Still in the draft stage but the best extruder I have used yet. Two opposing motors. this give a rock solid grip on the filament. Next revision will be making a tighter fit on the empty space around the pulley on each side. You may need to addjust the screw holes for the motor, if they get too tight the filament wraps like crazy (don't ask how I know)Future will see this design refined and printed on the CupCake, two pieces, the one side will hold a motor including entry /exit for filament and hold the nozzle. The other side will dovetail and slide so the motor pulley can be adjusted for tightness to the other pulley, Im thinking it should have a bolt in the direction of the motion with a wingnut for adjustments. See sketch. ANYONE please feel free to design that mount, I am not terrible good at setting up parts with accurate screw holes etc. :-)"Type R" as in BMW motorbikes, two opposed cylinders slightly offset.This is a DRAFT design, but it works VERY well so far. (at least for me)I used 3mm acrylic material, it is actually a little too thin, so I mounted the two motors with a set of washers to pull them out a little and also wrapped a piece of tape around the center piece to make sure the filament would move smoothly.To prevent the motors from pushing apart I glued the 4 layers on each side to a firm brick, this helped create a very firm mount.The Dino is very rudimentary, only one piece of 3mm on each arm, I thought it would wobble, but it seems plenty firm.