# Rocking shaft driving an upright shaft continuously through two opposed ratchets and bevel gears

> How can a rocking shaft drive another shaft round continuously?

- Category: Mechanisms › Intermittent motion
- Kind: Hardware
- Basis: Xem Studio design following Brown No. 49 (1868)
- Page: https://xemstudio.com/objects/opposed-ratchets-bevel-gears-rocking-mechanism/ · JSON: https://xemstudio.com/api/geometry?object=opposed-ratchets-bevel-gears-rocking-mechanism · Plain text: https://xemstudio.com/objects/opposed-ratchets-bevel-gears-rocking-mechanism/sheet.txt
- License: dimension sheet CC BY 4.0 (Xem Studio); files Xem Studio Design License (free to use and sell from, not to redistribute as files: https://xemstudio.com/license/)
- Use in every chat: add https://xemstudio.com/mcp as a connector (https://xemstudio.com/use-with-ai/)

**Exact dimensions.** True size, with no printing tolerance added.

## Notes

- Resize: multiply every length by one factor k and the motion stays identical: angles, ratios, timing and the formulas below do not change, because a mechanism's motion depends only on the ratios of its lengths. Here, stays the same: gears, ratchets.
- Resize: fit clearances stay in mm (a slide fit is the same gap at any size); keep every printed wall and pin at least two nozzle widths; mass grows with k³ but part strength only with k², so at k = 2 parts are about 8× heavier and 4× stronger: check pins and thin links when scaling up.
- Two mitre gears ride loose on the rocking cross shaft, facing each other across a third gear on the upright shaft. Each carries a ratchet wheel; a pawl on an arm keyed to the cross shaft drives each, the two ratchets set opposite ways.
- Rocking one way, pawl A drives gear A; rocking back, pawl B drives gear B. Because A and B sit on opposite sides of the upright gear, both turn it the same way: the upright shaft goes round (almost) continuously while the cross shaft only rocks.
- Built from three module 2, 24-tooth spherical-involute mitre gears (cone distance 33.94 mm) and two copies of the catalog 24-tooth ratchet, feed pawl and feed arm (Brown No. 225 parts); the gears were checked in mesh at six angles. Brown's No. 49.
- Parts (each has its own page): mitre-gear-m2-24t-bore5, ratchet-wheels, ratchet-feed-pawl-24t-d40, ratchet-feed-arm-30, linear-shafts-h6.
- Brown's movement No. 49 (1868) shows it; this model is a Xem Studio design following his figure, every part at true size.

## Sizes

| parameter | value |
|---|---|
| gears | 3 × mitre, module 2, 24 T |
| ratchets | 2 × 24 T Ø40, opposite hands |
| input | cross shaft rocking |
| output | upright shaft, one direction |

## Where the files are

- Henry T. Brown (1868, public domain): [Five Hundred and Seven Mechanical Movements — scan on archive.org](https://archive.org/details/fivehundredseven00browiala) — web — Publisher's page; dimensions are facts
- 507movements.com: [Brown's movement No. 49: figure, his text and an animation](https://507movements.com/mm_049.html) — web — Publisher's page; dimensions are facts

## Free STEP/STL (1 parts, Xem Studio Design License, Xem Studio)

Index: https://xemstudio.com/files/hardware/opposed-ratchets-bevel-gears-rocking-mechanism/index.json · license: https://xemstudio.com/files/hardware/opposed-ratchets-bevel-gears-rocking-mechanism/LICENSE.md

- opposed-ratchets-bevel-gears-rocking-mechanism-assembly: [STEP](https://xemstudio.com/files/hardware/opposed-ratchets-bevel-gears-rocking-mechanism/opposed-ratchets-bevel-gears-rocking-mechanism-assembly.step) · [STL](https://xemstudio.com/files/hardware/opposed-ratchets-bevel-gears-rocking-mechanism/opposed-ratchets-bevel-gears-rocking-mechanism-assembly.stl) — Assembled mechanism, all parts placed at one pose (STEP keeps each part separate)

## Questions

**How can a rocking shaft drive another shaft round continuously?**

Two mitre gears ride loose on the rocking cross shaft, facing each other across a third gear on the upright shaft. Each carries a ratchet wheel; a pawl on an arm keyed to the cross shaft drives each, the two ratchets set opposite ways.

## Fits with

- [Mitre (bevel) gear, module 2, 24 teeth, Ø5 bore, spherical involute (spline flanks)](https://xemstudio.com/objects/mitre-gear-m2-24t-bore5/)
- [Ratchet wheels Ø40 with 12, 24 and 36 teeth](https://xemstudio.com/objects/ratchet-wheels/)
- [Feed pawl for the 24-tooth Ø40 ratchet (pivot 30 mm from the wheel axis)](https://xemstudio.com/objects/ratchet-feed-pawl-24t-d40/)
- [Ratchet feed arm, pawl pivot at 30 mm, Ø5 hub](https://xemstudio.com/objects/ratchet-feed-arm-30/)
- [Linear shafts Ø3 to Ø25 mm (h6), 100 to 1000 mm long](https://xemstudio.com/objects/linear-shafts-h6/)