How to fix Stress Cracks??

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1973Guppie

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Hi all,

I am wondering if somebody can tell me the proper way to fix stress cracks? I have these in a few places on my 55 resto I am doing, namely they are in the corners of the door jambs. These are just little cracks that go from corner to corner in the corner of the door jambs. The main one is on the drivers side, makes sense as that would be the door to be used the most.

I am wondering of the proper way to fix these? my first thought was to simply ground out a small groove in the crack itself and just weld it up, grind flush and be done with it? Although I have a friend that told me another option, but can't remember exactly what it was? I think he mentioned that you should place a small strip of metal perpendicular to the stress crack in order to keep the crack from coming back? That would make sense since it would keep the metal there from splitting again as it will have some support perpendicular to the crack.

any help appreciated, if you have no idea what I am talking about I can take some pics......

Noah
 
Pics would help....

relieving the stress of the crack is important when welding up cast iron and I suspect it might be true for your application. Essentially you will want to relieve the crack at both ends, a fine drill will work fine. Relieve the crack before laying a bead and grinding it flush.
 
It is called stop drilling.

You drill a hole into the material that is cracked, at the end of the crack, and then weld the crack closed.
 
drill

Yes, it is called stop drilling and we do it all the time on aircraft to keep cracks from growing-- of course they use sheet metal patches not welding up. You may not be able to see where the crack ends with the naked eye ---we use NDI to determine the actual end of the crack


With welding you may be all right anyway if you just welded a little beyond the visible crack a little ---The idea is you don't want to run a bead and then have a non visible crack remaining beyond the weld --a new crack will start growing from there---Make sense?

This could run off at an angle from the end of the crack you can see so stop drilling usually will make sure you get it all so it cant hurt either but I don't think it is all that critical for what you are doing

if it cracked because the surrounding support is weakened you may need to actually cut out and replace the bad area to keep it from coming back. But a door? Probably cause of hanging on the doors etc over time?

got a pic?
ED: looks like me and Poser were posting at the same time-But he said it all in a sentence! ha ha! got to work on that!
 
steve is like yoda....

here are some pics, so I will basically just drill a small hole at each end of the crack and weld the crack up then, they are small cracks really, I don't think I need to redo the whole area or anything, just want to do it right while I have it on the rottisserie, after this metalwork is done and I can get it back on the frame and start prepping panels to be put back on!

:)
stress cracks 001.webp
stress cracks 002.webp
stress cracks 003.webp
 
cracks

I would say you could try the welding alone but not dress the welds up too much and make them too thin and you may be fine I mean this is a non critical car repair but here's some other options


Could be the cracks formed due to stress corrosion. you could have some minor pitting under there and you also have a point of concentrated stress along the ridge which is there to add strength. The cracks start and connect the dots along the pitting and propagate out from there

My guess is the cracks that run perpendicular came because the main crack weakened the area and then flexing caused them. Welding out 90 degrees along these cracks might create a point to fail later at the intersection of the welds--- Might not be a big prob once the first crack is fixed . Also, if the weld is hard and you get some flex there it may crack across the main crack weld from side to side especially in the curve

you could cut it out including those side cracks and weld in a patch or go over it with a doubler after welding it up to add strength or both

On the second one it runs into that lap joint so ideally you could remove the rivets and cut it out and replace that end section. a weld so close to the lap might crack again along the weld edge

By moving the welds away from the stress you could also dress them up more for cosmetic purposes

Having said that---The worst case seems to be that it does not last as long as you would like so I guess that would be the choice between zipping it up or patching or doubling depending on how you feel about that


I dont want to give the impresion that I know for sure that just zipping it up would fail cause I dont. I am just pointing out what you might expect--maybe

:cheers:
 
if you can(both pics are going to be covered by headliner) lay and shape a piece of 18ga to the area and rosette weld it in. trying to weld up those cracks by themselves will only result in them cracking on either side of the new weld.
 
Okay, so like this Brett? the spots are going to be spot welds. I think I could spot weld the plate on the higher areas and shape the metal down into the lower areas with a body hammer. I could see how a plate like this would not allow flex. Would it also be reccomended that I weld up the crack before placing the plate on there?
stress cracks 002 mod.webp
stress cracks 003 mod.webp
 
weld up the cracks

Yup, weld em up

That looks pretty good and the rosette welds are a nice touch:) that looks like a permanent repair now;)

form it as close as you can
after you cut it smooth the edges (break all edges) if you are not welding all around
round the corners slightly instead of leaving them sharp

Follow around a little out from the welded crack with the rosette welds to reinforce along the crack and then tack the edges down or you could make it a little wider and do some offset rosettes further out. Staggering the welds seems like a good idea.

if you stop drill you could put some metal foil tape down over them and coat with POR and you could also use weldable primer between the doubler and the skin

I still dont like the side cracks but that may be overkill to cut them out and patch in

hey I found this for ya-its actually a frame repair but it is the same repair procedure wise ---- they recommend stop drill even with welding

Google Image Result for http://www.tech-cor.net/AutoResBulletin/2000-6/Images/fordfig6.gif


The frame reinforcement procedure described in the service manual calls for installing the reinforcement on the outside of the rail (see Figure 6). There is no reference to installing the reinforcement on the inside. The first step is to drill a 6 mm (1/4") hole at a point 12 mm (1/2") beyond the root of the crack. This is to stop the crack from spreading. You then grind out the full length of the crack from the backside to form a V-shaped slot, and weld the crack shut. Clearance holes are drilled in the reinforcement, where necessary to clear rivets and bolts. The reinforcement is clamped to the rail and welded to the rail all around its perimeter. Undercoating applied to the outside of the repair provides the necessary corrosion protection.
stress cracks 002 mod2.webp
 
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good info, thanks,

what do you mean by "break all edges"? I think I will drill some smaller holes around the outer edges for the spot welds and some larger bigger holes in the middle.

I am starting to see how this will keep everything from ever moving like this again......
 
in addition to the "stop drilling" you might want to try and source the cause of the stress in that particular area and try to reverse/restructure it so that it doesn't seek out the next closest weak spot. I'm sure you've seen the early 40 series doors by the wing windows;).
 
honestly I think the stress is from the door being slammed there, so natural really in it's occurence, I might be wrong but? I think for now I will just plate it and be done with it. Yes, I know the 40's by the wing windows, I have a 40 and it has cracks there.....
 
the 55 in my garage has plenty of cracks like that. I assumed it was just from the body twisting and flexing over the years. I have always felt the metal in my 55s felt kind of "brittle" and won't personaly spend a whole lot of time trying to fix these, as I expect to see them again (or have the rest of the roof desolve around them). I intend only to drill and weld the cracks, and rely on the cage I build to stiffen things up and delay further cracking. I am not doing a resto however, and it looks like it would be a lot easier to deal with if I took the roof off...
yeah right when that comes off it's not going back on.
 

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