Antikythera mechanism

A place to hang out and chat about astronomy

Re: Antikythera mechanism

Postby minimoa69 » Thu Oct 23, 2014 11:20 pm

After much pondering, head scratching and general dithering, I've now got the the next steps firmly fixed in my head and today has seen me cut out the two remaining frames that will house the gearing for the three superior planets. These two new frames will be fixed with rods to the great big gear (currently shown in the photo without its inferior planet gearing fitted) and they will slowly rotate with it, with all the planetary gearing being caged within these three rotating layers - and all the gears in turn will be humming away themselves as the are pulled around by the cage - it should look great when it's all done!  
I'm hoping to get all this test assembled over the next few days if all goes to plan, when the new photos will hopefully make more sense to you all!
More soon.

Image

Edit - the middle frame will be replacing the little triangular frame in the previous photos - I hadn't realised that this frame also doubled up as somewhere to fix the pivot points for some of the new gearing, so it needed to be much bigger. Another easy fix thank goodness!
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Re: Antikythera mechanism

Postby minimoa69 » Sun Oct 26, 2014 8:31 pm

Evening all,
Well I think that I've cracked it - or at least the first part anyway.
So, here are some photos of the first unit all put together and, more or less, working!
One of Saturn's gear pairs only meshes when it wants to at the moment, but that's mainly down to the fact that central core of tubes is only held at one point at the moment so the other end is free to move about a bit which pulls the gears out of position. Hopefully when the rest of the framework is built everything will be caged and held in its proper position and it'll all work beautifully... hopefully being the operative word.
As far as I can tell this is the first time that this part of the machine has ever been physically built to this design - it's been computer modelled and depicted several times but never actually built. All the other physical versions of the machine have been built to much earlier thinking, so it's a bit of a relief to see it actually working on the flesh, so to speak.
More soon.
:-)

Image

Image

Image
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Re: Antikythera mechanism

Postby dave.b » Tue Oct 28, 2014 11:46 pm

Looking good - unbelievably good in fact!

How about a quick video of mechanism turning?

BTW are the designs for this version of machine in the public domain?

Dave B.
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Re: Antikythera mechanism

Postby minimoa69 » Thu Oct 30, 2014 12:31 pm

Hi Dave,

Thanks for the kind comments - it's a really fun project to do. Once I've got it to a point where it's all working as I want it to I'll certainly start posting some videos of it doing it's thing - although at the moment the subtleties of the movement of gearing is a little hard to see even when it's sat in your hand, let alone in a video clip! However, I will do my best for you.

The schematics and gear wheel counts are out there in various published public domain papers, and even Wikipedia has recently been updated with the latest gear schematics - so it's not difficult to get the information, but as for proper plans, they don't yet exist, so there is still a fair amount of design to do which keeps things from getting boring. It would be no fun if somebody had already built one to the same design!
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Re: Antikythera mechanism

Postby minimoa69 » Tue Nov 04, 2014 11:26 pm

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...

Image
Slightly beefier frame design before cutting.
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Re: Antikythera mechanism

Postby minimoa69 » Mon Dec 01, 2014 12:15 am

Sorry for the lack of progress on this recently - unfortunately work, life, other projects and Christmas are all getting in the way at the moment, hopefully normal service will resume very soon!
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Re: Antikythera mechanism

Postby minimoa69 » Sat Feb 28, 2015 10:14 pm

Okay, I've been away for far too long so I guess it's high time for an update.
So, after a very busy and turbulent mid winter I've finally finished the rebuild of the first unit containing all the gearing for the planet pointer side of the machine.
The photos show this new version of the machine sporting it's final colour scheme. This frame and gear colour combination will follow through the rest of the build. It works great apart from a little binding between two of the gears which I will fix in about 10 minutes!
Bye for now ladies and gents - more soon.
:-)

Image

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Image
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Re: Antikythera mechanism

Postby dave.b » Sat Feb 28, 2015 10:36 pm

Looks fantastic!

What do you mean by "rebuild"? As drastic as start again? The outer frame looks different from last October's pictures.
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Re: Antikythera mechanism

Postby minimoa69 » Sat Feb 28, 2015 11:05 pm

No - nothing as drastic as starting from scratch. All the gearing and maths was good, but the frames were, well, a bit rubbish to be honest. The only answer was to recut them and then refit the existing gearing. Took a little longer than planned but was a job with doing. Is fascinating to see it working properly now with the backward and forward motion of some the gear outputs as the machine replicates the retrograde motion of the planets. I'm now trying to get it mounted in a frame so that I can film it doing it's thing, so to speak - it's a little hard to handle as it is at the moment.
I'm off to an early evening talk on the original machine in Oxford on Wednesday, not sure whether or not to take along what I've built so far - probably best to wait till it's finished I guess.
Right - more very soon!
:-)
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Re: Antikythera mechanism

Postby minimoa69 » Sun Mar 08, 2015 5:02 pm

Hi folks,
I finally got around to putting what I've built so far into a temporary frame so that I could take a short and rather wobbly film of it working.
So attached is a YouTube link to the 95% complete planet mechanism unit.

http://youtu.be/G60GOw5FCUw

The cocktail stick pointers are purely there to show that the output from the gearing does indeed show the planets retrograde motions as the years go by.

The two pointers that appear to rotate together at a constant speed are the date and the sun - the sun pointer appears to speed up and slow down slightly as the months go by - just as the sun does in reality, so it's position will sometimes be slightly ahead of the date pointer, and sometimes slightly behind. So the date pointer is really the mean average position of the sun if it's motion was constant.

There's a little tinkering to be done to a couple of the gears to iron out a little binding, but other than that it's looking pretty good.

More soon.
:-)
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