This paper evaluates the validity of helmet retention system test methods by considering both the impact mechanics of accidents, and the mechanical design of the tests. The test methods are simple falling weight laboratory tests where the drop height of the mass is adjusted to reproduce the type of failures found in accidents. The causes of force peaks and oscillations in the test traces have been identified. A means has been found of obtaining reliable chin strap force measurements. Recommendations are made for improving the test, so that chin straps and buckles are adequately strong but not over-designed. It is vital to measure the dynamic force, and to relate it to the likely force in an accident. The retention system effectiveness test has reduced the incidence of helmet roll-off by an inertial mechanism, but oblique impacts can still cause roll-off. (A)
Samenvatting