Repairing cracks in aluminum dump trailer

I just bought an '86 Freightliner tractor and 30' dump trailer.

The dump trailer is an aluminum body on a steel frame. It is a 1977 model. Therefore, it's been around the block if not the planet...

Generally it appears to my untrained eye to be in pretty good shape. It does have numerous aluminum patches welded here and there.

But there are also some cracks in it. I have called the manufacturer as to what alloy it is. Their guy told me that they didn't keep records back that far but that he GUESSED it was a 5000 series alloy.

I think he said 5353 but I may be mistaken. I was driving in my truck when we were talking and like a dummy I couldn't find a pen to take notes.

Anyway, a few questions:

First, does the standard advice for repairing a crack hold? I.e. drill a hole at the root of the crack... grind out the crack... clean... weld?

Is an overlay patch appropriate instead of, or in addition to, the above?

Is my Millermatic 250X welder gritty enough for the job? I think the skin is 3/16" aluminum.

Finally, should I be worried about terminal metal fatigue? I don't know much about aluminum but I have heard of trailers splitting in two.

If the trailer holds up for a few more months it will be worth what I paid for it.

Are there any clever ways to get a clue as to what the alloy is?

Is there a magic bullet wire for this? It is obviously weldable as it is welded throughout and patched profusely.

In a nut shell would y'all make me smarter as to aluminum metallurgy and/or repair than I am now? It would take very little to double or triple my knowledge...

The thing is a beaut. When I'm standing beside (under) it I cannot help thinking about the space shuttle.

It is rated to carry 24 yards. Best I can tell that's over 30 tons.

I think I've stumbled into the dirt bidness...

Thanks for all comments.. Vernon

Reply to
Vernon Tuck
Loading thread data ...

Likely it is 5052 and 5086.

Yes that should work nicely.

It can't hurt.

Easily. Buy or rent a 30A spoolgun to run from it and a bottle of pure argon. Get a box of 1 lb. spools of 3/64" (0.047") 5356

Aluminum cracks tend to propagte rapidly if not stopped.

5356 or 5556 filler are your best bets. 5556 is a bit stronger but not as common.

Download and read this pdf from Lincoln.

formatting link
There is an excellent article on aluminum welding.

Also check out the Alcotec's Technical library.

formatting link

I was rather stunned to find out that Motorcross event producers lease their dirt. They hold lease rights to piles of dirt all over the US and just have it hauled to whatever venue they are using.

Reply to
Ernie Leimkuhler

Reply to

Hey Ernie,

I was hoping you'd jump into this...

At present I do not own an aluminum spool gun.

Do I remember correctly that you were singing the graces of a Redi Welder as a viable and inexpensive aluminum spool gun substitute?

The way I'm hemmorhaging money servicing the truck it would be great to save a buck or two on a usable spool gun.

I'm shooting for May 1 as the date I'll be legally authorized to operate as a Texas Motor Carrier. On the heels of that I hope to start hauling road base for a family company.

Therefore, getting those cracks under control is not the least of my worries.

In light of the above would you, Ernie, or anybody and everybody else, tell me how a poor boy can get into position to weld aluminum with a Millermatic 250X, with the smallest possible investment in a spool gun?

Someone once told me he had great success by shortening the sheath of a regular (steel) feeder and then setting the machine, the shortened feeder, AND the work to be welded on a table top.

Of course it would take a fair sized table top to set the 30' trailer on...

So what about it? Will a Redi Welder do the trick?

Enquirin' bird-brains wanna know.

Thanks! Vernon

Reply to
Vernon Tuck

running the 5356 out of a 10' snake you may not even have to worry about the spool gun...

Reply to

Yes, it should be fine.

Reply to
Ernie Leimkuhler

Yes, I have had mine for about 2 years, and love it. Under $500 for everything, and you can run it off of anything.

formatting link
Mine is a model 10250, which is designed to run from welding power sources.

The model 10000 is designed to run from batteries. Both guns will do both jobs, but the default cables are different.

Miller also makes an economy spoolgun, Spoolmate 3545, that will fit the Millermatic 250X, it is only about $600 instead of $1000, but it requires a $250 control box to put it on a 250X. The Miller 30A just plugs in to the face of the 250X.

I think the Readywelder 10250 is an excellent choice for this job.

You will need to figure out how to get the trailer inside a building or rig up some serious wind blocks since aluminum MIG requires a Argon or Argon/Helium shielding gas.

Weld up some practice pieces to get your settings dialed in. This includes cutting them up and breaking the welds.

Aluminum MIG can make pretty welds with no strengh, if you aren't careful.

Once you figure out your settings, write them down, for each type of joint.

Reply to
Ernie Leimkuhler

Ernie, Randy and all... I have acquired an 18 lb. roll of 3/64" aluminum roll in the 5356 flavor. I am going to attempt to run it through my regular MIG cable/hose. Numerous sources have told me it will feed.

Now I have some related questions for which I beg your collective indulgence and sagacious advice...

The dump trailer in question has numerous rectangular patches over it. I haven't measured the thickness of these but I'd guess they're about

4" wide by 1/4" thick and of varying lengths. I also assume but do not know, that these were overlay patches to repaired cracks.

I want to acquire some aluminum bar stock to use for the patching I do. In that regard,

a) Should I use the same 5000 series alloy for the patches? b) Is 1/4" better than say 3/16" or even thinner material? c) Where does a guy buy this kind of material? I live in a small Central Texas town. We have a metal supplier but they don't do aluminum. I need to locate the stuff pretty quick even if it means traveling to Houston or elsewhere. d) Is any kind of generalized pre-heat or post-heat necessary or advantageous? e) Would a high speed die grinder with a burr open up these fatigue cracks? f) Ditto a router and carbide cutter?

Now, discussing the tailgate area:

The tailgate frame has some air operated steel latches which cam around, grab, and latch the tailgate. It looks like the latches were from another trailer because the holes in the steel do not match the threaded holes in the aluminum.

There is also some fatigue cracking in this area. I am considering drilling, gouging and re-welding these fatigue cracks but then building a steel angle iron framework around the back of the trailer in order to spread out the stresses of the banging tailgate.

Although I haven't worked out the details of this the general idea is to take some wide flange but relatively thin gauge angle iron and frame around the back. Thus, where the steel latches are now affixed to the aluminum with four 5/16" bolts which screw into threaded holes in the aluminum spaced at the corners of an approximately 3" x 4" rectangular area, which shows signs of fatigue cracking, the idea is to "turn the corner" with the wide flange angle iron and thus sink threaded holes into relatively sound areas of aluminum across a much wider impact area. I hope that made sense.

The question on my mind is, and to borrow (and perhaps butcher) an engineering term I probably don't even understand, is the coefficient of expansion of the two metals (aluminum and mild steel) likely to be an issue?

In other words, are the two facing surfaces going to expand at different rates thus propagating additional cracks?

This trailer is certainly in the late autumn if not late winter of its years. It doesn't have to stand up to 15 hours per day at maximum loading because I am not intending to make a living with it.

However, I do have a pressing need for it. Therefore, I want to do this repair the smartest way possible. Conversely, I would find it quite embarrassing to have the thing split wide open while going down the highway and spilling 40 tons of clay gravel on the roadway.

I will try to take some pictures of the trailer tomorrow. Hopefully I'll get them uploaded to my web page so that all you designers can pipe up and give me your views.

This endeavor has been exciting yet scary, too. The Texas DOT mirrors the requirements of the federal DOT. If you put a big rig on the public thoroughfares of Texas it had better be safe!

And of course, that's a good thing. So I'm eager to do my part.

Best wishes and many thanks to all. Vernon

formatting link

Reply to
Vernon Tuck

whoah!! great idea (running straight snake for aluminum with the 5356), but you're supposed to use different liner and make super sure your rollers are very clean

Reply to

(big snip)

I would recommend buying some 1/4" 5052 for your patches.

Houston should have a non-ferrous metals dealer.

5052 is very common stuff.

Warming the area with a big propane weedburner can't hurt, but really isn't necessary unless you are dealing with 3/4" or 1" plate.

Like a can opener.

Much scarier.

Your best bet is to through-bolt the aluminum with a steel plate on each side, after repairing the cracks.

As long as you use lock washers, locktite or nylocks, vibration should be a big deal.


Reply to
Ernie Leimkuhler

Probably not an issue here given the piece of equipment in question but aluminum and steel touching each other will corrode and essentially grow together making a nearly impossible to break free seal. Galvanic corrosion I think.


Reply to

Locally a chip trailer outfit does the anti corrosion thing by placing duct tape between steel and aluminum before bolting together. It seems to help. Major failure of tailgates is driver forgetting to open latches before lifting to dump. The aluminum gates are just not designed to take the full weight of the gravel/sand. Randy

Reply to
Randy Zimmerman

Ernie, Randy, and anybody else who has an opinion to share:

Last week I ordered some Alcotec 5052 wire in 3/64" dia. along with the appropriate rollers, feeder nozzle (or whatever it's called), an "aluminum conversion" kit for the MIG gun (consisting of teflon liner) and some heavy duty tips, all for a Millermatic 250X mig welder.

However, it did not arrive in time to do anything this weekend. Supposed to be here Monday.

On Friday I bought a few drops of 5052 aluminum sheet in 3/64", 1/8", and 1/4" 5052. The supplier did not have any 3/16" in anything less than full sheets, which were more than $200.

Unlike some aluminum trailers ("Travis type") which are built solely of aluminum, this trailer (Benson made in W. Va.) has an aluminum box mounted on a steel frame.

We had already discovered a significant problem with the rear axle of the trailer.

Today I drove up and did a crawl-around inspection of the dump box as regards the needed fatigue crack repairs. As I believe I stated at the beginning of the thread on this saga I don't know much about the metallurgy of aluminum. But I think I know enough to be rightly scared as regards not only how to make proper repairs, but also, as to whether I'm knowledgeable enough to know whether the money I'm poised to spend on this trailer will be an investment or instead, I'm throwing money down a pit.

There are some previous crack repairs which have cracked again, right through the middle of the welding bead. Other repairs appear to be holding up.

It is interesting that the repairs that appear to be effectively done also show a much better bead than the ones that have cracked again.

Obviously, the repairs were done by at least two different people. Some of the beads are just awful. They look like chewing gum just stuck to the top of the metal.

I have been in touch with a technical support guy named "Tex" from the Benson factory. He explained to me that over the years (in this case nearly 30 years!) aluminum sucks up all kinds of contaminants. He went on to say that even after grinding out and cleaning the parent metal, I should expect to get poor results due to this crud cooking out of the pores and rising to the surface of the weld.

He assured me that provided I do not get discouraged, but just keep cleaning, welding, re-grinding, re-cleaning, and re-welding, the stuff would finally cook out and I'd get satisfactory adhesion and a sound weld.

I have decided that if I can find a professional welder, preferably one with experience with repairing dump trailers, and can afford him (her) I will pay to have this work done even though the do-it-yourselfer in me wants to er... do it myself.

One concern however, is that no matter who does the work, it may have to be done outside due to the size of the trailer.

I have three welding processes available to me to do this work:

a) a Millermatic 250X; b) a Henrob (Dillon) oxyacetylene torch and two stage regulators; c) a Syncrowave 500 square wave welder with pulser.

However, I don't have even one centimeter's worth of aluminum welding experience with any of these.

Most of the required welds will be on vertical surfaces. Some of these will be at joints between stiffeners and plates, which are at about a 45 degree angle.

In summary, we have not yet begun these repairs. And it is likely that some are needed that I haven't yet detected.

Meanwhile, back at the axles, I'm on the brink of a decision as to whether to do a minimal repair or a complete rebuild of the suspension system.

Although I don't yet know the cost of a complete suspension rebuild I would be significantly more confident - and therefore inclined to incur this expense - if I better understood the future prognosis for these welding repairs.

In a nutshell I'm afraid I'll have a steel chassis in tip-top condition with an aluminum body dump box sitting on it for which sustainable repair is not cost effective.

So I guess what I'd really like to receive from y'all is "the voice of experience" of somebody who's been involved in REPAIR welding of old aluminum equipment. If your experience is specific to aluminum dump trailers then I will jump for joy.

On Monday I'm also going to attempt to find somebody in Houston or elsewhere. If somebody out there in this newsgroup knows or knows of such a person I will truly appreciate your bringing us together by phone or email.

Finally, if Ernie reads this, I will appreciate his guidance on which of the three processes I have available to me would give me the best chance of success. When I bought the Henrob (Dillon) torch I watched a video that came with it. The guy repaired a crack in an aluminum cylinder head.

He made it look dead easy. However, he WAS welding in the flat position. I (or the person I hire) will be welding mostly vertical and in a few instances even overhead.

If anybody believes I've asked the wrong question or that there's an angle I haven't considered I'll appreciate your feedback as well. In other words, even if I didn't ask the question feel free to answer it!

I wonder if this is a contender for most long-winded query ever posted in this newsgroup??

Best regards to all, Vernon

Reply to
Vernon Tuck

or that there's an

somewhere i recall you indicating that you were not essentially planning to use the finished product (the roadworthy truck & trailer) yourself, that you were looking at this entire project as an investment. if so, one question that comes to mind (in developing an investment strategy) is are you going to be doing it again (find another "dead" aluminum trailer to restore for re-sale)?

Reply to

All aluminum fatigues, so there's always going to be cracking problems with anything aluminum that vibrates or flexes. Why not just buy a steel bodied trailer? That won't fatigue crack if it isn't repeatedly overloaded past the fatigue limit. It'll weigh more, so you'll have to haul a little less per load, but that may be a good tradeoff.


Reply to
Gary Coffman

Gary and everybody,

I would have preferred a steel trailer. It just happened that I found this trailer and tractor too, at what SEEMED like a great price. And even with the unforeseen problems and expenditures I'm still fairly confident.

Of course it is natural to fear that which we do not understand. And I do not understand aluminum.

A previous poster seemed to recall that I'd said I had bought the tractor and trailer as an investment to fix up and re-sell.

Not so. The plan is to develop a 13 acre patch of deep sand which has about 1300' of frontage along a very busy state highway. Generally, it's high and dry. But the very middle of the property has a swag across it. In fact, there are three depressions across it.

The plan is to use the rig to do my own landfill, grading, roadbuilding, and building site preparation. When I say "do my own" I really mean to say "help Larry do it". Larry is my driver and new employee. He's also family of sorts in that he's taken up housekeeping with my wife's aunt.

The guy knows trucks, machinery and equipment like I know Spanish dictionaries... from cover to cover pretty much.

Now, back to the matter at hand. Larry says that it is entirely feasible to retrofit the trailer with a steel body. He has indicated that they're pretty much built to a standard and that there's nothing to stop us from doing that.

So all I have to do is wait for a steel body to float by. However, in the meanwhile, we have to make do with this one.

In addition to the project for myself my family has the need to do some roadbuilding. In fact their project is far larger than mine.

Therefore, if I can get up and running, and provided I'm no higher than the low bidder, I should be able to pick up a hauling contract which will at the very least defray the cost of buying the equipment, and possibly pay for it and then some.

The tractor, an '86 Freightliner, is almost good to go. We've been over it from end to end, servicing fluids, replacing gaskets and seals, and tweaking the brakes and driveline. Everything we've done we've done the right way - for the long haul.

It's now that we're turning our attention to the trailer that I'm a little nervous. I'm at a cross roads as to whether to go through the suspension for a complete rebuild (new bushings, shackles, seals, etc.) or fix it just good enough to get up and running (a repair to the "spider" on the right rear axle).

And the unknown quantity is the near-term future serviceability of the aluminum dump body.

Last night, right after posting, I did a google search and found a very useful exchange between Randy, Ernie and some others (2002) about a botched repair to an aluminum truck frame which was in the process of cracking all the way through while laden with a gravel trailer. There are some pictures in the 2002 closed files dropbox entitled aluminum abortion 1 through 4.jpg.

In the final analysis I'm probably asking y'all an unanswerable question: "Is an old aluminum dump body worth repairing?"

I understand that aluminum fatigues over time. I suppose what I'm trying to figure out is: "As time goes by does fatigue cracking exponentially increase to the extent that even diligent attention to repairs will not keep up with it?"

I am striving to believe that what may not be expedient for a hardcore gravel hauling operation running maximum loads 10 - 12 hours per day, could still be practical and reasonable for me. This is a 24 yard trailer. If I load it to one-half its capacity this is acceptable even if it's less than ideal.

The pivot point of this issue may well be that "it's worth repairing if I do it myself but not if I have to pay somebody".

Provided I can find somebody specialized in repairing aluminum dump bodies I will probably hire 'em, especially if I can peek over his/her shoulder and learn to do it myself.

As always, I will appreciate everybody keeping this discussion alive. Over the years I've morphed into an almost competent DIY welder thanks to the contributors to this group.

You're the best! Vernon

Reply to
Vernon Tuck

I forgot a couple of things.

If I MIG weld the cracks should I go for "globular" or "spray" transfer. Last night I found a chart that Ernie generously contributed to the dropbox which contained approximate settings for both these.

The skin of this trailer is either 1/8" or 3/16". I think it's the latter but it's hard to tell since the metal is sort of curved around in those places where it's been torn.

The other question is: Can I drill both ends of the crack, gouge, clean and weld the crack from both sides, then grind the outside bead flush and overlay with a patch? I saw some clever advice from Randy and Mike about how the patch should be "fishplated" in a shape and/or position such that the weld beads are not vertical but rather angled, in order to prevent stress risers. Randy also mentioned start and end tabs so as to avoid dimples where the weld bead ends.

I assume that placement of a fishplate requires the crack fill weld bead to be ground down flush.



Reply to
Vernon Tuck

ever wonder how or why the old trailer became fatigued?? maybe it was over loaded and ran hard on very rough terrain. if you weld up those cracks and sheet with some re enforcement, it very well may last you into the next century with some careful driving

Reply to

In flat position, you can use globular or spray. For vertical or overhead you'll need to use either short circuit transfer or pulsed spray. I'd try to avoid globular transfer altogether simply because it produces so much spatter.

You'll likely have gaps to fill in the torn areas. Short circuit transfer does that best. Welding against a chill plate may also be helpful (see below).

Randy gives good advice. But to clarify, what you want is to place the patch welds so that they aren't perpendicular to the axis of maximum strain. For a truck chassis, that would typically be at an angle to the vertical. But on a dump bed repair the angle isn't so obvious. You need to visualize the direction of maximum strain at the particular point of the repair (which may occur when the bed is raised), and avoid placing a weld seam perpendicular to it.

The area needs to be flat. But there's another way to do this if you have access to both sides. Stop drill and Vee grind the crack on the opposite side from the patch. Grind flat on the patch side. Install the patch. Then weld up the crack. The patch then provides a backer for the crack weld. This should reduce chances of burnthru, and also allows you to fill gaps in the torn metal.


Reply to
Gary Coffman

I'd want the suspension and running gear in good shape. A failure on the road could be catastrophic.

Fatigue is cumulative. You're already seeing cracks where the fatigue has accumulated to the greatest extent, but much of the rest of it may be close to end of life too. It isn't likely to suddenly crack into a million pieces, but the number and severity of cracks is likely to increase fairly rapidly now.

I can't answer that. But you probably will be patching it a lot, so doing it yourself may be the only economic answer.

The real question is whether you can afford to have it crack and fail on the road. If it fails on your own property, it is just a nuisance, but if it fails on the road it becomes a public hazard. So you have to ask yourself how much risk should the public be asked to bear as a consequence of your decisions.

In sue happy America, I tend to err on the side of caution. The decision to repair or condemn the trailer really needs an expert in person inspection and evaluation of the trailer. There's no way we can say what to do here with the limited information available.


Reply to
Gary Coffman

PolyTech Forum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.