Suggestions on Frame Repair

I noticed this crack in my frame just as we were about to head out on a run a the TDS event this weekend. We made a temporary repair with some scrap metal using my friend's on-board welder and it held for the day of wheeling. The crack is all the way through the bottom part of the 'C' and stops almost at the top.

Now I need a more permanent fix for it. Recommendations appreciated. It looks like a previous owner plated or somehow added an extension to this frame in front of where it cracked. The front line is a shadow from the offset steel previously added, not an additional crack. Thanks.

 

If possible, I'd remove the plate that the PO put on, grind and weld the crack, then add a new plate that bridges the cracked area. If possible, box the inside of the frame there. I had a similar crack at the rear spring hanger that I welded and added a plate on the outside and it eventually cracked through the plate again. Those cracks usually originate on the inner bottom lip of the frame and travel up. That's why boxing works so well as it strengthens that edge. Plan on the other side cracking eventually, if it isn't already. Anywhere a re-inforcing plate ends is a candidate for a new crack to form. With that in mind try to plan the best place to end your plate. Don't weld closer than 1/4" from the end of the plate. Good luck.

 

mike heres mine, had a similar crack. cracked just after inside boxing stopped, now fully boxed , take off other bandaid,just grind out crack, weld with good heat , grind and replate plate, end repair on an angle or fish mouth , my repair metal is 3/16, don't go to thick that will just ask for another one . if boxing try to run it as long as you can and end on an angle . a structral engineer for Lusardi came up with the shape or my repair and rotisary welds . I have really cranked on mine and it has held up so far .

 

Here is how we do that type of repair at work. Clean all the metal one inch back from both sides (right and left) of the crack. Clean front and back sides of the frame if you can. Grind a "V" down the middle of the crack. Do a root weld down the crack with 6010. Next do one or two cover passes with 7018. Make a "fish plate" out of 1/8" thick steel plate. The plate should be diamond shaped. It should be wider than it is taller. The height of the top and bottom points should be the same as your frame height. Place the plate over the welded crack and mark around the sides of the plate (where you will weld). Clean the metal around where you will be welding. Weld the plate over the crack with a 6010 root pass and 7018 cover pass. If you can get to the back side of your frame, put a fish plate over the crack on that side as well. If you use a rectangular plate instead of a diamond shaped plate, don't weld the sides, just the top and bottom. Your frame flexes up and down, this causes the cracks. If you have a vertical weld on the side of your frame it may crack next to the weld (like what already happened to your frame). Hope that doesn't confuse you too much :?

 

Can you say overkill ! I do say that is a beautiful fix though, nice!

Unless you are running 35" tires, a smallblock and a ton of frame flex I think both are over kill. Find the end of the crack dreill a hole to stop the crack and plate it with a diamond shape patch panel of the same thickness as the frame and you should be good to go. i dont see the need for the multiple passes on this material.

So how was TDS? I wish the funds were avail this year to go. I havent been out there in 4 years, very fun place.

 

Good, clear directions. Thanks guys! I don't know if you can tell by the picture, but the metal is pretty darn thin. I think 1/8" plate will be the ticket. I'll also try to find a piece that covers the bottom part of the frame. I haven't looked to see how much I'll be able to box on the inside yet, but I'll do what I can.
It won't be pretty, but at least it will match the rest of the Jeep.

 

Can you say overkill -spoolnaround
not really -, you have not seen me wheel.
I have been chasing that crack for years , and finally it is gone!!!! it was worth the work just for peace of mind.

 

The point dvw86 makes about the diamond shape is very important with load transfer into and out of a splice. A similar taper is seen with cj5/442's repair. cj5/442 did a good job tapering both ends of his splice. I don't think it's overkill. I've seen many short frame splices that crack again right next to the splice. I'd strongly recommend that a rectangular splice be avoided. If a second splice is going to be used on the inside of the frame, it should not have the same profile as the external splice. It should stop and start at least 1.0" inch ahead of, or behind the opposite side splice. This dissimilarity keeps a hard point in the main frame from occurring, and reducing the chance for another crack location.

 

Yes. As I understand it, the problem in this case is with rigidity. A short splice makes that short section of the frame very rigid. This causes what's called a "stress riser." The stress rises at the point where the flexible un-patched frame meets the more rigid patched frame. Concentrated stress makes the steel more likely to fatigue at the stress riser. The diamond or fish-mouth shape eases this transition.

Also realize that the rails of the frame (horizontal parts) provide most of the weight-carrying strength of the frame. The web (vertical part) between the rails mostly serves to keep the rails in parallel with each other. Welding perpendicular to the length of the frame, especially across the rails, should be avoided (according to my half-a exposure to this stuff in the race car shop and understanding of the mechanics, not a lot of welding experience).

 

Here's a pic of the welded crack. The existing plate that was about an inch in front of the crack runs all the way to the front end of the frame. I'm not taking it off. Instead I cut a triangle piece out of it to get rid of the vertical joint as shown.


So now to add the new plate. The cardboard shows what I'm planning. The rectangular tab part on the bottom will actually be part of the 1/8" square tube that I'm cutting the plate out of , welded to the bottom.
FYI the inside of the frame is boxed to a bit past the leaf spring mount and was not cracked.

Comments? Recommendations?

 

Looks good. But I'm just an amateur!

 

You're definitely on the right track. It might be better to extend the repair plate farther aft (down) a couple inches. Make sure there's good weld penetration at the forward most joint. This is where the existing doubler meets the suggested repair plate.

Without seeing the rest of the frame and what else is fastened to it, it's tough to make a complete evaluation. Keep in mind that you should inspect this repair at normal intervals. The plate suggested is on the short side, and having it butted next to an existing doubler isn't the best arrangement. That doubler should have extended all the way down to the spring hangar.

BTW, are those spring hangers working OK? I'd suggest a much heavier gusset on the forward and aft ends between the horizontal surface of the hanger and frame web.

 

I can lengthen the plate some. What would be a good terminus location, half way between the motor mount and the spring hanger? Should I not butt weld the new plate to the old doulbler? Not sure what else I could do there.

The hangers seem to be holding up okay. The plate under the gussets extends to the inside of the frame rail, but you're right, more bracing would be better.

Thanks.

 

Your repair plate is actually becoming an extension of the existing doubler. That's why I emphasize having a good weld between the two members. The load (stress) in the doulber needs to pass through the repair plate and back into the frame in a smooth manner, and away from the crack. This is why I suggest a longer plate.

The half way point you suggest is fine; just remember that you should inspect the area occasionally after everything is in service.