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1971-02-01
Technical Paper
710044
Rudolf Limpert
An engineering analysis of tractor-semitrailer braking is presented in terms of the utilization of available tire-roadway friction. The effects of load transfer on the tandem axle suspension upon braking performance are discussed. The physical relations are derived that allow the determination of an improved brake force distribution among the axles of the combination as a function of the geometric and loading configuration. Tractor-semitrailers operating on our highways have braking efficiencies as low as 60%. Increase in braking performance can be expected provided the brake force distribution is improved. Eliminating the front brakes without changing the base line distribution has an unfavorable effect upon the braking performance of the combination.
1971-02-01
Technical Paper
710041
Gerald D. Robinson
Automotive seat spring assemblies are now subject to much closer tolerance control due to the new government safety standards which, in addition to outlining specific mounting force resistance specifications, have added such tolerance complicating components as front seat back latches and headrests. Since these seat assemblies are made in many locations far remote from the automotive assembly plants, it is imperative that the quality control system operate at maximum effectiveness, using gaging and sampling techniques that cut rejects to an absolute minimum. This paper discusses a new quality control system that has been installed in three different seat manufacturing plants.
1971-02-01
Technical Paper
710057
Daniel Zibello, Frank M. Thompson
A Procedure for Optimizing Elastomeric Mountings (POEM) is described which provides a systematic investigation of vehicle ride performance as a function of both the spring rate and damping of a selected mounting. POEM assumes the mounting design and its placement on the vehicle have been established. Then nine mounts satisfying a three-level factorial experiment in spring rate and damping are evaluated. Evaluations can be subjective or objective and can employ laboratory simulators or road tests. Dynamic properties of the mounts are measured at simulated on-car conditions. Computer, step-wise regressions of the data are performed to define any performance/property relationships. Final regression equations are contourized by computer, displaying performance versus dynamic properties. Results enable easy and quantitative optimization of dynamic properties. Examples of POEM analyses are given.
1971-02-01
Technical Paper
710058
Regis V. Schmitt, Matthew L. Kerr
This paper describes a constant natural frequency spherical elastomeric spring element. The concept of constant natural frequency and its advantage in providing consistent ride quality with varying vehicle weight is reviewed. Performance data on the spherical spring for both laboratory and field tests is presented and evaluated.
1971-02-01
Technical Paper
710080
Howard Dugoff, Leonard Segel, R. D. Ervin
A set of safety-relevant performance qualities for the passenger car has been defined as a first step in the development of objective measures of precrash safety performance. Measures were sought that stress the performance produced by a passenger vehicle when it is operated under emergency crash-avoidance conditions. This goal has led to the identification of six limit maneuvers and associated limit responses to serve as a first-order means of assessing the safety quality of a motor vehicle. The viability and the discriminatory power of the proposed test procedures have been demonstrated by applying these procedures to four separate vehicles.
1971-02-01
Technical Paper
710020
K. R. Trosien, L. M. Patrick
Though the steering wheel has been maligned as a primary cause of injuries in automobile collisions, studies show it is the first passive restraint system in the automobile. Adding an airbag to the steering wheel distributes the energy load better than the wheel alone, and the airbag takes advantage of the space between occupant and steering wheel to protect the driver further. Specifically, the airbag utilizes space to decelerate the occupant, prevents concentrated loads on the torso, stops the face from hitting the steering wheel rim, and helps distribute impact load over a larger area. The airbag has three major components-the sensor, inflator, and airbag. The functioning of these components, as well as experimental investigations conducted to determine operational capabilities of the system, are discussed.
1971-02-01
Technical Paper
710427
Robert D. Gilson
The critical design weight environment necessary to optimize load-carrying efficiency of the C-5A was such that breakthroughs in technology were needed. One such breakthrough was beryllium brakes. From the discovery of beryllium in 1798 its advantages-as well as its disadvantages-were well known. These are discussed to indicate why beryllium was chosen as the brake heat sink material for the design configuration evolved. A review of current C-5A data is presented, including flight test experience, as well as expected life projection from limited normal operational experience. The re-use of beryllium elements, and cost effectiveness are also discussed. A consideration of the future use of beryllium is indicated, with the conclusion that it will become commonplace in the next decade.
1971-02-01
Technical Paper
710505
John F. McNabney
Economics today indicates the need to provide industry with tools of greatly increased capacities to gain the greatest possible output for the least practicable input. Ocean going tankers, railroad cars, airliners, highway trailers, diesel engines, draglines, and shovels are only a few “giantized” tools which are being joined by new earthmoving vehicle concepts of larger-than-life size. A critical item upon which any vehicle in this category depends is its tires. The dimensional scope of the tire program and the challenge of meeting the tire requirements of the various applications being considered are currently being studied by the tire industry. Production facilities of the necessary size and capacity required to meet these needs are now in the process of design and fabrication. This paper discusses the highlights of this giant tire program.
1971-02-01
Technical Paper
710515
Donald J. Zach
A seat suspension has been developed to isolate the operator from high amplitude-low frequency motion characteristics of large, rubber-tired, earthmoving vehicles. The motion of the suspension is unique in that it allows for 7 in. of vertical motion at the operator's “H” point with little or no motion of the lower legs and feet. In addition to greater operator comfort, this arrangement makes possible better control and safer operation.
1971-02-01
Technical Paper
710405
J. David Long, Ronald W. Orme
A method is presented for measuring individual wheel loadings with strain gages mounted on a rotating axle. The mechanics of the system are discussed and the instrumentation required for obtaining the necessary signal outputs is described.
1971-02-01
Technical Paper
710576
C. W. Floyd
Laboratory power loss test procedure and effect of varying conditions on power loss is discussed. An attempt is made to correlate laboratory rolling resistance with fuel economy. The information is presented from the perspective of a tire engineer, with the objective of providing useful information to automotive designers as well as other interested parties.
1971-02-01
Technical Paper
710590
R. H. VanSteenkiste, E. K. Buyze
This paper discusses The Budd Company's development of a new and novel approach to an old product. It involves the design, development, and manufacture of a brake disc for an automotive disc brake using materials other than cast iron. This product must have all the qualities of a cast iron disc, but must be competitive price-wise. The development of a solid disc would have been a relatively simple challenge; however, a ventilated type disc complicated the task by requiring a composite or welded structure. Real ingenuity in design and material processing was demanded. The results are what is called the Budd “All Steel Brake Disc.”
1971-02-01
Technical Paper
710589
Frank H. Highley
Heat storage, heat dissipation, and cooling coefficients are defined; and equations, based on theory and practice, are developed with which values of the coefficients can be determined. Vehicle tests required are described. Use of the coefficients in predicting drum or disc temperatures is demonstrated, using coefficient values obtained in vehicle tests. Use of the cooling coefficient for simulating brake cooling on a brake dynamometer is demonstrated.
1971-02-01
Technical Paper
710527
Rolland D. Scholl, Richard E. Klein
A steering system for an articulated vehicle was analyzed to gain an improved understanding of the closed loop stability characteristics. The analysis was applied to an electrohydraulic system and is applicable to more general types of systems. Since the parameters of electrohydraulic valves are well known, a simulation model including the hydraulic system and the vehicle dynamics, was easily derived. Using the simulation, the oil mass resonance was determined to be the most critical parameter and was controlled by adding compensation in the steering system closed loop. The paper describes the steering system, simulation model, and stability criteria.
1971-02-01
Technical Paper
710529
Thomas E. Cochran
Caterpillar Tractor Co. has introduced a new emergency-parking brake system for its line of large wheel loaders and wheel type tractors. This system includes a multidisk-spring-applied/hydraulically-released-emergency-parking brake, a hydraulic control system providing both automatic and manual application of the brake, and an audiovisual warning system for the operator. The brake is for use on vehicles in the 60,000-140,000 lb range and is designed specifically to provide automatic application of the emergency-parking brake in the event of a loss of service brakes.
1971-02-01
Technical Paper
710530
Lon B. Eberhart
The steering and braking systems used on the all-hydraulic JD-570 articulating grader were designed with the safety of the operator in mind. These systems are given priority over the other related hydraulic systems on the grader through the use of a priority valve. An accumulator is provided to store hydraulic energy for the steering and braking systems in the event of a power failure. In addition, the brake valve is capable of acting as a pump to supply pressure oil to the service brakes, if required. A mechanically actuated secondary brake effective on all four tandem wheels is also provided.
1971-02-01
Technical Paper
710536
Giles A. Kendall
A compressible solid shock isolator is a combination spring and damper which makes use of a silicone elastomer media to achieve these two functions. It is a candidate for use in energy absorbing bumper systems because of its favorable volume, weight, automatic reset capability, functional efficiency, reliability, and cost. E/A bumper systems must be designed to accommodate a wide variety of loading conditions. System qualification requires the use of both pendulum and barrier type testing.
1971-02-01
Technical Paper
710534
Robert G. Moore
Many factors, including vehicle motion, temperature, humidity, atmospheric contamination, and noise level, influence the habitability, or ride comfort, of any vehicle. All of these factors must be considered in the design of an air cushion vehicle (ACV). This paper discusses the motion of the craft induced by traveling over a rough surface. This motion may be reduced by suitable design of the lift and skirt systems, to minimize pressure changes within the cushion.
1971-02-01
Technical Paper
710627
Yasuhiko Fujiwara, Miki Nakayasu
An analysis was made of vibration phenomena in the steering system of a vehicle, when the front wheels have some amount of unbalance. The program included vehicle running tests and bench tests to ascertain some of the factors influencing vibration behavior. A mathematical model of the vibration system was simulated on a digital computer in as much detail as possible. The resultant understanding of the dynamics of the system as a whole led to an extensive theoretical analysis of selected key parameters.
1971-02-01
Technical Paper
710626
N. Seitz, A. W. Hussmann
Of all the automobile safety studies made, one that has received much attention is tire design. Comfort, service life, and reliability have been the guideposts in the development of better and safer tires. The investigation of the forces that affect reliability is the subject of this paper, and emphasis is placed on determination of the parameters at the particular area where tire and road are in contact.
1971-02-01
Technical Paper
710630
Walter Bergman, Harold R. Clemett, Narendra J. Sheth
This paper gives a comprehensive analysis of tire-road traction, utilizing new experimental and analytical techniques. It introduces a concept of traction envelope for evaluation of the overall tire traction properties in all operating modes on a common basis. It establishes feasibility of laboratory techniques for tire wet traction measurements and shows good correlation between road and laboratory measurements and also between road measurements on different surfaces. Comparative evaluation between new and conventional techniques for measuring tire traction on the road in cornering with and without power application are given.
1971-02-01
Technical Paper
710615
O. Webb
Preventing loss of vehicle control under drive conditions is analogous to, and as important as, the retention of vehicle control under emergency braking. Loss of control under drive conditions frequently leads to panic braking, which only aggravates an already dangerous situation. A four-wheel-system for passenger cars is described, having as its special aim greatly improved controllability under all road surface conditions. Reasons are given for splitting the torque unequally between the front and rear axles, and for employing two spin control clutches geared in parallel to the center differential in such a manner as to modify the basic torque split.
1971-02-01
Technical Paper
710165
George M. Kurajian, Harold Burr
A general analog computer procedure is presented for the dynamic analysis of a selected realistic model of an automobile or truck vehicle wheel-frame system. The elements of the model are assigned a set of values based on a preselected vehicle, and the model is then subjected to a number of inputs which correspond to test track road disturbances at various speeds. This procedure is successively applied to a number of typical vehicles. Time-varying values of wheel spindle and frame reaction “g” loads, acclerations, and displacements are recorded, and illustrative waveshapes are depicted. Tables indicating extreme values of these quantities are also included.
1971-02-01
Technical Paper
710388
T. Peter Neal
Control-system bobweights and downsprings are quite often used in general aviation airplanes to improve longitudinal static stability at aft c.g. positions. However, these devices can also have strong and usually undesirable effects on the airplane's dynamic behavior. These important effects are reviewed and discussed. In addition, guidance is provided as to how some of the undesirable characteristics can be minimized by careful design.
1971-02-01
Technical Paper
710400
Don McCosh
Aircraft produced by Cessna have, for a number of years, used steel landing gear springs as the major portion of the aircraft main or tail landing gears. These steel springs are relatively simple in design and manufacture, and have proved to be durable. This paper discusses some of the factors involved in the design of a spring steel landing gear, analysis methods, and design goals used at Cessna. Certification requirements and methods of compliance for landing gears are also discussed. The analysis methods employed have been proved acceptable by the ability of the gears to pass certification tests without modification, and by service experience.
1971-02-01
Technical Paper
710360
B. L. Douglass
With the advent of increasing numbers of heavier passenger car-trailer combinations, the need for a uniform brake test procedure code and recommended level of performance requirements for such combination of vehicles became apparent. Initial efforts were directed toward a standard of performance for the trailer or towed vehicle brakes only, but as the work progressed a more practical solution evolved in a test code, SAE J134, and performance requirements, SAE J135, for passenger car-trailer combinations. It is intended that light trucks will be considered in a later revision.
1971-02-01
Technical Paper
710361
Raymond R. McHenry
A digital computer simulation of complex, three-dimensional dynamics of automobiles on irregular terrain is described which is suitable for studies related to vehicle braking systems and to the driving task, including the upper limits of control as well as the linear ranges of operation. The reported simulation is an extended version of an earlier, validated mathematical model. A number of refinements and extensions of the analytical treatments of tire forces, suspension properties, and terrain definitions, have been incorporated. Also, analytical representations of the braking system and driveline, and approximations of rolling resistance and aerodynamic drag, have been introduced. Sample outputs of the modified computer program are presented and discussed.
1971-02-01
Technical Paper
710287
J. Mahig
Knowledge of that component of a vehicle's handling characteristics represented by the vehicle dynamics is necessary to analyze the driver's role in controlling the vehicle. One aspect of this problem is determination of the effect on the stability under differing road conditions in the linear as well as nonlinear region. The simulation presented evaluates the response the vehicle suspension system to suddenly applied external impulses which are identified as caused by wind gust and road disturbance. This analysis considers only the effect on the lateral stability of the vehicle. Thus this representation is assumed completely decoupled from the longitudinal dynamics of the vehicle. Proceeding in this fashion makes it possible to study the effect of large wind gust and lateral road impacts on the lateral stability of a vehicle containing nonlinear tire characteristics. The effects in the nonlinear region are clearly demonstrated with the aid of a conventional root locus plot.
1971-02-01
Technical Paper
710252
P. W. Meyer
The paper attempts to give an overall view of the very complex brake fluid situation existing in Europe today. It is written with the hope of creating a better understanding of the actual realistic requirements that have to be set for modem and safe brake fluids. It is further hoped that it may help to pave the way for an international standardization of brake fluid specifications and test methods.
1971-02-01
Technical Paper
710253
R. W. Radlinski, R. J. Forthofer, J. L. Harvey
Automotive hydraulic brake fluids are known to pick up water in service. This paper shows that a major portion of the water picked up by the brake fluid in a braking system is transmitted through the hoses. It discusses two major effects of water pick-up on brake fluid performance-reduction in vapor lock temperature, and increase in low temperature viscosity. Performance data for several “wet” brake fluids operating in actual braking systems at high and low temperatures are presented.
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