Archive for April, 2010

Hydrostatic Transmissions Advantages

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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 input energy is delivered to the load (wheels). A hydrostatic transmission has an efficiency of …

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Hydrostatic and Mechanical Drives Comparison

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Hydrostatic and Mechanical Drives Comparison

The same vehicle shown in Fig. 6.1 is shown in Fig. 6.11 with the mechanical transmission replaced with a hydrostatic transmission; all other components remain the same. To provide a specific example, we will begin by specifying a variable displacement axial piston pump and a fixed displacement axial piston motor. Pump output is increased by …

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Hydrostatic Transmissions

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Hydrostatic Transmissions

A hydrostatic transmission (HST) is simply a pump and motor connected in a circuit. Other components are added to obtain certain operating features. The four basic configurations of hydrostatic transmissions are : 1. In-line (Fig. 6.10a) 2. U-shape (Fig. 6.10b) 3. S-shape (Fig. 6.10c) 4. Split (Fig. 6.10d) Various pump and motor designs can be …

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Automatic Transmission Shift Control

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Automatic Transmission Shift Control

Performance of a direct-drive transmission with six shifts (six gears) is compared to a torque converter/automatic transmission with three shifts in Fig. 6.9. Note that the torque converter “broadens” the power transfer bands with the three shifts such that the power line is equally as smooth as the power line produced with six shifts. However, …

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Mechanical Transmissions

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Mechanical Transmissions

A vehicle with rear-wheel drive has the components shown in Fig. 6.1. For purposes of discussion, we assume that the mechanical transmission has four gear meshes. (Functionally, a mechanical transmission can be thought of as a black box with gears inside. The meshing of these gears gives an output shaft speed lower than the input …

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