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The next lifter needs a crank that oscillates for about 200 degrees of a circle. The only way to achieve that is to use a motor crank to drive a crank on the big gear that then drives the small gear and its crank. 100 degrees of movement of the crank on the big gear is then 200 degrees of movement of the crank on the small gear.

See the video if it doesn’t make sense:

https://www.youtube.com/watch?v=RpJbGZhRH5E