Draw Bar failures-Picture added

[PaulC]

Hi All, I've noticed that a lot of the trailers over there have the draw bar welded at the front of the chassis meeting point. Over here we do not weld that particular joint so as to minimise drawbar failure. Do any of the engineering gurus (Andrew) have a way to explain to me why there would be this difference. Maybe this pic of Woodbutcher's new frame will help:
Cheers
Paul

[Bandit]

I notice that this post has had alot of views and no replys.
Can you give use a better description of what your are talking about or how about a picture.

Are you refering to why people weld across the top of the tongue where it meets the main body of the frame?
And are you refering to heat stress that may make this point week?

[Miriam C.]

Hello there.
When I hear drawbar I think of the thingy that the ball is attached to. The other end (female) is what I call a coupler. Mine is welded to my dismay. You are right about the possibility on needing to replace it.

Miriam

[PaulC]

Hi Miriam, I stand corrected with my description. Over here we call it a towbar(the part on the car). The part on the trailer is either the a-frame or tow hitch frame. Either way, why do some weld that particular point as we have found it weakens the a-frame, especially when used in off road situations.
Cheers
Paul

[doug hodder]

I dunno Paul...maybe cuz over here, it's a normal position weld, and where you are in the Southern Hemisphere....it would be an overhead weld...trickier to do... Doug

[Miriam C.]

I dunno Paul...maybe cuz over here, it's a normal position weld, and where you are in the Southern Hemisphere....it would be an overhead weld...trickier to do... Doug

Sorry.

Perhaps it is the expected use. My trailer was intended for campground use, complete with stove and fridg. I really don't like the coupler welded cause I might want to change it. Not sure if it is stronger with the A welded or not but there is a connecting plate top and bottom with the jack in the middle. Seems strong enough.

Miriam

[Artificer]

A while ago I was reading something from a rollercoaster maintenance guy. He was deriding a new employee about welding all around an attachment bracket. Acording to him, you only weld parrallel to the tubing. If you weld perpendicular, its guarenteed to fail due to fatique. He forced the new guy to grind off the welds, and do it properly.

With that in mind, it might be the American "more is better" idea. I admit that I welded that point as well, but I believe the frame is overbuilt anyway.

I don't know which idea is correct. Keep kicked up water out of the joint, or prevent the fatigue failure.

[Aussie Nomad]

Paul, I thought the same thing the other day when I saw Hekki's spring mount.

I was always told not to weld across a member only to weld along it.



Using the picture as an example I would only weld it top and bottom. If it needed more strength I would drill a hole in the center and "rosette" weld it.

Maybe we have been taught to build to suit our conditions. These people might have the luxury of having roads to drive on.

Ian.

[PaulC]

I dunno Paul...maybe cuz over here, it's a normal position weld, and where you are in the Southern Hemisphere....it would be an overhead weld...trickier to do... Doug

I'm with you on this one Miriam
But I guess we should'nt expect anything less than that from Doug
Cheers
Paul

[apratt]

Paul, I thought the same thing the other day when I saw Hekki's spring mount.

I was always told not to weld across a member only to weld along it.



Using the picture as an example I would only weld it top and bottom. If it needed more strength I would drill a hole in the center and "rosette" weld it.

Maybe we have been taught to build to suit our conditions. These people might have the luxury of having roads to drive on.

Ian.

I agree with you Ian. It was the same with me doing body and fender repair work, when we would splice 1/4 panels or other sheet panels we where told not to weld a straight line. The best weld was from plug weld (or spot weld. Or as you call it rosette weld.) If you weld a solid straight line the metal next to the weld line would become brittle and weak, therefore under stress it would crack.

[Classic Finn]

A comment on the welds there is that many of the utility trailer companies here weld the exact same way..and they provide a very good guarantee on all workmanship. So I guess the methods vary quite a bit..from country to country.

And it has been approved by the Finnish Safety Inspectors..

so wether its the right way or the wrong way I cant say but if its safe and wont break or fall apart Im happy...

In my opinion the entire bracket is in the wrong place and it doesnt look too good....Am I bein Finnicky?

Classic Finn

[kirtsjc]

I dunno Paul...maybe cuz over here, it's a normal position weld, and where you are in the Southern Hemisphere....it would be an overhead weld...trickier to do... Doug

Doug, Doug, Doug......

I am ROTFLMAO , and can't think of a thing to say... Except Thank Heavens you are NOT in the Diplomatic Corps for the U.S.A.!!!!

[Spardo]

Hi All, I've noticed that a lot of the trailers over there have the draw bar welded at the front of the chassis meeting point. Over here we do not weld that particular joint so as to minimise drawbar failure. Do any of the engineering gurus (Andrew) have a way to explain to me why there would be this difference. Maybe this pic of Woodbutcher's new frame will help:
Cheers

Your misgivings about welding are well founded Paul, check this thread out:

viewtopic.php?f=28&t=31339&p=1014916#p1014916

[Bogo]

Almost all metals are weakened by the heat generated during welding. Some are weakened allot more than others.

Instead of welding, pass the tongue channel under the front cross member, and use a fitting to allow the two to be bolted together with the bolts only passing through the middle of the webs. Don't bolt through the top or bottom surface as that will weaken the tensile or compression strength which is what is needed to support the bending loads. An engineer could explain it better. I just know more than enough to get myself into allot of trouble.

[angib]

I believe the official Australian advice is not to weld or bolt that joint at all - just let them touch. It doesn't seem 'right' (and doesn't it 'clang' open and shut?) but then the Aussies appear to have more experience of what it takes to stop a trailer tongue fracturing so I'm not going to say it's wrong.

One nice idea is to put a strap or U-bolt under the tongue so it is held in place but with neither welds or bolt holes to weaken it. (Which I see is exactly what Bogo has just written on another thread!)