Welding a Chassis

[16svt]

In a few places, the chassis on my AEC O854 Coles Crane is heavily rusted/wasted. I have decided that as there are not too many spare chassis about, my only real option is to build the wasted areas up with weld. I am not too worried about this as the Crane has a massive sub frame and there is not too much stress on the chassis where I am welding it. What are the 'forums' views on this? also what are peoples thought on cutting bit out of the chassis and welding replacement sections in. This is not something I intend to do, i just want to know peoples views.

Cheers Dan

[Zero-Five-Two]

It does not seem to be practised so much these days, but back "then" cutting and welding a chassis to extend/shorten a wagon was common place. Many old trucks undergoing restoration get chassis work done now to return them to original spec.

 

So long as the quality of the welding being done is good then no problem.

[N.O.S.]

I believe the general rule if stick welding is to use low hydrogen electrodes.

[ruggyjohn]

In a few places, the chassis on my AEC O854 Coles Crane is heavily rusted/wasted. I have decided that as there are not too many spare chassis about, my only real option is to build the wasted areas up with weld. I am not too worried about this as the Crane has a massive sub frame and there is not too much stress on the chassis where I am welding it. What are the 'forums' views on this? also what are peoples thought on cutting bit out of the chassis and welding replacement sections in. This is not something I intend to do, i just want to know peoples views.

Cheers Dan

 

best welded with mig as the chassis is not mild steel hence the advice if stick welding to use low hydrogen rods, if joining two sections then a decent fillet needs to be ground out and a plate bolted on the inside covering the join, some say the chassis should be cut at 45 degrees to make the join stronger, as for filling deep pits weld them up and grind of, try not to put too much heat in to any specific area so as to reduce the chance of distorting the chassis, if the pit is deep fill the bottom and move on to another and then come back to it when its cooled a little.

[16svt]

best welded with mig as the chassis is not mild steel hence the advice if stick welding to use low hydrogen rods, if joining two sections then a decent fillet needs to be ground out and a plate bolted on the inside covering the join, some say the chassis should be cut at 45 degrees to make the join stronger, as for filling deep pits weld them up and grind of, try not to put too much heat in to any specific area so as to reduce the chance of distorting the chassis, if the pit is deep fill the bottom and move on to another and then come back to it when its cooled a little.

Thanks for that advice, that was exactly what I was looking for. Its not too far off what i had been doing already.

[Tamber]

Welding a chassis -- both when shortening/lengthening a truck, and as a repair -- is still fairly common these days; and the body-builder's manuals (if you can ever find them! Probably not, for the older stuff.) will generally contain a section somewhere concerning procedures for doing so. Usually right after telling you not to do it.

 

But the general summary of the procedures, as ruggyjohn hit right on the head, is:

 

 

• low-hydrogen rods, if you're using stick
  
• Make sure both sides of the join are cleaned back to bare metal with no crud, paint, or rust.
  
• Bevel the edges that you're welding, to ensure full penetration welds
  
• 45° cuts for splices, if possible
  
• Try to reduce the amount of heat you put into the chassis -- it not only creates the risk of distortion but might affect the strength of the steel, since truck chassis' are usually an alloy steel, or heat-treated
  
• Dress the welds of splices flat with the parent metal and add fish-plates (ideally bolted) on both inside and outside (if it's C-section, but I've not seen many truck chassis' that aren't. ) that extend a minimum of 8 inches either side of the joint.
  

 

 

We've never had a truck break in two after following the above. (I'm sure I've jinxed it now. :blush:)