Frame rails

[krautmeister]

So I don't know the best place for this... my truck was a pretty impulsive buy... I regret lacking research prior to purchase... thankfully it was cheap!

So I noticed when my truck was parked on a section of my driveway that's a bit twisted and saw the bed was slightly torqued and was not "square". Now on level pavement, it looks just fine.

I recently got it all up on jack stands and found this. Can anyone tell me if the rails are bent? I feel like it should be a "C" rail and it looks like a "J" rail in a cross section.

This picture was driver side behind the cab.

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[oldchevy4x4]

Yeah that should be flat on the bottom (as in normal C channel). If you sight from front to back down the body is the ridge on the side of the truck straight? Or does it look like the fenders point up a little? Or maybe down?


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[Honky Kong jr]

So I don't know the best place for this... my truck was a pretty impulsive buy... I regret lacking research prior to purchase... thankfully it was cheap!

So I noticed when my truck was parked on a section of my driveway that's a bit twisted and saw the bed was slightly torqued and was not "square". Now on level pavement, it looks just fine.

I recently got it all up on jack stands and found this. Can anyone tell me if the rails are bent? I feel like it should be a "C" rail and it looks like a "J" rail in a cross section.

This picture was driver side behind the cab.

You must be registered for see images attach

That hole that is burnt threw in your pic would concern me as well.

 

[OkieFishMan]

Yeah, that large hole ain't factory. But the good thing about metal is it can be persuaded to do what's needed.

 

[Honky Kong jr]

Yeah, that large hole ain't factory. But the good thing about metal is it can be persuaded to do what's needed.

You can see the heat marking around the hole where the temper of the steel has been changed.

 

[chengny]

Look at the bottom flange. In one area it is kinked with an upward bend. Directly behind that upward deflection, it appears that the lower flange is not square to the web (i.e. the vertical side) and is distorted downward:

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The top flange isn't visible in this image - but I'll bet that it has distortion similar to the bottom flange.

When a piece of channel stock is bent by a force applied perpendicular to the outer face of the web - this is the result.

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As the web flexes/bends inward, the flanges are put under compression. This is because the length of the space they occupy is being reduced. With nowhere to move in the longitudinal axis, they begin to get squeezed. At some point - if the web is bent enough - they buckle and develop a ripple in the area of the bend.

Sometimes it's easier to visualize what happens if the web is bent in the opposite direction (if the bending force is applied to the inner face of the web). In this case, as the web bends, length of the area the flanges occupy is increased. Now the flanges are put under tension and begin to stretch. If the web is bent far enough outward they will eventually tear.

This all conjecture on my part, but I would say the frame rail was bent inward at some point - and that ragged torch cut hole was made to accommodate for frame pulling equipment. Also, that mark (that looks like a 3) directly above the ripple isn't something you'd normally see on a frame rail. It was probably meant to mark the area of deformation.

 

[krautmeister]

So looks like it's deformed... accident what not.

So what do I do from here? Can I box it in, weld supports or is this frame scrapped? I don't want to dump money into it if it is flawed from the start.


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[chengny]

Nah, don't do anything. It's a little distorted, but apparently at some point, someone at least tried to pull it straight. That's how a bent frame is repaired. Once those ripples are created, they don't generally come out. But the structural strength of the rail has very likely not been diminished to any great extent.

If you notice, there is no evidence that any heat was used to straighten the rail (other than to burn the hole) - it appears to have been pulled cold. If heat is needed to straighten a frame rail it loses some degree of its temper - and that can cause trouble.

If the truck rolls straight and it looks okay - I'd just let it be. The bed can be shimmed if the slight misalignment really bothers you - or you can always just try to park on level pavement. Sorry - I couldn't help it.

 

[krautmeister]

Good stuff! Thanks! Yeah for what this truck is, I'll patch it up and enjoy it! It's not any show winner nor will I put a ton of power through it


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[oldchevy4x4]

Does the truck have a salvage title? If the frame was straightened it should be fine to reinforce it. If they did a crappy job straightening it then it might be worth finding another one


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[shiftpro]

That's not a bent frame, it is more of a dent from smoking something like a rock. If the frame was bent enough to cause this ripple, it would be very obvious.
This is how you fix it... get a really big crescent wrench on it, you might need a pipe snipe on it, and bend it down where it's supposed to be. If you have a torch go ahead and throw some heat on it. Don't worry about heat stress or temper, it's all good.
I've repaired and modded many frames, welded on them more than enough. Fixed many semi tractor frames bent and or broken. Fish plated lots and welded the ever living **** out of them and everything was well tested.
Local laws may be another story... here in Beautiful western Canada any welding on a frame other than welding a hitch to a truck frame is a call for a tow truck. If we shorten a frame then the welds get ground smooth and the entire frame gets prepped with the same care and painted and undercoated to hide that it was welded. The inside of the frame is another story as far as hiding the work, but if inspectors have no real reason to crawl underneath it will never be detected.
I'll be shortening the frame on my crew cab there will be no welding. I'll move the spring perches forward and cut the frame rail right behind the rear spring perch. This is acceptable in my woods...