# Tri-clamp membrane with a centre hole: 2 in, for a rod through the diaphragm

> How does a displacer rod pass through a diaphragm power piston?

- Category: Hardware › Stirling & thermoacoustic
- Kind: Hardware
- Basis: The 2 in membrane on this site (ISO 2852 Type B section for the clamped ring, 1.0 free span, 3 × Ø2.4 on Ø13) with a Ø5 centre hole; travel and stretch from the sealed generator's crank
- Page: https://xemstudio.com/objects/tri-clamp-through-rod-membrane/ · JSON: https://xemstudio.com/api/geometry?object=tri-clamp-through-rod-membrane · Plain text: https://xemstudio.com/objects/tri-clamp-through-rod-membrane/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

- The same membrane as the 2 in diaphragm membrane on this site: Type B bead 5.5 thick from the bore (Ø47.5) to the groove diameter (Ø56.5), web 1.7 out to Ø63, free span 1.0 thick, three Ø2.4 holes on Ø13. It adds a Ø5 hole in the centre, so a Ø3 rod passes through without touching it.
- Clamped between the crosshead hub (crankcase side) and the tapped backing disc (working side), the free span runs from Ø20 to Ø47.5 (13.75 mm). At ±6.0 mm travel it forms a 23.6° cone and stretches 9.1 %.
- On the sealed generator it carries only the difference between the working space and the crankcase: at most 0.60 bar in the Schmidt estimate at 2 bar gauge charge, about 0.47 bar at the ends of travel, a membrane force of about 1.4 N per mm at the disc edge there.
- The seal at the centre is the clamp between the two discs; the rod's own seal is the 15 mm guide bore in the crosshead hub above it.

## 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 |
|---|---|---|---|---|
| clamped ring | Type B section: bead 5.5 to Ø56.5, web 1.7 to Ø63 | ISO 2852 face recesses of the hot head and the cross | clamp | all |
| centre hole | Ø5 | Ø3 displacer rod (no contact) | designed | all |
| screw holes | 3 × Ø2.4 on Ø13 | M2 × 6 (ISO 273 medium clearance) | designed | all |

## Sizes

| size_in | od_mm | bead_to_mm | free_span_dia_mm | free_t_mm | centre_hole_mm | screw_circle_mm | travel_mm | stretch_pct |
|---|---|---|---|---|---|---|---|---|
| 2 | 63.0 | 56.5 | 47.5 | 1.0 | 5.0 | 13.0 | ±6.0 | 9.1 |

## Where the files are

- ISO (via iTeh sample): [ISO 2852 clamp liners: face profile and flange / groove diameters](https://cdn.standards.iteh.ai/samples/7850/eb49c396488d408c8ced3e2961d76cf3/ISO-2852-1974.pdf) — PDF — standard excerpt; dimensions are facts
- ASME: [BPE Bioprocessing Equipment (clamp fitting dimensions, tube OD and wall)](https://www.asme.org/codes-standards/find-codes-standards/bpe-bioprocessing-equipment) — standard — ASME; dimensions are facts (verify at link)
- 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/tri-clamp-through-rod-membrane/index.json

- membrane-2in-hole5: [STEP](https://xemstudio.com/files/hardware/tri-clamp-through-rod-membrane/membrane-2in-hole5.step) · [STL](https://xemstudio.com/files/hardware/tri-clamp-through-rod-membrane/membrane-2in-hole5.stl) — 2 in flat membrane with a Ø5 centre hole: Ø63 OD, Type B bead 5.5 thick from Ø47.5 to Ø56.5, web 1.7 out to the OD, free span Ø47.5 × 1.0, 3 × Ø2.4 on Ø13

## Questions

**Why a hole in the membrane?**

The displacer sits under the membrane in the same tube, so its rod has to come up through the membrane's centre to reach the crank.

**Does the hole leak?**

The hole is inside the clamped centre: the discs seal it. The only path for gas is along the rod in the crosshead's 15 mm guide bore.

## Fits with

- [Tri-clamp diaphragm membrane: flat, 1.5 and 2 in clamped size](https://xemstudio.com/objects/tri-clamp-diaphragm-membrane/)
- [Diaphragm crosshead hub and tapped backing disc: 2 in, with the displacer rod through the centre](https://xemstudio.com/objects/tri-clamp-diaphragm-crosshead/)
- [Tri-clamp cups: closed-end spools (ferrule on a capped tube), 1.5, 2 and 3 in](https://xemstudio.com/objects/tri-clamp-cups/)
- [Sanitary clamp crosses (9MP): ½ to 4 in](https://xemstudio.com/objects/sanitary-clamp-crosses/)
- [Build list: Tri-clamp sealed diaphragm generator, 2 in](https://xemstudio.com/objects/list-tri-clamp-sealed-diaphragm-generator/)