Pulleys of the first system, 3 movable pulleys (8 : 1) — dimension sheet
Source: Xem Studio, https://xemstudio.com/objects/first-system-pulleys-8-to-1-mechanism/  (sheet CC BY 4.0; files Xem Studio Design License, https://xemstudio.com/license/)
Basis: Xem Studio design following Brown No. 20 (1868)
Catalog version: 2026-10-20

Sizes: see table below
- 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.

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

Files elsewhere (not hosted by Xem Studio; license as stated by the publisher):
- Henry T. Brown (1868, public domain): Five Hundred and Seven Mechanical Movements — scan on archive.org — web — Publisher's page; dimensions are facts — https://archive.org/details/fivehundredseven00browiala
- 507movements.com: Brown's movement No. 20: figure, his text and an animation — web — Publisher's page; dimensions are facts — https://507movements.com/mm_020.html

Free files (Xem Studio Design License, Xem Studio; STEP + STL, 1 parts): https://xemstudio.com/files/hardware/first-system-pulleys-8-to-1-mechanism/index.json
API: https://xemstudio.com/api/geometry?object=first-system-pulleys-8-to-1-mechanism