What size C channel?

[montrose818]

Looking to build a flatbed for an MDT

What size C channel should I use for the two main frame rails, and what size for the cross members, and spacing?

It will be standard 34" frame width, about 14-15 feet long, and something rigid enough to carry maybe 15k (rear axle is rated at 23k).

This be enough for the main rails?

5 x 6.7 lb (5 X 1.75 X .190)

I have no concept of whats enough. Only whats overkill.

 

[arse_sidewards]

I find it very, very, very hard to believe that you wouldn't be time and money ahead by buying a used one and beefing it up for your needs.

Unless it's a dumping flat bed the main rails underneath don't do shit for preventing bending. That's the truck frame's job. You only really need to deal with bending along the perimeter. We can't tell you if 5x6.7 would be enough for the perimeter rail without more information. It all depends on your crossmember web height and spacing.