Sometimes you think you have come up with a simple design, but when you come to real-ise that design it turns out to be much harder than you imagined to make.
So I went back to the drawing board, and came up with something even simpler. This is what I have come up with, the crudestruder.
There is nothing really innovative about this design, its just a piece of MDF with mounting holes for a NEMA 17 and some 15mm copper pipe clips to hold on the thermal barrier. I used another short piece of 16mm PTFE rod with a 4.0mm hole to act as a filament guide. The pinch-wheel is just one of the standard mendel m4 bearings, and is held using a flange of aluminium that I cut off of my original stock of aluminium angle. This pinch wheel mount is held using the same m3 bolts that hold the NEMA in place. The top hole of the mount was cut into a slot to allow minor adjustment. I use a conrad electronics splined model car insert to provide grip on the drive shaft.