Hareline crack in frame....

I think it is only the top and bottom flange you aren't supposed to weld. I think you would be surprised how many welded frames are on the road. Done properly it shouldn't be an issue as no one would be able to tell it's welded.

 

you can weld and drill a frame all you want. there isn't anything illegal about it. just do it right.

 

First thing , put the driver on a diet.

If done correctly a frame can be welded.
How do you think they extend chassis.
The problem with a crack is , that the crack is there because the frame has been highly stressed or fatigued.
It will be stressed and fatuigue there after welding as well.
The actual material will dictate the type of electrode.
Normally just low hydrogen high ductile electrode.
Preheat the frame and keep some heat on weld afterwards for a couple of hours for a slow cool off.
Grind the ends and sides of the weld bead to eliminate the migration of micro cracks (toe grinding).
If you can get someone with some high frequency stress relieving equipment it wont hurt to stress relieve.
Plate it with some chassis bolts or rivets if you are not concerned with what it looks like.

 

You can't weld or drill the top and bottom flange. The sides are fair game and if you plate it on on either the inside or outside you can weld on the flanges.
How do you think they lengthen frames. The regs have better details about this under vehicle section

 

I have welded lots of frames, I use an air arc to follow the crack to the end, drilling sounds good but the crack can be longer on the inside. with the air arc you can see the crack. I keep the frame as cool as posible, with 7018, clamp backing plates to work as a heat sink and do it from the bottom up about 3 inches at a time, spray with water to cool it off. I use a stick welder all the time MiG puts out to much heat.
I use an air chisel to clean it and getting the heat right is very important.
If you put any amount of heat in it, you will harden it and it will really crack.
I have never had a frame weld fail, did many extensions, and repairs.
Leave the grinder alone, you are welding the frame not grinding it away.

 

I'm willin to bet that crack runs through those 2 other bolt holes that are on the hanger. easy weld but would have to remove hanger to do it right.

 

My previous post was advice on welding cracks on a trailer. If you MUST repair a tractor chasis; Find a GOOD heliarc guy. Aircraft experience prefered. And still I would advise replacing that frame rail at earliest.

 

The reason you grind away the edges of the weld bead are because this is where cracks come from.
There are always micro cracks where the weld bead meets the parent metal.
These under stress are the seed of structural cracks.
This toe grinding technique is used on critical parts in the perto-chemical , oil well , mining and aerospace industry.

I also think the crack runs under the hanger to the other bolts.

 

Why are you using 7018? It is generally considered filler rod, and designed for last pass / top pass work. I know it looks good when you're done and takes much less of a skill set to operate, but there are definitely better rod choices. Something like 6010 is a much better root pass rod. Is this a heat thing or what? Im not trying to pretend I know how to weld frames, I do not. But, I do know you're not getting near the penetration you may think you are. Is there a good reason Im not understanding?