I was trying to source a rotating platform/ slew bearing to use in conjunction with a camera and there wasn't anything readily available on the market that seemed right for the job.  Slew bearings are heavy and expensive, and there's a little bit of wiggling that happens when the load is unevenly distributed.  So I came up with this design specifically to deal with the kind of forces at play when you're dealing with a mounted camera and trying to get a smooth shot with no backlash (which would be visible in the footage).  With this design you can adjust the pre-load tension between the two mounting plates (the two main pieces of plastic that move independent of each other) by tightening the nut/bolt that runs through the whole assembly.  Also in pre-loading the two halves you end up centering them on the one large bearing, thus reducing any wobbling between the two halves.