What is the torque required for a track to climb over a step

[zephyrific]

I'm trying to figure out whether it is best to use a multi-wheel or track system to get an object over a step, however I'm having a bit of trouble finding the torque needed for a track to pull itself up and over.

Diagram of course is not to scale, but I've drawn up something of the situation. I'm not sure of whether to consider the radius of the wheel in contact with the step or rather the track as a whole, or if I'm approaching this completely incorrectly.

Also, to clarify, the weight would be distributed across each point of contact with the ground, and also the point of contact with the step, correct?

 

[jrmichler]

Draw some free body diagrams:
1) Immediately after R2 lifts off the ground.
2) At several stages from that point until the mechanism goes over center and is fully on the step.

Each diagram will have different forces, and a different torque on the driver wheel to produce those forces. One of those positions will require the most torque. That is your design torque.

Now adjust the design, and repeat. The process is tedious, but at the end you will have an excellent understanding of the proposed solution. If you have not yet had free body diagrams, then consult Mr Google.