Xem Studiomeasured geometry

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Rocking segment and band turning two pulleys to and fro

How does a rocking segment drive two pulleys? · Hardware · basis: Xem Studio design following Brown No. 6 (1868)

Also called: segment lever, band drive, oscillating pulley drive, rocking lever band, segmento oscilante con banda, Schwingsegment mit Band

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

sizes
4 in table

Notes

  • A lever rocking on a pivot carries a circular segment; a band fixed to both ends of the segment passes round two pulleys below. Rocking the lever pulls the band one way, then the other, so both pulleys turn back and forth together, in the same direction.
  • Pulley turn = segment turn × R_segment / R_pulley = 50/20 = 2.5: rocking the lever ±20° turns each Ø40 pulley ±50°. The segment's rim spans 198.83° so the band's 174.83° of wrap stays on it.
  • Band 16 × 1.5, 510.14 mm; pulleys 70 mm apart, 110 mm below the pivot. Brown's No. 6.
  • Parts (each has its own page): rocking-segment-lever-r50, flanged-flat-pulley-40, band-16x1-5-segment-r50-two-pulleys-40, linear-shafts-h6.
  • Brown's movement No. 6 (1868) shows it; this model is a Xem Studio design following his figure, every part at true size.

Rocking segment and band turning two pulleys to and fro size chart

parametervalue
segment radius50 mm
pulleys2 × Ø40 (catalog)
ratio2.5 : 1
band16 × 1.5, 510.14 mm

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. 6: 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

segment-lever-band-pulleys-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=segment-lever-band-pulleys-mechanism

Rocking segment and band turning two pulleys to and fro, isometric render of a generated part
Render of segment-lever-band-pulleys-mechanism-assembly from the free STEP; not to scale.

Fits with

Rocking segment lever, R50 rim × 16, Ø8 pivot, 100 mm handle, isometric render of a generated part
Rocking segment lever, R50 rim × 16, Ø8 pivot, 100 mm handle100.0×110.0×23.0 mm★ 1 file
Flanged flat-belt pulley Ø40, 16 mm face, Ø8 bore, isometric render of a generated part
Flanged flat-belt pulley Ø40, 16 mm face, Ø8 bore46.0×46.0×20.0 mm★ 1 file
Band 16 × 1.5 for the R50 segment and two Ø40 pulleys (drawn as a loop), isometric render of a generated part
Band 16 × 1.5 for the R50 segment and two Ø40 pulleys (drawn as a loop)113.0×183.0×16.0 mm★ 1 file
Linear shafts Ø3 to Ø25 mm (h6), 100 to 1000 mm long, isometric render of a generated part
Linear shafts Ø3 to Ø25 mm (h6), 100 to 1000 mm long10 sizes★ 70 files

Questions

How does a rocking segment drive two pulleys?

A lever rocking on a pivot carries a circular segment; a band fixed to both ends of the segment passes round two pulleys below. Rocking the lever pulls the band one way, then the other, so both pulleys turn back and forth together, in the same direction.