Frame repair

[Mega Arc 5040DD]

Where I work we use Qt-100 alot for for trailer frames not sure why it's just what the engineers decided to design with I guess. We also bend up Qt-100 rails for the truck shop my boss owns for when they do the odd frame stretch. It's a pain in the *** to bend.

[welder_one]

hmmmm.... still trying to pawn off the qt100 steel? too hard for frame work, when 572 gr-50 would be better choice... especially if you gotta try to bend it... hmmmm.... i used to have a supervisor named steve.... we called him stoopid steve.... that aint you is it?

[st333v]

is there any wrong way? I will be repairing 2 2 inch holes in a tube frame. the holes are on the vertical surface. I will be mig welding and repairing with either 3/16 or 1/4 flat stock and putting a 90 bend on the bottom of the plate to wrap around the frame.

frame holes are neccasary, they prevent crack from making the frame less rigid. if the frame rail runs up high, maybe think about qt-100 plate(1/4") wrap around bottom from plate bent on break press, throw in a few holes for some give, or i guess diamonds that are rounded are the big thing now from engineers lately. stitch it up.

[scote]

Always weld horizontal on a frame repair. Weld the top and bottom of your overlapping plate and make it big enough to put bolts through on both ends of the plate. If your frame has holes already make your plate large enough to use those. If not make your own.

[jolane]

I would also suggest treating the rust if you are going to cover it up. There are products out like POR-15, Naval Jelly, etc... that you could put on first IF they are away from welding. Maybe this way the rust will slow down, or even stop completely.
What I have done on my car "chassis" (unibody actually, but still rusty) is use a sanding disc to get to bar metal first, then put a patch over. I would say that regardless of what you do, butt weld or not, that you should still put a doubler plate over the affected area, if possible. You may want to even box the frame if it is not boxed already. That will definitely make it stronger and stiffer.
Joshua

[Bulldog]

As far as cutting out the rusted piece It would depend on how badly the thing is rusted. If the frame has any structural integredy to it at all I think I would cover the bad section and if the frame is totally shot cut it out and put a piece in then fish plate over that.
Bulldog

[df5152]

thanks for the info the diagnal makes sence. I have a nice big chipping hammer i planned on using and was also going to drill the holes in the plate. Ill try to take some pictures.

Is there any pluses or minuses to cutting the rust out and doing a butt weld as compared to laying the plate over the top and lap welding it?

[jolane]

I have also been told NOT to weld completely across a frame rail, as in if a frame cracks vertically (similar to a mid-80's Chevy Truck frame at the steering box mount), skip weld the patch. The HAZ area will cause a weakness, and with a continuous weld, will crack across the frame. I have noticed that people tend to make the welded edges go diagonal "down" the frame, to also help spread the loads and HAZ area.
On dove tail trailers, I have seen reinforcement doubler plates added at the dove tail bend. The reinforcement plates were a diamond shape, so the HAZ was not vertical across the load bearing member.
I don't know if this makes sense or even helps at all. Hopefully it does.
Joshua

[Bulldog]

Clean up as much of the rusty area as possible. Make the repair patch 4X as big as the bad area. Also drill some holes in the (good) steel where the patch is and plug weld from the frame to the patch. While your down there check out the rest of the frame closely. Use the pointed end of a chipping hammer on any and all rust spots you'll probably find more holes. Good luck and be safe!
Bulldog

[df5152]

is there any wrong way? I will be repairing 2 2 inch holes in a tube frame. the holes are on the vertical surface. I will be mig welding and repairing with either 3/16 or 1/4 flat stock and putting a 90 bend on the bottom of the plate to wrap around the frame.