Anyone weigh the before and after of a boxed pickup frame? (6x2.25" C-channel type 10 gauge) I've been considering just using rectangle tube, and am wondering what smaller size I can get away with, without sacrificing strength? Can be looked at in two ways, I guess: smaller dimensionally with the same wall thickness, or the same 6x2.25" with a smaller wall thickness.
That is a mechanics of materials question. I lost my book. The answer depends on which way the frame is bent - vertically or horizontally. The true answer can only matter if you use a completely flat frame with no kickups, bends, or z's.
I sent an email to our engineers at work, but today's Sunday. And engineers being engineers, I probably won't get an answer for a good month or more, lol. Anyway, I was only measuring the section between front and rear suspensions.
Depends on how the frame is built and what it is going under. 2x4 x.125 may work real well if it is properly cross braced. But it may not hold up well at all under a ton dually, if you catch my drift.
Section height is the driving factor for strength, thickness has negligible effect on strength. Take a look at this: http://www.structural-drafting-net-expert.com/steel-sections-standard-channels.html Click on the "properties" tab. Look at "I" in the column "Axis X-X". "I" is basically the strength of the channel. See how it dramatically increases as the height increases. Using a tube doesn't dramatically increase strength over a c-channel, but it does help with torsional rigidity.
Thanks, I agree the height is the biggest factor. Maybe I'm over-thinking the weight issue. I'm looking to replace the frame rails on my KB2, the crossmembers will remain, except for the bends and locations to accomodate the different driveline. Since the frame rail is the same on my F1, I'm hoping to get a general idea in case if I do the same to it, as well.
Got my answer: Equivelant would be 5.5 x 2.25, same wall thickness., or 6 x 2.25 x .093 wall (13 GA.)
Only sizes available are 6x2, or 6x3. Looks like it'll be 6x3 with 1/8" or 3/16" wall. I prefer the strength of the 3/16", but at 3" wide, it's getting pretty heavy. Do you think the 1/8" wall will be good enough?
The suspension brackets are a U shape that fit over the rail, with a 3" ID. So I figured using the 3" rail would just be easier. I plan on holesawing a couple holes for sockets on the back side of the rails where the running board brackets and such bolt on. I also intend to use L brackets where the cab mounts are, and stuff like that. Crossmembers will be welded on, and of smaller dimensions. The rails at the suspension points are of different sizes too, so it's mainly the center between axles that is 6". 3" gives plenty of surface on top for any holes that need to be drilled. 2" may be fine, but I keep coming back to the U brackets being 3" ID. Decisions, decisions, lol. I forgot to mention this is for my KB2, which is a 3/4 ton.
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