CIM Motor Shaft Bending Moment

Technical Motors
1

We’re working on a design project, and this will require having the pinion gear on a CIM placed far out on the shaft before engaging with the gear in a gear box. I know that bending moments are undesirable on motor shafts, but most gearboxes place some bending load on the motor output (torque divided by the cosine of the pressure angle times the pitch radius) unless there’s an equally spaced distribution of evenly loaded output gears and/or you’re running a planetary gear box.

Does anyone have any reference for the maximum allowable bending moment on a CIM? I can’t find anything like that on the application drawing, but it has to be able to take some amount of bending, or all interfacing gear boxes would need to be planetary.

Thanks.

2

It is a lot for FRC applications, considerably less if you want it to last a normal lifetime. I would think the limiting factor is the shaft bushing (and the resulting friction), since the shaft itself is fairly stiff (it should support several hundreds of pounds without bending). You can dramatically increase overall side load capacity by installing a roller or ball bearing somewhere along the shaft, even if it is between the gear and the motor case it can carry a lot of the load, or ideally at the far end of the shaft.