Interpretation ID: nht92-4.31

DATE: August 20, 1992

FROM: Richard Allison -- Program Manager, The Bott Group, Inc.

TO: Paul Jackson Rice -- Chief Counsel, NHTSA

TITLE: FMVSS No. 216, "Roof Crush Resistance-Passenger Cars", Request for Interpretation

ATTACHMT: Attached to letter dated 9/21/92 from Paul Jackson Rice to Richard Allison (A39; Std. 216)

TEXT:

The Bott Group, Inc. (a Design, Sales & Engineering firm for manufacturers of roof racks (luggage racks), decklid racks and accessories), on behalf of all O.E.M. clients who use our products, requests the Agency render an interpretation of the requirements of Federal Motor Vehicle Safety Standard No. 216, "Roof Crush Resistance-Passenger Cars", while considering the conditions as described herein.

To be specific, The Bott Group requests an interpretation of 1) the proper application and orientation of the test device (S6.2 of this standard) and 2) the distance the test device is allowed to travel (paragraph S4 of this standard), when testing vehicles equipped with roof mounted accessories, such as roof racks (luggage racks).

This accessory neither contributes to nor detracts from the actual strength of the roof panel and would collapse easily upon application of the forces as specified in paragraph S6.3 of the standard. The roof rack examples we present for consideration, in the attached documentation, can be easily removed for compliance testing.

Roof racks are positioned on the roof panel surface to lend aesthetic enhancement to vehicle contours. This could influence the positioning of the test device (per S6.2), as well as render impossible compliance with the maximum allowed travel of the test device (per S4), and thus, not achieve the true objective of the standard.

The Bott Group roof rack designs fall into two unique categories:

1) Four Seasons Style Has adjustable/removable crossbar assemblies with end supports that move fore and aft above the vehicle roof in fixed, outer channels. Refer to Figure 1 on attachment "A".

2) Elevated Siderail Style (with fixed position end supports) Has adjustable crossbar assemblies that move fore and aft above the roof surface by sliding in an elevated, channeled siderail assembly, however, the end supports are in fixed positions on the vehicle roof. Refer to Figure 2 on attachment "B".

Please consider, for instance, the roof rack example in Figure 2 on attachment "B". The fixed position, front end support of the siderail assembly is mounted in the area of the "B" pillar on the roof surface.

Under normal conditions this style of roof rack assembly is not removable during use, but it can be easily removed for testing.

The adjustable crossbar assembly on the roof rack example shown in Figure 1 on attachment "A" (normal forward positioning is also in the "B" pillar area) can:

1) be adjusted to its rearward most position out of the contact area of the test device or,

2) be removed completely or,

3) the entire roof rack assembly can be easily removed for testing.

The Bott Group believes that there are three different test conditions which should be considered. We have illustrated the differences in the positioning of the test device (refer to Figure 3 on attachment "C").

Condition 1- Test conducted without a roof rack installed or the roof rack has been removed and the test device has been positioned as outlined in S6.2. The first point of contact has been established and is indicated (marked "A").

NOTE: Test condition 2 & 3 assumes that the "elevated siderail style" roof rack with the fixed position end supports is used.

Condition 2- Test conducted with a roof rack installed and the test device positioned the same as in test condition-1. Using the first point of contact established in condition-1 (marked "A"), as reference, the test proceeded. The actual first point of contact during this condition was to the fixed end support of the roof rack (marked "B") and this was a considerable distance rearward from the original contact point "A" established in condition-1.

The dimension between point "A" and point "B" varies according to the fore/aft positioning of the fixed end support of the roof rack on the roof surface.

When the first point of contact, "B", occurred, the second item we identified was a gap between the bottom of the test device and the roof surface at point "A". This may not comply with S6.2(c).

Condition 3- Test conducted with a roof rack installed and the test device positioned as outlined in S6.2 to the contact point (marked "B") established in test condition-2. This condition seemed to create three situations.

a) The complete test device is relocated some distance rearward of the original positioning in test condition-1 and its established contact point (marked "A"). This may not provide test requirements per S4, S6.2 & S6.4 of the standard.

b) The positioning of the test device left a gap between the bottom surface of the test device and the surface of the roof at point "A". The test device, not being tangent to the surface of the vehicle roof, when first point of contact occurs, may not comply with S6.2(c) of the standard.

c) With the test device not making contact (not tangent) with the roof surface at point "A" when the required pressure is applied to the test device, as specified in S6.3, a considerable amount of test device travel is required before contact (tangency) with the roof surface point "A" is made. This may cause non-compliance with S4, as measured in accordance with S6.4, of the standard.

The Bott Group requests the Agency's interpretation of which test condition above, number 1, 2 or 3, is correct and thus, satisfies the intent of FMVSS No. 216.

If test condition 2 or 3 is deemed correct, can the additional amount of test device travel, required between first point of contact and the actual contact (point "A") on the roof surface, be added to the "allowed distance" of test device travel when determining compliance with paragraph S4 of the standard?

The Bott Group is concerned for the timeliness of this matter because of the design timelines we work under (several model years in advance) and we would like to thank the Agency, in advance, for its kind, prompt, attention and consideration of this matter.

(Figures omitted)