noteven Posted May 2, 2018 Report Share Posted May 2, 2018 My Carriage trailer has the "normal" rv upper 5th wheel plate and king pin location stuck out ahead of where it mounts to the frame of the trailer for pickup towing. The king pin centerline is 13-3/4 inches ahead of the center of the frame extending down from the trailer that the "pin box" bolts to. The pin weight road ready is 3400lbs Is this correct: (13.75/12) x 3400 = 3895.8 lbs-ft of torsion on the mounting frame ? Plus 3400lbs vertical? Does the draw pin force - that is the force applied through the pin to move the trailer or decelerate the trailer - remain equal whether the pin is forward or straigth down? The frame is no doubt designed to withstand these forces... But when I smash over a bridge deck or hit a crossways hole/dip at speed (see Interstate 5 north of Grapevine, CA) I imagine in my pea brain those forces are being multiplied by the lever the king pin is on the end of... I have room to use a straight up and down pin set up. My reason for changing would be for stress relief for the trailer frame. The 13-3/4" of length change wouldn't matter much either way. p.s. yep - I know what suspension 5th wheels (hitches) do. I'm asking about leveraged force (or not) on the trailer frame. Thanks Link to comment Share on other sites More sharing options...
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