The Antikythera Mechanism Episode 8 – Making The Mean Lunar Sidereal Train


after many generations of watching the
night sky it was clear to the ancient observers that there was an underlying
order and structure to the cosmos in addition to the cycle of night and
day and the phases of the Moon when measured against the background of stars
they found that the objects they were watching had a repeatable and
predictable motion and a good example of this is the motion of the moon if an
observation is made when the moon is adjacent to a prominent star then when
it returns to that star an interval of time can be calculated this is known as
its side aerial period or in the case of the moon we simply call it the side
aerial month now the ancients were well aware that this was merely an average
representation of the time interval they might not have had our modern
understanding of exactly why it was so but they certainly knew that the moon
sped up and then slowed down during its trip back to the same reference point
and that even that small oscillation was itself continuously moving throughout
each cycle it’s perhaps the most remarkable aspect of the device that
such subtle observations were mechanically represented within its
keyring and it began with the calculation of the mean lunar side
aerial month as a further resonance of the metonic cycle it so happens that 254
sidereal months also almost exactly equals 19 solar years so much like the
metonic gearing the side aerial period of the Moon can be given a convenient
mathematical expression now of course many aspects of this machine were
pushing the engineering limits of the day at this part of the train in
particular takes it closer to the edge than the rest and it’s those engineering
limitations that I’d like to go through now
to begin with the gearing rapidly steps up in this part of the train demanding
relatively fast rotations from assemblies with considerable inertia and
this puts a heavy load on some very small components for the most part the
high loads are dealt with in the same manner as the rest of the mechanism
square arbors fitting into square holes well peened in the position but the
teeth are at their greatest risk of damage in this part of the train and
there’s no better example of the material limitations experienced in the
mechanism much like the EM assembly the D assembly
must be capable of removal from the main plate
additionally the maker elected to run at flush against the underside of the
assembly platform and in so doing created the requirement that the D
assembly be fastened with a recessed retaining pin now you’ll have noticed that the wheels
and pinions in the mechanism are quite thin in most cases between one and two
millimeters thick and they obviously need to stay well meshed to function
correctly in modern clock making the meshing is ensured by setting a limiting
end shake with the pivot shoulders and to some extent by using relatively long
pinions that can tolerate a small amount of longitudinal shift between the
components but the sleek design of this machine rules out the option of using
longer pinions and the concept of shouldered pivots had apparently not yet
been invented generally the issue was solved by allowing a small clearance on
the inside of the arbors a bit like a simple axle it provides the required
limits to the movement at the cost of a higher friction penalty a good example
is the way that the EM assembly was fabricated
but in this higher load section of the train the maker discovered that method
was unsuitable and was forced to come up with a more reliable solution it shares
some of the features of a modern bridge but it might be more correctly described
as a sort of thrust plate that captures the small pinion while still permitting
its free rotation whatever you choose to call it it performs almost exactly the
same function as the shoulder of a modern pivot albeit with more friction
locking the longitudinal travel of the assembly and ensuring a very limited and
precise end shape but as effective as this idea is it still leaves one part of
the problem unsolved a natural limitation of the larger wheels due in
part to the simple square seating is the tendency for them to very slightly tilt
out of the horizontal plane for the low load assemblies this isn’t really an
issue but for the high loads in this part of the train and elsewhere in the
mechanism like the main solar drive wheel this dramatically affects their
efficiency and at worst can quickly lead to them becoming damaged so it was clear
that they required stabilisation and for that the maker came up with the
idea of these small stabilizing strips known as curves carefully set to the
correct height they acted as a guiding surface that limited the extent to which
the wheels could twist out of alignment now as it happens there’s an interesting
combination of methods used to fasten these curves to the main plate some are
fastened as you’ve seen here using pins but others were soft soldered into
position and that’s a process that I figured was worth looking at in more
detail so be sure to check out that video if you haven’t already done so the
stud for the SI assembly is the final component to be fabricated for this part
of the train with a small notch file to provide clearance with a d’ assembly hub
and a pin used to maintain its orientation with the main plate and I should also mention that there are
two final curbs to install underneath the main solar drive wheel that if
installed now would partly obscure the internal view of the mechanism so I’ve
decided to hold off fixing those until a later stage of the build in any event
has unorthodox as the solution appears the curbs turned out to be quite
effective the friction penalty has certainly increased but it is quite
acceptable and importantly the objective has been achieved because the assemblies
are now constrained into their operating planes as required to the extent that
the tiny wheel known as e 2 which is now rotating at the mean side aerial period
of the moon is now a reliable input to the next part of the mechanism the
epicyclic been and slight gearing thanks for watching I’ll see you later you

100 thoughts on “The Antikythera Mechanism Episode 8 – Making The Mean Lunar Sidereal Train

  1. Another amazing video! I always get excited when I check YouTube and see something from you! I would love to start in this hobby and was wondering if you would ever make a 'beginners tools to clockmaking' style video? Or even a small side series showing what tools a beginner should get in your opinion and how to properly use them. Maybe even something that provides information on different metal options for making different clocks? Pro's and con's of different materials! Thank you so much for the hours of entertainment!

  2. Perhaps a stupid question, but are the moving parts going to be lubricated in some way in the final assembly? Just wondering if they would have done that in the ancient times or not?

  3. Like a Holiday for me ) Enjoying your videos, and cannot wait for last one, when everything will be set in place and you will test it. ))

  4. I watched all 8 videos this weekend! just incredible detail and was still shaking my head in amazement in this episode at the tolerances you achieve with hand tools…

  5. Amazing work as always, Chris. I loved your soldering video, too. I'm just hoping I don't have to wait half a year for the next video!

    I understand life is a bitch, though, so don't take me too seriously; I'm only joking around.

  6. It's unlikely that the mechanism was a machine that was just created…may be there were much more simpler machines that were then evolved in to this…

  7. Truly nice Chris, it is so lovely to see it coming up! Your explanations are some of the best I have seen and your workmanship is totally unique! Please keep it up!

  8. Nice👍, quick question, after you peen your pins then sand or file them down so smooth I don’t understand what’s left to hold the part, can’t it just back out of the piece? Thanks

  9. Oh man, this is hypnotic to watch. Even though I have little understanding of how the mechanism as a whole works, I'm still delighted to watch how everything comes together. I can't wait to see this beautiful project completed!

  10. Fascinating watching you carry out your intricate work and listening to your dialogue and references to some astronomical terms a real pleasure ,and a very patient skilled craftsmen ,nice work and detailed video footage ,thank you for sharing ,best wishes Ron.

  11. Sometimes I go on YouTube and think "I bet I could do that if I had tools like those," then there's stuff like this, where I doubt I can do that with the tools I do have, but it reminds me of when I was starting out building stuff. I didn't so much as have a vise, and I made things work. Clickspring, you are an inspiration to so many. I hope someday I will be half the craftsman you are.

  12. I know it's not wood, but I've watched every episode back to back and it's nearly 3am aND IM TRIPPING BALLS CAUSE SOME OF THE LIGHTING MAKES IT LOOK LIKE WOOD.

    Super amazing build, though. This is some of the greatest creating and engineering I've ever seen on YouTube, and you do an amazing job with explaining the process, how each piece works, and why it works.

  13. Hey I just found your channel last night and I love your videos. You do a great job at describing the old methods of clock making and that you do like that is amazing you just got subscriber. Keep up the great work! 🙂

  14. I just discovered your channel and it's totally engrossing. I'm a woodworker but I find metal machining fascinating.

    I have one question though. From working wood I know that square is much easier than round. I see that the modern techniques you use are a time saving issue but I'd like to know how you think the Greeks created such high tolerance cylinders. Did they have some early incarnation of the lathe?

    Can't wait for the next installment!

  15. My favorite long-running series on youtube. Thank you for the amazing craftsmanship that constrasts the usual diy videos that populate here. It is refreshing to see a master of his craft work. I can't wait to see the finished result, yet would be sad to see this series come to a close.

  16. I was floating down the San Juan river between Bluff, UT and Mexican Hat, UT when my phone briefly got service. I checked email and saw the notice from Patreon that there was a new Clickspring video. I was finally able to watch it this morning. As always, the workmanship and videography were outstanding.

  17. love the drill and the drill work, but I have a feeling that if the old ones were building these machines then they would have put that drill on a stand for accuracy, also to save drill bits and to save wollering the hole. That way they could have the apprentice drill the hole and reduce the chance of them messing it up, I bet those old masters were like old school engineering of the past, the youth to sweep the floor and do the drilling.

  18. Awesome craftsmanship with hand tools and scribe lines – ancient and present. I wont trust myself with a hand file beyond 0.15mm. The inventor/ craftsman were totally genius. I mean he had tools far less than the average amateur handyman would have and he created this! Absolute dedication. What is also amazing is also that he used sheet stock for gears that later was the norm in clockwork . Thanks for sharing with us, I totally enjoy.

  19. They recently found another piece of the mechanism. This mocht interest you.
    https://www.archaeology.org/7140-181113-greece-antikythera-bull

  20. Have you run into any issues with work-hardening of the materials you're using? I personally hate working with copper or brass for that reason. I hate having to stop what I'm doing to go anneal what I'm working on before I can continue. I guess I'll just stick to beating steel lol.

  21. gaining an understanding of how this machine works is a great achievement in itself. having the necessary skills and the desire to build one by hand no less puts you in a special place among the craftsmen of this world. we you tube viewers are in your debt for sharing this adventure with us. this has all the makings of a discovery channel documentary. thank you

  22. Thanks for the reminder. I had to go over my astronomical knowledge about the sidereal period and then synodic period. A small detail that appreciated my visit. Thank you

  23. How was this possible more than 2000k years ago? The Pyramids are also a mystery due to the fact that we cannot reproduce the techniques they usedto create near perfect cuts & surfaces and joinery. So how is it possible ?

  24. I have been watching a genius at work. But more to the point, how did they do this centuries ago. Its almost beyond believe.

  25. WHY people dont know anything about MOOn nowadays?
    Possible answer:

    1-You dont need.

    2-You should not know to remain a good and nice slave.work for me , ia will give you everything you need, shitty food, some clothes, and a coin for your remain needs.

  26. Dude, this is so big deal, if I even try to file my nail i get to the bone, that craft you do is so precise and meticulouslly detailed. Awesome!

  27. I would be super self conscious about someone this smart and methodical analyzing every detail of my work thousands of years in the future.

  28. Great work, but they didnt have none of them modern tools, power tools, steel hand tools, etc. Id like to see how the person of persons did it

  29. It just seems strange that not only did no other device of this type, from this era survive the only one we have is a pile of green goop.

  30. Fact or friction,, the relatively light loads of the of the requirements of this mechanism and the non constant spin to read calculations results would support the no lubrications theories at play in the constructors endeavor.

  31. Perhaps I missed something in an earler episode…. but is it possible that the original metal mechanism discovered is a miniaturization of a much larger unit, not meant for travel, that was fabricated possibly in wood and used by those ancient astronomers? Sort of like the original IBM mainframe computer compared to a current laptop.

  32. The history of that machine is amazing but the French guy made one that you could wear is a watch all of the same stuff this guys doing but in the watch

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