welding

[rexie1100]

Howdy all,

I'm sure someone on here knows the answer to this.

I've read/heard (cant remember where) that you should only weld lengh ways on the draw bar not accross.

My mate who is a welder welded mine both ways, he said it will be better, is this going to be an issue?

cheers and  in advance

[Jon]

depends on a few things such as hitch download weight, drawbar section and wall thickness.
Lots of people do it. If you can avoid it then great.

[Tjupurula]

Hi Rexie
The only reason the it is not recommended to weld across is because of possible metal fatigue.  That however is no longer relevant, as long as the welding is being done with a MIG.  Can you please indicate as to precisely why the weld was necessary, or was it simply initial construction ?  I have welded both lenthways and across on a variety of drawbars, and there has never been a problem.
Regards
Tjupurula

[sandman]

That however is no longer relevant, as long as the welding is being done with a MIG

Sorry to be off topic but what makes you say that? There is no difference between the heat required for a good weld with MIG or Stick and the HAZ is the same.

[Tjupurula]

Sorry to be off topic but what makes you say that? There is no difference between the heat required for a good weld with MIG or Stick and the HAZ is the same.

Hi Sandman
MIG welds are,if done correctly, considerably stronger than stick welds.  The HAZ is also considerably different between the two, which is why the majority of fabricators these days do use MIG.  I am assuming the OP is referring to domestic welding, as opposed to industrial.
Regards
Tjupurula

[Symon]

Hi Sandman
MIG welds are,if done correctly, considerably stronger than stick welds.  The HAZ is also considerably different between the two, which is why the majority of fabricators these days do use MIG.  I am assuming the OP is referring to domestic welding, as opposed to industrial.
Regards
Tjupurula

Not saying you are wrong, but when our boilermakers patch up dragline and excavator buckets and the like they always use stick welders for the extra penetration, never MIG's.

[Tjupurula]

Not saying you are wrong, but when our boilermakers patch up dragline and excavator buckets and the like they always use stick welders for the extra penetration, never MIG's.

Hi Symon
As I mentioned, industrial welding is considerably different to light domestic welding.  When I do any RSJ work or the like, I also use a heavy stick, preferably low hydrogen sticks.  For the light work that the OP was discussing, I would never use a stick.
Regards
Tjupurula

[qlddsl]

Not saying you are wrong, but when our boilermakers patch up dragline and excavator buckets and the like they always use stick welders for the extra penetration, never MIG's.

Stick welders can tolerate a lot more metal contamination aswell

[camperd4d]

Hi Sandman
MIG welds are,if done correctly, considerably stronger than stick welds.  The HAZ is also considerably different between the two, which is why the majority of fabricators these days do use MIG.  I am assuming the OP is referring to domestic welding, as opposed to industrial.
Regards
Tjupurula

really?? please do tell.Ive worked in some pretty big fab shops welded a fair bit of steel, mig and stick ,preparation,amp set up,correct rods,skill level will see the similar  results.
Migs are faster/esiser for the average welder but can be subjected to more imperfections if the welding envioroment( gas sheild) is not well protected.
why would my home 200 amp stick welder using satincraft rods be any different to running my work 200 amp stick welder same rods?? Amps are Amps

[jim-m-72]

Back to welding across the top of the draw bar shouldnt be done as it creates a stress point and will eventualy cause it to crack, possibly at the worst time (Murphy,s law) only time will tell now. ps doesnt matter if its a mig, tig, stick or sub arc amps are amps and create heat along with stress from the heat and metal contracting after welding
Jim

[cardinal28]

Hi All
Well I am certainly no expert, but being a boillie by trade I think I can make a few comments. Both stick and mig have their advantages and disadvantages. Mig is simple to use, BUT it can be a huge problem with oily, dirty, painted or galvanised surfaces wich can leave a lot of porosity in the weld leading to a very understreangth join. Also wind can be a problem with gas shielded mig welding leaving the same result. Personally stick welding gives a very satisifing result if used succesufully. Once again all the problems associated for mig can also affect stick welding. At the end of the day good preperation of the welded surfaces will lead to a good welding process.
As a note on high strength welding it is not recommended to weld across beams etc, only lengthways. But in saying that we are talking high strength as in most major construction. It should also be noted that most states have outlawed home made bullbars and towbars and all other modifications have to have to be engineered and have engineer sign off. Beware the back yard fabricator if anything happens.
Hope this helps.

[dazzler]

I was told this years ago with one of my trailer builds and have taken that advice (not across the drawbar) ever since.

I do wonder though if there is any evidence of failure anywhere or is it an urban myth?  A photo would be good.

I think correct design is more important than where its welded.  You would think that leverage and using the drawbar to carry stuff would do more damage.

[MrHorsepower]

I have known about the "no welding across the drawbar" thing for years and on the 5+ trailers that I have built have never done so. However I have lookaed at the 3 scissor lift trailers at work (carrying 1800kg scissor lifts) and 2 of the 3 have a weld across the draw bar where the main platform attaches. These trailers were all built proffesionally by a company specialising in plant trailers. Knowing this I still probably couldn't bring myself to lay a bead of weld horizontally across a drawbar .......superstition I guess...Cheers..Michael.

[prodigyrf]

MIG is largely used in enclosed workshops due to wind blowing away the shielding gas and it aint much fun dragging around in the dirt a heavy MIG welder complete with its substantial roll of MIG wire and a heavy cylinder of gas. Gas shielded MIGs are faster and more economical for any production welding, particularly because you don't have to chip off and wire brush flux slag. To overcome that handicap you can use a portable MIG with flux cored wire and largely for light gauge sheetmetal welding where stick welding has its lower limits unless you're a real pro and there's no MIG handy. Flux cored MIG presents the same cleanup problem as rods but you can now see why maintenance welders use rods outside in the open, particularly on big stuff.

There is no difference(or there shouldn't be) in strength of weld between MIG or rod providing the right filler steel is used for the base steel and welders can pressure vessel weld with either as the case may be. Essentially pressure vessel welding must contain no slag inclusions or undercut and is often x-rayed for that reason. Now we come to exactly what the base metal is you're welding and you need to be aware that many steels are high tensile nowadays, as well as problematic cast irons which must be specially stress relieved or they will crack at the weld completely and suddenly. With plain steel, welding anywhere should not affect performance but it is true hi-tensile steels can present problems. For example truck chassis with DO NOT WELD plastered on their bolted and rivetted channels and they mean it or else. Then you come down to much lesser tensile steels like Duragal tubing which are designed to be easily welded(as distinct from heavy galv) but probably not all around in a tensile situation like a drawbar but may be fine in compression (ie a bolted cap plate) It's quite OK to weld say a cross brace across a rectangular Duragal drawbar but not all around its circumference as its probably been engineered for its particular structural properties. In that regard you'd make the brace the same size tube so that it is welded to the corners of the adjoining tube. Mild steel drawbar (which it definitely will be if hot dipped galvanised) and the welding should have no effect anywhere provide it's sound welding and no undercut for the obvious.

[danielhobby]

well fellas here we go,it is a no goer to weld across the top of a drawbar/trailer box connection because the weld bead/heat cause a change in composition of parent metal(rhs)EXACTLY where the rhs andweld toe meet.This point also becomes the fulcrum(perhaps for want of a better term)when the trailer is loaded out of perfect balance and is worked continually up and down until a failure becomes a distinct possability and when it does if it does the fail is in the rhs at the mentioned point

[danielhobby]

and mig or stick or tig makes not a bit of difference when a wall thicknes of 3 or 4 mm is concerned.now im going to cover my head with my hands and wait for the stones to stop!!!