3 cylinder radial air engine

There is somewhat of a challenge. Build a 5cc air engine which can drive a propeller and see if we can compare them :)

I was starting a more complicated design but someone challenged me to make an engine with a rotary valve, so here it is!

It's running very quiet and smooth.
It's very easy to build, just print the parts, get the bearings, some o-rings (or glue), some small bolts and a piece of 3mm steel rod for the crank and you're set.

When you're done building make sure to drill some small (1.5mm) holes just above the piston when it's at BDC so the air can escape. I didn't print this in to make sure the cylinders are smoother.

Some quick fresh video's..
Running at 4 bar: https://www.youtube.com/watch?v=H2KQvAMbInc
Running at 8 bar: https://www.youtube.com/watch?v=Wo2Qotynjrk