# Walking beam for a tri-clamp beam engine (arms 158.07 / 131.73)

> How do I build a walking beam for a vertical power cylinder?

- Category: Hardware › Stirling & thermoacoustic
- Kind: Hardware
- Basis: Design values; 625 and dowel sizes from their standards
- Page: https://xemstudio.com/objects/stirling-walking-beam/ · JSON: https://xemstudio.com/api/geometry?object=stirling-walking-beam · Plain text: https://xemstudio.com/objects/stirling-walking-beam/sheet.txt
- License: dimension sheet CC BY 4.0 (Xem Studio); linked files under their publishers' licenses
- Use in every chat: add https://xemstudio.com/mcp as a connector (https://xemstudio.com/use-with-ai/)

**Exact dimensions.** Every file is drawn at true size with no printing tolerance. The holes and pins that meet another part are listed below under Mating features, with the fit each joint needs; open those by your printer's or process's clearance before making the part.

## Notes

- A T-shaped beam on two 625 bearings on a Ø5 pivot pin in the post's cheeks. Arm A (158.62) carries a Ø6 pin for the 60 mm link from the piston rod's crosshead; arm B (132.18) a Ø5 pin for the 488.4 mm link down to the crank. The arm ratio 1.2 turns the crank's 30 mm throw into the piston's 36 mm stroke.

## Mating features (exact size; open press / slide / run / socket by your process clearance, leave designed and clamp as drawn)

| feature | exact | mates with | fit | files |
|---|---|---|---|---|
| pivot bore | Ø16 × 10 | two 625 bearings | press | all |
| end A hole | Ø6 | Ø6 dowel pin (link A) | press | all |
| end B hole | Ø5 | Ø5 dowel pin (link B) | press | all |

## Sizes

| feature | value |
|---|---|
| arm A | 158.62 |
| arm B | 132.18 |
| pivot | Ø16 bore, two 625 |
| swing | ±6.5° |

## Where the files are

- Long Earth Society: [Engine builds](https://longearthsociety.com/engineering/) — web, video — LES site

## Free STEP/STL (1 parts, CC BY 4.0, Xem Studio)

Index: https://xemstudio.com/files/hardware/stirling-walking-beam/index.json

- walking-beam-158.07-131.73: [STEP](https://xemstudio.com/files/hardware/stirling-walking-beam/walking-beam-158.07-131.73.step) · [STL](https://xemstudio.com/files/hardware/stirling-walking-beam/walking-beam-158.07-131.73.stl) — walking beam 10 thick: pivot boss Ø30 with an Ø16 bore (two 625), end A Ø6 press hole 158.62 from the pivot, end B Ø5 press hole 132.18 from it, bar 16 high, stem to 40 below the pivot

## Questions

**Why a beam?**

It is the classic desk layout: the power cylinder stands up from the middle of the displacer cylinder and the beam brings its motion to the same crank as the displacer.

## Fits with

- [Build list: Tri-clamp walking-beam gamma generator, 2 in, chargeable](https://xemstudio.com/objects/list-tri-clamp-walking-beam-gamma/)