So often, 3D printer owners buy their machines with the promise of freeing themselves from the shackles of commercial manufactured items, and making all sorts of wonderful and useful things to improve their lives. Then they proceed to print a menagerie of good luck cats and toy elephants, that little tugboat, and a host of other pretty but ultimately useless items in garishly colored filament.
Perhaps this is an unfair assessment, but if you have the sneaking feeling that it might just describe you then could we point you at something that while it still has little use is at least interesting to play with. [Gzumwalt]’s single cylinder air engine is as its name suggests, a piston engine that runs on compressed air. You don’t need a shop compressor though, your lungs or an inflated balloon will suffice.
It’s a simple enough design, but it does incorporate two connecting rods, one of which drives a sliding valve. All the files are available for download, and there is a video we’ve placed below the break showing it chugging away nicely from a balloon. It might not be the most useful of engines and it may not bring you good luck, but it beats a plastic menagerie in the interest stakes.
We’ve featured a very similar engine made from lasercut ply in the past, but most impressive is this very practical engine converted from a lawnmower unit.