[SgtMillhouse648]

I think you misunderstood me on the tensioning. Let me see if I understand how this works correctly to drive the wheels:
1: motor turns chain which powers the drive sprockets on top of modules
2: drive sprockets turn a shaft going through the center of the module which has a bevel gear on the other end
3: bevel gear meshes with another bevel gear, turning the rotation along the vertical axis to the horizontal axis
4: This second bevel gear powers a chain drive which goes down the interior of the module directly to the wheel.

I realize how easy it is to keep tension on the 1st step, what I am worried about is in the 4th step, especially if you are using #25 chain. With #35, you don't have near as big of problem, but there's still a problem.

Nice work though.
Malhon