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

How does each movable pulley double the advantage? · Hardware · basis: Xem Studio design following Brown No. 20 (1868)

Also called: first system of pulleys, compound pulley, 8 to 1 pulley, runner tackle, sistema de poleas de primera clase (8:1), Potenzflaschenzug (8:1)

Exact dimensions. True size, with no printing tolerance added.

sizes
4 in table

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.

Pulleys of the first system, 3 movable pulleys size chart

parametervalue
movable pulleys3 × pitch Ø30
ropes3
mechanical advantage8
hand travel / weight travel8

Where the files are

Other publishers' files are linked, not hosted. "verify" = check the license at the link before commercial use.

Henry T. Brown (1868, public domain)Five Hundred and Seven Mechanical Movements — scan on archive.orgwebPublisher's page; dimensions are facts
507movements.comBrown's movement No. 20: figure, his text and an animationwebPublisher's page; dimensions are facts

Free files

★ Free files 1 parts. Xem Studio design: free to use, print and sell things from; not to be republished as files. Xem Studio Design License. index.json

first-system-pulleys-8-to-1-mechanism-assemblyAssembled mechanism, all parts placed at one pose (STEP keeps each part separate)STEP · STL
Let your AI pull this. Add https://xemstudio.com/mcp to Claude, ChatGPT, Cursor or any MCP client (free, no account, one minute) and it can look up exact sizes, mating fits and free STEP/STL from every chat.
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Plain text: sheet.txt · JSON: /api/geometry?object=first-system-pulleys-8-to-1-mechanism

Pulleys of the first system, 3 movable pulleys (8 : 1), isometric render of a generated part
Render of first-system-pulleys-8-to-1-mechanism-assembly from the free STEP; not to scale.

Fits with

Tackle beam 240 × 20 × 12 with Ø3 sockets every 5 mm, isometric render of a generated part
Tackle beam 240 × 20 × 12 with Ø3 sockets every 5 mm240.0×20.0×12.0 mm★ 1 file
Single block for a pitch-Ø30 sheave, stem down (movable block or floor block), isometric render of a generated part
Single block for a pitch-Ø30 sheave, stem down (movable block or floor block)40.4×13.0×53.2 mm★ 1 file
Single runner block for a pitch-Ø30 sheave, rope socket below, isometric render of a generated part
Single runner block for a pitch-Ø30 sheave, rope socket below40.4×13.0×45.2 mm★ 1 file
Rope sheave for Ø3 rope, pitch Ø30 (rope centre), Ø34.4 rim, Ø4 bore, isometric render of a generated part
Rope sheave for Ø3 rope, pitch Ø30 (rope centre), Ø34.4 rim, Ø4 bore34.4×8.0×34.4 mm★ 1 file
Ø3 ropes for the pulleys of the first system, 3 movable pulleys (drawn in place), isometric render of a generated part
Ø3 ropes for the pulleys of the first system, 3 movable pulleys (drawn in place)33.0×3.0×224.5 mm★ 3 files
Weight Ø40 × 40 with a Ø3 top socket (394.58 g in steel), isometric render of a generated part
Weight Ø40 × 40 with a Ø3 top socket (394.58 g in steel)40.0×40.0×40.0 mm★ 1 file
Dowel pins, 2–6 mm (ISO 2338 / DIN 6325), isometric render of a generated part
Dowel pins, 2–6 mm (ISO 2338 / DIN 6325)5 sizes★ 23 files

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.