Hobson's joint

A Hobson's joint or Hobson's coupling is a type of right-angle constant-velocity joint; rods bent 90° are able to transmit torque around a corner because they are all free to turn in their mounting holes in both legs of the coupling.^[1][2]

Hobson's joints are used to make elbow engines, a novelty device,^[1] but also for practical purposes in tools^[3] and shaft-driven bicycle gearing.^{[citation needed]}