You can build the BBT 6 GPU open air mining frame below for about $40 out of two 8ft pieces of 1/8" x 3/4" angled aluminum, one 8 ft 1" x 3" piece of pine, one 4ft 1" x 1" piece of pine and #8 1/2" self-tapping screws. You can also build it out of all wood if you want to save some money.
6 GPU Frame (Dimension 21" W x 15 3/4"" D x 10 3/4" H):
Build Cuts:
For the Angled Aluminum:
-First 8ft (96") Angled Aluminum; .75 inch of waste
4x 15 3/4" cuts (63" use) (Case Depth)
3x 10 3/4" cuts (32.25" use) (Case Height)
-Second 8ft (96") Angled Aluminum; 1.25 inch of waste
4x 21" cuts (84" use) (Case Width)
1x 10 3/4" (10 3/4" use) (Case Height)
And for the wood:
-8ft 1x3 Pine (96"); 2 inch of waste:
6 cuts of 15 3/4" (94" use) (Case Bottom)
-4 ft 1x1 Pine (24" left over):
1 cut of 21" (21" use) (Card Bracket Support)
https://www.youtube.com/watch?v=D5xNrlxsCVshttps://www.youtube.com/watch?v=MA_sH4q2toU&feature=youtu.be&t=283