[MrForbes]

bolting the arm to the sprocket should work ok. The Igus 5/8" (from last year) or the new KOP 1" shaft and bushings is nice for making stuff like this pivot.

A 3/8" bolt is usually torqued to about 35 ft lbs when we use them on cars, so it should handle 28 ft lbs just fine, although the key may or may not be up to the task. you can calculate the shearing stress in it by figuring the torque is all transmitted to the key at the outer diameter of the shaft, and the key has a known cross section that must withstand that force.


and ditto on the motor torque, you want to load the motor much less than the stall torque, so it will last. 20% would be nice.