Dynamics of 3 Points Linkage Hitching (V)

Fundamentals of the Vertical Motion for a Plow

Abstract

Dynamic stability of a plow is the most important problem in plowing. Depth uniformity of the furrow and minimization of the dynamic resistance of the plow mostly depend on this stability. A plow has six degrees of freedom of motion as a rigid body. Pitching and bouncing of the plow have greatest influence on the dynamic stability.
Equations of motion concerning the pitching and bouncing of a bottom plow are derived considering the deviation of the three components of the draft and pitching moment due to depth and attack angle variations. Refering to the stability criterion by Routh and Furwitz, it is concluded that the plow is not always stable.
There considered two ways of stability compensation. One is that the increase of directional stability by the long land-side, gage wheel and furrow wheel. In this case, however, plowing resistance is also increased. Another compensating device is the hitching mechanism which intervanes between the tractor. Fundamental characteristics of the hitching mechanism are as follows.
1. Restoring orientation of the plow is maintained for the depth deviation from the equilibrium.
2. Spring constant at the hitch point should be as small as possible. Namely, free linkage hitch is desired unless the hydraulic control is employed.
3. Draft point of the plow should be located as close as the hitch point and the gravity center is desired to be as low as possible.
4. Restoring moment is desired to be as great as possible by the configuration of the plow.
In case of the free linkage hitching, stability criterion for the hirizontal and vertical motion is not simultaneously satisfied. For further performance, hydraulic controlled linkage hitching is desired.