Section II. FRAME MEMBERS, MATERIALS, AND ASSEMBLY

TB 9-2510-242-40

Section II. FRAME MEMBERS, MATERIALS, AND ASSEMBLY

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Frame embers. Depending upon load capacities and frame designs, trailer frame structural members consist of

pressed steel channel or box beam side rails, pressed steel channel , or box beam cross members, and steel gusset

plates and stiffeners. Chassis structural members consist of longitudinal rails, crossmembers, gusset plates, stiffeners,

and plates associated with the kingpin and upper coupler plate. Longitudinal rails can be pressed steel channels, I-

beams, or box beams. Crossmembers may be pressed steel channel, Z-section, I-beam or box beams. The corners of

some SEMITRAILERS and some brackets are steel castings. In some semitrailer tankers, the tanker barrel is a

structural member and carries load. In some van SEMITRAILERS, the van body carries load.

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Frame Materials. Steel composition of frame members, gussets, and stiffeners vary depending upon design

limitations such as load capacities, trailer size, assembly techniques, and weight saving requirements. Consequently, the

steels used range from hot or cold rolled, low carbon, structural quality types having yield strengths of 30,000 to 36,000

PSI, through the high strength low alloys having yield strengths of 45,000 to 55,000 PSI; the latter offer a weight savings

up to 25 percent. Steel compositions used for the lunette trailer frames identified in this technical bulletin are also shown

in appendix A. Virtually all steels can be welded. Steels used in semitrailer frames, shown in appendix B, are weldable.

Frames fabricated from heat-treated steel may be repaired by welding and reinforcing where possible (See TM 9-237,

pages 7-24 thru 27). Similarly all aluminum components of a trailer frame may be weld repaired according J to

procedures described in TM 9-237 (pages 7-28 thru 34).

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Frame Assembly. Lunette trailer and semitrailer frame members are assembled with bolts, rivets, or welded

joints, or by a combination of these methods.

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Frame Galvanization. Frames that have been coated with zinc (galvanized) to prevent corrosion require

special repair procedures. Prior to repair, the zinc coating must be removed After repairs have been completed, the

repaired area must be re-galvanized using cold galvanizing spray.