# Tri-clamp crank web: Ø8 bore, Ø3 crank pin at 8, 12 and 18 mm throw

> What crank web gives a 24 mm stroke on an 8 mm shaft?

- Category: Stirling engines › Tri-clamp engine parts
- Kind: Hardware
- Basis: Stroke 16 / 24 / 36 mm (0.46 × bore) for the 1.5 / 2 / 3 in pistons; web Ø = 2 × (throw + 6)
- Page: https://xemstudio.com/objects/tri-clamp-crank-web/ · JSON: https://xemstudio.com/api/geometry?object=tri-clamp-crank-web · Plain text: https://xemstudio.com/objects/tri-clamp-crank-web/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 round crank web: Ø8 shaft bore, Ø3 crank-pin hole at half the stroke, and an Ø2.5 radial hole for an M3 grub onto the shaft. Two webs face each other with the pin between them.
- 1.5 in: Ø28, pin at 8 mm (16 mm stroke). 2 in: Ø36, pin at 12 mm (24 mm stroke). 3 in: Ø48, pin at 18 mm (36 mm stroke). All 5 mm thick.
- Shaft order: tower, web, con-rod, web, tower with 1 mm gaps, inside the crank frame's 21 mm tower gap; the crank pin between the webs is Ø3 × 19.

## 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-web shaft bore | Ø8 | Ø8 D-flat crankshaft | slide | crank-web-* |
| crank-web pin hole | Ø3 | Ø3 crank pin | press | crank-web-* |
| crank-web grub hole | Ø2.5 | M3 tap drill | designed | crank-web-* |

## Sizes

| spool_in | web_od_mm | shaft_bore_mm | pin_hole_mm | throw_mm | stroke_mm | thickness_mm |
|---|---|---|---|---|---|---|
| 1.5 | 28 | 8 | 3 | 8 | 16 | 5 |
| 2 | 36 | 8 | 3 | 12 | 24 | 5 |
| 3 | 48 | 8 | 3 | 18 | 36 | 5 |

## 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-web/index.json

- crank-web-1.5in-s16: [STEP](https://xemstudio.com/files/hardware/tri-clamp-power-pistons/crank-web-1.5in-s16.step) · [STL](https://xemstudio.com/files/hardware/tri-clamp-power-pistons/crank-web-1.5in-s16.stl) — 1.5 in crank web: Ø8 bore on the D-flat shaft with an M3 tapped grub hole, Ø3 pin at 8 mm (16 mm stroke); two per crank
- crank-web-2in-s24: [STEP](https://xemstudio.com/files/hardware/tri-clamp-power-pistons/crank-web-2in-s24.step) · [STL](https://xemstudio.com/files/hardware/tri-clamp-power-pistons/crank-web-2in-s24.stl) — 2 in crank web: Ø8 bore on the D-flat shaft with an M3 tapped grub hole, Ø3 pin at 12 mm (24 mm stroke); two per crank
- crank-web-3in-s36: [STEP](https://xemstudio.com/files/hardware/tri-clamp-power-pistons/crank-web-3in-s36.step) · [STL](https://xemstudio.com/files/hardware/tri-clamp-power-pistons/crank-web-3in-s36.stl) — 3 in crank web: Ø8 bore on the D-flat shaft with an M3 tapped grub hole, Ø3 pin at 18 mm (36 mm stroke); two per crank

## How it fits

### Goes in or on
- [Tri-clamp crank frame: ISO 2852 cap with 608 towers for a Ø8 crankshaft, 1.5, 2 and 3 in](https://xemstudio.com/objects/tri-clamp-crank-frame/): two webs between the towers on the Ø8 shaft

### Connects to
- [Tri-clamp con-rod: 58, 70 and 95 mm centres with 623 pockets](https://xemstudio.com/objects/tri-clamp-con-rod/): Ø3 crank pin through the rod's 623

### Alternatives
- [Counterweighted crank discs, Ø5 bore, 10 to 30 mm stroke](https://xemstudio.com/objects/counterweighted-crank-discs/): balanced webs

### Also needed
- [Crankshafts Ø3, Ø5 and Ø8 with full-length D-flat](https://xemstudio.com/objects/stirling-crankshafts/): Ø8 shaft, Ø3 × 19 crank pin
- [Set screws (grub screws), M3–M8 (ISO 4026)](https://xemstudio.com/objects/set-screws-metric/): M3 grub

## Questions

**What stroke do the tri-clamp crank webs give?**

16 mm (1.5 in), 24 mm (2 in) and 36 mm (3 in): the Ø3 pin is 8, 12 or 18 mm off the Ø8 bore.

**How is the web fixed to the shaft?**

An M3 grub in the Ø2.5 radial hole, onto the Ø8 shaft (on its flat if it has one).

## Fits with

- [Tri-clamp crank frame: ISO 2852 cap with 608 towers for a Ø8 crankshaft, 1.5, 2 and 3 in](https://xemstudio.com/objects/tri-clamp-crank-frame/)
- [Tri-clamp con-rod: 58, 70 and 95 mm centres with 623 pockets](https://xemstudio.com/objects/tri-clamp-con-rod/)
- [Counterweighted crank discs, Ø5 bore, 10 to 30 mm stroke](https://xemstudio.com/objects/counterweighted-crank-discs/)
- [Crankshafts Ø3, Ø5 and Ø8 with full-length D-flat](https://xemstudio.com/objects/stirling-crankshafts/)
- [Set screws (grub screws), M3–M8 (ISO 4026)](https://xemstudio.com/objects/set-screws-metric/)