# 0 to 360 degress constrained rotation mechanism

I'm looking for examples of mechanisms that can constrain a hub rotating around a shaft from 0 to 360 degrees. Rotation between 0 and 360 should be free. Rotation < 0 and > 360 should be stopped.

A few things I think could work but I am not not sure what this is called and searching on Google has not helped.

• a simple pin would allow for 0..(360 - pin_width)
• a spiral would allow hard stops 0..360 but the pin would need to float radially.
• a gear set of 2:1 would allow for pins but would add some complexity.

Thanks for any ideas folks might have and/or any names I might be able to use in a Google search.

• You have a hub with a pin in it that is allowed to spin free on a shaft. You can add a stop collar with a 'dog' that stops rotation in either direction by interacting with the hub's pin. If this stop collar is allowed to float a distance equal to the diameter of the pin plus the width of the stop 'dog' (possibly through its own pin and slot in the shaft) then you achieve a 0° -> 360° -> 0° restricted rotation.
– user21645
Sep 1, 2019 at 22:05