This is a Java animation, by Bill Casselman, of the
differential assembly in the Antikythera Mechanism.
Top slider controls the green (Moon) gear;
bottom slider controls the purple (Sun) gear.
In the Mechanism itself, these inputs were not
independent, since they were fixed by the Sun-Moon
assembly in the ratio 254 to 19.
|The complete ranges of speeds show that, taken out of the Mechanism, this is a true differential. The next one known was invented in the 19th century. To simulate its operation inside the Mechanism, choose moon-gear speed +2 and sun-gear speed -1/8. This will give a ratio of 16, while the actual ratio of speeds was 254/19 = 13.368... .|
Return to 4. The differential in the Antikythera Mechanism.