I was able to print this single cylinder in 1 hour, which allowed me to easily test design variations. Eventually this block, piston, and connecting rod would be used in 4cyl versions.

I found tolerances as low as 0.2mm between moving parts allowed smooth movement. This cost print speed and accessibility for printers that aren’t tuned as well.

Small bridges were added to the design underneath connecting rods and each piston skirt. This allows the printer to almost “print in thin air”.

Full disclosure, this crankshaft design does not exist or function in a real engine. The vibrations would be very bad, but I love it as a desk toy.

This model is the most common 4 cylinder crankshaft design in consumer engines. If you drive an economy car, chances are this is what’s under the hood.

Current plans involve a central drive gear, dual belt system printed from TPU, and the ability to slap two engine variants together for comparison.