Interpretation ID: nht80-4.7
DATE: 10/03/80
FROM: AUTHOR UNAVAILABLE; S. P. Wood for F. Berndt; NHTSA
TO: William Blythe
TITLE: FMVSS INTERPRETATION
TEXT:
October 3, 1980 NOA-30
Mr. William Blythe 1545 University Avenue Palo Alto, California 94301
Dear Mr. Blythe:
This responds to your recent letter asking questions concerning the test procedures of Safety Standard No. 216 Roof Crush Resistance (49 CFR 571.216). Specifically, you are concerned with the proper applications of the test block forces specified in paragraphs S6.3 and S6.2(d) of the standard.
Your first question asks whether paragraph S6.3 allows the force on the test block to be applied "essentially opposite the initial contact point of the roof to the block." Paragraph S6.3 specifies that the force required by the standard shall be applied in a downward direction to the lower surface of the test device. Figure 1 of the standard illustrates this procedure and indicates that the force is to be centrally applied to the loading block. This procedure will be followed during tests by the agency to determine the compliance of particular passenger cars with Safety Standard No. 216. Therefore, we would not recommend that you apply the force opposite the initial contact point of the test block with the roof.
Paragraph S6.2(d) of the standard specifies that the initial contact point (with the roof) is on the longitudinal centerline on the lower surface of the test device and 10 inches from the forwardmost point of the centerline. Your second question asks whether this 10-inch dimension should be maintained if this places the leading edge of the test device behind the leading edge of the roof and the A-pillars. You state that this would occur with certain roof configurations which tend to be high in the center (i.e., in which the leading edge of the roof is not the highest point of the roof). A manufacturer should adhere to the 10-inch dimension even if this means the leading edge of the test device will not be forward of the A-pillar and the roof's forward edge. The test procedures specified are standardized procedures which the agency applies to all passenger cars regardless of roof configuration. Thus, the agency would maintain the 10-inch dimension even when testing a roof with a higher center than its leading edge.
I would like to point out, however, that the test procedures specified in the safety standards only document how the agency will conduct its compliance tests. Manufacturers are not required to test vehicles according to the procedures specified. A manufacturer's responsibility is to exercise due care to ascertain that its vehicles are in fact in compliance with the standards (15 U.S.C. 1397). If you are convinced that the procedures mentioned in your letter would accurately test the compliance of a particular vehicle with Safety Standard No. 216, you are certainly permitted to use those procedures. It is up to the manufacturer, however, to determine whether it has in fact exercised due care to determine compliance.
I hope this has been responsive to your inquiry.
Sincerely,
Frank Berndt Chief Counsel
August 24, 1980
Office of the Chief Counsel National Highway Traffic Safety Administration 400 Seventh Streee, S.W. Washington, D.C. 20590
Attention: Mr. Huyh Oates, Esq.
Reference: Motor Vehicle Safety Standard No. 216, "Roof Crush Resistance--Passenger Cars"
Gentlemen:
This letter is pursuant to my telephone conversation with Mr. Hugh Oates, on August 7, 1980. I am writing at the suggestion of Mr. Ed Jettner, NHTSA Project Engineer for MVSS 216, in an attempt to clarify certain aspects of that Standard. My organization is preparing to conduct tests in accordance with MVSS 216, and we perceive certain apparent ambiguities in the Test Procedure (paragraph S.6 of MVSS 216), for which we need clarification. Essentially, we have two questions to which we seek answers.
1. What should be the location of the applied force with respect to the upper surface of the test block?
Paragraph S6.3 reads: "Apply force in a downward direction to the lower (sic) surface of the test device...," but does not specify the location of the force on the surface of the block. Figure 1 seems to imply that the applied force should be centered in the upper surface of the block, but the location of the force is not dimensioned. Clearly, if the applied force could be located directly opposite the point of initial contact of the test block with the roof, the load transmitted to the roof would be unchanged, and at the same time the loading frame needed to maintain the block at its specified angles would be much simpler to construct. Thus the question is, can the applied force on the block be located essentially opposite the initial contact point of the roof to the block? This location is much preferred over the control location implied in Figure 1 of the specification because the test frame is thereby greatly simplified and no change results in the loads transmitted to the roof.
2. Should the ten-inch dimension from the leading edge of the loading block to the initial contact point be maintained even if this locates the leading edge of the block aft of the A-pillar (or leading edge of the roof)?
Paragraph S6.2(d) specifies that the "initial contact point ... is ... 10 inches from the forwardmost point..." of the loading block. Also, Figure 1 implies that the forward edge of the block is forward of the leading edge of the roof. For some roof configurations (which tend to be high in the center), holding the ten-inch requirement will move the leading edge of the block to a position aft of the leading edge of the roof. In such a situation, should the ten-inch dimension be maintained, or should the leading edge of the loading block remain forward of the A-pillar, thus increasing the ten-inch dimension? In order to simulate, even approximately, the actual loading which might be encountered in a roll-over, it would seem desirable to keep the leading edge of the loading block forward of the A-pillar so that the A-pillars are loaded directly.
Because of our test program schedule, we would appreciate your response at the earliest possible time.
Very truly yours,
William Blythe, Ph.D.
WB:gh