Prediction of Steady State Roll Threshold for Loaded Flat Bed Trailers - Theory and Calculation

The flexibility of flat bed trailers is shown to be an important consideration in determining the static roll threshold for a loaded Class 8 tractor trailer. The development of an easy to use static roll threshold model using Microsoft® Excel's nonlinear equation solution capability provides a tool that should be useful to the trailer designer, dock loading manager and the traffic safety manager responsible for the training of drivers. It can be seen for low stiffness flat bed trailers that the trailer torsional stiffness is a more important parameter than typical suspension or tire stiffness. Further, even for “stiff” flat bed trailers the use of the rigid body roll criteria (T/2h) or the 2-D “planar” model can produce significant error in many practical loading configurations.