I've constructed and tested an eddy current brake.  The test was a failure.  I used about 8m (30 turns) of 0.33 mm (#28 AWG) insulated copper wire wound into an 85 mm coil.  It has about a 1.5 Ohm resistance and rated for 1.4 A max current. Therefore I did not use more than 3V to test it.  I will try boosting the voltage a bit more since I don't care about destroying it.  However, at 3V and about 450 RPM I did not see any breaking (movement of the tibia).  This is not a standard eddy break coil configuration.  I wanted to try a core-less design.

I am also working on a new Femur designed to print in one piece.  Both eddyBreak.FCStd and femurBlock.FCStd are available in BreakerOne_experimental_2020-06-04.zip