Interpretation ID: nht68-3.19

DATE: 03/25/68

FROM: AUTHOR UNAVAILABLE; William Haddon, Jr., M.D.; NHTSA

TO: Renault

TITLE: FMVSS INTERPRETATION

TEXT: Thank you for your letter of December 1, 1967, concerning tests made on the Renault 10 model for compliance with Federal Motor Vehicle Safety Standard No. 203.

We recognise the validity of a system which takes advantage of the energy absorbing characteristics of the surrounding vehicle structure as on alternative to the more conventional approach of employing on energy absorbing column and/or wheel. As you mentioned, SAE J944 was not written with that type of energy absorbing system in mind. The structure which you intend to employ to provide the energy absorbing requirements specified in Federal Motor Vehicle Safety Standard No. 203 might in reality first be severely stressed and deformed in a crash eltuation. Therefore any laboratory test used to evaluate such a system should recognize this detrimental influence. In the event that you would wish to submit a proposed alternative test procedure which incorporates a barrier test is specified in Standard No. 204 prior to testing for compliance with Standard No. 203, we would be pleased to consider such a request.

Your second point concerns the need for a more explicit definition of translational motion. SAE J944 states that the body-block contacts the wheel in translational motion. It does not say that this motion must continue after impacting the wheel. Your magnetic release mechanism appears to impart approximately translational motion to the body-block at impact and is a satisfactory procedure. The fact that the body-block is free to rotate forward after impact is a stimulation of an actual crash situation and the body-block was not intended by SAE J944 to be restrained in translational motion after impact. Since the body motion in on actual crash situation will very somewhat the Bureau feels that a more explicity definition of translational motion is unnecessary.

The third series of tests as described in Report No. 287.397 using a right test fixture and the free flying body-block are compatible with the SAE J944 test procedure.

Your interest in motor vehicle safety is appreciated.