Rigidity test of a helmet is done to determine its ability to withstand deformation due to any force acting on it.

Rigidity tester consists of two solid steel plates held parallel to each other with the help of four spacer rods. A loading plate with a guide rod is guided along a vertical axis in a brass bush held in the upper plate. The weight of the loading plate assembly is equal to the initial load.

Major load is applied in specified steps by placing disc shaped dead weights on top of the loading plate assembly. The deflection of the helmet is measured with the help of a scale fixed to the frame and a pointer fixed to the loading plate assembly.