1st off this is my first Instructable so I hope I took enough pics and I don't do too terrible with the instructions.
2nd this is not my design, I got the plans from http://s683.photobucket.com/user/simul8r/library/?sort=6&page=1 , so credit goes to simul8r
Step 1: How to Make a Straight Freehand Cut on a Pvc Pipe
Rip a flap off of a cardboard box, make sure its long enough to wrap around the pipe 1&1/2 times. make a small mark where your cut is going, then wrap the cardboard around the pipe making sure the overlapping part of cardboard lines up with the rest of the cardboard on your measurement mark, you now have a straight line and can trace that line onto the pipe with a marker. then cut with a fine toothed hacksaw blade, when the blade breaks through to the inside of pipe start turning the pipe away from you following the line.
Step 2: Parts List and Pvc Cut Sizes
I believe I spent around $120 for PVC,MDF and plywood. I already had everything else needed (primer,glue, ect)
My wheel and pedals were around $300 new but that was years ago, depending on how realistic you want your experience to be there are lower grade wheels on Ebay used for about $50.
2" PVC parts list
T's x14 (15 if you want to add a cup holder)
45 Degree x3
90 Degree x6 (8 with the cup holder)
End Caps x2
2" to 3" adapter x1 (cup holder)
10' PVC pipe x3
Step 3: Mock Up and PVC Assembly
Mock up (pre-assembly without glue) here you need to make sure everything fits and cut lengths are correct, mark all your joints to make sure they line up while gluing. While internal wiring isn't necessary I recommend doing it, I drilled x3 3/8" holes then ovaled them out into one oval hole, though I'd recommend buying x3 2"x2"x1" T's and using those for the wire access points.
Step 4: Cut and Install Plywood And/or Mdf
I'm not going to go into much detail here since your seat and steering wheel/ pedals combo will decide what you do from here. I included the templates for my Logitech G27 setup.