OoiTY's Beefy Dual Fan Bushing X-Carriage No X-axis loss

Updated by this; http://www.thingiverse.com/thing:92028

As popular as the designs for X-carriages with 40mm fans between the rods are, they cause a loss of x-axis travel of at least 10mm per fan. With 20mm fans like I use, this means there'll be a total of a 40mm reduction. The goal for this design is to maximize the amount of X-axis travel while still having 2 fans.

Also, uses Zipties to secure the bushings to the carriage, since I noticed that regular designs for bushing carriages crack