Applying Electronic Autoshift to a Log Loader Propulsion System

In typical powershift transmission applications, a torque converter is used to absorb energy during the changing of gear ratios. This paper describes an application of a powershift transmission without a torque converter and its related inefficiencies. The system incorporates a variable displacement hydrostatic motor directly mounted to a powershift transmission on a self-propelled log loader. An electronic control provides automatic synchronized shifting of the powershift transmission and hydrostatic motor displacement.

This system provides propulsion that achieves significant tractive effort in rough terrain and load-towing, yet provides adequate speed for highway travel, all with operator ease.