How to mount hub motor with strange shaft profile

Question

I'm thinking about buying a hub motor that seems to be relatively common in the alibaba/ebay world but has a pretty strange shaft coming out of it (see pictures). It has a D profile that doesn't go all the way to the end of the shaft, and it seems to be 24.8mm in diameter, not 25 or 25.4.

Is this some common size / shape that I'm not familiar with? Is there some specific part that it is supposed to mate with?

Barring that, how would you design a simple, cheap mount for this motor? I have some ideas, but I'm interested in seeing what others come up with.

I've also asked the supplier these questions but I don't have a lot of faith that I'll receive any feedback.

Answer 1

The shaft is slightly undersized so it will fit into a 1" hole in a worst-case tolerance stackup (called a clearance fit). The fact that the flat does not extend all the way to the end of the shaft is because this will prevent the thing that has been set screwed onto the end of the shaft from flying all the way off the shaft if the setscrew works itself loose.

Answer 2

The motor design in the image provided is consistent with a hub motor for a bicycle or other electrically powered vehicle. I expected to see a matching flat on the opposite side of the shaft, to accept a typical bicycle fork. This does not exclude the concept that this shaft is designed to be fixed in place while the hub/motor assembly rotates, providing motivation to the vehicle on which it is installed.

An appropriate mount would be a flat bottom fork with a "cork" or latch type securing device pushing the axle of the motor into the bottom, preventing rotation. One could also use a radiused-bottom slot with a set-screw of some sort to prevent rotation, but the flat bottom design provides for greater surface contact.

The power/control wiring exits from the shaft, confirming that the shaft does not rotate.