# Pawl 24 mm with a Ø3 pivot for the Ø40 ratchet wheels

> How is a pawl for a ratchet wheel shaped?

- Category: Stirling engines › Drives & mechanisms
- Kind: Hardware
- Basis: Pawl 24 mm from pivot to tip, 8 wide, 6 thick, Ø10 boss with a Ø3 pivot hole
- Page: https://xemstudio.com/objects/ratchet-pawl/ · JSON: https://xemstudio.com/api/geometry?object=ratchet-pawl · Plain text: https://xemstudio.com/objects/ratchet-pawl/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 pawl 6 thick: a Ø10 boss with a Ø3 pivot hole, an 8 mm wide arm and a pointed tip 24 mm from the pivot. Overall 29 × 10 × 6.
- It turns on a Ø3 pin; the tip locks against a tooth face and the sloped tooth backs lift it on the free stroke.
- Its contact point trails the pivot in the locking direction so load drives it into the tooth; a spring holds it down (not drawn).

## 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 |
|---|---|---|---|---|
| pawl pivot hole | Ø3 | Ø3 pin (pawl turns on it) | run | pawl-* |

## Sizes

| feature | value_mm |
|---|---|
| pivot to tip | 24 |
| arm width | 8 |
| thickness | 6 |
| pivot boss | Ø10 |
| pivot hole | Ø3 |
| overall | 29 × 10 × 6 |

## Where the files are

- Wikipedia: [Ratchet (device)](https://en.wikipedia.org/wiki/Ratchet_(device)) — web — CC BY-SA 4.0 (text)
- Wikipedia: [Pawl](https://en.wikipedia.org/wiki/Pawl) — 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 (1 parts, CC BY 4.0, Xem Studio)

Index: https://xemstudio.com/files/hardware/ratchet-pawl/index.json

- pawl-24: [STEP](https://xemstudio.com/files/hardware/ratchet-and-pawl/pawl-24.step) · [STL](https://xemstudio.com/files/hardware/ratchet-and-pawl/pawl-24.stl) — pawl 24 mm, Ø3 pivot hole, for the Ø40 wheels; spring not modeled

## How it fits

### Connects to
- [Ratchet wheels Ø40 with 12, 24 and 36 teeth](https://xemstudio.com/objects/ratchet-wheels/): tip on the Ø40 wheel's teeth

### Also needed
- [Crank and wrist pins Ø3 × 12, 16, 19, 20 and 23](https://xemstudio.com/objects/pins-3mm/): Ø3 pivot pin
- [Torsion spring wire Ø0.8, OD 8, 6 coils](https://xemstudio.com/objects/torsion-spring/): pawl return

## Questions

**Which way does the pawl point?**

Its contact point trails the pivot in the locking direction, so load drives it into the tooth.

**What does the pawl pivot on?**

A Ø3 pin through its Ø3 hole.

## Fits with

- [Ratchet wheels Ø40 with 12, 24 and 36 teeth](https://xemstudio.com/objects/ratchet-wheels/)
- [Crank and wrist pins Ø3 × 12, 16, 19, 20 and 23](https://xemstudio.com/objects/pins-3mm/)
- [Torsion spring wire Ø0.8, OD 8, 6 coils](https://xemstudio.com/objects/torsion-spring/)
- [Dowel pins, 2–6 mm (ISO 2338 / DIN 6325)](https://xemstudio.com/objects/dowel-pins-metric/)