My former roommate and I went half and half on a Prusa i2 a year or two ago. After we decided we weren't living together again, we were faced with the question of who's going to keep the printer. I decided I wanted to create a larger printer, and long story short, this entire printer was created using that printer. Everything was designed by me. See the "Instructions" tab for a full build manual.  
The total build volume is roughly 1 cubic foot (12" x 12" x 12").  
The design challenges as well as a detailed overview of the printer can be found in the instructions.