Category Archives for Hydrostatic Transmissions

Hydrostatic Drive for Sweet Sorghum Harvester

An experimental vehicle to harvest whole-stalk sweet sorghum was designed by a university research team. At present, the harvester is a pull-type machine, meaning it is towed behind a tractor and powered via a universal joint driveline. The decision has … Continue reading

05. May 2010 by Jack
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Closed-Circuit Closed-Loop Hydrostatic Transmission

The hydrostatic transmission, shown in Fig. 6.28, is operating under a constant load. Speed is set by the command voltage at 1000 rpm. The feedback transducer is a tachometer generator, which produces a voltage proportional to motor rpm. The load … Continue reading

05. May 2010 by Jack
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Servo Pump Operated with Flapper Nozzle Torque Motor

The servo pump shown in Fig. 6.27 is like that shown in Fig. 6.26, except a torque motor is used to position the spool of the servo valve. A torque motor rotates through several degrees of rotation, when a current … Continue reading

05. May 2010 by Jack
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Manually Operated Servo Pump

Before beginning our discussion of closed-loop hydrostatic transmissions, it is necessary to first learn how a servo-controlled pump operates. A variable displacement axial piston pump will be used as an illustration. When configured for servo control, this pump will have … Continue reading

05. May 2010 by Jack
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Four-Wheel Drive Vehicle Hydrostatic Transmission

A configuration where all four wheels are powered is shown in Fig. 6.18. A single pump provides flow to four motors. This machine can be built with two or four steerable wheels. On three-wheel- and four-wheel-drive vehicles, the front wheels … Continue reading

05. May 2010 by Jack
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Three-Wheel Vehicle Hydrostatic Drive

The vehicle shown in Fig. 6.17 has three wheel motors supplied by the same pump. In the design of such a vehicle, care must be taken to size the motors and final drives such that the tangential velocity of the … Continue reading

05. May 2010 by Jack
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Vehicle with Two Hydrostatic Transmissions

The vehicle shown in Fig. 6.14 has a separate in-line hydrostatic transmission for each drive wheel. The engine delivers power via a universal joint driveline to a right-angle drive gearbox. Each side of this gearbox powers an inline hydrostatic transmission. … Continue reading

05. May 2010 by Jack
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Hydrostatic Transmission with Variable Speed Motors

As previously mentioned, it is often necessary to provide a road speed, so the machine can be moved on the highway between job sites. (Generally, these travel distances are only a few miles, so road speeds in the range of … Continue reading

05. May 2010 by Jack
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Two Wheel Motors Hydrostatic Transmission

Wheel motors, mounted at both rear wheels (Fig. 6.12), is a variation of the configuration shown in Fig. 6.11. This arrangement eliminates the universal joint driveline, differential, and rear axle, with resultant cost and weight savings. Because the pump has … Continue reading

05. May 2010 by Jack
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Hydrostatic Transmissions Advantages

A hydrostatic transmission provides improved maneuverability, but at a cost. The efficiency of a hydrostatic transmission is always lower than a discrete-gear transmission. A discrete-gear transmission will typically have an efficiency of 95% or greater, meaning that 95% of the … Continue reading

29. April 2010 by Jack
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