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I am now getting the chance to add all the goodies to my frame but before I go any further I want to know how should I weld the cracks in my frame? I havent had a problem welding the holes or anything like that but the frame does have cracks where the old shock mounts used to be. I am adding MII so I want a solid frame and need this fixed. Any advise? All the frame shops by me wont even touch the frame as I have already whacked off all the old suspension. Any ideas? thanks
There is a very good method to restore the strength and appearance of the frame. Locate and map the crack(s). Drill a small hole (1/8 dia is good) at each end of the crack thru the web. Grind a shallow (1/2 web thickness) V-shaped groove that follows the crack from hole to hole. Weld the groove and holes full and grind off flush.
This method is very much like the way we repair cracks in airframe components and works very well to resist fatigue cracks again later. Make sure your welds have good penetration. Check from the back side for fall-thru.
I assume that you will be boxing the frame. May I suggest that when you do, you box well past the front spring rear mounts. My 56 has a MII IFS put in by the previous owner. He boxed back to those mounts and both frame rails had cracks where the boxing ended from frame flexing.
Thanks for the info. After some more research from other sites i found that I should grind the cracks first but thats as far as they said. That info was just what I needed and what I was looking for. And yes I will be boxing further than that but still not sure if I want it to be the whole frame. Thanks a ton again.
Randy pretty much covered it-although he didn't point you to a very helpful sketch in his gallery. Take a look at this-the "scalloped cut" vs square cut will help reduce the likelihood of cracks in the future.
Also, avoid welding across (perpendicular) to the frame rails-try to make all of the welds parallel with the frame. I know it can't be totally avoided when welding in the cross member, but when boxing or adding gussets (fish-plates), try to avoid it, especially on the "open end."
Another thing to remember when welding on a fish plate is to leave about 1/4" unwelded at all 4 corners. Otherwise you will just create new stress risers and start new cracks along the weld lines axis.
And yes, when splicing a frame it is always best to use a Z cut to start, this gives the maximum strength.
Hey Fat Fendered Ford, I see you had some holes in your frame from the battery acid. How did you fix these holes? Did you cut out the damaged area and weld in a new piece? Thanks Fred
Is there a conceern about MIG-welding being a very hard metal, compared to the softer frame metal? In other words, is stress relieving necessary? Stick welding isn't as bad, but I've always heard frame repairs should be gas-welded (when filling in cracks, holes, etc)
Ross - MIG rod is a very similar alloy to the frame metal. Neither is technically "hardenable". Stress relieving welded assemblies reduces the stress caused by the molten metal shrinking as it cools. That shrinking does add residual stresses, which are subtractive from the frame's load-carrying capacity.
I've heard different theories about stress-relieving. Some say it is necessary. Some never bother. In the aircraft industry, where welded assemblies are designed for minimum weight for the load capacity, mild steel weldments are rarely done. Aluminum and exotic steel alloys (4130, etc) are almost always done.
The stress relieving process just heats everything up and then cools it down together.
You should have no need to stress relieve frame repairs, unless the welding and heat applied are really extensive and cause the frame to warp out of shape. Besides, if you could find an oven large enough to accept a frame and heat it to cherry red temp, the cost to do it would probably be more than the cost of a new frame. Flame-heating an area to stress relieve it has limited value.
MHO
Randy pretty much covered it-although he didn't point you to a very helpful sketch in his gallery. Take a look at this-the "scalloped cut" vs square cut will help reduce the likelihood of cracks in the future.
Also, avoid welding across (perpendicular) to the frame rails-try to make all of the welds parallel with the frame. I know it can't be totally avoided when welding in the cross member, but when boxing or adding gussets (fish-plates), try to avoid it, especially on the "open end."
Clear as mud?
Good Luck!
i know this is a very old thread...
my question is why not to weld perpendicular to the frame?
I´m really interested in the technical reason
thanks
Ingo
my question is why not to weld perpendicular to the frame?
I´m really interested in the technical reason
thanks
Ingo
The ideal frame rail would have uniform "strength" across its entire length. In that situation bending and twisting forces applied to the rail would cause a consistent and uniform bend or twist in the rail. This uniform bend also means that the stresses on the rail are uniform. With stresses distributed along the length a given total applied force creates the least local stress per unit length. Consider that local stress and local bending are precisely related by the strength of the material.
Now take that uniform frame rail and attach a super stiff plate over some length right in the middle, with an abrupt stopping point at each end. Now if we applied and bending or twisting force the stronger middle bit will not deflect or deform. But, at the junction between the normal and "strong" section of frame some extra local bending will occur, kind of like folding a piece of paper. This extra local bending means we also have extra local stress. We have "concentrated" the stress at the junction between strong and weak sections. These "stress concentrations" mean the material at these junction is more likely to fail by inelastic deformation (permanent bending) or cracking.
The reason for angled junctions, doubler plates and boxing with "fished" ends, and Z joints is to distribute any change in the net structural properties over a sufficient length that the resulting stress concentrations along or a the ends of these structures is small enough to not create high local stress concentrations. Doublers and boxing will add strength while Z joints are more likely weak sections. Either way, we want to distribute the change in strength over a sufficient length so as not create large stress concentrations.
In engineered systems the shape and size of these joints would be designed and modeled with detailed strength of materials data and computer simulations. In our hobby we rely on the decades long experience of multiple artisans and learn by what they have done and their long-term results. The resulting designs have become largely intuitive, but the success rate is admirable.
So if I understand, you want to reinforce some spots but not others. You are going to create weak spots right where your boxing starts and stops. There's reason that aftermarket frames are boxed front to back, that way the frame is the same strength all the way.
