Structural design issues?

Lynnmor wrote:
My frame cracked where the cross-members are welded to the "I-beam"

The side to side flexing causes cracks, so I installed beams from hanger to hanger.

Wow, very nice work!

My frame cracked where the cross-members are welded to the "I-beam"

The side to side flexing causes cracks, so I installed beams from hanger to hanger.

The frame probably needs 3 cross members added at the spring hanger locations to keep it from twisting and breaking. Boxing the i-beam wouldn't be a bad idea either. Generally, RV trailer frames are typically built as thin and light as possible for their GVWR, so they are inherently weaker than other types of trailer frames built heaveir for hauling cargo.

It's been on here before with photos for reinforcement/welding. Poor design as far as I'm concerned. The side force of the suspension that is welded under the bottom plate is acting like a lever and twisting from side to side. Some people weld in reinforcement plates from the bottom edge toward the top. Other option is to try and "box" the frame to make it more rigid.

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