to be 7*5 cms., and is the length 1899.] THE INDUCTION MOTOR. 331 J of the teeth on armature and stationary portion ; A2, the area of the teeth, is taken to be 105 sq. cms.; l3 is taken to be 24 cms. and is the mean length in the iron ; A3, the area of the iron, is taken to be 200 sq. cms. Then the equation to ,, , , . ,. . 47rraI#i ( / i l l Iv ) the character is t ic curve is = 2 I -r\u2014 + 1 2 \u2014 r - + / , \u2014 T - \\ I O X 3 ( Ai ",
            " On open circuit the phase differences with regard to maximum induction are 480 for coils (3-4), (4-5), and 300 for coils (2-3), (5-6) as against 450 with a pure rotating field. On load these phase-differences are 720 and 720. 1899.J THE INDUCTION MOTOR. 335 Deal now with the armature of this motor. The armature being brought to the same position in each experiment by aid of the pulley-block, and the pull in pounds observed on the spring balance, observations were made for different positions of the phase of the primary potential differences Ex E2 and currents xx x2; the potential differences between the ends of each of the armature circuits C, D, E (see Fig. 6), and the currents yX) y2) y3, in each armature circuit. The relative position of armature and field in each experiment is as shown in Fig. 6. The electromotive force of each armature circuit, ez e2 e3, is given by correcting its potential difference for current into resistance of the armature coil. In this investigation, rx r2 r3 are respectively the resistances of the armature coils and are each equal to \"025 ohm ; px p2 p3 are the external resistances, in the armature circuits rx r2 r3, and constitute the independent variable. In any one experiment px=p2=p3. By correction for Rx R2 (the resistance of the primary circuit) into the instantaneous value of the current, the reactions mx \u2014i w2\u2014A have been found, and therefrom \u2014~ \u2014",
            " With an induction motor such use of the controller would result in an abnormal current from the line, but practically no starting torque. To give a complete account of this motor it would be necessary to observe curves for variation of frequency and potential differences, ~ET E2, and position of armature with respect to field. The preceding curves refer to a frequency 52 and V mean2 Ex and E2 = 60 volts. A similar set of curves have been obtained at frequency 95 and /mean 2 = 80 volts, the position of armature with respect to field being unaltered, and as shown in Fig. 6. The results of these tests are given in Tables X., XL, XII., and XIII. The collected results are given in Table XIV. It will be seen that the same character of result is obtained, namely, that as the independent variables pz = p2 = p3 are given values between 00 -and o, the torque rises to a maximum at about Pi = pz = p3 = '15 ohm, and then diminishes. These tests, as well as those at frequency 52, will be specially referred to in the next section on Armature Reaction. Table XVIII. gives a few other tests at other frequencies for which no curves have been taken"
        ],
        "surrounding_texts": []
    },
    {
        "image_filename": "designv11_36_0002616_piae_proc_1916_011_012_02-Figure29-1.png",
        "original_path": "designv11-36/openalex_figure/designv11_36_0002616_piae_proc_1916_011_012_02-Figure29-1.png",
        "caption": "FIG. 29.",
        "texts": [],
        "surrounding_texts": [
            "I t has frequently been urged, to some extent truly, that the Hindley or Lanchester worm gear requires greater precautions in mounting than is the case with a gear of the parallel type. The point is that whereas in the Lanchaster type the worm thrust has to be accurately located, in the parallel type 80 long aa the worm axis is correct as to position the longitudinal location of the worm is of no importance. The matter may be carried a step further; worm gear of the parallel type in turn may be said to require more careful mounting than common screw gear, in which both worm and wheel are of the ordinary screw-cut spiral form. Thus the argument that the Hindley or Lanchester gear is at a &ad- * In the parallel type of worm it will be seen from Fig. 16b that there is very little constancy in the type of the bearing contact ; actual concavities in the teeth frequently make their appearance with no proper driving contaot. Beyond this the mere degree of convexity, although a valuable indication, ia not the whole criterion in view of the squeegee action dealt with in the discneeion of the-previous paper. Compare Proceedings 1913-14, Vol. VII., p. 279.\u201d 102 THE INSTITUTION OF AUTOMOBILE ENGINEERS. ventage, on amount of the extra precautions required, aa compsrd with parallel worm gear, may be quite as reasonably urged against worm gear of every kind in favour of ordinary screw gearing suah aa commonly used to drive the side shaft of a gas engine. Suoh arguments are clearly without weight if any adequate advantage can be &own to exist. In practice the whole point of difference h i n p on the correot location of the worm thrusts, since in every other respect any want or loss of alinement affects both types of gear equally. It may be doubted tu a matter of experience whether the Hindley type of worm gear is actually at as great a disadvantage as its WORM GEAR A N D WORM (SEAR MOUNTING. 103 detractors would represent, the Lancheater gear at least has shown itself capable of working surprisingly well under the severe conditions which supervene when a worm thrust bearing fails. Admitting, however, that the durability of the gear does definitely depend upon the permanence of alinement aa determined by the thrust bearing, the problem resolves ih l f into the comparatively simple question of how, under manufacturing conditions, the initial accuracy of alinement can be secured; beyond this, the durability of the alinement resolves itself into a question of fixing the proportion and type of thrust bearing best employed, and of the general soundnew of the mounting as a piece of engineering. The earliest type of mounting employed in the application of Fio. 16a. worm ge'ar to the original Lanchester OBS is shown in Figs. 16,*16a, and 17. Hero it will be noted that the ball bearings are not of the modern type, the design dating back to a time when such bearin@ were not a s tandard id or a marketed commodity; two double bearings of the bicycle cup and cone type are arranged a t opposite ends of the worm, the whole combination being symmetrical. The cups were made adjustable by housing them within an internally screwed sleeve piece, and the adjustment was fixed by a key or cotter engaging with one of twenty-four notches cut in the periphery of each cup, Fig. 16a. The pitch of the thread was twelve per inch, so that the design gave a capacity of adjustment to within approximately three and a half one-thousandths of an inch, which 104 THE IXSTITUTLON O F AUTOMOBlLE ENGINEERS. was found to give satisfactory results in practice. Here we stumble against one of the misconceptions which are current with regard to the Hindley type of gear; it has often been represented that the accuracy of alinement of the worm requires to be true to within a thousandth of an inch of gedmetrical accuracy: 'from the sucmss of the arrangement described, it is clear that no such degree of accuracy is essential. It will be noted in the bearing in question that (as in the IWW of the old bicycle ball bearing) there is no separate function of cylinder bearing and thrust, and without doubt from a modern standpoint the type of bearing shown in Figs. 16 and 16a would be considered lacking in durability. No trouble was experienced from expansion (due to temperature) as between the two thrust bearings, and i t is fair to regard the casing, as indeed the whole of the parts, as sdliciently elastic to take up any small temperature difference. It is possible that at times one thrust bearing is called upon to sustain more thrust and at other times less than its fellow, but there has been no actual evidence of this taking place. The worm wheel bearings shown in Fig. 17 are roller bearings of the cheese roller type without cage of any kind. These are in fact the bearings on which the balance gear box is WORM QEAR A N D W O R M OEAR MOUNTING. 105 mounted, and the worm wheel itself forms the central seotion of the balance gear box. The thrusts were of a specially designed type, and consisted of balls in a flat cage between two perfectly flat ground and hardened thrust washem, the balls being arranged in a spiral manner,* Fig. 18. The object of this arrangement, i.e., the spiral distribution of the balls, is that each ball ma3 bear on a different part of the flattened surface, so distributing the wear; a further advantage is, that if the balls vary amongst themselves aa to diameter, as is commonly the caae, each ball will form its own race and will soon be taking its due proportion od the 10ad-h markings on the thrust r a m frequently gave evi- denoe of this action. The degree of inaccuracy amongst balls of nominally the same diameter is cowonly less than one tenthouculndth of an inch. This form of bearing waa in every, way successful and satisfactory; that it has since been dropped is due to the fact that excellent thrust bearings have now been placed on the market by specialised manufacturers. In the modern worm mounting, the type of bearing given in Fig. 16 haa been long since abandoned, and to-day it is the invariable practice to separate the functions of radial load and thrust and provide for each by a bearing speually designed Patent 17,032 of 1901. 106 THE INSTITUTION OF AUTOMOBILE ENGINEERS. for khe,purpose. Thus in%igs. 19a, 19b, 20 and 23, a roller bearing is employed independent of the thrust; in some cases this bearing is of the long-roller type, in others (Fig. 23) the \u201ccheese\u201d type iS adopted. In Figs. 24 and 26 and those which follow, it will be seen that the radial bearing also in common use is the symmetrical type of ball bearing 89 now to be obtained from several firms, such m the Hoffmann, Skefko, Duplex, etc., and the h s t is independently carried. It is worthy of note that in the modern mountings, the thrust bearing, a double thrust, is almost invariably fitted at ope end.* Objection has been taken to this arrangement on the ground that any inequality of expansion between the worm shaft and the casing will throw the worm out of centre, in other words, the objection is baaed on the faat that the arrangement is unsymmetrical. There are two answers to this. Firstly, the temperature difference is a mere \u201cbagatelle\u201d; thus the whole range of temperatures between the hotteat and coolest parts of the gear box is included between an * An exception to the practice of employing separate radial and thrust bearingi L to be found in cases where the American type of conical roller bearin@: has been adopted. WORM (;EAR AND WORM GEAR MOUNTING. 107 e tmqher ia temperature, say, 20\" C. and an upper extreme of about 100' 0.; speaking generally, the difference between one part and another does not exceed 40\" C. or 50\" C. At the worst, calculation gives the relative displacement of the worm oentre line and the wheel centre line due to the cause stated es not exceeding two or three thousandths of an inch. In practice it is doubtful whether it is ever aa great as this: in any w e it has not been found to be detrimental. Secondly, if , as is the only alternative, the thrust and oounterthrust be arranged at opposite ends of the worm shaft, there will be a much bigger expansion difference to take up between thrust and counterthrust, probably twice aa great a~ that now between worm and thrust bearing. This expansion might have a detrimental effect on the thrust bearings and ultimately lead to their disintegration. The failure of a thrust bearing may be regarded as perhaps the worst \"accident\" which can happen to a worm gear. The author will now dascribe in detail a few of the later and more succassful types of worm mounting, and some of those which am historically the more important. The &st series whioh will be taken will be in continuation of Figs. 16 and 19, showing the historical development of worm mounting in the practice of the Lanchester Company. It will be noted on comparison of the figures given that there are certain featuras of the Lamhestor mounting which have survived from the earliest designs, notably 108 T H E IN ST IT U T IO N O F A U T O M O B I L E E N Q IN E E R S. 0 cy 8 4 WORM QEAR AND WORM GEAR MOUNTING. 109 the splined shaft on which the worm assemblage is mounted, also the method of building in the worm wheel as part of the balance gear box, and in providing for the housing in the worm wheel meting itself of the cross pin or pins on which the balance gear bevels are mounted. In this arrangement, which is common to the whole of the series, it will be seen that the drire from the bevel wheel is taken directly on to the balance pinions, and the covers of the balance gear box are not used to convey torque but only the thrust and other forces by which the wheel is held in alinement. It will be noted that the thrust bearings serving the balance gear box take not only the worm thrusts but also the axle thrusts. There is a bronze pad fitted between the axle ends by which the thrust is conveyed from one axle to the other and thence to the thrust bearing, Fig. 21. Another incidental feature which may benoted is the fact that there axe four balance pinions in the differential gear box, each pair mounted on a transverse pin; the figures show clearly the means taken in the design of these oross pins to permit them to clear each other and to clear the axle ends and thrust pad. So far as the worm gear mounting is concerned, these are mere incidents, but the method by which the drive is conveyed from the worm wheel to the balance pinions is essentially of interat . Coming back now to the more directly important points, we may, with reference to Fig. 19a, call attention to the first advance in worm mounting after the type shown in Fig. 16. In this we see that roller bearings brought well up to the neck of the worm have been substituted for the bicycle type of bearing in the previous figure, and a double ball thrust between flat parallel races has been applied at the tail end of the worm shaft. This. design, again, was before the period in which ball or roller bearings could be purchased from specialised makers, and the bearings were made in every detail at the Lanchaster Company\u2019s works. It will be seen that.the thrust bearing in this design is very compact, but from the modern point of view and with present day loads and speeds it would not be considered adequata. Owing to the incline of the worm shaft and the importance of ground clearance, the tail position is at a disadvantage compared to the driving end of the worm shaft in the matter of permissible diameter, hence, when we pass to a later design, Fig. 19b, in which the bearings (both cylinder and thrust) are far more robust, the thrust is fitted at the neck or forward end. I n Fig. 20 (early 110 THE INSTITUTION OF AUTOMOBI1,E ENGINEERS. 20 h.p.), we find that the ball thrust bearing has again been arranged at the forward end of the worm, and in this dasign an innovation was tried experimentally to do away with the ball counterthrust and employ a series of thrust washers, the efficiency clearly being a matter of no importance when the brake is being employed. A notable feature in this dasign is the very large diameter of the thrust balls. Fig. 21 gives the corresponding FIO. 21. section through the worm wheel axis. Here we see the spiral typo of thrust bearing with flat races still holding its own. A feature which is worthy of mention in many of thase early mountings is the employment of the \u201cchetxie\u201d type of roller bearing, that is to say, a type in which the length and diameters of the rollers are about equal. This is a type of bearing which the author developed in the experimental period of car building, WOHM QEAR AND WOKM GEAR MOUNTINCf. 111 and which w a ~ used in the Gold Medal phaeton built in 1897-8. The employment of this type of bearing WM extended considerably in the 10-12 design in 1900, where it W&B used throughout the re= axle and parts of the oountershaft. It is only within the last few y e m that bearings of this pattern have been taken up and introduoed by the Hoffmann Company and others. There is a differenoe in practice inasmuch as the bearings marketed at the present day appear to be all fitted with cages, whereas in the FIU. 22. author\u2019s experience a cage is absolutely unnecessary in bearinp of the \u201ccheese\u201d roller type. In any , m e the guiding of the rollers is done from the ends, and this is really the definite distinction between the ordinaxy roller bearing and that of the \u201ccheese\u201d type, in the former the roller being guided from its cylindrical surfacw, the cage being a necessity. Generally, speaking, it has been the author\u2019s practice to so design the bearing that the rollers once in position could not fall ou t ; thus, in the axle bearings shown in Fig. 17, the diameters of rollers and 112 T H E IN ST IT U T IO N O F A U T O M O B I L E E N Q IK E E R S. WORM QEAH AND WORM GEAR MOUNTING. 11 3 races were such that the axle or central race could be removed and the rollers could not be displaced. The clearance was so small that the rollers would lock before they could come free, ,as illustrated diagrammatically in Fig. 22. On the worm bearings we again see the cheese roller bearing of the cagele~s type employed, and a double thrust bearing on the tail end of the shaft. The whole outline of the worm housing, however, hits been made very clean and smooth externally. The corresponding axle mounting is given in Fig. 21. Here it may be seen that on the axle bearing the ball has in this case replaced the roller. It may almost appear, in looking at these changes, that in some cases, in which the change goes from one arrangement to another, and then back again at a later data, there is certain evidence of infirmity of purpose. As a matter of fact, changes are frequently due to conditions which are temporary, and often two designs are so nearly equal in merit that whether one or the other be adopted is purely a matter of convenience. A great deal must depend. upon whether the designer has a completely free hand or whether he is required to make use of standard components. I t will be noted that amongst the various changes the practice of the Lanchester Company has slways been to place the worm shaft below the axle. One knotty point has existed throughout almost the whole history of gear box mounting, and that is the manner in which alinement is to be secured. There are four methods open: firstly, the parts may be made with sufficient mechanical exactitude to ensure perfect interchangeability and alinement within the necessary degree of accuracy. Secondly, a screw or other variable adjustment may be provided by which the necessary alinement may be secured in spite of individual variation in the parts. Thirdly, the method of using pen steel washers or \"shims \" may be adopted. Fourthly, an accommodation piece may be employed. In the earliest type of mounting (already discussed, Fig. 16)) the method of screw adjustnient was employed, and up to a certain point was found satisfactory. I t had the wealtness, however, that, if the mountings were taken down, either the parts would have to be carefully marked, which might be forgotten, or in re-assembling an experienced hand would have to be employed,-who might not always be available. In brief, the screw adjusted mounting is not fool-proof.\" In departing A still later type of mounting is given in Fig. 23. LANCHES'l'ER. H 114 THE INSTITUTION OF AUTOMOBILE ENQINEERS. from this the author endeavoured to attain perfection and prescribed limits to the components and methods of gauging by which completo interchangeability waa secured. This ideal, however, F I ~ . 24. is cxtremely difficult to get carried out. The number of parts in the \u201cmechanical circuit\u201d is great, and, in ordar to avoid excessive variation in the aggregate, the individual liiiiits require to be unusually fine. So long as all the components are made WORM QEAR AND WORM GEAR MOUNTING. 11s in the same works a s the car the thing can be done, and it has been successfully done by the Lanchester Company. The d i5culty, however, arises when it is desired to increase the output and bearings have to be purchased from firms who specialise in such commodities; the degree of accuracy to which they will guarantee to work is totally inadequate, in .other words, bearing makers will not guarantee to work to thickness limits or width limits less than five one-thousandths of an inch, and if such limits were tolerated the total inaccuracy in the case of a worm mounting would amount to rn many hundredths of an inch as it should be thousandths. * The author has never found it cheaper to work to a low degree of accuracy than to work to a high degree of accuracy,; in other words, a thrust bearing can be produced which from face to face does not differ by more than a thousandth just as cheaply as i t can be produced to within two or three one-thousandths. Whatever difference of Gost there may be is more than compensated for by the advantage of interchangeability. I n other words, the actual production of a part accurately to dimensions, that is to say, within fine limits, may be slightly greater, but in any complex piece of machinery the saving in ms't of assemblage will pay the bill many times over. The above is no mere ideal or unsupported opinion, i t is based on hard experience. Some years ago, in designing certain mechanism (which need not be specified) every clearance dimension and tolerance dimension was set personally by the author'8 own hands, and these were worked to for a considerable time with satisfactory results. A new works manager, who did not believe in working to fine limits, reported that the limits were unduly fastidious and that money could be saved by relaxing the limits and so avoid having to scrap parts. The managing director consented and the scheme was tried. A slight and questionable reduction resulted in the cost of manufacturing components, but the increased cost of assembling and testing, and the cost of rectifying complaints, etc. became so great that the initial saving was swallowed up many times over. Within twelve months the scheme was abandoned and the old fine tolerances were rmtored, the expense of twice altering the gauges, etc. being a dead loss apart from the disastrous results of the experiment. The Hoff mann limit on the width in a standard ball bearing is +0*006, a total variation of 0.01 in. or mm. - H 2 116 THE INSTITUTION OF AUTOMOBILE ENQINEERS. The author thinks he could go further and say that he has never made an endeavour to do anything better than proviously, without finding that when it is being done better it is also being done cheaper. Thus, the \u201csplined shaft\u201d was looked a t by some as a piece of fantastic extravagance when first introduced, but it showed itself to be a money saver from the outset; it is far cheaper to cut a splined shaft and drift the hole to correspond, than it is to cut a key way and make and fit a key; also the job is incomparably better engineering when done. I t is, perhaps, the more legitimate to cite this example since it was in connection with worm mountings that the splined shaft was first introduced into motor car practice; the worm shaft of the 10-12 h.p. Lanchaster car, Fig. 16, also the gear box, were, the author believes, the first applications of the splined shaft in the history of automobile engineering. * Returning to the main point under discusqion, it has been stated that though commercially possible, and probably advantageous, to fir the limits of the various components to secure perfect interchangeability in a worm gear mounting, it can only be done provided that the whole of the parts are made by the builders; a t least in cases such as ball or roller bearings the offending dimensions must be rectified after they have been received from the manufacturer. There are commonly some eight parts or thereabouts of which the tolerance differences accumulate, and to attain perfect interchangeability the whole sum of theset must be kept down to within four or five one-thousandths of an inch. Admittedly the individual limits are fine. Owing to the difficulty of obtaining the necessary interchangeability egpecially where ball boarings, etc. were ordered from outside sources, the Lanchester Company have from time to time resorted to an accommodation piecc, or havc made use of \u201cshims\u201d in order to secure the nocessary accuracy of alinement. There is more to be said in the case of a worm gear mounting for this practice than might appear to the idealist; it is, for example, admitted that the various components, thrust bearings, etc. are liable to a certain amount of wear; occasionally, also, the whole assemblage will be found to have developed internal sloggar, in which case the components may undergo considerable \u2018 I punishment \u201d and additional inaccu- , * In f l ~ p s . 19a, 19b. 20, 23, etr., Pplined tihaftR are emploved in every case, In FiFs. 21 and 24 also the axle end. bnt the Pplines me oot shown in detail. (althouuh not Nhlwn W R such) are aplined for the fitting of the bevel wheels. f Compare Appendu. WORM GlEAR AND WOKM GEAR MOUXTING. 117 racy is introduced. Under these conditions tho use of sh\u2019ims in the repair shop is fully justified, and a very good job indeed can \u2019be made if the points at which the shims are inserted are such as to present a sufficient area, and i f the shims themselvea axe of pen steel or other suitable hard grade of material. If this be not the case, there is always the danger of the shimma being spun out or hammered out, and eventually disintegrating, in which case the parts may get Ioose in the gear box. There is also the fourth expedient above given: the accommodatioii piece. In all interchangeable work in mechanical engineering a point may ultimately be reached when the accumulation of the tolerances of the individual components results in the individual limits having to be cut down to a point below anything which may be considered reasonable. I t then becomes a question of judgment for the designer (as in the case of the worm gear under discussion) how the difficulty is to be met: one method is that of the accommodation piece. Thus one piece in the whole \u201cmechanical circuit\u201d is left to be fitted, or is made in several different standards of thickness. This is f a r better practice than to have a pretended interchangeability which does not really exist in which the accumulated tolerances do not come within the aggregate limit, and which in the assembling of a machine has to depend upon the selection of compatible components. Thus, on many pieces of mechanism at present being manufactured for the Government there are limik specified on the aggregate assemblages which are inconsistent with the limits pormitted on the individual components, so that a manufacturer may make his components within the limits specified and yet he may not have a single assemblage which will go together. I t is frequently true that it would be far easier to put finer limits on the individual components and devise means of working to them, but obviously, as already stated, there is a limit to what is commercially possible. When this limit is reached the alternative to the very unsatisfactory state of things above described is to make one of the components an accommodation piece, and either admit that part as a fitter\u2019s job, that is to say, allow it to be filed or otherwise adapted to the rest of the assemblage, or else to make that particular part in sufficient variety and confine the selecting to that one particular component. In the Appendix is given an oxainple of a case where the number of dimensions in the mechanical circuit is about normal for a 118 THE INSTITUTION OF AUTOMOBILE ENGINEERS. worm transmission, and examples of suitable component dirnensions are given in detail as figured on an interchangeable basis. I n the worst or extreme cases given by theee dimensions the difference amounts to 0.01 in. in the worm and wheel location ; this may bo taken as within the limits of good practice. I t is clear from this example that a very high degree of accuracy in manufacture is necessary in order to obtain the desired result. The difficulty mentioned in the case of \u201cshims,\u201d namely, that they aro liable to be spun or beaten out, is a difficulty met with more broadly and in a more general way in worm gear mountings. The parts intervening between the thrust and the worm appear in practice to need to be able to stand a lot of \u201cpunishment,\u201d and it is most important that no backlash shall exist. The consolidation of the worm shaft assemblage is usually provided for by pulling the whole string of components, namely, worm, distance piece, bearing ring, thrust washer, etc. thoroughly solid by a nut of ample proportions, as may\u2019be seen from the various figures. In some cases this nut has been locked by means of a, caulking plate, in other cases the customary split cotter has been employed. Where the latter practice is adopted it is important that the nut shall be pulled thoroughly home before the hole is drilled for the split cotter, and even under these conditions there are certain objections to locking in this way. Owing to the trouble which has been found to develop if any initial backlash once makes its appearance, it has been the author\u2019s practice for some time to specify that all the components forming this compression assemblage shall be hardened, either being made of a high carbon steel or case-hardened according to circumstances. When this precaution is taken, and when the abutting areas are made sufficient, all trouble from the cause stated has been found b Tho experience of the Daimler Company, though dating from more recent time, is considerably wider than that of the Lanchevter firm, inasmuch as the range of sizes and standards as defined by the different centres and ratios of gear is far greater; the applications range from the lighter types of pleasure vehicles, both petrol and electric, to the heaviest type of motor lorry, namely, the five-ton vehicle. The whole range of the Daimler-Lanchester worm gear standards is laid out diagrammatically to scale in Fig. 25.* The different The LaWhebhr Compang\u2019a standards include types A and B only. and are cease. Type A B *Load at 1 ton,per 24 1.5 nq. in. TOT# In. Ton In. I i C D F a 4.2 1.1 1-52 8-9 Ton In. Ton In. Ton In. Ton ha. i l J ! H J K L 0 P 0.7 8.4 1.75 1.17 12.8 5.7 Ton In. Ton In. Ton In. Ton In. 2bn ln. Tm In. L-, -- LH ButhHands 9 a t Centres - 1 - 5.44 LEE ,.,,),: 4-33 w Pi FIQ. 25. * These torque values refer to the wheel element, and are bmed on a 1c.ading of one tcn per tq. in. projected tooth area. 1 7.36 RH They represent roughly the ordinary caondition of running on the high gear. The maximum 8afe load for thort periods may be taken as four or five times peat . 120 THE INSTITUTION O F AUTOMOBILE ENQINEERB. standards of blank are designated by the capital letters A, B, C, etc., in the order in which they were initially established. Types A, B, C, F, and IC have been produced for private pleasure cam,. etc. Types D and L more particularly for electrical vehiclea (supplied mainly to the U.S.A.). Types H, J, and 0 for commercial heavy vehicles, and type G for particular application to (stationary) power transmission. Thus, in greater detail, type B, 6 in. or 152 mm. centres, is that used almost universally in full weight touring cars, limousines, etc.* Type K, 137 mm. or 5T7F in. centres, for cars of, say, identical with those given except that the Lancheater Company\u2019a list does not indude the 9/32 ratio type B, but includes a 6/36 ratio in type A. In addition to this the Lonchexter Company\u2019s standrirds in the B type include left-handed cut.ters only, but their list includes a oertain number of right-handed cuttera in type A. In all cases it is the weight of the car rather than the h.p. which k of importance. Up to 60 cwt. gross or even over. WORM QEAH A N D WORM OEAR\u2019MOUNTING. 12 I 20 \u201clegal\u201d* h.p., weight not exceeding 32 cwt. gross. Type F , 120 mm. or 42 in. centras, for cars of, say, 16 \u201clegal\u201d h.p., not exceeding 28 cwt. gross. The typas H and J, 72 in. or 196 mm. centres, are for three-ton lorrim, \u2018bus chassis and the like. Type 0, 9 in. or 228 mm. centres, is for the heaviest road vehicle at present in ordinary commercial use, namely, the five-ton lorry. A typical mounting for the A and B standards of gear is illustrated in Figs. 26 and 27. There is little to be noted here except the self-adjusting spherical thrust bearings which prevent; FIQ. 27. undue or unevenly distributed stresses on the thrust bearings as plausibly due to any slight \u201cwhip \u201d or spring of the mounting or want of alinement. Contrary to the Lancliester Conipany\u2019e practice, also, it may be noted that the road wheel thrusts are taken independently of the differential box mounting. Figs. 28 and 29 illustrate the mounting adopted in the 20 h.p. Daimler chassis used to a considerable extent for Staff, Red Cross and other purposes at the Front. I n this mounting the worm iS * The \u201c legal \u201d h.p. i H nieasured by the R. A C. rating 0.4 D2n. 122 THE INSTITUTlON O F AUTOMOBILE ENQINEEKS. on top, and the worm box is cast integral with the main portion of the gear box. An interesting feature in this mounting is the fact that the thrust is placed adjacent to the worm itself, and the bearing is placed beyond. This inversion of the usual order results in a bigger bending moment on the worm shaft, but there is ample strength to carry this. The advantage lies in the f:rd FIQ. 28. that as designed there are, including the worm, only five parts in the mechanical circuit, if we regard the variation in ball diameter as negligible. These are the worm, the thrust half bush, the thrust live ring, the thrust Exed ring, and, finally, the gear box casting. Thus, the total variation in the location of the worm is the sum of five tolerances, or, as already expressed, there are five elements in the mechanical circuit. This may bc considered a WORM GEAR AND WORM GEAR MOUNTING. 123 distinct advance in worm gear mounting as a step to securing interchangeability. Figs. 30 and 31 show the G standard mounted as a fixed transmission-as such i t has been applied for the driving of air comprwiore, etc. and other slow running plant from electro-motors. It is good for 150 b.h.p. at 1,000 revs. per minute of the worm shaft. It may be noted that thO Daimler Company\u2019s standard types for commercial vehicles (lorries, buses, and the like) are of a heavier type, and, generally spcaking, of considerably lower gear ratio than thoso for pleasure vehicles, the differcnce being mainly duo to tho slower speeds commonly in demand and the larger diameter of the road wheels necessary for the duties in question, coupled with tho fact that the engine speed is not proportionately lower. It may, be said that in the application of worm gear to com- 124 T H E IN ST IT V IIO S O F A U T O M O B IL E B N O lN E B llS . WORM QEAR AND WORM GEAR MOUNTING. 125 mercial vehiclw the conditions are on the whole more exacting than in the touring car. The driving mechanism is rarely 80 refined, and the driver himself is not usually 80 fastidious. Beyond this, the loads are heavier, the tyres less yielding, the suspension. etiffer, and generally all the conditions which tend to \u201cliustle\u201d the gear exist in a more aggravated form. In consequence of this, it might be supposed that all the precautions which have been enumerated as tending to secure solidity of the worm shaft essemblage in the pleasure car will be at least aa important in FIO. 32. the heavy commercial vehicle: experience has fully justified this anticipation. It is absolutely necessary that the compression park ~d thrust surfaces between the various components of the assemblage, namely, worm, spacing collar, roller race, thrust washer, etc., should be of ample area and on no account must they be left soft. As exemplifying points of good and bad design in this respect a comparison may be made between Figs. 32 and 33. In Fig. 32 a poor design of worm assemblage is illustrated, in which the defects are intentionally exaggerated; in Fig. 33 a 126 THE INSTITUTlON OF AUTOMOBILE ENGINEER& good design is given, showing the proportions and precautions necessary to ensure BUCCBSS. Referring to Fig. 32, it will be seen that the thrust surface3 between the spacing pieces at a, b, c, d, etc. axe of insufficient area. So far as concerns the taking of the necessary thrust reaction, they might with justice be regarded 8~ more than ample; for example, at the point d the area of the contact faces is more than a square inch, and may be taken as safe in compression for a force of ten tons-the actual maximum FIQ. 33. load is not more than one-third or one-fourth of that amount. A8 a mattar of experience, however, no such design will stand up, the faces in contact are found to undergo punishment and sooner or later backlash will develop, and the failure of the mounting follows in a very short time. The author has actually seen 3 cam of this kind in which the one part has eaten into the other a matter of three or four millimetree and the worm has had to adapt itself to an axial displacement of that magnitude; this can hardly be described as fair or proper trwtment. When asked how WORM GEAR AND WORM GEAR MOUNTING. 127 to account for such failurw taking place, considering the cornparatively light t h m t load per square inch carried by the faces in contact, it is fair to say that casea of even admittedly defective design do eometimw stand up; a certain percentage of output will not bo reported as giving trouble. The truth probably is that the failure occurs through a little initial \u201cslogger\u201d oz backlash creeping in, either from careless mounting, due to insufficient initial pressure being put on by the retaining nut,* FIQ. 34. or as oonsequent upon some slight defect in material or by bad or rough handling at some time or another. What has to be remembered is that a mounting which is not open to inspection (without virtually dismounting an axle) must be so designed and constructed as to be reliable even under the most unfavourable conditions; the need for large face contacts and hardened surfacea * The inclusion of a amall quantity of swarf or dirt might be the explanation in some cams."
        ]
    },
    {
        "image_filename": "designv11_36_0002538_imotp.1896.19529-Figure1-1.png",
        "original_path": "designv11-36/openalex_figure/designv11_36_0002538_imotp.1896.19529-Figure1-1.png",
        "caption": "Fig. 1. less than C A and the piston",
        "texts": [],
        "surrounding_texts": [
            "papers.] UNWIN ON CRANK ANGLE FOR GREATEST PISTON VELOCITY. 363\n(Papep No. 2976)\n\u2018\u2018 Determination of Crank Angle for Greatest Piston Velocity.\u201d\nBy WILLLAM CAWTHORXE UNWIX, BSc., F.R.S.\nIF C A, Fig. l , is a crank and A B a connecting-rod, and C D is perpendicular to the line of stroke, then, as is well known,\nVelocity of piston C D Velocity of crank-pin - C A\u2019 ~- -\nFor nearly all the revolution C D is\nvelocity is less than the crank-pin velocity, but for two small parts of the revolution, when the direction of the connecting-rod is nearly tangential to the crank-pin circle, C D is greater than C A, and the piston velocity is greater than the crank-pin velocity.\nIt has been usual to assume that approximately the piston velocity is greatest when the crank and connecting-rod are a t right angles. Let 1 be the length of connecting-rod, r the crank\nDownloaded by [ Heriot-Watt University Library] on [24/09/16]. Copyright \u00a9 ICE Publishing, all rights reserved.",
            "364 UNWIN ON CRANK ANGLE FOR GREATEST PISTON VELOCITY.[Selectd\nradius, and let - = W. The crank angle p, when the crank and\nconnecting-rod are at right angles, is given by the relation-\nt a n p = n . . . . . (1)\nl r\nand this determines approximately the angle for which the piston velocity is greatest.\nThe determination of the exact value of p for which the piston velocity is greatest is known to present some difficulty, and, so far as the Author is aware, the first exact solution has been found by Professor Hi1l.l The same result, however, may be reached by a different and, in some respects, an easier path.\nIn Fig. 2, let C A be the crank, and A B the connecting-rod as before. Produce A B to intersect a perpendicular to the line of stroke in D; draw D E perpendicular to D B, join E A, and draw D F parallel to A E, and A G parallel to D C. Let C A = r, A B = 1, C B = s ; l e t - = n ; a n d l e t a n g l e A C B = P , A B C = a . l r\nIt has been shown by Rittershaus that the piston acceleration is proportional to F E - E C, the construction being now well known. The piston velocity will be a maximum when the acceleration is zero, and therefore at that position of the crank which makes F E = E C.\nMinutes of Proceedings Inst. C.E , vol. csxiv. p. 390. * \u201cMachine Design,\u201d Part 11, p. 72; Civilingenieur, xxv.\u2019s. 461:; xxvii. S. 283.\nDownloaded by [ Heriot-Watt University Library] on [24/09/16]. Copyright \u00a9 ICE Publishing, all rights reserved."
        ]
    },
    {
        "image_filename": "designv11_36_0002549_jiee-1.1917.0030-Figure5-1.png",
        "original_path": "designv11-36/openalex_figure/designv11_36_0002549_jiee-1.1917.0030-Figure5-1.png",
        "caption": "FIG. 5.",
        "texts": [
            " These waves can only occur in a t)rpe of winding in which the current in any bar is solely determined by the electromotive force in the same bar, and not hy the electromotive force in a series of bars. The only type which fulfils this condition is the squirrel-cage type. Hence the type of machine with which we shall deal will be one carrying a squirrel-cage winding on one member and on the other merely a primary winding concentrated at one point in the zone which we are studying, or at a limited number of points in the whole machine. Such a machine is shown in Fig. 5. It consists of an ordinary squirrel-cage rotor and a primary member wound ring-wise around the core and concentrated in a single slot. The diameter of the apparatus is assumed to be sufficiently great to enable the disturbances on the positive side of the primary member to die away before passing sufficiently far around the machine to meet those on the negative side. In the following sections a thorough study is made of such an apparatus and the influence of resistance, selfinduction, and capacity in the rotor is worked out, as well as that of various secondary windings on the stator",
            " By way of an example we may elucidate the application of such a diagram by considering how with its aid we may calculate the wave motion due to a single ring-wound primary co-operating with a short-circuited secondary and wound on a core of such diameter and constants that the wave motions in both directions die away before they interfere with one another. First of all from the dimensions of the apparatus, the cross-section of bars, core length, and air-gap we calculate the two constants r2 and ft, and thence p fi/r3. These known we proceed to plot the two curves mentioned above. We have next to determine the scale to which Y P, represents the synchronous speed of the wave v0 \u2014\u2014pl\u00bbt- Since OY = w, we can readily calculate :c for any value of O P and the corresponding length of Y P, and so determine the scale. If we suppose the rotor (Fig. 5) to revolve in a clockwise direction, then on the right of the primary it will be moving away from it and on the left towards it. Hence O P corresponding to v positive, or moving with the wave, is correct for the disturbance on the right, and O Pa {v negative) for that on the left. The first thing which we notice is that the ordinate m determining the speed of the wave is the same in both cases, and hence that the wave flows away from the primary coil at the same speed in both directions. But the decrements vary very much, being, as stated above, proportional to the slip between the wave and the rotor, and therefore being very great when 468 CREEDY: ELECTRIC WAVE PHENOMENA v is negative and very small when it is positive"
        ],
        "surrounding_texts": []
    },
    {
        "image_filename": "designv11_36_0002616_piae_proc_1916_011_012_02-Figure42-1.png",
        "original_path": "designv11-36/openalex_figure/designv11_36_0002616_piae_proc_1916_011_012_02-Figure42-1.png",
        "caption": "FIG. 42.",
        "texts": [
            " For any eet of gear between wide limits of load and speed the angle of friction is in fact almost constant, quite near enough so for the purposes of the foundation theory. On this assumption (i.e., angle of frictionconstant), it is then easy to demonstrate that the efficiency will be constant for all variations of torque and spaed, also that the efficiency is independent of the diameters of the g e m provided that the pitch angle of the teeth is the same. The approximate truth of this as an experimentally established fact is the justification of the method, and this has been fully established by the N. P. L. task and report. In Fig. 1 i reproduced Fig. 42 from the previous paper, in which a comparison is given between one of the testa from the N. P. L. report and one of the so-called tests of a parallel worm oited by Mr. Kerr-Thomm, namely, from a paper by Profassor Kennereon. Here, B, we eee the N. P. L. tast of a Daimler-Lanchesbr worm in whioh from about 27 h.p. to 62 h.p. the efficiency dow not vary more than one-third of 1 per cent, whereas in the plottings from Pmfeseor KeMerson\u2019s paper, A, there is a curve which WORM QEAR AND WORM GEAR MOUNTING",
            " 13; oircuit the greater will be the accumulated effect of the tolerance (allowed to the individual parta in manufacture) on the ultimate clearance value. In some caaw, as where there is a clearance between every part, with its oil film, such aa a number of sliding bars housed parallel to one another between two retaining jaws, the deaigner\u2019e object to avoid trouble by reducing the number of park in the \u201cmechanical circuit\u201d to the minimum. Such a case is typically illustrated in a worm gear mounting shown in Fig. 42; in this case thero are no less than eight parts i n the mechanical circuit, and there is only one clearance dimension. Tho eight parts are labelled a, b, c, d, e, f , g, and h, and the dimension in which the clearanca is felt may be regarded as that giwn by the letter S. This dimension S is affected by the accumulated tolerance of the eight parts a, b, c, d, e, f , g, h . . Under these conditions the permissible variations in S, divided by the ,Lumber of components in the circuit, defines the degree of accuracy of manufacture or tolerance necessary for the individual components"
        ],
        "surrounding_texts": []
    },
    {
        "image_filename": "designv11_36_0002616_piae_proc_1916_011_012_02-Figure58-1.png",
        "original_path": "designv11-36/openalex_figure/designv11_36_0002616_piae_proc_1916_011_012_02-Figure58-1.png",
        "caption": "FIG. 58.",
        "texts": [],
        "surrounding_texts": [
            "on which the author is insisting is thus based on experience of what is rather than on calculation as to what might or should be. A further defect in the design shown in Fig. 32 is the thin distance tube g on which the double thrust bearing is mounted; it has boen stated that the end nut h must be thoroughly tightened in order to secure the assemblage; if, as drawn, too muoh force were applied, the tubular spacing piece would be liable to be crushed and unknown forces would be brought to bear on the thrust bearing itself, with the imminent risk of its f a i l u r e involving tho usual undesirable consequences. On referring to Fig. 33 i t will be seen how much greater is the area of the faces provided, and generally what a far more secure job has been made of the worm location. Instead of the worm itself being held on one portion of a shaft and the thrust. being held on another portion of the shaft, so that if either of two fixings come slack the worm develops backlash, we now see the worm and its thrust all held up solid on one section of the worm shaft, so that its location depends upon one fixing in place of two. Also the end face of the worm by which the brake thrust is taken is of increased diameter and bears direct on a face formed on the shaft itself. In Fig. 33, the system (to which reference has previously been made) of an accommodation piece is employed to overcome the difficultiw of interchangeability, the piece in question, taking the form of a sleeve on which the double thrust is mvunted; the accommodation pieoe is more precisely formed by the flange of this sleeve, which constitutes a spacing piece between the roller bearing inner race and the first thrust washer, and its thickness is varied to correct for the combined inaccuracy of $he width of the roller race and the thrust bearing dimension. I t is, as before remarked, one of the troubles with which the constructor is faced that the makersof roller and ball bearings will not go to the trouble of workingwithindecently fine limits; it har been reported that in the particular combination of roller and ball thrust given in Fig. 33 the variation between one samplu and another is commonly (on an average) as much as 0'25 mm.* Personally, the author is strongly in favour of dismantling all bearings aa they come from the makers and rectifying their important dimensions so as to secure complete interclinngeability ; however, neither the Lanchester Company nor In an exoeptional case the inaccuracy was no less than ona whole millimeter ! WORM GEAR A N D WORM G E A R MOUNTING. 129 tho Baimlor Company has yet taken so drastic a course: tho systrin of the accommodation piece has been taken as tho simplwt way out of the difficulty. No accommodation piece is wanted to correct for inexactitude on the part of the motor car manufacturer; this is evidenced from the fact that the present procedure is that the bearings are taken to the view room and are \" married \" in set,;, one roller bearing and one ball thrust, and the accommodation piece, the sleeve, is ground to whatever thickness is required in i b flanged portion to bring the dimensions accurate; no -.- F I ~ . 35. FIG. 36. similar pairing or grouping of parts is needed in t.he case of those for which the autoiiiobile manufacturer is wholly responsible. It is quite clear from this that the attitude of the bearing manufacturer is quite preposterous, and we may look to his speedy reformation when the number of firms supplying ball and roller bearings have an output in excess of the demand; it is usually waste of time arguing with a man who has tl bigger market than he can fill. LANCUESTER. I 130 THE INSTITUTION OF AUTOMOBILE ENGINEERS. Another feature in which the makers of ball and roller bcarings havo much to learn before the goods in question cease to be a trouble to the designer is that of the radius which it is customary to put on the edges of the bearing races. This is too littlc, and results over and over again in a designer having to arrange an additional piece in his design in order to adapt the bearing to the shaft on which it is to be mounted. What is far more serious is tliat in many cases draughtsmen have been led to design shafts with comparatively sharp corners at collared portions in order to suit the bearing. I t mould be tho best course inechanically to pass the bearings through an extra process and appropriately increase the radius to suit the needs of tho shaft neck design, but there is always the danger that this might be neglected, especially in garage work where the bearing is, often enough, obtained direct from the manufacturer instead of through the car builder. This is one of the evils not so much felt in worm mountings (where more often than not the bearing is placed between two collars) as it is in other applications of the roller or ball bearing, but occasions frequently occur, and the point is one which merits attention. In Fig. 35 me have a b d l bearing a.3 commonly turned out with its radius of only 3/32 in.; the shaft neck to take this bearing would have to be almost sharp in the corner. The figuro shows this bearing accommodated by means of a collar or washer to a properly designed shaft neck. Fig. 36 illustrates what this bearing should be from the point of view of tho automobile designor. The author faiLs to see any reason why a liberal radius as illustrated should not be adopted by the manufacturers of bearings. In fully interchangcable work any additional piece in the mechanical circuit, as in Fig. 35, means a fining of the limit3 of manufacture with an all-round increaw in the cost of production.* Compare Appendix. WORM GEAR A N ) WORM G E A R MOUNTING. 131 APPENDIX. d THE worm assemblage is a typical example of a case in which to obtain perfect intorchangeability is difficult. The designer necds to make a careful study of the conditions. The production of manufactured articlas on an interchangeable basis is a modern development, and the whole subject, perhaps, has not had the systematic and careful study from the designer that is its due; there is a tendency to regard the interchangeability aa something apart from the design proper, and to leave the whole consideration of the subject to be undertaken subsequently to design in the tool and jig department. In the prasent Appendix the author is giving a brief outline of the system adopted in 1900 by the Lanchaster Company, the worm gear mounting being taken as a typical illustration. Firstly, a few words may be said on the broad theory of intorchangeable components in mechanism. Interchangeability depends fundamentally on the power of measurement. The appliances at the disposal of the engineer for the measurement of parts prescribe the limit of accuracy from a stated dimension that can be recognised, and accuracy in manufacture can never equal or transcend the pomor of measurement. Interchangeability is only possible so long as tho limits permissible to the individual components on account of the functions they have to perform is greater than the limit of measurement available; for example, i f a shaft to work in a given journal must be within 0.001 plus or minus of a given size, it is only possible to secure interchangeability EO far as the shaft is concerned i f we are able to gauge the part with certainty within 0*001. But the matter is not quite so simple as this; i n every case of working parts or fitting parts in a machine there are& least two parts which may be said to form a \u201cmechanical circuit\u201d: tlius, in a shaft bearing there is the shaft and the journal. Assuming the latter to be a bush, the essence of interchangeability is that the difference between the maximum permissible clearance and the minimum permissible clearance must be divided between the shaft tolerance and the bush tolerance. In other words, if the diametrical cleprance may be permitted to I 2 132 THE INSTITUTION OF AUTOMOBILE ENGINEERS. vary by 0.002, and the shaft tolerance be fixed at 0*002, the atmuracy of the bush would require to be absolute, and vice versa. Giving an equal tolerance to each of the components of the cirpuib, namely, 0.001, the diameter of the shaft, and equally the diameter of the bore of the bush, must be gauged within this limit. I t is important to have a perfectly clear conoeption of the difference betwten the meanings of the words clearance and tolernncp. The clearance between two fitting parts is the absolute differenoe in their dim,ension, and the range of variation in the clearance is due to tho combined magnitude of the individual tolerances.* I t is the custom in some factoriias to assign a \u201cparent\u201d dimension on any part, and to give a toleraiiue plus and minus. In other factorias the system has been adopted of writing in in full -.. ,==I+ - \u2018995 the maximum and minimum dimensions. The autbor\u2019a system, aa used at the Lanchaster factory, is to write either the minimum or the maximum as the parent dimension with an index beneath either plus or minus as the case may be, one-thousandth of an inch being taken M the unit. The three systems of dimensioning are given with respect to a nominally 1 in. shaft bearing in Figs. 3?a, b, and c respectively. I t will be noted that according to the author\u2019s system, Fig. 37c, the shaft bearing is figured with its maximum dimension and the tolerance with a minus sign, whereas the bush is figured as a minimum dimension as shown by the tolerance having a plus I 1-4 Cleurance has keen eomstimes defiued as the mazimum, and at others as the sign. 8i minimum clearance aa Lere given. WORM QEAR AND WORM QEAR MOUNTING. 133 The difference in these various methods of dimensioning might be regarded as merely a matter of notation or convention, but the author cannot but feel that there is more in it. Hia own conception of the problem of interchangeability is follows. If it were possible to make each part with perfect BCCUracy to a specified size or dimension, the clearance which would be assigned in the dimensioning of any two working par& would be the least clearance at which they would work satisfactorily; then, in the course of the life of the machine, the clearance would gradually increme until it reached some maximum value at which replacement becomas necessary. Now the author has always taken the view that tho tolerance on the component should be regarded as an initial amiunt of wear, an unfortunate necessity or imperfection, which is imposed by the fact of manufacture.. I t is on this basis that the system was adopted in which the parent dimension of each part corresponds to the closest perinissible fit. Nothing could be simpler as a matter of clear thinking than this basis; thus, in the case of the journal which we have 80 far used as an example, the designer says to himself, \" I want a clearance of (say) 0.002 in. ; it is the minimum which will give good working, also experience has shown that a bearing with a clearance of 0'008 in. should be replacod. I will allow as the greater limit for the clearance 134 THE INSTITUTION OF AUTOMOBILE ENGINEERS. 0'004 in., and will assign 0.001 in. of this to the tolerance of each of the two parts.\" In this case it would be fair m an approximate statement to say that the purchasar who happens to get a maximum bush and a minimum shaft together in the machine he buys, would socure only two-thirds the life which he mould sccure in tho case whelu thG part.icular parts are finished to the limits giveu by the parent dimension I t may be claimed, in favour of the author's systom, that the method of dimensioning a part with an intermodiate dimension and a plus and minus tolerance, Fig. 37a, is inferior, inasmuch as the dimension given serves no useful purpose; i t is not a useful dimension because i t does not appear on the gaugw by which the part is rejected or accepted a t all; it is not an ideal dimension WORM GEAR AND WORM QEAR NOUNTINO. 135 becauso, as before stated, it presupposes that a certain initial wear has taken place: in other words, if two parts giving the small& clearance possible by the limits will work, then these parts mill have the maximum durability and axe the most dasirable. Tho F~Q. 40. system in which maximum and minimum aro both specifiod on the drawing, Fig. 37b, is cumbersome. I t means a considerable addition t p tho amount of figuring to be inserted on the drawing, it does not give at a glance the degree of accuracy of the part requirod, and means considerable scratching out, etc. i f it is found necessary by experience to alter clearances. 136 T H E INSTlTU\u2018lIOX O F AUTOMOBILE ENQINEBRS. In producing an experimental or trial machine which it ia intended subsequently to standardise on an interchangeable manufacturing basis, i t is of the greatest possible advantage to etart by specifying clearances and tolerancw, just as i f the machine were being put at once into manufacture. The sucoess of the manuferttured article depends in some degree upon the limits being properly assigned, and the trial machine, whatever it may be, should be used incidentally to test proposed limits and secure information. For bcaring or wearing surfaces the minimum clearanom should be aimed at, and then where park have to be eased in order to obtain good working results, the subsequent gauging of theae parts will tell the designer w\u2019hat his minimum clearance (as determined by the parent dimensions) ought to be. I t is often convenient to put a trial machine in hand from drawings which have not been fully detailed, and to have the components made from drawings of group assemblages; it is one of the advantages of the author\u2019s system of tolerance notation that dimensions may be inserted on an assemblage drawing and the sign of tho tolerance shows oleaTly to which part the dimensiom relate. This also is a gre:it convenience to the designer in other cases, inasmuch as he may prepare an assemblage drawing and fill in any dimension wliich he deems to be of capital importanoe without the draughtmian who subsequently prepares the detaile being in any tlniibt as to whether a given dimension relates to the inner or outer part. In the elementary example it hns been assumed that the total tolerance, that is to say, the permissible clearance difference, L divided equally between the two controlling tolerances; this, however, i u obviously not necessary, i t is a matter where the experienoe and judgment of the designer will come in, as to whether a greater tolerance should be given to the one part or tho bther-it will depend largely upon whether it is easior to get accuracy in the manufacture of the one or the other component. I t has been stated that the foregoing example represents the simplest possible case of a \u201cmechanical circuit,\u201d being one in which there are only two parts. In the design of any actual machine there may be three or four or any number of parts, and it is here that the conception of a mechanical circuit becomes of value. I n Fig. 38 an example is given of a three-part circuit, in Fig. 39 we have a four-part circuit, in Fig. 40 a five-part circuit. It is clear that the greater the number of parts in the mechanical WORM GEAU ANI) WORM GEAR MOUNTING. 13; oircuit the greater will be the accumulated effect of the tolerance (allowed to the individual parta in manufacture) on the ultimate clearance value. In some caaw, as where there is a clearance between every part, with its oil film, such aa a number of sliding bars housed parallel to one another between two retaining jaws, the deaigner\u2019e object to avoid trouble by reducing the number of park in the \u201cmechanical circuit\u201d to the minimum. Such a case is typically illustrated in a worm gear mounting shown in Fig. 42; in this case thero are no less than eight parts i n the mechanical circuit, and there is only one clearance dimension. Tho eight parts are labelled a, b, c, d, e, f , g, and h, and the dimension in which the clearanca is felt may be regarded as that giwn by the letter S. This dimension S is affected by the accumulated tolerance of the eight parts a, b, c, d, e, f , g, h . . Under these conditions the permissible variations in S, divided by the ,Lumber of components in the circuit, defines the degree of accuracy of manufacture or tolerance necessary for the individual components. I t is clear, therefore, that if the accuracy necessary in the dimen&Jn S is greater than can be divided by the number n (8 in the case in point) without resulting in an impracticably close limit from B manufacturing standpoint, full interchangeability may have"
        ]
    },
    {
        "image_filename": "designv11_36_0002574_pime_proc_1861_012_010_02-Figure2-1.png",
        "original_path": "designv11-36/openalex_figure/designv11_36_0002574_pime_proc_1861_012_010_02-Figure2-1.png",
        "caption": "Fig 2 . Trunsverse Sechan,",
        "texts": [
            " 1, Plate 14, is a front elevation ; the headstock is at the right end, and the machine has six spooling heads, each of which fills one spool at the same time. Pig. 2, Plate 15, is a vertical transverse section through the parts operating upon the spool. Figs. 3 to 7, Plates 1 6 and 17, show the detail of the winding, thread-fixing, and spool-changing apparatus, drawn half full size. The thread wound upon the spools is drawn from a large bobbin stuck in the back frame of the machine, as shown in Fig. 2, Plate 15; and is guided and fed regularly upon the spool A by the thread guide B, Figs. 3 and 6, Plates 16 and 17. The spool A is driven a t e speed of about 2000 revolutions per minute. The thread guide B spools. at UNIV NEBRASKA LIBRARIES on June 6, 2016pme.sagepub.comDownloaded from SPOOLING MACHINE. 57 has spring fingers on it, through which the thread is drawn ; these clip the thread with a uniform pressure and ensure its being wound with uniform tightness on the spool. The point of the guide where the thread is delivered carries a small swivel piece C on the underside, the face of which is made with fine grooves corresponding t o the thickness and roundness of the thread : this grooved piece bears on the thread with a uniform pressure while in the act of being wound ; and the swivel joint enables it to coincide correctly with the alternate slight inclination of the thread right and left, since the thread is wound in a right and left handed spiral alternately in the successive layers on the spool",
            "comDownloaded from so that a t the end of the traverse the upper spring has acquired sufficient preponderance of power t o throw the arm over through the required vibration : and in the return tyaverse towads the l e f t hand, the lower spring is bent back and the upper one relaxed, as shown in Fig. 11, ready for reversing the arm again in the same manner. When the winding of the last layer of thread is completed, the whole of the winding motion is instantly stopped dead by the appli- at UNIV NEBRASKA LIBRARIES on June 6, 2016pme.sagepub.comDownloaded from SPOOLIHQ MACHINE. 59 cation of a break K, Fig. 2, Plate 15, consisting of a leather band, shown by the strong black line, passing round a pulley on the main driving shaft of the winding apparatus ; the band is suddenly tightened on the pulley by a lever and cam, and holds all the winding motion quite stationary while the operations of fastening the threads and changing the spools are performed. As soon as the winding is stopped, the incision knife L, Figs. 3 and 7, for cutting the nick in the edge of the spool, descends and niakes the cut, as shown in Fig",
            " The thread guides rise as the spools fill, till the last layer but one, when their rise is obstructed by a cam which gives extra pressure to polish the thread ; but hy the time the last layer is wound on the spool, the cam has turned on far enongh to remove the obstruction to the rise of the thread guide. A t the same time the escape plate X, Fig. 12, is released, and the belt-changing cam causes the driving-belt to be traversed on to the inside driving pnlley, for fastening off the thread and changing the spool ; and a t the same instant lifts the break off this pulley, and puts on the break K, Fig. 2, to stop the winding apparatus. A t the 5th degree of rotation of the cam shafts the thread guide begins to lift clear of the spool, 8s shown in the diagram, Fig, 14, Plate 19, and has finished lifting at the 25th degree, and then becomes stationary. The hook for drawing the thread devn in60 the nick on the spool begins to rise a t about the 12th degree of rotation, 63 SPOOLING NACHINE. in the edge of the spool a t the 40th degree, and then remains stationary, while the spring point connected with it presses on the spool and prevents the thread from getting unwound"
        ],
        "surrounding_texts": []
    },
    {
        "image_filename": "designv11_36_0002616_piae_proc_1916_011_012_02-Figure19-1.png",
        "original_path": "designv11-36/openalex_figure/designv11_36_0002616_piae_proc_1916_011_012_02-Figure19-1.png",
        "caption": "FIG. 19b.",
        "texts": [
            " Another incidental feature which may benoted is the fact that there axe four balance pinions in the differential gear box, each pair mounted on a transverse pin; the figures show clearly the means taken in the design of these oross pins to permit them to clear each other and to clear the axle ends and thrust pad. So far as the worm gear mounting is concerned, these are mere incidents, but the method by which the drive is conveyed from the worm wheel to the balance pinions is essentially of interat . Coming back now to the more directly important points, we may, with reference to Fig. 19a, call attention to the first advance in worm mounting after the type shown in Fig. 16. In this we see that roller bearings brought well up to the neck of the worm have been substituted for the bicycle type of bearing in the previous figure, and a double ball thrust between flat parallel races has been applied at the tail end of the worm shaft. This. design, again, was before the period in which ball or roller bearings could be purchased from specialised makers, and the bearings were made in every detail at the Lanchaster Company\u2019s works. It will be seen that.the thrust bearing in this design is very compact, but from the modern point of view and with present day loads and speeds it would not be considered adequata. Owing to the incline of the worm shaft and the importance of ground clearance, the tail position is at a disadvantage compared to the driving end of the worm shaft in the matter of permissible diameter, hence, when we pass to a later design, Fig. 19b, in which the bearings (both cylinder and thrust) are far more robust, the thrust is fitted at the neck or forward end. I n Fig. 20 (early 110 THE INSTITUTION OF AUTOMOBI1,E ENGINEERS. 20 h.p.), we find that the ball thrust bearing has again been arranged at the forward end of the worm, and in this dasign an innovation was tried experimentally to do away with the ball counterthrust and employ a series of thrust washers, the efficiency clearly being a matter of no importance when the brake is being employed"
        ],
        "surrounding_texts": []
    },
    {
        "image_filename": "designv11_36_0002547_piae_proc_1920_015_011_02-Figure12-1.png",
        "original_path": "designv11-36/openalex_figure/designv11_36_0002547_piae_proc_1920_015_011_02-Figure12-1.png",
        "caption": "FIG. 12.-Beardmore Precision Front Fork.",
        "texts": [],
        "surrounding_texts": [
            "several long springs working in combination, care would have to be taken to see that the springs did nok foul each other, and numerous guides would be required, while there would &o have to be many small pins and eyes, bolts, etc. FIGI. 9 With extension springs it would be difficult to work in a cornbEnation type, and the oinly suggestion is to change the action from the non-progressivse type to a, resultant action in which the load was no longer directly proportional to the deflection. This at PENNSYLVANIA STATE UNIV on June 5, 2016pau.sagepub.comDownloaded from THE SPlZINGIKG OF MOTOR CYCLES. 57 could be done without much difficulty by altiering the leverage of the spring on the links as it way extended, or by inoreasing tha rate a t whioh it was extended for a given movement of the wheel. Experience hes shown that in parallel mound extension springs, the safe valuie of the stress per sq. in. is only about two-thirds of that fon open coiled coinpression springs of the same dimensions; other considenations may, hoivever, outweigh this disadvantage. The author believes that pneumatic springs h w e been used on motor cycles yeam ago,* and they have much to recommend them if the mechanical difficulties can be overcome. A last alternative is the volute or conical spring, which can be made to practically any rate of progression, and it would seem to be worth while experimenting with this type. I n one type of front fork, conical springs acting in conipression are dmady fitted, but they are short and ane only very slightly taper. A conical spying is not satisfacLory when used in extension, as sufficient load to fully stress the smaller or stiffer coils cannot be applied without distorting thee larger coils. Blefore leaving this side of the springing question, it would be as well to discuss the merits or demerits of friction, and this has lately been a much debated question. For perfectioa, a damping rlevice which would come into action after the first big deflection either way, after the wheel has passed its normal position, is desirable. I f the author could not have this, however, he would prefer to have friction in the springing of a motor cycle rather than none a t all, chiefly la steady the springs and damp out oscillations, this especially when the machine is travelling over a, road with more or lesls regular undulations which happen to fit in with the natural period of the motor cycle suspension. The objection to friction, as pointed out by Mr. G. H. Baillie in his! paper before the Institution in 1913,: is that it increases the change of accderation, and change of acceleration causes that jerk which is uncomfortable to the rider or passenger. I n the caste of a car, as there is very little danger from the cumulative effect of regular undulations on the springing (which would be greater with no friction in the springs), comfort is the first considwation. On a motor cycle, however, the case is different; the machine is in a state of unstable equilibrium, and as * SeeProc. I.A.E. Vol. IV. pa 87. + See Proc. I.A.E. Vol. VII. p. 451. at PENNSYLVANIA STATE UNIV on June 5, 2016pau.sagepub.comDownloaded from 58 THE INSIIlUT1ON OF AUTOMOHI1,R ESGINEERS. this cumulative effect on springing could be very dangerous, the extra or excessive comfort must be a very secondary consideration. On a considerable number of machines now horizontal springs are also fitted on the front forks ; the wheel is thus sprung in two directions, and that these springs do useful work can be appreciated by siding a machine SO fitted. In the author\u2019s opinion, however, these are only useful when vertical springs are too stiff, and on a front fork fitted with reasonably flexible springs the horinontal springs would not be required, especially as the motor cycle front forks (are already a t an angle of ab\u2019out 30 degrees to the vertical in the direction of the shock. A point that has b\u2019een raised in objection to these horizontal springs is that the steering lead is continually changing, and that there would be danger when riding round a curve. A inovenlent of ab\u2019out one inch is fairly usual on these horizontal springs, which would be lfr in. to 2 in. on the wlieel. I n the author\u2019s experience, these horizontal springs do not have any particular effeclt on the steering, although i t is possible that they might at high speeds. The question arises as to whether it should be arranged that the springs give lateral support to the forks. That the laminated springs do give lateral support on most makes of cars is well known; at the same time it should be remembered that a certain ainount oE side play on the axles of the ordinary touring car does not matter, while on a motor cycle practically no play at all can be allowed. The question is a compromise, and the author only says that if possible it would be better to arrange that suitable faces should give lateral support, and the springs take their direct load only. On the type of spring which is fittied with an eye and shackles, if the bearing in the spring eye is to work nioely, it must have some clearance on tihe sides, s o that biefore the spring clan help in the lateral stability the bearing i n which the rear fork is hinged must have worn enough for the fork to rock over and take up this clearance. In the gmthor\u2019s opinion, by the time this biearing is wjorn to that extent it ,requires renewing. In the A.B.C. type of springing, Fig. 10, the spring does give lateral support to the wheel, as it is b b h d solidly at each end to the frame and the rear fork respectively. DQaling with the eye of the leaf spring, on several makes shackle plates and pins of good proportions are employed, and on the Royal Ruby patented roller bearings as shown in the upper part of Fig. 4 are fitted to eliminate lateral play, and they should at PENNSYLVANIA STATE UNIV on June 5, 2016pau.sagepub.comDownloaded from work well. The author thinks, however, that these shackles are a refinement, and he would recommend in a great inany cases simply a flat end to the spring and no eye. A roller for the spring to work against is unnecessary, it should simpIy work against a fiat face; a t the end of the back of the spring should be a crosspiece, with possibly a rubber buffer to catch the spring on rebound or when the wheel drops into a hole. An objection tao &is type is that there would be a tapping noiw if the end of ihe spring left this face, but the author has ridden a maohine so fitted, and he experienoed no inconvenience. This hype is ,much cheaper to make, and the possible noise could hardly be counted a slerious objection until the motor cycle engine is more silent ,than it is at preslent. English designers throughout s h d d remember Ford gractioe a liktle more-eheap and sinipls and doesn\u2019t look nbe, b\u2019ut the public gets used to it, and it works -Ford taught the public, and didn\u2019t let the public teach him. It would be as well to compare the different designs of front forks, of which there seem to be three distinct types. The most usual k the paralleI link motion type, whcere the links oonneat from the top of the front forks to the head of the frame, then the type i~ on the Triumph and the Beardmore Precision, where the front fork i s hinged at the crown, a d lastly the design which seems to be popular on American machines, and which is also embodied in the Phelan and Moore front forks, where the con- at PENNSYLVANIA STATE UNIV on June 5, 2016pau.sagepub.comDownloaded from 60 THE INS'l ' lTtiTIO~ OF AUTOMOBILE ENGINEERS. necting link coineb straight off the wheel spindle. I t would be hard to say which type is best, as they are, in Cioimiion with mosti engineering problems, a conipromise ; of the three, the author prefers the first mentioned, where the links bridge from the top1 of the front forks to the l i e d . The bearings in this type are long, easy to lubricate, easy to adjust, accessible, simple and out of the dirt, and in practice they stand up quite well. The tendency is now to make the link spindles of larger diameter, as on the Douglas type shown in On the P. &: M. and American type, there is the advantage that when uring helical springs, the angular movement of one at PENNSYLVANIA STATE UNIV on June 5, 2016pau.sagepub.comDownloaded from THE SPRINGING OF MOTOR CYCLES. 61 end of the spring in relation to the other when bieing compressed or extended is less than with the first nientioned link motion type, and another advantage is that there will ble slightly less unsprung weight. When the wheel is in front of the bearing it hinges from, it would seem t.hat one advantage of this type is delstroyed; if the wheel is behind the bearing, it is trailing, and its position could be such that it would be readily responsive to road shocks from a large range of directions. A t the same timr, howlever, the at PENNSYLVANIA STATE UNIV on June 5, 2016pau.sagepub.comDownloaded from"
        ]
    },
    {
        "image_filename": "designv11_36_0002616_piae_proc_1916_011_012_02-Figure26-1.png",
        "original_path": "designv11-36/openalex_figure/designv11_36_0002616_piae_proc_1916_011_012_02-Figure26-1.png",
        "caption": "FIG. 26.",
        "texts": [],
        "surrounding_texts": [
            "I t has frequently been urged, to some extent truly, that the Hindley or Lanchester worm gear requires greater precautions in mounting than is the case with a gear of the parallel type. The point is that whereas in the Lanchaster type the worm thrust has to be accurately located, in the parallel type 80 long aa the worm axis is correct as to position the longitudinal location of the worm is of no importance. The matter may be carried a step further; worm gear of the parallel type in turn may be said to require more careful mounting than common screw gear, in which both worm and wheel are of the ordinary screw-cut spiral form. Thus the argument that the Hindley or Lanchester gear is at a &ad- * In the parallel type of worm it will be seen from Fig. 16b that there is very little constancy in the type of the bearing contact ; actual concavities in the teeth frequently make their appearance with no proper driving contaot. Beyond this the mere degree of convexity, although a valuable indication, ia not the whole criterion in view of the squeegee action dealt with in the discneeion of the-previous paper. Compare Proceedings 1913-14, Vol. VII., p. 279.\u201d 102 THE INSTITUTION OF AUTOMOBILE ENGINEERS. ventage, on amount of the extra precautions required, aa compsrd with parallel worm gear, may be quite as reasonably urged against worm gear of every kind in favour of ordinary screw gearing suah aa commonly used to drive the side shaft of a gas engine. Suoh arguments are clearly without weight if any adequate advantage can be &own to exist. In practice the whole point of difference h i n p on the correot location of the worm thrusts, since in every other respect any want or loss of alinement affects both types of gear equally. It may be doubted tu a matter of experience whether the Hindley type of worm gear is actually at as great a disadvantage as its WORM GEAR A N D WORM (SEAR MOUNTING. 103 detractors would represent, the Lancheater gear at least has shown itself capable of working surprisingly well under the severe conditions which supervene when a worm thrust bearing fails. Admitting, however, that the durability of the gear does definitely depend upon the permanence of alinement aa determined by the thrust bearing, the problem resolves ih l f into the comparatively simple question of how, under manufacturing conditions, the initial accuracy of alinement can be secured; beyond this, the durability of the alinement resolves itself into a question of fixing the proportion and type of thrust bearing best employed, and of the general soundnew of the mounting as a piece of engineering. The earliest type of mounting employed in the application of Fio. 16a. worm ge'ar to the original Lanchester OBS is shown in Figs. 16,*16a, and 17. Hero it will be noted that the ball bearings are not of the modern type, the design dating back to a time when such bearin@ were not a s tandard id or a marketed commodity; two double bearings of the bicycle cup and cone type are arranged a t opposite ends of the worm, the whole combination being symmetrical. The cups were made adjustable by housing them within an internally screwed sleeve piece, and the adjustment was fixed by a key or cotter engaging with one of twenty-four notches cut in the periphery of each cup, Fig. 16a. The pitch of the thread was twelve per inch, so that the design gave a capacity of adjustment to within approximately three and a half one-thousandths of an inch, which 104 THE IXSTITUTLON O F AUTOMOBlLE ENGINEERS. was found to give satisfactory results in practice. Here we stumble against one of the misconceptions which are current with regard to the Hindley type of gear; it has often been represented that the accuracy of alinement of the worm requires to be true to within a thousandth of an inch of gedmetrical accuracy: 'from the sucmss of the arrangement described, it is clear that no such degree of accuracy is essential. It will be noted in the bearing in question that (as in the IWW of the old bicycle ball bearing) there is no separate function of cylinder bearing and thrust, and without doubt from a modern standpoint the type of bearing shown in Figs. 16 and 16a would be considered lacking in durability. No trouble was experienced from expansion (due to temperature) as between the two thrust bearings, and i t is fair to regard the casing, as indeed the whole of the parts, as sdliciently elastic to take up any small temperature difference. It is possible that at times one thrust bearing is called upon to sustain more thrust and at other times less than its fellow, but there has been no actual evidence of this taking place. The worm wheel bearings shown in Fig. 17 are roller bearings of the cheese roller type without cage of any kind. These are in fact the bearings on which the balance gear box is WORM QEAR A N D W O R M OEAR MOUNTING. 105 mounted, and the worm wheel itself forms the central seotion of the balance gear box. The thrusts were of a specially designed type, and consisted of balls in a flat cage between two perfectly flat ground and hardened thrust washem, the balls being arranged in a spiral manner,* Fig. 18. The object of this arrangement, i.e., the spiral distribution of the balls, is that each ball ma3 bear on a different part of the flattened surface, so distributing the wear; a further advantage is, that if the balls vary amongst themselves aa to diameter, as is commonly the caae, each ball will form its own race and will soon be taking its due proportion od the 10ad-h markings on the thrust r a m frequently gave evi- denoe of this action. The degree of inaccuracy amongst balls of nominally the same diameter is cowonly less than one tenthouculndth of an inch. This form of bearing waa in every, way successful and satisfactory; that it has since been dropped is due to the fact that excellent thrust bearings have now been placed on the market by specialised manufacturers. In the modern worm mounting, the type of bearing given in Fig. 16 haa been long since abandoned, and to-day it is the invariable practice to separate the functions of radial load and thrust and provide for each by a bearing speually designed Patent 17,032 of 1901. 106 THE INSTITUTION OF AUTOMOBILE ENGINEERS. for khe,purpose. Thus in%igs. 19a, 19b, 20 and 23, a roller bearing is employed independent of the thrust; in some cases this bearing is of the long-roller type, in others (Fig. 23) the \u201ccheese\u201d type iS adopted. In Figs. 24 and 26 and those which follow, it will be seen that the radial bearing also in common use is the symmetrical type of ball bearing 89 now to be obtained from several firms, such m the Hoffmann, Skefko, Duplex, etc., and the h s t is independently carried. It is worthy of note that in the modern mountings, the thrust bearing, a double thrust, is almost invariably fitted at ope end.* Objection has been taken to this arrangement on the ground that any inequality of expansion between the worm shaft and the casing will throw the worm out of centre, in other words, the objection is baaed on the faat that the arrangement is unsymmetrical. There are two answers to this. Firstly, the temperature difference is a mere \u201cbagatelle\u201d; thus the whole range of temperatures between the hotteat and coolest parts of the gear box is included between an * An exception to the practice of employing separate radial and thrust bearingi L to be found in cases where the American type of conical roller bearin@: has been adopted. WORM (;EAR AND WORM GEAR MOUNTING. 107 e tmqher ia temperature, say, 20\" C. and an upper extreme of about 100' 0.; speaking generally, the difference between one part and another does not exceed 40\" C. or 50\" C. At the worst, calculation gives the relative displacement of the worm oentre line and the wheel centre line due to the cause stated es not exceeding two or three thousandths of an inch. In practice it is doubtful whether it is ever aa great as this: in any w e it has not been found to be detrimental. Secondly, if , as is the only alternative, the thrust and oounterthrust be arranged at opposite ends of the worm shaft, there will be a much bigger expansion difference to take up between thrust and counterthrust, probably twice aa great a~ that now between worm and thrust bearing. This expansion might have a detrimental effect on the thrust bearings and ultimately lead to their disintegration. The failure of a thrust bearing may be regarded as perhaps the worst \"accident\" which can happen to a worm gear. The author will now dascribe in detail a few of the later and more succassful types of worm mounting, and some of those which am historically the more important. The &st series whioh will be taken will be in continuation of Figs. 16 and 19, showing the historical development of worm mounting in the practice of the Lanchester Company. It will be noted on comparison of the figures given that there are certain featuras of the Lamhestor mounting which have survived from the earliest designs, notably 108 T H E IN ST IT U T IO N O F A U T O M O B I L E E N Q IN E E R S. 0 cy 8 4 WORM QEAR AND WORM GEAR MOUNTING. 109 the splined shaft on which the worm assemblage is mounted, also the method of building in the worm wheel as part of the balance gear box, and in providing for the housing in the worm wheel meting itself of the cross pin or pins on which the balance gear bevels are mounted. In this arrangement, which is common to the whole of the series, it will be seen that the drire from the bevel wheel is taken directly on to the balance pinions, and the covers of the balance gear box are not used to convey torque but only the thrust and other forces by which the wheel is held in alinement. It will be noted that the thrust bearings serving the balance gear box take not only the worm thrusts but also the axle thrusts. There is a bronze pad fitted between the axle ends by which the thrust is conveyed from one axle to the other and thence to the thrust bearing, Fig. 21. Another incidental feature which may benoted is the fact that there axe four balance pinions in the differential gear box, each pair mounted on a transverse pin; the figures show clearly the means taken in the design of these oross pins to permit them to clear each other and to clear the axle ends and thrust pad. So far as the worm gear mounting is concerned, these are mere incidents, but the method by which the drive is conveyed from the worm wheel to the balance pinions is essentially of interat . Coming back now to the more directly important points, we may, with reference to Fig. 19a, call attention to the first advance in worm mounting after the type shown in Fig. 16. In this we see that roller bearings brought well up to the neck of the worm have been substituted for the bicycle type of bearing in the previous figure, and a double ball thrust between flat parallel races has been applied at the tail end of the worm shaft. This. design, again, was before the period in which ball or roller bearings could be purchased from specialised makers, and the bearings were made in every detail at the Lanchaster Company\u2019s works. It will be seen that.the thrust bearing in this design is very compact, but from the modern point of view and with present day loads and speeds it would not be considered adequata. Owing to the incline of the worm shaft and the importance of ground clearance, the tail position is at a disadvantage compared to the driving end of the worm shaft in the matter of permissible diameter, hence, when we pass to a later design, Fig. 19b, in which the bearings (both cylinder and thrust) are far more robust, the thrust is fitted at the neck or forward end. I n Fig. 20 (early 110 THE INSTITUTION OF AUTOMOBI1,E ENGINEERS. 20 h.p.), we find that the ball thrust bearing has again been arranged at the forward end of the worm, and in this dasign an innovation was tried experimentally to do away with the ball counterthrust and employ a series of thrust washers, the efficiency clearly being a matter of no importance when the brake is being employed. A notable feature in this dasign is the very large diameter of the thrust balls. Fig. 21 gives the corresponding FIO. 21. section through the worm wheel axis. Here we see the spiral typo of thrust bearing with flat races still holding its own. A feature which is worthy of mention in many of thase early mountings is the employment of the \u201cchetxie\u201d type of roller bearing, that is to say, a type in which the length and diameters of the rollers are about equal. This is a type of bearing which the author developed in the experimental period of car building, WOHM QEAR AND WOKM GEAR MOUNTINCf. 111 and which w a ~ used in the Gold Medal phaeton built in 1897-8. The employment of this type of bearing WM extended considerably in the 10-12 design in 1900, where it W&B used throughout the re= axle and parts of the oountershaft. It is only within the last few y e m that bearings of this pattern have been taken up and introduoed by the Hoffmann Company and others. There is a differenoe in practice inasmuch as the bearings marketed at the present day appear to be all fitted with cages, whereas in the FIU. 22. author\u2019s experience a cage is absolutely unnecessary in bearinp of the \u201ccheese\u201d roller type. In any , m e the guiding of the rollers is done from the ends, and this is really the definite distinction between the ordinaxy roller bearing and that of the \u201ccheese\u201d type, in the former the roller being guided from its cylindrical surfacw, the cage being a necessity. Generally, speaking, it has been the author\u2019s practice to so design the bearing that the rollers once in position could not fall ou t ; thus, in the axle bearings shown in Fig. 17, the diameters of rollers and 112 T H E IN ST IT U T IO N O F A U T O M O B I L E E N Q IK E E R S. WORM QEAH AND WORM GEAR MOUNTING. 11 3 races were such that the axle or central race could be removed and the rollers could not be displaced. The clearance was so small that the rollers would lock before they could come free, ,as illustrated diagrammatically in Fig. 22. On the worm bearings we again see the cheese roller bearing of the cagele~s type employed, and a double thrust bearing on the tail end of the shaft. The whole outline of the worm housing, however, hits been made very clean and smooth externally. The corresponding axle mounting is given in Fig. 21. Here it may be seen that on the axle bearing the ball has in this case replaced the roller. It may almost appear, in looking at these changes, that in some cases, in which the change goes from one arrangement to another, and then back again at a later data, there is certain evidence of infirmity of purpose. As a matter of fact, changes are frequently due to conditions which are temporary, and often two designs are so nearly equal in merit that whether one or the other be adopted is purely a matter of convenience. A great deal must depend. upon whether the designer has a completely free hand or whether he is required to make use of standard components. I t will be noted that amongst the various changes the practice of the Lanchester Company has slways been to place the worm shaft below the axle. One knotty point has existed throughout almost the whole history of gear box mounting, and that is the manner in which alinement is to be secured. There are four methods open: firstly, the parts may be made with sufficient mechanical exactitude to ensure perfect interchangeability and alinement within the necessary degree of accuracy. Secondly, a screw or other variable adjustment may be provided by which the necessary alinement may be secured in spite of individual variation in the parts. Thirdly, the method of using pen steel washers or \"shims \" may be adopted. Fourthly, an accommodation piece may be employed. In the earliest type of mounting (already discussed, Fig. 16)) the method of screw adjustnient was employed, and up to a certain point was found satisfactory. I t had the wealtness, however, that, if the mountings were taken down, either the parts would have to be carefully marked, which might be forgotten, or in re-assembling an experienced hand would have to be employed,-who might not always be available. In brief, the screw adjusted mounting is not fool-proof.\" In departing A still later type of mounting is given in Fig. 23. LANCHES'l'ER. H 114 THE INSTITUTION OF AUTOMOBILE ENQINEERS. from this the author endeavoured to attain perfection and prescribed limits to the components and methods of gauging by which completo interchangeability waa secured. This ideal, however, F I ~ . 24. is cxtremely difficult to get carried out. The number of parts in the \u201cmechanical circuit\u201d is great, and, in ordar to avoid excessive variation in the aggregate, the individual liiiiits require to be unusually fine. So long as all the components are made WORM QEAR AND WORM GEAR MOUNTING. 11s in the same works a s the car the thing can be done, and it has been successfully done by the Lanchester Company. The d i5culty, however, arises when it is desired to increase the output and bearings have to be purchased from firms who specialise in such commodities; the degree of accuracy to which they will guarantee to work is totally inadequate, in .other words, bearing makers will not guarantee to work to thickness limits or width limits less than five one-thousandths of an inch, and if such limits were tolerated the total inaccuracy in the case of a worm mounting would amount to rn many hundredths of an inch as it should be thousandths. * The author has never found it cheaper to work to a low degree of accuracy than to work to a high degree of accuracy,; in other words, a thrust bearing can be produced which from face to face does not differ by more than a thousandth just as cheaply as i t can be produced to within two or three one-thousandths. Whatever difference of Gost there may be is more than compensated for by the advantage of interchangeability. I n other words, the actual production of a part accurately to dimensions, that is to say, within fine limits, may be slightly greater, but in any complex piece of machinery the saving in ms't of assemblage will pay the bill many times over. The above is no mere ideal or unsupported opinion, i t is based on hard experience. Some years ago, in designing certain mechanism (which need not be specified) every clearance dimension and tolerance dimension was set personally by the author'8 own hands, and these were worked to for a considerable time with satisfactory results. A new works manager, who did not believe in working to fine limits, reported that the limits were unduly fastidious and that money could be saved by relaxing the limits and so avoid having to scrap parts. The managing director consented and the scheme was tried. A slight and questionable reduction resulted in the cost of manufacturing components, but the increased cost of assembling and testing, and the cost of rectifying complaints, etc. became so great that the initial saving was swallowed up many times over. Within twelve months the scheme was abandoned and the old fine tolerances were rmtored, the expense of twice altering the gauges, etc. being a dead loss apart from the disastrous results of the experiment. The Hoff mann limit on the width in a standard ball bearing is +0*006, a total variation of 0.01 in. or mm. - H 2 116 THE INSTITUTION OF AUTOMOBILE ENQINEERS. The author thinks he could go further and say that he has never made an endeavour to do anything better than proviously, without finding that when it is being done better it is also being done cheaper. Thus, the \u201csplined shaft\u201d was looked a t by some as a piece of fantastic extravagance when first introduced, but it showed itself to be a money saver from the outset; it is far cheaper to cut a splined shaft and drift the hole to correspond, than it is to cut a key way and make and fit a key; also the job is incomparably better engineering when done. I t is, perhaps, the more legitimate to cite this example since it was in connection with worm mountings that the splined shaft was first introduced into motor car practice; the worm shaft of the 10-12 h.p. Lanchaster car, Fig. 16, also the gear box, were, the author believes, the first applications of the splined shaft in the history of automobile engineering. * Returning to the main point under discusqion, it has been stated that though commercially possible, and probably advantageous, to fir the limits of the various components to secure perfect interchangeability in a worm gear mounting, it can only be done provided that the whole of the parts are made by the builders; a t least in cases such as ball or roller bearings the offending dimensions must be rectified after they have been received from the manufacturer. There are commonly some eight parts or thereabouts of which the tolerance differences accumulate, and to attain perfect interchangeability the whole sum of theset must be kept down to within four or five one-thousandths of an inch. Admittedly the individual limits are fine. Owing to the difficulty of obtaining the necessary interchangeability egpecially where ball boarings, etc. were ordered from outside sources, the Lanchester Company have from time to time resorted to an accommodation piecc, or havc made use of \u201cshims\u201d in order to secure the nocessary accuracy of alinement. There is more to be said in the case of a worm gear mounting for this practice than might appear to the idealist; it is, for example, admitted that the various components, thrust bearings, etc. are liable to a certain amount of wear; occasionally, also, the whole assemblage will be found to have developed internal sloggar, in which case the components may undergo considerable \u2018 I punishment \u201d and additional inaccu- , * In f l ~ p s . 19a, 19b. 20, 23, etr., Pplined tihaftR are emploved in every case, In FiFs. 21 and 24 also the axle end. bnt the Pplines me oot shown in detail. (althouuh not Nhlwn W R such) are aplined for the fitting of the bevel wheels. f Compare Appendu. WORM GlEAR AND WOKM GEAR MOUXTING. 117 racy is introduced. Under these conditions tho use of sh\u2019ims in the repair shop is fully justified, and a very good job indeed can \u2019be made if the points at which the shims are inserted are such as to present a sufficient area, and i f the shims themselvea axe of pen steel or other suitable hard grade of material. If this be not the case, there is always the danger of the shimma being spun out or hammered out, and eventually disintegrating, in which case the parts may get Ioose in the gear box. There is also the fourth expedient above given: the accommodatioii piece. In all interchangeable work in mechanical engineering a point may ultimately be reached when the accumulation of the tolerances of the individual components results in the individual limits having to be cut down to a point below anything which may be considered reasonable. I t then becomes a question of judgment for the designer (as in the case of the worm gear under discussion) how the difficulty is to be met: one method is that of the accommodation piece. Thus one piece in the whole \u201cmechanical circuit\u201d is left to be fitted, or is made in several different standards of thickness. This is f a r better practice than to have a pretended interchangeability which does not really exist in which the accumulated tolerances do not come within the aggregate limit, and which in the assembling of a machine has to depend upon the selection of compatible components. Thus, on many pieces of mechanism at present being manufactured for the Government there are limik specified on the aggregate assemblages which are inconsistent with the limits pormitted on the individual components, so that a manufacturer may make his components within the limits specified and yet he may not have a single assemblage which will go together. I t is frequently true that it would be far easier to put finer limits on the individual components and devise means of working to them, but obviously, as already stated, there is a limit to what is commercially possible. When this limit is reached the alternative to the very unsatisfactory state of things above described is to make one of the components an accommodation piece, and either admit that part as a fitter\u2019s job, that is to say, allow it to be filed or otherwise adapted to the rest of the assemblage, or else to make that particular part in sufficient variety and confine the selecting to that one particular component. In the Appendix is given an oxainple of a case where the number of dimensions in the mechanical circuit is about normal for a 118 THE INSTITUTION OF AUTOMOBILE ENGINEERS. worm transmission, and examples of suitable component dirnensions are given in detail as figured on an interchangeable basis. I n the worst or extreme cases given by theee dimensions the difference amounts to 0.01 in. in the worm and wheel location ; this may bo taken as within the limits of good practice. I t is clear from this example that a very high degree of accuracy in manufacture is necessary in order to obtain the desired result. The difficulty mentioned in the case of \u201cshims,\u201d namely, that they aro liable to be spun or beaten out, is a difficulty met with more broadly and in a more general way in worm gear mountings. The parts intervening between the thrust and the worm appear in practice to need to be able to stand a lot of \u201cpunishment,\u201d and it is most important that no backlash shall exist. The consolidation of the worm shaft assemblage is usually provided for by pulling the whole string of components, namely, worm, distance piece, bearing ring, thrust washer, etc. thoroughly solid by a nut of ample proportions, as may\u2019be seen from the various figures. In some cases this nut has been locked by means of a, caulking plate, in other cases the customary split cotter has been employed. Where the latter practice is adopted it is important that the nut shall be pulled thoroughly home before the hole is drilled for the split cotter, and even under these conditions there are certain objections to locking in this way. Owing to the trouble which has been found to develop if any initial backlash once makes its appearance, it has been the author\u2019s practice for some time to specify that all the components forming this compression assemblage shall be hardened, either being made of a high carbon steel or case-hardened according to circumstances. When this precaution is taken, and when the abutting areas are made sufficient, all trouble from the cause stated has been found b Tho experience of the Daimler Company, though dating from more recent time, is considerably wider than that of the Lanchevter firm, inasmuch as the range of sizes and standards as defined by the different centres and ratios of gear is far greater; the applications range from the lighter types of pleasure vehicles, both petrol and electric, to the heaviest type of motor lorry, namely, the five-ton vehicle. The whole range of the Daimler-Lanchester worm gear standards is laid out diagrammatically to scale in Fig. 25.* The different The LaWhebhr Compang\u2019a standards include types A and B only. and are cease. Type A B *Load at 1 ton,per 24 1.5 nq. in. TOT# In. Ton In. I i C D F a 4.2 1.1 1-52 8-9 Ton In. Ton In. Ton In. Ton ha. i l J ! H J K L 0 P 0.7 8.4 1.75 1.17 12.8 5.7 Ton In. Ton In. Ton In. Ton In. 2bn ln. Tm In. L-, -- LH ButhHands 9 a t Centres - 1 - 5.44 LEE ,.,,),: 4-33 w Pi FIQ. 25. * These torque values refer to the wheel element, and are bmed on a 1c.ading of one tcn per tq. in. projected tooth area. 1 7.36 RH They represent roughly the ordinary caondition of running on the high gear. The maximum 8afe load for thort periods may be taken as four or five times peat . 120 THE INSTITUTION O F AUTOMOBILE ENQINEERB. standards of blank are designated by the capital letters A, B, C, etc., in the order in which they were initially established. Types A, B, C, F, and IC have been produced for private pleasure cam,. etc. Types D and L more particularly for electrical vehiclea (supplied mainly to the U.S.A.). Types H, J, and 0 for commercial heavy vehicles, and type G for particular application to (stationary) power transmission. Thus, in greater detail, type B, 6 in. or 152 mm. centres, is that used almost universally in full weight touring cars, limousines, etc.* Type K, 137 mm. or 5T7F in. centres, for cars of, say, identical with those given except that the Lancheater Company\u2019a list does not indude the 9/32 ratio type B, but includes a 6/36 ratio in type A. In addition to this the Lonchexter Company\u2019s standrirds in the B type include left-handed cut.ters only, but their list includes a oertain number of right-handed cuttera in type A. In all cases it is the weight of the car rather than the h.p. which k of importance. Up to 60 cwt. gross or even over. WORM QEAH A N D WORM OEAR\u2019MOUNTING. 12 I 20 \u201clegal\u201d* h.p., weight not exceeding 32 cwt. gross. Type F , 120 mm. or 42 in. centras, for cars of, say, 16 \u201clegal\u201d h.p., not exceeding 28 cwt. gross. The typas H and J, 72 in. or 196 mm. centres, are for three-ton lorrim, \u2018bus chassis and the like. Type 0, 9 in. or 228 mm. centres, is for the heaviest road vehicle at present in ordinary commercial use, namely, the five-ton lorry. A typical mounting for the A and B standards of gear is illustrated in Figs. 26 and 27. There is little to be noted here except the self-adjusting spherical thrust bearings which prevent; FIQ. 27. undue or unevenly distributed stresses on the thrust bearings as plausibly due to any slight \u201cwhip \u201d or spring of the mounting or want of alinement. Contrary to the Lancliester Conipany\u2019e practice, also, it may be noted that the road wheel thrusts are taken independently of the differential box mounting. Figs. 28 and 29 illustrate the mounting adopted in the 20 h.p. Daimler chassis used to a considerable extent for Staff, Red Cross and other purposes at the Front. I n this mounting the worm iS * The \u201c legal \u201d h.p. i H nieasured by the R. A C. rating 0.4 D2n. 122 THE INSTITUTlON O F AUTOMOBILE ENQINEEKS. on top, and the worm box is cast integral with the main portion of the gear box. An interesting feature in this mounting is the fact that the thrust is placed adjacent to the worm itself, and the bearing is placed beyond. This inversion of the usual order results in a bigger bending moment on the worm shaft, but there is ample strength to carry this. The advantage lies in the f:rd FIQ. 28. that as designed there are, including the worm, only five parts in the mechanical circuit, if we regard the variation in ball diameter as negligible. These are the worm, the thrust half bush, the thrust live ring, the thrust Exed ring, and, finally, the gear box casting. Thus, the total variation in the location of the worm is the sum of five tolerances, or, as already expressed, there are five elements in the mechanical circuit. This may bc considered a WORM GEAR AND WORM GEAR MOUNTING. 123 distinct advance in worm gear mounting as a step to securing interchangeability. Figs. 30 and 31 show the G standard mounted as a fixed transmission-as such i t has been applied for the driving of air comprwiore, etc. and other slow running plant from electro-motors. It is good for 150 b.h.p. at 1,000 revs. per minute of the worm shaft. It may be noted that thO Daimler Company\u2019s standard types for commercial vehicles (lorries, buses, and the like) are of a heavier type, and, generally spcaking, of considerably lower gear ratio than thoso for pleasure vehicles, the differcnce being mainly duo to tho slower speeds commonly in demand and the larger diameter of the road wheels necessary for the duties in question, coupled with tho fact that the engine speed is not proportionately lower. It may, be said that in the application of worm gear to com- 124 T H E IN ST IT V IIO S O F A U T O M O B IL E B N O lN E B llS . WORM QEAR AND WORM GEAR MOUNTING. 125 mercial vehiclw the conditions are on the whole more exacting than in the touring car. The driving mechanism is rarely 80 refined, and the driver himself is not usually 80 fastidious. Beyond this, the loads are heavier, the tyres less yielding, the suspension. etiffer, and generally all the conditions which tend to \u201cliustle\u201d the gear exist in a more aggravated form. In consequence of this, it might be supposed that all the precautions which have been enumerated as tending to secure solidity of the worm shaft essemblage in the pleasure car will be at least aa important in FIO. 32. the heavy commercial vehicle: experience has fully justified this anticipation. It is absolutely necessary that the compression park ~d thrust surfaces between the various components of the assemblage, namely, worm, spacing collar, roller race, thrust washer, etc., should be of ample area and on no account must they be left soft. As exemplifying points of good and bad design in this respect a comparison may be made between Figs. 32 and 33. In Fig. 32 a poor design of worm assemblage is illustrated, in which the defects are intentionally exaggerated; in Fig. 33 a 126 THE INSTITUTlON OF AUTOMOBILE ENGINEER& good design is given, showing the proportions and precautions necessary to ensure BUCCBSS. Referring to Fig. 32, it will be seen that the thrust surface3 between the spacing pieces at a, b, c, d, etc. axe of insufficient area. So far as concerns the taking of the necessary thrust reaction, they might with justice be regarded 8~ more than ample; for example, at the point d the area of the contact faces is more than a square inch, and may be taken as safe in compression for a force of ten tons-the actual maximum FIQ. 33. load is not more than one-third or one-fourth of that amount. A8 a mattar of experience, however, no such design will stand up, the faces in contact are found to undergo punishment and sooner or later backlash will develop, and the failure of the mounting follows in a very short time. The author has actually seen 3 cam of this kind in which the one part has eaten into the other a matter of three or four millimetree and the worm has had to adapt itself to an axial displacement of that magnitude; this can hardly be described as fair or proper trwtment. When asked how WORM GEAR AND WORM GEAR MOUNTING. 127 to account for such failurw taking place, considering the cornparatively light t h m t load per square inch carried by the faces in contact, it is fair to say that casea of even admittedly defective design do eometimw stand up; a certain percentage of output will not bo reported as giving trouble. The truth probably is that the failure occurs through a little initial \u201cslogger\u201d oz backlash creeping in, either from careless mounting, due to insufficient initial pressure being put on by the retaining nut,* FIQ. 34. or as oonsequent upon some slight defect in material or by bad or rough handling at some time or another. What has to be remembered is that a mounting which is not open to inspection (without virtually dismounting an axle) must be so designed and constructed as to be reliable even under the most unfavourable conditions; the need for large face contacts and hardened surfacea * The inclusion of a amall quantity of swarf or dirt might be the explanation in some cams."
        ]
    },
    {
        "image_filename": "designv11_36_0002756_paiee.1906.6742509-Figure2-1.png",
        "original_path": "designv11-36/openalex_figure/designv11_36_0002756_paiee.1906.6742509-Figure2-1.png",
        "caption": "FIG. 2.\u2014Complex current I and induction B with maximum values 9 0 \u00b0 behind sinusoidal electromotive force when iron is present. The fundamental (F) sine curve of current lags (90\u2014 <p) degrees behind E.",
        "texts": [
            " W e may then write AdB T di 6 = = - A d T ^ - L d t ' The inductance L is constant; and hence the induction B is proportional to current i and magnetizing force H , permeability * Not including ohmic electromotive force. 6 0 4 BEDELL AND TUTTLE: [Sept. 28 being constant. The hysteresis \" l o o p , \" plotted between B and H, becomes then a straight line. With iron present, inductance and permeability are not con stant. The induction B is no longer proportional to the current i and magnetizing force H, and with induction B sinusoidal (due to sine impressed electromotive force), the current i is not sinusoidal, but distorted as in Fig. 2. Since B and H are no longer proportional; instead of a straight line we have the hysteresis loop representing their cyclic variation. In the following work we shall deal with the fundamental and third harmonic only. The process will be to assume suc cessively definite relative amplitudes and phase positions for these and build up the complex current wave. From this complex wave of current and the sine wave of flux, the hysteresis loop which would cause such a current is determined. The equation for the current is i = sin oj t+ j3 sin (3 co t + 0). The amplitude of the third harmonic is /? (taking the funda mental as unity) and 0. is its phase-angle, + 0 indicating an ad vance, and \u2014 6 a lagging of the origin of the harmonic rela tively to the origin of the fundamental. 1906.] ALTERNATING-CURRENT WAVE FORM. 605 Let us take a typical case represented in Fig. 2. The as sumed fundamental and third harmonic of the current are represented by dotted curves. Here the amplitude of the harmonic is taken to be jj = 0.22 (the amplitude of the funda mental being unity) and 6 is taken to be + 4 5 \u00b0 . The maximum of the current wave necessarily coincides in time with the maxi m u m of the induction (for in a hysteresis loop the max imum H coincides with the max imum B). The sinusoidal flux, in ac cordance with Faraday's law, is 90\u00b0 behind the sinusoidal electromotive force; accordingly, the maximum of the induction and hence of the current is 90\u00b0 behind the electromotive force",
            " It will be noted, however, that the fundamental of the current wave has its max imum in advance of the max imum of the c o m  plex wave by an angle <p, the hysteretic angle of advance, in this case equal to 29\u00b0 2 3 T h e fundamental current wave lags then 90\u00b0 \u2014 <Jf behind the electromotive force and represents power consumed b y hysteresis, with a power-factor cos (90\u00b0 \u2014 <p) = sin (p. If 0, the phase-angle of the harmonic, is between 0\u00b0 and 180\u00b0, we find that the right-hand side of the complex current wave will have a hump, as in Fig. 2. The fundamental: will be ad vanced to the left so as to lag less than 90\u00b0 behind the elec tromotive force, representing power taken by hysteresis\u2014a possible case. If, however, 0 is between 180\u00b0 and 360\u00b0; that is, if the har monic is made to be behind instead of in advance of the funda mental, the hump on the current curve will be found on the left, and the fundamental will be shifted to the right so as to lag more than 90\u00b0 behind the electromotive force, representing power given out b y hysteresis\u2014an impossible case. In this case the hysteresis loop would needs be traversed in the reverse direc tion from the actual counter-clockwise direction and its area would represent work given out per cycle. Fig. 2 turned upside down would represent such a case. D E R I V A T I O N O F H Y S T E R E S I S L O O P . A hysteresis loop consists in plotting corresponding values of B and H in rectangular coordinates. A hysteresis loop cor responding to the curves of Fig. 2 is accordingly readily plotted. H is directly proportional to / , and hence the curve for I may be taken as a curve for H. Corresponding values of H and B 606 BEDELL AND TUTTLE: [Sept. 2 8 are taken directly from the curves in Fig. 2 and plotted in rec tangular coordinates to give the hysteresis loop of Fig. 3. The interpretation is this: we arbitrarily assume a complex current / , made up of a fundamental and third harmonic, Fig. 2. The sinusoidal induction B and electromotive force will then be as shown in Fig. 2. The hysteresis loop which would pro duce the assumed distortion is shown in Fig. 3. When 6 = 0\u00b0, or 180\u00b0, the hysteresis loop becomes a curved line; the ascending and descending curves coincide and enclose no area, representing therefore no hysteresis loss, although the permeability varies. These cases are shown b y curves 5 and 13 in Figs, 14 and 15. They are impossible limiting cases; the angle 0 must accordingly be more than 0\u00b0 and less than 180\u00b0, and positive. It will be shown later that 6 must be greater than 30\u00b0, and that all the curves in Fig",
            " b P ' / / / / B - \u2022 -j/^ s ' vf Q i ^ ^ ^ ^ ^ F I G . 16.\u2014Vector representations in three dimenions of a complex current. E is sine electromotive force; F is fundamental current; Q 3 , harmonics; and 2\" is the equivalent sine current. V E C T O R R E P R E S E N T A T I O N O F C O M P L E X C U R R E N T . Without iron, where current as well as electromotive force is sinusoidal, as shown in Fig. 1, the vector representation of these quantities as lines in a plane is well known. Let us take, however, such a case as shown in Fig. 2, in which the electromotive force E is sinusoidal and the current / , on account of iron, is complex , being composed of a fundamental F and third harmonic Q 3 . Considering first the fundamental F, this may be considered as composed of two components , Fig. 16, a power component 616 BEDELL AND TUTTLE: [Sept. 28 P in phase with E, and a quadrature or wattless component Q1 at right angles to E\\ that is,F = x / P * + Qi 2 . These quantities E, F, P, and Qi are all sine functions of the same frequency and are graphically represented in one plane. The induction B is in the direction of Qv and is also a sine function of fundamental frequency. The fundamental F lags behind E by an angle 9 0 \u2014 0 (as in Fig. 2 ) ; 0 is the angle between Qt (or 5 ) and F. In Fig. 16 and its discussion all quantities represent virtual or square root of mean square values. The harmonic Q3 has no power component in phase with E\\ it is entirely wattless, as has been shown, and hence is to be represented graphically in quadrature to E. But it may be shown* that I = \\ /pz + Q*^ which corresponds to a graphical construction in which Q3 and F are two sides of a rectangle and / the diagonal. As Q3 is thus at right angles to both E and F , it is drawn in the third dimension at right angles to the plane of fundamental frequency in which lie E, F, P, and Qv The total current is / , the diagonal of the rectangular parallelopiped"
        ],
        "surrounding_texts": []
    },
    {
        "image_filename": "designv11_36_0002616_piae_proc_1916_011_012_02-Figure17-1.png",
        "original_path": "designv11-36/openalex_figure/designv11_36_0002616_piae_proc_1916_011_012_02-Figure17-1.png",
        "caption": "FIG. 17",
        "texts": [
            " 16 and 16a would be considered lacking in durability. No trouble was experienced from expansion (due to temperature) as between the two thrust bearings, and i t is fair to regard the casing, as indeed the whole of the parts, as sdliciently elastic to take up any small temperature difference. It is possible that at times one thrust bearing is called upon to sustain more thrust and at other times less than its fellow, but there has been no actual evidence of this taking place. The worm wheel bearings shown in Fig. 17 are roller bearings of the cheese roller type without cage of any kind. These are in fact the bearings on which the balance gear box is WORM QEAR A N D W O R M OEAR MOUNTING. 105 mounted, and the worm wheel itself forms the central seotion of the balance gear box. The thrusts were of a specially designed type, and consisted of balls in a flat cage between two perfectly flat ground and hardened thrust washem, the balls being arranged in a spiral manner,* Fig. 18. The object of this arrangement, i",
            " author\u2019s experience a cage is absolutely unnecessary in bearinp of the \u201ccheese\u201d roller type. In any , m e the guiding of the rollers is done from the ends, and this is really the definite distinction between the ordinaxy roller bearing and that of the \u201ccheese\u201d type, in the former the roller being guided from its cylindrical surfacw, the cage being a necessity. Generally, speaking, it has been the author\u2019s practice to so design the bearing that the rollers once in position could not fall ou t ; thus, in the axle bearings shown in Fig. 17, the diameters of rollers and 112 T H E IN ST IT U T IO N O F A U T O M O B I L E E N Q IK E E R S. WORM QEAH AND WORM GEAR MOUNTING. 11 3 races were such that the axle or central race could be removed and the rollers could not be displaced. The clearance was so small that the rollers would lock before they could come free, ,as illustrated diagrammatically in Fig. 22. On the worm bearings we again see the cheese roller bearing of the cagele~s type employed, and a double thrust bearing on the tail end of the shaft"
        ],
        "surrounding_texts": []
    },
    {
        "image_filename": "designv11_36_0002632_jiee-1.1916.0014-Figure1-1.png",
        "original_path": "designv11-36/openalex_figure/designv11_36_0002632_jiee-1.1916.0014-Figure1-1.png",
        "caption": "FIG. 1.\u20142,700-k.v.a., 3-phase Turbo-generator.",
        "texts": [
            " Thus, one of these curves is required for the part of the rotor which is uniformly slotted, and another curve is required for the polar projection, which may be regarded as one large tooth. These curves are shown in Fig. 3 and are marked F and G. In Table 1 are given the figures from which the \" airgap and tooth-saturation \" curve for the slotted part of the rotor is plotted. In these curves it is well to take as abscissae ampere-turns per pole, and as ordinates the flux density in the air-gap on the middle line, shown in Fig. 1 by the dotted circle MM. The flux density on this line may be taken as the standard from which the flux density in an adjacent tooth may be calculated. each polar projection occupying the space of five slots which are uncut. The gross axial length of the iron of the field-magnet is 115 cm.; there are 21 ventilating ducts each o-95 cm. wide, leaving a net length of iron of 95 cm. There are 14 ventilating holes, 3*5 cm. diameter. The slots are 1*9 cm. wide and 9 cm. deep. This construction leaves the teeth very narrow at the base, only 1*17 cm"
        ],
        "surrounding_texts": []
    },
    {
        "image_filename": "designv11_36_0002616_piae_proc_1916_011_012_02-Figure16-1.png",
        "original_path": "designv11-36/openalex_figure/designv11_36_0002616_piae_proc_1916_011_012_02-Figure16-1.png",
        "caption": "FIG. 16.",
        "texts": [
            " The point is that whereas in the Lanchaster type the worm thrust has to be accurately located, in the parallel type 80 long aa the worm axis is correct as to position the longitudinal location of the worm is of no importance. The matter may be carried a step further; worm gear of the parallel type in turn may be said to require more careful mounting than common screw gear, in which both worm and wheel are of the ordinary screw-cut spiral form. Thus the argument that the Hindley or Lanchester gear is at a &ad- * In the parallel type of worm it will be seen from Fig. 16b that there is very little constancy in the type of the bearing contact ; actual concavities in the teeth frequently make their appearance with no proper driving contaot. Beyond this the mere degree of convexity, although a valuable indication, ia not the whole criterion in view of the squeegee action dealt with in the discneeion of the-previous paper. Compare Proceedings 1913-14, Vol. VII., p. 279.\u201d 102 THE INSTITUTION OF AUTOMOBILE ENGINEERS. ventage, on amount of the extra precautions required, aa compsrd with parallel worm gear, may be quite as reasonably urged against worm gear of every kind in favour of ordinary screw gearing suah aa commonly used to drive the side shaft of a gas engine",
            " Hero it will be noted that the ball bearings are not of the modern type, the design dating back to a time when such bearin@ were not a s tandard id or a marketed commodity; two double bearings of the bicycle cup and cone type are arranged a t opposite ends of the worm, the whole combination being symmetrical. The cups were made adjustable by housing them within an internally screwed sleeve piece, and the adjustment was fixed by a key or cotter engaging with one of twenty-four notches cut in the periphery of each cup, Fig. 16a. The pitch of the thread was twelve per inch, so that the design gave a capacity of adjustment to within approximately three and a half one-thousandths of an inch, which 104 THE IXSTITUTLON O F AUTOMOBlLE ENGINEERS. was found to give satisfactory results in practice. Here we stumble against one of the misconceptions which are current with regard to the Hindley type of gear; it has often been represented that the accuracy of alinement of the worm requires to be true to within a thousandth of an inch of gedmetrical accuracy: 'from the sucmss of the arrangement described, it is clear that no such degree of accuracy is essential",
            ", the spiral distribution of the balls, is that each ball ma3 bear on a different part of the flattened surface, so distributing the wear; a further advantage is, that if the balls vary amongst themselves aa to diameter, as is commonly the caae, each ball will form its own race and will soon be taking its due proportion od the 10ad-h markings on the thrust r a m frequently gave evi- denoe of this action. The degree of inaccuracy amongst balls of nominally the same diameter is cowonly less than one tenthouculndth of an inch. This form of bearing waa in every, way successful and satisfactory; that it has since been dropped is due to the fact that excellent thrust bearings have now been placed on the market by specialised manufacturers. In the modern worm mounting, the type of bearing given in Fig. 16 haa been long since abandoned, and to-day it is the invariable practice to separate the functions of radial load and thrust and provide for each by a bearing speually designed Patent 17,032 of 1901. 106 THE INSTITUTION OF AUTOMOBILE ENGINEERS. for khe,purpose. Thus in%igs. 19a, 19b, 20 and 23, a roller bearing is employed independent of the thrust; in some cases this bearing is of the long-roller type, in others (Fig. 23) the \u201ccheese\u201d type iS adopted. In Figs. 24 and 26 and those which follow, it will be seen that the radial bearing also in common use is the symmetrical type of ball bearing 89 now to be obtained from several firms, such m the Hoffmann, Skefko, Duplex, etc",
            " Another incidental feature which may benoted is the fact that there axe four balance pinions in the differential gear box, each pair mounted on a transverse pin; the figures show clearly the means taken in the design of these oross pins to permit them to clear each other and to clear the axle ends and thrust pad. So far as the worm gear mounting is concerned, these are mere incidents, but the method by which the drive is conveyed from the worm wheel to the balance pinions is essentially of interat . Coming back now to the more directly important points, we may, with reference to Fig. 19a, call attention to the first advance in worm mounting after the type shown in Fig. 16. In this we see that roller bearings brought well up to the neck of the worm have been substituted for the bicycle type of bearing in the previous figure, and a double ball thrust between flat parallel races has been applied at the tail end of the worm shaft. This. design, again, was before the period in which ball or roller bearings could be purchased from specialised makers, and the bearings were made in every detail at the Lanchaster Company\u2019s works. It will be seen that.the thrust bearing in this design is very compact, but from the modern point of view and with present day loads and speeds it would not be considered adequata",
            " There are four methods open: firstly, the parts may be made with sufficient mechanical exactitude to ensure perfect interchangeability and alinement within the necessary degree of accuracy. Secondly, a screw or other variable adjustment may be provided by which the necessary alinement may be secured in spite of individual variation in the parts. Thirdly, the method of using pen steel washers or \"shims \" may be adopted. Fourthly, an accommodation piece may be employed. In the earliest type of mounting (already discussed, Fig. 16)) the method of screw adjustnient was employed, and up to a certain point was found satisfactory. I t had the wealtness, however, that, if the mountings were taken down, either the parts would have to be carefully marked, which might be forgotten, or in re-assembling an experienced hand would have to be employed,-who might not always be available. In brief, the screw adjusted mounting is not fool-proof.\" In departing A still later type of mounting is given in Fig. 23. LANCHES'l'ER. H 114 THE INSTITUTION OF AUTOMOBILE ENQINEERS",
            " Thus, the \u201csplined shaft\u201d was looked a t by some as a piece of fantastic extravagance when first introduced, but it showed itself to be a money saver from the outset; it is far cheaper to cut a splined shaft and drift the hole to correspond, than it is to cut a key way and make and fit a key; also the job is incomparably better engineering when done. I t is, perhaps, the more legitimate to cite this example since it was in connection with worm mountings that the splined shaft was first introduced into motor car practice; the worm shaft of the 10-12 h.p. Lanchaster car, Fig. 16, also the gear box, were, the author believes, the first applications of the splined shaft in the history of automobile engineering. * Returning to the main point under discusqion, it has been stated that though commercially possible, and probably advantageous, to fir the limits of the various components to secure perfect interchangeability in a worm gear mounting, it can only be done provided that the whole of the parts are made by the builders; a t least in cases such as ball or roller bearings the offending dimensions must be rectified after they have been received from the manufacturer"
        ],
        "surrounding_texts": []
    },
    {
        "image_filename": "designv11_36_0002705_scientificamerican06011901-21258supp-Figure3-1.png",
        "original_path": "designv11-36/openalex_figure/designv11_36_0002705_scientificamerican06011901-21258supp-Figure3-1.png",
        "caption": "FIG. 3.",
        "texts": [
            " 2, which is used on the overload apparatus, the retardation being accom plished by a train of clockwork operated by an ordinary spring. The brake on the clock train (which is nor mally at rest) is released by either of the two mag nets, one being connected to the secondary of a trans former in series with phase No. 1, and the other sim ilarly connected to phase No. 2, the diagram showing the connections for a two-phase circuit. Variation of the time limit is accomplished by changing the angle of the air paddles on an axis normal to the spindle driving them. . Fig. 3 shows a third type of switch which may be operated by air, controlled by a relay or by any other agency, and consists simply of a U-shaped copper rod connecting two brass cylinders, with spring sockets, filled with oil. When the U-shaped rods are withdrawn from the copper receptacles at the bottom of the cyl inders the arc is broken in oil in two places. The cut illustrates the separation of the phases by means of y./A'-U'f.HA,\\It::hUE. s .... tlo S\"'''T\ufffd''H. a direction that the contact arm attached to the armature shaft is strongly pulled against the blank stop, a spring assisting in this pull"
        ],
        "surrounding_texts": []
    },
    {
        "image_filename": "designv11_36_0002532_303-Figure3-1.png",
        "original_path": "designv11-36/openalex_figure/designv11_36_0002532_303-Figure3-1.png",
        "caption": "Fig. 3.",
        "texts": [
            " This method of producing a double image has one distinct disadvantage. Both images are slightly deformed, the one being elongated and the other compressed along the direction of displacement. It will be seen at once that this deformation is consequent on the property of the system by which oblique rays are deflected from their normal direction on emergence. Suppose that a rotation of the prisms by I minute of arc from the direction of zero separation produces a separation of The Contact Setting of Smal l Discs 189 a minutes between the images of a point. In Fig. 3 let AB represent an object of angular diameter d , the centre of which is displaced from the zero axis OP by an angle 8. T h e two images a, and a, of the edge A will d be separated by an amount a (0 - i), while the angular separation of the two images b, and b, of B will be a (0 + %) . An observer looking at the object through the prisms at P will therefore see two images, alb, and a,b,. Clearly, the angular width of a,b, = L a,PA f L APB - L b,PB = d ( ~ - z ) . Similarly, the angular width of 4 b 2 U 2 Tha t is to say, the deformation of each image is - d i n the direction of the deflection, one image being compressed to the same extent that the other is elongated, and this deformation is independent of the distance of the object from the axis, provided that the object is small"
        ],
        "surrounding_texts": []
    },
    {
        "image_filename": "designv11_36_0002547_piae_proc_1920_015_011_02-Figure17-1.png",
        "original_path": "designv11-36/openalex_figure/designv11_36_0002547_piae_proc_1920_015_011_02-Figure17-1.png",
        "caption": "FIG. 17.-Main Spindle of Special Triumph Spring Frame Machine.",
        "texts": [
            " Another deqign, which ma3 got out by the author, was the fitting of rear springing to a standard Triumph machine. There waa nothing particuhrly original ,ablaut the design, the general arrangement of which can be seen from Fig. 5. The carrier and rear mudguard wene unsprung. The spring had a flat end, with no eye or shackle, but behicd Rhe end was a CTOSS bar, which caught the spring m sebound or whlen the nmr wheel dmppe62' into a bole. The details Qf bhle main spindle bearing can be seen in Fig. 17. Grooves were turned just inside the bushes to collect any dust and mud, etc. Ithat might work in. This d<esign was simple and substantial ; facilities and time did not allow at PENNSYLVANIA STATE UNIV on June 5, 2016pau.sagepub.comDownloaded from THE SPKINGING OF BIOTOH. CYCLES. 51 of the details b,eing elaborated. It riS regretted that the author has not got particulars of the strength of the spring, etc.; from memory he woald gay $hat rthe allowable movement from the normal ww about 33 in. Pbe diffemncle bl&veern the riding 4 (4 at PENNSYLVANIA STATE UNIV on June 5, 2016pau"
        ],
        "surrounding_texts": []
    },
    {
        "image_filename": "designv11_36_0002547_piae_proc_1920_015_011_02-Figure10-1.png",
        "original_path": "designv11-36/openalex_figure/designv11_36_0002547_piae_proc_1920_015_011_02-Figure10-1.png",
        "caption": "FIG. 10.-A.B.C. Spring Frame.",
        "texts": [
            " The question is a compromise, and the author only says that if possible it would be better to arrange that suitable faces should give lateral support, and the springs take their direct load only. On the type of spring which is fittied with an eye and shackles, if the bearing in the spring eye is to work nioely, it must have some clearance on tihe sides, s o that biefore the spring clan help in the lateral stability the bearing i n which the rear fork is hinged must have worn enough for the fork to rock over and take up this clearance. In the gmthor\u2019s opinion, by the time this biearing is wjorn to that extent it ,requires renewing. In the A.B.C. type of springing, Fig. 10, the spring does give lateral support to the wheel, as it is b b h d solidly at each end to the frame and the rear fork respectively. DQaling with the eye of the leaf spring, on several makes shackle plates and pins of good proportions are employed, and on the Royal Ruby patented roller bearings as shown in the upper part of Fig. 4 are fitted to eliminate lateral play, and they should at PENNSYLVANIA STATE UNIV on June 5, 2016pau.sagepub.comDownloaded from work well. The author thinks, however, that these shackles are a refinement, and he would recommend in a great inany cases simply a flat end to the spring and no eye"
        ],
        "surrounding_texts": []
    },
    {
        "image_filename": "designv11_36_0002634_jrproc.1915.216693-Figure3-1.png",
        "original_path": "designv11-36/openalex_figure/designv11_36_0002634_jrproc.1915.216693-Figure3-1.png",
        "caption": "FIGURE 3",
        "texts": [
            " Suppose these transformations involve 2n new variables; upon (2n - 2) of them we may impose any conditions we please; this leaves two variables, the relation between which must be determined from the original equation, f (x, y) = 0. CIRCUITS HAVING INDUCTANCE, RESISTANCE, AND VARIABLE MUTUAL INDUCTANCE Turning now to Pupin's theory, we consider first the case of a circuit having resistance R, inductance L, and a constant impressed e. m. f., E.; in the field of this circuit is rotated another circuit having resistance S and inductance N. For any angle 0 between the coils, the mutual inductance is given by M cos 0. (See Figure 3.) In the first circuit, the reactions are the in- ductance reaction Ldx, the resistance reaction Rx, and the d e. m. f., Md (y cos w t) due to the presence of the rotating circuit. In this latter the reactions are the inductance reaction N d t Y the resistance reaction S Y, and the e. m. f. due to thed t d presence of the stator circuit, M ddt (x cos w t). (Thruout this paper, x shall denote the current in the stator, y the current in the rotor, and (o the angular velocity of rotation.) The equations of reactions therefore are: dLt+Rx+M"
        ],
        "surrounding_texts": []
    },
    {
        "image_filename": "designv11_36_0002634_jrproc.1915.216693-Figure1-1.png",
        "original_path": "designv11-36/openalex_figure/designv11_36_0002634_jrproc.1915.216693-Figure1-1.png",
        "caption": "FIGURE 1",
        "texts": [
            " CIRCUIT HAVING YARIABLE INDUCTANCEIANDINO RESISTANCE It will be helpful, perhaps, before considering Pupin's problem, to take up a simple, hypothetical case first, viz., a circuit having a periodically varied self-induction and no resistance. Imagine a circuit made up of two coils connected in series, the one having inductance L1, the other inductance L2, and let M be the maximum value of the mutual inductance between the coils. When they make an angle 0 with each other, the mutual inductance between the coils is M cos 0. (See Figure 1.) Let the- circuit be supplied with a source of constant e. m. f., E (e. g., a battery), and let R be the resistance. If one of the coils is continuously rotated with angular velocity (o, the total self-induction of the circuit will vary periodically in accordance with the equation L = L1 + L2 + 2 M cos co t. * Delivered before the Institute of Radio Engineers, New York, May 5, 1915. The inductance reaction will therefore be dt(Li + L2 + 2Mcosot)x], where x is the current in the circuit at any instant"
        ],
        "surrounding_texts": []
    },
    {
        "image_filename": "designv11_36_0002756_paiee.1906.6742509-Figure15-1.png",
        "original_path": "designv11-36/openalex_figure/designv11_36_0002756_paiee.1906.6742509-Figure15-1.png",
        "caption": "FIG. 15.-Hysteresis loops corresponding to Figs. 10-13. () greater than 30\u00b0",
        "texts": [],
        "surrounding_texts": [
            "DATA RELATIVE TO CURVES IN FIGS. 5 - 1 3 . Curve N o . Q P a 0 I I ' 5 0 \u00b0 0 111 0 \u00b0 0 \u00b0 1 . 0 0 6 0 . 8 8 9 0 6 2 \u00b0 0 122 16\u00b0 5 4 ' 17\u00b0 1 . 0 0 7 0 . 8 8 3 2 7 5 \u00b0 0 135 2 2 \u00b0 4 8 ' 2 3 \u00b0 1 . 0 0 9 0 . 8 8 3 3 8 2 0 \u00b0 0 172 29\u00b0 2 9 \u00b0 3 0 ' 1 . 0 1 5 0 . 9 2 5 0 9 3 0 \u00b0 0 193 2 9 \u00b0 3 3 ' 3 0 \u00b0 1 . 0 1 9 0 . 9 6 2 4 10 4 5 \u00b0 0 2 2 0 2 8 \u00b0 3 8 ' 2 9 \u00b0 2 2 ' 1 . 0 2 4 0 . 9 8 6 8 11 9 0 \u00b0 0 283 19\u00b0 3 6 ' 2 0 \u00b0 3 0 ' 1 . 0 3 9 1 . 1 8 5 0 12 135\u00b0 0 321 10\u00b0 1 2 ' 10\u00b0 4 5 ' 1 . 0 5 0 1 . 2 9 5 0 13 180\u00b0 0 333 0 \u00b0 0 \u00b0 1 . 0 5 3 1 . 3 3 3 0 6 is the phase relation of the third harmonic to the fundamental at the origin. [3 is the ratio of the maximum ordinates of the fundamental and third harmonic (critical value). (p is the phase difference between the max ima of the distorted and fundamental curves. 90 -(j) is lag of fundamental component of current behind e.m.f. 9 0 - (X is lag of equivalent sine current behind e.m.f. 7 and I' are the maxima of the equivalent sine curve and distorted curve, respectively, ths maximum value of the fundamental being unity. The amount of shifting to the left of the fundamental (the hysteretic advance) , is readily observed in each case, this being (p. The hysteretic angle (J> increases with hysteresis loss, the power-factor for hysteresis being cos <Jf. In Figs. 5 and 13, for 6 = 0 \u00b0 and 180\u00b0, <p is 0 and the maxima of the fundamental and complex waves are coincident; hence power consumed b y hysteresis is zero. The corresponding hysteresis loops for all cases are shown in Figs. 14 and 15. Loops 5 and 13, for 6 = 0\u00b0 and 0 = 180\u00b0, have no area, which likewise indicates that the power consumed by the hysteresis is zero. Curves shown in Figs. 5 to 9 are for various values of 6 equal to or less than 30\u00b0, the corresponding hysteresis loops being shown in Fig. 14. The upward turn of these loops, when 6 is less than 30\u00b0, shows these cases to be impossible; for they would indicate an increase instead of decrease in the permeability for increasing values of induction beyond saturation. Possible values of 6 must accordingly be between 30\u00b0 and 180\u00b0. 6 1 0 BEDELL AND TUTTLE: [Sept. 2 8 612 BEDELL AND TUTTLE: [Sept 28 1906.] ALTERNATING-CURRENT WAVE FORM. 613 614 BEDELL AND TUTTLE: [Sept. 28 R E L A T I O N B E T W E E N A R E A O F H Y S T E R E S I S L O O P A N D A N G L E O F H Y S T E R E T I C A D V A N C E . Since only the fundamental in the current wave represents power, and the harmonics are wattless, we have the same power represented b y the fundamental as by the complex wave. Hence if values of H be taken from the fundamental current curve, and a hysteresis loop plotted, it will have the same area as though H were taken from the complex wave, as was done in deriving the loops in Figs. 1 4 and 1 5 . In this case, however, with H as well as B sinusoidal, the hysteresis loop would form an ellipse, the area of which can be shown* to be A = t t XY sin <p. Here X and Y represent the max imum values of the sinusoidal magnetizing force H and induction By respectively. A s has just been shown, the area of this ellipse can likewise be taken as the area of the loop when the complex wave of cur rent is taken. It at once follows that S m ^ \" t t XY~ 7T ' X'Y' X ~ \\ ' X' Y'F ' Here F is the max imum value of the fundamental and l f the max imum value of the complex current wave ; X and X' being corresponding values of magnetizing force. Xf Y is the area of the rectangle enclosing the hysteresis loop . A I' For write p; and for write / . X'Y, F ' For any hysteresis loop the value of the hysteretic advance may then be derived from the following expression: Sin <J>=pf/7t, * Let the induction and magnetizing force be respectively y = Y sin a) t and x = X sin (cot \u2014 (J>). Plotted in rectangular coordinates, the resulting figure will be an ellipse. Its area (see translation of Goursat's Mathematical Analysis, p. 185) will be A= J / (xdy\u2014ydx). J o = \u00a7J X Y {sin 0) t cos (co t\u2014 <[>)\u2014 sin (oj t\u2014 (J>) cos o) t} oj d t X Y P27Z = / (sin2 co t sin </> + sin cp cos 2 cot) codt 2 U o = 7T X Y sin i[>. 1906.| ALTERNATING-CURRENT WAVE FORM. 615 where p is the ratio of the area of the hysteresis loop to the en closing rectangle, and / is a form-factor\u2014the ratio of the max imum values of the complex and fundamental current waves. If the result depended upon p only, hysteretic advance could be readily and directly determined from area of the hysteresis loop. The results are modified, however, b y the presence of / , which is unsatisfactory, for it makes the direct determination in t l i s way impossible. Table II gives values of / ' for curves 5-13. b P ' / / / / B - \u2022 -j/^ s ' vf Q i ^ ^ ^ ^ ^ F I G . 16.\u2014Vector representations in three dimenions of a complex current. E is sine electromotive force; F is fundamental current; Q 3 , harmonics; and 2\" is the equivalent sine current. V E C T O R R E P R E S E N T A T I O N O F C O M P L E X C U R R E N T . Without iron, where current as well as electromotive force is sinusoidal, as shown in Fig. 1, the vector representation of these quantities as lines in a plane is well known. Let us take, however, such a case as shown in Fig. 2, in which the electromotive force E is sinusoidal and the current / , on account of iron, is complex , being composed of a fundamental F and third harmonic Q 3 . Considering first the fundamental F, this may be considered as composed of two components , Fig. 16, a power component 616 BEDELL AND TUTTLE: [Sept. 28 P in phase with E, and a quadrature or wattless component Q1 at right angles to E\\ that is,F = x / P * + Qi 2 . These quantities E, F, P, and Qi are all sine functions of the same frequency and are graphically represented in one plane. The induction B is in the direction of Qv and is also a sine function of fundamental frequency. The fundamental F lags behind E by an angle 9 0 \u2014 0 (as in Fig. 2 ) ; 0 is the angle between Qt (or 5 ) and F. In Fig. 16 and its discussion all quantities represent virtual or square root of mean square values. The harmonic Q3 has no power component in phase with E\\ it is entirely wattless, as has been shown, and hence is to be represented graphically in quadrature to E. But it may be shown* that I = \\ /pz + Q*^ which corresponds to a graphical construction in which Q3 and F are two sides of a rectangle and / the diagonal. As Q3 is thus at right angles to both E and F , it is drawn in the third dimension at right angles to the plane of fundamental frequency in which lie E, F, P, and Qv The total current is / , the diagonal of the rectangular parallelopiped. / is the equivalent sine wave representing the com plex current. In phase it is as represented in Fig. 16, lagging behind E b y an angle 90 \u2014 a. In magnitude it is such as to have the same square root of mean square value as the complex wave. W e have seen that 1 = VF\u00bb + Q,\u00bb;~ W e also have In the usual treatment confined to one plane, the plane taken is the diagonal one in which lie E and / . The equivalent sine current / may be resolved into a power component P of funda mental frequency in phase with E, and an equivalent wattless component Q at right angles to E. The component Q is itself complex, consisting of two components each wattless; namely, 0 ! of fundamental frequency and the harmonic Q3. We have then 0 = VQJ+Q^, and / = \\ / p 2 + Q 2 . Power is the product of E and P. Considering the funda mental sine curve, we have for power in terms of F: W = EF cos ( 9 0 - 0 ) . *This is independent of the phase position 0 of the harmonic. See F. Bedell, \"The Principles of the Tranformer,\" p. 391. 1906.] ALTERNATING-CURRENT WAVE FORM. 617 If we consider the equivalent sine curve, we have for power in terms of 7: W = EI cos ( 9 0 - a ) . Each is correct, the two expressions being practically identical. A n error (numerically small) would be made b y confusing the fundamental and equivalent sine curves, and interchanging the values of JF and I, or of (p and a. It is seen that sin a _ F F sin (p ~ I ~ VF* + Q*B For the curves in Figs. 5-13, the values for a and <p are given in Table I I ; also / , the max imum value of the equivalent sine wave. In constructing the curves, F has been taken as uni ty ; then Q 3 = /? (see table). The graphical construction of Fig. 16 will include the rep resentation of higher harmonics if we include them all in Q 3 ; that is, in place of Q 3 w e should have Qx = y/Q3 2 + Q& 2 . . . Qn 2. Separately and collectively the harmonics are wattless, and are at right angles to both E and F. Their separate representation in three dimensions is not possible; for, in addition to being at right angles to E and F, each one should be at right angles t o each other one, requiring an additional dimension for each harmonic above the third. This representation is, however, unnecessary, for, since all are wattless, their collective representation as one line, Q 3 , meets all requirements. If we are to represent all quantities in one plane only, the vector representation is correct for each frequency, and for the equivalent sine curve separately; components of different fre quencies so drawn are not to be combined vectorially, but are to be added b y taking the square root of the sum of the separate squares. C O N C L U S I O N . W e conclude that an alternating current is distorted when iron is present b y the introduction of a third harmonic in ad vance of the fundamental b y an angle 0 which is greater than 30\u00b0 and less than 180\u00b0. Taking the fundamental as unity, this harmonic cannot ex ceed a definite value (see Table I) of about 0.192 for 6 = 30\u00b0, and 0.333 for 0 = 180\u00b0. The angle (p of hysteretic advance due to the third harmonic cannot exceed 30\u00b0. 6 1 8 BEDELL AND TUTTLE: [Sept. 2 8 From the shape of the hysteresis loop obtained from the third harmonic only, it is concluded that iron introduces higher harmonics in addition to the third. Three dimensions, as Fig. 16, are required for the vector representation of the complex current wave. A P P E N D I X . * R E L A T I O N B E T W E E N 6 A N D / ? . W e wish to find the condition which holds at the transition state, Fig. 19, separating the impossible case of two maxima W e proceed to find the condition imposed upon 6 and /? so that the graph of f (t) = sin co t + {3 sin (3cot + d) shall have no trough or minimum in the first half cycle. * Due to Professor James McMahon. 1906. ] ALTERNATING-CURRENT WAVE FORM. 6 1 9 By differentiation we have /'(t) a; [cos to t + 3 ft cos (3 <ot + 0)] = 0, hence the positions of the crests and troughs are given by the equation cos cot + Sp cos (3wt + d) = 0. We shall find the condition that this equation may have two roots equal; and, subject to this condition, we shall find the next roo t ; this will give the position of the only proper crest or max imum in the first half-cycle. For convenience let 9/? = 1/a and write x for cot. Then cos (3 x + 0) + 3 a cos x = 0. That is cos 3 x cos 0 \u2014 sin 3 x sin 0 + 3 a cos x = 0. Therefore (4 cos 3 x \u2014 3 cos x) cos 0 \u2014 (3 sin x \u2014 4 sin 3 x) sin 0 + 3 a cos x = 0. Dividing through b y cos 3 x we have (4 \u2014 3 sec 2 x) cos 0 \u2014 (3 tan x sec 2 x \u2014\u2022 4 tan 3 x) sin 0 + 3 a sec 2 # = 0 620 BEDELL AND TUTTLE: [Sept. 28 a ac \u2014 b2 For our cubic the condition for equal roots becomes - 4 ( a 2 - 2 a cos 0 + 1) (3 a 2 - 2 a cos 6 - 1) = (4 a sin 0 ) 2 , whence . 3 a 4 + 6 a 2 - l C 0 S ^ 8 ^ ; (2) and the expressions for the roots become 2 a sin 0 tan xx = tan x tan#o = a 2 - 2 a cos 0 + 1 ' (3) 3 (a \u2014 cos 0) 4 a sin 0 sind a 2 - 2 a cos 0 + 1' (4) With the aid of (2), the last expression reduces to ( 1 - a 2 ) (1 + 3 a 2 ) 8 a 3 sin 6 It is convenient to let \u2014 = b, then 6 = 9 / ? , and a ( 6 2 - l ) ( 6 2 + 3) tan 8 6 s i n 0 ' (5) wherein 6 is given b y (2) , or by \u201e 3 + 6 W-B* C O S 0 = \u2014 b , ( 6 ) or fin a form better adapted to logarithmic computat ion) Replacing sec 2 x b y 1 + tan 2 x, we get the following cubic for tan x: sin 6 tan 3 x + 3 (a \u2014 cos 5) tan 2 # \u2014 3 sin 6 tan # + (3 a + cos 6) = 0. N o w it is known in the theory of equations that the cubic (1) ax3 + 3bx2 + 3c x + d = 0 has two equal roots when 4 (a c - b2) (b d-c2) = (ad-b c)2, the equal roots being given b y b c \u2014 a d and the third root b y 3 6 bc \u2014 ad 1906.] ALTERNATING-CURRENT WAVE FORM. 621 This equation, wherein 6 = 9 / ? , gives the desired relation be tween 6 and /?. If we assume a given value of 0 and solve for /?, the value so obtained would be the greatest value of /? that could be used with the. given value of 6 without obtaining a trough as in Fig. 17, which corresponds to the impossible hys teresis loop of Fig. 18. T o determine 0, the phase displacement of the crest, we pro ceed as follows: Eliminating sin 0 from (5) by means of (7) we obtain t a n x = 6 2 + 3 a n % * V ( 6 2 ~ l ) ~ ( 9 - 6 2 ) ' (8) Hence the position of the crest is given b y 6 2 + 3 to t= 7i \u2014 t a n 1 \u2014 ; \u2014 \u2014.. / n \\ V ( 6 2 - 1) ( 9 - 6 2 ) W Now the crest of the fundamental curve (y = sin to t) is given by to tx = \u2014 . Hence the displacement of the crest due to the presence of the third harmonic is given by * - \u201e ( , - , , ) - T - tan- ( 1 Q ) wherein 6 = 9 / 9 . This gives 0 in terms of /?, when 0 is deter mined as in (7) . Sincenei ther (7) nor (10) is readily solvable for 6, it is best to assign values to 6 and compute corresponding values for 6 and tp. Equation (7) shows that 6 cannot be less than 1 nor greater than 3; and equation (6) shows that 6 = 1 corresponds to 0 = 0, and 6 = 3 to 6 = n. Table I gives values of 0 and <J> computed from (7) and (10), by letting 6 run from 1 to 3 at convenient intervals, not always equi-distant. The corresponding values of P run from 0.111 to 0.333. Cornell University, June, 1906."
        ]
    },
    {
        "image_filename": "designv11_36_0002575_t-aiee.1914.4765196-Figure17-1.png",
        "original_path": "designv11-36/openalex_figure/designv11_36_0002575_t-aiee.1914.4765196-Figure17-1.png",
        "caption": "FIG. 17 FIG. 18",
        "texts": [
            " The object of the archoid is to obviate, as much as possible, the necessity of graphical methods: the time-speed curve is plotted from actual observations, then the constants are derived from it and, finally, the acceleration is found by substituting the latter into the corresponding formula. But, in some cases, especially where motion in general is considered (and not only the starting or accelerating period), it is necessary to use graphical methods, and in this connection a few words may be mentioned here regarding the integral curve, which is so useful in such investigations. In fact this curve can be used in many branches of engineering, but we shall limit ourselves to its application to the time-speed problems. A curve B (Fig. 17), of which any ordinate y represents to some certain scale the area of another curve A, corresponding to the same abscissa x, is called the integral curve of the proposed curve A. Conversely, A is called the differential curve of B. Being given either curve we can readily construct the other curve, as will be presently explained. It will be easily seen that, in our original problem, the archoid, or in general the time-speed curve is really the integral curve of the time-acceleration curve; on the other hand this same time-speed curve is the differential curve of the timedistance curve (we mean distance in general, that is, in angular sense for rotation and in lineal sense for translatory motion)"
        ],
        "surrounding_texts": []
    }
]