I was going to take a new picture of my UGears wooden model kit, but . . well, you know, life gets in the way a bit sometimes. So this is one from when I had just finished it last summer.
If you know anyone who likes to make models then I can highly recommend these - all wooden kits, all gear driven in some way or another, well made if a bit fiddly to construct in certain areas, and great fun to make.
This one has an elastic band powered system that drives the car along - the engine is exposed because that is also moving parts - the pistons stroke and the valves open and close while it goes along. It only goes a few feet, but fun.