NEMA17 Universal Belted 2:1 Reduction Drive

This is a universal belted 2:1 NEMA17 reduction drive. It's based mostly on parts used to build a Voron Mobius extruder (http://mzbot.us/voron_mobius). Thanks to the use of pulleys and a belt as opposed to gears, this setup is very quiet.

BOM:
1x GT2 40T pulley
1x GT2 20T pulley
1x GT2 110mm belt loop
1x 5x50mm steel rod (shaft)
2x 625 bearings
2x M5 washers to separate the bearings from the 40T pulley
2x M3x10 socket hex screws
2x M3x25 socket hex screws
4x M3x25 OR LONGER socket he