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Two speeds from two belts on fast and loose pulleys
How do fast and loose pulleys give two speeds? · Hardware · basis: Xem Studio design following Brown No. 60 (1868)
Also called: fast and loose pulleys, two speed belt drive, loose pulley, belt shifter, poleas fija y loca (dos velocidades), Fest- und Losscheibe (zwei Gänge)
Exact dimensions. True size, with no printing tolerance added.
- sizes
- 5 in table
Notes
- The upper shaft carries a wide Ø80 and a wide Ø40 pulley; each drives its own belt. Below, each belt can run on a fast pulley (keyed to the shaft) or on a loose one beside it (free to turn). With belt 1 on its fast Ø40 the lower shaft runs at 2 × upper speed; shift belt 1 to its loose pulley and belt 2 onto its fast Ø80 and it runs at 0.5 ×.
- Drawn in the fast (2 : 1) setting: belt 1 on the fast Ø40, belt 2 idling on the loose Ø80. Both belts are the same length, 471.36 mm (Ø40 + Ø80 at 140 mm). Pulleys plain (no flanges) so the belts can be shifted; upper faces 34 mm wide for both positions.
- Brown's No. 60. Only one belt may be on a fast pulley at a time.
- Parts (each has its own page): plain-flat-pulley-80x34, plain-flat-pulley-40x34, plain-flat-pulley-40x16, plain-flat-pulley-80x16, flat-belt-16x1-5-pulleys-40-80-c140-open, linear-shafts-h6.
- Brown's movement No. 60 (1868) shows it; this model is a Xem Studio design following his figure, every part at true size.
Two speeds from two belts on fast and loose pulleys size chart
| parameter | value |
|---|---|
| upper pulleys | Ø80 × 34 and Ø40 × 34 (fast) |
| lower pulleys | Ø40 fast + loose, Ø80 loose + fast, × 16 |
| speeds | 2 : 1 and 1 : 2 |
| belts | 2 × 16 × 1.5, 471.36 mm |
| shafts | Ø8, 140 mm apart |
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. 60: figure, his text and an animation | web | Publisher'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
| fast-and-loose-pulleys-two-speed-mechanism-assembly | Assembled mechanism, all parts placed at one pose (STEP keeps each part separate) | STEP · STL |
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.Plain text: sheet.txt · JSON: /api/geometry?object=fast-and-loose-pulleys-two-speed-mechanism
Fits with
Questions
How do fast and loose pulleys give two speeds?
The upper shaft carries a wide Ø80 and a wide Ø40 pulley; each drives its own belt. Below, each belt can run on a fast pulley (keyed to the shaft) or on a loose one beside it (free to turn). With belt 1 on its fast Ø40 the lower shaft runs at 2 × upper speed; shift belt 1 to its loose pulley and belt 2 onto its fast Ø80 and it runs at 0.5 ×.