Traction Analysis of Farm Tractors (I)

Statical Analysis of the Traction Type Farm Tractor

Abstract

Although there are many reports on the experiments about farm tractors, but not yet systematic mechanics of traction mechanism is established, because those experiments were drawbar-pull tests for practice, not for mechanical analysis. These studies are fundamental studies on the traction mechanics of farm tractors and their hitches.
In this report 1, as fundation of these studies, statical anaysis of the traction type four wheel farm tractor is presented 1 by introducing new ideas, such as, the critical hitch height and the critical pull angle, and a new calculation formula for required engine horsepower for the tractor which is engaged drawbar-pull on the grades.
According to this study, following conclusions are obtained;
1) The weight transfer should be confined to the relative change in vertical soil reactions against to the traction wheel and steering wheels, accordingly the vertical component of drawbar pull is excluded from the weight transfer term.
2) The maximum drawbar pull Pm is confined by following three conditions; a) the magnitude of engine horsepower and b) reduction ratio of power transmitting gears, c) stability of the tractor.
3) The maximum drawbar pull Pm changes its magnitudes according to the hitch height and pull angle and reaches its maximum at the critical hitch height y and pull angle.
4) From the standpoint of stability of tractor, the hitch height and pull angle should not exceed their critical points.
5) In order to use the weight of tractor for drawbar pull effectively, the weight transfer be increased to its maximum.