For my past several projects where I needed some sort of light-duty torque transfer, I would use a 3d printed clover coupling like the one shown below from a pump project I did a while ago.

While this coupler works ok, it doesn’t provide for any misalignment between the input and output axes.

I decided I wanted to see if I could make a u-joint inspired coupler in approximately the same form factor as the previous coupler. Primarily, I want it to fit through the same 30mm bearings, since I have quite a few of them on the shelf.

My idea for this coupler, as I mentioned previously, is based on a universal joint. What I wanted to try, was a u-joint that uses v-groove, fork tine kind of things on the shafts, like shown below.

And sandwiched between these two, is a hub with four cylindrical shafts nested in the Vs. The below model was a sanity check design I made as a first test of the concept.

Design Goals:

• I’d like the coupler to fit inside of a 30mm ID bearing. That would make it a ‘drop in’ replacement for the spider couplers I’ve been using.

• +/- 1 mm radial misalignment

• +/- 5 deg angular misalignment

• ≥ 1 N*m sustained torque capacity

I used the proof of concept design discussed above as a starting point, but I reduced the pin sizes to 3mm OD from the 5mm used in the initial test. The below image from the model shows the first attempt at a coupling that meets the above requirement to fit within the 30mm ID of the 6806 roller bearings I often use.