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Treadle and crank (crank-rocker four-bar)
How does a treadle turn a wheel? · Hardware · basis: Xem Studio design following Brown No. 158 (1868)
Also called: treadle crank, crank rocker, foot treadle mechanism, four bar crank rocker, pedal y manivela (manivela-balancín), Tretkurbel (Kurbelschwinge)
Exact dimensions. True size, with no printing tolerance added.
- sizes
- 5 in table
Notes
- A foot treadle rocking on a pivot drives a crank round through a connecting rod: a crank-rocker four-bar. Because the crank is the shortest link and next to the frame (Grashof: s + l ≤ p + q), it turns fully while the treadle only rocks.
- Here crank 20, rod 80, treadle 100 and frame 100 mm (catalog four-bar links): the treadle swings 25.08° per crank turn; a flywheel carries the crank through the two dead points where rod and crank line up.
- Brown's No. 158 (treadle driving a disc or crank), the drive of foot lathes, grinders and sewing machines.
- Parts (each has its own page): four-bar-links, dowel-pins-metric.
- Brown's movement No. 158 (1868) shows it; this model is a Xem Studio design following his figure, every part at true size.
Treadle and crank size chart
| parameter | value |
|---|---|
| crank | 20 mm |
| connecting rod | 80 mm |
| treadle | 100 mm |
| frame | 100 mm |
| treadle swing | 25.08° |
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. 158: 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
| treadle-crank-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=treadle-crank-mechanism
Fits with
Questions
How does a treadle turn a wheel?
A foot treadle rocking on a pivot drives a crank round through a connecting rod: a crank-rocker four-bar. Because the crank is the shortest link and next to the frame (Grashof: s + l ≤ p + q), it turns fully while the treadle only rocks.