Thanks to everyone for their comments.
Somehow the description didn't get posted when i uploaded the picture. What you see weighs 19 lbs. I haven't decided what gearboxes to use, but i have AM toughboxes or DeWalts in mind. The frame is 1x1x3/16 square tube, and will be welded.
Yes, Only the 2 center wheels are powered.
I was not planning on using 80-20 because it would make it heavier than i want this design to be.
The angle aluminum that supports the axles is 3/16 inch thick.
InfernoX14 explained dead axles.
Do you mean done in CAD, or built?
I will probably continue CAD of this design and similar ones until 2009. I don't know when i'll be 'done'.
To answer the comments about 6wd vs 2wd:
This drive base design was meant to be simple and light. Part of meeting this goal meant not powering the corner wheels.
For 3 out of the past 4 years, 1519 has used a 2wd drive, powering the center wheels only.

We have had good success with this design. The only drawback of this drive system is, like IKE points out, it cant climb ramps.
I like 6wd, but this design is meant to be the simple, light, stick-with-what-we-know design.
They are custom 6 inch aluminum wheels with roughtop or similar tread material.
They are 'poor mans omnis'. I'd like to get away from using them too, as are heavy.
Poor mans omnis are a lot cheaper than regular omni wheels, and they slide laterally very well, but not better than omnis.
Ryan, thanks for your advice about torquing the frame. Where would you recommend putting the round tube?
Comments are welcome
DB