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Antikythera Mechanism

A question about manufacture

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Dave Halford19/11/2021 16:45:07
2536 forum posts
24 photos

Has anyone on here ever drawn bronze wire down to 0.3mm if so how strong was it?

ega19/11/2021 23:36:50
2805 forum posts
219 photos

SOD:

Isn't the time on the Smiths timer witnessed by the notch at the 12 o'clock position?

david bennett 819/11/2021 23:58:27
245 forum posts
19 photos
Posted by SillyOldDuffer on 19/11/2021 15:32:03:

This Smiths Timer reminded me of the Antikythera ring:

dsc06542.jpg

A pin in the lower ring flips a microswitch on, while a pin in the outer ring flips it off. 96 holes divide a 24 hour cycle into 15 minute segments. Much less challenging to make the ring than that on the Antikythera device. Setting the timer is a little fiddly, and I think the holes are about as close as they can be for ordinary fat fingered folk.

Struck me the Smiths pins have two separate functions: they drive a switch and they indicate the time. Possibly the Antikythera does similar. I think the Antikythera pins are too small and weak to drive gears or move the ring. Therefore I suggest the holes are intended to hold indicator pins. A pin might be inserted to indicate 'new moon today', after which cranking the device would move the ring and pin to show the dates on which future new moons occur. This movement might be relative to the Egyptian Civil Calender marked on the dial, and maybe one of the mechanism's functions is to convert lunar time into solar. For example: If tonight is the second new moon of the year in Athens (Lunar), how many days are there until the 23rd of Renwet in Thebes (Solar)?

Dave

Dave, there seems to be a misunderstanding of the Mechanism (which made me think I was missing something) As I understand it, none of the dials or hole rings move when the thing is cranked. All that happens is that the related "pointers"move - except the calendar dial is manually moveable for adjustment.

dave8

Edited By david bennett 8 on 20/11/2021 00:16:46

Edited By david bennett 8 on 20/11/2021 00:18:21

david bennett 821/11/2021 02:18:59
245 forum posts
19 photos
Posted by Michael Gilligan on 12/11/2021 08:31:48:
Posted by david bennett 8 on 12/11/2021 01:34:38:
.
 
We now know the actual solar year is 365.24 days. Over 4 years the error would be 0.96 days.

.

Alternatively; using Hipparchus’s figure, it would be 0.98668

… pick a number !

MichaelG.

I did pick a number - I chose todays results to compare with the AM designers figures . (I know this is a late reply, but I have just been re-reading the posts)

dave8

 

Edited By david bennett 8 on 21/11/2021 02:19:54

Edited By david bennett 8 on 21/11/2021 02:22:48

Michael Gilligan21/11/2021 07:44:53
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23121 forum posts
1360 photos
Posted by david bennett 8 on 21/11/2021 02:18:59:
Posted by Michael Gilligan on 12/11/2021 08:31:48:
Posted by david bennett 8 on 12/11/2021 01:34:38:
.
 
We now know the actual solar year is 365.24 days. Over 4 years the error would be 0.96 days.

.

Alternatively; using Hipparchus’s figure, it would be 0.98668

… pick a number !

MichaelG.

I did pick a number - I chose todays results to compare with the AM designers figures . (I know this is a late reply, but I have just been re-reading the posts)

dave8

.

Sorry, Dave … I honestly don’t understand the logic of your choice.

[ mostly because you started with a false premise ]

MichaelG.

.

P.S. __ If you really want to labour this [which I do not think is really appropriate] … you might find this interesting : 

https://www.hermetic.ch/cal_stud/cassidy/err_trop.htm

Edited By Michael Gilligan on 21/11/2021 07:57:22

david bennett 821/11/2021 15:02:35
245 forum posts
19 photos

Michael G, I also do not wish to labour the point, but I would be interested ro know my false premise, and I doubt the extra decimal points would be relevant to a mechanism like this .

dave8

Michael Gilligan21/11/2021 17:36:44
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23121 forum posts
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Posted by david bennett 8 on 21/11/2021 15:02:35:

Michael G, I also do not wish to labour the point, but I would be interested ro know my false premise, and I doubt the extra decimal points would be relevant to a mechanism like this .

dave8

.

O.K. Dave

You clearly stated, with [it appeared] some confidence:

"We now know the actual solar year is 365.24 days. Over 4 years the error would be 0.96 days."

... but that is, in fact, quite contrary to what "we now know"

What we do know is that the solar year varies from place to place and from time to time.

That's what I was hinting-at when I wrote:

"... pick a number"

.

I do agree that additional decimal places are likely irrelevant to the construction of the mechanism ... but if we were to use anything for 'reverse engineering' , then Hipparchus’s figure would be near-contemporaneous and [rounded to two decimals] gives 0.99 rather than 0.96

MichaelG.

david bennett 821/11/2021 20:16:48
245 forum posts
19 photos

Michael, thanks for your views. Finally, what in your opnion is the purpose of the ring of holes?

dave8

Michael Gilligan21/11/2021 20:28:03
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23121 forum posts
1360 photos
Posted by david bennett 8 on 21/11/2021 20:16:48:

Michael, thanks for your views. Finally, what in your opnion is the purpose of the ring of holes?

dave8

.

Until we can be more confident of the number of holes in the full circle, I am content to remain agnostic

MichaelG.

.

Ref. __ https://www.merriam-webster.com/dictionary/agnostic

Edited By Michael Gilligan on 21/11/2021 20:28:47

david bennett 823/11/2021 00:37:45
245 forum posts
19 photos

As a general comment,to summarise, a solar dial with a 365.25 geared pointer, would give a very accurate leap-year correction by advancing  the year dial  one hole  in a 354 hole ring every 4 years.

dave8

Edited By david bennett 8 on 23/11/2021 00:38:52

Edited By david bennett 8 on 23/11/2021 00:43:55

Edited By david bennett 8 on 23/11/2021 00:46:28

Edited By david bennett 8 on 23/11/2021 00:51:43

david bennett 823/11/2021 02:10:46
245 forum posts
19 photos
Posted by david bennett 8 on 23/11/2021 00:37:45:

Sorry the above post should have read - "As a general comment,to summarise, a solar dial with a 365.geared pointer, would give a very accurate leap-year correction by retarding the year dial one hole in a 354 hole ring every 4 years."  (I must stop posting so late)

dave8

 

dave8

 

Edited By david bennett 8 on 23/11/2021 02:38:30

Edited By david bennett 8 on 23/11/2021 02:43:29

Michael Gilligan23/11/2021 06:51:40
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23121 forum posts
1360 photos
Posted by david bennett 8 on 23/11/2021 02:10:46:
Posted by david bennett 8 on 23/11/2021 00:37:45:

Sorry the above post should have read - "As a general comment,to summarise, a solar dial with a 365.geared pointer, would give a very accurate leap-year correction by retarding the year dial one hole in a 354 hole ring every 4 years." (I must stop posting so late)

.

354/365 = 0.97 [rounded to two decimal places] yes

’though the favoured Metonic explanation also makes good use of 354

MichaelG.

.

Ref. __ https://www.scientificamerican.com/article/antikythera-mechanism-eclipse-olympics/

… as one digestible source

Ref. __ https://www.google.co.uk/url?sa=t&rct=j&q=&esrc=s&source=web&cd=&ved=2ahUKEwjn6fne7630AhXGUMAKHSmJBuYQFnoECB8QAQ&url=https%3A%2F%2Fosf.io%2Fpreprints%2Fsocarxiv%2Ffzp8u%2Fdownload&usg=AOvVaw2Hf3gjn3t2ysykR9uvvn_G

… should [hopefully] link to a recent ‘preprint’

Edited By Michael Gilligan on 23/11/2021 07:13:01

John McNamara23/11/2021 10:24:43
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1377 forum posts
133 photos

Good find Michael G

From the first Scientific American link you posted.
If this image is from the Antikythera find it appears to show a larger fragment. Maybe it is an assembly of found pieces? However even if it is it may enable a more precise centre point to be derived, Even if just a "feature" arc is used if the holes are not visible. it might improve the accuracy of the calculations for the hole circle. By knowing the radius of a feature arc and then measuring the distance from the feature arc to the hole circle arc, a more accurate radius for the hole circle might be obtained. I firmly believe that the mechanism was accurately made with true concentric circles.

Maybe there is a better copy of this image available?

antikythera l.jpg

Slideshow Link

Regards
John

Michael Gilligan05/12/2021 18:22:30
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23121 forum posts
1360 photos

[ posted in error … I will try again later ]

blush MichaelG.

Edited By Michael Gilligan on 05/12/2021 18:52:08

david bennett 806/12/2021 17:21:05
245 forum posts
19 photos

John,I too believe the dials were made truly circular, but when they were broken, distortion of their circularity is likely due to the release of locked in stresses. A cast bronze ring, possibly quenched, probably hammered to harden and refine the structure, then machined, would have severe internal stess. 350+ holes in the calendar ring backing plate would add to it. When such a ring is broken, the apparent original center would be in doubt. (I cannot find any data relating to this stress release distortion) ( then there's the problem of centuries of sea-water corrosion)

dave8

Edited By david bennett 8 on 06/12/2021 17:22:07

Edited By david bennett 8 on 06/12/2021 17:31:07

Neil Lickfold08/01/2022 09:01:05
1025 forum posts
204 photos

This guy Chris has made one. Just delete if his YT channel has been linked before. He has done a good job of recreating tools etc to make it al happen, apart from using sheet material it seems. I found it interesting and the precision possible with such basic hand tools.

https://www.youtube.com/c/Clickspring/videos

Some newer data, 

https://www.youtube.com/watch?v=MkKgdq57uOo

https://bhi.co.uk/antikytheramechanism/

Edited By Neil Lickfold on 08/01/2022 09:11:49

Michael Gilligan08/01/2022 09:11:25
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23121 forum posts
1360 photos

For info. Neil

That guy Chris is one of the authors of the paper which is being discussed.

MichaelG.

Neil Lickfold08/01/2022 09:12:45
1025 forum posts
204 photos

Thanks Michael, If my posting is not needed, then it should be deleted.

Michael Gilligan08/01/2022 09:18:23
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23121 forum posts
1360 photos

Eight pages into a complex thread, Neil

… I would say your reference is well worth keeping, for the benefit of new readers.

MichaelG.

Swarf Maker09/01/2022 19:08:40
132 forum posts
7 photos

I have just found this article in 'Scientific American'. Apologies if this has been linked to before.

https://www.scientificamerican.com/article/an-ancient-greek-astronomical-calculation-machine-reveals-new-secrets/

Scientific American

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