Sad reminder of the importance of welding

[Dave M7040]

In the late 1960's I was an engineer working for the Canadian Government. My job was to investigate the worst motor vehicle accidents and provide technical expert witness testimony in court.
A tractor trailer (18 wheeler) was pulling a pup trailer attached to the first trailer with a pintle hook and the trailer tongue had a big eye which slipped over the hook.
The whole attachment assembly was welded together by someone who ran beads of grapes and called it welding.
The hitch, chains etc failed on a modern 4 lane divided highway and the pup got loose.
Normally, because the pup headed for the shoulder, it would not have been too big a deal but this time there was a young hitch hiker on the shoulder who could not get out of the way and the pup trailer killed him.
If you are not a certified welder you should not be welding items where, if they fail, people can get killed.
Dave M7040

 

[ultrarunner]

Back in my Machine Shop Days I was certified... had to be because we were working on components for the Space Shuttle Program.

Even being certified... it is a skill that is maintained and honed through repetition.

 

[Walkin Horse]

Sometimes being a certified weldor is not enough. You need to be an engineer and a metallurgist.

A friend of mine wanted me to make him a gooseneck hitch extender. It sets the trailer back farther from the tailgate. I told him of the liability involved and that I really didn't want to do it. He even offered to sign a waiver. I had run my hay spear in the ground and ripped a peice of heavy wall 2" sq. tube. I took that over one day and showed him. I said if I can tear that up with my tractor, do you really want a trailer full of horses jerking on it. The material failure and the design of this extender scared me from wanting anything to do with it.

 

[DarkBlack]

Sometimes being a certified weldor is not enough. You need to be an engineer and a metallurgist.

A friend of mine wanted me to make him a gooseneck hitch extender. It sets the trailer back farther from the tailgate. I told him of the liability involved and that I really didn't want to do it. He even offered to sign a waiver. I had run my hay spear in the ground and ripped a peice of heavy wall 2" sq. tube. I took that over one day and showed him. I said if I can tear that up with my tractor, do you really want a trailer full of horses jerking on it. The material failure and the design of this extender scared me from wanting anything to do with it.

What are you afraid of, to help your friend? Wouldn't a longer gooseneck have lower stress than the original shorter one in the same application?

 

[dragoneggs]

What are you afraid of, to help your friend? Wouldn't a longer gooseneck have lower stress than the original shorter one in the same application?

I do't understand the geometries being talked about here but usually longer means longer moment arm and higher bending stresses.

 

[DarkBlack]

I do't understand the geometries being talked about here but usually longer means longer moment arm and higher bending stresses.

The further from the trailer axle(s), the lower the force.

 

[DarkBlack]

I do't understand the geometries being talked about here but usually longer means longer moment arm and higher bending stresses.

The further from the trailer axle(s), the lower the dynamic force.

 

[dragoneggs]

The further from the trailer axle(s), the lower the dynamic force.

I understand what you are saying I think (tongue load?) but I would need to see the full geometry to understand how the stresses 'everywhere' are affected.

 

[muddstopper]

not sure I am on the same page when it comes to extending the tongue. The weak point should be where the tongue attaches to the trailer frame. Making the tongue longer would increase the stress being applied where the tongue meets the trailer. The weight would remain constant on the trailer frame and a longer tongue might decrease tongue weight at the hitch point, the longer the tongue, the more the stress would be at the trailer where the tongue attaches.

 

[Walkin Horse]

After I replied I saw another thread about short bed trucks and gooseneck trailers. They had a picture of a B&W hitch extender. You pull the ball out and drop this in your gooseneck hitch. It sits the trailer back 3 or 4 inches.
This guy pulls a 40' stock trailer with 12 or 13 horses in it that belong to other people. You think I'm going to just pick up a chunk of steel and fab something to do that with. You start jerking on hitch with 25000# of swaying meat and trailer and 250 gal of water in the nose,you better have someone signing off on it. Plus take scrap material with no way to track the heat numbers.

That's not about geometry or stress. That's about liability that I can't afford,to save him $175. I think there's more to fabricating things than just welding ability that should be thought about. With the litigious society today there could be 12 or more people who want a piece of me. On the other hand he brought me a metal table the other day. I spot welded the broken parts and repainted it for him.

If I can find the tubing that I tore up,I will post a picture of it.