Xem Studiomeasured geometry

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Single movable pulley (power half the weight)

Why does a movable pulley halve the effort? · Hardware · basis: Xem Studio design following Brown No. 13 (1868)

Also called: movable pulley, running block, pulley mechanical advantage 2, polea móvil, lose Rolle

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

sizes
3 in table

Notes

  • The weight hangs from a pulley that rides in a bight of the rope: two strands hold it up, so each carries half the weight (P = W/2), and the free end moves twice as far as the weight.
  • Here the rope's standing end plugs into the beam 15 mm left of centre, runs under a pitch-Ø30 sheave in the movable block and up to the hand; the Ø40 × 40 weight hangs from the block's stem.
  • Brown's No. 13.
  • Parts (each has its own page): tackle-beam-240-sockets, tackle-block-15-bottom-stem, rope-sheave-3mm-pitch-30, ropes-3mm-single-movable-pulley, tackle-weight-d40x40-socket, dowel-pins-metric.
  • Brown's movement No. 13 (1868) shows it; this model is a Xem Studio design following his figure, every part at true size.

Single movable pulley size chart

parametervalue
sheavepitch Ø30 (Ø3 rope)
mechanical advantage2
hand travel / weight travel2

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. 13: 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

single-movable-pulley-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=single-movable-pulley-mechanism

Single movable pulley (power half the weight), isometric render of a generated part
Render of single-movable-pulley-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
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 rope for the single movable pulley (drawn in place), isometric render of a generated part
Ø3 rope for the single movable pulley (drawn in place)33.0×3.0×134.5 mm★ 1 file
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

Why does a movable pulley halve the effort?

The weight hangs from a pulley that rides in a bight of the rope: two strands hold it up, so each carries half the weight (P = W/2), and the free end moves twice as far as the weight.