Hey guys, I'm looking to do several high school lessons on the mechanical advantage of gears...including rpm calculations and gear ratios. I've searched and searched, but can't seem to find any good gear models/demos for students to use to build and experiment on their own. It seems like plastic gear kits are easy to come by...but I'm wondering, how would we be able to build gear trains from them easily? All I can think of is a self-built board with holes for dowel insertion. Any other ideas on what I may have missed would be extremely appreciated!