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It is not uncommon to find old crawler tractors or other old construction machinery with cracks in the truck frame and other structural areas.   While the cracks can be an indication of hard use or long use, they need not detract from the value or usability  of the machine if they are properly repaired.  

Background:  Andy has been working on repairing  mining equipment all of his life. He has graciously shared some of his expertise  in fixing these types of cracks. 

TIP:

Very often when inspecting a machine for repairs, cracks are detected in the frame. When evaluating a crack for repair, several steps must take place. First remove all possibility of sudden movement from the machine. This usually involves removing the ground circuit from the battery. Lockout and tagout of the machine will guard against this. The next step is to remove all pressure from the hydraulic circuits by rotating or actuating the controls back and forth. Once you are assured of a safe work area, then proceed to prepare for the weld repair.

Proper grounding of the welder is a must. Grind clean an area next to the failure to attach the ground clamp. After this step, prepare your air arc torch. Most weld machines are equipped to have some high arc capability. If yours does not, then get ready for a long arduous grinding job. When arcing out a crack, pay attention to the depth of the crack so you don't end up with an extremely wide root opening. After the crack is prepared from air arc, next get your grinder out and start polishing and cleaning of the opening. The acceptable amount of carbon to be left is simply zero. ( substitute wire brushing to get rid of the last of the carbon) The next step is preheating prior to welding. Most preheats call for a minimum of 250 deg. Fahrenheit. After preheat, then setup to begin welding. You need to pay attention to what choice of electrode before starting the repair. Start your root pass on one end then skip to the other in order to secure the two pieces. Now go back and clean the slag off before starting to lay down the multiple passes. A measured amount of root opening isn't always possible, but try keep it at a reasonable amount of 1/8 inch. After welding is complete, grind clean and pay attention to filling undercut. Post heat is a much neglected task. Post heat can become the small extra that allows a repair to survive. Purchase a small amount of fire blanket before beginning your repair. Wrap the affected area with several layers of fire blanket to allow for controlled cool down. Finally, repaint the area to let it blend in with the rest of the appearance.

Several recommendations on tools: an air chipping gun with needles- An air or electric grinder- a victor torch and bottle cart- a capable electric welder such as a Lincoln- Hobart or Miller. 

As for vertical, it is just a matter of getting your temp set right. When welding up, it is critical to get "dialed" in. Don't try to carry to much weld. Just stay with straight stringer beads and watch your base metal for overheat. When you weld overhead you are essentially duplicating what you do when you work flat. I know this might sound simplistic, but it really isn't hard. Most of the prep is tough, but not the welding. most of the time a guy wants to bite off a big job and take shortcuts.  

This means with a 1/8 rod you can weave 1/8 + 1/16, or 3/16. This isn't what I am referring to with the term stringer. Stringer simply means no weave. 

Email:  <grannyjo@northlink.com>

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