Performance and Analysis of a Dynamic Loading Four Square Machine for Crawler Tractor Power Train Development

This paper describes a machine that tests crawler tractor power trains through application of the four square principle. Two units coupled to form a “closed torque loop” require only power input sufficient to overcome frictional losses.

A computer governs test operation - from monitoring system parameters to control of a gearbox for dynamic torque loop loading.

The loads at selected points in the closed loop were found to be dependent upon the directions of machine rotation and torque. It was concluded that frictional losses in the closed loop caused significant differences in load levels at the driving and driven test units.