The Antikythera Mechanism Episode 9 - Making The Epicyclic Pin and Slot Gearing

> One wrong move and you're starting over on the entire part My guess is that it's possible to fix typos, but it would be a lot of additional work. For example to fix pieces, he makes a hole and put a small bronce in the hole, then he punch it, and then polish the surface until it's invisible. For example see this port of the previous episode ▶ this video Anyway, I'd be terrified of making a mistake if I had to do this.

Perhaps the most beautiful part of the mechanism is the modelling of the motion of the Moon, which Chris describes in minute detail [1]. [1] ▶ this video

Clickspring's work on the Antikithra mechanism (and the Pateron exclusive Byzantine Sundial) is particularly interesting, because not all of the movements created by gears are circular or even. The input can be purely rotational, but the output is not. For example on the Antikithra mechanism, it has to account for the procession of the moon's orbit which causes an uneven time to complete one orbit. To properly simulate this, a pin-and-slot system is combined with an offset pivot to turn the rotation of gears into a movement that lags behind and then speeds ahead, mirroring the actual orbital period. I worded that poorly; the video does a better job of explaining it (within the first minute), and the rest of the video shows the gear train coming together ▶ this video