Dual cardan coupling (RC car transmission)

This is a part of a bigger project and mounts on my other model (the gearbox) and should drive a differential gearbox (yet to come).

A dual coupling is needed when you want to link 2 rotating shafts, even if they are supposed to be aligned by design. In fact, they are not! This device will be forgiving for slight misalignments.

The different parts are assembled with M3 nuts and M3 hex screws of different lengths. Except when you are assembling with the shafts, the right screw size should be 8mm.  Do not overtighten the screws on the links, it needs to rotate freely. 

For my boat design I used 2 RABOESCH cardan couplings per propeller shaft. This time I’m making my own… Even though for the boat I did something kludge because I realized that a single cardan coupling would not do the job. So, I printed 2 PLA parts that would make my single Raboesch cardan into a dual one (fixed length).  Here there is 2 shafts + a sleeve.  The idea was to add tolerance on the length of the coupler. 

As my reductor gearbox drives 2 shafts (front and rear) my design will need 2 of these dual couplings.

Printing is quite straightforward: 0.20 Quality preferably without supports.

You need to open the screw holes on the gimbal parts with a small screwdriver (in-design supports).