If we know the maximum load on the vehicle,how to calculate the torque required at the crankshaft to move it.?

Answer 1

Load is a somewhat vague term. If you are referring to the power produced by the motor, then it is easy. The torque at the crankshaft in ft.-lbf. would be (Power [in hp] x 5252)/ n (in rpm).

If you are refering to the power produced at the wheels it would be the same, except you would need to divide your answer by the efficiency of the powertrain (usually between 85 & 95%). Power is constant through gear reductions, like the transmission and differential.

If you are calling the load the force at the wheels, then it is a little meticulous. First, you would find the torque at the rear axle by multiplying the wheel force by the wheel radius. Then you divide the axle torque by the differential ratio and multiply that result by two (for both wheels) to obtain the driveshaft torque. It does not matter which rear wheel since torque is constant across a differential (at least for an open differential). After that, you divide the driveshaft torque by the transmission ratio (that would depend upon which gear you are in). Finally, divide by the powertrain efficiency. Good luck.

Answer 2

T*w = F*v (Power applied by torque = power used by vehicle against load)

w = angular velocity of shaft
v = linear velocity of vehicle
F = total load

T = F*v/w

Answer 3

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