This mechanism allows 2 degrees of freedom by driving either side in the same or opposite direction, In addition to the 2 DOF it operates smoothly and can withstand moderate loads <10 ibs. I manipulated bevel gear files that I got off the internet to create this hands on mechanical design aid. It is really helpful for showing how differentials work.Print out 2x Bevel1 1x Bevel2 1x Diff support I reemed out the holes in Bevel1 and Bevel2 to .5" then used .5" threaded rod to hold the two bevel1 gears together with the diff support in between them. then I used a .5" cap screw to mount the Bevel2 gear onto the Diff support.( this screw should fit snug).