# Tri-clamp con-rod: 58, 70 and 95 mm centres with 623 pockets

> How long is the con-rod for a 2 inch tri-clamp piston?

- Category: Stirling engines › Tri-clamp engine parts
- Kind: Hardware
- Basis: Rod centres = wrist-pin height + crank height + stroke/2 (1.5 in 58, 2 in 70, 3 in 95 mm), keeping the rod angle under 11°
- Page: https://xemstudio.com/objects/tri-clamp-con-rod/ · JSON: https://xemstudio.com/api/geometry?object=tri-clamp-con-rod · Plain text: https://xemstudio.com/objects/tri-clamp-con-rod/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

- An I-section connecting rod with a Ø10 pocket for a 623 bearing at each end: the small end on the piston's Ø3 wrist pin, the big end on the Ø3 crank pin.
- Centres 58 / 70 / 95 mm for the 1.5 / 2 / 3 in piston and crank frame. 5 mm thick, Ø14 ends, 10 mm wide web recessed 1.2 mm each side (2.6 mm web).
- Overall 72 / 84 / 109 mm long. At bottom dead centre the piston skirt is flush with the ferrule face.

## 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 |
|---|---|---|---|---|
| con-rod bearing pockets | Ø10 | 623 bearing | press | conrod-* |

## Sizes

| spool_in | centres_mm | overall_len_mm | thickness_mm | end_od_mm | pockets |
|---|---|---|---|---|---|
| 1.5 | 58 | 72 | 5 | 14 | 623 (Ø10) both ends |
| 2 | 70 | 84 | 5 | 14 | 623 (Ø10) both ends |
| 3 | 95 | 109 | 5 | 14 | 623 (Ø10) both ends |

## 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-con-rod/index.json

- conrod-1.5in-58: [STEP](https://xemstudio.com/files/hardware/tri-clamp-power-pistons/conrod-1.5in-58.step) · [STL](https://xemstudio.com/files/hardware/tri-clamp-power-pistons/conrod-1.5in-58.stl) — 1.5 in con-rod, 58 mm centres, 5 mm thick, Ø10 623 pockets both ends (wrist pin and crank pin Ø3)
- conrod-2in-70: [STEP](https://xemstudio.com/files/hardware/tri-clamp-power-pistons/conrod-2in-70.step) · [STL](https://xemstudio.com/files/hardware/tri-clamp-power-pistons/conrod-2in-70.stl) — 2 in con-rod, 70 mm centres, 5 mm thick, Ø10 623 pockets both ends (wrist pin and crank pin Ø3)
- conrod-3in-95: [STEP](https://xemstudio.com/files/hardware/tri-clamp-power-pistons/conrod-3in-95.step) · [STL](https://xemstudio.com/files/hardware/tri-clamp-power-pistons/conrod-3in-95.stl) — 3 in con-rod, 95 mm centres, 5 mm thick, Ø10 623 pockets both ends (wrist pin and crank pin Ø3)

## How it fits

### Connects to
- [Tri-clamp power piston: ring-less full-bore pistons Ø34.8, Ø47.5 and Ø72.9](https://xemstudio.com/objects/tri-clamp-power-piston/): small-end 623 on the Ø3 wrist pin
- [Tri-clamp crank web: Ø8 bore, Ø3 crank pin at 8, 12 and 18 mm throw](https://xemstudio.com/objects/tri-clamp-crank-web/): big-end 623 on the Ø3 crank pin

### Alternatives
- [Crank discs for a Ø5 shaft, 10 to 30 mm stroke](https://xemstudio.com/objects/crank-discs-5mm-bore/): other rod lengths

### Also needed
- [Ball bearings, 683 to 6210 and flanged F6xx (ISO 15)](https://xemstudio.com/objects/ball-bearings-metric/): two 623 (3 × 10 × 4)

## Questions

**How long is the 2 inch tri-clamp con-rod?**

70 mm between centres, 84 mm overall, 5 mm thick, with a 623 pocket (Ø10) at each end.

**How are the con-rod lengths worked out?**

Wrist-pin height + crank height + half the stroke: 23.5 + 34 + 12 ≈ 70 mm for 2 in.

## Fits with

- [Tri-clamp power piston: ring-less full-bore pistons Ø34.8, Ø47.5 and Ø72.9](https://xemstudio.com/objects/tri-clamp-power-piston/)
- [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 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/)
- [Ball bearings, 683 to 6210 and flanged F6xx (ISO 15)](https://xemstudio.com/objects/ball-bearings-metric/)
- [Crank discs for a Ø5 shaft, 10 to 30 mm stroke](https://xemstudio.com/objects/crank-discs-5mm-bore/)