Building weld for strength?

[joe@rivden.com]

Hello,

First time poster here and new to welding. I am wondering if building up weld (mig ER70S-6) has structural strength. I recently purchased a used boat with a triple axle trailer. Everything is galvanized except where the spindles are welded to the axle tubes which have rusted out. I ground the rust off completely and the original 3/16" metal is down to 1/8" in some places so I need to beef this up. I am wondering if I can just build up the weld to increase the thickness and strength or is this something that will look good but not really do anything useful or perhaps too brittle and crack under the oscillating load?

My alternative is to weld 1/8" plate to the thinned out areas but since these are relatively small parts, it would be easy to build it up. Thoughts?

Thanks.

[DSW]

If you are new to welding, trailer projects are not for you. Trailers aren't "learning" projects. Trailers require that you make code quality welds, in all positions, every time.

[jbmprods]

+1 what Mr. DSW said.

[Joshfromsaltlake]

Welcome to the forum, Joe.

If you're a newbie welder, then it's very bad idea.

You do NOT want a FUBAR'ed axle on the freeway, friend. Not under any circumstances.

Have a professional trailer repair place look at it. They could tell you whether it's weldable or whether something needs to be replaced. I'm leaning towards the latter.

EDIT; yeah, what DSW said.....

[gwiley]

I agree with the previous posts - one clarification, these guys mean highway trailers. The reason is that a failed weld on the highway can lead to injury to you and to innocent bystanders.

I recommend that you have a shop do the work - if it can be repaired they will charge something around $70/hour (here in central Va anyway).

Meanwhile, grab some pipe and start playing with your ideas. Try a few things, test them until they fail and you will be well on your way toward understanding why folks come down so hard on new weldors working on trailers. WHen I first started it really surprised me how good a weld can look to an inexperienced eye and how quickly that same weld can fail.

[Sample]

I am guessing there is more rust in the axle than what you are seeing. I think it would be best to replace the axle itself.

[MoonRise]

Axle tube is 'rusted out' from the original 3/16 wall thickness to 1/8 inch wall thickness (or less)?

And that is just in the places you checked?

In general, without seeing any pictures or being able to do a more thorough inspection, that sounds like it is a REPLACE time.

Surface rust happens, but once the tube wall thickness is appreciably (noticably, or easily 'measured') reduced from rust, it's pretty much time to replace "structural" items. With the wall thickness reduced by at least ~1/3 (3/16 original down to 1/8 or less now), the strength of the axle is now suspect.

And an axle tube on a triple-axle trailer sure sounds structural to me.

Replace the axle tubes.

(just 'piling up' some weld metal on a part subject to load variations or vibration certainly WILL negatively affect the fatigue life/strength of the part. And that's if the weld is done well. Do the weld poorly and the strength/life can be easily reduced to 1/2 or 1/4 of the 'original'.)

[farmersamm]

It's generally not a good idea to weld on axles unless you're familiar with the problems which may arise.

This is an excellent reference for welding procedures on axles

http://www.meritorhvs.com/MeritorHVS_Documents/mm14.pdf

If the tube has decayed to such a point as you've described, it's probably beyond repair. Simply adding weld material will adversely affect ductility. First in the application of heat, and second in the difference in ductility of the weld material and the parent metal. Every time a weld is applied to an axle tube there's also an accompanying change in camber. Lottsa stuff to be aware of.

Replacing the axle is the best way to go in this case.

I don't subscribe to the "Oh God the sky is falling" mentality when working on rolling stock. But I do think it should be done only when fully informed as to the correct procedures.

I don't like the way most trailers are built. They're mostly aftermarket "just good enough" designs. This goes for small utility trailers clear through semi trailers. It's the nature of the beast.

[joe@rivden.com]

Thanks for the replies.

farmersamm, thanks for the referenced document, this is helpful.

[TozziWelding]

Throw a new axle under it they are cheap, all things considered.

[joe@rivden.com]

Thats the direction I'm going, but its 3 axles so not so cheap. The rest of the trailer is all galvanized and checks out good so its worth saving.

It is shame on how these are being built. The frame was obviously built very well and protected with a good hot galvanize but just about everything else attached to it is crap. In fact the axles tubes themselves, also hot dip galvanized, are in great shape but the spindles were welding to galvanized tubing and not protected properly. All of the brakes, backing plates, etc. are completely shot so that's all getting replaced.

As ridiculous as my original idea may have been, I don't see that this trailer was originally built and DOT approved with much more thought.

In any case, thank you for the help, especially to farmersamm who's document gave me the details to understand why I need to replace these.