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Open flat belt and two pulleys (2 : 1)

Name: Open flat belt and two pulleys (2 : 1) dimension sheet
Creator: Xem Studio
License: https://creativecommons.org/licenses/by/4.0/

How do you work out a belt drive's ratio and length? · Hardware · basis: Xem Studio design following Brown No. 1 (1868)

Also called: belt drive, pulley and belt, flat belt drive, transmisión por correa y poleas, Riementrieb

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

sizes: 4 in table

Notes

An open belt on two pulleys turns both shafts the same way; speed ratio = D₂/D₁ = 80/40 = 2 : 1 (less a little slip). Belt inside length here 471.36 mm for 140 mm centres.
Wrap on the small pulley = 2·acos((R₂ − R₁)/C) = 163.6°: the smaller the wrap, the less torque before slipping.
Brown's No. 1 (belt and pulleys); a crossed belt (No. 2) reverses the driven shaft.
Parts (each has its own page): flanged-flat-pulley-40, flanged-flat-pulley-80, flat-belt-1-5x16-pulleys-40-80-140.
Brown's movement No. 1 (1868) shows it; this model is a Xem Studio design following his figure, every part at true size.

Open flat belt and two pulleys size chart

parameter	value
pulleys	Ø40 and Ø80, flanged
centres	140 mm
ratio	2 : 1
belt	16 × 1.5, 471.36 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.org	web	Publisher's page; dimensions are facts
507movements.com	Brown's movement No. 1: figure, his text and an animation	web	Publisher's page; dimensions are facts

Free files

★ Free files 1 parts. Generated by Xem Studio from the standard; threads are plain cylinders at major diameter. CC BY 4.0. index.json

belt-and-pulleys-mechanism-assembly

Assembled 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=belt-and-pulleys-mechanism

Open flat belt and two pulleys (2 : 1), isometric render of a generated part — Render of belt-and-pulleys-mechanism-assembly from the free STEP; not to scale.

Fits with

Free

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 Free

Flanged flat-belt pulley Ø80, 16 mm face, Ø8 bore, isometric render of a generated part

Flanged flat-belt pulley Ø80, 16 mm face, Ø8 bore86.0×86.0×20.0 mm★ 1 file Free

Flat belt 16 × 1.5 for Ø40 and Ø80 pulleys at 140 mm (loop drawn on the pulleys), isometric render of a generated part

Flat belt 16 × 1.5 for Ø40 and Ø80 pulleys at 140 mm (loop drawn on the pulleys)203.0×83.0×16.0 mm★ 1 file

Questions

How do you work out a belt drive's ratio and length?

An open belt on two pulleys turns both shafts the same way; speed ratio = D₂/D₁ = 80/40 = 2 : 1 (less a little slip). Belt inside length here 471.36 mm for 140 mm centres.