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Help with torque caculations

I need some help with figuring out the maximum payload for a robot I’m designing.

I'm looking in to using either the Wild thumper 4wd (http://letsmakerobots.com/node/14156) or the Rover 5 4 motor version (http://letsmakerobots.com/node/23331)

Both of the data sheets for these robots provide the gear ratio and stalling torque for each motor is it possible using these values to calculate the maximum payload I could use on these platforms?

Rover 5 has a stalling torque of 10Kg/cm and a gear ratio of  86.8:1

Wild thumper has a stalling torque of 4Kg/cm and a gear ratio of 35:1 (or at least the version I’m looking at does)

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There are other factors involved in calculating your payload. To begin whith the strength of the chassis. I would not recommend any more than 1Kg for the Rover 5.

Because the Wild Thumper 4WD has a suspension system you need to consider it as well. With the suspension set as hard as it will go for all 4 wheels you could probably carry 4Kg as long as the center of gravity is kept low. If the weight is too high then it will probably lean to one side or the other.

Now you can look at the maximum incline the robot could handle. Assuming your robot is not top heavy then your Rover 5 (4 motor) should have plenty of torque so traction will be the problem. Once you get beyond 45° then your center of gravity and traction will both be a problem

The Wild Thumper 4WD will have similar traction and center of gravity issues assuming the 75:1 gearbox is used.


You need a bit more info first.
You already have the torque values, but for each example you'll also need the chassis weight (everything but the payload) and wheel diameter.

Another parameter you need to consider is the maximum angle you want to be able to climb. If you're running around the house on flat floors, a few degrees may be acceptable. To climb rocks and hills outside, you'll have to use a more ambitious value for your angle.