Geneva Crank Fidget

The Geneva drive, also known as a Geneva mechanism, is a gear system that converts continuous rotational motion into intermittent rotational motion. It's widely used in various mechanical devices for its precision and reliability. I added a secondary locking piece just to make it more interesting: It spins freely counterclockwise, but often will lock up going clockwise.

Some key concepts from Chat GPT:

Rotation Angle per Step: Each step of the Geneva wheel corresponds to a fixed rotation angle, which is determined by the number of slots:

• 360 degrees/N = Rotation Angle

For example, if the Geneva wheel has 4 slots, each step will be:

• 360/4 = 90 degrees

Center Distance: The distance between the centers of the driving wheel and the Geneva wheel must be carefully calculated to ensure proper engagement of the pin with the slots:

• D = √(D^2 - R^2)

For a Geneva wheel diameter of 10 cm and drive wheel radius of 2 cm:

• D = √(10^2 - 2^2) = 9.8cm

Arc of Movement: The driving wheel's pin moves through an arc when engaging a slot. The length of this arc is related to the rotation angle of the Geneva wheel.

Dwell Period: The Geneva wheel remains stationary while the driving wheel continues to rotate. The length of the dwell period depends on the number of slots and the rotation speed of the driving wheel.