Trailer sauce advice

[jwiereng]

Trailer sauce has several excellent articles and drawings on their website http://www.trailersauce.com/


They have an several articles on tongue design, and one of them is about composite tongue.

They advise builders "Do not under any circumstances weld across the horizontal faces on the tongue where it intersects the cross members as shown below."

While advising builders as to where and where not to weld it does not cite reasons.
I am unsure why one should not weld on top.

I would like ExPo members to weigh in.

 

[PCO6]

I'm curious about this too. I built my utility trailer using the same basic design as above and welded the frame in the spots where they say not to. I also welded the undersides of the contact points in the same locations. It's seen a LOT of use over the past 5 years and although most of those spots are now covered by floor boards I can't imagine that the welds are failing.

 

[Ozarker]

That makes perfect sense when we look at a tilt trailer.

 

[sunnybean]

The only thing I could think of is maybe the torsional load as the trailer tries to twist. Maybe. I'm not an engineer.

I went out and looked at my PJ trailer. Itis welded like they say not to and I have severely overloaded it with dirt and gravel multiple times without any issues.

 

[Scoutn79]

Both of mine and both of my friends trailers are welded at those point also, two are campers and two flatbeds. Sure would like to hear the reasoning for not welding everywhere you can myself.
A 3 point mount (2 tires and ball, not a fifth wheel plate) won't have any torsion on the structure under normal use.
Darrell

 

[jwiereng]

Pretty sure the drawings are not for a tilt trailer. They author does call for welding under on the tongue.

Perhaps the author thinks some detrimental effects of welding on the tongue.

 

[Scoutn79]

Looking at the direction on the website they don't want the welds on top but underneath which still gets a weld at the intersections but at a 90 deg angle to what you would have if you welded on top...wonder why the change in direction???
Darrell

 

[Trailersauce]

Hi everyone,

The reason for not welding the top face of the tongue (drawbar) and most importantly across the front of the angle gusset is that when steel is welded, the heat from welding process alters the crystalline structure of the steel and creates a "heat affected zone" or HAZ. This HAZ is generally weaker and prone to cracking depending on the circumstances the welded section is placed under.

The tongue does a lot of work while towing. Every little bump in the road and every turn you make transfers stress through the tongue and compresses, twists and stretches the tongue material constantly. The majority of this flexing occurs where the chassis and tongue are connected and is enhanced when the trailer is constantly overloaded or unbalanced. This repeated loading and unloading (cycling) of stresses on the tongue can create microscopic cracks within the grain structure of the tongue material especially around the HAZ.

Over time a microscopic crack can grow, and potentially reach a critical size, to a point where the tongue may suddenly fracture and ultimately fail.

Fitting an angle gusset over the tongue top face gives addition area for supporting the load placed on the tongue and reduces the potential for tongue failure.

 

[jwiereng]

Good to see you on ExPo now.
Thanks for the post.

 

[Brettski]

Hi everyone,

Fitting an angle gusset over the tongue top face gives addition area for supporting the load placed on the tongue and reduces the potential for tongue failure.

Sorry to resurrect an old thread, but will someone explain this to me? Getting read to fabricate and a) not sure where this gusset is supposed to go? and b) if the angle gusset is a triangle that gets welded to the side of the tongue member, then how is that stronger than welding the frame member across the top? We're still laying a bead across one face. Thanks

 

[azscotts]

I'd say weld everywhere. I did. And judging from the responses last year, everyone agrees.

That looks like a composite addition to a single tongue trailer. See here: http://www.trailersauce.com/information/draw-bar-design/trailer-drawbar-design-function/

About halfway down it talks about adding composite support.

 

[Lmg]

I saw this when it was posted, but am just now getting a chance to respond.

Disclaimer: "I am no expert on this, except for I have worked for years around certified welders and welding inspectors, and have also welded my own projects for years."

The explanation of the heat affected zone (HAZ) given in post #8 could have been more detailed. A better explanation can be found here: https://app.aws.org/forum/topic_show.pl?tid=125

The reference also gives information on how to minimize the HAZ, including the use of preheating. If you are fabricating your project in the wintertime in a cold space, I suggest that you always preheat.

If you have seen a tensile strength test on a weld, you will notice that on a good weld, the failure always occurs in the HAZ.

Especially the tops and bottoms of the tongue and the main frame rails are subject to tension and/or compression, and can alternate between the two.

Placing a weld anywhere creates a HAZ on each side, parallel to the weld, as well as creates stresses in the weld and base metal, so there is a lot more going on here that one would expect.

If you want some information on the how critical welding on a frame can be, google welding procedures on truck frames. You will find welding forums on this subject, and you will find welding procedures from the truck manufacturer's engineers as well. Generally all welding is prohibited by frame manufacturers on the top or bottom flanges. Granted there is the potential for much greater liability from an improper welding procedure on a commercial truck frame, but the principals of the frame loading are the same as on our much smaller trailers.

Another potential for cracking that I have frequently observed is the crater at the end of a weld string. You should pause at the end for 2-3 seconds and allow this to fill in.

A lot of our smaller trailers manufactured by smaller companies who have no engineering staff, and who do not employ certified welders, so they are not aware of these issues. And usually there are no issues, but usually when someone learns the correct way to perform a task, they will stick with it.

Welding is much more technical than most of us realize. As far as I know, Ohio State University has the only ABET accredited welding program in the US. Starting pay for these graduates is equal to a chemical engineering graduate with 100% placement pretty much guaranteed after graduation.

Personally, I do not weld in these areas and will use automotive seam sealer in an attempt to keep out water and rust.

The welding industry has a saying: "sometimes the best weld is no weld."

If you are serious about welding, I suggest attending some classes at the local vo-tech. Many of them have good relationships with the AWS and excellent instructors.

 

[Brettski]

I guess the follow up questions would be since all welds create HAZ, just how much does it weaken the metal? Say a 20% reduction in strength may not mean much on 11 gauge square stock that isn't bearing a load nearly close to its potential load. On truck frames, this is probably in the ballpark of failure, but on a teardrop? I don't know, but maybe someone else does?

And practical question is how to get around it? Seems like not welding the top was the answer, but why? How to buttress properly?

 

[Steve83]

I know this is an old thread...


The HAZ doesn't weaken the metal - it makes it more brittle. There's a difference. Glass is very strong, but it's brittle (in any size thicker than a fiber) which means it doesn't flex much without breaking. So the HAZ has no substantial effect on strength, but it makes the structure less-able to withstand oscillating stresses (like rolling down a road, or off-road).

The reason not to weld the top of the tongue channel is that it would run ACROSS the most-loaded member (the tongue channel). So that would be like cutting a notch across that channel - it makes the tongue MORE-likely (but not necessarily LIKELY) to crack & break off. Welding ALONG the tongue (on the bottom of the crossmembers) is much safer because a crack along the weld would only affect the crossmember - not the tongue.

The original article isn't saying NOT to weld the crossmembers to the tongue channel - it's saying to weld them ALONG the tongue rather than ACROSS it.

 

[jmnielsen]

I know this is an old thread...


The HAZ doesn't weaken the metal - it makes it more brittle. There's a difference. Glass is very strong, but it's brittle (in any size thicker than a fiber) which means it doesn't flex much without breaking. So the HAZ has no substantial effect on strength, but it makes the structure less-able to withstand oscillating stresses (like rolling down a road, or off-road).

The reason not to weld the top of the tongue channel is that it would run ACROSS the most-loaded member (the tongue channel). So that would be like cutting a notch across that channel - it makes the tongue MORE-likely (but not necessarily LIKELY) to crack & break off. Welding ALONG the tongue (on the bottom of the crossmembers) is much safer because a crack along the weld would only affect the crossmember - not the tongue.

The original article isn't saying NOT to weld the crossmembers to the tongue channel - it's saying to weld them ALONG the tongue rather than ACROSS it.

Good explanation. That is how it was explained to me a while back by a very smart welder. He said you don't want to weld across the trailer, you want to weld along the length of the trailer.