Studies on the Overturning of Tractors (II)

Analyses on the Side-Overturning of Tractors using the Model with 2 degrees of Freedom

Abstract

In order to investigate the dynamic side-overturning of tractor, the authors analyzed the problem mathematically and compared with the experimental results. In this paper, a tractor was idealized into a model of spring-mass system with two degrees of freedom, and the pneumatic tire was assumed as the parallel combination of linear spring and viscous damper.
(1) It was supposed that a tractor overturned when its uphill wheel ran up a certain obstacle (sine curve, triangle) on a slope. The critical running speed which brought the tractor-overturning on several slopes was calculated under the above mentioned states.
(2) When the upward velocity of the uphill wheel on an obstacle was larger than the critical upward velocity calculated by the equation (20), the tractor overturned sideways.
(3) The calculated values indicated that the tractor was apt to overturn with the increase of the height of obstacle and the running speed. It became more difficult to overturn for a tractor as the spring rate decreased, and the tractor didnot overturn when the spring rate and the height of obstacle were smaller than the limited value, respectively.
(4) On the model tractor, the experimental results with the triangle obstacle were nearly equal to the calculated values in the assuming that the tractor bounds up at the top of the obstacle.