# Can-engine diaphragm: membrane, clamp rings and centre disc, Ø40 / 50 / 60

> What are the dimensions of the diaphragm clamp rings for a can Stirling engine?

- Category: Stirling engines › Can & LTD engines
- Kind: Standard part
- Basis: Ring bore = diaphragm working diameter; centre disc at half the bore; 6 × M3 clearance (ISO 273) on the ring
- Page: https://xemstudio.com/objects/can-engine-diaphragm/ · JSON: https://xemstudio.com/api/geometry?object=can-engine-diaphragm · Plain text: https://xemstudio.com/objects/can-engine-diaphragm/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 diaphragm power piston of the can engine: a 0.2 mm membrane clamped round its edge between two identical rings, with a stiff centre disc the con-rod screws to.
- Rings come in Ø40, Ø50 and Ø60 bores, each 3 thick with an outside of bore + 16 (Ø56 / 66 / 76) and 6 × Ø3.4 holes on a bore + 8 circle (Ø48 / 58 / 68).
- Each ring size has its own centre disc at half the bore: Ø20, Ø25 or Ø30 × 2 with a Ø3.2 hole for the M3 con-rod screw.
- Each membrane is the rings' outside diameter (Ø56 / 66 / 76) × 0.2 with the same six Ø3.4 holes and a Ø3.2 centre hole; its free span is the ring bore. One membrane, two rings and one disc of the same size make one diaphragm.

## 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 |
|---|---|---|---|---|
| clamp-ring screw holes | Ø3.4 | M3 screw clearance | designed | diaphragm-ring-* |
| centre-disc screw hole | Ø3.2 | M3 screw clearance (ISO 273 fine) | designed | diaphragm-disc-* |

## Sizes

| size | ring bore | ring outside | screw circle | ring thickness | disc | disc hole |
|---|---|---|---|---|---|---|
| 40 | 40 | 56 | 48 | 3 | Ø20 × 2 | 3.2 |
| 50 | 50 | 66 | 58 | 3 | Ø25 × 2 | 3.2 |
| 60 | 60 | 76 | 68 | 3 | Ø30 × 2 | 3.2 |

## Where the files are

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

## Free STEP/STL (9 parts, CC BY 4.0, Xem Studio)

Index: https://xemstudio.com/files/hardware/can-engine-diaphragm/index.json

- diaphragm-ring-40: [STEP](https://xemstudio.com/files/hardware/can-engine-printed-kit/diaphragm-ring-40.step) · [STL](https://xemstudio.com/files/hardware/can-engine-printed-kit/diaphragm-ring-40.stl) — diaphragm clamp ring Ø40 bore × Ø56, 3 thick, 6 × Ø3.4 (M3 clearance); two per diaphragm, one each side of the membrane
- diaphragm-disc-20: [STEP](https://xemstudio.com/files/hardware/can-engine-printed-kit/diaphragm-disc-20.step) · [STL](https://xemstudio.com/files/hardware/can-engine-printed-kit/diaphragm-disc-20.stl) — diaphragm centre disc Ø20 × 2, Ø3.2 M3 clearance hole for the con-rod screw
- diaphragm-membrane-40: [STEP](https://xemstudio.com/files/hardware/can-engine-printed-kit/diaphragm-membrane-40.step) · [STL](https://xemstudio.com/files/hardware/can-engine-printed-kit/diaphragm-membrane-40.stl) — diaphragm membrane Ø56 × 0.2 with the rings' 6 × Ø3.4 holes and a Ø3.2 centre hole; free span Ø40 between the rings
- diaphragm-ring-50: [STEP](https://xemstudio.com/files/hardware/can-engine-printed-kit/diaphragm-ring-50.step) · [STL](https://xemstudio.com/files/hardware/can-engine-printed-kit/diaphragm-ring-50.stl) — diaphragm clamp ring Ø50 bore × Ø66, 3 thick, 6 × Ø3.4 (M3 clearance); two per diaphragm, one each side of the membrane
- diaphragm-disc-25: [STEP](https://xemstudio.com/files/hardware/can-engine-printed-kit/diaphragm-disc-25.step) · [STL](https://xemstudio.com/files/hardware/can-engine-printed-kit/diaphragm-disc-25.stl) — diaphragm centre disc Ø25 × 2, Ø3.2 M3 clearance hole for the con-rod screw
- diaphragm-membrane-50: [STEP](https://xemstudio.com/files/hardware/can-engine-printed-kit/diaphragm-membrane-50.step) · [STL](https://xemstudio.com/files/hardware/can-engine-printed-kit/diaphragm-membrane-50.stl) — diaphragm membrane Ø66 × 0.2 with the rings' 6 × Ø3.4 holes and a Ø3.2 centre hole; free span Ø50 between the rings
- diaphragm-ring-60: [STEP](https://xemstudio.com/files/hardware/can-engine-printed-kit/diaphragm-ring-60.step) · [STL](https://xemstudio.com/files/hardware/can-engine-printed-kit/diaphragm-ring-60.stl) — diaphragm clamp ring Ø60 bore × Ø76, 3 thick, 6 × Ø3.4 (M3 clearance); two per diaphragm, one each side of the membrane
- diaphragm-disc-30: [STEP](https://xemstudio.com/files/hardware/can-engine-printed-kit/diaphragm-disc-30.step) · [STL](https://xemstudio.com/files/hardware/can-engine-printed-kit/diaphragm-disc-30.stl) — diaphragm centre disc Ø30 × 2, Ø3.2 M3 clearance hole for the con-rod screw
- diaphragm-membrane-60: [STEP](https://xemstudio.com/files/hardware/can-engine-printed-kit/diaphragm-membrane-60.step) · [STL](https://xemstudio.com/files/hardware/can-engine-printed-kit/diaphragm-membrane-60.stl) — diaphragm membrane Ø76 × 0.2 with the rings' 6 × Ø3.4 holes and a Ø3.2 centre hole; free span Ø60 between the rings

## How it fits

### Connects to
- [Con-rods with Ø3 pin ends, 45 and 60 mm, 8 × 5](https://xemstudio.com/objects/pin-end-con-rods/): con-rod screwed to the centre disc's Ø3.2 hole

### Alternatives
- [Syringe cradle for 10, 20 and 60 mL barrels](https://xemstudio.com/objects/syringe-cradle/): a syringe as the power piston instead

### Also needed
- [Socket head cap screws, M2–M8 (ISO 4762 / DIN 912)](https://xemstudio.com/objects/socket-head-cap-screws-metric/): 6 × M3 through the rings, 1 × M3 in the disc

## Questions

**Which centre disc goes with which ring?**

Half the ring bore: Ø20 disc with the Ø40 rings, Ø25 with Ø50, Ø30 with Ø60.

**How are the diaphragm rings fastened?**

Six M3 screws through Ø3.4 holes on a circle 8 mm larger than the bore (Ø58 on the 50 mm ring), through both rings and the membrane.

**Which size does the can engine use?**

The can-engine build list uses the Ø50 rings with the Ø25 disc.

## Fits with

- [Can-engine cap for 53.3, 58, 66 and 76.2 mm cans](https://xemstudio.com/objects/can-engine-cap/)
- [Con-rods with Ø3 pin ends, 45 and 60 mm, 8 × 5](https://xemstudio.com/objects/pin-end-con-rods/)
- [Build list: Soda-can gamma](https://xemstudio.com/objects/list-can-engine/)
- [Syringe cradle for 10, 20 and 60 mL barrels](https://xemstudio.com/objects/syringe-cradle/)