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I have a 1970 Mack truck with a crack in the frame.   the crack is starts on the bottom of the frame travels vert. to the center.  Its in the middle of the rear spring hanger of the front axle.  It is centered between the bolts appox. 2" each way.  It is a single frame 7" web. Doubling will be difficult because the frame is tapered. Not to mention the joy of the trans, fuel tank and the cab.
The pervious suggestions were to slightly perheat, grind out the crack completly, use a termiating hole, weld with a backing plate, and double the frame.
??I'm curious about rod or wire type, affects to tempering of the frame.  what about NR-211 innershied or 11018rod
??how about welding a 15"-5/16 strip of flat stock to the bottom of the frame on the outside??

RE: repair

Adding the straps to the bottom of the frame by welding or bolting will certainly reinforce the existing frame but, I would still weld up the crack as described.  The straps are quite common when frames are completely  broken so it should   work ok.  I still prefer a Fitch plate or comething similar.  Just don't get too much heat in the area.  In some frames embrittlement can become a  problem and that is the reason for the doubler.  It just spreads the load away from the repaired area.


RE: repair

thankyou very much fellows!!  what we end up doing is grinding out the crack and welding it with 11018 rod.  its too much work to put in a terminating hole, because we would have to take half the truck apart.  instead of a strap we put on a 15" X 1/4" piece of angle iron to give it vertical suport, and we tapered the ends to avoid hard spots, and sitch welded it to avoid too much heat.  again thanks a lot. I'll update you in a month or so.

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