Quote:
Originally Posted by asid61
Assuming that your gearbox is direct driving the center wheel, here's a list of forces:
1. upward force from the effect of gravity on the wheel shaft
2. forces between gearsets (look up calculating the force of a spur gear)
-These translate into forces on the bearings, and thus the holes in the gearbox plate.
3. forces on the sprockets going to the front and back wheels (although this might cancel out, I'm not sure).
There might a couple more but those seem to be the major ones.
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Having done a minimal amount of FEA on gearbox plates for comparative purposes, this is a good starting point. A couple forces that I would add are the cantilevered weight of the CIM motors, and the clamping force caused by the bolts through their standoffs.
An important thing to remember when going down the path of FEA is that it can only help you prepare for forces in the mechanism that you can accurately predict.
For something like a gearbox, it is impossible to predict all of the forces that it will undergo, so it is not a good idea to make your design purely off of the FEA results, and it is a good idea to keep a safety factor of 5 or greater.
With that said, I think FEA is an incredibly valuable tool, because it can teach students about the way stress and strain work in materials without having to build and break mechanisms. I plan to hold a CAD class for our team this year that will include some FEA training for this reason.