[UCGL_Guy]

While the off the shelf trannies are great and work wonderfully - don't cheat yourself or students out of the learning experience available by designing and building your own. Look at it a another project. Pick a couple of ideas choose the style you want then begin designing it to meet your own criteria. The pride developed by doing this is immense. Our team loves our 3 speed trannies based off of 222's. We made our own tweaks and such and they hae worked great this year.
Most of all this can be fun and frustrating - start early - and test to refine your work of art.

Ken