Cycloidal Gearbox Design (WIP)

Personal Project

June 2026 - Present

Introduction

In order to better understand drive mechanisms used in robotics, I decided to design a cycloidal gearbox from scratch. The goal of the cycloidal gearbox was to be fully manufactured with a 3D printer, bearings, and basic fasteners. The success of the project is determined by:

Accuracy of gear reduction ratio is 12:1 +/- 0.5 turns
Backlash is <2 degrees with a fixed load
Record to 1 degree of precision
Maintain accuracy with no damage due to fatigue and creep

Design Parameters

Hand Calculations

Desmos Mapping

I started out by determining key parameters and determining required values. My plan was to use the 7x19x6 bearing that I purchased previously for another project as my roller pins. Thus, the pin radius was set at 9.5 mm. I targeted a reduction ratio of 11:1, which forced the number of rollers to be 12. In order to meet the accuracy and backlash requirements, I decided on a dual-drive cycloidal drive such that the load is balanced amongst the two disks. I also utilized Desmos to determine the shape of the cycloid disk and understand how it worked. (https://www.desmos.com/calculator/eqcjxzrkjv)

CAD

I created a rough CAD of the cycloidal drive without fasteners and bearings to verify my geometry from the calculations would work. The cycloidal drive was drawn from an equation-driven curve that has been parameterized. (https://blog-assets.solidworks.com/uploads/2025/12/building-a-cycloidal-drive-with-solidworks.pdf) I then ran a motion study to detect interference or failures.

Motion Analysis Result

Cycloid Disk Sketch

For a more robust design, I included the bearings for the roller pins and also included them for the output drive shaft. Any surface where different parts contacted was fitted with bearings to minimize friction between components. I then created holes to use heat-set inserts and M3 screws as primary fasteners.