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Technical Paper

Why Disc Brakes

A family of disc brake systems, capable of braking vehicles with gvw's from 3000-6000 lb, has been developed and released on the 1965 Lincoln and Thunderbird with power brakes as standard equipment, and on the 1965 Mustang with manual brake as an option. These systems, while retaining the desirable characteristics of current drum brake systems, provide significant performance advantages in the areas of fade resistance, stability, and serviceability. The disc brake systems on the Ford products consist of a ventilated rotor, in conjunction with a fixed, multiple-piston caliper utilizing segmental brake linings. Duo-servo rear brakes are used with a hydraulic proportioning valve which compensates for the nonlinear rear brake output.
Technical Paper

Why Do Airplanes Make Noise?

THIS paper presents a brief historical review of the quest for information concerning the mechanism of aircraft noise generation. It is shown that, after a number of false hypotheses, the noise of propellers was finally traced to the principal aerodynamic loads of the blades. The intensity and characteristics of the noise can now be predicted theoretically from knowledge of the geometry and operating conditions of the propeller. With regard to jet noise, the picture is not so clear. The actual mechanism of noise generation is still somewhat obscure. Included here is a resume of United States and British work on determining the actual source of noise. Experiments on devices for reducing noise are also discussed.
Technical Paper

Why Do We Need the Diesel?

Audi and Volkswagen support the diesel, because there are four good reasons for using a modern diesel engine: It is efficient, economical, environmentally friendly, and future-oriented. The advantages in fuel consumption and exhaust emissions offered by the diesel and above all by the direct-injection diesel are presented and discussed here in view of their implications for future development. In addition the benefits of better fuel qualities is discussed.
Technical Paper

Why Does a Car “Pivot”?

REMARKING the difficulty of explaining logically the strange phenomenon known as the “pivoting” of a car, the author, after presenting citations of actual experiences with various combinations of front-wheel and rear-wheel braking and their tendencies to cause a car to pivot, analyzes pivoting and explains its causes under (a) “dry-roadway” and (b) “skiddy-roadway” conditions. Concerning (a), the author states that when two-thirds of the braking force of a four-wheel-brake system is distributed to the rear wheels, the preponderance of the stopping or braking force will remain active to the rear of the center of gravity of the car, causing a so-called “drag-anchor” effect to counterbalance what is termed the “spin effect,” and no dry-roadway pivot can occur. Since the friction available between the roadway and the tires is comparatively small on a skiddy roadway, the retarding forces at the two sets of wheels should be utilized to their utmost.
Technical Paper

Why Dual Tires Do Not Stay Matched

TIRE matching is not a simple matter, says Mr. Place, for a good program of matching on one operation may not give as good results, relatively, on another. For this reason, he asserts that it is impossible to make one blanket recommendation that will give the best overall results on all fleet operations. Thus, he confines himself to describing what takes place during the use of dual tires, and discusses certain service expedients that operators may try under close observation.
Technical Paper

Why Engine Variables Affect Exhaust Hydrocarbon Emission

The relative importance of several internal environmental factors known to affect the hydrocarbons exhausted by an engine has been studied using an analytical model of the emission process. The model included A: two sources of unburned fuel resulting from wall quenching of the flame, 1) the walls of the open part of the chamber, and 2) the crevices separated from the open part of the chamber by restrictive passages; and B: three subsequent effects, 1) the oxidation of unburned fuel in the chamber after flame propagation, 2) the preferential exhausting of the burned products from the chamber and 3) the oxidation of unburned fuel in the exhaust system. Results obtained by empirically fitting the model to measured exhaust hydrocarbon concentrations for systematic changes in five operating variables indicated that different environmental factors predominated in causing the different variable effects.
Technical Paper

Why Four-Wheel Drive?

This paper covers the development and marketing experience, from an engineering point of view, of four-wheel-drive agricultural tractors up to the present time. The information pertains to the Minneapolis-Moline-type of four-wheel-drive and discloses new information on application data. Specific information is given on how to optimize a four-wheel-drive for agricultural applications; design duty cycle and how this duty cycle was confirmed by experimental and field testing. Trends in the use of agricultural tractors as affected by the four-wheel-drive introduction are also given.
Technical Paper

Why Front-Wheel Drive?

Front wheel drive has found wide acceptance and increased popularity during recent years in medium and medium-small class European cars. A frequent design configuration is the FWD with transverse front engine. The principal factors in this choice are: 1. Better use of available space 2. Production costs at levels competitive with other design arrangements 3. Ease of obtaining derivative models from basic cars. The technical/functional aspects of the FWD will not be discussed here except some reference needed to explain otherwise uncomprehensible concepts.
Technical Paper

Why Gasoline 90% Distillation Temperature Affects Emissions with Port Fuel Injection and Premixed Charge

Statistically designed experiments were run in a single-cylinder engine to understand the reason for the decrease in exhaust mass HC emissions found in the Auto/Oil Program with decreasing 90% distillation temperature (T90) of gasoline. Besides T90, the effects of mixture preparation, equivalence ratio, and ambient temperature on emissions and fuel consumption were measured. HC emissions were higher with PFI than with premixed charge, but decreasing T90 decreased HC emissions with both premixed charge and PFI. Rich mixture and low ambient temperature increased HC emissions. Speciated exhaust HC measurements indicate that incomplete vaporization of heavy components of the gasoline (C8-C10 alkanes, C6-C9 aromatics and alkenes) was responsible for higher HC emissions.
Technical Paper

Why Has the Medium-Speed Diesel Become Competitive in Marine Propulsion?

Since 1965, the market for propulsion plants for large merchant vessels has shown an increasing trend towards medium-speed geared plants. An economic analysis determines the reasons why the medium-speed engine can compete with the slow-running, direct-propulsion, two-stroke engine. The various influences on the types of cost are examined and the cost parameter range within which the medium-speed geared plant is competitive will be marked out. An optimization analysis clarifies the cost advantages that will be provided by tomorrow's still larger medium-speed four-stroke diesels.
Technical Paper

Why Have a Systems Engineering (SE) Capability for Automotive Product Development? - Questions and Answers

A clear understanding of Customer and User requirements is essential to successfully develop, design, build, test and produce components and systems for Customer Programs. Systems Engineering (SE) is defined as “a formal process for the development of a complex system, driven by a set of established requirements, derived from the intended mission of the system throughout its life cycle”. Systems Engineering has been successfully employed for decades in aerospace and commercial product development, but its methodology may not be used or is underutilized by many automotive companies and their suppliers. This paper will describe the characteristics and aspects of a “System” and the corresponding Systems Engineering methodology from educational, professional and corporate perspectives.
Technical Paper

Why High Density Polyethylene for Automotive Applications?

The question, “Why high density polyethylene for auto motive applications” will be answered by reviewing the resin’s physical properties, the advance in processing techniques, and the use of these techniques to fabricate parts for the automotive industry. In addition, the properties of particular groups of resin will be presented to illustrate the importance of selecting the proper resin for each application.
Technical Paper

Why Hydraulic Shovels - Mining

The hydraulic shovel as a primary loading tool in mines and quarries is compared to more conventional methods used to date in the North American market such as cable shovels and large wheel loaders. Discussed are the history of the hydraulic shovels, their concept, and their place in the mining industry. Also discussed are the applications for which hydraulic shovels are best suited, not only because of their performance but also because of other advantages such as mobility, production and economic considerations. A comparison is made to other alternatives of loading methods considering the many factors today's user is faced with.
Technical Paper

Why Hydrostatic Track Drive-The Liebherr Line of Crawler Tractors and Loaders

Crawler tractors and loaders with hydrostatic drive systems and other related state-of-the-art features are compared to machines with conventional drive systems. Discussed are the advantages, due to a different design, concerning production capabilities, maintenance, preventive maintenance, and repair and operator acceptance. In today's market, increased employee turn-over makes shorter training times to reach a certain level of efficiency more and more important. For the same reason, equipment owners look for machines which are easier to maintain and need shorter repair downtimes for high availability. Parts interchangeability between different machine lines and sizes, and the size and weight of individual components become serious considerations. Also discussed are the higher internal efficiency and better utilization of installed engine horsepower.
Technical Paper

Why Intake Charge Dilution Decreases Nitric Oxide Emission from Spark Ignition Engines

This study was undertaken to develop a better understanding of how intake charge dilution by various gases affected nitric oxide (NO) emission from a single-cylinder spark ignition engine. Carbon dioxide, nitrogen, helium, argon, steam, and exhaust gas were individually added to the intake charge of a propane-fueled, single-cylinder engine operated at constant speed and load. Nitric oxide emission was reduced in all cases. The gases with higher specific heats gave larger NO reductions. The product of diluent flow rate and specific heat correlated with NO reduction. The effects of diluents on calculated combustion temperature, mbt spark timing, and fuel consumption are also presented and discussed.
Technical Paper

Why Liquid Phase LPG Port Injection has Superior Power and Efficiency to Gas Phase Port Injection

This paper reports comparative results for liquid phase versus gaseous phase port injection in a single cylinder engine. It follows previous research in a multi-cylinder engine where liquid phase was found to have advantages over gas phase at most operating conditions. Significant variations in cylinder to cylinder mixture distribution were found for both phases and leading to uncertainty in the findings. The uncertainty was avoided in this paper as in the engine used, a high speed Waukesha ASTM CFR, identical manifold conditions could be assured and MBT spark found for each fuel supply system over a wide range of mixtures. These were extended to lean burn conditions where gaseous fuelling in the multi-cylinder engine had been reported to be at least an equal performer to liquid phase. The experimental data confirm the power and efficiency advantages of liquid phase injection over gas phase injection and carburetion in multi-cylinder engine tests.
Technical Paper

Why Manned EVA?

Despite the fact that early STS planning did not include any provisions for manned Extravehicular Activity (EVA), the orbiter airlock and Extravehicular Mobility Units (EMU's) or “spacesuits” were eventually incorporated in the Space Transportation System. Events have amply demonstrated the value of manned EVA. It is concluded that EVA will continue to be required for STS missions and for the Space Station. The reasons that space vehicles may need servicing are presented, e.g., reliability/-MTBF, preventive maintenance, wear-out and degradation, damage, updating, and replacement. The functions that man can perform EVA are then reviewed, e.g., inspect/assess, reconfigure, repair, replace components, debris capture, checkout and verify. Some of the functions that man can perform easily in EVA but are difficult for machines/teleoperators are reviewed.