Interpretation ID: nht72-2.2

DATE: 02/23/72

FROM: AUTHOR UNAVAILABLE; Richard B. Dyson; NHTSA

TO: Cosco Household Products, Inc.

TITLE: FMVSS INTERPRETATION

TEXT: This is in reply to your letter of January 12, 1972, concerning Motor Vehicle Safety Standard No. 213, "Child Seating Systems." You ask specific questions, enclosing 3 diagrams, regarding the application of certain provisions of the standard to a child seat you wish to build. You state that this seat in its present form is composed of a tubular steel frame, and has a molded plastic shell to seat the child, to provide head restraint, and to assist in containing the child under lateral decelerations.

You ask whether the shell is a rigid component, stating that it will most probably be manufactured of polyethylene of about .100 inch thickness, and will be deformable by hand. We believe that such a shell could be considered a non-rigid component. There is not at present a definition of "rigid" in the standard and manufacturers should rely on generally available definitions of the term in determining whether or not components are rigid.

You state further that in those areas where the shell contacts the tubular frame it is unquestionably rigid, and ask whether energy-absorbing material could be applied between the frame and the shell, rather than between the shell and the child as specified in S4.10 of the standard. In the particular case you present, it is not clear whether the rigidity of the shell is inherent or results because of its attachment to the frame. If by cushioning this attachment the rigidity will be eliminated, we would no longer consider the component to be rigid. However, the amount of cushioning needed would depend upon the amount necessary to eliminate the rigidity, and would not necessarily be the 1/2-inch thickness specified in S4.10 for covering rigid components. This determination would be for the manufacturer to make, based upon his analysis of when the rigidity has been removed from the component.

With reference to the question presented on sketch 1, we believe it is answered in the preceding paragraphs. Concerning sketch 2 you ask what the standard requires at point N, where there is "essentially no energy-absorbing material between the bottom of the groove and the rigid tube." S4.10 of the standard requires rigid components that may contact the head or torso, with certain exceptions, to be "covered" with energy-absorbing material having a thickness of at least 1/2 inch. If the point N with which you are concerned can contact the head or torso of the child during impact, taking into account compression of the material adjacent to it, then it must be covered with at least the specified thickness of energy-absorbing material.

Your third sketch asks whether energy-absorbing material is required where the shell loops over the tubular steel frame, when the side of the shell is greater than 24 square inches. You are apparently assuming that the area in question is contactable as that term is used in S4.10. In our view the answer to this question depends upon whether the part of the seat in question is actually a "side" and if so if its rigidity is uniform. If the area in question creates a frontal projection we would not consider it to be a "side" under S4.10. If it does not, but the side is significantly more rigid in the area of the tubular frame, then we would not consider the exemption in S4.10.3 to apply, since the shell would not be one component. The hazard created would be identical if the tubular frame were exposed, and not covered by the shell.

Finally, you ask for any information on the status of Notice 5, published September 23, 1970 (35 F.R. 14786). A final rule based on this notice is in preparation, and we expect that it will be issued in the near future. At the same time, we have placed in the docket a report entitled "Report of Test on Child Vehicles and Their Energy Absorbing Materials." This report summarizes recent test work done to investigate test procedures for head restraints and energy absorbing materials for child seats.