Helmets are subjected to penetration test at two points at a minimum distance of 75 mm from each other within the area of protection after being subjected to the process of conditioning which has given the least satisfactory results in impact absorption test. During this test the tip of the punch shall not come closer than 5 mm measured vertically to the head-form.
The Penetration Tester for helmets consists of an arrangement to hold a head-form on which the helmet under test is kept. The arrangement has five degrees of freedom so that any point on the surface of the helmet can be brought under the point of impact in a manner such that the plane tangential at the point is substantially horizontal.
A metal punch of a specified shape and weight guided in a bush is kept vertically above the point of impact. A metallic weight of specified mass is allowed to drop on the punch from a specified height. The minimum distance between the tip of the punch and the head-form at the time of impact is determined with the help of molding clay.
The complete arrangement is built over a rigid fabricated steel frame. The tester is finished in gray hammer tone painting and bright chrome plating to give it a corrosion resistant finish.
The head-forms used for conducting the test are not supplied with the equipment but are available as optional accessories.
IS 4151 - 1993 : Specification for Protective Helmets for Motorcycle Riders.