designv11-10.json

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        "image_filename": "designv11_10_0000005_1.1707241-Figure2-1.png",
        "original_path": "designv11-10/openalex_figure/designv11_10_0000005_1.1707241-Figure2-1.png",
        "caption": "FIG. 2. Forces acting on the journal as the result of the pressure distribution in the lubricating film when the source is at the crown of the bearing.",
        "texts": [
            " On the other hand, a and fJ are essentially determined\" by q and {3, which involve the source strength, lubricant viscosity, and journal speed. To establish these relationships we impose on the load com ponents the conditions that their resultant be along the vertical and have a magnitude equal to the journal load. In applying these conditions one must treat separately each position of the lubricant source. In this paper we shall consider only the cases where the source is either at the crown or base of the bearing. SOURCE AT BEARING CROWN Since the polar axis is vertical for this case (d. Fig. 2), the a~~ve-mentioned conditions to be imposed on the load components clearly become (20) where r2W is the actual load on the journal. Eliminating (3 from these equations, and introducing the dimensionless flux strength, (21) one finds 7rg{ 4(1- 2e-wo) cos a+1](3 -8e-wo) cos 2a+ fJ2 { -~-~ cos 2a+ 16e-wo/2-12woe-wo/2 -( 8-~ cos 2a)e-wo+3Wo(2+COS 2a)e-wo-4(4-9Wo)e-3Wo/2+P2/7rq} cos a +fJ2{ -~+ ~e-wo+3woe-wo} sin a sin 2a]= -(1+17 cos a)3 cos a. (22) Fixing the values of Wo and 17, one may compute numerically6 from this equation the relation between go and a",
            " On the other hand, the effect of the lubricant source comes about through its action in tending to depress the journal, thus opposing the journal supporting force due to the journal rotation. Since the latter increases with increasing eccentricity, it is necessary to have a higher journal eccentricity in order to support a given load when the lubricant source opposes the load-carrying pressures caused by the ro tation. 52 These variations of 1/ with S, qo and w may also be interpreted in terms of individual forces acting on the journal because of the pressure distribution in the film. As indicated in Fig. 2, these may be resolved for small eccentricities into a force: R=21r{31/(wo-tanh wo), which is caused by the rotation of the journal and acts normal to the line of centers; a force: F= 41rq(1- 2e-wo ) acting in the direction of the lubricant inflow and representing the effect of the lubricant source on a journal which is concentric with the bearing; and finally a force: T=1rq1/(3-8e-wo) due to the lubricant source and the eccentricity of the journal, and which acts downward on the journal and is inclined to F by the angle a",
            " Thus all the curves show load-carrying capacities appreciably less than that for the infinitely long journal bearing, the deviation from the latter increasing as the bearing lengths are decreased. This is, of course, to be expected in view of the great importance of the \"end effects,\" or fall in the pressure distribution to atmospheric at the bearing ends, as the bearings become shorter in length. Moreover, the source of lubricant is seen to cut the load-carrying capacity still further, this effect increasing as the source strength increases. The reason for this behavior lies in the journal depressing force F (d. Fig. 2), which is proportional to the source strength and acts in the direction of the lubricant inflow. If the source were to be placed at the bottom of the bearing, the component F, as we shall see JOURNAL OF APPLIED PHYSICS [This article is copyrighted as indicated in the article. Reuse of AIP content is subject to the terms at: http://scitation.aip.org/termsconditions. Downloaded to ] IP: 129.174.21.5 On: Sun, 21 Dec 2014 16:10:19 later, will tend to support the journal, and thus increase the load-carrying capacity of the lubri cating film, except at high source strengths"
        ],
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    },
    {
        "image_filename": "designv11_10_0000030_piae_proc_1935_030_039_02-Figure9-1.png",
        "original_path": "designv11-10/openalex_figure/designv11_10_0000030_piae_proc_1935_030_039_02-Figure9-1.png",
        "caption": "Fig. 9 .",
        "texts": [
            " Taking for the purpose of illustration the extreme case of a car pivoting on the front axle and only sprung at the rear, i t is of interest to examine the conditions when such a car passes over a hummock in the road, such as a culvert known to the French as a dos d\u2019dne. The rear part of the body may be thrown up till all the weight is taken offdhe spring and even beyond, then, on its return, even if the spring is inactive in the downward direction, the conditions are no better than in the case of a beam hinged or supported at the one end and allowed to fall under the influence of gravity. There is a point X on the beam, Fig. 9, known as the centre of percussion which will fall with an acceleration = g, and all points nearer the hinge point will have a less downward acceleration than g, and those beyond will have a greater acceleration; in this latter region any body or article resting on the beam will be left behind. This is what sometimes happens to a passenger, and, in a closed car, the roof gives him a crack on the head. Passengers have actually been \u201c knocked out \u201d (stunned) in this manner. The only cure for this is that the passengers\u2019 seat shall not be placed beyond the centre of percussion"
        ],
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    },
    {
        "image_filename": "designv11_10_0001393_pime_proc_1933_125_023_02-Figure5-1.png",
        "original_path": "designv11-10/openalex_figure/designv11_10_0001393_pime_proc_1933_125_023_02-Figure5-1.png",
        "caption": "FIG. 5.-Load-Extension Diagrams for specimens from web and boss of wheel centre.",
        "texts": [
            " There can be none, however, regarding the part which is weakest due to manufacturing processes. In order t o get some idea of the extent by which the elastic limit and yield point of the web material had been raised by rolling, tensile tests were carried out on test pieces taken from the web and boss of a wheel centre. This centre was not made from any of the casts previously considered, The positions from which the test pieces were taken, together with the load-extension diagrams of the material are shown in Fig. 5. Values of the tensile breaking strength, elastic limit, and yield point are given in Table 2. It is evident that a force fit allowance based on the results obtained from test pieces taken from the web will lead to an excessive over-strain of the wheel boss and a consequent diminished grip between the elements on assembly. at The University of Auckland Library on June 5, 2016pme.sagepub.comDownloaded from DEC. 1933. FORCE, SHRINK, AND EXPANSION FITS. 505 It may be well, at this stage, in view of the experiments to be described later, to consider the fit allowances employed and the magnitude of the stresses induced in an important shrink fit assembly, such as a built-up marine crankshaft"
        ],
        "surrounding_texts": []
    },
    {
        "image_filename": "designv11_10_0000005_1.1707241-Figure1-1.png",
        "original_path": "designv11-10/openalex_figure/designv11_10_0000005_1.1707241-Figure1-1.png",
        "caption": "FIG. 1. Cross section of a complete journal bearing system.",
        "texts": [
            " Moreover, when the source is set at the base of the bearing, the friction coefficient curves for both the bearing and journal, when plotted against the Sommerfeld variable, alI go through the origin in contrast to the infinitely long bearing theory where the coefficient of friction on the journal has a unit friction axis intercept. From the hydrodynamic point of view there are therefore no minima in the curves, or suggestions of thin film friction rises when the lubricant source is at the base of the bearing. equation for the pressure distribution in the film of the lubricant, namely, \\7. (~\\7P) = U ah, i21! 2r ao (1) where h is the film thickness, I! the lubricant viscosity, p the pressure in the film, U the sur face velocity of the journal, r the journal radius, and 0 the azimuthal coordinate (cf. Fig. 1). In order to derive results valid for any position of the lubricant source, it will be convenient to consider the lubricant source as fixed, so as to define the origin of the coordinates, and to suppose that the line of centers of the journal and bearing is tilted with respect to the source by the arbitrary angle a. In this system the film thick ness will be given by h=c+e cos (0- a), (2) where c is the radial clearance and e the journal JOURNAL OF APPLIED PHYSICS [This article is copyrighted as indicated in the article"
        ],
        "surrounding_texts": []
    },
    {
        "image_filename": "designv11_10_0000030_piae_proc_1935_030_039_02-Figure53-1.png",
        "original_path": "designv11-10/openalex_figure/designv11_10_0000030_piae_proc_1935_030_039_02-Figure53-1.png",
        "caption": "Fig. 53",
        "texts": [],
        "surrounding_texts": [
            "(BIRMINGHAM CENTRE.) Mr. Maurice Olley (U.S.A.), in opening the discussion, said : I want to tell as simply as possible how we came to adopt independent suspension on General Motors cars,-why we did it, and some of the advantages which we have found in the design. In trying to cover the subject briefly, I am going to seem to clash with the author in several points, but the differences are principally in viewpoint and terminology. For instance, what he refers to as F, 1 refer to as R= K1 - A B. I have talked that way for so long that I cannot break myself of thehabit. I t may be shown that the basic riding quality of a car (or its \" action \" ~~ on the road) depends on :- ( I ) The static deflections of the suspension, front and rear. (2) The K*/A B ratio (see Fig. 62). (3) The position of the centre of gravity along the length of the (Also, of course, in practice on the placing of the passengers within the vehicle: for example, the passengers on the roof of a bus are not well placed to get a good ride.) We built for ourselves a small model, such as shown in Fig. 63. Mr. Olley had such a model with him, and used it for demonstration. Springs A and B are of various rates. wheel base. Weights C and D are adjustable Light wires are fixed to the ends of the rod as a means along the rod E. Fin. 62. toward finding the oscillation centres. This model contains all the elements mentioned above. The static deflections can be changed by changing spring rates or by shifting the weights so as to change the load on the springs. The K*/A B ratio can be changed by moving the weights equally inward or outward along the rod, and the position of the centre of gravity can be changed by moving the two weights together along the rod. The rod is so proportioned that when the weights are approximately in line with the springs the KZjA B ratio is equal to I. at UNIV CALIFORNIA SAN DIEGO on September 1, 2015pau.sagepub.comDownloaded from MOTOR CAR SUSPENSION A N D I N D E P E N D E N T SPRINGING. 753 A s set up in Fig. 63, the model represents pretty closely a typical motor car suspension of 1933. The centre of gravity is centrally located, the K*/A B ratio is about 0.6 to 0 . 7 , and the front spring deflection is half the rear. When the typical combined motion of the model is excited it is seen that the rear or softly-sprung end partakes of ,: jerky motion which is really due to the interference or \" heterodyning of two simple harmonic motions of widely dissimilar frequencies. When this motion of the rear end is shown to people, they generally say, \" Yes, we have sat there ! \" We look upon this \" interference kick \" or \" whiplash \" effect as typical of the riding action at the rear end of cars with stiff front springs. I think that there is a difference in terminology between the author and myself in what we call \" bounce \" and \" pitch.\" The reason I refer to fixed oscillation centres can be seen from the model. What I call bounce is this simple harmonic motion occurring about a centre outside the wheel base, which in a car sprung like the model is approximately a t the front bumper. I t is typical of these centres that they are interchangeable, so that if the model is struck at the bounce centre it will produce pure pitch, and vice uevsh. The pitching, as can be seen on the model, occurs about a centre which is within the wheel base, but back of the centre of gravity. It is the combination of these two motions which produces the interference kick at the rear end which can be seen. The sort of ride obtained obviously depends on the frequencies of the two motions. If they are very nearly the same, the sudden interference kick of the first set-up becomes modified to a slow \" beat \" of the form LANCHESTER. 48 at UNIV CALIFORNIA SAN DIEGO on September 1, 2015pau.sagepub.comDownloaded from 754 THE INSTITUTION OF AUTOMOBILE ENGINEERS. (Mr. Maurice Olley.) indicated in Fig. 64, and the energy of the oscillation can be seen to be slowly being transferred from one end of the car to the other alternately. But if the two frequencies are very dissimilar the interference may be roughly of the form shown in Fig. 65, which is intended to be a rough picture of what is actually seen in the model. I t therefore appeared to us that a fundamental improvement in riding quality depended on making the pitch and bounce frequencies more nearly alike. Previous to this time it had been put forward by a great many people that the solution of the problem of riding quality was to so proportion the masses of the car and the length of the wheel base that the Kz/A B ratio should he equal to I . This can be demonstrated on the model by sliding the weights outwardly until they are approximately in line with the springs. The proof that this ratio has been attained is that the oscillations of the two ends are independent of each other, as mentioned by the author in the paper, and as demonstrated here. It can be seen from the model that, although the kick has been improved by increasing the Ka/A B ratio, it is still there, and the motion of the model is still not smooth. The better solution appears to be along the lines which can be demonstrated on the model by making the springing of the two ends of the car equal. The bouncing motion of the car is now truly parallel, z.e., the bounce centre has moved off to infinity, and the pitching now occurs about the centre of gravity, which in this case is the centre of the wheel base In the particular case where the springing is equal and at the same time the liZ/A I3 ratio is equal to I , it will be noticed that any motion which is given to the model will continue almost indefinitely, that is, there are no fixed oscillation centres, and only one frequency is present in the - - - suspension. But actuallv in the larger cars the K2/A B ratio is about 0 . 8 , and it is seen from the model that there is a slight interference in the form of a slow beat, such as indicated in Fig. 64. I t is an interesting fact that under these particular conditions of springing (equal front and rear) the ratio of pitch frequency to bounce frequency is J\u2018$ . Thus if the KZ/A B ratio is 0.8 the pitch frequency is actually only IZ per cent faster than the bounce, so that no violent interference kick can occur. Such demonstrations with a model are all very well, but tho natural criticism is that these may not represent anything veal in a car on the road. The next step was obviously to conduct similar tests on an actual car. A large seven-passenger car with the rear seat well overhung over the back of the axle (in arder not to make things too easy for ourselves) was fitted with front and rear \u201c outriggers,\u201d on which 60 lb. cast iron weights could be locked by set screws.* These weights were normally stored in a box just a t the back of the front seat. There were twelve of them, or a * For an illustration, see S.A.E. Journal, March, 1934. page 79 at UNIV CALIFORNIA SAN DIEGO on September 1, 2015pau.sagepub.comDownloaded from MOTOR CAR SUSPENSION A N D I N D E P E N D E N T SPRINGING. 755 total weight of 720 lb. The outriggers were so positioned that the weights were carried front and rear a t an equal distance from the box. Therefore when two weights were taken out of the box and attached one to the front and the other to the rear, the weight distribution had not been disturbed, but the m a s s distribution or K2/ .I B ratio had been increased. Various rates of front and rear springs were fitted, and were tested on the actual car by pulling down the front and rear ends on platform scales and measuring deflection from the bumpers. The KZ!A B ratio was also checked with various weight distributions by swinging the whole car as a pendulum from the roof girders and then deducting the unsprung masses in the usual way. We thus had a device in which we could at will :- ( I ) Change the K2/A B ratio without disturbing any other charac- ( 2 ) Change the position of the centre of gravity and the deflection By starting out with various spring rates, we could separate out the relative value of the above two effects, i . e . , find the effect of moving the centre of gravity and of changing the relative front and rear deflections independently. As might be expected, the relative spring deflection is vastly more important than the movement of the centre of gravity. With very little time or trouble, we could thus reproduce any desired condition of the model on the complete car, and we found, as might be expected, that the motions of the car and of the model were similar. The only important difference was that whereas equal deflections a t the two ends are best on the model, the car requires a slight bias in favour of the front springs to produce similar results, i . e . , the front deflection should be somewhat greater than the rear to produce a \" flat \" ride. The reason for this is certainly due to the sequence of blows received by the car which is disturbed first a t the front suspension and then a t the rear. This car was run under these conditions for several thousand miles. Far enough, in fact, for us to become very familiar with the problems which would arise under our desired \" optimum \" conditions of suspension. We proved to our own satisfaction that if a car was to be as softly sprung in front as we desired, so that it rode \" flat,\" it must have something better than our then-accepted ideas of steering geometry. The need of an accurate steering geometry is not so much to give proper control of the car on really rough roads, but to avoid the car swerving sideways when driven fast over long \" donkey-back \" waves, such as are provided in the United States a t grade crossings. We also shou-ed the desirability of eliminating or greatly reducing the dry-friction of the front suspension. Soft springing is very readily spoilt in its effect on riding quality by relatively small amounts of dry-friction. We started therefore to build independent suspension with the idea of combining two effects, first, to obtain an accurate steering in conjunction with soft springing, and, secondly, to eliminate or control dry-friction. A further benefit which could be obtained by the design was to bring the engine forward more or less between the front wheels. Thus we could move the whole car forward on its wheels, so as to fill up the space-wasting \" box canyon \" that we had always had between the front frame horns, and at the same time move the rear passengers into a better position relative to the front wheels without lengthening the wheel base, and thus reducing our Ka/A B ratio. The author has asked why on the \" wishbone \" type of independent suspension the upper arm is made shorter than the lower. This necessity of moving the power unit forward is, of course. a direct reason for the teristic. of the front and rear springs simultaneously. 48 ( 2 ) at UNIV CALIFORNIA SAN DIEGO on September 1, 2015pau.sagepub.comDownloaded from 756 THE ISSTITCTION OF AUTOMOBILE EKGIKEERS. (Mr. Maurice Olley.) difference in length, and whereas we should not do this if there was any disadvantage in it, we are not above finding some good excuses for it, now that it is done ! It is a fact that if the arms arc horizontal together, and if their lengths are inversely as their height from the ground, the tyre contact will move up and down vertically without lateral \" scrub.\" However, the direct relation between moderate lateral scrubbing of the tyre and wear o f the tread is not very marked. I t is probably of greater importance that the heavily-loaded outer wheel on a corner does, with arms of unequal length, hold itself a t a slightly more favourable angle relative to the ground, due to the fact that the wheel motion up and down is not truly in vertical planes. On heavier cars this does have a measurable benefit in steering effort, without going so far as to produce the gyroscopic reactions associated with '' shimmy \" on a conventional front axle. A feature which has not previously been pointed out, I believe, is that on transverse link suspensions of the wishbone type, if equal links are used above and below, the tyre contact moves in a curve which is concave towards the centre of the car. Under lateral forces on corners there will in such cases be a definite toggling action, tending to reduce the stability of the car on turns. There are therefore \" good and sufficient reasons \" for arms of unequal length, besides the obvious one of space for the upper arm, or the other obvious one of a long lower arm being necessary for use with a coil spring. The first experimental cars which we built had independent suspension, both front and rear. They served to bring out the very definite tlistinction between the two ends of the car, so that a type of wheel motion which is desirable in front need not by any means be acceptable on the rear. We found also that a parallel action front independent has a very definite effect in improving the handling of the car, and this started us of f on a whole new line of investigations to find in what way a tyre pushes a car round a corner. Most of the laboratory work on these tyre characteristics had been put in hand a year before by The Goodyear Tyre and Rubber Co., and as they are fully covered by Mr. R . I). Evans in his S.A.E. paper,* they need not be repeated here. Briefly, the tyres (both front and rear) steer the car much more like the rudder of a ship than like a curved railway track, and the side force produced by a tyre running with a known \" slip angle\" can be ascertained a t least as accurately as the lift of an airfoil at a given angle of incidence. Not onl; the \" slip angle \" of the wheel in plan view, but also the \" camber angle of the wheel relative to the ground in front elevation, both produce side thrust. Changing the \" camber angle \" of the wheels relative to the ground in the direction in which they change on a parallel action independent in rounding a corner, slightly reduces their ability to make the turn. The amount of reduction is small and can be ascertained by the following rough figures. Side thrust due to slip angle is about 7 to 10 lb. per IOO lb. of load per degree of angle. Negative side thrust due to camber angle is about I & lb. per IOO lb. of load per degree of angle. This thrust is therefore one-sixth to one-eighth of the side thrust due to slip angle. I t appeared therefore that we had improved the handling of the cars by slightly reducing the ability of the front tyres to push the car round a corner. However, a very simple consideration shows that it does. Suppose a car to be proceeding along a straight road, and for any At first sight this did not seem to make sense. * See S.A.E. Journal, February, 1935, page 41 at UNIV CALIFORNIA SAN DIEGO on September 1, 2015pau.sagepub.comDownloaded from MOTOR C.4R S U S P E N S I O N AND I N D E P E N D E N T SPRINGING. 757 reason, such as a change in the road camber, suppose it to roil slightly to one side or the other. The effect of the \u201c camber thrust \u201d produced by parallel-independent front wheels is obviously to make the car run in a very flat curve towards the roll. The centrifugal force due to the curved path of the car is such as to oppose the initial force which caused the roll. The action is exactly similar to that of a bicycle. A little consideration will show that a similar effect also exists when turning corners, and that though the effect may be very small it is exceedingly far-reaching in its results on the general handling of the car. We actually know that it is of the greatest importance through tests made on a flat concrete \u201c plate.\u201d 250 ft. dia., on which the angle of the front wheels, the slip angle of the front and rear wheels, and the roil angle of the car may be measured with considerable accuracy, while the car is driven in a circular path of known radius a t speeds up to the limit of adhesion of the tyres. The angle of the front wheels or \u201c steering angle \u201d is particularly important. In some cars this has to be decreased, 2.e.. the steering wheel has to be turned back as the speed on the turn is increased. These cars are, without exception, unstable in handling, particularly in a side wind. Other cars have a strong reverse characteristic, and have to be pulled into the turn harder as the speed is increased. These cars are, without exception, stable in handling, but, if the effect is overdone (as may readily be arranged experimentally by ballasting the front end or reducing the front tyre pressure) the handling of the car becomes heavy. We have called the first, or unstable, effect \u201c oversteering,\u201d and the second, or stable effect, \u2018\u2018 understeering.\u201d Our work on independent front suspension has been to provide a desirable balance between these two effects. We are sure that a correct happy medfym between the two extremes is go per cent of what we mean by a good sense of direction \u201d in a motor car. These statements are not made as a selling effort. They may be justly criticised as being a case of wisdom after the event. We did not know all these things when we started building independent front suspension, but at UNIV CALIFORNIA SAN DIEGO on September 1, 2015pau.sagepub.comDownloaded from 758 THE INSTITUTION OF AUTOhlOBILE ENGINEERS. (RIr. Maurice Olley.) have found it possible by fitting cars with independent suspension to enjoy some of these benefits. Some authorities have claimed that the chief cause of this is lateral scrubbing of the tyres on the road, and have advocated a truly parallel-action independent, or a wishbone suspension with unequal links arranged so that the tyre contact moves vertically in order to eliminate scrub. Others have pointed out that on a conventional front axle the distance between the two tyre contacts is invariable, whereas on an independent suspension design even of true parallel tvpe this distance varies considerably. They have claimed that a fixed- front axle therefore does not scrub the tyres sideways. Still others, principally the tyre companies, have pointed out that a car which rolls excessively will always show rapid tyre wear, and it is now fairly well ascertained that this is due to the excessive slip angles induced when cornering on a car of little roll stability. If, for example, a car is driven in a circle on a gravel surface and the outer front A few notes may be appropriate on the subject of tyre wear. It can readily be shown that an axle does produce tyre scrub. wheel is driven a t each turn over a ramp, as shown in Fig. 66, it will be found that the inner wheel throws gravel sideways and rapidly digs a hole for itself in the road surface. A little study of \" washboard \" surfaces on gravel roads shows that the waves are often \" skewed \" relative to the road, and therefore suggests that the action described above may be a potent cause of the formation of a washboard surface. On a parallel-action independent this action is not eliminated entirely, but it is reduced, and we think that the variation in length of tyre track is unimportant by comparison. However, the supposed importance of absolutely vertical wheel action on an independent suspension design is contradicted by the quite reasonable performance as regards tyre wear of some German cars with swing axles. We know now that the final result on tyre wear depends appreciably on the slip angles of the tyres and this, again, depends on the roll stability of the car, which is a function of the rolling moment and the resisting moment of the suspension springs. at UNIV CALIFORNIA SAN DIEGO on September 1, 2015pau.sagepub.comDownloaded from MOTOR CAR SUSPENSION A N D I N D E P E N D E N T SPRINGING. 759 I suggest that Fig. 67 shows the moments on a car when turning a corner. F is the centrifugal force applied a t the centre of gravity ; C-D is the roll axis ; L is the wheel base divided into two parts A and \u20ac3 on either side of the centre of gravity ; W is the weight of the spring mass of the car applied a t the centre of gravity ; H, is the height of the latter above roll axis ; and H, is the height of the roll axis above the ground a t the rear. The rolling couple on the suspension springs, when the car has rolled through an angle 8 from the vertical, is, then, F H, + W 0 H,, and this couple is resisted by the suspension at either end in proportion to the rotary stiffness of the suspension a t front and rear. T The couple carried by the tyres is obviously (F + W 0) H, x 1 Ti + T, at the front end, where T, and T, are the rotary stiffnesses of the front and rear suspension respectively. And :- A ( F + w ~ ) H , ~ - T z ~ - + F X ~ X H , Tl + T, at the rear end. This proportion of the total roll couple carried by the front and rear tyres is found to have a very marked effect on steering, and has to be proportioned by trial to avoid excessive effects in the direction either of \u201d oversteer \u201d or \u201c understeer \u201d as described above. The height of the roll axis on an axle is generally somewhat below the level of the main-plate of the leaf springs, and on a parallel action independent with rigid control of the wheel planes it is a t the ground level (neglecting the effect of tyre deflection which is present on all cars). The effect therefore of independent front wheels is to increase the moment arm HI by perhaps 5 in., or half the drop of the front roll centre. But, since the rotary stiffness of the front suspension depends on the square of the lateral separation of the springs, and the spring effect on an independent, as pointed out by the author, is always applied at the tyrc contact, the final result in stahility for a given rate of spring suspension is very definitely in favour of the independent suspension design. This double fact that the spring effect on the latter design is applied a t the tyre contact and that the roll axis depends on the tyre scrub action and not a t all on the spring location, has not been sufficiently understood previous to the author\u2019s paper, and I am personally grateful to him for emphasizing it. I do not quite agree with his figure for the stiffness of a leaf spring suspension in roll, and would increase the figure about 50 per cent for leaf springs with rigid shackles, as we fii:d from tests about this additional stiffening effect due to the twisting of the leaf springs. The method of conducting these tests for the \u201c ride rate \u201d and \u201c roll rate \u201d of car suspensions was described and illustrated in my paper published in the S.A.E. Journal.* An interesting thing which I believe has not been previously pointed out, but which is evident from the above expressions for the roll couple, is that for each form of suspension there is a limiting softness a t which the resisting couple of the springs only just balances the term W 8 H, due to the lateral movement of the centre of gravity. A suspension as soft as this may be said to have no roll stability a t all. Independent suspension, which applies the spring effect on the widest possible base, reaches this limit of zero stability at a very much lower spring rate than conventional suspension with springs separated by about half the track. * See S.A.E. Journal, March, 1934, page 73. at UNIV CALIFORNIA SAN DIEGO on September 1, 2015pau.sagepub.comDownloaded from 760 THE INSTITUTION OF AUTOMOBILE ENGINEERS. Mr. Alex. Taub (U.S.A.) : The author remarked on the fitting of independent suspension on the lower-priced cars. On the Chevrolet, which is the lowest-priced car in the States, we have independent suspension, because it is needed more on the smaller than on the larger cars. Incidentally, though there is some additional expense, it has been found well worth while. I should like to express my opinion (which is shared by most of the engineers in America) of respect for Dr. Lanchester, for the wonderful work that he has done in the past and which we are daily using. Mr. W. S. Renwick: The author has spoken of compromise and its necessity. I think of compromises other than those he envisages, perhaps because I work for the M.G. Car Company. Turning to the author\u2019s remark on page 708 about the use of stabilisers not leading to further safety, but merely encouraging the driver to take corners faster, we find nothing cynical in that ; on the contrary, we think it is our job to make a car which will corner, in comfort, as fast as ever the coefficient of friction between tyres and road will allow. If somehow we, or tyre makers, or road builders can increase that coefficient, it will become our job to make cars which will corner still faster and still in comfort. That is why we think that the compromise of the future will pay greater attention to lateral stability than the author appears to consider necessary. We have done some experimental work, not on the American scale, but we have tried, particularly on the racing cars, to see what could be done with a suspension of the tyre which he classifies as \u2018\u2018 2 A,\u201d I think it well known that our \u201c Racing Midgets \u201d of last year were of that type. Independent suspension of the pure \u201c parallel motion linkage \u201d type, both front and back. They thus had a very low (on ground level in fact, as the author points out) rolling axis, and because of the great reduction of unsprung weight, and consequently increased road adhesion, they were capable of being dragged round corners very fast. It is our experience that, from the road adhesion point of view (in which we are most interested), we must have independent suspension on all four wheels or not at all. Independent suspension of the front only means that the driver is tempted into cornering a t such speeds that the rear axle slides away. Independent rear as well as front gives equal adhesion of all wheels, but then we are well and truly up against the rolling problem. That is why, when the author, in referring to what he calls \u2018 I bastard \u201d systems of suspension, says, on page 695, that \u201d they need not be considered,\u201d we disagree, because we are considering them very seriously indeed. That German rear axle, which the author sketched on the blackboard, has its rear lateral location point some inches above the centre of the rear axle, and the car as a whole has a considerably inclined \u201c roll axis.\u201d In spite of the fact that it looks so horrible on paper, it is, I think, what we are going to come to in the end. The ideal, perhaps, would be some standard parallel motion type of independent suspension in front, and at the rear a suspension which would change its mind, It would be of parallel-motion type when going along a straight road, but would become something like the German when corners were encountered, and roll resistance became more important than tyre scrub. Mr. G. Deacon : I feel that reference in the paper to the different modes of application of independent wheels would have been valuable :-(a) with regard to steering mechanism ; (b) with regard to maintenance, as I am We are looking at the height of the lateral location. at UNIV CALIFORNIA SAN DIEGO on September 1, 2015pau.sagepub.comDownloaded from MOTOR CAR SUSPENSION AND INDEPENDENT SPRINGING. 761 led to believe that systems of independent suspension lead to chatter when they have been in use for some time, which necessitates the frequent checking of toe-in, etc. To my mind the design of Broulhiet independent suspension shown in Fig. 45 warrants special attention. In this design the steering does not have to accommodate itself a t all to the irregularities of the road surface. Each front wheel is mounted on a pivoted guide post on which the stub axle slides freely up and down, the friction and wear being eliminated by a special kind of sleeve ball bearing working in splines. There is absolutely no shake in these splines, as the leverage is low, and even the very slightest amount of play is taken up immediately by the slightly offset weight of the car. A very simple and effective shock absorber is included which requires no brackets. It consists of a plunger with a graduated slot working in a dashpot inside the guide post, which is hollowed. This design seems most effective. Will the author give his opinion of this system in relation to others ? Dr. Lanchester, in replying to the discussion, said : I t has been a real pleasure to me to have had with u s Mr. Olley who is probably the greatest exponent of independent springing, and to have heard a t first hand an account of his experiences. I am grateful for his contribution, and have learned a great deal, and so, I am sure, have all those present. On some points in which I do not appear to be in agreement with Mr. Olley, I think the differences may be accounted for as a matter of terminology. On the question of the Kz/A B ratio, I have taken A as equal to B in order to simplify the discussion, and consequently Mr. Olley\u2019s A B becomes my Lz. The model used by Mr. Olley for the purpose of demonstration is what I refer to as a \u201c bar-bell.\u2019\u2019 If you watch the middle of that bar when the pitching is a t its maximum, you will see that the centre of the bar is practically stationary ; when on the other hand, the middle of the bar is rising and falling, we have represented the condition of bounce. That is one of the points I tried to make clear in the paper. The difference between Mr. Olley\u2019s version of bounce and mine is that he describes two centres, rather like the pendulum used by scientific men for determining the value of gravity. On my part I do not agree that there is such a thing as a bounce centre. My argument is based on the scientific fact that there are two degrees of freedom. One degree of freedom relates to oscillation about a transverse axis, and the other comprehends motion of the centre of gravity in a vertical path, and these two degrees of freedom define the behaviour of the bar-bell. Much of what Mr. Olley has shown is implicit in my own theoretical dissertation. I was very interested in Mr. Olley\u2019s comments regarding the reception of scientific men in the General hlotors organisation, because it is the same here ; human nature (and inhuman nature) are the same the world over. Then, as to the method of determining the moment of inertia in a car, experimentally. The method described by Mr. Olley is the same as employed by me in the case of model gliders, even the smallest. The moment of inertia of those models is important as concerning the critical condition of stability. In some cases the models were swung from two points as a check on the result. An account of this will be found in \u201c Aerial Flight. \u201d * I cannot but wonder whether Mr. Olley approves of the American technical-sales literature as issued by General Motors. In response to an Constable, * \u201c Aerial Flight,\u201d Lanchester, Vol. 11 ; 5 172 and App. VI. London. at UNIV CALIFORNIA SAN DIEGO on September 1, 2015pau.sagepub.comDownloaded from 762 THE INSTITUTION OF AUTOMOBILE ENGINEERS. (Dr. Lanchester.) enquiry I received from Messrs. Cadillac a most extraordinary booklet. In i t is illustrated what they call \" Knee-action,\" see Fig. 68. To the left of a figure of a man demonstrating \" knee-action \" is shown a car in which the suspension must be solid ; it might consist of wooden-blocks in lieu of springs. On the other side, to the right, a car is shown having suspension in which clearly the springs can have no stiffness whatever. One can only reflect on what a poor opinion General Motors must have of the intelligence of the people to whom this booklet is issued. He kindly calls my attention to the fact that I have made no mention of the torsional stiffness of laminated springs as contributing to lateral stiffness. This is quite true, and in some degree it constitutes an additional argument in favour of suspension of the normal type. I am much interested to learn that independent suspension is being fitted to the Chevrolet in the U.S.A. I t is always a knotty point how far it is good commercial policy to introduce refinements There is one more point mentioned by hlr. Olley. In reply to Mr. Taub. which tend to increase cost on the lowest-priced cars. If by obtaining increased popularity it leads to a larger output and that, in turn, lowers the cost sufficiently to provide compensation, it may be justified. But when the same course is followed by competitors-what then ? And if tyre wear is increased and the public find this as a fact, again-what then ? Generally, if the big luxury car leads with any new refinement sooner or later the lower and lowest-priced cars follow, the new feature acquires from its aristocratic origin what has been aptly termed \" snob-value.'' I sincerely thank hlr. Taub for the kind words with which he concludes his remarks. Replying to the objections raised by Mr. Kenwick. If I were devoting special attention to racing machines, 1 might be disposed to take a rather different point of view to that disclosed in the paper. In racing, safety is not a matter of first consideration, a \" safety first \" competitor in a race would get nowhere. In the design and construction of a racing car everything is done to secure speed and road-holding qualities to which everything else in the design is subordinate. Some day, perhaps, I will write a paper on racing cars ; there is no one better qualified to do so than I am, because I have never been in a racing car in my life ! at UNIV CALIFORNIA SAN DIEGO on September 1, 2015pau.sagepub.comDownloaded from Plate XL MOTOR CAR SUSPENSION AND INDEPENDENT SPRINGING For text reference, see Appendix VI. page 725. at UNIV CALIFORNIA SAN DIEGO on September 1, 2015pau.sagepub.comDownloaded from Plate XLI MOTOR CAR SUSPENSION AND INDEPENDENT SPRINGING. at UNIV CALIFORNIA SAN DIEGO on September 1, 2015pau.sagepub.comDownloaded from Plate XLll MOTOR CAR SUSPENSION AND INDEPENDENT SPRINGING. For text reference. see page 725. For t e x t reference, see page 725. at UNIV CALIFORNIA SAN DIEGO on September 1, 2015pau.sagepub.comDownloaded from"
        ]
    },
    {
        "image_filename": "designv11_10_0000030_piae_proc_1935_030_039_02-Figure67-1.png",
        "original_path": "designv11-10/openalex_figure/designv11_10_0000030_piae_proc_1935_030_039_02-Figure67-1.png",
        "caption": "Fig. 67.",
        "texts": [
            " However, the supposed importance of absolutely vertical wheel action on an independent suspension design is contradicted by the quite reasonable performance as regards tyre wear of some German cars with swing axles. We know now that the final result on tyre wear depends appreciably on the slip angles of the tyres and this, again, depends on the roll stability of the car, which is a function of the rolling moment and the resisting moment of the suspension springs. at UNIV CALIFORNIA SAN DIEGO on September 1, 2015pau.sagepub.comDownloaded from MOTOR CAR SUSPENSION A N D I N D E P E N D E N T SPRINGING. 759 I suggest that Fig. 67 shows the moments on a car when turning a corner. F is the centrifugal force applied a t the centre of gravity ; C-D is the roll axis ; L is the wheel base divided into two parts A and \u20ac3 on either side of the centre of gravity ; W is the weight of the spring mass of the car applied a t the centre of gravity ; H, is the height of the latter above roll axis ; and H, is the height of the roll axis above the ground a t the rear. The rolling couple on the suspension springs, when the car has rolled through an angle 8 from the vertical, is, then, F H, + W 0 H,, and this couple is resisted by the suspension at either end in proportion to the rotary stiffness of the suspension a t front and rear"
        ],
        "surrounding_texts": []
    },
    {
        "image_filename": "designv11_10_0000005_1.1707241-Figure8-1.png",
        "original_path": "designv11-10/openalex_figure/designv11_10_0000005_1.1707241-Figure8-1.png",
        "caption": "FIG. 8. (a) The motion of the journal center with increas ing source strength (direction of the arrow) when the lubricant source is at the base of the bearing and S=0.05. (b) The motion of the journal center with fixed source strength but varying Sommerfeld variable when the lubricant source is at the base of the bearing. For segment directed to the right qo = 0.025; for segment directed to the left qo=0.20. Arrows indicate decreasing values of S. Bearing length = bearin~ perimeter.",
        "texts": [
            " (29\u00bb for all values of S. And when qo exceeds this critical value the journal wiII rise above its central position, and a will fall to values less than 11'\"/2, as shown in Fig. 7. To calculate the values of the Sommerfeld variable for the present case one may use exactly the same formula as when the source is at the crown of the bearing, namely, Eq. (23). The previously discussed effe'tt of the strength of the lubricant source on the position of the center of the journal is shown graphically in Fig. 8(a) for W= 1 and S=0.05. The arrow indi- 55 [This article is copyrighted as indicated in the article. Reuse of AIP content is subject to the terms at: http://scitation.aip.org/termsconditions. Downloaded to ] IP: 129.174.21.5 On: Sun, 21 Dec 2014 16:10:19 cates the motion of the center of the journal with increasing values of go, the extremity to the right of the curve referring to the zero value of go. For a system of fixed source strength but variable S, the motion of the center of the journal is shown in Fig. 8(b). The arrows here indicate the direction of motion as S is decreased, the segments of both curves beginning at the centers of the circles, i.e., at '1/ = 0 corresponding to S'\" 0() , and ending on the vertical axis for s=o. The segment directed downward refers to the value of go = 0.025, which is less than the critical value. The segment directed upward was calculated for go=0.20, which exceeds the critical value. The radically different behavior of the center of the journal under the conditions where the source strength is less or greater than the critical values will be obvious from this diagram",
            " The line coincident with the S axis refers to the critical value of go, at which 7j = 0, for all values of S. While the gen~ral trend of the curves at the larger values of S is the same as found previously for the case where the source is at the crown of the bearing, their relative positions for different 56 values of go depend upon whether or not go ex ceeds the critical value. Thus for fixed S, in creasing values of go lead to smaller eccentricities until the critical values of go are reached, after which the situation reverses. This behavior clearly corresponds to that indicated in Fig. 8(a). Moreover, as actually shown for the cases where go=0.05, 0.10, and 0.15, the curves will show maxima at the small values of S, and ultimately drop off again as S approaches zero. This be havior will be followed by all the curves excepting that for go = 0, the absence of the maxima for go=O.Ol and go=0.25 in Fig. 9 simply indicating that these maxima and the 1/ axis intercepts will be found for values of 1/ exceeding 0.5 when go is very small or very large. The existence of the 1/ axis intercepts less than one means that, as previously suggested, the lubricant source alone will be able to support the load even when there is no journal rotation (S = 0) when the source is set at the base of the bearing"
        ],
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    },
    {
        "image_filename": "designv11_10_0000030_piae_proc_1935_030_039_02-Figure48-1.png",
        "original_path": "designv11-10/openalex_figure/designv11_10_0000030_piae_proc_1935_030_039_02-Figure48-1.png",
        "caption": "Fig. 48.",
        "texts": [],
        "surrounding_texts": [
            "For text reference, see Appendlx VI, pa;e 725. at UNIV CALIFORNIA SAN DIEGO on September 1, 2015pau.sagepub.comDownloaded from MOTOR CAR SUSPENSION A N D IXDEPENDENT SPRINGING. 721 Or if offset from c.g. be taken into account, : = \"57 x 1/I6,200= 225, 0 0 . 4 2 We shall be justijied in accepting t = 0.4 , or pitch-oscillation per min. - 150. In connexion with the design of the car under discussion the author had a t command the experience gained in the design and construction of three experimental cars which preceded it. He came to the conclusion that the wheel-base which he had previously adopted, and that which was then common in other cars, was altogether too short for good riding, and although from a present standpoint the wheel-base, namely, 7 ft. 10 in., looks very little, i t represented an extension of a foot or more compared to other cars a t that time on the market. Further, the author was led to concentrate the mass in the centre of the car-that is to say, according to present knowledge, to do that which would induce a high pitching frequency. In this the author was guided by a somewhat different idea from that which now prevails. I t was clear to him that if the moment of inertia about a transverse axis could he reduced sufficiently, in the extreme case disposed of entirely, then pitching would not take place other than that directly impressed by road irregularities, and, were this so, the longer the wheel-base the less the angle through which the car would he forced to pitch. The lengthening of the wheel-base and the concentration of mass were measures following logically on these considerations. In the light of the knowledge gained subsequently, it is evident that the reverse argument might have been used, namely, that the greater the moment of inertia the slower would be the pitching period-that is to say, the lower the frequency and the greater the comfort. Actually, on the road the riding of the xo/rz h.p. car was everything that could be desired. Undoubtedly, the car did pitch t o a small extent, but although pitch frequency was comparatively high (as shown by the calculation) there was no discomfort. The author's present view is that the two extremes are good, namely, a very low moment of inertia, or a comparatively high moment of inertia, but that the conditions are worst a t some intermediate value. A car of which the suspended mass has a high moment of inertia can acquire a large amount of energy in pitching which has to be damped out, whereas one with little moment of inertia cannot acquire much energy it approximates the condition of zero moment of inertia when no energy a t all can be stored in the pitching oscillation. In this matter of moment of inertia the author suspects that many of the small cars which may be seen \" bucketing \" along the road to-day, with the back-rest (actually much too hard) punching the occupants on the shoulder blades (and giving them arthritis in the cervical vertebrz), are, from the standpoint under discussion, about as bad as is possible. When we consider the effect of a single road obstacle, such as a brick or other obstruction lying in the fairway, or an over-filled trench, or a subsidence, due to the laying of a sewage connexion or gas or water pipes, the relations between speed, length of wheel base, and pitching period assume a special importance. The behaviour or a car so far as concerns comfort, or as the Americans term it, \" ride,\" depends upon the time which elapses between the front wheels and the rear wheels encountering the obstacle ; the second impact may tend to reinforce the oscillation set up by the first or may tend t o damp i t out. Since this time period depends LANCHESTER. 46 at UNIV CALIFORNIA SAN DIEGO on September 1, 2015pau.sagepub.comDownloaded from THE INSTITUTION OF AUTOMOBILE ENGINEERS. 722 upon the speed of the vehicle, it comes about that any given car is better (more comfortable) a t certain definite speeds than at others : there are good and bad ranges of speed. Given a good road as basis the incidence of an occasional lump or pot-hole is by no means unusual, and herein lies the chief importance of the study of this condition ; but evidently the importance of the study is not confined to this particular condition ; the same will apply to any bad road in which lumps and pot-holes abound, for each of these will give its \u2018\u2018 double kick,\u201d and so such a road surface may be considered as constituted by a number of single lumps and potholes whose influences are superposed. Let us consider the oscillations in terms of a simple pendulum and deal with a few typical cases ; it is always legitimate to consider harmonic disturbances on this basis. Firstly, we will take the case of a car meeting with a sudden change of level of the road surface, as when a road has been re-surfaced section by section and the junctions are imperfect, Fig. 33, Now, the front wheels, on meeting the discontinuity, change their level suddenly ; thisin thependulum, Fig. 34. is equivalent to the fulcrum having its position changed in a horizontal direction, we will say from L to R (left t o right). This is a change of equilibrium position made with such rapidity that, during the change, the pendulum, or in the case of the car, the suspended body, has no time t o respond. Then the swing begins. If, after a half swing, the original position of the fulcrum be restored R to L, then oscillation is piled on oscillation, the swing will be from Y to Z, and the riding will be bad. In the case of the old Lanchester with its 8 f t . wheel base and 0.4 sec. pitching period, this means that under the at UNIV CALIFORNIA SAN DIEGO on September 1, 2015pau.sagepub.comDownloaded from MOTOR CAR SUSPENSION A N D INDEPENDENT SPRINGING. 723 conditions given a speed of 8 f t . in 0 . 2 sec., i . e . , 40 f t . per sec., will be one of minimum comfort. If, now, the position of the fulcrum be restored (R to L) after a full swing, the pendulum will be brought to rest. So i t is with the car, a speed of 8 ft. in 0 . 4 sec., is., 20 f t . per sec., will be one of optimum comfort. And following the matter up we see that 8 ft. in 0.6 sec. (13 .3 ft. per sec.) will be bad, and 8 ft. in 0 . 8 sec. (10 f t . per sec.) will be good. The road condition taken in the above example is unusual, but not unknown. We will now consider the condition when the car encounters an obstacle such as a brick on the road. This will be regarded as a sudden displacement of the fulcrum of the equivalent pendulum and its almost immediate return. The pendulum bob, after this disturbance, will be virtually in midposition (mid-swing) and possessed of a velocity due to an impulse. When the same obstacle is met by the rear wheels the impulse must be considered, in the pendulum analogue, as of opposite sign : that ip to say, if the first impulse is from L to R this second impulse will be from R to L. If this second impulse be given one complete swing period, or multiple thereof, later than the first it will act to annihilate the disturbance first set up, but if the second impulse be applied a t any half period the swing will be amplified. Here again we see that the condition of optimum comfort will be found at speeds of 8 ft. in 0 . 4 sec. = 20 ft. per sec., 8 f t . in 0 . 8 sec. = 10 ft. per sec., etc., and the condition of least comfort a t speeds of 8 ft. in 0 . 2 sec. = 40 f t . per sec., 8 f t . in 0.6 sec. = 1 3 . 3 ft. per sec., etc. The fact that under both the conditions visualised the most favourable and least favourable velocities are found to be the same will justify us in considering that these results are of general application. There is one warning that must, however, be given, the second condition postulated, namely, that due to a very temporary obstruction-typified by the brick-end, is directly influenced by speed, apart from the special conditions envisaged. The magnitude of the impulse (energy imparted) is dependent upon, and directly as, the square of the time of application of the disturbing force. which is inversely as the square of the velocity. It is generally admitted that high speed \" irons out \" road roughness, and this is the reason. Hence the relations between wheel base and pitching period dealt with ahove do not fully define the conditions. Speeds of least discomfort will generally be higher than those given owing to the virtue inherent in speed itself. at UNIV CALIFORNIA SAN DIEGO on September 1, 2015pau.sagepub.comDownloaded from 721 T H E IN ST IT U T IO N O F A U T O 3IO B IL E E N G IN E E R S . / I' / i i i I I at U N IV C A LIF O R N IA S A N D IE G O on S eptem ber 1, 2015 pau.sagepub.com D ow nloaded from MOTOR CAR SUSPENSION A N D INDEPENDENT SPRINGING. 725 APPENDIX VI. The response to the author\u2019s broadcast invitation to manufacturers to supply technical particulars of their systems of independent springing has been meagre ; in many cases all that has come to hand has been a bundle of sales catalogues and literature. On the other hand, the response in some cases has been most gratifying, and the author desires to express his thanks to those who have, a t much trouble to themselves, granted him facilities for personal trials and investigations. Out of the particulars received some nine cases have been selected for the purpose of illustration, and some few others to which appropriate references are made. These will be taken in alphabetical order. I . A L V I S . Type I1 C. See Figs. 42 and 52. Plate XLI. Thisis the type adopted on three or four of the firm\u2019s latest models employing rear drive. The type adopted on the Alvis front-driven cars is also of Type I1 C, illustrated in Fig. 43 (u) and ( b ) . (This model has front-wheel drive.) 2. B I R M I N G H A M S M A L L A R M S . 3. B R O U L H I E T . Type I c. See Fig. 45. 4. C A D I L L A C . See Figs. 53 and 54, Plate SLII . 5. DELAGE. Type I1 D. See Fig. 51, Plate S L I . 6. E L V I D G E . Type I1 A. See Fig. 55. 7. F R A S E R N A S H . Type I1 C. See Fig. 46. 8. GORDON A R M S T R O N G . Type I11 B. See Fig. 47. 9. AfERCEDES-BENZ. Type I1 A. See Fig. 45. 10. ROLLS ROYCE. Type I1 A. See Fig. 49. 11. V A UXHALL. Type 111 C. See Fig. 50. Plate XL. The Vauxhall does not belong exactly to any of the types scheduled in 33. The box (3) in the figure contains a spiral spring, arranged to function much as in the Gordon Armstrong. The cranked links are pivoted in this box and not in cross members of the chassis, as in the Gordon Armstrong (this feature looks weak). As far as may be judged, the whole box is pivotally mounted, instead of the wheel only. Beyond the above the Humber and the Singer both employ the Gordon Armstrong or something very like it. Citrogn makes use of Type I1 A, as does also Elvidge. In both these the suspension spring is provided in the form of a straight bar in torsion. Type I1 B. . See Fig. 44. See Figs. 55 and 56. at UNIV CALIFORNIA SAN DIEGO on September 1, 2015pau.sagepub.comDownloaded from 726 T H E IN ST IT U T IO N O F A U T O M O B IL E E N G IN E E R S. at U N IV C A LIF O R N IA S A N D IE G O on S eptem ber 1, 2015 pau.sagepub.com D ow nloaded from MOTOR CAR SUSPENSION AND INDEPENDENT SPRINGING. 727 THE DISCUSSION. (DERBY CENTRE.) Mr. A. G. Elliott, in opening the discussion, said : I can confirm the bad effect of undamped upholstery in the car, but I differ from the author in saying thatwe ascribe the trouble purely to the periodic effect of the mass of the passenger on these undamped springs activated by the other movements of the car. The comfort of the ride can be completely spoiled by undamped cushions on a vehicle that is otherwise satisfactory. The Rolls-Royce system of independent front suspension is a compromise. The roll centre is about 7 in. above the ground level, and there is a certain amount of gyroscopic reaction fiom the front wheels to be taken care of. It is a sacrifice we have to make to get the roll centre higher and keep the track unaltered. Mr. D. Bastow : The author has said that he would like a description of the Rolls-Royce system of independent front wheel suspension, which I shall be glad to give before proceeding with the discussion proper. The general lay-out of the system is upper and lower wishbones or triangles, the upper one is shorter than the lower and the pivot axes of these triangles are not parallel to the centre-line of the chassis, but are inclined inwards towards the rear as in the Cadillac, which the author mentioned. The wheel itself-the pivot assembly-has a pivot-pin passed through these two bosses and the weight goes on through the upper triangle levers, which are secured to this fulcrum pin. To the centre part of this fulcrum-pin is secured a lever a, Fig. 49, page 722, which looks down into the main housing. This lever a has two rollers b, at its lower end, which bear against a piston flange c, which pushes the two coil springs e inside the housing and these springs give the elasticity of the system. In the centre of the coil springs is the shock-damper arrangement. The same piston flange c, which is worked by the rollers b, is attached to a piston d, which works inside two fixed cylinders which are full of oil. One of these can be seeq a t fi. Displacement of the piston towards the outer end, caused by upward or bump displacement of the wheel, causes oil to flow from this chamber, through the central tube A, past the valve and so back into the chamber a t the other end. Downwards or rebound movement causes flow of oil in the reverse direction. The valve of the shock-damper is a twin valve consisting of a mushroom type valve k, whose head is exposed to pressure in the tube A, see Fig. 57, and a sleeve I surrounding the stem of the mushroom valve, but not reaching up to its head. The valve is held on its seat by a spring n, against which a collar on the valve stem bears, and the sleeve bears against the reverse side of this collar, so that since the area of the sleeve is larger than the area of the head of the mushroom valve, the admission of oil under pressure into the space between the head and the end of the sleeve vzd passages m will lift the valve off its seat, just as will pressure in the tube A. The valve spring n is enclosed in a bellows 0 , one end of which is fixed to a plate held under the housing j . The plate closing the other end of the bellows bears against the end of the spring remote from the valve, and oil pressure round the outside of the bellows compresses them and increases the spring load on the valve and so increases the damping. The oil pressure round the outside of the bellows is provided by a \u2018\u2018 governor control \u201d unit driven from the gear-box, which is so arranged that the pressure at UNIV CALIFORNIA SAN DIEGO on September 1, 2015pau.sagepub.comDownloaded from 728 THE INSTITUTION OF AUTOMOBILE ENGINEERS. (Mr. D. Bastow.) increases with the road speed of the car, and can also be varied by an overriding hand control. -4 tension rod approximately on the king-pin centre-line works a lever on the brake actuating camshaft by its upper end, the lower end being pulled by a bell-crank lever oT which the other arm is pulled by another rod. The inner end of this rod is attached to an idler lever on the frame, and the length and initial position of thc rod are arranged to give the minimum of alteration of braking with up-anddown movement of the wheel. Further rods from the idler levers on the frame connect to a central equaliser worked by a cable coming uzh another idler lever from the servo on the gear-box. In the centre of the car on a pivot there is a steering lever which looks backwards, with two ball Brake operation is by rods and levers. The steering layout is by divided track-rod. Fig. S7. pins, and from each of these a steering tube comes out to a lever on the pivot assembly and controls that particular wheel, and from the side of the central lever is another arm, with a tube ball-jointed to it going back to the pendulum lever on the steering box. The main housing g (Fig. 49) is spigoted into a circular distance-piece in the frame, which is, I consider, a very good feature. It is secured to it by a number of studs going right through, and in addition there is a pressing which is bolted to the back of the housing and bolted to the frame, the whole assembly being very rigid. The potf, which contains the springs, is secured to the outside of the frame. I do not agree with the author that the roll centre or lateral location of an independent suspension is on the ground. The roll centre of our own suspension is certainly above the ground, and it is quite possible to get at UNIV CALIFORNIA SAN DIEGO on September 1, 2015pau.sagepub.comDownloaded from MOTOR C.4R S U S P E N S I O N A S D I S D E P E N D E N T S P R I N G I S G . 729 almost any height of roll centre by arranging the linkage. \\Vith one type of front suspension which has not been nientioned the swinging half-axles, type, where the axle is divided in thc middle, each half being pivoted to tllc frame and carrying a wheel, and Xvhere naturally gyroscopic reactions have then been introduced on the steering, the roll centre is above the pivot point of the swinging half-axle. This is obvious if it is realised that the roll centre is on the line joining the point of contact of the tyre and road to the instantaneous centre of movement of that point of contact of tyrc and road in relation to the car. With swinging half-axles the instantaneous centre is obviously the pivot centre of the half-axles, and the lines from the tyre anti road contact point t o these are produced t o meet on the centre-line of the car at a point which is above the level of the half-axle pivot. This is the roll centre of the car for the normal position of the wheels. If the mass is concentrated below the half-axle pivots, then the outward force when cornering will cause the car to tilt inwards, so obviously the roll centre is well above the ground. This has the advantage of reducing the roll on corners, and as it is done on the Rolls-Royce system, has the other advantage of keeping the outside wheel approximately vertical when cornering. That helps the cornering power of the tyre. A paper in the S.A.E. Jortrnal in the first part of 1935 deals with the question of tyres. It shows that if the tyre is kept vertical instead of leaning outwards about 5 deg. the cornering power of the tyre is doubled, or its slip angle halved. (These are approximate figures.) AS far as actual experience of our suspension goes, we can say that tyre wear is reduced and not increased. The point of inclining the pivot axes Of the triangles inwards towards the rear is that with the wheel inclination altering as the wheel goes up and down, keeping the outer wheel at an approximately constant inclination to the ground, the caster angle is at the same time altered and reduced on rounding corners, and with a large car one of the problems is the exceedingly strong self-centering effect of the tyres. and acything that can be done towards reducing that selfcentering makes it much easier t o hold the steering on corners. There are one or two smaller points I should like to bring up. I think i t is very unlikely that the roll angle of 10 deg., which the author quotes, is ever reached, because even on a big car with big spring deflections I think 6 deg. is the maximum. Certainly a roll angle of even less can be felt very much in a car. I think a passenger would begin to feel that the car is turning over with even 6 deg., and 10 deg. would be very had. One point about the lateral location being at or near the ground : the author stresses that from the point of view of sideways load imposed on the tyre and the sideways throwing of the car. When cornering, the effect given of rolling appears t o be composed of two things, namely, first the actual angle through which the car rolls, and secondly the sideways displacement of the passenger in the car, and when the roll centre is on the ground that sideways displacemcnt is increased, and I think that to get the same effect as with a normal front axle the roll angle of the car must be reduced, even when the roll centre is above the ground. Another point : the use of an anti-roll stabilizer, apart from allowing softer springs t o be used, is that by keeping the car more Vertical the cornering power of the tyres is again helped. The author, because of assuming the roll centre t o be on the ground, has not been altogether fair t o the independent front suspension in the case of anti-roll stiffness, and I think that actuallv i t is. say, 25 per cent. better than the ordinary front axle. I think a car may be, for the same stiffness of springing, certainly 23 times as stiff, without any very bad effects showing themselves in other ways. I have already- mentioned the roll centre. at UNIV CALIFORNIA SAN DIEGO on September 1, 2015pau.sagepub.comDownloaded from"
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        "image_filename": "designv11_10_0001404_t-aiee.1932.5056199-Figure1-1.png",
        "original_path": "designv11-10/openalex_figure/designv11_10_0001404_t-aiee.1932.5056199-Figure1-1.png",
        "caption": "FIG. 1-SINGLE-PHASE SHORT-CIRCUIT TORQUE OF 100,000-KVA. ALTERNATOR, MAXIMUM INITIAL ARMATURtE LINKAGES",
        "texts": [
            " It is to be noted that this high peak value is eO = armature voltage before short circuit largely due to the presence of trapped armature link- a = angular position of the direct axis at the instant of ages, since with no armature linkages the peak value of short circuit, measured in the direction of rotation torque is only 4 times normal. from the axis of the armature winding The trapped armature linkages are also responsible and XD\" and xQ\" are respectively the direct- and quadrafor all odd harmonic components of torque. Fig. 2 ture-axis single-phase static reactances of the shortshows that with no trapped armature linkages the circuited armature winding. torque is made up entirely of even harmonics and in Changing to three-phase reactances, as in equation Fig. 1 it is seen that the odd harmonics decay gradually (1d) of Appendix D, the current is so that the torque curve approaches that of Fig. 2. ( It appears from the equations in Appendix B that the 3 eO [cos (t + a) - cos a] (2a) short-circuit torque is the same for line-to-line and line- kH to-neutral short circuits. This is exactly true for an where ideal machine and is true for actual machines to the H = (XIt' + Xq7\") + (Xd\" - Xq\") cos 2 (t \u00b1 ae) (3a) extent that Xo/2 is negligible in comparison with xd Asonneeec3euto 2)abrsl and xq\" (see Appendix D)"
        ],
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        "image_filename": "designv11_10_0000030_piae_proc_1935_030_039_02-Figure11-1.png",
        "original_path": "designv11-10/openalex_figure/designv11_10_0000030_piae_proc_1935_030_039_02-Figure11-1.png",
        "caption": "Fig. 11.",
        "texts": [],
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            "at UNIV CALIFORNIA SAN DIEGO on September 1, 2015pau.sagepub.comDownloaded from 692 THE INSTITUTION OF AUTOMOBILE ENGINEERS. direction to that which would give relief (z.e., true rolling contact) and the rnortar-rnill action is accentuated.* I t is evidently not possible to make a comparison between the two types of springing as to tyre wear, because if a car were to do all its running on straight arterial roads we should not expect there to he any difference at all between one system of springing and the other. If, on the other hand, most of the mileage were run off in wkding lanes and in cities, we should expect a very material difference in favour of axle-suspension. The author believes, without being able to give any definite figures, that this difference may sometimes amount to as much as a 30 or 40 per cent reduction in the mileage for a given amount of tyre wear and tear ; in other words (roughly speaking) a 50 per cent increase in the cost of tyre maintenance and replacement. 5 27. It is an unfortunate fact that, however accurately a front wheel suspension and steering mechanism may be designed and put up in the first instance, it is never known to \u201c stay put.\u201d There is a general tendency as back-lash develops for the wheels t o splay in such a manner as to make their natural tracks divergent. To compensate for this in advance, i t is customary to give the alinement of the wheels initially a certain degree of \u2018\u2018 toe-in.\u201d \u201c Toe-in \u201d is sometimes specified for another reason altogether, namely, to compensate for wheel camber or splay in a vertical plane. Some ten years ago the author investigated this subject at the Daimler Works, as related to the ordinary axle-suspension, and established on theoretical grounds an optimum relationship between the wheel splay or camber and \u201c toe-in.\u2019\u2019 Unfortunately, owing to his connexion with the Daimler Company having been severed, he has no longer access to this source of information, nor to the tests which were subsequently made in confirmation. 3 28. The principle on which the relation between \u201c toe-in \u201d and splay (or camber) was founded is as follows :- If a road wheel be so mounted as to have an outward inclination, that is if i t .be inclined to the vertical, Fig. 12, the rolling conditions are abnormal. This splay, or, as some call it, camber, is in common use on horse-drawn vehicles, and has been so since the remote past, long before the advent of the self-propelled vehicle, the object being to permit of a wider body, this being of especial value in the case of farm carts and wagons. It allowed of fuller loads of bulky produce, such as hay, to be carried ; also in the case of merchandise, such as bricks, the c.g. when loaded could be kept lpwer than would otherwise be the case. Under these conditions, the wheels, iron shod, had a considerable \u201c mortar-mill \u201d action. The different parts of the tyre where in contact with the road could not all move with one and the same velocity as rectilinear motion required, and so there was friction set up, and disintegration of the road surface exactly as in mortar-mill. This was probably one of the main causes of the generation of fine dust and mud in the old days, also of tyre wear. * Mortar-mill action commonly gives rise to a scrubbing sound, sometimes even a squeal. 9 26. at UNIV CALIFORNIA SAN DIEGO on September 1, 2015pau.sagepub.comDownloaded from MOTOR CAR SUSPENSION AND INDEPENDENT SPRINGING. 693 Firstly, the object of wheel splay or camber is not the same. Secondly, the problem is fundamentally modified by the resilient (pneumatic) tyre. SO far as the object is concerned, we might better say the excuse, the practice was undoubtedly based to a great extent on a misapprehension. It was due to an endeavour to make the steering pivot axis coincide with the centre of the contact area between tyre and road. The same result was sometimes sought by other methods -5s 17, 18, Figs. IZ t o 15. But a small amount of camber was undoubtedly beneficial. If there be camber without toe-in, there is a considerable force set up, tending to widen the gauge; that is to say, an outward force, and any such lateral force involves unnecessary tyre wear. By making use of toe-in, this may be neutralised or even reversed. The demonstration is as follows :- One would naturally expect that by means of toe-in it would be possible to get rid of outward lateral forces on the tyres since such outward forces could, if not otherwise present, be brought into being by \" toe-out.'' But we must not rely too much on what we should '' naturally expect \" when dealing with engineering problems. Firstly, we must formulate definitely how the outward force comes about. We will assume in the first instance that the tyre tread on meeting the road surface is adhesive, and that no slip takes place during the period of road contact. Then, referring to Fig. 18,* it will be seen that the body of the tyre must undergo a twist. Confining our attention to the right-hand wheel, the direction of this twist will be counter-clockwise until the point is reached where the tread contact is plumb under the axle and then the twist will be relieved up to the point when road contact ceases. So the net result is that for the length of the contact arc (usually about 10 in. or I ft.), the body of the tyre is pulled out of position to the right, which means definitely that the road surface, by which this twist or distortion is brought about, must be exercising a force to the right, tending to pull the wheel off its axle. It is necessary to add that the torsional stiffness of the tyre, which is considerable, will distribute the twist a distance beyond the local area of contact. Also it is to be remarked that the supposed condition that there shall be adhesion between tyre tread and road, and no rubbing, is not strictly true. There will be some yielding and the outward lateral force applied by the road surface must in practice induce some degree of frictional yield, so that the adhesion will break down and the force will be in some degree relieved. The practical condition will be something between the full force and full adhesion (no slip), and a no force and complete slip, and the compromise reached will depend upon the state of the road surface. fj 29. We now consider the conditions which arise when \" toe-in \" is applied as a corrective. In Fig. 19 the extent of toe-in shown is sufficient t o bring the direction of motion (straight ahead) into alinement with the tread where it makes first contact with the road. * Figs. 18, IQ and 20 are exaggerated. Fig. ZI is more nearly a true rendering. In the motor vehicle the conditions are different. This is without toe-in. at UNIV CALIFORNIA SAN DIEGO on September 1, 2015pau.sagepub.comDownloaded from 694 THE INSTITUTION OF AUTOMOBILE ENGINEERS. Then, assuming provisionally the condition of complete adhesion, the body of the tyre undergoes torsion in the opposite direction to that previously the case, namely, in a clock-wise direction, and this denotes a force applied from road to wheel acting from right to left. When the tread leaves the road surface, the cause of this torsion is removed, but the tyre cannot instantly spring back into its central position because of its torsional stiffness. Actually what happens is much the same as under the conditions discussed above, namely, the magnitude of the force is reduced by slipping between tread and road surface. We will now consider the conditions when the toe-in is reduced to half that suggested, Fig. 20. The natural path of a point on the tread of the tyre without restraint is indicated by the dotted line, it is in plan part of an ellipse ; and shown by a solid line is the path during the period of contact on the assumption of perfect adhesion. Here it will be observed that for the first half of the contact period there is a force tending to force the tyre outwards, and during the second part of the contact period the force acting on the tyre from the road in the opposite direction tending to push the wheel home on its axle, L e . , inwards. The two tend to balance, and so it may be inferred that the scrubbing of the tyre on the road will be less for this condition than for either extreme. 5 30. Optimum Toe-k-If in radians 0 be the angleof camber (from the vertical), and b the radial yield of the tyre in inches whose external diameter is 35 in., then the half-length of the contact area between tyre and ground is 1/35. And if the point of first contact and the centre of the contact area are both on the axis of motion, Figs. 20 and 23, the angle.of the toe-in a will be given by- . . . . . . . . . (1) 0 b 6356 By way of example, we may take 8 = 0.1 radian, and b about I in., so that taking d\\/35b = 6 ; then- 0'1 a = - radian, or 1160th. 6 If the toe-in be gauged by means of two staffs or gauges measuring the distance between the front and rear tyres respectively, Fig. 22, the difference between these will be- 2 x (in.) = 1 - 2 in. 60 If the measurement be taken between the tyres and not from centre to centre, the difference will be I in. with sufficient exactitude. The above is the method employed by the author some 10 or 12 years ago in prescribing the toe-in for the Daimler Cars. In the figures given by way of example, the camber angle 8 is, the author believes, rather overstated, and speaking from memory the difference I in. was in excess of that adopted ; obviously it would not be the same in every case. at UNIV CALIFORNIA SAN DIEGO on September 1, 2015pau.sagepub.comDownloaded from MOTOR CAR SUSPENSION AND INDEPENDENT SPRINGING. 695 One point of interest concerning splay or camber is the character of the wear observed in the tyres after a few thousand miles running. The wear of the tyre is, of course, lop-sided, due to the wheels not being square to the road, but, in addition to this, there is a curious intermittence in the incidence of the wear; the wheel becomes polygonal to some degree. Not only so, but the shape often bears some resemblance to a formed milling cutter, \" teeth \" being formed, tending in one direction like those of a circular saw.* The author has never seen this phenomenon fully or satisfactorily explained. 3 31. Tyres and Tyre Wear as Affected by Independent Springing.The essence of independent springing being that it disposes of the gyroscopic kick and consequent tremors and reactions on the steering mechanism, it is clear that the wheels must move in their own planes (or parallel thereto), planes which are in strict relationship to the suspended body of the vehicle. Modified forms of independent springing have been devised in which this condition is infringed, but these are compromises devised to overcome one difficulty a t the expense of another, a return, in greater or less degree, of the gyroscopic troubles. Such proposals need not be considered. When a vehicle having independent springing rolls, as when taking a corner a t speed, the angle of roll may be as much as 10 deg., and this will be the angle the road wheels make with the vertical. A plan of the centre line of the tread will then be an ellipse, as represented in Fig. 18, and the road contact (assuming full adhesion) will be a chord drawn parallel to the direction of the wheel, as in the figure. But the car is turning, so that this cannot be the full solution, since it would denote a tangential force in the wrong direction (i.e., towards the path centre, instead of away from it), and, following the line of argument given in $ 2 9 , we see that the steering angle of the wheel must be increased : the tyre-ground reaction must be reversed. Both steering wheels are affected in the same manner. This is a very serious matter. It means a very great increase in the apparent (effective) slip angle and a great increase in the tyre wear. Under these conditions, as the car heels over an increased movement will have to be given to the steering wheel to maintain the required track curvature. Putting it in another form, the car will tend to understeer. The impression experienced is that the tyre is failing to grip the road when the body careens. This can scarcely be the case, for the tread of the tyre still maintains contact with the road, and there is no reason to suppose that there is, under these conditions, any change in the coefficient of friction. Quantitatively, the position is (roughly speaking) as follows :- Assuming an angle of heel = 0 - 2 radian, a wheel 35 in. dia. overall and a value for the tyre (radial) yield - I in., the length of the contact area will be 12 in. The apparent slip angle will be something approaching, but probably less than, I in 7, or about 8 deg. This is only part of the story, for with axle-suspended vehicles there is a certain degree of \" slip \" also which cannot be accounted for in the same manner. * Probably caused by an alternation of adhesion and slipping. at UNIV CALIFORNIA SAN DIEGO on September 1, 2015pau.sagepub.comDownloaded from 696 THE INSTITUTION OF AUTOMOBILE ENGINEERS. FIg U. Pi#. 2s. Pi#. l6. at UNIV CALIFORNIA SAN DIEGO on September 1, 2015pau.sagepub.comDownloaded from MOTOR CAR SUSPENSION AND INDEPENDENT SPRINGING. 697 5 32. Effect on Steering.-The development of this heavy slip angle as a consequence of independent springing must be considered in relation to the problem of steering. If both front and rear be independently sprung, then it would seem that the increase in the slip angle might be arranged to affect both alike. This would mean that in cornering the movement required of the hand wheel to effect a given track curvature might be unaffected, the only difference being the attitude of the car in its relation to its path, but if there be a difference between the front and rear suspensions, the movement required to effect a given curvature as the car heels over might be increased many times with front independent springing only, or decreased or become negative with rear independent springing only. In the latter case it would be legitimate to regard the steering as being dangerous. But it is well not to dogmatise. We must not fall into the error of considering the steering of a car as steering by position, as though the wheel were pegged down ; such steering would be bad in any case. Whilst it is true that when turning at very low speeds the driver of a car does concern himself mainly with the position of his wheel ; when a t speed steering is effected by touch ; that is to say, by the force applied to the wheel and not by the measure of its movement. But for this fact, steering at high speed would be impossible. A car would steer like a water-fly in a series of jerky straights,* and a misjudgment of a few millimetres would result in disaster. PART 111. INDEPENDENT SPRINGING IN PRACTICE. 5 33. Mechanism : The Three Types.-It is possible to classify the different mechanisms used in Independent Springing as of three main types, of which there are subdivisions characterised by distinctive individual features. These types are :- I. That in which (a) the independent right and left hand stub axles are pivotally mounted on blocks or brackets which slide vertically under suitable restraint, on \u2018\u2018 pintles \u201d built into, or forming part of, the chassis frame, Fig. 23; or (b), Fig. 30. in which the stub axles are rigidly held by the sliding members which themselves are permitted a rotary motion, about the pintles provided to permit of their vertical movement. 11. That in which the parts carrying the stub axles are mounted on pairs of hinged or flexible outriggers forming a parallel motion, the axes about which movement is permitted being arranged in a fore and aft direction. This type has four variants, namely, (a) Figs. ~ o a and rob, also * Compare Proc. I.A.E., vol. ii., 1908. pp. zoo ct sup. at UNIV CALIFORNIA SAN DIEGO on September 1, 2015pau.sagepub.comDownloaded from 698 THE INSTITUTION OF AUTOMOBILE ENGINEERS. at UNIV CALIFORNIA SAN DIEGO on September 1, 2015pau.sagepub.comDownloaded from MOTOR CAR SUSPENSION AND INDEPENDENT SPRINGING. 699 Figs. zga and zgb, in which the outriggers on either hand take the form of triangular links each securely hinged at its base to a member of the chassis frame ; (b) Fig. 24, in which the outriggers are replaced by a pair of transverse laminated springs ; and (c) Fig. 25, in which only the upper outriggers are so dealt with, the lower outriggers remain ; and (d) Fig. 26, in which the lower outriggers only are replaced by springs. 111. In which the parts carrying the stub axles right and left are mounted on a parallel motion constituted by a pair of overhung cranks of which the axles are transverse to the chassis, Fig. 27. $ 34. In most cases, except where the springs are of the laminated type and form or act as a part of the linkwork, there are many differences in the manner in which the springs are applied. It is scarcely possible to extend the classification to include all these variations, they wiI1 be dealt with as individual cases as occasion may arise.+ Also, there are several modifications of type, especially as relating to rear independent springing which the author has thought it unnecessary to include. The author has himself been responsible for two forms of independent springing; the first of these dates from 1908 and refers to the alighting mechanism of an aeroplane. Another more ambitious effort was embodied in a design submitted to the Daimler Company in 1917 (see Appendix 111). $ 35. Independent Springing in Present Day Practice : Type I.Apart from the author\u2019s proposals, which cannot be included as examples of present day practice, it would appear that there is only one representative of type I (the \u201c pintle\u201d type), namely, the Lancia. The system of independent springing adopted by the Lancia is disclosed in Specifications of Patent 190,457 (1921) ; 197,310 (1922). and 222,460 (1923). Fig. 28 is a drawing taken from the first of these. Tf this is the earliest of the Paltents covering the Lancia system-Type I (b)-Lancia is four years later in date than the author. The Lancia claims are very narrow, which is usually a sign that the applicant has been faced with citations of prior grants. More recently the Alvis Company and ano. have filed patents covering a variantt of I (b), 311,083 and 311,084 (1928). The claims, as might be expected, are very narrow. A proposal embodying the double link system is embodied in Patent No. 419,562, granted to \u201c Daimler Benz Aktiengesellschaft,\u201d dated 1932. The feature of this particular proposal is the provision of a small degree of fore-and-aft elasticity i n addition to the vertical movement. The author has more than once heard it stated that this feature is desirable, but has not been able to satisfy himself as to * A pendix VI. t Tg e I.S. system actually used by the Alvis Company in production is Tyfie 1I.-There are many examples from which to choose. not of this type. at UNIV CALIFORNIA SAN DIEGO on September 1, 2015pau.sagepub.comDownloaded from"
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        "caption": "Fig. 54.",
        "texts": [
            " as stated by the author, the use of frictionless springs necessitates more elaborate and expensive damping mechanism. On page 689 the author states (5 24, No. 2 ) that one disadvantage associated with independent springing is that of increased tyre wear. Within my experience of independently sprung cars, tyre wear is no worse than with the orthodox type of springing, and I would say that tyre wear due to lateral reaction, where location is high, offsets that which occurs in independently sprung cars due to \u201c scrubbing \u201d when cornering. Referring to the underview of the Cadillac, Fig. 54, the author professed ignorance of the reason that the axes of the wishbone links converge towards the rear end. I believe this is done to harmonise the motion of the track rods with that of the links. Obviously there are other ways of achieving the same result. We have in this room to-night one of the early inventors of independent springing-Mr. Parnacott, who patented independent springing in 1912 ; his patents were almost as early as the author\u2019s patents. Further, a wishbone suspension of a type very closely akin to the modern American type was patented by Mr"
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        "caption": "Fig. 50.",
        "texts": [
            " 43 (u) and ( b ) . (This model has front-wheel drive.) 2. B I R M I N G H A M S M A L L A R M S . 3. B R O U L H I E T . Type I c. See Fig. 45. 4. C A D I L L A C . See Figs. 53 and 54, Plate SLII . 5. DELAGE. Type I1 D. See Fig. 51, Plate S L I . 6. E L V I D G E . Type I1 A. See Fig. 55. 7. F R A S E R N A S H . Type I1 C. See Fig. 46. 8. GORDON A R M S T R O N G . Type I11 B. See Fig. 47. 9. AfERCEDES-BENZ. Type I1 A. See Fig. 45. 10. ROLLS ROYCE. Type I1 A. See Fig. 49. 11. V A UXHALL. Type 111 C. See Fig. 50. Plate XL. The Vauxhall does not belong exactly to any of the types scheduled in 33. The box (3) in the figure contains a spiral spring, arranged to function much as in the Gordon Armstrong. The cranked links are pivoted in this box and not in cross members of the chassis, as in the Gordon Armstrong (this feature looks weak). As far as may be judged, the whole box is pivotally mounted, instead of the wheel only. Beyond the above the Humber and the Singer both employ the Gordon Armstrong or something very like it"
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        "caption": "FIG. 3.-Load-Extension Diagrams for specimens from bosses of wheel centres.",
        "texts": [
            " Test pieces 2 and 4 were taken from the boss parallel to the wheel bore and a t right-angles to one another. The average values obtained from the four tests of each cast show a great variation in the quality of the steel. Values as low as 24-38 tons per sq. in. were obtained, and in three casts only did the material give a minimum strength in excess of 28 tons per sq. in. at The University of Auckland Library on June 5, 2016pme.sagepub.comDownloaded from DEC. 1933. FORCE, SHRINE, AND EXPANSION FITS. 501 The typical load-extension diagrams in Fig. 3 indicate that the yield point of the material was not clearly defined. The similarity in nature and shape of the curves for test pieces 3 and 4 taken from casts Nos. 5 and 4 respectively should be noted. It provides evidence that the material a t certain points of the boss has been influenced by the mechanical processes in manufacture. It is apparent that the material had a low elastic limit and yield point. Test readings gave elastic limit values of 6.4 to 9 tons per sq. in., and yield point values of 11 to 16"
        ],
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    {
        "image_filename": "designv11_10_0001412_ie50197a005-Figure1-1.png",
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        "caption": "Figure 1-Experimental Bearing",
        "texts": [
            " used is rather narrow and may be readily covered by experiment. The following experimental data illustrate the utility of the foregoing method of correlation and include a study of the effects of changes in operating conditions (Z-V,\u2019P), clearance (l/\u2019c), and oil-feed pressure on one particular bearing. Unfortunately, data are not available on bearings of different sizes and characteristics. EXPERIMENTAL REsuLTs-The range covered by these oil flow measurements is indicated in Table 11, and the test bearing used is shown in Figure 1. The rate of flow was measured by feeding oil to the bearing from a large buret under the indicated supply pressure. The bearing was of bronze and mas supported on a hardened steel journal, the bearing load being directed downward. Clearance was varied by substituting a journal of different diameter. Tab le I1 FACTOR Viscosity ( 2 ) R. p m. (SJ Load ( P ) Diameter (d I Length (0 Clearance ( c ) Oil-feed pressure 011 flow -Range Covered by Oil-Flow LMeasurements MINIMLX MAXIMUM 12.5 centipoises 43"
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    {
        "image_filename": "designv11_10_0003947_pime_proc_1886_037_015_02-Figure54-1.png",
        "original_path": "designv11-10/openalex_figure/designv11_10_0003947_pime_proc_1886_037_015_02-Figure54-1.png",
        "caption": "Fig. 54. 1L Matchless \u201d Sliding Seat.",
        "texts": [
            " It is true that nearly all tricycles are fitted with the 1-shaped pin or some similar device for shifting the position of the seat fore and aft. But in few of them can the shifting be managed whilst riding; and all that a rider can do is to average a. sort of medium position to suit his comfort on a level, and up a steep gradient to rise from the saddle and stand wholly on the pedals, holding on by the handles. This can be done with tolerable convenience in tricycles of classes B, C, D ; but in many of class A it is out of the question, The \u201cClub \u201d sliding seat, Fig. 53, Plate 37, and also the \u201cMatchless\u201d sliding seat, Fig. 54, provide the means of varying the rider\u2019s position within certain limits whilst riding ; but in comparison with the considerable forward movement made by the rider of a Salvo or Rudge tricycle when he stands on the pedals for working uphill, it will be seen that devices of this kind wouId be cumbersome if they provided for the same extent of forward movement; whilst no smaller extent will fully meet the rider\u2019s requirements. A more complete solution of the problem is afforded by the adjustable double frame of Mr"
        ],
        "surrounding_texts": []
    },
    {
        "image_filename": "designv11_10_0000030_piae_proc_1935_030_039_02-Figure41-1.png",
        "original_path": "designv11-10/openalex_figure/designv11_10_0000030_piae_proc_1935_030_039_02-Figure41-1.png",
        "caption": "Fig. 41.",
        "texts": [
            " or so), and in part to the freedom permitted by the \u201cshackling of the springs in some cases, the side location is not so rigid ag to enforce the whole of the lateral motion on the body, as shown in the diagram : but in any case the quantity h, that is to say, the height of the side location above the ground level, should be kept as small as possible, for, other things being equal, the amplitude of the side wobble will he proportional to h. It is evident that the correct position for the side location is, theoretically speaking, on theground line itself; thus in Fig. 41 we will suppose that the body is carried on a cantilever suspension of the Lanchester type, exaggerated to the extent of carrying the axle down to within an inch or so of the ground, it is evident that no side oscillation will be conveyed to the body, and the wear and tear on the tyres will be correspondingly diminished. In designing suspension mechanism I have for the last ten years had the considerations now under discussion in view, hut I have never gone to the length of lowering the point of side location to the extent illustrated in Fig. 41, such an extreme would scarcely be justified in view of the fact that any small side throw can well be taken by the lateral elasticity of the springs combined with a slight yielding of the tyres. It is evident, how- * This kind of race is very rarely heard of a t the present time, probably for the reason that it proved too destructive to the tyres. at UNIV CALIFORNIA SAN DIEGO on September 1, 2015pau.sagepub.comDownloaded from MOTOR CAR SUSPENSION AND INDEPENDENT SPRINGING. 709 ever, that any increase of h above some critical value will begin to cause discomfort to the passengers and damage to the tyre fabric"
        ],
        "surrounding_texts": []
    },
    {
        "image_filename": "designv11_10_0000010_1.1707623-Figure1-1.png",
        "original_path": "designv11-10/openalex_figure/designv11_10_0000010_1.1707623-Figure1-1.png",
        "caption": "FIG. 1. Mechanical system,on which dissipative and con servative forces are acting.",
        "texts": [
            " For p particles there are pep -1) /2 such relative speeds. Other useful forms of P are easily obtained. It is clear, of course, that for a system acted upon by two or more types of forces, the proper power function is merely the sum of power func tions corresponding to the individual types. 2 See reference 1, page 230. VOLUME 16, SEPTEMBER, 1945 EXAMPLES ILLUSTRATING THE USE OF P (1) Consider two small masses ml and m2 con nected with a light rigid rod and moving in contact with an inclined plane as shown in Fig. 1. This is a problem of three degrees of freedom and we shall find, by means of a P function, the generalized forces corresponding to coordinates x, y, and 8 where x, y might, if so desired, locate the center of gravity of the dumb-bell. Assume gravity acting in the direction indicated and further, because of the contact of the masses with the plane, assume a drag on ml given in magnitude by a8l n1 and a drag on m2 given by b82 n2 \u2022 It follows from (14) and (16) that; P= b(X22+Y22) (n2+1)/2 n2+ 1 where Xl, Y1 and X2, Y2 are the rectangular coor dinates of ml and m2, respectively"
        ],
        "surrounding_texts": []
    },
    {
        "image_filename": "designv11_10_0003947_pime_proc_1886_037_015_02-Figure73-1.png",
        "original_path": "designv11-10/openalex_figure/designv11_10_0003947_pime_proc_1886_037_015_02-Figure73-1.png",
        "caption": "Fig 73.",
        "texts": [
            " I n the Spinaway tricycle designed by the author this defect is obviated, as will be described later on. In the Grosvenor tricycle, Fig. 30, Plate 27, the wheel on the same side as the pilot is not a driver, and is small in diameter ; but the disadvantages of this arrangement are considered to be compensated by the system of compounding for two riders side by side. The Cunard two-track tricycle has similarly only one driver ; but the idle wheel is not much reduced in size, and is on the opposite side to the pilot wheel. Class D. Rudge Tricycle, Fig. 31, Plate 28, and Fig. 73, Plate 44. -This is essentially a single driver. The three wheels are arranged in two tracks, the large driving wheel being on the left hand and two small wheels on the right hand. Here it is obviously impossible to put more than half the load on the driver, whilst the two smaller wheels carry tho remainder divided between them in the inverse proportion of their distances from the seat. But although only half the load can be put on the driver, this is yet a larger amount than in any of the three preceding classes A B C when only one wheel is used as driver"
        ],
        "surrounding_texts": []
    },
    {
        "image_filename": "designv11_10_0000005_1.1707241-Figure6-1.png",
        "original_path": "designv11-10/openalex_figure/designv11_10_0000005_1.1707241-Figure6-1.png",
        "caption": "FIG. 6. Forces acting on the journal because of pressure distribution in the lubricating film when the lubricant source is at the base of the bearing and has a strength less than the \"cntical.\"",
        "texts": [
            " While in principle such a restriction is quite artificial, it turns out that even when the angle a is allowed to vary, it wiII stilI be limited, by the require ments of equilibrium between the forces due to the lubricant source and the journal rotation, to values exceeding 70 0 except for high journal eccentricities. The variability in the angle a has permitted an extension of the friction coefficient curves to smaller values of S, but over the same range of variables the results given here agree with those previously developed in everything except quantitative detail. Since the source is to be taken here at the base of the bearing, the geometric system will corre spond to that shown in Fig. 6, at least as long as the rotational effects are the predominating elemen ts in determining the journal displacement. The conditions to be imposed upon the load components of Eqs. (17) and (18) for the present case will therefore be: (30) Upon eliminating (3 from the resulting equations, VOLUME 10, JANUARY, 1939 one obtains an expression involving qo, a, and 1/ which is identical with Eq. (22), except for a change in sign on the right side. In solving this equation for a as a function of qo, it is found that here the behavior of the system will depend primarily upon the magnitude of the dimension less flux strength qo. For small values of qo the forces resulting from the pressures in the film will be as shown in Fig. 6, with a lying between 11'\" and 311'\"/2. When go has the critical value given by: 1/411'\"(1-2e-wo), the force F wiII be great enough to support the journal without any assistance from R. The journal will then become concentric with the bearing and the friction coefficient wiII be given by the Petroff line (Eq. (29\u00bb for all values of S. And when qo exceeds this critical value the journal wiII rise above its central position, and a will fall to values less than 11'\"/2, as shown in Fig. 7. To calculate the values of the Sommerfeld variable for the present case one may use exactly the same formula as when the source is at the crown of the bearing, namely, Eq"
        ],
        "surrounding_texts": []
    },
    {
        "image_filename": "designv11_10_0003967_t-aiee.1918.4765582-Figure1-1.png",
        "original_path": "designv11-10/openalex_figure/designv11_10_0003967_t-aiee.1918.4765582-Figure1-1.png",
        "caption": "FIG. 1 FIG. 2",
        "texts": [
            " Shale and clay are most commonly used for obtaining the argillaceous material for Portland cement. Cement rock mentioned above, as well as blast furnace slag, are also used as a source of argilla- IROCK CRUSHER 2 SCREEN 3 ROCK RE-CSHERS 4 WASH MILL 5 AGITATOR A MtIING TANK 7 COM-EB MILL 7K PRELIMINA GRINDER)ALTERNATE TO r~~~~~ ~7B FINE GRINDER AR1 7'1 8 STORAGE TANKS[laj 19 ROTARY KILN 10 ROTARY COOLER 11 GYPSUM ADDED L _ _s 12 COM-PEB MILL U p 12A PRELIMINARY GRINDER ALTERNATE TO 12 12B FINE GRINDER113 STOCK HOUSE & PACKING MACHINES 14 COAL CRUSHER 15 COAL DRYER 16 COAL GRINDER EL. FIG. 1 ceous material. Blast furnace slag, like cement rock, contains a considerable proportion of lime and has the further advantage that this lime is found as calcium oxide instead of the carbonate; therefore, the heat necessary to dissociate the carbon dioxide gas from this part of the lime is not required. The preliminary crushing of limestone, cement rocks and shale is ordinarily done in the crushers of the gyratory, jaw or roll type. Materials may be ground either in the wet or dry state. Fig. 1 shows a typical flow sheet for a wet mill and Fig. 2 for a dry grinding mill. In a dry grinding plant, the two classes of materials are preferably dried separately and then weighed, after which they are ground. In a wet grinding plant, the materials are generally measured or weighed in their natural state as excavated, and then ground. Where shale or cement rock is used as the argillaceous material, it must be crushed in rock crushers. In the past, it has been the practise in certain wet grinding cement plants to dry the clay in order better to store and handle it, and also to eliminate gravel and other foreign material. The bettor practise, however, is to dump the clay in its natural state into a wash mill where sufficient water is mixed with it to allow the heavy pieces of gravel to settle out, and also to form a slurry which can easily be stored in tanks. The flow sheet, Fig. 1, for a wet grinding cement plant shows a wash mill installed for handling the argillaceous material. Wash mills are used only for clays, marls and similar materials, which, by mixing with water, can be kept in suspension. If shale were used as argillaceous material, a crusher of some type would have to be provided instead of a wash mill. The same general type of grinding machinery can be used for either wet or dry grinding. In the past, it has been customary to use a preliminary and a finishing grinder; but, the latest 1534 WILLIAMSON: MOTORS IN CEMENT INDUSTRY [Nov",
            " It is thus apparent that the synchronous motor is merely a convenient substitute for the mechanical coupling when the alternator is situated at some distance from the rectifier, i. e., when the alternator is in a central power house and is used for supplying current to other pieces of apparauts. It is desirable to keep this point clearly in mind, that the two methods of driving the rectifier are almost identical, so far as the electric circuit in question is concerned. Near the periphery of the revolving disk, but separated from it by a small air gap, four shoes or elongated conductors are placed, one for each quadrant. (See Fig. 1) The disk carries four \"contactors, \" these so-called contacts being made through the air gaps by means of arcs. These revolving points might preferably be called \"arcing-points\" or \"arcing-contactors.\" The general arrangement of the disk and shoes and a wiring diagram are also indicated in Fig. 2. It is not feasible at these high peripheral speeds, to have the shoes and contactors in actual contact,-we wish it were. Two wires connect the transformer high-tension terminals to two shoes spaced apart 1574 MOTORS IN CEMENT INDUSTRY [Nov"
        ],
        "surrounding_texts": []
    },
    {
        "image_filename": "designv11_10_0000003_1.1697680-Figure1-1.png",
        "original_path": "designv11-10/openalex_figure/designv11_10_0000003_1.1697680-Figure1-1.png",
        "caption": "FIG. 1.",
        "texts": [
            " In this equation /1-, h, U, and P are the oil vis cosity, the oil-film thickness, the slider velocity, and the oil pressure at any point on the slider surface. If the substitutions are made: 483 [This article is copyrighted as indicated in the article. Reuse of AIP content is subject to the terms at: http://scitation.aip.org/termsconditions. Downloaded to ] IP: 155.97.178.73 On: Fri, 28 Nov 2014 06:18:57 where Land B are the length and width of the slider, ho represents the oil-film thickness at the outlet edge, and fJ is a function of Xl (see Fig. 1) ; and if viscosity is assumed constant, the equation becomes (2) In Eq. (2), N is the ratio of slider length to slider width (LIB) and A is the product 6J1.ULlho2 containing all the dimensional terms. The new variables Xl and Zl are the fractional distances along the length and width of the slider, and range in value from 0 to 1.0. It will now be assumed, following the method in reference 3, page 141, that the pressure at any point can be expressed as the product of two functions P=A -!(XI) \u00b7f(ZI)"
        ],
        "surrounding_texts": []
    },
    {
        "image_filename": "designv11_10_0000005_1.1707241-Figure7-1.png",
        "original_path": "designv11-10/openalex_figure/designv11_10_0000005_1.1707241-Figure7-1.png",
        "caption": "FIG. 7. Forces acting on the journal because of pressure distribution in the lubricating film when the lubricant source is at the base of the bearing and its strength exceeds the critical value.",
        "texts": [
            " For small values of qo the forces resulting from the pressures in the film will be as shown in Fig. 6, with a lying between 11'\" and 311'\"/2. When go has the critical value given by: 1/411'\"(1-2e-wo), the force F wiII be great enough to support the journal without any assistance from R. The journal will then become concentric with the bearing and the friction coefficient wiII be given by the Petroff line (Eq. (29\u00bb for all values of S. And when qo exceeds this critical value the journal wiII rise above its central position, and a will fall to values less than 11'\"/2, as shown in Fig. 7. To calculate the values of the Sommerfeld variable for the present case one may use exactly the same formula as when the source is at the crown of the bearing, namely, Eq. (23). The previously discussed effe'tt of the strength of the lubricant source on the position of the center of the journal is shown graphically in Fig. 8(a) for W= 1 and S=0.05. The arrow indi- 55 [This article is copyrighted as indicated in the article. Reuse of AIP content is subject to the terms at: http://scitation.aip.org/termsconditions"
        ],
        "surrounding_texts": []
    },
    {
        "image_filename": "designv11_10_0000029_bf02565548-FigureII-1.png",
        "original_path": "designv11-10/openalex_figure/designv11_10_0000029_bf02565548-FigureII-1.png",
        "caption": "Fig. II--Glass Bath Vessel for Modified HZheeler-Swift Stability Test, Permitting Visual Determina-",
        "texts": [
            " All of the o t h e r curves in Wheeler's p a p e r show the same characteristics, and the peak of the color curve in the case of corn oil is very extreme, the color go.~oo / / / a4 ing from 9 to 100, zoo / then dropping quickly to a value of 2. t~*; -/_Fix Appara tus ~ / / \" , x, accurate means of determining the endpoint without mak- ing peroxide number determinations, an apparatus was designed in which the principal feature is a glass bath vessel, permitting visual examination of the tests without the necessity of removing them. The apparatus is shown in Figure II, which, it is believed, illus- Ot'/I 7~t O d t CoL ~, Ifl~d. giving a detailed description. The principal difficulty was to make the vessel vapor-tight to avoid too much 10ss of water when the tests had to run overnight. This result was attained by cutting a strip of ~ - in . sponge rubber 2-in. wide, and sewing the ends together to form a tion of End Point. O. S. C., N e w Or leans , M a y 28 a n d 29. 1936. sort of bushing between the walls of the beaker and the metal collar soldered to the cover"
        ],
        "surrounding_texts": []
    },
    {
        "image_filename": "designv11_10_0000030_piae_proc_1935_030_039_02-Figure58-1.png",
        "original_path": "designv11-10/openalex_figure/designv11_10_0000030_piae_proc_1935_030_039_02-Figure58-1.png",
        "caption": "Fig. 58.",
        "texts": [
            " The author approves of independent suspension at the front, but not a t the rear of a car. We feel, however, that the reasons given do not do full justice to independent suspension. Little has been said of the great advantage of a decrease in unsprung weight. As this factor has not been considered in its essentials, we beg the author\u2019s pardon for introducing a little mathematics in support of our claims. It is rather interesting to consider the equation of motion of a system comprising of a mass MI supported by a wheel and tyre and a mass M, supported above 1\\1, by a spring (Fig. 58). If the mass M, is displaced by distance S, and then released, the differential equations describing the subsequent motions are This is, of course, a somewhat loosely worded description. The motion would be better represented by three Fourier\u2019s series, two of them representing the longitudinal motions and one the transverse motion. This can easily be proved by the elements of periodical analyses and verified on a bouncing machine. at UNIV CALIFORNIA SAN DIEGO on September 1, 2015pau.sagepub.comDownloaded from MOTOR CAR SUSPENSION AND INDEPENDENT SPRINGING"
        ],
        "surrounding_texts": []
    }
]