Antikythera Fragment #2 - Ancient Tool Technology - The Original Dividing Plate?

Antikythera Fragment #2 - Ancient Tool Technology - The Original Dividing Plate?

One thing about this machine that is truly surprising, is just how small the teeth are.

There’s a well established theory as to how the tooth divisions were marked out, but employing that process to mark out multiple wheels has forced me to question whether it can reasonably be applied to the Antikythera Mechanism.

So in this video I propose an alternative process of wheel division, using only the non precision tools of the period.

More detail on the specifics of 223 teeth on B1 below…

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The proposition regarding why B1 has 223 teeth in detail:

The teeth of the main drive wheel B1 are accepted to sit outside the calculating train, and so serve the purpose of simply permitting convenient movement of that wheel, via the input crown wheel A1. In that sense any practical tooth number would have sufficed, and by practical I mean any tooth count that would provide a mechanically sound, robust tooth size.

B1 has an approximate outside diameter of 132mm.

200 teeth gives a tooth module of approximately 0.66 - a very chunky and robust tooth, with apex tip to tip of 2.1mm. A very strong tooth, able to withstand the input torque very well. Although it must be said approaching the point of being too coarse from the perspective of fine mechanism control.

280 teeth gives a module of approximately 0.47 - a reasonably delicate tooth form, 1.49mm between tooth tips, but consistent with almost all other wheels found in the device, and so still a reasonable candidate. Perfect for very fine control of the mechanism, but perhaps approaching the size where deformation of the tooth could occur with exuberant input torque from the user.

So assuming no change to the outside diameter of the wheel, any tooth count (and therefore module) in between this range of 200 to 280 would provide a tooth form that is suitable to perform the role of robustly generating movement of B1.

Latest research has the actual number of teeth for B1 at either 223 or 224. However it is highly likely that the number is in fact 223.

If this is the case, then the choice of 223 is remarkable.

Because if we consider all options within the range of approximately 200 to 280 teeth as valid candidates, then there had to be a very good reason to choose that more difficult division candidate over the more obvious options immediately adjacent. ie Why not select 224? 222? 240? etc

My proposition is that 223 was selected out of simple manufacturing convenience. And that the choice strongly indicates the existence of an ancient division method very different to the current theory. ie One that leverages existing counts to propagate them to multiple wheels.

E3 is known with to have 223 teeth to perform its eclipse prediction role on the Saros dial, so that division number was already required to be present on the division tool.

Knowing that any robust tooth would suffice for B1, The Maker would have been able to directly observe that the count of 223, fits nicely into the range of convenient and robust tooth sizes for the role to be performed by B1. It would have been clear that there was no need to perform yet another large division, when a suitable candidate was already present on the tool.

And so the otherwise surprising tooth count of 223 was selected for B1.


Antikythera Fragment #2 - Ancient Tool Technology - The Original Dividing Plate?