トラクタの転倒に関する研究 (第1報)

動横転倒の解析と実験

抄録

In order to investigate the dynamic side-overturning of tractors, the authors analyzed the problem mathematically and carried out some experiments with a 4-wheel model tractor whose size was about 1/5 of the ordinary tractor. The main results were as follows:
1) In this paper, the tractor was regarded as a rigid body with a single degree of freedom, and its motion was described by the equation (4). The limits of side-overturning were determined in terms of initial conditions of the equation, namely, φ₀ and ω₀ or v₀.
2) It was supposed that the tractor travelling along a contour line on a slope overturned sideways under the following two states; a). the upper side wheel of the tractor would run up a triangle obstacle. b). the upper side wheel would run against the obstacle and rebound with the restitution coefficient e. Then, the critical running speeds which would cause the tractor to side-overturn in the states were calculated by the equation (8) and (16), respectively.
3) The theoretical equations indicated that the critical angle of side-overturning of tractors decreased with the increase of the height of center of gravity of the tractor, the obstacle size and the running speed. The experimental results agreed more closely with the values calculated by the equation (16) than by (8).
4) As the upper side wheel rises from the ground, the point where the tire of opposite wheel contacts with ground transfers outward and it makes a tractor difficult to sideoverturn. The theoretical values modiffied by such an effect coincided closely with the experimental results.
5) The experimental results showed that the more the center of gravity moved to the front part of the tractor, the more easily the tractor side-overturned. This was due to the fact that the transfer of a contact point of the front wheel was smaller than the rear one, because the tire width of the front wheel was narrower than that of the rear one.