P.Harmonic Gear Reducer

thingiverse

Watch it go at: https://youtu.be/sdRGrTHq4hA This gear reducer is a hybrid of a planetary drive and a harmonic drive. It starts off with a conventional set of 5:1 planetary gears. The ring gear has 96 teeth. But then I've extended the planets and sun gears and added an additional flexible gear with 93 teeth, essentially creating a harmonic drive. The overall reduction 155:1. It's no surprise that the estimable emmett has also designed a hybrid planetary/harmonic drive - https://www.thingiverse.com/thing:219779 - but this one uses a significantly different structure. The flexible gear is coupled to the output ring with flexible fingers rather than with a flexible cup, and the output ring is supported by a ball bearing using 6mm dia airsoft pellets for balls. I designed this to mount on a standard NEMA 17 stepper motor, although you can demonstrate by hand it without a motor, or the ball bearing, in fact. Final note: This is mostly just a demonstration gear reducer not intended for extended use. I printed mine out of PLA and after about 15 minutes of high-speed use, the flexible gear cracked. Printing out of other materials may give a longer life, but really, any 3D printed gears are not really suitable for high speed or extended use.