Talk:Geneva drive

older entries

Perhaps this picture helps

This is a wonderfull, amazing, article! Thank you so much! David G Brault 21:21, 28 June 2006 (UTC)

I agree. Very interesting article. 66.150.62.145 17:42, 13 July 2006 (UTC)

While a very interesting article -- this ranks up there with the square drill bit for me :) -- I find the paragraph on internal Geneva drives quite confusingly worded. Could someone with insight have a go at restating it for the terminally dumb ;) --Turbothy 00:31, 23 December 2006 (UTC)

Don't we

have to separate the Maltese Cross which like every cross always has four arms from the more general term Star Wheel that may be three- or five-armed, and so on ? Filmtechniker--80.219.134.244 (talk) 09:06, 12 October 2008 (UTC)

10,000 Year Clock

Not up for editing the article myself, but the 10,000 year clock project has some fantastic examples of the Geneva Drive principle: http://longnow.org/clock/chimes/ :) 194.176.105.151 (talk) 16:17, 1 August 2011 (UTC)

Internal Geneva Drive

I'd say the most important difference is that the (depicted) internal version has no locking function between steps, or has it? This might be an issue for many applications. However, this could obviously be solved, so it might be just a problem for the selected wiki animation? --79.214.39.237 (talk) 16:32, 25 August 2013 (UTC)

The main difference is in the ratio between moving/stationary times. External Genevas are much more common because they have the (often useful) effect of this "snap" action.

Neither really has much of a useful locking action. Any force back through the drive will jam them, rather than act as a useful brake. Andy Dingley (talk) 17:14, 25 August 2013 (UTC)

Additional Applications

Geneva mechanisms are also used for precision object placement throughout extreme temperature ranges. They are used within cryogenic temperature chambers to rotate precision apertures into and out of position. — Preceding unsigned comment added by 174.18.113.149 (talk) 18:06, 8 October 2013 (UTC)

File:Geneva mechanism 6spoke animation.gif to appear as POTD

Hello! This is a note to let the editors of this article know that File:Geneva mechanism 6spoke animation.gif will be appearing as picture of the day on June 3, 2015. You can view and edit the POTD blurb at Template:POTD/2015-06-03. If this article needs any attention or maintenance, it would be preferable if that could be done before its appearance on the Main Page. Thanks! — Crisco 1492 (talk) 00:45, 15 May 2015 (UTC)

Picture of the day

The Geneva drive is a gear mechanism that translates a continuous rotation into an intermittent rotary motion. The rotating drive wheel has a pin that reaches into a slot of the driven wheel advancing it by one step. The drive wheel also has a raised circular blocking disc that locks the driven wheel in position between steps. Such a mechanism is used in film projectors, watches, and indexing tables, among others.Animation: Mike1024

angle of rotation

Forgive me if I just don't get it, but: The internal section says "The angle by which the drive wheel has to rotate to effect one step rotation of the driven wheel is always smaller than 180° in an external Geneva drive and always greater than 180° in an internal one" - it looks like 360 degrees in both the animations (external and internal), to me. So I have no idea why it says this, or what it could mean if not what I think it means. 110.20.168.169 (talk) 23:52, 17 June 2016 (UTC)

It's correct, although could be clearer.

A geneva wheel isn't a simple gear ratio, even though it has a gearing-down effect for speed. It's main characteristic is that the riven wheel is stationary for some of the cycle and moves in intermittent steps - for all of them, the driving wheel makes one complete revolution to turn the driven wheel by a step. The statement here is about the proportion of 360º rotation of the driving wheel for which it's turning the driven wheel, and how much is ineffectual (i.e. no driven rotation happening).

For the external geneva, the movement phase is always less than 180º (short moves and long gaps), for the internal geneva it's always long moving phase and short gap. Andy Dingley (talk) 01:18, 18 June 2016 (UTC)

Ohh hehe thank you! :-) So given that it means that, perhaps "The angle by which the drive wheel has to rotate to effect one step rotation of the driven wheel" isn't a good way of saying that? That phrase still sounds like me to mean.. uh what it literally means. 360 deg. Well, you're the expert, but for me, (and well, WP should be written by experts for laymen/noobs!) something like 'The driven wheel of an external drive is stationary most of the time" etc would be infinitely clearer. Thanks again; that was just baffling. 110.20.168.169 (talk) 07:29, 22 June 2016 (UTC)

Formula Please!!!

This article lacks the information required to design one. A suggested source with overlays is here. And one is animated here. Note that a 2 position wheel is not possible because a circle does not have a 180° angle on it, and the peg needs to hit a wall. — Preceding unsigned comment added by Charlieb000 (talk • contribs) 01:27, 18 June 2016 (UTC)

There's no "formula" as such. It's a simple combination of radial slots and arcs centred on the driving wheel. Andy Dingley (talk) 01:34, 18 June 2016 (UTC)

Please read my “suggested source”. The design is more complex than you would assume. Some people do not like trial and error (While i was ignorant, the one i designed would not rotate properly because the arc in the rotor would rotate into the cross as it turned - because the bars on either side of the slots were flared too wide. Then I realised that the shafts more than likely need to be a certain distance apart, so I hunted for formulas.) And to correct you, there are seven formulas.Charlieb000 (talk) 01:52, 18 June 2016 (UTC)

That's rather the problem. As there is no single formula for this (if there was, the maths would be unpleasantly discontinuous) it's stated instead as a set of separate conditions. If you want to express the design constraints, then the right-angled triangle might be the clearest way to express these, rather than some formula. It shows the need for the pin to engage with the slot in a purely radial direction, it also makes the limit on slot depth needed quite easy to see. Personally though I've always found them pretty easy to design (I laser cut stuff and make automata). Andy Dingley (talk) 08:07, 18 June 2016 (UTC)