An infinitely variable transmission (IVT) for instructional purposes was designed and built. It was an input-coupled power split transmission with a hydrostatic transmission used as the variable unit. Components for the IVT have been chosen based on creating a model to teach students the function and operating characteristics of an IVT. Visibility was a key to determine placement of components. The IVT cart was built to connect to a dynamometer for output power, torque, and speed measurement. The IVT was instrumented so that input torque and speed as well as hydraulic oil pressures, temperature, and pump swash plate position were monitored. The displacement of the hydrostatic transmission is controlled by a stepper motor. Through a controller area network (CAN) system, all variables and parameters can be displayed; with a personal computer connected, data logging can be accomplished easily. Example laboratory handouts were created to streamline instruction and assess comprehension of IVT concepts.

A 6.2 kW diesel engine was selected to provide power to the IVT. Timing belts and pulleys transfer power between the hydrostatic transmission and the input and output. A 3:1 planetary gear set was selected to sum power at the output. The hydrostatic transmission selected has a variable pump and fixed motor with displacements of 21 cc per revolution. The maximum allowable pressure in the hydrostatic transmission is 145 bar and cross-port relief valves were added to limit the pressure. The output speed of the transmission is infinitely variable between approximately 20 and 2500 rpm for an input.