Description from Equestrian Surfaces – A Guide (White Paper).
The Orono Biomechanical Surface Tester was developed for use on Thoroughbred racecourses in the United States, and then adjusted for equestrian riding surfaces at SLU in Uppsala. It is often called “the mechanical hoof”, as by dropping a hoof shaped projectile at an angle to the ground it mimics the impact of the horse’s hoof on the surface. The machine is mounted to a truck or van of sufficient weight and is supported by a frame, which is placed on the ground for stability during testing.
The metal “hoof” is mounted beneath a heavy weight, which is dropped to the ground between two guide rails. When the weight is released, the mechanical hoof first hits the ground at a specific angle which has been determined based on measurement from high-speed motion capture of horses’ legs. Thus the mechanical hoof mimics the motion of the forelimb of a horse during the early landing/touchdown phase, as a simultaneous downward motion and forward slide of the ‘hoof’ occurs when it contacts the ground. An accelerometer mounted on the metal hoof measures the surface hardness. A load cell measures the impact of the heavy weight as it loads the ‘hoof’ to a maximum in both the vertical and horizontal directions. This, in combination with position sensors on the hoof, measures the cushioning of the surface during the loading phase, the amount of grip and the surface responsiveness. For testing of equestrian surfaces the mechanical hoof of the machine has been set to mimic that of a medium sized Warmblood horse.