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Multiple field trials and nearly a decade of laboratory studies have demonstrated that shear stable multigrade hydraulic fluids improve fuel economy. These studies have determined that fuel efficiency is dependent upon temperature, fluid viscosity and shear stability. This paper presents a viscosity classification system proposed by the National Fluid Power Association (NFPA) Fluids Technical Committee. This system is analogous to the SAE J300 viscosity classification system for engine oils. The letter “L” is used in place of “W” as the designation for the low temperature grade. Under this new classification system, NFPA 32L-68 fluids will provide the low temperature viscosity properties of an ISO VG 32 hydraulic fluid and the high temperature viscosity properties of an ISO VG 68. In addition, fluids that meet the requirements of the proposed NFPA Energy Efficient classification system increase fuel economy and productivity while reducing CO2 emissions.

Should the United States government become involved in regulating quality standards systems which provide guidelines for quality management and quality assurance of products and services? This paper examines recent developments within quality standards systems, in particular ISO 9000 and QS-9000, and their effects on small businesses, automobile and other industries, and international trade. The difference between these standards is one is representative of international consensus on the essential features of a quality system while the other is focused on applying these international rules to specific sectors of industry. Analysis is conducted on whether government involvement is necessary and, if so, the ways in which government could assist in standards development, regulation, and/or enforcement.

To make electrical or electro-hydraulic gas exchange valve actuators more economically feasible for the production of cam-less engines, it is desirable to achieve valve position information from existing engine sensors rather than to develop and install new sensors for each gas exchange valve. Time and frequency domain characteristics of acoustic (knock) sensor signals were analyzed using both cross-correlation and Fourier analyses to determine characteristics that indicate valve position. The time-domain signatures for valve events were found to be inconsistent from cycle to cycle and thus difficult to identify using cross-correlation techniques. Frequency content of the engine vibration as it varied with crankshaft angle was analyzed to find valve position dependent patterns. Analysis revealed a wideband signal that correlates to intake and exhaust valve closing events.

A four valve controller and electronic control circuits were developed to control the displacement of hydrostatic pump/motors (P/M's) utilized in an automobile with a hydrostatic transmission and hydropneumatic accumulator energy storage. Performance of the control system was evaluated. The controller uses four high-speed, two-way, single-stage poppet valves, functioning in the same manner as a 4-way, 3-position spool valve. Two such systems were used to control the displacement of two P/Ms, each system driving a front wheel of the vehicle. The valves were controlled electronically by a distributed-control dead-band circuit and valve driver boards. Testing showed that the control system's time response satisified driving demand needs, but that the control system's error was slightly larger than desired. This may lead to complications in some of the vehicle's operating modes.

This paper examines the compatibility and filterability characteristics of mineral oil and bio-based hydraulic fluids. Due to advantages in renewability and environmental acceptability, bio-sourced, biodegradable hydraulic fluids are increasingly used in fluid power applications. Conversion from mineral oil based fluids to biodegradable fluids can be expensive because hydraulic systems often must be drained and flushed several times during the conversion process. The goal of this research is to investigate the use of the ISO 13357:1 wet filterability procedure as a method for determining the compatibility of hydraulic fluids. Mineral oil, vegetable oil and synthetic ester based hydraulic fluids mixtures have been evaluated. An additive combination that is known to have marginal compatibility has been evaluated under conditions of varying temperature, duration, and concentration.

This paper presents an investigation of the fluid viscosity properties that affect the Low-Speed High-Torque (LSHT) efficiency of hydraulic motors. Low speed torque efficiency is important because it often determines the minimum displacement (size) and operating pressure of mobile hydraulic equipment. The viscosity, viscosity index, high-shear viscosity, piezoviscosity and shear stability of prototype fluids have been characterized. These hydraulic fluids have been evaluated in a full-scale hydraulic motor dynamometer. Geroler, axial piston and radial piston motors have been evaluated. Low-speed (1 RPM) testing has been performed under constant pressure conditions in accordance with the ISO 4392-1 standard test method. Startability testing has been performed under constant load conditions in accordance with ISO 4392-2. In startability and 1 RPM testing, the axial piston motor exhibited a 6 percent efficiency gain with a high viscosity index hydraulic fluid.

A computer model is developed for a system consisting of an electronic chopper circuit driving a magnetic actuator, which in turn operates a hydraulic valve that controls a hydraulic cylinder. Here the entire system is modeled using SPICE, a widely used electric circuit simulation program. Besides the SPICE model of the chopper circuit, included are a model of the magnetic actuator obtained by electromagnetic finite element analysis and a model of the hydraulic valve and cylinder based on their hydraulic and mechanical equations. The complete model is used to compute typical system performance.

A 4-wheel drive off-road vehicle was designed and fabricated using extensive hydraulic technology for the SAE (Society of Automotive Engineers) Mini-Baja competition. The vehicle incorporates an open hydrostatic transmission using a single pump and four independent drive motors. A constant power controller that maintains full engine power to drive the vehicle or stores excess energy in two accumulators controls the pump. Each of the drive motors is independently controlled using a proportional meter-out pressure control valve. The use of pressure control allows the flow to each of the motors to be proportioned based on the dynamics of the vehicle. A CAN bus controller is used in conjunction with a steering sensor to provide differential motor speed control in maneuvering conditions that insures 4-wheel drive availability at all times. Steering of the vehicle is achieved by articulating the chassis using a rotary actuator and multi-motion actuator controlled by the driver.

This paper presents an experimental study of external gear pump efficiency based upon an analysis of the Stribeck values. The volumetric, mechanical, and overall efficiencies of a variety of external gear pumps were measured under steady state conditions. Straight grade antiwear hydraulic fluids were evaluated at 50°C and 80°C. Stribeck values for mechanical, volumetric, and overall efficiency were compared to classic pump efficiency curves. The experimental curves for pump volumetric and overall efficiency were consistent with the classic pump efficiency model. Mechanical efficiency diverged from model behavior at low Stribeck numbers; declining at low speeds and high pressures as contact conditions transitioned from the hydrodynamic to the mixed-film lubrication regime. Lubrication of external gear pumps can be enhanced by using hydraulic fluids that optimize the Stribeck value. A simple expression for relating the Stribeck number to volumetric and mechanical efficiency is presented.

In determining the specific fuel consumption rating of gasoline-driven single-cylinder engines, three problems occur: test stand vibrations, shifting of the direct coupling mechanism, and inability to maintain constant dynamometer loads for any length of time. A small portable test stand was designed, minimizing the vibrations. A steelflex coupling fastened by means of two set screws, one on top of another, absorbed the shock loads and prevented coupling shifting. A water pressure valve installed at the inlet to the dynamometer maintained a constant water pressure. A deflector mounted within the dynamometer in turn insured the rotor being completely surrounded by water, allowing a constant load to be maintained on the dynamometer.

The history of the Stirling engine is briefly reviewed, together with the theory of the engine, and the Stirling cycle. The Stirling and Carnot cycles are compared. The Stirling engine and its operation are discussed, and several recommendations are made, among which: the output work would be increased by increasing the temperature change of the working fluid, and improvement could be accomplished by better seals in the system.

SAE Student Branches actively participate in a multitude of projects designed to compliment and enhance their formal engineering education. While the typical engineering curriculum gives students the basic skills necessary to meet the technical objectives of the project, the basic elements of project management are often overlooked. This paper describes the basic element of project management, and discusses specific applications to SAE Student Branches.

An accurate nonlinear model of a typical magnetic actuator is included in a new SPICE simulation of an electrohydraulic system. The actuator model is obtained by electromagnetic finite element analysis. The resulting nonlinear magnetic flux linkages and forces as functions of airgaps and currents are included in the SPICE model. The SPICE model is able to include electronic driver circuits and models of the hydraulic circuits, which are shown to interact to determine the closing time of electrohydraulic valves.