Overhead welding on a semi trailer

I have a "beavertail double drop deck semi trailer":

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that needs some work done on its very tail end:

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Some of it would involve "Overhead" welding, operating from below the weld.

What is the easiest way to do it correctly. These would be welds that need to hold up when a forklift or a metal tracked vehicle drives over that tail.

We have solid mig wire and E71T flux cored.

Thanks

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Reply to
Ignoramus18965
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Good luck, you'll need it.

With my equipment and skills, I'd have to find a way to flip it over. If it already broke once, tacking a bit more weld on ain't gonna do it.

Karl

Reply to
Karl Townsend

Proly should post to sejw. Don't know what the spatter situation is like for mig stuff, but if it's anything like stick, get leather headgear -- not too much is worse than slag in the ear.... except for mebbe slag in the eye. Slag in yer socks is no joke either. And a welding jacket,

Overhead welding, at least for stick, requires a lot of practice.

Reply to
Existential Angst

Particularly on a scabby old trailer. Flip the sucker, or at least stand it on it's side, and sandblast the repair area. My preference would be to stick weld it, but that's just me.

Reply to
clare

Mebbe even easier/wiser to skip the welding and bolt mending plates made out of suitable angle iron, etc, if possible.

Reply to
Existential Angst

Yeah, just flip that 16,000 lbs sucker ...

Reply to
Ignoramus18965

You can do it REAL easy. Two chains attached to the tail of your tractor and back to the trailer. Two more under the trailer in similar positions to keep it from sliding. Add two more to stop it when it gets on edge.

Or if you have time two air/hyd. 20 ton jacks. Jack up, block in place. Block jack up and keep going 'til it's at a good angle.

Call a wrecker outfit and have them lift it up. Block it in position. Blast and stick weld it then have them come back and drop it down.

Reply to
Steve W.

Did you see the video of the tornado tossing semi trailers through the air in Dallas recently?

16,000#, and you only have to lift a side and let the weight mostly bear on the other side. Should be easy enough with a forklift and some care.
Reply to
Pete C.

Although, I can't see exactly what you are trying to weld from the pictures, I would recommend stick welding with 7018. Absolutely do not use solid MIG wire. The flux core is a much better choice if you must use a MIG set up. It is not necessary to tip your trailer over as others have suggested, but backing it over a garage pit would help to give you some working room.

Joint preparation is key. You should grind a vee joint between the plates (asumming this is a butt weld) and absolutely clean it out of any paint, rust, or grinding debris using a knotted wire wheel.

If you have no experience running a key-hole type root pass with say

6010, I'd recommend tacking a backing strip to the weld path. Usually a piece of cold rolled steel about 1/4" thick will do the trick. (Grind any mill scale off of it before you use it.) You can cut this off with careful application of an oxy-acetaline torch after the weld is completed. Then grind the remains flat and apply a capping bead over that side of the weld.

The root pass is also key. You must keep a very short arc length with

7018 otherwise oxygen will contaminate the weld puddle. The goal is to lay passes that stack up evenly across the length of the weld. After the root pass you can use weaving passes to make this stack up.....once again remembering to keep a SHORT arc length.

Before attempting to do this on your trailer, do TEST set ups and practice. Overhead takes practice above all else. Dave

Reply to
dav1936531

The easy way would be to go out and hire a welder :-)

-- Cheers,

John B.

Reply to
John B.

I see an 18-wheeler tow truck in Ig's future...

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-- Believe nothing. No matter where you read it, Or who said it, Even if I have said it, Unless it agrees with your own reason And your own common sense. -- Buddha

Reply to
Larry Jaques

I can see you've never worked on a locomotive (:

Reply to
Jim Stewart

Or a surplus tank retriever.

Reply to
Jim Stewart

Get inventive to get easier access - Something so you don't have to kill yourself crawling under there and grinding & welding in extremely confined conditions.

Plus you have to consider emergency egress and access - if for example you manage to light the hydraulics on fire you want to be able to get out in a hurry. Then grab an extinguisher and decide if you want to go back in, or just squirt and pray from outside...

Either tip the trailer up at a 45-degree angle to the side with the forklift, or pick up all four corners a few feet off the ground with a set of Railroad Jacks (what they were designed for!) and crib the heck out of it for safety...

Or bring it inside through the ground level door and run it outside the Dock door with the tail end hanging out off the end of the loading dock over the trailer pit...

Or dig a proper lube pit, and finish it right with concrete block walls and a poured floor slab (with a sump-pump depression too!) and a pair of concrete wheel tracks on the sides, and stairs out the end.

And a ledge on the sides of the pit so you can cover it up with 4X6 and 4X8 cribbing lumber to keep people from falling in when you aren't using it. "Safety's in the Top Three..."

The last one is practical for working on the tractor and other motorized things you have, too. If you're going to use it a lot, make provisions for getting air and power down there (a 2" conduit from the Shop you can snake an air hose and an extension cord through) and make the Sump Pump semi-permanent with a plumbed outlet pipe before you pour concrete.

Or clamp a chunk of Copper Busbar over the other side of the weld (the trailer deck diamond-plate) as a chill plate. That will keep the weld from making a bigger mess if you burn through, then go to fill in the hole.

Overhead also takes lots of protective gear, because the red hot molten steel dingleberries will go places you do NOT want them. Armor up like you're going to work in a foundry.

If you don't trust yourself to do the final welds, find a local Mobile Welder that can come out and do the work after you get it all set up, cleaned up and primed with Weld-Through Primer and make up the repair pieces you want and tack it together to fit.

These are the guys with the big honking Hobart Pipeliner welder filling up the back of the truck, and they can whip out Nuclear Grade overhead welds like nobody's business. Pay attention, you'll probably learn a few things.

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Reply to
Bruce L. Bergman (munged human readable)

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