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Viewing 8131 to 8160 of 8253
1929-01-01
Technical Paper
290046
JOHN SNEED
IF brake-lining manufacturers would insist on holding the values of friction coefficients to 0.3 or 0.4, many of their troubles would cease, in the opinion of the author, who asserts that the main objections to high friction-coefficients are rapid wear, greater liability to cause scoring, and instability. The first results of tests on molded brake-lining materials were so superior to tests on woven material that further development of molded materials was carried on. Regardless of the type or make of molded material tested, it was found that the friction-coefficient value remained much more uniform than did that of woven material and that, without exception, the friction value and general characteristics of molded material were not changed by wear conditions. Molded material shows longer life than woven material, according to tests, and the author thinks that possibly this is because of the completeness of the saturation of the molded material.
1929-01-01
Technical Paper
290045
R. H. SOULIS
FIRST reviewing briefly the history of molded brake-lining, the author states that the introduction of molded lining has, until recently, met with considerable opposition. After the first volume-production adoption in 1924, there were no further adoptions of the strictly molded types in production until 1927, when the trend in brake design seemed to change suddenly from the external type to the internal type of brake. The present movement toward the use of molded brake-lining was brought about through the inability of woven lining to meet the exacting demands of some of the newer types of internal brake. In the author's opinion, the molded type of lining has more nearly fulfilled the present requirement of internal brakes than has any other type. He states that at least seven different brands of molded lining are now on the market, and that three of them are in large-volume production.
1929-01-01
Technical Paper
290022
W. T. DONKIN, H. H. CLARK
THE electric telemeter presents an excellent means for investigating the phenomenon of valve-spring surge. Basically, the telemeter is composed of two differentially connected stacks of thin carbon discs so arranged that, when the apparatus is subjected to strain, the pressure is increased on one stack and decreased on the other. Each stack forms one arm of a Wheatstone's bridge, and the resistances of the stacks vary with the pressure on them, thus slightly upsetting the balance of the bridge. If an oscillograph galvanometer-element be substituted for the usual bridging instrument, the arrangement will be found suitable for making photographic records. To study valve-spring surge, the telemeter is connected across the points of a stiff C-spring, one end of which is held against the valve-spring in such a way that vibrations of the spring are transferred to the C-spring and thence to the telemeter.
1929-01-01
Technical Paper
290076
T. H. MACDONALD
TWO distinct phases of the subject are the physical and the economic, both of which are included in the conclusions stated in the paper, based on investigations made by the Bureau of Public Roads. It is as pertinent to inquire what effect the highways have on the motor-vehicle as to inquire what effect the motor-vehicle has on the highways. Mutual adjustment must be made if real economy is to result. Two general conclusions that may be drawn from the observations presented are that the six-wheel vehicle offers a desirable and effective answer to (a) the problem of the load in excess of the normal desirable limit of weight for the four-wheel truck, and (b) the problem of the load equal to the heavier four-wheel truck in areas where road conditions do not permit the maximum wheel-load concentration.
1929-01-01
Technical Paper
290075
G. M. SPROWLS
1929-01-01
Technical Paper
290074
L. R. Buckendale
MANY interesting problems in design are presented in the application of four-rear-wheel drive to a six-wheel vehicle. As axle design is intimately related to the rest of the chassis construction, the axle builder is concerned with the type of spring mounting, the method of taking the torque, and the distribution of the load. The author specifies a number of factors that positively must be taken into account and provided for in any construction that is to prove successful. He then shows by photographs and describes a number of rear-end four-wheel-drive constructions that have been built and put into operation.
1928-01-01
Technical Paper
280053
A. MOORHOUSE, W. R. GRISWOLD
BECAUSE of the increased engine-speed and the limitations of progress by the previous method of designing valve-springs, Packard engineers entered upon fundamental studies of valve-spring behavior and of the influence of stress range upon durability. Various theories of the dynamics of valve-spring surge were investigated, and one was found which seems to agree fairly well with the observed phenomena. Jumping of valve push-rods and spring failures that could not be explained by the static analysis of spring design are accounted for by the dynamic analysis, which serves as an improved basis for design. Finding it impossible to design a single spring to meet the conditions, within the space limitations, a double spring with interlaced coils was designed. Descriptions are given of the provision for mounting the ends of the springs and the methods of assembly and inspection.
1928-01-01
Technical Paper
280068
ETHELBERT FAVARY
ASSERTING as a premise that highway legislation should be purely a matter of economics, the author draws a comparison between the costs of building a cheap road and hauling with 2½-ton trucks and building a heavier road and hauling with 5-ton trucks. He shows by this illustration that the latter proceeding is the more economical. Most States permit gross weights of vehicle and load that make it possible to haul pay-loads of about 5 tons. If 5-ton trucks show a saving in transportation costs over 2½-ton trucks, still larger capacity four-wheel trucks might show a corresponding saving over 5-ton trucks, from which it might be argued that all roads should be built sufficiently strong to carry the heavier vehicles and loads without damage. But it is pointed out that there are a great many secondary roads on which traffic is light, and that it is uneconomic to build roads and roadbeds stronger than is warranted by economic needs.
1928-01-01
Technical Paper
280052
W. T. DONKIN
A PAPER on Valve-Spring Surge,2 by Mr. Donkin and H. H. Clark, which was presented at the Semi-Annual Meeting of the Society in May, 1927, was presented during the last season by Mr. Donkin at Section meetings in Buffalo, Chicago and Milwaukee. At a meeting of the Cleveland Section he delivered a paper on Valve-Spring Design, part of which is printed herewith. The remainder was a duplication of the Semi-Annual Meeting paper. At each of these Section meetings the subjects of valve-spring surge and valve-spring design were discussed. Some of the discussion was upon part of the original paper in which were compared two valve-springs, the original design vibrating noisily and the improved design being satisfactory.
1928-01-01
Technical Paper
280017
H. D. HUKILL
THE use of a power medium in brake control points at once to the possibility of simplifying the brake system so that its characteristics, once established, can be expected to remain uniformly effective throughout extended periods without adjusting, with correspondingly long life of brake-linings. The author says also that, if the greater retarding effect possible with mechanically operated four-wheel brakes is to be fully realized, it is necessary to do one of three things: increase the pedal pressure, increase the brake leverage and consequently the pedal movement, or increase the “self-energizing” effect. The vacuum-type brake described is stated to be an amplifier which provides power to supplement muscular strength and assists the driver to apply the service brake, thereby reducing the required pedal stroke and pedal pressure without interfering with the regular service-brake hook-up.
1928-01-01
Technical Paper
280018
JOHN SNEED
THE theory and characteristics of brakes of the Steeldraulic system are set forth and their application in practice is explained. Self-energizing brakes are said to be desirable because they allow large clearances, low pedal-effort and frictional coefficient and, if properly designed, give a high degree of efficiency with smooth uniform action. To accomplish these results, the controls should deliver equal and accurate actuation to all brakes at all times, be designed to minimize the possibility of becoming inoperative on account of dirt and rust, require no servicing, be noiseless and of good appearance, and remain unaffected by climatic changes. Shoe design should allow very liberal limits and tolerances in wheel, axle and drum assemblies, without causing erratic brake-action or noises. The brake hook-up should follow the simplest line and use the least number of connecting links.
1928-01-01
Technical Paper
280002
D.SENSAUD DE LAVAUD
THIS paper is an attack on the usual system of front suspension of an automobile and a proposal to substitute independently sprung front wheels for the conventional assembly of wheels, rigid axle and semi-elliptical springs. Mounting of the front wheels on a solid axle is a survival of horse-drawn-vehicle days which the author asserts is so unsatisfactory from the standpoint of rational mechanics that it should long ago have become a memory in the automotive industry. To the complex action and reactions of the axle, oscillating between the springs and the tires, and of the wheels, with their gyroscopic effects, are attributed the phenomena of shimmy and wabble that have become so disconcerting and even dangerous since the advent of low-pressure tires and front-wheel brakes. The origins of the various abnormal vibrations are analyzed, the effects of damping and of friction are discussed, and the part played by the conventional steering-gear and steering connections is considered.
1927-01-01
Technical Paper
270021
J. F. PURDY, R. B. DAY
TIRES of high shock-absorbing capacity greatly reduce the blows delivered to roadways by heavy vehicles and the reactions on the vehicles; they also absorb most effectively the shocks in a vertical direction that are the cause of the greatest discomfort to passengers. With a view to making a laboratory study of these shock-absorbing properties of tires, an instrument called a bounce-recorder has been devised and is described. This instrument records the paths followed by tires in passing over obstacles placed in their way. From these records, the vertical acceleration of a tire at any point of its flight can be determined, the purpose of doing so being twofold, namely, to develop an accurate and fairly rapid means of ascertaining the relative shock-absorbing capacities of tires by the acceleration method and to find out whether load-deflection tests made on the Olsen testing-machine could be used for the same purpose.
1927-01-01
Technical Paper
270020
G. L. SMITH
BRAKE action extends from the foot-pedal through various connections and devices to the point of contact of the braked wheel on the ground but, although brake-development work has been extensive for that portion of the brake mechanism which extends from the foot-pedal up to the point of application of brake pressure, the author says that beyond this point practically no improvement has been made. He says further that a study of brakes and the retarding forces they exert on the road surface reveals the primary cause of brake troubles, and then analyzes the design of an efficient braking-system for automobiles, first outlining the ideally perfect mechanism without regard to mechanical limitations.
1927-01-01
Technical Paper
270052
H. D. CHURCH
The paper deals primarily with internal wheel-brakes for trucks and motorcoaches, but passenger-car brakes with similar characteristics are considered possible. A simple two-shoe internal-expanding type developed mainly by empirical methods is found to be the most practical solution in spite of relatively low circumferential contact. Self-energization is necessary to reduce driver effort with normal pedal-travel. The factors controlling self-energization are explained in detail, and the effect of difference in the coefficient of friction of brake-linings is noted. Distortion of brake-drum and brake-shoes must be limited by a drum of heavy section and by extremely rigid shoes. Rotation of cam with respect to self-energizing shoe should tend to deflect the toe of shoe away from brake-drum surface. A floating cam is necessary to balance unequal wear on the brake-shoes and assure adequate braking with normal pedal-pressure.
1927-01-01
Technical Paper
270043
TORE FRANZEN, S. P. HESS, CLARK A. TEA
1927-01-01
Technical Paper
270047
S. VON AMMON
A REPORT on the investigation of brake-lining materials by the Bureau of Standards was made by the author in 1922. The present paper gives information on work done in this field since that time. It places on record a summary and discussion of various test-methods and equipment at present employed by brake-lining manufacturers and others in the automotive industry. The difficulties connected with this work, resulting from the varying characteristics of brake-lining materials, are brought out. It is shown that some of the test methods in use do not furnish a basis for ready or fair comparison of different brake-linings. Other test procedures are so limited as to give only an incomplete picture of the characteristics of the brake-linings under conditions met in service; therefore, the test schedules generally require readjustment and amplification because a full and satisfactory knowledge of these materials can be obtained in this manner only.
1927-01-01
Technical Paper
270023
K. L. HERRMANN
THE author enumerates and describes various inter-related movements of the front end of the car that are commonly known as automobile shimmy. A long list is given of experiments made in an attempt to correct the trouble. These did not produce consistent results but showed that caster angle acts as a considerable influence, while the influence of camber and toe-in seems to be more on tire wear than on shimmy. Lubrication of springs and conditions affecting the free motion of the steering pivots have some influence but the author sees imperfections in the tires as fundamental causes. The nature of the road is also important, particularly of concrete roads having regularly spaced depressions at joints. Some of the tire imperfections are described and blame is placed on the tire makers for being less thorough in their methods of testing and inspection than are car manufacturers.
1926-01-01
Technical Paper
260051
C. W. BEDFORD, ERNEST BLAKER
Premature failures in the summer of 1925 of inner-dual motorcoach tires and tubes on 20-in. wheels in which the brake-drum was directly under and close to the rim caused the rubber companies to undertake development work on tire beads, flaps and tubes; but no solution of the problem was to be found by a change of the rubber compound. The need for definite information regarding actual tire temperatures developed in road service led to extensive joint tests in Florida early in 1926 by a tire and a wheel company. In these tests a brake-drum temperature was maintained as nearly as possible constant at 475 deg. fahr. above atmospheric temperature by successively accelerating the car and applying the brake. When it was judged that this temperature had been reached, stops were made to take thermocouple readings of the temperature.
1926-01-01
Technical Paper
260050
J. A. BUCHANAN
In motor-truck impact-reactions, the unsprung component is generally the major quantity and the force depends on four principal variables: tire equipment, load, speed and road roughness. The tire equipment that utilizes the greater time of duration for the reaction will cause the lower impact-forces. Increases in load, speed and road roughness increase the impact-reaction. Poor tire-equipment on rough roads may cause forces of 35 tons to be borne by both the truck and the road. Pneumatic tires rarely allow reactions greater than twice the static wheel-load. The impact reactions of a six-wheel truck approximate one-half those of an otherwise equivalent four-wheel truck having the same pay-load. Fifty per cent loss in the overall height of the tire multiplies the impact reaction by 2.5. Rolling resistance varies with the speed, the tire equipment and the road surface, and may reach a value of one-sixteenth the wheel-load.
1926-01-01
Technical Paper
260045
F. C. Mock
This is an analysis of spring action such as occurs on an automobile driven on a highway having bumps and depressions, a discussion of the requirements of spring-recoil checking devices, and an account of experiments made with a car on which different combinations of springs of various lengths and flexibilities were used and the distribution of weight on the frame was varied. Spring action was analyzed previously by means of small models that simulated the suspension and weight distribution of a motor-car. The compression and recoil action of springs and their relation to the travel of the car as represented by the time element are discussed. Although the more-flexible springs absorb the bumps better, it is shown that their recoil is greater unless it is damped by a shock-absorbing device.
1926-01-01
Technical Paper
260021
H H ALLEN
Variation of the retarding forces on the brakes of automotive vehicles for a given pedal position or a given pedal pressure is frequently due to the ordinary wear of the brake-linings or other parts and may readily be prevented by periodic inspection and adjustment. Sometimes, however, sudden and serious reduction in retarding ability occurs when the brakes have been applied for comparatively long periods with short cooling-intervals or when the brakes have been wetted or oil has reached the linings. Laboratory tests of braking materials have shown that a marked increase in temperature will generally result in a reduction in the coefficient of friction of asbestos textile brake-lining materials and that oil and water have a similar effect of a temporary character.
1926-01-01
Technical Paper
260048
N. E. HENDRICKSON
Substitution of scientific data obtained by experiment for the mere opinions long since prevailing about the respective values of arguments pro and con in regard to the interleaf friction of springs, the effectiveness of many leaves versus few leaves, the lubrication of springs and kindred subjects, was the objective of the author and the results he has secured since the start of the experimental work early in 1924 are set forth. Tests were conducted with springs having leaves varying in number from 1 to 14 and, in all cases, both when dry and when copiously lubricated with thin oil. All the variable factors were included during the progress of the experiments, the number of combinations possible being indicated by the fact that about 250 tests were made and more than 50 different springs were used.
1926-01-01
Technical Paper
260019
FRED H GLEASON
Greater length of chassis-life, improved riding and handling qualities and the elimination of annoying squeaks and rattles are the major benefits sought in chassis lubrication, and these are claimed to be achieved by an effective system which derives its lubricant from a central source. The paper supplements a previous one, and is in the nature of a progress report. Experimental work since that of 1924 is described, and the improvements in the system resulting therefrom are cited. Layouts and constructions used in connection with this central-source chassis-lubrication system are illustrated, and a short description of the salient points is presented. Oil pressures maintained in the different parts of the system are discussed, possible leakages of the oil are specified, desirable viscosities of the oil are mentioned, and the construction of the tubing and the various special connections is explained. The lubrication of special parts of the chassis is also covered.
1925-01-01
Technical Paper
250049
A F MASURY
Reviewing the present transportation problem in regard to its demand for larger motor-vehicle units of transport, the author says that the motor truck is proving to be successful in the movement of practically all local freight and that the motorcoach is meeting with greater and greater favor as the logical vehicle with which to meet the demands of the traveling public for better transportation facilities. Although the present types of motor vehicle are serving present needs in a more or less successful manner, when strict economics becomes the standard for measuring road transportation a demand will be made for vehicles that will accommodate the maximum freight or passenger loads in the minimum of street space. At speeds governed within limits of safety they will offer the utmost comfort for passengers and will haul perishable goods over long distances in quantities large enough to assure strictly economic operation.
1925-01-01
Technical Paper
250048
J W WHITE
Experiments with hydraulic steering-control with the object of preventing or reducing shimmying and tramping were made by the author, who asserts that the elimination of backlash by doing away with mechanical joints and by holding the front wheels as rigid as the rear wheels has been amply proved by the results to be a long step in the right direction. With a Marmon car fitted with an hydraulic steering-system and driven over the roughest roads it was impossible to discern any front-wheel wabble as the car approached and passed the observer.
1925-01-01
Technical Paper
250046
F C MOCK
Riding-discomfort from road inequalities can be divided into two general classes, of which the first, direct discomfort, includes jolts, jars and unpleasant forces that occur during, and as the immediate result of, passage over the inequality. The extent of these discomforts depends chiefly upon the magnitude of force exerted against the passenger and the rate at which this force is applied. The second type of discomfort may be called potential and includes such motions of the car, following, and resulting from, passage over the road inequality, as lead to “not holding the road,” extreme pitching motion, or throwing the passengers off the seat and the like. This potential discomfort is more or less proportional to the amplitude of spring motion and the extent to which this motion interferes with the uniform straight-forward progression of the car. The springs of a vehicle supported at the front and the rear seldom operate individually.
1925-01-01
Technical Paper
250020
E A De Waters
In the summer of 1922 the Buick Company began experimenting with balloon tires. The first tires tested, being four-ply and 32 x 6.20 in. in size, produced a galloping action that was sufficient to prejudice the company's engineers against them, and the tests were discontinued. In addition to the galloping effect, other difficulties encountered included those usually present in steering, the development of wheel shimmying to a serious degree, the lack of proper clearance for external brakes because of the small 20-in. wheels, the excessively rapid wear of the tire tread, and the greater susceptibility to puncture. Leaks because of the pinching of the inner tubes also occurred. When, later, a set of 5.25-in. tires was tried on a smaller car, the galloping was noticeably less; but punctures were more numerous than was the case with high-pressure tires.
1925-01-01
Technical Paper
250012
E W STEWART
In determining the characteristics of coiled wire springs, if all the component forces, including those .of torsion, transverse shear, tension, and compression, are considered, the calculation may be complicated and involved, but for practical purposes of design all can be ignored except torsion. The calculation then becomes simple. The underlying principles of the formulas that express the torsional characteristics of an ordinary helical spring are the same as those that govern torsion in a straight shaft; and the fact that the result would be the same if the shaft or wire were twisted in the opposite direction makes it clear why a coiled spring has the same stiffness in either compression or extension so long as all the coils remain open. In Begtrup's formula, as given in the handbooks, the only unknown factor is the modulus G, which is variously stated to be from 10,000,000 to 14,000,000 lb.
1925-01-01
Technical Paper
250017
W R STRICKLAND
Although wheel wabble, even with high-pressure tires, is of ancient origin and the general methods of controlling it have been well understood, its importance among present-day problems is due to the fact that the recognized specific for its treatment, namely, increasing the air-pressure in the tires, has been denied. Shimmying, as generally applied, includes wabble, or the sidewise vibration of the front wheels about the knuckle-pin, and tramping, or the bouncing of the wheels vertically, alternately on the two sides. In addition to discussing the advantages and disadvantages of the low-pressure tire, the author has enumerated the results of tests, some of which have been obtained from original research work by himself, others from the literature on the subject, with a view to determining whether shimmying is caused by defects in design, and what are the effects when certain modifications are introduced.
Viewing 8131 to 8160 of 8253