Progress on trailer frame repair

jon f mn

Well-known Member
Finally got some time to work on the trailer frame that is broke. The owners took my advice and decided to replace the beams rather than fix them. So I decided the easiest way was to pull the wheels out from under the trailer.

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Once it was out it was easy to see the extent of the damage was even worse than I thought. The previous repairs were some of the worst I've seen. On one side the frame was broke both front to back and top to bottom. And the previous repair guy never even bothered to align the frame or weld the flange.

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I don't know how they thought that would hold, and it is a dot violation when it left the shop. They were lucky to not get caught. Whoever was doing their inspections also wasn't doing their job.

Anyway, I started by cutting the old beam out and cleaning up the parts for welding.

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Then I cut the new beam to lenth and drilled the holes for the top stop and torched the hole for the load carrying roller.

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Just to show how poor the construction of this trailer was even from the factory. I couldn't figure out why the sides didn't match in the front and I couldn't pull them even.

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Then I put a square on the front cross member.

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The front crossmember was installed crooked from the factory. Lol. I didn't bother to fix that because it doesnt matter other than appearance and the frame is square and the axle is square.

So next was welding the beam in. Been several years since I did a vertical up weld and you can see they are not great, but I think they will hold.

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Sorry this pic is out of order.

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I added these 2 gussets to help keep it from cracking again. If the factory had put something like that in there this never would have been a problem.

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That's as far as I got because I ran out of gas for the welder. .I should get done with the welding tomorrow.
 
Nice work, doubt you will get driving too much if you do work like that and save company big bucks.

Have you thought about sending that out and getting galvanize dipped when done?
 
I really doubt you will last there, think your quality standards are too high for them.

That industry is cheap, cheap, cheap.
 
bummer.... i have a couple of 500 amp mig welders outof a cat plant that would look good in yer shop!!!
 
Depends what frame you are talking about. You are thinking of a truck frame. The rails are heat treated high tensile steel, and designed to flex. Hence the bolted only connections.

The trailer frame Jon is working on was built out of plain old mild steel channel iron. Probably could have been designed better, or it wouldn't be broke in the first place.
 
Moresmoke has it mostly right. You try never to weld across the flange of a beam if you can avoid it. Sometimes you have to tho. You can weld to truck frames too, or weld them together for shortening or stretching frames. But on truck frames it's much more technical both for welding process and technique. For this since it's all mild steel I'm using mig for everything. As far as welding on beams like this there is a lot of technique involved too. For instance those gussets should have been put in at the factory to prevent the beam from flexing which is what caused the problem here.
 
I once worked for a trailer Manufacturer as a welder. We were using .052 wire and 375 to 400 amps. The trailers were
Michigan trains for hauling coil steel 30+ inch tall stringers with 1" webs and 1.25 X 8 inch wide flanges. The juniors
were 12X3 inch Ibeams at 12" OC. Two 35,000 pound coils were usual loads. 8 axles 5 air and 3 single leaf. Obrecht Trailer inc. You make nice welds. Jim
This one only has 7
 
well heck fire.....build a shop with three phase, kruser and i will load up the welders, grab some bail money and head up to minniesoater!,,, road trip!!!!!!!!!!,
 
The reason you don't want to weld (or flame cut holes) to the flange of a beam is the toe of the weld (or the jagged edges of a flame cut hole) have small inclusion that create propagation sites for metal fatigue (crack formation). The higher the strength of the steel the less ductile it is and the more prone to cracking. If you are welding/repairing a flange, then you want to make sure you do a CJP (full pen) weld so you don't create a spot for a crack to form. Usually in offshore structures, critical welds are back ground to remove these includes and the capped with welds to create a "nickle" profile. This creates a smooth transition between intersecting surfaces to also minimize fatigue. More info can be found in AWS D1.1. Holes in structural steel are required to be drilled or punched to minimize crack formation (drilling is better).
 
Oil and gas welding and most government regulated welding is significantly different from truck and trailer work. Any time you weld steel the metal is weakened due to the damage from the heat. There is no welding process that can avoid that. For gas and oil and buildings and bridges and such the material is over sized to provide a significant margin for error. That margin creates the window for simple welded only joints. For truck and trailers there is little or no margin which means the technique for joints is significantly different.
 
Fracture mechanics, fatigue life, and stress in steel behave the same irregardless of the application. The main differences is total service life.

The problem with the heat affected zone is that it makes the material more brittle (relatively speaking). Following the preheat and post heat treatments like you would in a structure will help alleviate the stresses and hardening due to the welding. Also grinding the welds smooth helps reduce the stress concentrations at the weld and remove slag inclusion at the toe of the weld (crack propagation site) both of which improve fatigue life in all applications.

The best way for minimizing fatigue is to reduce the stress ranges in the member, which you have done with your gusset plates. Reducing the stress range load by half will increase the fatigue life between 8 and 32 times.
 

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