Blocks and tackle, two sheaves in each block (4 : 1) — dimension sheet
Source: Xem Studio, https://xemstudio.com/objects/blocks-and-tackle-mechanism/  (sheet CC BY 4.0; files Xem Studio Design License, https://xemstudio.com/license/)
Basis: Xem Studio design following Brown No. 14 (1868)
Catalog version: 2026-10-20

Sizes: see table below
- With n sheaves in the lower (moving) block, 2n strands hold it up: the power is the weight divided by twice the number of lower sheaves (P = W/4 here), and the hauling part moves four times as far.
- Drawn as a fiddle tackle so every strand hangs vertical in one plane: the upper block has pitch-Ø80 and pitch-Ø30 sheaves one above the other, the lower block pitch-Ø19 and pitch-Ø25 side by side. Standing end on the upper block's becket; strands at x = −34, −15, 15, 40 carry the load, the hauling part comes down at x = −40.
- Brown's No. 14 (blocks and tackle). Real blocks put the sheaves side by side on one pin; the rope then leads slightly sideways between them.
- Parts (each has its own page): tackle-beam-240-sockets, tackle-block-fiddle-upper-80-30, tackle-block-fiddle-lower-19-25, rope-sheave-3mm-pitch-80, rope-sheave-3mm-pitch-30, rope-sheave-3mm-pitch-19, rope-sheave-3mm-pitch-25, ropes-3mm-blocks-and-tackle, tackle-weight-d40x40-socket, dowel-pins-metric.
- Brown's movement No. 14 (1868) shows it; this model is a Xem Studio design following his figure, every part at true size.

parameter  value
upper block  pitch Ø80 + pitch Ø30 sheaves
lower block  pitch Ø19 + pitch Ø25 sheaves
supporting strands  4
mechanical advantage  4 (no friction)

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. 14: figure, his text and an animation — web — Publisher's page; dimensions are facts — https://507movements.com/mm_014.html

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