Antikythera mechanism

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Mechanism Man

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I'm sure that most of you good folks here have far better things to be doing than worrying about ancient Greek artifacts, and not many of you will be particularly familiar with the Antikythera Mechanism, and that's if you've ever heard of it at all.
So, for those not sad and lonely enough to know what I'm talking about, or for those that only have a vague recollection of this incredible device, it was, in a nutshell, a machine the size of a shoe box discovered 114 years ago in a 2100 year old Greek ship wreck that could accurately predict where in the heavens to look for all the major heavenly bodies known at the time. It included the apparent backward movement in the night sky - retrograde motion - for all the planets (the machine represents what can be seen looking out from Earth, rather than being a birds eye view of the galaxy like a traditional orrery), and it even went as far as showing the apparent speeding up and slowing down of the Moon's orbit. It's predictions were depicted on both sides of the box by pointers for the five known planets of the time (and of course the Sun and moon), and with time being measured on the opposite side with a spiral scale that spanned 235 months, after which time the pointer on this scale would have to be reset to month one again. Other pointers predicted likely eclipses, moon phases and measures of time. All this pre-dated the first gear driven clock by over 1000 years. Put simply, it was an incredible feat of engineering for it's time.
So why am I rambling on about it you may ask? Well after building many orreries over the past few years - all with scroll saw cut wooden gearing - I've finally got around to having a go at building one of these amazing machines myself, and again, it's being built with hand cut wooden gears. All the gearing has been worked out by minds far greater than mine, so with a little luck I shouldn't encounter too many problems, but if I pull it off I'll be the first person to actually physically build one of these devices with all the latest thinking rather than just computer model it for 2000 years - so I really hope that it works!
I'm not sure if anybody here will be particularly interested, but I thought I'd share my efforts anyhow, just in case.
I'll attach a photo or two tomorrow.
Dave.
 
Mechanism Man":13bt2mq1 said:
....if I pull it off I'll be the first person to actually physically build one of these devices with all the latest thinking rather than just computer model it for 2000 years - so I really hope that it works!

Lots of details on the web, including proposed gear layouts and the wikipedia page has a reproduction photo from a 2007 model - not quite sure you will be the first to build one for 2000 years I am afraid.

http://en.wikipedia.org/wiki/Antikythera_mechanism

While it was indeed technologically astounding for its time, it appears that it was built assuming planets had circular rather than elliptical orbits and so wasn't particularly accurate!

Would be interested to see pics of your build - are you building it as a 1:1 scale replica or larger?

Steve
 
StevieB":5z1scrdy said:
While it was indeed technologically astounding for its time, it appears that it was built assuming planets had circular rather than elliptical orbits and so wasn't particularly accurate!

Steve

Yes it took nearly 2 millennia for Johannes Kepler to formalise his theory of elliptical orbits, and a couple of centuries thereafter for Albert Einstein to refine it further. So the Greeks weren't doing bad.
 
Welcome and best of luck with your project , I for one will be watching your posts and finding out about something I have never heard about before .
 
Absolutely interested.

I make wooden clocks (with wooden movements - and yes, sometimes they wouldn't go) - and I'm repairing one now. I've posted a couple of WIPs here, of wooden animations I've done. Mostly I use the plans from a guy in Hawaii (http://www.lisaboyer.com/Claytonsite/Claytonsite1.htm).

Please post a WIP, and do it as you go. As people have said to me here, its fun seeing the process, and the mistakes and bodges as well as when things go right first time (HA!).

I to am wondering about scale. 3 times? I can't believe you will be able to cut small enough teeth to be much smaller that that (even using home made ply from sandwiched vaneer, I couldn't go very small).

Very best of luck.
 
Evening chaps,

Thought that I'd better come back and add a bit more having started this off.

You are quite right in saying that my machine will not be the first, but it will be the first to include this method of gearing for the planet drive system. Up until about two years ago nobody really knew how the original designer included the gearing for the 5 known planets at the time, mainly because the gearing for this section of the machine was simply lost and not recovered from the ship wreck. All the machines built so far (there are only about five anywhere in the world) have either missed out the planet gearing all together, or else the solution had been cumbersome at best. The latest research has produced an entirely new gear train which is elegant, 'blimmin clever, and actually fits within the known available space in the original machine and follows the techniques used throughout the rest of the mechanism. However, the new gearing has never actually been built - until now!

As for the accuracy, well the Ancient Greeks did indeed believe that the Earth was the centre of the solar system (apparently it's not), and yes, they also thought that the planets (and the Sun) move around the Earth in circular orbits (erm, they don't), so on the face of it they were never going to produce an accurate machine to predict anything because they had no idea how the solar system actually worked. So why does it? In short, it made no difference that they had got it all wrong, because the machine was simply based on 500 years of physical observations. They thought that at certain times the planets actually stopped and moved backwards in the heavens (we now call in retrograde motion), so that's what they modeled - the machine simply reflects what can be seen looking out from Earth - and it does it really accurately, irrespective of how the planets are really moving. The machine really doesn't care if the orbits are round, elliptical, or even square, it just shows what's going to happen without any real understanding of how it actually how it happens. If you really want to know why the Greeks thought that the planets speed up and show down, Google the word 'Epicycle' - it's all clear as mud...

Apparently I have to post four times before I can link to my photos in Photobucket, so I shall carry this on in another post....
 
As for the scale of my version, it's just over one and a half times bigger than the original, and even then it's not very big. Some of the gears only have a pitch of 2.4mm, so from a scroll saw point of view you have to be a bit switched on and be concentrating when chopping up the gearing, but it seems to be working out ok so far with everything meshing as it should be.
It's stretched me mentally quite a bit - I'm not used to actually thinking, especially since there are no proper plans to follow, so with the exception of the all important gear wheel counts, I'm having to make it up as I go along. I just hope that I can do it justice...
Right, by my reckoning, I should be able to post some photos now that I've made the posts... I hope...
So, here are the first few progress shots of the machine up 'till now. This represents about one month of work I guess, so it's not quick, but I'm getting there. Some of it needs to be re cut (the frames mainly), but it works so far at least. The photos show just the mechanism for the planet and sun pointers. This whole assembly will slowly rotate with the gears gently spinning within it, it should look great when it's done. The rest of the machine has yet to be started, so there is still lots to do - but at least I'm moving in the right direction!

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Just in case you all thought that I'd gotten bored and given up, well I'm still here and beavering away, I just haven't got anything solid to show you. Progress is still good, but I just had a little bit of a two steps back to make one step forward situation to get through before starting the next unit.
After having a good play with the machine as it stood in the last photo, I came to the conclusion that although the gear work was all fine, the frames were just not good enough.
Unfortunately, when I first fitted the gearing to the frame work, I got myself very confused as to which gear went where and so drilled a few holes that should never have been drilled. I could fill these, but they would always be visible, and if the jobs worth doing...
More important than that though, I also didn't leave enough material to fit decent size spacer poles, my preference is for 6 mm wooden dowels, rather than the 3mm metal rods currently fitted which was all I had room for at the time - changing them will make fixing everything together so much easier.
Lastly, the purpose of the gear teeth running around the outside of the bottom frame is to provide the main input drive for the entire machine via the winding handle. I've decided to lose this in favour of a smaller gear that will be driven by a worm gear - both to be fitted later - so all three new frames can have smooth edges.
So while it's still at a relatively early stage in the build I have opted to cut three new frames and re-fit the existing gearing to them instead, it's a bit of re-work that's worth doing I think.
I'll hopefully have this all finished in the next day or two, and this time I'm staining and varnishing the bits that require it, as well as fixing all the gearing in properly so that I'll end up with the first properly finished unit.
That's the plan anyhow...

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Slightly beefier frame design before cutting.
 
That's truly great!

Can I ask - how did you choose the thickness of the gears? - they're thicker than is "obvious", and given your experience
I'm sure you didn't just guess.

BugBear
 
I watched the film 'hugo' the other week- this project instantly made me think of it . I admire your patience ;)
 
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