Small steam engine
About 4" x 7".
Each year, I do some new props for Clockwork Alchemy. Here's one for 2015.
Steampunk conventions need more steam engines. So I put this together. It's a toy engine from the 1930s, made by Wilesco. They're still made. Originally it came with a boiler and smokestack, and ran on little fuel pellets. I got this one cheap, with the boiler broken. It was mostly flimsy sheet metal, but the engine parts were well made. So I re-mounted the machinery on a heavy brass plate, then put that on a piece of walnut.
The engine will run on steam, but live steam is too much for CA. So I use a small aquarium air pump, which provides just enough air pressure to make the engine run, slowly.