Abstract
In the equestrian sport of three-day eventing there have been many serious horse and rider injuries and fatalities due to rotational falls. The MIMsafe system MIMclip was created to reduce the amount of fatal rotational falls. Finite element analysis determined that the stresses were almost 9 times higher than the yield stress (YS) of the steel alloy (450 ksi (3,103 MPa) versus 51 ksi (352 MPa)). The YS was estimated based on the hardness and microstructural evaluation. Fracture surface analysis of failed MIMclips in the field which confirmed a ductile failure mechanism. Finally, a cross country table jump was built to compare the results of the stress analysis models to a full-scale condition. The MIMclips did not activate even using energies as high as 330 foot-pounds (447 Joules). The results indicate that the current kettlebell testing standard is only applicable to the post and rail jump geometry.
The test results, along with in-situ visual observation using high speed photography displaying flexure in the table during testing, indicate that the current MIMclips are overdesigned for the table configuration. The final conclusion is that a different test criterion needs to be developed for cross country tables and a lower strength MIMclip should be specified.