Senior Development Engineer
New Products Office
Magneti Marelli UK Ltd.
Walkmill Lane, Cannock
Staffordshire WS11 3LP
Dear Mr. Tolley:
This responds to your letter of April 28, 1995, asking for an interpretation of the torque deflection test specified in paragraph S18.104.22.168 of Motor Vehicle Safety Standard No. 108.
The second sentence of this paragraph states that "The downward force used to create the torque shall be applied parallel to the aiming reference plane, through the aiming pads, and displaced forward using a lever arm such that the force is applied on an axis that is perpendicular to the aiming reference plane and originates at the center of the aiming pad pattern." You believe that the instructions for performing the test are not sufficiently precise and can be interpreted in different ways. Specifically, you are concerned that the standard fails to adequately define the center of rotation of force, which is necessary to determine the downward force applied to the headlamp.
We agree with you, and are examining ways in which the standard might be amended to address the problem you have brought to our attention. Noting that you have presented four possible answers (as well as "some other point"), our comment is that, until NHTSA clarifies the matter, a manufacturer should choose a center of rotation that appears the most appropriate for the design of mechanically aimable headlamp under consideration, in certifying that the headlamp meets all applicable Federal motor vehicle safety standards.
I am sorry that we could not be more helpful at this point. If you have any questions you may refer them to Taylor Vinson of this office (202-366-5263).
John Womack Acting Chief Counsel