YouTuber Robert Murray Smith has published a historically inspired gear system as a 3D model. It is based on the Antikythera mechanism, an ancient gear mechanism from 80 BC that was used to calculate astronomical movements. Smith is making his model available free of charge on the Thingiverse platform.
The special feature of this 3D-printed gear is the use of an epicyclic system, also known as planetary gearing. This involves several gears moving around a central sun wheel, similar to the planetary orbits around the sun. This concept has been further developed over the centuries and can now be found in numerous technical applications – from power tools to automatic transmissions.
A key feature of the system is its compact design with a high transmission ratio. Classic planetary gearboxes enable transmission ratios of 4:1 to 10:1, with several stages often being combined for higher ratios. Smith shows an alternative technology in his video. The stacked arrangement of planetary gears with different diameters. This principle was developed by Urs Wolfram in 1912 and enables an even greater reduction in speed.
In practice, this gear system poses a number of challenges. Precise indexing of the upper and lower gears is necessary to avoid tilting. There is also a physical limit to the size of the gears. Smaller teeth improve the transmission ratio, but above a certain size, the risk of manufacturing inaccuracies increases.
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