Xem Studiomeasured geometryLibrary › Mechanisms › Intermittent motion ·
Mutilated pinion and double rack (continuous rotation to reciprocation)
How does a half-toothed gear make a rack go back and forth? · Hardware · basis: Xem Studio design following Brown No. 114 (1868)
Also called: mutilated gear rack, reciprocating rack and pinion, intermittent rack, engranaje mutilado con doble cremallera, Teilzahnrad mit Doppelzahnstange
Exact dimensions. True size, with no printing tolerance added.
- sizes
- 3 in table
Notes
- A pinion with teeth on half its rim turns continuously between two facing racks on one frame: for half a turn it drives the upper rack (frame moves one way 31.42 mm), for the other half the lower rack (frame comes back).
- The toothless half is cut to the root circle so it clears the other rack; the racks are spaced one pitch diameter apart (20 mm) with their teeth in phase, which keeps the hand-over clean (half a turn = 10 pitches each way).
- Brown's No. 114.
- Parts (each has its own page): mutilated-pinion-m1-20t-half, double-rack-frame-120.
- Brown's movement No. 114 (1868) shows it; this model is a Xem Studio design following his figure, every part at true size.
Mutilated pinion and double rack size chart
| parameter | value |
|---|---|
| pinion | module 1, 10 of 20 teeth |
| rack spacing (pitch lines) | 20 mm |
| stroke | 31.42 mm each way |
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. 114: 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
| mutilated-gear-double-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-double-rack-mechanism
Fits with
Questions
How does a half-toothed gear make a rack go back and forth?
A pinion with teeth on half its rim turns continuously between two facing racks on one frame: for half a turn it drives the upper rack (frame moves one way 31.42 mm), for the other half the lower rack (frame comes back).