# Tri-clamp crank frame: ISO 2852 cap with 608 towers for a Ø8 crankshaft, 1.5, 2 and 3 in

> How do I mount a crankshaft on a tri-clamp spool?

- Category: Stirling engines › Tri-clamp engine parts
- Kind: Hardware
- Basis: ISO 2852 cap face; pedestal Ø = tube OD to clear the clamp; two 8 mm towers with Ø22 608 pockets, 21 mm apart, crank axis 32 / 34 / 40 mm above the face
- Page: https://xemstudio.com/objects/tri-clamp-crank-frame/ · JSON: https://xemstudio.com/api/geometry?object=tri-clamp-crank-frame · Plain text: https://xemstudio.com/objects/tri-clamp-crank-frame/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

- A crank frame that clamps onto the open ferrule of a spool with a stock clamp and gasket, and holds a Ø8 crankshaft in two 608 bearings above it.
- Base: the 6 mm ISO 2852 cap, a pedestal the tube's OD (38.1 / 50.8 / 76.2) up to 14 mm so the clamp clears, and a Ø C3 plate 4 mm thick on top. A con-rod window Ø21 / Ø28 / Ø44 runs through the centre.
- Two towers 8 mm thick with rounded tops stand 21 mm apart; each has a Ø22 × 7 pocket for a 608 from the outside face, and the shaft hole between is Ø9.2 so the Ø8 shaft touches only the bearings.
- Crank axis 32 / 34 / 40 mm above the face for 1.5 / 2 / 3 in; overall height 47.7 / 54 / 60 mm.

## 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 |
|---|---|---|---|---|
| crank-frame bearing pockets | Ø22 | 608 bearing | press | crank-frame-* |
| crank-frame face | ISO 2852 | tri-clamp ferrule face + Type B gasket | clamp | crank-frame-* |
| crank-frame shaft clearance | Ø9.2 | Ø8 shaft (no contact; the 608s carry it) | designed | crank-frame-* |

## Sizes

| spool_in | flange_od_mm | window_mm | crank_axis_mm | tower_gap_mm | bearing | overall_h_mm |
|---|---|---|---|---|---|---|
| 1.5 | 50.5 | 21 | 32 | 21 | 608 (Ø22) | 47.7 |
| 2 | 64.0 | 28 | 34 | 21 | 608 (Ø22) | 54.0 |
| 3 | 91.0 | 44 | 40 | 21 | 608 (Ø22) | 60.0 |

## Where the files are

- Long Earth Society: [Tri-clamp Stirling engine builds](https://longearthsociety.com/engineering/) — web, video — LES site
- James R. Senft: [An Introduction to Stirling Engines (piston fit and leakage)](https://www.stirlingengine.com/) — book — Moriya Press (verify at link)
- ASME: [BPE tube dimensions (16 ga sanitary tube)](https://www.asme.org/codes-standards/find-codes-standards/bpe-bioprocessing-equipment) — standard — ASME (verify at link)

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

Index: https://xemstudio.com/files/hardware/tri-clamp-crank-frame/index.json

- crank-frame-1.5in: [STEP](https://xemstudio.com/files/hardware/tri-clamp-power-pistons/crank-frame-1.5in.step) · [STL](https://xemstudio.com/files/hardware/tri-clamp-power-pistons/crank-frame-1.5in.stl) — 1.5 in crank frame: ISO 2852 cap face (clamps to the spool with a stock clamp), Ø21 con-rod window, two towers with 608 pockets for a Ø8 crankshaft 32 mm above the face, 21 mm between towers
- crank-frame-2in: [STEP](https://xemstudio.com/files/hardware/tri-clamp-power-pistons/crank-frame-2in.step) · [STL](https://xemstudio.com/files/hardware/tri-clamp-power-pistons/crank-frame-2in.stl) — 2 in crank frame: ISO 2852 cap face (clamps to the spool with a stock clamp), Ø28 con-rod window, two towers with 608 pockets for a Ø8 crankshaft 34 mm above the face, 21 mm between towers
- crank-frame-3in: [STEP](https://xemstudio.com/files/hardware/tri-clamp-power-pistons/crank-frame-3in.step) · [STL](https://xemstudio.com/files/hardware/tri-clamp-power-pistons/crank-frame-3in.stl) — 3 in crank frame: ISO 2852 cap face (clamps to the spool with a stock clamp), Ø44 con-rod window, two towers with 608 pockets for a Ø8 crankshaft 40 mm above the face, 21 mm between towers

## How it fits

### Goes in or on
- [Tri-clamp spool (two ferrules on a tube), 1.5 and 2 inch](https://xemstudio.com/objects/tri-clamp-spool/): ISO 2852 face on the open ferrule

### Connects to
- [608 ball bearing](https://xemstudio.com/objects/608-bearing/): 608 in each Ø22 × 7 pocket
- [Tri-clamp crank web: Ø8 bore, Ø3 crank pin at 8, 12 and 18 mm throw](https://xemstudio.com/objects/tri-clamp-crank-web/): two webs on the Ø8 shaft between the towers

### Also needed
- [Metric shafts Ø3 to Ø10 with D-flats and clip grooves](https://xemstudio.com/objects/metric-shafts/): Ø8 shaft and collar
- [Tri-clamp clamp, two-bolt: every flange size ½ to 4 in](https://xemstudio.com/objects/tri-clamp-clamps/): clamp and gasket on the face
- [Flywheels Ø100–Ø200 with hex-nut rim pockets](https://xemstudio.com/objects/nut-pocket-flywheels/): Ø8-hub flywheel outside a tower

## Questions

**How do I put a crankshaft on a tri-clamp cylinder?**

Clamp the crank frame to the open ferrule; a Ø8 shaft runs in two 608s in its towers, 34 mm above the face on the 2 in frame.

**How wide is the gap between the crank-frame towers?**

21 mm: crank web, con-rod, crank web (5 mm each) with 1 mm gaps.

**Does the shaft touch the frame?**

No: the shaft hole is Ø9.2; the Ø8 shaft runs only in the 608s.

## Fits with

- [Tri-clamp crank web: Ø8 bore, Ø3 crank pin at 8, 12 and 18 mm throw](https://xemstudio.com/objects/tri-clamp-crank-web/)
- [Tri-clamp con-rod: 58, 70 and 95 mm centres with 623 pockets](https://xemstudio.com/objects/tri-clamp-con-rod/)
- [Tri-clamp power piston: ring-less full-bore pistons Ø34.8, Ø47.5 and Ø72.9](https://xemstudio.com/objects/tri-clamp-power-piston/)
- [608 ball bearing](https://xemstudio.com/objects/608-bearing/)
- [Metric shafts Ø3 to Ø10 with D-flats and clip grooves](https://xemstudio.com/objects/metric-shafts/)
- [Tri-clamp clamp, two-bolt: every flange size ½ to 4 in](https://xemstudio.com/objects/tri-clamp-clamps/)