Frame Repair Straightening

Important: Frame straightening is complicated and requires special equipment. Only trained technicians should attempt to straighten the frame.

Perform a complete analysis of the condition before completing any steps to straighten the frame. Analyzing the cause of failure helps determine the correct sequence of steps in the repair. Use corrective procedures in order to reverse the flow of the damaging forces. In many instances, pressure must be applied from different directions at the same time.

Important: Do not heat beyond 606°C (1,200°F). A red glow indicates that the material is overheated. Overheating will result in the following conditions:

Careful use of controlled heat is critical. The following items are major sources of trouble:

Heat the area that is stretched as the frame is straightened.

Heat the area after sufficient pressure is exerted in order to cause a slight checking or silvery cracks to appear on the surface of the metal.

Gradually increase the pressure while heating.

Frame Repair Cracks

Straight cracks (1) normally start from the edge of a flange. The crack travels across the flange and through the web section of a rail. The crack continues through the other flange. Straight cracks result from high concentration of stress in small areas of the frame, excessive bending movement, and torsional loading.

Sunburst cracks (2) radiate from a hole in the web section of a rail or crossmember. Sunburst cracks are caused by high loads at a mounting bracket or a crossmember that is not securely attached to the rail.

If cracks occur to both the rail and reinforcement at a particular area of the frame, the cracks must be repaired separately. The flanges must react independently in order to prevent localized stress concentration. Use a copper spacer between the flanges of cracked base rail flanges and reinforcement flanges.

Crossmember mounting flange cracks may be repaired in the same manner as side rail cracks. However, weld bead should be built up in order to provide a smooth radius. Replace a crossmember that is badly damaged.

Important: Aligning the frame and leveling the rails may be necessary before you repair the frame.

1. Remove any equipment that will interfere with access to the crack.
2. Locate the extreme end of the crack and drill a 6 mm (0.25 in) hole.
3. V grind the entire length of the crack from the starting point to the 6 mm (0.25 in) at the extreme end.
4. The bottom of the crack should be opened up 2  (1/16 in) in order to allow good penetration of the weld. Use a hacksaw blade.
5. Weld with the proper electrode and welding techniques.
6. Grind the weld smooth on the inside and the outside of the rail or crossmember. Be extremely careful to eliminate weld buildup or notches on the edge of the flange.