# Stepped cone pulleys (three speeds by moving the belt)

> How do stepped cone pulleys change speed?

- Category: Mechanisms › Belt and friction drives
- Kind: Hardware
- Basis: Xem Studio design following Brown No. 8 (1868)
- Page: https://xemstudio.com/objects/stepped-cone-pulleys-mechanism/ · JSON: https://xemstudio.com/api/geometry?object=stepped-cone-pulleys-mechanism · Plain text: https://xemstudio.com/objects/stepped-cone-pulleys-mechanism/sheet.txt
- License: dimension sheet CC BY 4.0 (Xem Studio); linked files under their publishers' licenses
- 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 stepped pulleys mounted head to tail: moving the belt from one step pair to another changes the speed ratio — 50/30 = 1.67, 40/40 = 1, 30/50 = 0.6 — while the belt length stays the same because each pair's diameters add to 80 mm.
- Drawn with the belt on the middle (Ø40 / Ø40) steps, shafts 120 mm apart; belt inside length 365.66 mm.
- Brown's No. 8 (speed pulleys); the classic lathe and drill-press drive.
- Parts (each has its own page): stepped-cone-pulley-50-40-30, flat-belt-1-5x16-pulleys-40-120.
- Brown's movement No. 8 (1868) shows it; this model is a Xem Studio design following his figure, every part at true size.

## Sizes

| parameter | value |
|---|---|
| steps | Ø50 / Ø40 / Ø30 (×2, reversed) |
| ratios | 1.67, 1, 0.6 |
| shaft centres | 120 mm |
| belt | 16 × 1.5 flat |

## 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. 8: figure, his text and an animation](https://507movements.com/mm_008.html) — web — Publisher's page; dimensions are facts

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

Index: https://xemstudio.com/files/hardware/stepped-cone-pulleys-mechanism/index.json

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

## Questions

**How do stepped cone pulleys change speed?**

Two identical stepped pulleys mounted head to tail: moving the belt from one step pair to another changes the speed ratio — 50/30 = 1.67, 40/40 = 1, 30/50 = 0.6 — while the belt length stays the same because each pair's diameters add to 80 mm.

## Fits with

- [Stepped (speed-cone) pulley Ø50 / Ø40 / Ø30 × 20 mm steps, Ø8 bore](https://xemstudio.com/objects/stepped-cone-pulley-50-40-30/)
- [Flat belt 16 × 1.5 for two Ø40 pulleys at 120 mm (loop drawn on the pulleys)](https://xemstudio.com/objects/flat-belt-1-5x16-pulleys-40-120/)