# Cone pulleys (speed cones) for gradually varied speed

> How do cone pulleys vary speed?

- Category: Mechanisms › Belt and friction drives
- Kind: Hardware
- Basis: Xem Studio design following Brown No. 9 (1868)
- Page: https://xemstudio.com/objects/cone-pulleys-mechanism/ · JSON: https://xemstudio.com/api/geometry?object=cone-pulleys-mechanism · Plain text: https://xemstudio.com/objects/cone-pulleys-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 identical cones mounted head to tail: sliding the belt along them changes the ratio smoothly, from r_small/r_large to r_large/r_small, while the sum of the two radii — and so the belt length, nearly — stays the same.
- Here Ø24–Ø56 × 64 cones at 110 mm; at 20 mm along, Ø34 drives Ø46, ratio 0.74. With straight cones an open belt is -1.54 mm slacker near the ends than in the middle (No. 10's curved cones fix that).
- Brown's No. 9 (cones for gradually increasing or decreasing speed, as in cotton machinery). The belt section lies flat on each cone; its strands twist between the two tilts.
- Parts (each has its own page): cone-pulley-24-56x64-bore8, flat-belt-10x1-5-cone-pulleys-c110.
- Brown's movement No. 9 (1868) shows it; this model is a Xem Studio design following his figure, every part at true size.

## Sizes

| parameter | value |
|---|---|
| pulleys | 2 × Ø24–Ø56 × 64, head to tail |
| centres | 110 mm |
| ratio range | 0.43 – 2.33 |
| drawn at 20 mm | ratio 0.74 |
| belt | 10 × 1.5, 345.99 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. 9: figure, his text and an animation](https://507movements.com/mm_009.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/cone-pulleys-mechanism/index.json · license: https://xemstudio.com/files/hardware/cone-pulleys-mechanism/LICENSE.md

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

## Questions

**How do cone pulleys vary speed?**

Two identical cones mounted head to tail: sliding the belt along them changes the ratio smoothly, from r_small/r_large to r_large/r_small, while the sum of the two radii — and so the belt length, nearly — stays the same.

## Fits with

- [Cone pulley Ø24 → Ø56 × 64, Ø8 bore](https://xemstudio.com/objects/cone-pulley-24-56x64-bore8/)
- [Flat belt 10 × 1.5 for two cone pulleys at 110 mm (loop drawn at 20 mm along)](https://xemstudio.com/objects/flat-belt-10x1-5-cone-pulleys-c110/)