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Geneva stop (Maltese cross stop-work): finger wheel limited to four turns
How does a Geneva stop limit the number of turns? · Hardware · basis: Xem Studio design following Brown No. 212 (1868)
Also called: geneva stop, maltese cross stop, stop work, winding stop, geneva mechanism, parada de Ginebra (cruz de Malta), Malteserkreuz-Gesperre (Aufzugsbegrenzung)
Exact dimensions. True size, with no printing tolerance added.
- sizes
- 5 in table
Notes
- Resize: multiply every length by one factor k and the motion stays identical: angles, ratios, timing and the formulas below do not change, because a mechanism's motion depends only on the ratios of its lengths. Here, scales with k: centres; stays the same: star, turns allowed, engagement; step to the nearest standard size (and redraw the hole or pocket it fits): pin.
- Resize: fit clearances stay in mm (a slide fit is the same gap at any size); keep every printed wall and pin at least two nozzle widths; mass grows with k³ but part strength only with k², so at k = 2 parts are about 8× heavier and 4× stronger: check pins and thin links when scaling up.
- A finger wheel with one pin indexes a five-position Maltese cross one position per turn, the locking disc holding the cross still in between (a Geneva drive). One of the five positions is not a slot but a convex tooth: when the pin comes round to it the tooth will not let it in, and the finger wheel is stopped — after four turns in one direction (and four back). Brown: used in Swiss watches to limit the winding; the convex curved portion of the star is the stop.
- Standard Geneva proportions on 40 mm centres: pin radius a·sin 36° = 23.51, star tip radius a·cos 36° = 32.36, so the pin enters and leaves each slot along the slot (no shock); Ø4 pin in 4 mm slots, locking disc Ø41.02 cut back by the star's exact sweep. Checked at ten wheel angles through an indexing and at the last slot before the stop: no overlap beyond contact; with the stop tooth in place of a slot the pin collides 6° past the entry angle (75.4 mm³), which is the stop.
- Drawn with the pin entering the second slot (-20° before the line of centres), the stop tooth three positions on.
- Parts (each has its own page): geneva-stop-finger-wheel-r23-5-pin4, geneva-stop-star-5-positions-4-slots-r32-4, linear-shafts-h6.
- Brown's movement No. 212 (1868) shows it; this model is a Xem Studio design following his figure, every part at true size.
Geneva stop (Maltese cross stop-work): finger wheel limited to four… size chart
| parameter | value |
|---|---|
| centres | 40 mm |
| star | 5 positions: 4 slots + 1 stop tooth |
| pin | Ø4 at r 23.51 |
| turns allowed | 4 |
| engagement | 108° of the wheel's turn per index |
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. 212: 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
| geneva-stop-winding-stop-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=geneva-stop-winding-stop-mechanism
Fits with
Questions
How does a Geneva stop limit the number of turns?
A finger wheel with one pin indexes a five-position Maltese cross one position per turn, the locking disc holding the cross still in between (a Geneva drive). One of the five positions is not a slot but a convex tooth: when the pin comes round to it the tooth will not let it in, and the finger wheel is stopped — after four turns in one direction (and four back). Brown: used in Swiss watches to limit the winding; the convex curved portion of the star is the stop.
What is the difference between a Geneva drive and a Geneva stop?
The same wheel and cross; the stop has one slot replaced by a convex tooth, so the cross cannot go round and the driver is limited to n − 1 turns.