This is a work in progress but thought I would share. This was designed to allow two wades extruders to be attached to a Printrbot. (Or a Dual Extruder Printrbot by Japica, however I may be the only person who owns one of these....) The weight of the extruders is a problem with the 2 x rods that are stacked vertically. (this was the way the extruder mount was designed when I got it from Japica).
I designed the " 3rd rod x axis brackets" to be a glue on part for the current Printrbot parts, if this all works I then plan to merge the parts together as one part file and reprint.
I also have been having trouble with the linear bearings on my dual carriages so I m trying these "Pillow Bushings" from Lulzbot. They seem to be very smooth, just have to get your spacing just right.
PLEASE NOTE: the current files are 1st gen and I have had to do some hand work on them with a dremel and mill to get them just right for my setup. ALSO I have access to a Dimension Printer which these parts were printed off of, support material was used and most likely needs to be used. I am just trying to get my printer to work at this point in time as it was built for me and hasnt worked properly yet. If there is interest, once I get my printer up and working and the bugs worked out of the parts, I will go back and look at making the parts more single extruder friendly.
I have found that gluing the top 2 pillow bushings into the cutouts of the mounts makes the part even more sturdy.
I have designed a linear bearing version: http://www.thingiverse.com/thing:81404