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Hydrostatic drives offer many advantages in certain vehicle applications. In zero-turn-radius vehicles, advantages such as infinitely variable transmission, high torque transfer, transmission responsiveness, and non-clutching direction reversing make this system the transmission of choice. Currently, most hydrostatic transmissions use mechanical linkages to set the displacement of the hydrostatic pumps. The use of non-linear linkage connections and mechanical damping are used to give the required vehicle drive feel. The use of electrical actuators on hydrostatic pumps along with minimal use of sensors allows the design engineer to replace the conventional mechanical linkages on hydrostatic drive vehicles. In some instances the cost savings gained with the removal of the linkages offset the cost of the electronic circuitry, actuators and sensors.

Three currently available hydromechanical transmissions have been considered, all targeted at the off-highway market. For the purposes of this paper, these are designated Types “A”, “B” and “C”. Each unit has discreet qualities and types of application, and further differences will be highlighted. To provide a reference, a conventional six speed power-shift transmission has also been included, with a down-stream range change unit, held in “Hi” range; designated type “X”. The problem Ricardo have addressed in this paper is how to compare and contrast the qualities of these units for a potential user, who may not be familiar with off-high-way applications. The example considered in this study is a mobile rough-terrain crane manufacturer, contemplating a 25 tonne machine with a 193 kW engine and an on-highway max. speed of 75 kph.

As electronic systems for off-highway applications become increasingly complex, original equipment manufacturers (OEMs) must rely on outside suppliers to design the electronics and application software for these systems. Often, a combined development team is formed, with engineers from both the OEM and the supplier working together to design the system. While many methods for software process improvement exist, few of these methods deal directly with the unique challenges of coordinating and implementing software improvements for a geographically- and politically-split development team. The objective of this paper is to outline methods that may be used to create and develop a software process for such a split development team.

The use of hydrostatic transmission as vehicle drives is primarily motivated by its large range of continuously variable speed, high maneuverability and a possibility to increase the overall efficiency. Consequently an optimally designed system can provide low fuel consumption and thereby low exhaust gas emission. Modern technology involving electro-hydraulic systems, microprocessor control and control theory makes it easier to utilize the advantage of these properties than using traditional hydro-mechanical control. The requirements on productivity are very high for mobile machinery. High output capacity and a wide velocity range are therefore of great importance. To meet these requirements an ordinary hydrostatic transmission is generally used with a mechanical gearbox connected in series. The main drawback in this concept is the high cost in using a gearbox, which can switch gear ratios without jerks and other disturbances in speed and torque transmission.

During the last few years, industry has come to face the demand of optimizing the ecological compatibility of its technical products. Especially the agricultural machinery branch is to develop ecologically compatible machines and facilities as these are used for work in ecologically sensitive areas. This paper will present the practical experiences of optimizing agricultural machines' ecological compatibility; it will also show a method designed for ecologically oriented agricultural machines' development in small and medium sized enterprises, based on these experiences.

Designers of mobile and off-highway equipment are developing more efficient systems to meet the demands of increased competition. Improving designs often includes a review of the hydraulic system, as engineers seek more efficient means of transmitting power. Increasingly, the focus is on reducing the size of hydraulic components or concentrating power in smaller package sizes. This can be accomplished by using higher operating pressures. To meet this challenge, developers of new off-highway hydraulic components must be able to test under those more demanding high pressure conditions. Fortunately, there are now more test-stand components available to support these manufacturers, as they design and qualify their products for higher operating pressures. Component testing is currently being conducted at pressures as high as 15 000 psi (1040 bar).

Efficiency increase of an agricultural tractor may be achieved through installation of a pneumatic track propulsion system to combine the benefits of both pneumatic wheels and rubber tracks. A pneumatic track comprises a power belt and a number of pneumatic elements attached thereto. Serviceability of the pneumatic track is dependent upon the properties of its pneumatic elements. The article gives the methodology and static test results of several types and dimensions of pneumatic elements. The tests were run on a custom-designed testing stand. Geometric parameters, properties of static rigidity rate (normal, lateral, and tangential), and pressure distribution coefficient versus air pressure in the pneumatic elements have been determined. Through mathematical processing of experimental data regressional equations have been obtained. The methodology and the results of the experimental studies are given for a tractor having a pneumatic track propeller.

The operator of a sugarcane harvester cannot see the basecutter and depends on sound to adjust its height. A mechanical/hydraulic system was developed to follow the vertical changes in row height and the lateral changes in the location of sugarcane stalks on the top of the row. The system sensor was an articulated skid mounted in front of the cutter blade. Laboratory and field tests showed the system was able to keep the blade adjusted within 2.54 cm of the top of the row when tested under simulated field conditions.1

Electrorheological and magnetorheological fluids have found commercial application in a wide range of damping, force transmission and fluid flow arrangements, but are complex fluids, needing accurate rheological models for application design. In order to further the understanding of the behavior of these fluids under stress, a new lumped parameter (eight-element) model of shear-mode electrorheological fluid dampers has been developed. In this paper, the new model is presented and experimental data on damper force response is compared with model predictions over a range of sinusoidal input displacement amplitudes, input excitation frequencies and electric fields.

“Bio Fluids” have the remarkable property of rapidly degrading in natural environments. Unfortunately, the same fluid chemistry leading to biodegradation also leads to fluid instability in machine environments. This dilemma can be resolved through vigilant contamination control. Maintaining biodegradable fluids at extremely low levels of particulate contamination and extremely low levels of moisture discourages fluid deterioration, especially the breakdown mechanisms of oxidation and hydrolysis. Maintaining fluids clean and dry also achieves the additional benefits of limiting the wear and corrosion of mechanical components. The challenge is to control these contaminants in the fluid systems of heavy machinery operating in wet and dusty environments.

Despite the best preventative measures, ruptured hoses, spills and leaks do occur with the use of all hydraulic equipment. Although these releases do not usually produce an RCRA (Resource Conservation and Recovery Act) regulated waste, they are often reportable events. Clean-up and subsequent administrative procedures involve additional costs, labor, and work delays. Concerns about these releases, especially when they involve Sandia National Laboratories, New Mexico (SNL) vehicles hauling waste on public roads, prompted their Fleet Services Department (FS) to seek an alternative to conventional petroleum-based hydraulic fluids. Since 1996, SNL has participated in a pilot program, along with the University of Northern Iowa (UNI) Ag-Based Industrial Lubricants (ABIL) Research Program and selected vehicle manufacturers, to field test in twenty of its vehicles, hydraulic fluid produced from soybean oil.

The genetic modification of oilseeds has been a critical step in the evolution of biodegradable, non-toxic vegetable oil-based industrial fluids. Oils that are high in oleic acid possess the required properties for many industrial applications and have been successfully used as hydraulic fluids and numerous lubricants. Recently, the DuPont Co. has developed high oleic soybean varieties that produce oil with greatly improved oxidative stability. This oil provides the opportunity to make environmentally acceptable industrial fluids that may be lower in cost and/or functionally superior to vegetable oil-based fluids currently on the market. Research and testing over the last year has focused on utilizing genetically modified soyoil for industrial applications. Using standard bench tests and low volume fluid power pump tests, experiments were conducted to develop a soybean oil-based hydraulic fluid in cooperation with Lubrizol Corporation.

Triaryl phosphates have been used as fire-resistant hydraulic fluids in hazardous applications for many years and are currently finding new markets. There have, however, been some historical concerns regarding their toxicity and ease of handling. This paper reviews the available test data (including the most recent ecotoxicity information) and confirms that commercially-available products have a generally favourable toxicity and ecotoxicity profile.

Traditionally, various testing methods are used to determine the lubrication properties of hydraulic fluids. The specific standard for mechanical testing of hydraulic fluids is based on a special type of hydraulic power unit, the vane pump (DIN 51 389, DIN 51 524). Numerous other procedures for mechanical testing of lubricants are used with the FZG-Test (DIN 51 354) being the most important one, in which the tested fluid is exposed to a certain load by shearing it in a gear set. Moreover industry uses several non-standard ‘in-house’ testing methods. This situation cannot be satisfying in many respects: Since only part of the interaction between fluid and component is tested with the existing test procedures, the validity of test results is limited. Reproducibility of the test results is also limited, especially in the case of the vane pump test, due to the number of necessary test procedures, cost and time expense is too high.

Measuring water quality and preventing drawbacks caused by deteriorated water quality in tap water fluid power systems is a unique problem. Tap water is a suitable environment for waterborne microorganisms. It also contains dissolved and undissolved organic and inorganic matter. Wear particles in the tap water fluid power systems are a separate problem, however closely linked to problems above mentioned. Contamination and the quality of the pressure medium in the system is a function of local characteristics of tap water, operating parameters, system and component design and contamination introduced to the system. To study effects of water quality on tap water fluid power systems, and to evaluate methods for measuring water quality and particle counting, a pilot scale hydraulic system was constructed. The pilot scale system emulates typical operation of a commercial tap water fluid power system.

Computer simulation of product usage is effective in achieving shorter product development time, integrating the efforts of suppliers, reducing test cost, providing early product direction and interfacing to CAD. However, simulation may not be appropriate when no objective metrics exist, the engineering phenomenon is not yet well understood, analysis technology does not exist to handle the specific problem or when knowledge based engineering is adequate. Simulation may be coupled to systems engineering to allow cascading engineering requirements for the entire product by specifying the systems that enable the achievement of customer wants and then cascaded to components that enable systems targets. Virtual Design of Experiments in the simulation process can provide major improvements in all phases of the product development process from concept screening to optimization to robustness.

Kubota has developed a lawn tractor series that will be produced in the USA with good cost to performance ratio and with new features for improved control and comfort. We believe this is the first in the industry of lawn tractor series that features the Cushion Ride system, Auto Throttle Advance system and other features. The new models, that were introduced this spring, were designed concurrently with a horizontal-axis water-cooled diesel engine and a vertical-axis water-cooled gasoline engine. Another new feature is the Electric Power Steering system. I will now discuss these newly introduced technologies.

Measurements were made of the in-cylinder fluid velocities in a crankcase compression, piston ported two-stroke engine under both motored and fired operating conditions to investigate the effect of combustion on the scavenging process. The engine was modified to allow optical access to the clearance volume and was operated in a burst fired manner, where the firing sequence was controlled by modulating the fuel delivered to the crankcase. The burst fired sequence consisted of 30 cycles, of which there were twelve consecutive cycles where fuel was injected into the crankcase. The engine was operated at a speed of 500 RPM, with a delivery ratio of 0.54, and a fuel-air equivalence ratio of 1.28. Laser Doppler Velocimetry was used to measure two components of the in-cylinder fluid velocity at five locations in the cylinder head cup during the burst fired operation of the engine.

The main purpose of this investigation was to develop the virtual prototype of the whole log forwarder by using ADAMS dynamic system simulation software. The virtual prototype contains hydraulic systems of the loader (except the grapple), mechanisms (steering, bogie axles), tire-terrain interaction, the log loader with structural flexibility and the control systems of the loader. Then the virtual prototype was validated with a simple procedure describing loading dynamics.

With the legislative demands increasing on recreational vehicles and utility engined applications, the two-stroke engine is facing increasing pressure to meet these requirements. One method of achieving the required reduction is via the introduction of a catalytic converter. The catalytic converter not only has to deal with the characteristically higher CO and HC concentration, but also any oil which is added to lubricate the engine. In a conventional two-stroke engine with a total loss lubrication system, the oil is either scavenged straight out the exhaust port or is entrained, involved in combustion and is later exhausted. This oil can have a significant effect on the performance of the catalyst. To investigate the oiling effect, three catalytic converters were aged using a 400cm3 DI two-stroke engine. A finite level of oil was added to the inlet air of the engine to lubricate the internal workings. The oil flow rate is independent of the engine speed and load.