Discussions on the Slip-Sinkage of Tractor Drive Wheel (VI)

Transient Phenomenon at 100% Slippage

Abstract

In this paper, the slip sinkage phenomenon of a tractor drive wheel at 100% slip condition under the pulling load was discussed, especially on the slip sinkage transient curve and the torque of the drive wheel axle. In estimating the torque of the drive wheel axle, two kinds of method were applied.
1) The use of the relation between the mean contact pressure and sinkage, derived from the geometrical relation.
2) Application of the quadratic curve to the radial contact pressure measured with a pressure sensing beam on the wheel periphery.
Shear force at the interface between the tread and the soil was estimated by multiplying the radial contact pressure by the frictional coefficient at the interface.
The torque of the wheel axle was calculated by integrating the shear forces along the contact length.
On the other hand, the relations between the rotational angle of the wheel axle and the sinkage were obtained from the tests under the constrained condition of the horizontal motion of the wheel. Tests were held for three kinds of soil hardness 0.2, 0.4 and 0.6kg/cm² respectively.
Those relations were applied to the model of the drive wheel shown in Fig. 2, and the results of the theory and the experiments on the sinkage were compared.
It was found that the geometrical mean contact pressure in radial direction was more efficiently available to estimate the wheel axle torque. The estimated values using a geometrical mean contact pressure was quitely coincident with the experimental ones.