**I just uploaded a newer version of this design please check it out first: http://www.thingiverse.com/thing:456025
This is a mash-up of the Greg's Wade extruder and Terawatt Industry's belt drive extruder. It brings the zero backlash advantages of the Terawatt 00str00der design together with a heavy duty, rock solid design.
Video can be found here: http://youtu.be/cY4r6K0P9Qk
2013.12.05 Added 1.75mm filament option
2014.05.30 Corrected belt size
65T plastic (carbide) GT2 pulley w/8mm bore, flanges, set-screw
17T aluminum GT2 pulley w/5mm bore, flanges, set-screw
GT2 belt, 2mm pitch, 88T, 196mm length, 6mm-with, fiberglass-reinforced, closed-loop
Pulleys and belt can be sourced from stock drive products, Terawatt industries, ebay, etc.
608 bearings, 3 minimum (more could be used as spacers on the hobbed bolt)
2x M4 x 55 SHCS
1x M8 axle or stud for idler pulley
4x M3 SHCS for stepper mount
4x M3 washers for stepper mount
misc other M3 / M4 hardware
Assemble as normal for Greg's style extruder. Use the slots in the stepper mount to tension the belt. Be sure to recalibrate your E steps after installation. You may also have to reverse the direction of your extruder stepper in your firmware. (I did)
Note the photos shown illustrate assembly using Terawatt Industries' elastomer bumpers for the idler tension springs. I'd highly recommend using steel springs instead, they seem to work much better.
Enjoy quieter, backlash-free printing!