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Mutilated spur gear moving a rack, a spring bringing it back
How does a part-toothed gear and a spring make a rack go back and forth? · Hardware · basis: Xem Studio design following Brown No. 81 (1868)
Also called: mutilated gear rack, spring return rack, intermittent rack drive, engranaje mutilado con cremallera y muelle, Teilzahnrad mit Zahnstange und Rückholfeder
Exact dimensions. True size, with no printing tolerance added.
- sizes
- 3 in table
Notes
- A spur gear with teeth on half its rim turns continuously above a rack: while its teeth are in mesh it drives the rack one way and compresses a spring; when the toothless half comes round the spring pushes the rack back.
- Catalog parts: the module 1, 20-tooth mutilated pinion (10 teeth) and the 120 mm full-depth rack; stroke = 10 × π = 31.42 mm. The rack slides on a base against a side rail; an Ø8 spring between the rack's end and the base's end wall returns it. Drawn in mesh.
- Brown's No. 81 (mutilated spur gear giving alternate rectilinear motion to a rack rod, a spring returning it).
- Parts (each has its own page): mutilated-pinion-m1-20t-half, gear-rack-m1-120-full-depth, compression-spring-od8-wire1-l30, rack-guide-base-170-spring-seat, dowel-pins-metric.
- Brown's movement No. 81 (1868) shows it; this model is a Xem Studio design following his figure, every part at true size.
Mutilated spur gear moving a rack, a spring bringing it back size chart
| parameter | value |
|---|---|
| pinion | module 1, 10 of 20 teeth |
| stroke | 31.42 mm |
| spring | OD8 × Ø1 wire |
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. 81: 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
| mutilated-gear-spring-rack-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=mutilated-gear-spring-rack-mechanism
Fits with
Questions
How does a part-toothed gear and a spring make a rack go back and forth?
A spur gear with teeth on half its rim turns continuously above a rack: while its teeth are in mesh it drives the rack one way and compresses a spring; when the toothless half comes round the spring pushes the rack back.