Mounting a flatbed. Is it ok to weld steel bar to it?

[freefly23]

Hi guys,

Hope you are all doing well. I am working on making a camper for a truck. I was wondering what the best way was to overcome the "hump" in the pickup frame. It looks a lot like this:

The measurements and offsets for the hump are really not common sizes. The rails before and after the hump are something like 2 3/16 and the other one is 1 5/16. So to mount the flatbed. Would it be ok to just cut some solid 2x2 steel bar and weld it to the bottom of the flatbed? This way I can customize the size of the steel bar and it will keep the flatbed flat.

Any other suggestions for mounting the flatbed flatly over hump would be awesome!

Thanks!!

[MMW]

A lot of commercial beds use wood fillers, one before & one after the hump. Easy to cut to the right size & has a little give to it. Then mount bed to frame with u-bolts. Other ideas I have seen are to use short pcs. of tubing standing up cut to the proper size for each spot they are used. A bolting tab is usually welded to the bottom of it so it can be bolted to the chassis. This sounds like what you are asking about.

You can use solid 2" square bar but it is over kill. Most homebuilt beds usually have a weight problem. Pay careful attention to the overall weight as it adds up quick. This is the reason many commercial beds are "cheaply" built. One reason they are made like they are is to keep the weight down.

[WillieB]

I vote mounting on existing bed mounts. Probably cross members utilizing the shock absorber rubber mounts the existing bed sits on, with perpendicular long way stringers.

[freefly23]

So the existing bed did not have shock absorber rubber mounts. The truck is a 2005 F-350 SRW.

So the hump is in the middle of the truck's C Channel rails. The bed basically seems to be different size steel tube running sidways. The first 2 sideway members of the bed are big maybe 3 x 2. The next 2 that are over teh hump are smaller. Then the last 2 are bigger. That is I'm talking about the stock bed I removed. Also to overcome the fuel tank, the tube that runs over the fuel tank literally has an arch on the bottom. Really an odd / custom shape.

This is kinda what the back looks like (the picture is not my truck btw):

[WillieB]

I don't see body mounts as on the other sketch. I favor 1/4" thick by 6" wide flat stock running vertical, sistered along the truck frame. Use existing bolt holes & don't drill the top or bottom of the channel frame. I'd use four on each side. Using C channel lengthwise, bolt them to the uprights. Now you can build on using weld. Be sure to butter with grease between anywhere layers could trap water causing rust.

[Steve83]

Ford provides a LOT of the data you need, including "best practices" recommendations. It's all available free...
https://www.fleet.ford.com/truckbbas...eries_v1-2.pdf
Page 29 might be what you're looking for, but p.39 shows why you're having to deal with it. If you need more data, start here:

https://www.fleet.ford.com/truckbbas/topics/bodybuild.html

Starting with the bottom of your flatbed, I'd weld on a piece of angle iron just OUTboard of each of the truck's frame rails. That will prevent the flatbed from shifting sideways, and it will give you a STRONG vertical lip to support & distribute the bed's weight along the frame rail. Lift the bed so it's just OFF the highest point of the frame, level it so it's square to the back of the cab, and then weld in bolt boxes to the bed & the angle so they rest on the frame. Tack weld the bolts to the boxes after their nuts are torqued so the bolt can't spin (no backup wrench) or fall out if you ever remove the bed. Use the original factory holes, including any factory holes that were unused before, if they're convenient for you.

[freefly23]

Ford provides a LOT of the data you need, including "best practices" recommendations. It's all available free...
https://www.fleet.ford.com/truckbbas...eries_v1-2.pdf
Page 29 might be what you're looking for, but p.39 shows why you're having to deal with it. If you need more data, start here:

https://www.fleet.ford.com/truckbbas/topics/bodybuild.html

Starting with the bottom of your flatbed, I'd weld on a piece of angle iron just OUTboard of each of the truck's frame rails. That will prevent the flatbed from shifting sideways, and it will give you a STRONG vertical lip to support & distribute the bed's weight along the frame rail. Lift the bed so it's just OFF the highest point of the frame, level it so it's square to the back of the cab, and then weld in bolt boxes to the bed & the angle so they rest on the frame. Tack weld the bolts to the boxes after their nuts are torqued so the bolt can't spin (no backup wrench) or fall out if you ever remove the bed. Use the original factory holes, including any factory holes that were unused before, if they're convenient for you.

Hi Steve83, thank you for replying.

I check the links you posted. Did you mean page 39 would show me why I'm having to deal with the pickup hump? I'm still unsure why they didn't just make all pickups like chassis cabs. Is there any particular advantage using a wider frame and adding humps in the back?