# Connecting rods 30 to 80 mm centres with 623 pockets

> What does a model engine connecting rod with 623 bearings look like?

- Category: Stirling engines › Drives & mechanisms
- Kind: Hardware
- Basis: Flat rod 5 thick, Ø14 ends with Ø10 pockets (623 OD) at the stated centres
- Page: https://xemstudio.com/objects/connecting-rods-623/ · JSON: https://xemstudio.com/api/geometry?object=connecting-rods-623 · Plain text: https://xemstudio.com/objects/connecting-rods-623/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 flat rod 5 thick: an 8 mm wide web between two Ø14 bosses, each with a Ø10 pocket through for a 623 (3 × 10 × 4).
- Centres 30, 40, 50, 60 and 80 mm; overall length centres + 14.
- Both ends run on Ø3 pins. A rod at least twice the stroke keeps the piston side load low; the 2 in engines pair conrod-50 with a 20 mm stroke.

## 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

| file | centres | overall | thickness | pockets |
|---|---|---|---|---|
| conrod-30 | 30 | 44 | 5 | 2 × Ø10 |
| conrod-40 | 40 | 54 | 5 | 2 × Ø10 |
| conrod-50 | 50 | 64 | 5 | 2 × Ø10 |
| conrod-60 | 60 | 74 | 5 | 2 × Ø10 |
| conrod-80 | 80 | 94 | 5 | 2 × Ø10 |

## Where the files are

- Wikipedia: [Crank (mechanism)](https://en.wikipedia.org/wiki/Crank_(mechanism)) — web — CC BY-SA 4.0 (text)
- Wikipedia: [Flywheel](https://en.wikipedia.org/wiki/Flywheel) — web — CC BY-SA 4.0 (text)
- Wikipedia: [Stirling engine](https://en.wikipedia.org/wiki/Stirling_engine) — web — CC BY-SA 4.0 (text)
- Long Earth Society: [Engine builds that use these parts (videos and write-ups)](https://longearthsociety.com/engineering/) — web, video — LES site

## Free STEP/STL (5 parts, CC BY 4.0, Xem Studio)

Index: https://xemstudio.com/files/hardware/connecting-rods-623/index.json

- conrod-30: [STEP](https://xemstudio.com/files/hardware/crank-conrod-flywheel-kit/conrod-30.step) · [STL](https://xemstudio.com/files/hardware/crank-conrod-flywheel-kit/conrod-30.stl) — connecting rod, 30 mm centres, Ø10 pockets for 623 bearings both ends, 5 thick
- conrod-40: [STEP](https://xemstudio.com/files/hardware/crank-conrod-flywheel-kit/conrod-40.step) · [STL](https://xemstudio.com/files/hardware/crank-conrod-flywheel-kit/conrod-40.stl) — connecting rod, 40 mm centres, Ø10 pockets for 623 bearings both ends, 5 thick
- conrod-50: [STEP](https://xemstudio.com/files/hardware/crank-conrod-flywheel-kit/conrod-50.step) · [STL](https://xemstudio.com/files/hardware/crank-conrod-flywheel-kit/conrod-50.stl) — connecting rod, 50 mm centres, Ø10 pockets for 623 bearings both ends, 5 thick
- conrod-60: [STEP](https://xemstudio.com/files/hardware/crank-conrod-flywheel-kit/conrod-60.step) · [STL](https://xemstudio.com/files/hardware/crank-conrod-flywheel-kit/conrod-60.stl) — connecting rod, 60 mm centres, Ø10 pockets for 623 bearings both ends, 5 thick
- conrod-80: [STEP](https://xemstudio.com/files/hardware/crank-conrod-flywheel-kit/conrod-80.step) · [STL](https://xemstudio.com/files/hardware/crank-conrod-flywheel-kit/conrod-80.stl) — connecting rod, 80 mm centres, Ø10 pockets for 623 bearings both ends, 5 thick

## How it fits

### Connects to
- [Crank discs for a Ø5 shaft, 10 to 30 mm stroke](https://xemstudio.com/objects/crank-discs-5mm-bore/): 623 on the Ø3 crank pin
- [Rod clevises for a Ø2 or Ø3 rod or a Ø5 tube, 5 mm gap](https://xemstudio.com/objects/rod-clevises/): 5 mm rod end in the 5 mm gap
- [Tri-clamp power piston: ring-less full-bore pistons Ø34.8, Ø47.5 and Ø72.9](https://xemstudio.com/objects/tri-clamp-power-piston/): wrist-pin end

### Also needed
- [Ball bearings, 683 to 6210 and flanged F6xx (ISO 15)](https://xemstudio.com/objects/ball-bearings-metric/): 623 in each Ø10 pocket

## Questions

**What bearings go in the connecting rod?**

A 623 (3 × 10 × 4) in each Ø10 pocket, on Ø3 pins.

**How long a con-rod for a 20 mm stroke?**

At least 40 mm centres; the 2 in tri-clamp engines run 50.

## Fits with

- [Crank discs for a Ø5 shaft, 10 to 30 mm stroke](https://xemstudio.com/objects/crank-discs-5mm-bore/)
- [Rod clevises for a Ø2 or Ø3 rod or a Ø5 tube, 5 mm gap](https://xemstudio.com/objects/rod-clevises/)
- [Crank and wrist pins Ø3 × 12, 16, 19, 20 and 23](https://xemstudio.com/objects/pins-3mm/)
- [Ball bearings, 683 to 6210 and flanged F6xx (ISO 15)](https://xemstudio.com/objects/ball-bearings-metric/)
- [Flanged power cylinder liner Ø16, 20, 25, 30](https://xemstudio.com/objects/power-cylinder-liner/)