1 extruder 2 hobbed bolts.

http://www.thingiverse.com/thing:170654 just made this derivative and it works amazingly, I had to grind the gears by hand to get them to mesh and they are still a little large, If someone could help me with making some better gears I would greatly appreciate it, anyways i can get about 16mm/s of input from 1.75mm abs as of right now, I havent tried more because the drive gear was slipping on the stepper. this will fit onto any hinged idler exrtuder that is compatible with the gregs wades reloaded extruder. I just ran a 12 hour print at 90mm/s using a 0.6mm nozzle and 0.45mm layer height with zero stripping. I had to stop the print because it delaminated right in the middle unfortunately, about 7.50 in plastic is now scrap, but it gave me an excuse to move the printer into the garage and start using the heated build chamber.

anyways tell me what you think and give me some help with the gears if you can. oh and also my hobbed bolts were slightly different but it didnt seem to matter at all.

Nice work! I am guessing the idea here is to be able to get a better grip on the filament to push it faster? I have two questions? Would adding this extra mass to a direct print head cause problems when you run the printer at accelerated speeds and secondly, if the first hobbled bolt impressed the filament, is this going to cause problems with the second hobbled bolt gripping the filament? In my mind this seems like the second hobbled bolt might just grind grind up the already roughened up filament? Perhaps I am over thinking it?

it grabs it on the opposite side of the filament, so its not a problem

Aha, I see that now, thanks!