Interpretation ID: nht80-1.4
DATE: 01/11/80
FROM: AUTHOR UNAVAILABLE; F. Berndt; NHTSA
TO: Blue Bird Body Company
TITLE: FMVSS INTERPRETATION
TEXT: This responds to your October 8, 1979, letter and follow-up meeting in which you ask several questions about the compliance of your school buses with Standard No. 221, School Bus Body Joint Strength. In your letter, you ask about four separate joints and ask whether they would be required to comply with the standard.
As you know, the standard applies to any joint of a body panel that encloses bus body space and a body structure member. An exception from the standard exists for those joints that connect maintenance access panels. In our meeting with you, we stated the agency's objection to the existing industry practice involving maintenance access panels, and further stated that the agency was contemplating rulemaking to restrict the maintenance access panel exception.
Responding directly to the four joints that you reference in your letter, you first ask whether the contact point between the headlining panel and the spring clip is a joint subject to the standard. A spring clip is entirely enclosed within a bus wall. Its function is to aid in holding the body panel in place while the rivets or adhesives are being applied. It serves no function beyond that. The agency does not believe that a spring clip is either a body structure member or a body panel enclosing occupant space. Accordingly, the joint of this clip and any other body member is not a joint subject to the standard.
In your second question, you ask whether the joint between the headlining panel and the headlining panel positioning tab is a joint subject to the standard. The positioning tab is a device that is approximately two inches long and contacts the headlining panel in two places between the bus body bows. The purpose of this tab, is to prevent buckling of the headlining panel between the two bows. The agency concludes that positioning tabs are body structure members. Therefore, if they contact a body panel at its edge, the intersection of these two components creates a joint subject to the standard.
Your third question asks whether an extruded aluminum sash assembly must comply with the standard. You state in your letter that this assembly is part of the window and, therefore, exempt from the requirements. The aluminum sash assembly to which you refer is an add-on device above the window found in your larger buses to provide more headroom. The agency concludes that this device has no function as a part of the window but merely is a trim panel that serves to cover part of the bus sidewall. Accordingly, the joint connecting this panel to the remainder of the bus structure would be required to comply with the standard.
Finally, you ask whether the joint between a positioning angle and a headlining panel must comply with the joint strength requirements. A positioning angle is a body structure member that runs from bow to bow and supports the edge of the headlining panel to prevent buckling. The agency concludes that this positioning angle is a body structure member and its connection with a body panel is a joint subject to the standard's requirements.
SINCERELY,
BLUE BIRD
BODY COMPANY
October 8, 1979
Frank Berndt Chief Counsel National Highway Transportation Safety Administration Department of Transportation
SUBJECT: FMVSS 221
REF: 1. Letter from Francis Armstrong to Albert L. Luce dated 6-1-79; NEF-31 MPa CIR 2087
Dear Mr. Berndt:
The subject standard requires 60% joint strength for certain defined joints on school buses; other joints, as defined in S4 of the standard, are exempted. The purpose of this letter is to seek confirmation that certain aspects of a proposed design change are exempted under the provisions of S4.
In preparation for initial compliance with the subject standard, Blue Bird Body Company redesigned the wire service panel and obtained approval for the new design; please refer to letter to and from NHTSA on February 13, 1976 and April 26, 1976 respectively.
In reference 1, NHTSA raised questions concerning our wire service panel. The questions carried no allegations of non compliance. However, in keeping with Blue Bird Body Company's philosophy of meeting the spirit of NHTSA regulations as well as the letter, we are now proposing changes to the wire service panel and surrounding components. These changes are described by the two enclosed prints.
The prints show cross sections of the proposed wire service panel design for 74" headroom and 77" headroom vehicles. The specific items with regard to this design proposal which we would like you to confirm are:
1. That the area of contact between the headlining and spring steel clip is not a joint subject to FMVSS 221 requirements. As shown on the prints, this clip is used only as an assembly aid to support headlining panels while permanent fasteners are installed. The clip will be approximately 3/4" wide. While the permanent integrity of the design is not dependent on the clip, the intent is to leave it in place after the permanent fasteners are installed.
2. That the area of contact between the headlining and the headlining panel positioning tab on the header of 74" headroom models is not a joint subject to the requirements of FMVSS 221. The purpose of the tab is to prevent the headlining from bowing outward between roof bows. The tab is shown full size on the 74" headroom print. There will be two tabs per window section.
3. That the window frame extension on 77" headroom models is exempted under the provisions of S4 where windows and body panel joints designed for ventilation are exempted.
4. That the headlining panel positioning angle on 77" headroom models is exempted. This angle performs the same function on 77" headroom models as the headlining panel positioning tabs serve on the 74" headroom models; see item 2 above.
Your early review and confirmation of these items will be appreciated. We are available for conference at your convenience to answer any questions you might have.
W. G. Milby Manager, Engineering Services
ENCLS.