Cycloidal Gearbox

Project Overview

I needed a small form factor high reduction actuator for my custom robot dog in order to get the high torque I needed without it taking up a lot of space. A cycloidal gearbox was chosen due to its relative ease in manufacturing one and its extremely low backlash.

Design Overview

This cycloidal gearbox uses a printed hub and printed disks out of e-PA (Nylon) filament for a low friction interface. The input is driven by a large printed spline designed to interface with my dog and the output is a 6 hole set of heat set inserts to attach to.

The design is split into three main parts - the top, the bottom, and the disk assembly that is designed to come together with just 2 bolts. The top and bottom pieces utilize a 50mm ID x 65mm OD x 7mm WD radial bearing. Not only is it the biggest size I could fit for the largest output circle I could get, but it is also the same size bearing as all of the big bearings on the robot dog, making it easier to source parts for.

The disk setup itself is a printed eccentric shaft that locks the bearings for the disks on using a printed space on one end and an eclip on the other. Finally, it is brough together using metal shims and 5mm OD steel dowels to connect the input to the output.

Final Product

The gearbox has been assembled (and reassembled) many times in order to find the perfect fit, but the first gearbox has been installed into the prototype leg for the robot dog and is working fine.