Skid Resistance Experiment
MEASURING SURFACE FRICTIONAL PROPERTIES USING BRITISH PENDULUM SKID RESISTANCE TESTER.
The British Pendulum Skid Resistance Tester is an impact type pendulum used to measure the energy loss when a rubber slider edge is propelled over a test surface. The values measured represent the frictional properties and are expressed as BPN (British Pendulum Number).
In skidding phenomenon, the distance travelled by wheel on the road is more than the circumferential movement.When brakes are applied, wheels get locked and still if the vehicle moves ahead, longitudinal skidding is said to occur.
In slipping, the distance traveled by wheel on the road is less than the circumferential movement. If the wheels of the vehicle are rotating but the vehicle is not moving forward, then slipping is said to occur.
MEASUREMENT OF TEXTURE DEPTH
It is also necessary to record the surface texture of the road surface tested. This is measured by Sand Patch Method. A known volume of fine sand of uniform particle size is poured on the road and spread to form a patch of a regular shape so that its area couldn’t be measured. Sand should be spread in such a manner that all “valleys” are filled to level of “peaks”. Then the texture depth can be computed by using the formula;