The AIO version shown in these pictures mounts the control board in the front with cables routing to the motor in the back, based on a concept by @thearmpit. The AIO Cover part used here is a custom design not covered under CC BY-NC-SA 4.0 license.
What is a capstan drive?
A capstan drive uses rope and a pulley to transmit motion. For an excellent explanation of the mechanism, watch this video by Aaed Musa:Capstan Drive Explained
Learn how capstan drives work and why they’re effective for high-torque applications.
Why choose capstan over belt?
The standard belt-driven OSSM can experience slipping at higher torques. While this may result from build errors, the capstan drive eliminates this issue entirely.Comparison to standard OSSM
- Advantages
- Disadvantages
- Same form factor as standard OSSM
- Equal or quieter operation
- Only 13cm effective rail length loss (450mm rail = 32cm stroke)
- 2.7x stronger (32kg vs 12kg capacity)
- Same maximum speed
- No belt slipping
- No custom PCBs required
- PitClamp compatible
- Compatible with all custom end effectors
MGN12H vs HG20
There are two rail variants for this build. The HG20 version is recommended if your budget allows.- HG20 (Recommended)
- MGN12H
MGN12H rails and carriages reach their limits with 30cm+ cantilevers combined with heavy toys (~1.5kg and up). This results in louder operation, bearing wear over time, and deflection issues.The HG20 version addresses all of these and includes additional improvements such as a bigger drum and better rope guiding for smoother operation.Additional cost: ~40€ more than the MGN12H version.
Configuration options
AIO vs normal version
- AIO (Recommended)
- Normal
The AIO mod version mounts the control board in the front of the motor head with integrated cable routing. This is the recommended configuration.
Pulley versions
- Bushing Pulley (Recommended)
- 3D Printed Pulley
The bushing pulley is superior in every way:
- Better durability
- No deformation over time
- Supports rail lengths up to 450mm (500mm likely possible)
Supported rail lengths
| Pulley Type | Tested Length | Maximum Recommended |
|---|---|---|
| Bushing | 450mm | 500mm (untested) |
| 3D Printed | 400mm | 400mm |
Rope selection
Required rope: Liros DC pro 161 (or equivalent Dyneema DM20, SK99, SK75 with max 1mm diameter)Why rope selection matters
Why rope selection matters
The rope must have minimal stretch under load. Testing by community member @neos demonstrated that generic UHMWPE rope from AliExpress stretches excessively and breaks under load. The specified Dyneema rope maintains consistent tension for reliable operation.
Alternative rope specifications
Alternative rope specifications
If you cannot source Liros DC pro 161, look for:
- Material: Dyneema DM20, SK99, or SK75
- Maximum diameter: 1mm
- Verified low-stretch construction
Print settings
Pre-configured .3mf files are included for most parts with optimal settings.
| Setting | Value |
|---|---|
| Walls | 6 |
| Infill | 20% |
| Supports | Try without for AIO_cover (bridges only); enable if needed |
Bill of materials
- HG20 (~380€)
- MGN12H (~345€)
| Part | Estimated Cost | Source |
|---|---|---|
| 60AIM40F Motor | ~110€ | Superbuy/Taobao |
| OSSM Control Board + Remote | $91 USD (excl. tax/shipping) | Research and Desire |
| MR115 Bearings (4x) | ~3€ | AliExpress |
| Hardware kit | ~30€ | See fastener list below |
| PLA Filament (1kg) | ~8€/kg | AliExpress |
| Liros DC pro 161 Rope (5m) | ~15€ | Kite Line Shop |
| Bushing 20x24x40mm (id x od x l) | ~5€ | AliExpress |
| HG20 Linear Rail + HGH20HA Carriage | ~50€ (depending on length) | AliExpress (400/500mm) |
| Epoxy Glue | ~3€ | AliExpress |
| 4-pin JST Header Cable (30cm) | ~2€ | AliExpress |
| 2-pin AWG 18+ Wire (30cm) | ~2€ | AliExpress |
| Shrink tube (24mm ID) or Kinesio Tape | ~3€ | AliExpress or local drug store |
| 36V 5+A Power Supply | ~68€ | Voelkner (PSU) + Adapter |
| Total | ~380€ |
HG20 fastener list
HG20 fastener list
| Fastener | Quantity |
|---|---|
| M4x12 ISO7380 | 4 |
| M5x45 Countersunk | 2 |
| M5x75 Countersunk | 4 |
| M5x20 Hex Cap | 4 |
| M5x25 Hex Cap | 2 |
| M5x30 Hex Cap | 3 |
| M5x65 Hex Cap | 4 |
| M5x110 Hex Cap (fully threaded) | 1 |
| M5 Nuts | 11 |
| M4 Nuts | 4 |
The M5x110 fully threaded hex cap can be sourced from AliExpress.
Assembly guides
Detailed step-by-step assembly guides are available as PDFs:HG20 Assembly Guide
PDF assembly instructions for the HG20 variant.
MGN12H Assembly Guide
PDF assembly instructions for the MGN12H variant.
Printed parts and CAD files
All printable files and STEP sources are hosted on GitHub. Pre-configured .3mf files include recommended slicer settings.- HG20
- MGN12H
Printable parts (STL/3MF):
STEP source files:
| Part | Files |
|---|---|
| Capstan Drum | 3MF / Upper STL / Lower STL |
| Motor Head Front | 3MF / STL |
| Motor Head Back | 3MF / STL |
| Motor Head Cover | 3MF / STL |
| End Effector | 3MF / STL |
| Pulleys | 3MF / End Effector STL / Rail End STL |
| Rail End | 3MF / STL |
| Tensioner | 3MF / Upper STL / Lower STL |
| Standoffs | STL 1 / STL 2 / STL 3 |
| PitClamp Motor Ring (60AIM40F) | STL |
| Part | STEP |
|---|---|
| Motor Head | MotorHead_60AIM40F_HGR.step |
| Capstan Drum | CapstanDrum.step |
| End Effector | EndEffector.step |
| End Pulley | EndPulley.step |
| Rail End | RailEnd.step |
| Tensioner | 60AIMTensioner_HGR.step |
| Bushing Pulley (Fusion 360) | BushingPulley60AIM_HGR.f3d |
Community support
Special thanks to everyone who provided suggestions and helped overcome challenges during development!