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A new and different seat suspension suitable and advantageous for off-the-road and highway vehicles is presented. Contributing to a comfortable ride for the operator are several proved features, to which have been added three new and unique features. The seat suspension is an air-oil cushioning system to which has been added a servo-linkage to operate a two port hydraulic valve; the servo-linkage being tied to the vertical seat motion. The new, unique features are: 1. Unlimited range of adjustment of seat vertical position to suit the individual operator, assuring him of easy access to the brake pedal, good vision, and comfort, regardles of his particular body dimensions. 2. At any vertical seat position the operator chooses, automatic adjustment for the weight of the operator. 3. Clearance between the front edge of the cushion and the rim of the steering wheel, once set to the operator's liking, is maintained, including the time while the operator is dismounting and remounting.

A different approach to the study of drivetrain cost comparisons is presented, using 175 units operating within two fleets. Engine, transmission, clutch, driveshaft, universal joint, etc., were identical, item for item; the exceptions being identical brake types but different manufacture and differences in the manufacture of chassis. All units were serviced by the same mechanics. Use of a data bank by the mechanics gave a true cost/mile for the two fleets compared, and showed that good record keeping would provide fleet managers continued benefits.

Improved power brake booster designs and systems with redundant capabilities are anticipated to be required as a result of the new safety regulations for improved stopping distances, and indirectly, as the result of the new emission controls because of the potential loss of vacuum availability and increased underhood temperatures. In early 1968 it was becoming obvious to certain brake engineering groups that a new brake booster system with reserve capabilities for truck hydraulic brakes would be a requirement in the near future. Bendix, as a major independent supplier of power brake boosters, had more than a casual interest in this trend appearing over the horizon. As the result of discussions with customers and our internal analysis of various power booster systems, hydraulics, in the form of the Bendix Hydro-Boost system with an integral electric motor pump backup, was settled upon as one major approach to best serve the industry.

An initial report presenting order of magnitude data only. Owning, operating, and maintaining fleets of line-haul and pickup and delivery units has its own peculiar problems. This paper considers questions such as what manufacture of vehicle should be selected, reliability of the product, whether or not to perform maintenance, etc. Specifically covered is the possible problem area of drivetrains; a preliminary standard operating system developed by the American Trucking Assn., Inc. is given.

This paper discusses the history, theory, operation, and refinements of one of the oldest limited-slip vehicle axle and tandem interaxle differentials that has remained in continuous production. The design uses a cam and wedge principle, but is a true differential in the manner of a conventional geared unit. Its unique drive principle provides frictional bias in a ratio between 2-3:1 to increase vehicle drawbar pull on split-coefficient surfaces.

The approach taken in the design, development, and application of an Oshkosh powershift transmission for on/off-highway truck use is described. The Oshkosh transmission design has a building block concept, and in its basic form consists of a two-speed splitter auxiliary attached to the four-speed main drop box to provide a transmission with eight forward speeds and two reverse speeds. The two-speed splitter auxiliary may be omitted to provide a transmission with four forward speeds and a single reverse speed. The eight-speed transmission will be capable of use with high speed, low torque engines, or with low speed, high torque engines. This is accomplished by changing the input ratio gears. The overall ratio of the transmissions may also be changed to match tire size and/or axle ratios. The ratio changes for engine speed-torque and/or overall ratio may be made without affecting the transmission range or physical configurations.

The operation and application of the NoSPIN and Tandem-Lock differentials to power transmissions is described. The three types of NoSPIN-standard, silent, and silent-overrunning-and two of Tandem-Lock-conventional NoSPIN and inside-out design-are described, and the positive and negative features of each are considered. The paper points out the early design deficiencies and the corrective action taken to overcome them. The application guidelines of the NoSPIN and Tandem-Lock differentials are also covered so that proper application of the differentials can be carried out.

This paper describes a shiftable controlled traction differential developed for both on and off highway heavy-duty truck application. The differential can provide greater limited slip action when engaged for adverse driving conditions than current designs and yet not have the undesirable aspects normally associated with limited slip differentials. There is also a unique lubrication system that extends the life of the unit.

The types of noise problems confronting the urban dweller and the legislation dealing with such noises are discussed in this paper. Of prime consideration are vehicular transportation, mass transportation, and railroad noise. Current noise regulations in Chicago are reviewed and the needs of future legislation explored.

Various methods have been used to restrict differential action in drive axles to prevent loss of traction. Although these methods differ in principle, they exhibit similar characteristics. Based on tractive effort performance, most devices can be categorized into one of four basic classifications. This paper defines these classes and compares them to requirements needed for the “ideal” differential.

A program was undertaken to determine which retrofit methods are currently feasible for used cars, considering emission reduction effectiveness, cost, effects on vehicle performance, facilities, and labor skill required for retrofit installation, maintenance, and inspection. An extensive search was made for all sources of information on retrofit methods, developers, and producers. Eleven representative retrofit devices were actually tested in this project. A fleet of 20 used vehicles without factory installed exhaust control systems was used for testing the performance of the retrofit devices. The vehicles were tested first without a retrofit device to obtain a reference baseline, and then with retrofit device installed. Emission tests were conducted by the 1972 CVS Federal Test Procedure. Fuel consumption was also measured during the CVS test. Drivability tests were conducted by an Automobile Manufacturers Association procedure.

Data were obtained on exhaust emissions at idle from four fleets of cars to develop information that would be needed for servicing vehicles rejected by state and city emission surveillance programs. As expected, emissions increased with car age. Pre-1968 European cars produced higher emissions and responded less favorably to tune-up than other pre-1968 cars. Idle emission standards already proposed can bring about rejection rates ranging from 10 to 60% of all cars depending on the emission standard and local car population. Extended idling can increase these rejection rates by 3 to 31% of all cars. Although most rejected cars passed emission standards after tune-up, a significant percentage required additional repair work in order to pass. It is clear that with several standards, some cars could not be made to pass at a reasonable cost. Evaluation of exhaust analyzers has led to development of criteria for service station equipment.

This report presents some design parameters and development experience on quick-heat intake manifolds for evaporating the fuel. These can achieve good fuel evaporation soon after a cold start. Used in conjunction with a fast-opening choke, such a quick-heat intake manifold helps reduce carbon monoxide (CO) emissions. This is especially effective on cars with catalytic converters, since CO caused by cold enrichment is produced at a time when the catalyst is not yet hot and effective. The sensitivity of one design of quick-heat intake manifold to fuel volatility characteristics is included. A variety of ways to correlate drivability with the ASTM distillation characteristics of the fuel are evaluated.

Quick-release chokes may become an essential feature of advanced exhaust emission control systems to minimize emissions during warmup. However, quick-release chokes greatly impair warmup driveability when gasolines of conventional volatility are used. Consequently, modifications of gasoline volatility were investigated as one approach to restoring warmup driveability with quick-release chokes. Warmup driveability of two test cars equipped with quick-release chokes was measured on a chassis dynamometer at 40 and 68 F using fuels with widely different volatility characteristics. Warmup driveability was essentially restored by increasing fuel volatility in the 40-90% ASTM distillation range. Front-end volatility up to the 40% point had very little effect.

Drivability tests were conducted on 12 cars at four ambient temperatures with seven fuels of differing front-end and mid-boiling range volatility levels. One fuel was a typical winter grade gasoline, one was typical of summer grade, and the remaining five were blended to provide various combinations of Rvp and ASTM 50% evaporation temperature. Three driving schedules were used on the chassis dynamometer-a cold-start driveaway schedule to study operation from cold start through warmup, a warm-vehicle procedure to evaluate drivability with a thoroughly warmed-up car, and a hot-start vapor lock procedure to observe hot-fuel handling characteristics. Road tests were run at one temperature on four cars with two fuels for correlation between road and dynamometer results.

For many years, the primary consideration for determining motor gasoline volatility specifications has been good car performance, i.e., fast start-ups, freedom from vapor lock, and good driveability. Now, for late-model cars, there is a new consideration for volatility control. This is exhaust emissions. Fuel volatility has been found to have a significant effect on the exhaust emissions of many late-model vehicles. A decrease of 5 psi RVP from current levels increased exhaust CO an average of 28% at 70°F and 22% at 30°F in a group of eleven cars. Exhaust hydrocarbons were increased an average of about 5% at both temperatures. Now, before lowering fuel volatility, it is important to consider the effect the change will have on exhaust emissions as well as car performance.

Automotive friction materials are composites containing three kinds of components: an organic binder, fiber for reinforcement, and property modifiers. At low braking temperatures, the wear rate of the friction materials is controlled primarily by abrasive and adhesive mechanisms. At higher braking temperatures, the wear rate increases exponentially with increasing temperature due to thermal degradation of the binder and other components, and the exponential wear rate is frequently accompanied by brake fade. Thus, one method of reducing thermal wear and fade tendency is to lower the temperature at the rotor/friction material interface. Since the rate of heat transfer from the interface is mostly dependent upon the conductive and convective modes, a rotor of high thermal conductivity will have a significant advantage over a rotor of low conductivity, if the heat capacity remains the same.

This paper presents the findings of the second year of a planned three-year program to investigate the hydrocarbon losses sustained during the refueling of passenger cars. The magnitude and frequency of occurrence of spills by type of spill were estimated from observations of refueling operations during a five-city, four-season field survey. The magnitude of the average observed loss due to spills was 10.6 g and the probability of a spill loss was 0.329. The average spill loss was 3.5 g per refueling operation or 0.3 g/gal of dispensed gasoline. Measurements of displaced hydrocarbon losses were made under controlled conditions during a laboratory study conducted in the Scott all-weather room. A regression analysis of these data yielded a model which estimates the displaced hydrocarbon loss as a function of dispensed fuel temperature, displaced vapor temperature, and the Reid vapor pressure of the fuel.

The A-weighted sound level accounts for the bulk (but not all) of the jury's reaction to the sound of trucks coasting on a variety of tires. A component of the jury's reaction is related by the study to the manner in which the sound decays after the vehicle passes the point of observation. This component also appears to depend strongly on the characteristics of the sound. The jury's reaction shows two forms of distortion: end-of-scale compression and temporal drift. The analysis attempts to account for these factors and to see beyond them into the jury's basis for reacting.

The SAE Truck Tire Noise Subcommittee, as a part of its efforts toward writing a measurement and evaluation procedure, conducted an experimental test program for relating objective and subjective assessments of truck tire noise. The program comprised a series of designed experiments involving 6 trucks, 18 sets of tires, and 5 vehicle operating modes. The test runs were presented in random fashion to a jury situated alongside a highway. The subjective noisiness ratings and the A-weighted sound levels obtained verified the design objectives of the experiment and, further, correlated well with each other.