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@alan8325 Not a very useful version of that idea, as the teeth overlap so you can't put a shell in between.
Versions without overlap actually get used in things like nuclear power plants to pass mechanical motion via isolation barriers.
In a prior job I worked on the design of the converse: a rotary transformer to transmit electrical power between two 100% mechanically isolated components.
@alan8325 good point!
@pete Maybe it could have use in prolonging the life of 3D printed mechanical parts in systems you don't want to have to replace parts in all the time. This 3D printed solar-powered rover, for example, is a pretty cool project. https://www.youtube.com/watch?v=QVep9iSXVeo&t=874s