# Split eccentric strap for Ø30 sheaves, 51 mm to the eye

> What does an eccentric strap look like?

- Category: Stirling engines › Drives & mechanisms
- Kind: Hardware
- Basis: Ring Ø30 bore × Ø40 OD × 8 with a 1 mm split and a 40 × 10 arm ending in a Ø3 eye
- Page: https://xemstudio.com/objects/eccentric-strap/ · JSON: https://xemstudio.com/api/geometry?object=eccentric-strap · Plain text: https://xemstudio.com/objects/eccentric-strap/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 ring Ø30 bore × Ø40 OD × 8 with a 1 mm split through the side opposite the arm, so it goes over the sheave without taking the shaft apart.
- A 40 × 10 arm ends in a Ø3 eye 51 mm from the ring's centre. Overall 75 × 40 × 8.
- The Ø30 bore turns on the sheave and a Ø3 pin in the eye drives the next link; fits are under Mating features.

## 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 |
|---|---|---|---|---|
| strap bore | Ø30 | Ø30 eccentric (turns in it) | run | eccentric-strap-* |
| strap split | 1.0 | closes on the eccentric | clamp | eccentric-strap-* |
| strap eye | Ø3 | Ø3 pin (turns in it) | run | eccentric-strap-* |

## Sizes

| feature | value_mm |
|---|---|
| bore | Ø30 |
| ring OD | Ø40 |
| thickness | 8 |
| split | 1.0 |
| arm | 40 × 10 |
| eye | Ø3 at 51 |
| overall | 75 × 40 × 8 |

## Where the files are

- Wikipedia: [Eccentric (mechanism)](https://en.wikipedia.org/wiki/Eccentric_(mechanism)) — web — CC BY-SA 4.0 (text)
- Long Earth Society: [Engine and rig builds on extrusion frames](https://longearthsociety.com/engineering/) — web, video — LES site

## Free STEP/STL (1 parts, CC BY 4.0, Xem Studio)

Index: https://xemstudio.com/files/hardware/eccentric-strap/index.json

- eccentric-strap-d30: [STEP](https://xemstudio.com/files/hardware/eccentric-and-strap/eccentric-strap-d30.step) · [STL](https://xemstudio.com/files/hardware/eccentric-and-strap/eccentric-strap-d30.stl) — split strap for the Ø30 eccentrics, Ø30 bore, 40 mm arm with a Ø3 eye

## How it fits

### Goes in or on
- [Eccentric sheaves Ø30 at 3, 5 and 8 mm offset](https://xemstudio.com/objects/eccentric-sheaves/): Ø30 bore on the sheave

### Connects to
- [Four-bar links: flat links with 20 to 100 mm hole centres](https://xemstudio.com/objects/four-bar-links/): Ø3 eye to the link

### Also needed
- [Crank and wrist pins Ø3 × 12, 16, 19, 20 and 23](https://xemstudio.com/objects/pins-3mm/): Ø3 pin in the eye

## Questions

**How does the strap go on?**

Through the 1 mm split, over the Ø30 sheave.

**Where is the strap eye?**

Ø3, 51 mm from the strap centre.

## Fits with

- [Eccentric sheaves Ø30 at 3, 5 and 8 mm offset](https://xemstudio.com/objects/eccentric-sheaves/)
- [Four-bar links: flat links with 20 to 100 mm hole centres](https://xemstudio.com/objects/four-bar-links/)
- [Crank and wrist pins Ø3 × 12, 16, 19, 20 and 23](https://xemstudio.com/objects/pins-3mm/)
- [Clevis pins ISO 2341 B, Ø3 to Ø8](https://xemstudio.com/objects/clevis-pins/)