115:1 3 stage planetary gearbox

thingiverse

Made as part of a group project from one of my classes. Each stage is ~4.8:1, it's recommended to use 1/8" steel rods for the axles and shafts and 1/8" square brass tubing was used for the square shafts. The output shaft was machined from brass but could be printed if desired. Each stage can be and was printed together. The torque at the last stage is a bit high so if possible it's recommended to replace the spider with a sheet metal one if you can. In the included pdf there is; a balooned exploded view to help with assembly, Dimensions for non printed internal shafts, sample input and output shafts with all dimensions necessary to design your own, and dimensions for all mounting holes. The gearbox was designed for use with 6-32 screws but could also use m3 or other similar sized threads. 4 bolts and 4 nuts are required to hold the stages together, and the backplate should be glued to the rear ring gear. There are 5 holes for mounting the gearbox, 2 at the front and 3 at the back. For the output shaft to stay in you will need to design a way to hold it in place if you don't mount a plate on the backplate and use the retaining ring to hold the shaft in. Due to the modular design it is possible to not use the middle stage for less of a reduction, or multiple middle stages for a higher reduction, however if using a total of 4 or more stages are used metal spiders will be required for all stages past the first 2-3 or else the square output hole will strip. I have not tested using a total of 5 stages but there may be a risk of gears skipping or jamming under the high loads.