Filament Spool Holder System

This is yet another filament spool holder for Makerbot 2. It holds any number of spools of filament above the Makerbot on rods.
The idea is definitely not new, I borrowed it from several people (see ReMixed from section). The advantages/changes in my design are:
- It holds the spools over the center of the Makerbot instead of off of the back edge. I don't know of anyone that had problems with weight tipping over the printer, but this just seams 'more right'.
- It is easily extensible to taller builds with more spools of filament.
- It handles the 1/2" rods that I had on hand.
- It has an open, airy look to it.
I use 1/2" threaded rods. Other people's designs use different sizes or non-threaded rods, all of which should work with no or little changes.
One of the bigger features is that the rods can be run through the center of the towers (as originally planned), or hung off of the sides of the towers. It was mentioned elsewhere that you have to disassemble a lot when