Modular compressed air engine (Working)

thingiverse

Here is rewritten text: Singe cylinder: https://www.youtube.com/watch?v=CXvYDukyVZk Flat twin: https://www.youtube.com/watch?v=BERMDl2_mkg Inline 5: https://www.youtube.com/watch?v=2sBuIyi753A After the radial (https://www.thingiverse.com/thing:3224004), I wanted to make some improvements: - A modular design that can be either inline or flat twin. - A different crank that would give more efficiency, as my goal is to run it on lung power. - Mostly parametric design. This design can be built as a single cylinder, a flat twin, or any multiple of those. To do this, you need to print the cylinders 21mm apart so they fuse together in your slicer. You should be able to make any inline or flat design. My goal is to make an inline 5, that's why the crank has a 72 degree offset. There is also a 90 degree offset crank for a twin/four. Tips and requests are welcome. WARNING: Although I can run them at ridiculously high pressures with cheap PLA, it IS dangerous. If your engine doesn't explode, it will probably make lots of torque like mine does and CAN hurt you. Be careful. Wear gloves, glasses, and hearing protection. Part list for a flat twin: - Some PLA - 2 m2 10mm bolts for the pistons - 2 m2 10mm bolts for the rockers - 10 m2 10mm bolts for the heads - 2 m2 10mm bolts for the cam follower - 2 4.2mm m2 thread for the cam follower bearing (optional) - 1 2mm * 14mm steel rod for the crank - 4 m3 10mm bolt for the crank cases - 2 6mm airsoft bullet, or print the valve.. - 2 2mm * 15mm steel rod for the valves (drill the airsoft bullet), experiment with the length. - 2 2mm * 33mm steel rod as pushrod, experiment with the length. - 1 m3 hex bolt and nuts for the propeller - 1 m3 bolt for the other side of the crank - 2 O-rings 4.5mm inner, 8.5mm outer diameter, 1.85mm thick. Things that were done: - The rocker was changed as it seems to break at 7 bar, which is when it runs like a madman. - The cylinder is now a hole all the way through for easy assembly. - The cam follower is beefed up as it broke once. - The valve-spring space was made a little tighter. - Conrods that can be used without bearings were added. I'm running them and it seems to work ok. Changelog: 2018-12-13: The single cylinder version was running very well so another cylinder was made, and the flat twin ran nicely also. 2018-12-11: Today I ran the engine for the first time (single cylinder). The goal is to test the build and performance. The following is wrong: - Continuous air leak. Not sure if it's the ball seal or something else. - Cam opens too short. - Used a too soft spring which slofs the engine down at higher pressure levels. In short, it does run even at 1 bar. I'm running a fairly large 10x5 Master Airscrew. It really needs the weight of the propeller and the engine shakes a lot due to the torque. I never ran the radial as a single cylinder but it shakes less. The ball bearing rolling on the cam is a huge success. I tried it without one first (solid print) and it has a lot of resistance. Next: - Fix the leak - Try a little different cam - Maybe print another cylinder set to make a flat twin (same cam ;)) - Video? 2018-12-7 0:39: Updated all STL files. There is room for a second bearing close to the prop. Added a prop adapter Added a m5 air nipple Changed a lot of small things