Thanks a bunch.
The 50s Erectors come with motors and gear boxes. In the cheapo 2 sets I got (only $5 a piece not including shipping) there are 3 gear boxes 2 with motors attached and 1 without. (The without will become a steam powered gearbox.)
Anyhow from the factory I noticed they used pan head set screws but they sometimes interfere with the gears. A dum dum design. I went to the hardware store and got #6 grub screws and it's much better.
The gear box gears should be beveled for better engaging...