# Two speeds by shifting a belt between pulleys carrying gears (20 / 40 T)

> How does shifting a belt between two pulley-gear units give two speeds?

- Category: Mechanisms › Gears
- Kind: Hardware
- Basis: Xem Studio design following Brown No. 59 (1868)
- Page: https://xemstudio.com/objects/belt-shifted-gears-two-speed-mechanism/ · JSON: https://xemstudio.com/api/geometry?object=belt-shifted-gears-two-speed-mechanism · Plain text: https://xemstudio.com/objects/belt-shifted-gears-two-speed-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

- Two loose units on the input shaft, each a pulley with a gear (20 and 40 teeth), mesh with a 40 / 20 cluster on the output shaft. The belt on the 20-tooth unit's pulley gives the output half the pulley's speed; shifted onto the 40-tooth unit, twice — the unit not driven just idles.
- Module 1, 30 mm centres; belt from a wide Ø40 driving pulley 140 mm above, drawn on the 20-tooth unit.
- Brown's No. 59 (two speeds from a belt shifted between pulleys carrying small and large gears).
- Parts (each has its own page): pulley-gear-unit-40-m1-20t-bore8, pulley-gear-unit-40-m1-40t-bore8, gear-cluster-m1-40-20-bore8, plain-flat-pulley-40x66, flat-belt-16x1-5-pulleys-40-40-c140, linear-shafts-h6.
- Brown's movement No. 59 (1868) shows it; this model is a Xem Studio design following his figure, every part at true size.

## Sizes

| parameter | value |
|---|---|
| units | Ø40 pulleys with 20 / 40 T gears |
| cluster | 40 / 20 T |
| speeds | 0.5, 2 × input |
| centres | 30 mm |

## 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. 59: figure, his text and an animation](https://507movements.com/mm_059.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/belt-shifted-gears-two-speed-mechanism/index.json · license: https://xemstudio.com/files/hardware/belt-shifted-gears-two-speed-mechanism/LICENSE.md

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

## Questions

**How does shifting a belt between two pulley-gear units give two speeds?**

Two loose units on the input shaft, each a pulley with a gear (20 and 40 teeth), mesh with a 40 / 20 cluster on the output shaft. The belt on the 20-tooth unit's pulley gives the output half the pulley's speed; shifted onto the 40-tooth unit, twice — the unit not driven just idles.

## Fits with

- [Pulley and gear unit: Ø40 × 16 flat pulley with a module 1, 20-tooth gear, Ø8 bore](https://xemstudio.com/objects/pulley-gear-unit-40-m1-20t-bore8/)
- [Pulley and gear unit: Ø40 × 16 flat pulley with a module 1, 40-tooth gear, Ø8 bore](https://xemstudio.com/objects/pulley-gear-unit-40-m1-40t-bore8/)
- [Gear cluster, module 1: 40 T / 20 T on one Ø14 hub, Ø8 bore](https://xemstudio.com/objects/gear-cluster-m1-40-20-bore8/)
- [Plain flat-belt pulley Ø40 × 66 face, Ø8 bore (no flanges)](https://xemstudio.com/objects/plain-flat-pulley-40x66/)
- [Flat belt 16 × 1.5 for two Ø40 pulleys at 140 mm (loop drawn)](https://xemstudio.com/objects/flat-belt-16x1-5-pulleys-40-40-c140/)
- [Linear shafts Ø3 to Ø25 mm (h6), 100 to 1000 mm long](https://xemstudio.com/objects/linear-shafts-h6/)