Technical Paper
Unitized Power Unit for Compact Lawn Tractor
1991-11-01
911262
Use of the hydrostatic transmission (HST) in compact riding mowers has recently become more widespread due to the fact that an HST provides considerably better mowing performance than a conventional manual transmission. In addition, there are now several manufacturers that are capable of building compact and efficient HSTs. The standard power train of an HST-equipped compact riding mower consists of the engine, HST, and transaxle, laid out separately and interconnected by a V-belt. As a result, the power transmission system is highly complicated, making maintainability difficult. The recently developed model PA540A and PA420A unitized power units are compact power packages combining a vertical gasoline engine, HST, and transaxle in a single structure that can be mounted with as few as 3 bolts, allowing much greater freedom in mower design.
