# Rocker beam 60 / 80 / 100 mm on a 623 pivot

> What are the dimensions of a rocker beam for a beam-driven Stirling engine?

- Category: Stirling engines › Drives & mechanisms
- Kind: Hardware
- Basis: Centre pivot on a 623 bearing (Ø10 pocket, fit: press); Ø3 end holes (fit: run) at ±L/2
- Page: https://xemstudio.com/objects/rocker-beam/ · JSON: https://xemstudio.com/api/geometry?object=rocker-beam · Plain text: https://xemstudio.com/objects/rocker-beam/sheet.txt
- License: dimension sheet CC BY 4.0 (Xem Studio); linked files under their publishers' licenses

**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

- The walking beam of a beam-driven gamma: one end to the crank's con-rod, the other to the displacer rod, pivoting in the middle.
- A 12 wide × 6 thick bar L + 12 long (72 / 92 / 112) with Ø3 holes at ±L/2 (fit: run) and a Ø10 pocket on centre for a 623 bearing (fit: press).
- With equal arms the ratio is 1:1: the displacer stroke equals the crank 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 |
|---|---|---|---|---|
| rocker-beam pivot pocket | Ø10 | 623 bearing | press | rocker-beam-* |
| rocker-beam ends | Ø3 | Ø3 pins (turn on them) | run | rocker-beam-* |

## Sizes

| file | pin centres | length | section | pivot | end holes |
|---|---|---|---|---|---|
| rocker-beam-60 | 60 | 72 | 12 × 6 | Ø10 (623) | Ø3 |
| rocker-beam-80 | 80 | 92 | 12 × 6 | Ø10 (623) | Ø3 |
| rocker-beam-100 | 100 | 112 | 12 × 6 | Ø10 (623) | Ø3 |

## Where the files are

- Wikipedia: [Beam engine](https://en.wikipedia.org/wiki/Beam_engine) — web — CC BY-SA 4.0 (text)
- Wikipedia: [Stirling engine](https://en.wikipedia.org/wiki/Stirling_engine) — web — CC BY-SA 4.0 (text)
- Long Earth Society: [Engine builds](https://longearthsociety.com/engineering/) — web, video — LES site

## Free STEP/STL (3 parts, CC BY 4.0, Xem Studio)

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

- rocker-beam-60: [STEP](https://xemstudio.com/files/hardware/gamma-base-plate-and-beam/rocker-beam-60.step) · [STL](https://xemstudio.com/files/hardware/gamma-base-plate-and-beam/rocker-beam-60.stl) — rocker beam 60 mm, centre pivot on a 623 (Ø10 pocket), Ø3 ends (beam-driven displacer)
- rocker-beam-80: [STEP](https://xemstudio.com/files/hardware/gamma-base-plate-and-beam/rocker-beam-80.step) · [STL](https://xemstudio.com/files/hardware/gamma-base-plate-and-beam/rocker-beam-80.stl) — rocker beam 80 mm, centre pivot on a 623 (Ø10 pocket), Ø3 ends (beam-driven displacer)
- rocker-beam-100: [STEP](https://xemstudio.com/files/hardware/gamma-base-plate-and-beam/rocker-beam-100.step) · [STL](https://xemstudio.com/files/hardware/gamma-base-plate-and-beam/rocker-beam-100.stl) — rocker beam 100 mm, centre pivot on a 623 (Ø10 pocket), Ø3 ends (beam-driven displacer)

## How it fits

### Goes in or on
- [Beam pivot post, 60 mm](https://xemstudio.com/objects/beam-pivot-post/): 623 on the post's Ø3 pin
- [Ball bearings, 683 to 6210 and flanged F6xx (ISO 15)](https://xemstudio.com/objects/ball-bearings-metric/): 623 in the Ø10 pocket

### Connects to
- [Crank discs for a Ø5 shaft, 10 to 30 mm stroke](https://xemstudio.com/objects/crank-discs-5mm-bore/): con-rod on one Ø3 end
- [Rod clevises for a Ø2 or Ø3 rod or a Ø5 tube, 5 mm gap](https://xemstudio.com/objects/rod-clevises/): rod clevis on the other end

### Also needed
- [Dowel pins, 2–6 mm (ISO 2338 / DIN 6325)](https://xemstudio.com/objects/dowel-pins-metric/): Ø3 pins

## Questions

**What is a beam-driven Stirling engine?**

The crank drives a rocker beam whose far end moves the displacer, so the crank can sit beside the cylinder.

**What bearing goes in the rocker beam?**

A 623 (3 × 10 × 4) in the centre pocket, on the pivot post's Ø3 pin.

## Fits with

- [Beam pivot post, 60 mm](https://xemstudio.com/objects/beam-pivot-post/)
- [Base plate for 1.5, 2 and 3 in tri-clamp Stirling engines](https://xemstudio.com/objects/tri-clamp-engine-base-plate/)
- [Ball bearings, 683 to 6210 and flanged F6xx (ISO 15)](https://xemstudio.com/objects/ball-bearings-metric/)
- [Crank discs for a Ø5 shaft, 10 to 30 mm stroke](https://xemstudio.com/objects/crank-discs-5mm-bore/)