Leg test stand — prototype build
An early prototype test stand for a single leg, with the full bill of materials.
This is the early prototype test stand used to bring up a single leg. It is documented here so it can be rebuilt from the parts list alone.
Stand
The stand is built around two 800 mm SBR20 linear rails with four SBR20UU blocks, which gives a vertical axis long enough to let the leg travel through a full stride without hitting a limit.
Actuators
Three quasi-direct-drive actuators drive the leg. Each is built around an 8110 stator, hand-wound, running on a Flipsky ODESC V4.2 controller in field-oriented control.
Actuator, as built
- Stator
- 8110
- Magnets
- 12x5x3 mm, N52, 42 per rotor
- Winding
- 26 AWG enamelled copper
- Controller
- Flipsky ODESC V4.2, 24 V
- Printed parts
- PETG, Bambu X1C
Rotors, planetary gears, the planet holder, stator lock, outer housing and ring gear, bearing retaining ring, and backplate are all printed. The magnet holders are laser-cut from 1.2 mm A36/1008 mild steel.1
Bill of materials
Everything needed to rebuild the stand and its three actuators. Filled circles are purchased; open circles are outstanding.
| Purchased | Vendor | Item | Qty | Unit | × |
|---|---|---|---|---|---|
| Purchased | Amazon | 2x SBR20-800mm w/ 4x SBR20UULinear slide & blocks for stand. Sourced by Will.CAD (GrabCAD) ↗ | 2 slides, 4 blocks | $42.64 | 1 |
| Purchased | Amazon | Flipsky ODESC V4.2 24V ControllerBLDC controller for FOC. Sourced by Will.CAD (GrabCAD) ↗ | 1 | $42.99 | 1 |
| Purchased | Amazon | Flipsky ODESC V4.2 24V ControllerBLDC controller for FOC. Sourced by Ryan. | 2 | $42.99 | 2 |
| Purchased | 3D Printed | Planetary gearsPrinted w/ X1C PETG | 3 | ||
| Purchased | 3D Printed | RotorPrinted w/ X1C PETG | |||
| Purchased | 3D Printed | OutputPrinted w/ X1C PETG | |||
| Purchased | 3D Printed | Planet holderPrinted w/ X1C PETG | |||
| Purchased | 3D Printed | Stator lockPrinted w/ X1C PETG | |||
| Purchased | 3D Printed | Outer housing and ring gearPrinted w/ X1C PETG | |||
| Purchased | 3D Printed | Bearing retaining ringPrinted w/ X1C PETG | |||
| Purchased | 3D Printed | BackplatePrinted w/ X1C PETG | |||
| Not purchased | SendCutSend | magnet holder planetary.dxfA36/1008 mild steel, .048" (1.2mm). Sourced by Ryan. | 9 x 3 = 27 | 27 | |
| Purchased | Amazon | 26 AWG enamelled copper wireSourced by Ryan. | 1 | $27.98 | 1 |
| Purchased | AliExpress | 8110 StatorSourced by Ryan. | 3 | $13.80 | 3 |
| Purchased | Amazon | 12x5x3 N52 magnets, 70 pcs.Must be 12x5x3 mm and N52. Sourced by Ryan. | 42 x 3 = 126 | $9.99 | 2 |
| Purchased | Amazon | uxcell 6709 bearing, 5 pcs.Sourced by Ryan.Datasheet (AST) ↗ | $11.29 | 1 | |
| Purchased | Amazon | uxcell 6707 bearing, 10 pcs.Sourced by Ryan.Datasheet (AST) ↗ | $28.09 | 1 | |
| Purchased | Amazon | uxcell 6702 bearing, 10 pcs.Sourced by Ryan.Datasheet (AST) ↗ | $9.29 | 1 | |
| Purchased | Amazon | MR117 bearingSourced by Ryan.CAD library (GrabCAD) ↗ | $7.99 | 1 | |
| Purchased | Amazon | M3x5x4 heat-set insertsSourced by Ryan. | $11.99 | 1 | |
| Purchased | Amazon | M2 screw kitSourced by Ryan. | $6.99 | 1 | |
| Purchased | Amazon | Silicone-based lubricantSourced by Ryan. | $9.99 | 1 | |
| Purchased | Amazon | 3mm x 18mm steel dowel pinsSourced by Ryan. | $9.99 | 1 | |
| Purchased | Amazon | Gorilla Glue Gel XLTo hold the diametric magnet. | $7.48 | 1 | |
| Not purchased | Amazon | JST-PH 2.0mm 2-pinFor reference motor CAN bus. | $5.99 | 1 | |
| Not purchased | Grainger | Gates timing belt, GT 392DD95MGT-700Product page ↗ | $43.56 | 1 | |
| Not purchased | Misumi | Tapped dowel pins, m6 tolerance | 2 | ||
| Not purchased | Misumi | Keyless bushing timing belt pulleyNFC alteration removes the bushing; keyless ones have screw mounts. | |||
| Not purchased | Amazon | Misc. belts for prototypingSourced by Will.Product page ↗ |
Quantities are sized for three motors. Printed parts were run on a Bambu X1C in PETG. Cost columns in the source spreadsheet were ambiguous, so only per-unit prices are reproduced.
Reproducing this
Every printed part and every purchased component is listed above, with vendor links and CAD models where they exist. If you build one and find a better part — particularly for the timing-belt drive, which is still open — open a pull request against this page.