# Pulleys of the first system, 3 movable pulleys (8 : 1)

> How does each movable pulley double the advantage?

- Category: Mechanisms › Pulleys and tackle
- Kind: Hardware
- Basis: Xem Studio design following Brown No. 20 (1868)
- Page: https://xemstudio.com/objects/first-system-pulleys-8-to-1-mechanism/ · JSON: https://xemstudio.com/api/geometry?object=first-system-pulleys-8-to-1-mechanism · Plain text: https://xemstudio.com/objects/first-system-pulleys-8-to-1-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

- Each movable pulley hangs in its own rope, one end fixed to the beam, the other tied to the next pulley up; the last rope goes to the hand. Every pulley halves the pull passed on, so P = W/2^n = W/8 with n = 3, and the hand moves 8 times as far as the weight.
- Pitch-Ø30 sheaves; ropes' standing ends in the beam at x = -15, 0, 15; the hauling part comes up at x = 45. The runner blocks hang from the previous rope by a socket under their sheave.
- Brown's No. 20 (combinations following the rule that each movable pulley doubles the effect).
- Parts (each has its own page): tackle-beam-240-sockets, tackle-block-15-bottom-stem, tackle-block-15-bottom-socket, rope-sheave-3mm-pitch-30, ropes-3mm-first-system-pulleys-8-to-1, tackle-weight-d40x40-socket, dowel-pins-metric.
- Brown's movement No. 20 (1868) shows it; this model is a Xem Studio design following his figure, every part at true size.

## Sizes

| parameter | value |
|---|---|
| movable pulleys | 3 × pitch Ø30 |
| ropes | 3 |
| mechanical advantage | 8 |
| hand travel / weight travel | 8 |

## 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. 20: figure, his text and an animation](https://507movements.com/mm_020.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/first-system-pulleys-8-to-1-mechanism/index.json · license: https://xemstudio.com/files/hardware/first-system-pulleys-8-to-1-mechanism/LICENSE.md

- first-system-pulleys-8-to-1-mechanism-assembly: [STEP](https://xemstudio.com/files/hardware/first-system-pulleys-8-to-1-mechanism/first-system-pulleys-8-to-1-mechanism-assembly.step) · [STL](https://xemstudio.com/files/hardware/first-system-pulleys-8-to-1-mechanism/first-system-pulleys-8-to-1-mechanism-assembly.stl) — Assembled mechanism, all parts placed at one pose (STEP keeps each part separate)

## Questions

**How does each movable pulley double the advantage?**

Each movable pulley hangs in its own rope, one end fixed to the beam, the other tied to the next pulley up; the last rope goes to the hand. Every pulley halves the pull passed on, so P = W/2^n = W/8 with n = 3, and the hand moves 8 times as far as the weight.

## Fits with

- [Tackle beam 240 × 20 × 12 with Ø3 sockets every 5 mm](https://xemstudio.com/objects/tackle-beam-240-sockets/)
- [Single block for a pitch-Ø30 sheave, stem down (movable block or floor block)](https://xemstudio.com/objects/tackle-block-15-bottom-stem/)
- [Single runner block for a pitch-Ø30 sheave, rope socket below](https://xemstudio.com/objects/tackle-block-15-bottom-socket/)
- [Rope sheave for Ø3 rope, pitch Ø30 (rope centre), Ø34.4 rim, Ø4 bore](https://xemstudio.com/objects/rope-sheave-3mm-pitch-30/)
- [Ø3 ropes for the pulleys of the first system, 3 movable pulleys (drawn in place)](https://xemstudio.com/objects/ropes-3mm-first-system-pulleys-8-to-1/)
- [Weight Ø40 × 40 with a Ø3 top socket (394.58 g in steel)](https://xemstudio.com/objects/tackle-weight-d40x40-socket/)
- [Dowel pins, 2–6 mm (ISO 2338 / DIN 6325)](https://xemstudio.com/objects/dowel-pins-metric/)