This evenings fun project, modifying @Ax_Smith-Laffin 's Drakon Extruder (a 3D Printable variant of the E3D Titan geared extruder using off the shelf components) to be capable of dual direct driving an E3D Chimera. This is actually something that’s been on my mind for 2 years - making a dual direct drive for the chimera. But putting 2 full size Nema 17’s side by side will make for a heavy head. The idea here is to be able to put 2 of these guys (a regular and a mirrored version) back to back, and because of the gearing be able to use pancake steppers, making for not the smallest by any means, but still a lighter head than what we had to work with before.
Now, the 2 filament entrances of the Chimera are 18mm center to center so I had to slim down everything above the groove mount hole. And indeed, I’ve gotten the top surface to be exactly 9mm from the center of the groove mount. Plus the top surface should be completely flush - all screw heads are inside it.
In short, this involved removing Ax’s printed bushings and going to a smaller bearing size - from the 625’s in the original design to 695’s when I needed that final 1mm of reduction that bearing did the trick. Finally, I am using an openbuilds M5x25 screw which is the lowest profile head I have seen anywhere - this was also necessary for keeping the top surface flush with nothing sticking out.
Of course this is also experimental until I get them put together (new parts already printing) and the new bearings arrive.
All in all I think this might end up being an even slimmer and possibly lighter version of the original, maybe someone will use it in more “normal circumstances” than what I have in mind. 
