P-Mag electronic ignitions require a blast tube to prevent overheating the internal electronics. I became tired of removing and reinstalling the blast tube attachments to complete the recommended annual inspection.
I designed and 3D printed a simple cooling shroud to direct cooling air over the P-Mag cooling fins. The shroud is retained in place by a simple over-center position; the ears require a slight push to pass the full diameter and a slight pull to remove. There is no mechanical strain on the 1-inch SCAT tube, and it stays in place without a hose clamp or zip tie.
P-Mag ignitions have a factory applied 93°C (200°F) thermal indicator sticker to witness an overheated ignition. To put the “experiment” in experimental aviation, I installed a shroud on one P-Mag, left the standard blast tube on my other P-Mag as a control, and installed a wide-range thermal indicator sticker on both ignitions—both ignitions read identical maximum temperatures.
The mockup was printed in PLA filament material to test the fit and required several iterations to ensure a good fit and clear the mounting studs and nuts. PLA’s heat deflection temperature is 50-60°C (122-140°F) and would not survive in a hot engine compartment. My flying prototype is printed with PA12-CF—a carbon fiber reinforced nylon, resistant to fuel, oil, and solvents with a heat deflection temperature of 175°C (347°F).
An even better 3D printing material is ULTEM, which is FAA certified for flame, smoke, and toxicity, but can only be printed on expensive industrial printers; there are commercial 3D printing websites to upload a CAD file and send a finished part in a material of your choosing.
Download this STL file from Printables.com.
Does this fit both 4-clinder and 6-cylinder P-mags? If not, which one?
4 cylinder; it may fit a 6 cylinder, but I don’t have one to check the fit. I could easily make a 6 cylinder version if someone can send the dimensions and test fit it.
The file is in mm scale, correct?
Yes
Thanks, Dan!
My 1st foray into 3-D printing!
I like it. Thanks!
Someone print and sell! I’d buy two.
There are plenty of online 3D printing services, you upload the file, and they’ll mail the finished product. You need one printed in ULTEM to be fireproof – not something that can be done on home printers.
Any you’d recommend in the US?
There are 3D printing services that can make you a set, but printing and selling them goes against the license under which the model is provided. https://creativecommons.org/licenses/by-nc-sa/4.0/
Check out a few these, for example:
https://www.fictiv.com/3d-printing-service
https://www.hubs.com/3d-printing/
https://www.xometry.com/capabilities/3d-printing-service/
Thanks for this printable file. Where did you purchase the thermal indicator stickers
Amazon
https://amzn.to/3JTfcyY