Aluminum Trailer Repair Yucky

[William McCormick]

I was all set to enjoy my day off and then this rolls in.

Once I ground open the plate I saw just how bad the damage was. It was a poor design no matter what the person did with the trailer. Even if he went off road with it this should not have happened.

It did not look too bad at first. But when I ground off the plate they poorly welded in, it started to look a bit gruesome. The guy borrowed the trailer so he wants to return it good working order.



The other side was actually worse as far as the I-beam goes. I think the guy just wanted us to run the MIG over it and call it done but that really would not have fixed much in my opinion. So I ground out all the corroded material and got to some good meat.



It was pretty ratty and the U-bolt holes were cracked and distorted, so I just ground away everything bad. I might cut some plates to weld over the U-bolt holes it will help everything.



Then I put a little adjustable clamp on it and it bent back into place like it was made of silly putty. That clamp can exert 7,500 pounds. It has never failed me.



These are the discs I used, they are a bit pricey and you cannot get them from Home Depot but they are worth it. I got them from Coast Welding here by me.



When you grind aluminum you should definitely wear a respirator or at least a really good dusk mask.

Maybe after lunch we will weld it up. Or maybe not, Haha.

Sincerely,

William McCormick

[swampwelder13]

You gonna tig or Mig it?

[William McCormick]

You gonna tig or Mig it?

MIG 99 percent of it, Maybe TIG to touch up, or get in some strange place. It is hard to match the heat that the MIG can throw down from a push pull system.

Sincerely,

William McCormick

[welderj]

Could you post more pics of the trailer from a bit back that shows more of the frame. I would like a better look because I like to know why something broke so I can learn from it, maybe keep from making the same mistake myself in a trailer build. Maybe a brief description of what happened to cause the break.

[William McCormick]

I don't think it was a break but rather a slow destruction. Just a poor design in my opinion.





Sincerely,

William McCormick

[William McCormick]

They hung all the weight of the boat, from the bottom flange of the I-beam. Not good from an engineering point of view. I-beam flanges are designed for compression type loads. Not hanging loads.


Sincerely,

William McCormick

[William McCormick]

They really should have extended the U-bolts through the top flange of the I-beam.

And the single bolt as well. Even then, they should have put a 1/2" plate over the flange, to act as a washer.

Sincerely,

William McCormick

[Brink, M.E.]

Really shouldn't have bolted through the flange period. I'm sure you can take care of it though, good luck and charge well!

[Gamble]

Is it just that one spot you are welding?4043? What's a repair like that cost? Looks like you can get it done in an hour ?

[welderj]

Is there breaking on the other side or at any of the other cross members?

[William McCormick]

Really shouldn't have bolted through the flange period. I'm sure you can take care of it though, good luck and charge well!

On an aluminum I-beam I agree with your argument, the less holes the better. But you know the modern collegiate cadd team. I would not have been concerned, if they bolted through both flanges, and put the weight on top of the I-beam.

Sincerely,

William McCormick

[William McCormick]

Is it just that one spot you are welding?4043? What's a repair like that cost? Looks like you can get it done in an hour ?

It took me an hour at the welding supply today, to pick up the discs. Ha-ha. Then an hour to get out the tools, wrenches, and chords, unbolt all the stainless hardware, cut the wiring harnesses out of the way, and then make a decision on what to cut out and grind out. I am not going to weld it, my father is tomorrow. I will be back at work. This was my vacation. Hopefully I can get some pictures of it done.


Sincerely,

William McCormick

[William McCormick]

Yes both sides left and right of the trailer failed. The crack is right through both of the I-beams. Everything else on the trailer seems ok. That is the point on a trailer that takes most of the load. It was just such a lame way to mount the cross member.

Sincerely,

William McCormick

[welderj]

I think you might have misjudged the reason for the break. The first thing I saw was that the crack didn't look like a tear break as you would get if your theory is correct. A tear would be more jagged than what you have and wouldn't follow a straight line. Your breaks all follow perfectly along the bottom flange in a nice straight line. You also have the cracks on the outside of the holes which are more common with fatigue breaks from flexing or vibration. What I think you have, and my thoughts are worth what you paid, is a perfect example of frame flex as I've talked about before from not having a cross member at the bend in the frame.

I say this for several reasons, first is the straight lines of the cracks. Second, if you look at the breaks before grinding you can see they are significatly worn from rubbing. If it was a tear break from too much down pressure the flange would just drop and not rub. Also if you look at the dip in the flange you can see the dip is shorter than the crack. If the crack was from tearing I think the dip would be the full length of the crack.

I think the problem comes from several things that came together here. First, most boat trailers are made from tube which resists the twisting much better than I-beam. They also put a long radius in them rather than the sharper bend in this trailer. If you take that and the fact that boats are supported mainly at the front and rear, they are able to get by. With the use of I-beam and the sharper corner this one became a problem.

So in my opinion what happened here is the cross member held the bottom flange in place and flat, and the top flange flexed in and out from normal frame flex that wasn't stopped by a propper cross member there, causing a fatigue crack along the bottom flange from the bending back and forth of the web.

What this does for your plans for the repair, if you even believe me, I don't know. If your interested I could give an idea of what I would do. The only way to stop the frame flex is a complete redo of that cross member, and I'm not sure that's called for here. Certainly not without a consult with the owner and a lot more $ involved.

[William McCormick]

Yea I think we are on the same page actually.

I believe both agree it happened over time. I believe if they had put the U-bolt through the top flange as well, that would have stopped the destructive flexing.

When you bounce a couple tons of boat, on a trailer like that, and there are three half inch bolts only through the 3/8" thick bottom flange, of an aluminum I-beam, I am sure the flange is going to give first. I do not know if you can see in the pictures, but it bent the bottom flange of the I-beam on both sides down, well below the part of the flange connected to the web. On one side it was one half inch below the web area.

Without getting the load to the top of the I-beam I doubt highly it will be a permanent fix. But I do not think anyone wants to flip for that job.

Sincerely,

William McCormick

[walker]

Most likely the cause is a lot simpler than you guys are making it out to be. I would guess that it was too heavy a boat out on a borrowed trailer. The whole rented mule story. The original owners boat may have exceeded its capacity as well. I do agree with the poor design part of it though.

[William McCormick]

What I am saying is, if you put a U-bolt through the top and bottom flanges, with a half inch plate over the top flange to act as a washer to keep the flange from bending. When you tighten the U-bolt, it will not let the i-beam cant back and forth. You are saying the same thing recommending them mount the braces between the i-beam. I actually like the U-bolt, but not just to the bottom flange.

Sincerely,

William McCormick

[William McCormick]

If you look at H-beams that hold up I-beams, in older bridges and buildings. You can see the gussets they make out of rolled angle iron and flat plate. Each one of those gussets supports in only one direction. The compression direction. If you remove one and open the other you will see everything just warps and bends. That is what they did not calculate here in this trailer. I beams are only for compression. You cannot hang anything off of them. Even though today you can see it all over. It is just dead wrong engineering.

Sincerely,

William McCormick

[bassboy1]

Most likely the cause is a lot simpler than you guys are making it out to be. I would guess that it was too heavy a boat out on a borrowed trailer. The whole rented mule story.

I've seen that very same damage in the same location on a handful of similar trailers that weren't overloaded (I know the boat/owner), at least per the placard. I've also seen that same scab plate welded in as a repair by a handful of different shops.

First, most boat trailers are made from tube which resists the twisting much better than I-beam.

Steel ones, maybe. A large majority of the aluminum boat trailers in this area are I-beam, just like the pictured one. Well, trailers of this size, at least. The little aluminum trailers (under 2000k gross weight - jet ski trailers) are often tubular aluminum, but that's not what we're looking at here. The 3500-8000 gross weight aluminum single, tandem and tri axle trailers are I-beam. Also, they are entirely bolted - no welding. Some use U-bolts, others simply use bolts through the flange.

Not saying anything for the quality of the design. Just pointing out how commonplace this design is.

[welderj]

What I am saying is, if you put a U-bolt through the top and bottom flanges, with a half inch plate over the top flange to act as a washer to keep the flange from bending. When you tighten the U-bolt, it will not let the i-beam cant back and forth. You are saying the same thing recommending them mount the braces between the i-beam. I actually like the U-bolt, but not just to the bottom flange.

Sincerely,

William McCormick

I think you would be right about the longer bolts and top plate, but then I would question whether the cross tube was strong enough to stop the flex. I think without a stronger cross member you would just end up with a broken cross tube. I just now realised this is the second repair, I thought that plate was factory at first. This is very clearly a candidate for some serious rebuilding. Will you inform the owner or just let them figure it out? I always hate when I have to do that. Most times I will, but if they are known whiners I sometimes will let it go.

[welderj]

I've seen that very same damage in the same location on a handful of similar trailers that weren't overloaded (I know the boat/owner), at least per the placard. I've also seen that same scab plate welded in as a repair by a handful of different shops.



Steel ones, maybe. A large majority of the aluminum boat trailers in this area are I-beam, just like the pictured one. Well, trailers of this size, at least. The little aluminum trailers (under 2000k gross weight - jet ski trailers) are often tubular aluminum, but that's not what we're looking at here. The 3500-8000 gross weight aluminum single, tandem and tri axle trailers are I-beam. Also, they are entirely bolted - no welding. Some use U-bolts, others simply use bolts through the flange.

Not saying anything for the quality of the design. Just pointing out how commonplace this design is.

I've seen them like this even here where large boats are less common, I never paid any attention to them before tho. I can see why this is a common problem and I wonder why it hasn't been addresssed by now.

[William McCormick]

Oh yea the plate was definitely a repair, or sometimes a factory recall thing. Years ago we did some recall emergency work for a company that made trailers. Guys from Florida up for racing in New York would lose one of three wheels off their trailer on long trips. I do not even remember what the fix was anymore. But it was good money and retard simple. But it was silly like that plate.

Sincerely,

William McCormick

[William McCormick]

Yea, I can see your point about the cross member collapsing. You could drive a nice 6" - 12" long solid square bar into the end for a cheap fix. Saw it off a rectangular bar.

Cut off, or Drop off stock, under 20" long, is easy to find, and cheap.

I doubt it will go that way though.

Sincerely,

William McCormick

[William McCormick]

Here is where the rubber met the road. I just got home to get some pictures, it is being picked up in a few minutes. The customer just wanted us to weld over the existing failed plate fix. So he will be happy.







I think I called it with "Yucky", Ha-ha. It should be a marked improvement over the original though. That trailer is getting old it is actually deeply pitted. My father said it welded like garbage.


Sincerely,

William McCormick

[Gamble]

I'm sure it did. Was it anodized?