Modular Compressed Air Engine - Ultra simple - Easy print

Here is my 15.1mm bore x 8mm stroke air engine, It has no moving parts other than the piston and crank, it is very simple to build and is modular, so you can make any configuration you like. You only need about 5 files to make a working engine, the rest are supplementary. It can run at very low pressure, once well run in, it can run with you blowing down the inlet and at 5 bar it absolutely screams. There is a video on the youtube page about how to assemble.

It should run without any post processing, it can be easier if you deburr everything and give the pistons a light sand with fine sandpaper. Each STL is already in its optimal print orientation. Print everything at 0.2mm layer height, except the cylinder which is better at 0.1mm. Hardware required: 8x14x4 ball bearings - these go onto each crankshaft end 5/32" (3.968mm) ball bearing - (I'm certain it would work on 4mm if that's what you have) - This goes into the cylinder head and acts as a valve.

edit 16/12/2025 There is now a "crankcase exit" cylinder and "CCV" pistons. This is a new cylinder and piston to use together for more power and that dont have the exhaust exiting up the side, instead it exits through the piston and out of the crankcase. The rest of the engine is exactly the same, just no exhaust up the side.

There are now blanks to fill in the holes in the crankcase if you decide to make an inline engine or you just want to cover the crankshaft up in the vee.

This is all getting complicated. if you want to just print a damn engine use this link as it contains everything you need to make a v twin, no more no less. https://makerworld.com/en/models/1853394-modular-compressed-air-engine-v-twin-v8#profileId-1981546

Here's it assembled and working in CAD https://youtube.com/shorts/Erdt_70NapY?si=cgAdvTmbGsWMXcxX

Heres an instructional video of how to assemble https://youtu.be/TybmrVnv_PU?si=x9X2glEmEjPNOnRg

Here's the v8 actually running, enjoy :) https://youtube.com/shorts/stC0X5MKamU?si=9XTnqQFmzU5EkI3t