3D renderFive ratios · 3D renders of the generated CAD; colours are illustrative.
Mechanism pack / HS-MEC-002 / coming soon
Cycloid Drive Ratio Pack
Our cycloid drive in five more ratios for a NEMA17: 11, 15, 20, 30 and 40:1. Same bearings, pins and fits as the free 25:1.
Coming soonDigital 3D print files
Start with the free 25:1 Not on sale yet. Follow @harryson.stl for the launch.
Ratios11–40:1
HousingØ85 / Ø90
InputNEMA17
Digitally verified, not yet printed. Only the free 25:1 has been printed and bench-tested; these ratios come from the same design engine, parts and fits. You print the parts and buy the bearings, dowel pins, screws and motor.
01 / The ratios
Pick your speed.
Pins = ratio + 1. Output speed is the 560 rpm motor limit we measured on the 25:1 bench, divided by the ratio.
| Ratio | Ring pins | Discs | Housing | Output speed |
|---|---|---|---|---|
| 11:1 | 12 | 2 identical | Ø85 mm | ≈ 51 rpm |
| 15:1 | 16 | 2 identical | Ø85 mm | ≈ 37 rpm |
| 20:1 | 21 | matched A + B | Ø85 mm | ≈ 28 rpm |
| 30:1 | 31 | matched A + B | Ø85 mm | ≈ 19 rpm |
| 40:1 | 41 | matched A + B | Ø90 mm | ≈ 14 rpm |
02 / Digital checks
What we checked.
- Disc-to-pin clearance 0.100 mm at 72 cam angles over a full turn, every ratio
- Ten wall-thickness checks per ratio, all at least 1.3 mm
- Every STL watertight, one solid, flat on the bed; a clean, support-free reference slice
- The same engine rebuilds the printed 25:1 parts to within 0.11% of their volume
- Not printed yet: only the free 25:1 has been printed and bench-tested
03 / The download
What’s in the pack.
- Five gearboxes: print-ready STLs, STEP files of every part and the assembly, and a mount drawing (DXF) for each
- An 18-piece fit test for every press and slide fit
- An 18-page guide: choosing a ratio, BOM per ratio, print settings, assembly, wiring, troubleshooting
- A no-library ESP32 / Arduino test sketch for a TMC2209 driver
- BOM.csv with quantities per ratio
The parts we use are listed at harbeworks.com/parts.
Build the tested one first.
The 25:1 is free: same bearings, pins and fit test.