Motorized Erector Set Drive Shaft

I designed this after buying a used motorized Erector set for my son at a garage sale, and discovering after we got it home that it was missing the drive shaft piece, part # A460.

Since I had no original part to work from, I took measurements of the slots on the motor, and estimated the length based on information I could find online. I know the official part has dimples on the inside of the groove, so this isn't 100% true to the original, but it's close enough so that it functions fine.