paper: Analysis of “a torque-actuated module” used for strafing in an H-drive.

[RyanCahoon]

Originally Posted by GeeTwo

As you note, for small θ, the term deriving from B (the one with tan θ) is much less important than the term deriving from D (the one with sec θ).

I think I follow now. However, it seems to me that you're missing a term in equation 3: the force on the module by the pivot axle's bearings. Without this, you have forces at the wheel pushing up and force at the interface between the gears pushing down (from the frame of reference of the module), so there's an unresolved torque moment that will cause the module to rotate counterclockwise.