# Rod-end yokes with a side stub pin: Ø5 tube and Ø3 rod

> How do I connect a con-rod to a rod without blocking the rod's axis?

- Category: Hardware › Stirling & thermoacoustic
- Kind: Hardware
- Basis: Design values; Ø3 dowel (ISO 8734) stub pin, 623 con-rod eyes from the con-rod kit on this site
- Page: https://xemstudio.com/objects/tri-clamp-rd-yokes/ · JSON: https://xemstudio.com/api/geometry?object=tri-clamp-rd-yokes · Plain text: https://xemstudio.com/objects/tri-clamp-rd-yokes/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

- A small block on the rod end with a Ø3 dowel pressed 4.5 mm into its side: the con-rod's 623 runs on the 7.5 mm that stand out, beside the block, so the rod's axis stays free.
- The tube yoke has a Ø3.4 passage above its Ø5 socket: in the beta the Ø3 displacer rod runs up through the power piston's tube rod and out of the top of this yoke to its own rod yoke.
- Both hold their rod with an M3 grub.

## 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 |
|---|---|---|---|---|
| tube socket | Ø5 × 12 | Ø5 tube rod (M3 grub) | slide | rd-yoke-tube5* |
| rod passage | Ø3.4 | Ø3 displacer rod (no contact) | designed | rd-yoke-tube5* |
| rod socket | Ø3 × 10 | Ø3 rod (M3 grub) | slide | rd-yoke-rod3* |
| stub-pin hole | Ø3 × 4.5 | Ø3 × 12 dowel | press | all |
| grub hole | Ø2.5 | M3 tap drill | designed | all |

## Sizes

| part | socket_mm | pin_height_mm | height_mm | stub_pin |
|---|---|---|---|---|
| rd-yoke-tube5 | Ø5 × 12 | 17.0 | 21.0 | Ø3 × 12, 4.5 in |
| rd-yoke-rod3 | Ø3 × 10 | 14.0 | 18.0 | Ø3 × 12, 4.5 in |

## Where the files are

- 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-rd-yokes/index.json

- rd-yoke-tube5: [STEP](https://xemstudio.com/files/hardware/tri-clamp-rd-yokes/rd-yoke-tube5.step) · [STL](https://xemstudio.com/files/hardware/tri-clamp-rd-yokes/rd-yoke-tube5.stl) — tube-rod yoke 12 × 14 × 21: Ø5 socket 12 deep with an M3 grub (Ø2.5), Ø3.4 passage above it, Ø3 stub-pin hole 4.5 deep in the −Y face at 17
- rd-yoke-rod3: [STEP](https://xemstudio.com/files/hardware/tri-clamp-rd-yokes/rd-yoke-rod3.step) · [STL](https://xemstudio.com/files/hardware/tri-clamp-rd-yokes/rd-yoke-rod3.stl) — rod yoke 12 × 14 × 18: Ø3 socket 10 deep with an M3 grub (Ø2.5), Ø3 stub-pin hole 4.5 deep in the −Y face at 14

## Questions

**Why a stub pin instead of a clevis?**

A clevis pin crosses the rod's axis; the beta needs a second rod to pass straight through, so the pin stands out to one side.

## Fits with

- [Tri-clamp rolling-diaphragm power head, 2 in: standard clamp face, cylinder, rod guide and crank tower, with its diaphragm seat ring](https://xemstudio.com/objects/tri-clamp-rd-power-head/)
- [Rolling-diaphragm piston and head retainers, 2 in power head](https://xemstudio.com/objects/tri-clamp-rd-piston/)
- [Connecting rods 30 to 80 mm centres with 623 pockets](https://xemstudio.com/objects/connecting-rods-623/)
- [Dowel pins, 2–6 mm (ISO 2338 / DIN 6325)](https://xemstudio.com/objects/dowel-pins-metric/)