Rigid Two- and Three-Wheeled Vehicle Roll Over vs. Pitch Over Threshold Models: Testing and Analytical Modifications

The phenomenon of bicycle pitch over is simple in concept, yet determining threshold criteria for pitch over has yet to be well established, particularly when it comes to determining whether or not a bicycle’s front wheel will roll over a particular obstacle or not. Two prior SAE papers have laid out 3 different approaches to determining this threshold criteria; however, all three remain untested and thus unvalidated. To test the two analytical models, the dimensions and center of gravity location for a test rider on a tricycle were measured, and the test subject system was ridden over a series of progressively taller square edge obstacles until the tricycle transitioned from rolling over to stopping/pitching over. The test speeds were varied between 5 and 10 mph to keep the tricycle from fully pitching over and/or damaging the test tricycle. From this testing, it was demonstrated that the test tricycle and rider was able to ride over taller obstacles than calculated by the analytical methods. It is hypothesized that this discrepancy is due at least in part to dynamic tire deflection, and a modification to the analytical methods is proposed to better align their calculated thresholds with the empirical test results.