This is working compressed air engine that is fully 3D printed and does not require any hardware. The design is based on thing:576482 and has added functionality. This engine can operate from compressed air and can deliver substantial power via integrated Gear on flywheel.
Most likely I will continue development of this engine and add power modules and accessories. Let me know what would be good development for this engine.
The engine design process and tests are available in https://youtu.be/ciSbL8yVtwA and the build process https://youtu.be/a1t0a2YkKbk .
Sanding is required for all contact surfaces
What tools and software was used in design
The design is using openscad 3D design software. There are three files with .scad extension that contain the design. You can modify and visualize any portion of the design using this wonderful program.
I also used gvim editor for tex and Cura slicing software.
All three programs above are available online for free download.
Overview and Background
Recently I was interested in this oscillating dual cylinder engine (https://www.thingiverse.com/thing:576482). After printing it I quickly discovered that there is lots of sanding required. After spending few hours on sanding and testing the engine I gave up on making it work and decided to redesign it. The problem with this engine was the friction. There were too many moving surfaces, so much so that engine failed to operate even briefly.
My first effort was to modify the cylinder, since it was most obvious imperilment in this design. My first iteration of cylinder had about 60% less area and I noticed that the bottom of cylinder housing was very hard to reach for sanding and cylinder was getting stuck at that position. I quickly redesigned, sanded and fitted new cylinder and try to test it again. Once again engine did not budge. At the time I was experimenting with running this engine with compressed Air and noticed that after a while the cylinder housing was moving away from the air source, since there was very little force pushing it against the side support, exerted by tiny spring. Back to drawing board and I redesigned the spring, making it much beefier. One more test later found that it made things worst in old design, since more of surface areas were in contact and friction increased.
I was hooked and spent too much time on this design, so I redesigned the cylinder housing, crankshaft, connecting rode and added a gear to the flywheel. Finally all the designs are done and parts printed. It took me half an hour to sand and fit the engine parts and I was able to start it with compressed air very quickly.
Engine design process
Engine assembly and test
Lesson Plan and Activity
Few notes on getting the best results
- It might be beneficial to print the cylinder, cylinder housing, crankshaft/flywheel and cylinder connecting rod at 0.1mm Resolution. I printed my engine in 0.2mm resolution which required bit more sanding
- Make sure you sand inside cylinder housing, cylinder, crank shaft and inside cylinder connecting rod for nice/loose fit before assembling the engine. Use 150 grit sandpaper for coarse sanding and finish of with 600 grit for polishing. Allocate at least half an hour of sanding
- When assembling do not use any tools. You can easily break the parts if tightened too much by using tools
- Make sure you use supports when slicing the crank wheel/flywheel, otherwise you will have failed print
- Apply oil to all moving surfaces after everything is sanded/fit and assembled
Material needed and print settings
The Engine was printed with PLA using following settings:
- 0.2mm resolution (0.1mm recommended)
- Infill cubic, 20%
- Sandpaper 150 and 600 Grit
- Compressor or compressed air source with 60 PSI pressure