The Linear Test

The linear test is designed to measure the energy absorption characteristics of the motorcycle helmet shell and liner. When carrying out the linear impact test a twin wire guided test apparatus is used. This equipment is similar to that used in the British Standard BS 6658:1985.

Before commencing the test, the helmet is placed onto an appropriately sized head form and this is placed onto the guided carriage. The carriage is raised to a certain height above the anvil and released. The helmet, head form and carriage accelerate to impact upon a fixed anvil. On impact, the lateral and rotational motion is controlled by the tensioned wire and the carriage. This reduces the potential for a proportion of the impact energy to be dissipated through rotation. Pitch, roll and yaw motion of the helmet is controlled during the impact.

Research has shown that this method of linear impact is better suited for the SHARP performance rating than the free motion test apparatus, which allows the helmet to slide and rotate on the anvil, thus reducing the measured peak acceleration. [Mellor et al, 2007]

Research has shown that the twin wire guided test method provided the most repeatable helmet tests and the most accurate results, especially when compared with the free motion prescribed in the UN ECE Regulation 22.05. [Mellor et al, 2007]