I think that the key and the lock washers would do more to fix the gaers in place on the shaft would provide considerable "grip" on the gear. The spacers are mostly for spacing, and really don't provide a lot of structural strength.


As to precise measurements for spacers, the aluminum is soft enough to work easily, so a hacksaw and a file should be adequate to cut(slighty big) and fine tune the spacer. So I think FIRST is correct in saying the Chasis could be easily built with handtools. The only reall hard part is making a hole for the axel through the square aluminum
tube. Hard to drill a hole that big with hand tools. A small hole could be drilled and then enlarged by hand filing, While a spurred wood spade bit in a drill press would work - I don't feel that is a very safe method.

I think we will get 5fps with the FIRST supplied drive in low gear.