Original poster here. I thought you good people would find the Geneva drive interesting. It is so simple and elegant; similar in spirit to the elegance of a beautiful algorithm.
For further reading on the Geneva drive... don't miss the spherical Geneva drive design, illustrated in figure 9-3:
To be honest, at first I saw this post and thought, "how is a simple post of the Geneva drive mechanism news?". But after reading some of the followup and various links, I've definitley changed my opinion. Some amazing mechanical engineering in here. Thanks for this great video!
Yes thank you, posts like this are what make HN good. It's not necessarily news or even related to technology but interesting for us hacker types nonetheless.
Until you implement it at tiny scale using COTS integrated circuit technology or some semi-hypothetical individual atoms basis. MEMS chips are high tech.
Perhaps you could make a nano (well, micro) scale peristaltic pump out of a really small geneva linkage. Or gears for a little robot that floats in your bloodstream or something like that.
Thanks! For a moment there I was like "what the hell is this." But then I found the article fascinating and then I remembered, this is what HN is all about.
This is great. Thank you for posting this. I am looking to build an interactive display with intermittent rotation of objects, and couldn't think of a way to accomplish this efficiently without resorting to a software solution. This definitely solves it much better!
Such a nice hack. If you like this, you might be interested in "Five Hundred and Seven Mechanical Movements", freely available on google books [0], which I found on HN a couple of months ago.
Thanks for the link. I've had both 507 Mechanical Movements and 1800 Mechanical Movements for quite some time now. This seems like a great reference for mechanisms.
I met the Geneva drive when I was trained in servicing IBM 514 and 519 reproducing punches[1], in the mid-70s when these machines were on the way out. A 514 could reproduce a deck of punch cards[2] at 100 cards/minute. A punched card was fed from the "read hopper" and a blank one from the "punch hopper" and moved through the machine under steel feed rollers that were given intermittent rotation by a Geneva gear.
Driven by the Geneva, the feed rollers would move the cards the width of one of their 12 rows, then stop. On the read side, that row was under a gang of 80 little bronze wire brushes. On the punch side, the row was over a gang of 80 sharp little steel punches. When the cards stopped a pulse of current went through the brushes. If there was a hole in the card on the read side, current flowed on to one of 80 little solenoids. The solenoid would yank a bell-crank that pushed a punch through the blank card.
The punches withdrew, the Geneva swung its next lobe, and the cards advanced to the next row. Twelve rows per card, 100 c/m. It was quite noisy despite heavy sound insulation on the insides of the covers, a distinct brrruup, brrruup, brrruup overlaid with a general mechanical roar.
If you love both watch mechanisms and incredible feats of "traditional" machining, I highly recommend George Daniels' "Watchmaking." Not only is it a beautiful coffee table book but it takes the reader through modern (Swiss lever) mechanical watches all the way, from concepts to workshop design to machining to assembly. Even if you don't end up reading the whole thing the diagrams are wonderful to flip through over and over again.
While the article states that its name derives from an early use in mechanical watches, the modern mechanical watch is far more likely to use a deadbeat escapement for its intermittent motion. [1]
Hilarious. Sorry about that, obviously pasted completely the wrong buffer.
Your video is exactly the one I was going for, though potentially this [1] is a better quality version.
Thanks for the post. Watching that animation reminded what pleasure could be derived by just watching simple mechanism in action e.g. union joint, differential gear, rotary engine etc.
I can clearly remember the hypnotizing spell casted by the Lego differential gear on my 8year old brain. It lasted for weeks.... Come to think of it, I actually became an engineer....
Is there a drive that does the opposite? A drive that converts intermittent rotary motion to continuous rotation? I never studied this sort of thing in school, unfortunately.
Is there a drive that does the opposite? A drive that converts intermittent rotary motion to continuous rotation?
From the perspective of a mechanical watch, there is a component known as the mainspring. It is a spring that stores energy from either manual winding or automatic winding.
With manual winding, turning the watch's crown to wind the mainspring is an intermittent, rotary motion. Alternatively, with automatic winding, a rotary weight that moves intermittently (e.g., when the wearer's arm is moved) is used to wind the mainspring.
In either winding scenario, manual or automatic, the result is that intermittent, rotary motion causes energy to be stored in the mainspring, which is then subsequently available to provide for continuous rotation of the watch's mechanics.
I caught myself thinking along the lines of "of course it's not possible, that would be preposterous!", but as you say, a watch spring mechanism does exactly this.
google for "four bar linkage crank rocker" and you're gonna need a flywheel on the rotating side. For some definitions of intermittent rotary motion.
If you're ever bored, look at what four bar linkages can do. Stereotypical mech eng topic where its shocking just how many different things four chunks of metal and some bearings can achieve. A really poor analogy would be its kind of the turing machine of the mech eng world in that it can seemingly do almost anything with a minimal amount of parts.
There is an interesting scaling effect where the math for linkages scales pretty scarily as the number of bars increases.
(edited to add, and you can see an applied model in some stair stepper exercise machines where the arm actually moves thru an arc, which I guess is the intermittent rotary motion you're looking for?)
For intermittent motion to produce continuous motion, you need to store energy to have a supply of power for the lul when the input is not moving. Without energy storage, it is impossible to continue doing work on the output when the input is not moving. Does that make sense?
I think the key phrase is "intermittent rotary motion." The movement of the red wheel in the gif on Wikipedia is very unlike my legs powering a bicycle or a cars piston pumping up and down.
I would like to transfer the movement from the red wheel into the smooth continuous rotary movement of the green wheel.
A bicycle can work like an intermittent drive, though. The coast capability of the cassette, combined with your mass as a form of kinetic energy storage, means that you can alternate between pedaling and not pedaling while continuing to move.
Thank you for posting this. You've just thrown me back 20 years in time, when I was a young film projectionist in a cinema. The projector we had used this mechanism to flash the images on the celluloid at 24fps instead of one continuous stream of light.
I was also a projectionist and I had to rebuild intermittent movements a few times when we couldn't get a new one fast enough. I was the head projectionist for three years and we only lost one at a eight screen theater. But the theater across town that was owed by the same chain went through a few a month. But I also made sure the projector-head actually had oil in them and the other theater didn't seem to care.
If you liked this, you should love this series about vintage (analog) fire control computers: http://www.youtube.com/watch?v=_8aH-M3PzM0 (part 1; other parts in Youtube suggestions).
I was going to look those up and post them, but you beat me to it. Until I watched those videos some months back, I had no idea such mechanisms had ever existed.
I have a question about these kinds of drives. Don't these depend on the fact that no one is moving and wiggling the whole mechanism? It seems to me like if the red gear with the slots were to move just a bit out of the way, it'd mess up the entire mechanism.
The red gear is held in place via the axle, and isn't free to rotate because of the crescent shaped portion on the drive wheel. The spoke on the drive wheel catches the driven wheel before/simultaneous to the crescent rotating out of the way and freeing the driven wheel to move.
Oh wow, I see now. The green circular part pretty much locks the crescent and thus the red gear into place. That's why there is a gap in the circular part where the gear is supposed to turn. Thanks!
I would love to learn about clockwork - even if only using CAD (although actually getting to make something would be even better) - however have been unable to find any resources for learning about it. Does anyone know of any good guides for introducing horology/clockwork manufacturing to beginners and explaining how to get started?
Its kind of big, like "teach me about computers". You can learn a lot from practical applications. I find these blueprints and finished clocks extremely aesthetically pleasing and instructive:
I have no connection other than owning some of the plans and very slowly in the process of building one of the simplest clocks, one with a classic Verge escapement. I wanted specifically to build a retro Verge escapement and I don't know enough to advise if that's the best choice for a noob, unless you've also got a bug to build a Verge...
If you're willing to spend a ridiculous amount of money (like $1 per page!) "My own right time" by Philip Woodward could be a reasonable book to start. Borrow it at the library or interlibrary loan. One thing I learned from the book is the spouses of time nuts are apparently at least as tolerant as the spouses of ham radio and computer nuts (which is saying a heck of a lot).
This is an area where I know enough, to know I only know enough to be dangerous, so if anyone has better information they should respond.
(Edited to add I would consider clockmaking to be a separate craft from metal machining or wood butchering or 3d printing and would not advise trying to learn both at the same time, unless you're very patient. I think learning fine woodworking and clockmaking at the same time would be highly challenging. Or machining and clockmaking, etc.)
Another interesting property is that unlike a regular pair of meshed gears, this can only transfer power in one direction. Swapping the input and output shafts won't work.
For further reading on the Geneva drive... don't miss the spherical Geneva drive design, illustrated in figure 9-3:
http://ebooks.library.cornell.edu/k/kmoddl/pdf/002_010.pdf
Although not Geneva drive related, if you want to combine your passion of horology with human spaceflight, you will truly enjoy "John Glenn's Heuer":
http://www.onthedash.com/docs/Glenn.html
Also, thank you all for the great, related links!