The rolling resistance of the tractor wheel are researched by the soil deformation and the equili-brium of the force in this paper.
In Table 1, all cases of the force equilibrium on the equation (1) are shown, and the letters in it are
R
n: Normal component of the soil reaction force to the wheel. R
t: Tangential component. P: Drawing force. G: Wheel weight.
θ: Angle between the radius to the wheel center from the soil reaction point and the radius perpendicular to the plane which the wheel are driven.
R
t>0: Possitive to advance.
R
t<0: Negative to advance, for instance, by the brake, bearing friction, etc..
P>0: The case of the wheel drawn by the other force P.
P<0: The case which wheel are drawing.
Strictly, the rolling resistances of the powered wheel are different from them of the non-powered wheel. It is recognized by the soil deformation. They are shown by the equation (4) and (5).
(4) gives the resistance of the unpowered wheel, and (5) gives of the powered wheel. On ascent slope and down slope, they are given by the equation (8) and (9). α is the slope angle.
The maximum point of the rolling resistance on the powered wheel is caused when θ=π/4, and that magnitude is G/2, whine on the non-powered wheel, it is caused when θ=π/2. At the large velocity, as the wheel surface conflicts with the obstacle on the hard soil, the rolling resistance increases.
From above reason, in V, the results between the rolling resistance and the condition of the soil, the material, the width, the pneumatic pressure, the shape of lug or tread and the size of wheel, etc. are conducted.
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