Two fixed pulleys and one movable pulley (2 : 1, pull upward) — dimension sheet
Source: Xem Studio, https://xemstudio.com/objects/two-fixed-one-movable-pulley-mechanism/  (sheet CC BY 4.0; files Xem Studio Design License, https://xemstudio.com/license/)
Basis: Xem Studio design following Brown No. 18 (1868)
Catalog version: 2026-10-20

Sizes: see table below
- The movable pulley gives the advantage (two strands hold the weight: P = W/2); the two fixed pulleys only lead the rope — over the top and back round a floor pulley — so the hand can pull in a convenient direction, here upward beside the load.
- Pitch-Ø30 sheaves throughout: standing end in the beam at x = −15, under the movable block, over the fixed block at x = 30, under the floor block at x = 60 and up to the hand at x = 75.
- Brown's No. 18 (two fixed and one movable pulley).
- Parts (each has its own page): tackle-beam-240-sockets, tackle-block-15-bottom-stem, tackle-block-15-top-stem, rope-sheave-3mm-pitch-30, ropes-3mm-two-fixed-one-movable-pulley, tackle-weight-d40x40-socket, dowel-pins-metric.
- Brown's movement No. 18 (1868) shows it; this model is a Xem Studio design following his figure, every part at true size.

parameter  value
sheaves  3 × pitch Ø30
mechanical advantage  2
hand travel / weight travel  2

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. 18: figure, his text and an animation — web — Publisher's page; dimensions are facts — https://507movements.com/mm_018.html

Free files (Xem Studio Design License, Xem Studio; STEP + STL, 1 parts): https://xemstudio.com/files/hardware/two-fixed-one-movable-pulley-mechanism/index.json
API: https://xemstudio.com/api/geometry?object=two-fixed-one-movable-pulley-mechanism