# 3 in end caps with a bored 608 bearing boss: shaft-seal version and blind version with three 1/4 NPT bosses

> How do I carry a crankshaft in a sealed tri-clamp crankcase?

- Category: Hardware › Stirling & thermoacoustic
- Kind: Hardware
- Basis: ISO 2852 3 in face (Ø91 flange, Ø83.5 groove); 608 and ISO 6194-1 8 × 22 × 7 sizes from their standards; 1/4 NPT per ASME B1.20.1
- Page: https://xemstudio.com/objects/tri-clamp-bearing-cap-3in/ · JSON: https://xemstudio.com/api/geometry?object=tri-clamp-bearing-cap-3in · Plain text: https://xemstudio.com/objects/tri-clamp-bearing-cap-3in/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

- Two 3 in end caps close the run of a 3 in tee (the crankcase) and carry the crankshaft in a 608 each. On the output side an 8 × 22 × 7 rotary shaft seal sits outboard of the bearing against the outer shoulder: the crankcase pressure pushes it onto the shoulder.
- The blind cap carries the crankcase's three 1/4 NPT ports: fill valve, gauge and relief valve.
- A plain lip seal is made for a small pressure difference; for a charged crankcase use a type its maker rates above the relief setting.

## 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 |
|---|---|---|---|---|
| face | ISO 2852 3 in (Ø91 flange, Ø83.5 groove) | Type B gasket, 3 in clamp | clamp | all |
| bearing bore | Ø22, 608 at z 21–28 | 608 bearing OD | press | all |
| seal bore | Ø22, z 28–35, outer shoulder Ø12 | 8 × 22 × 7 rotary shaft seal OD | press | bearing-cap-3in-608-seal* |
| port bosses | 3 × 1/4-18 NPT on r 27, tap drill Ø11.1 × 12 | fill valve, gauge, relief valve | designed | bearing-cap-3in-608-3x* |

## Sizes

| part | bore | ports |
|---|---|---|
| bearing-cap-3in-608-seal | Ø22 to 35: 608 + seal, Ø12 shoulder | — |
| bearing-cap-3in-608-3x-npt14 | Ø22 to 28: 608 | 3 × 1/4 NPT on r 27 |

## 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)
- ASME: [ASME B1.20.1 Pipe Threads, General Purpose, Inch (NPT): 1/4-18 major Ø13.72, tap drill 7/16 in (11.1), L2 10.2](https://www.asme.org/codes-standards/find-codes-standards/b1-20-1-pipe-threads-general-purpose-inch) — standard — ASME; dimensions are facts (verify at link)
- ISO: [ISO 6194-1 Rotary shaft lip-type seals: nominal dimensions (8 × 22 × 7 is a listed size)](https://www.iso.org/standard/41300.html) — standard — dimensions are facts (verify at link)
- Long Earth Society: [Engine builds](https://longearthsociety.com/engineering/) — web, video — LES site

## Free STEP/STL (2 parts, CC BY 4.0, Xem Studio)

Index: https://xemstudio.com/files/hardware/tri-clamp-bearing-cap-3in/index.json

- bearing-cap-3in-608-seal: [STEP](https://xemstudio.com/files/hardware/tri-clamp-bearing-cap-3in/bearing-cap-3in-608-seal.step) · [STL](https://xemstudio.com/files/hardware/tri-clamp-bearing-cap-3in/bearing-cap-3in-608-seal.stl) — 3 in bearing cap: ISO 2852 3 in face, body Ø76.2 to 14, boss Ø36 to 40, Ø22 bore to z 35 (608 at 21–28, 8 × 22 × 7 shaft seal at 28–35), Ø12 through the outer shoulder
- bearing-cap-3in-608-3x-npt14: [STEP](https://xemstudio.com/files/hardware/tri-clamp-bearing-cap-3in/bearing-cap-3in-608-3x-npt14.step) · [STL](https://xemstudio.com/files/hardware/tri-clamp-bearing-cap-3in/bearing-cap-3in-608-3x-npt14.stl) — 3 in bearing cap, blind: Ø22 bore to z 28 (608 at 21–28), three 1/4 NPT bosses on its back on r 27 (fill, gauge, relief)

## Questions

**Why 3 in?**

A 36 mm stroke crank and its con-rods need more than the 47.5 mm bore of a 2 in fitting; the 3 in tee's 72.9 mm bore clears them.

## Fits with

- [Rotary shaft lip seal 8 × 22 × 7 (envelope)](https://xemstudio.com/objects/rotary-shaft-seal-8x22x7/)
- [Built-up crank webs for Ø8 shafts and Ø6 crank pins (two-throw cranks at 90°)](https://xemstudio.com/objects/stirling-built-up-crank-webs/)
- [Build list: Tri-clamp charged beta, 2 in](https://xemstudio.com/objects/list-tri-clamp-charged-beta/)