Interpretation ID: nht76-2.9

DATE: 04/26/76

FROM: AUTHOR UNAVAILABLE; F. Berndt; NHTSA

TO: Blue Bird Body Company

TITLE: FMVSS INTERPRETATION

TEXT: This responds to Blue bird Body Company's February 13, 1976, question whether 47 described intersections of bus body components qualify as "body panel joints" subject to the requirements of Standard No. 221, School Bus Body Joint Strength. You also ask what test procedures are used in testing joints if the means described in S6.1.1 or S6.1.2 cannot be employed due to the configurations of the intersecting components.

The terms which establish the applicability of the requirements of the standard to a particular section of a school bus body are defined in S4 of the standard. Read together, they establish the following test. If the edge of a surface component (made of homogeneous material) in a bus that encloses the bus' occupant space comes into contact or close proximity with any other body component, the requirements of S5 apply, unless the area in question is designed for ventilation or another functional purpose or is a door, window, or maintenance access panel. Applying this test to the 47 intersections of bus body components you describe, it appears that the arears corresponding to the following numbered paragraphs of your letter are bus body joints and therefore must meet the 60-percent joint strength requirements: 1, 4, 5, 6, 7, 8, 9, 11, 13, 14, 15, 19, 20, 23, 26, 28, 29, 50.

The front and rear headers described in paragraphs 2 and 12 are considered primarily structural and have only an incidental role in enclosing the occupant space and, therefore, are not considered "body panels" for purposes of the requirements.

The wire molding discussed in paragraphs 3 and 10 is considered a maintenance access panel, excluded from the requirements only if a wire is installed behind the molding.

The bumper trim strip described in paragraph 17 is not considered to have a function in enclosing the occupant space and is therefore not considered a body component for purposes of the requirements.

Your assumption that components located entirely below the level of the floor line are not subject to the standard is correct. However, body panels that do "enclose bus' occupant space" because a portion lies above the floor line are subject to the requirements. Thus, the rear center skirt described in paragraph 16, the bumper trim panel described in paragraph 18, and the auxiliary cross members described in paragraph 21 are not subject to the requirements.

The rubrails described in paragraphs 22, 23, 27, 28, and 29 are not themselves considered to have a function in enclosing the occupant space and therefore are not considered body components for purposes of the requirements. For purposes of testing the complex joints to which they are fastened, they should be modified as necessary to prevent them from affecting testing of the underlying joint.

The wheelhousing trim described in paragraph 24 is not considered to have a function in enclosing the occupant space and is therefore not considered a body component for purposes of the requirements.

Because the plywood described in paragraph 25 is attached to a floor panel and is only added to some buses for insulation purposes, it is not considered to have a function in enclosing the occupant space and is therefore not considered a body component for purposes of the requirements.

The extruded aluminum trim described in paragraph 30 is not considered to have a function in enclosing the occupant space and is therefore not considered a body component for purposes of the requirements.

The NHTSA agrees that paragraphs 30 through 36 and 38 through 46 describe joints between maintenance access panels and the bus body. The ventilation duct in paragraph 37 is the type of ventilation space that is not subject to requirements for joint strength.

In many of your requests for clarification, you asked what means would be employed to test joints in which the two body components in question are not flat surfaces in the same or parallel planes. The NHTSA intends to test joints that are not capable of being tested as specified in S6.1.1 or S6.1.2 by determining the nature of the two body components and testing identical materials joined by the same means as is used by the school bus manufacturer. The materials will be flat and conform to the dimensions described in Figure 1, and they will be oriented in the same fashion as described in Figure 1. For example, the 90-degree angle at the joint described in paragraph 20 is ignored for purposes of the NHTSA test procedure by simulating the joint and using opposing forces in the same or parallel planes. In this way, the agency can examine a manufacturer's technique to see if the fastening method constitutes the exercise of due care in complying with the joint strength requirement.

You also asked what procedure would be used in testing joints where more than two panels or body components are joined by one fastener (example in paragraph 29). In these cases, the definition of "body panel joint" in S4 describes several joints, involving one at each intersection area that qualifies as joint. For each pair of components, the tensile strength of the weaker panel is determined, and the joint is required to sustain a load of not less than 60 percent of that tensile strength. For example, in the case of two side panels riveted to a bow, one joint would be between the two lapped panels and 60 percent of the weaker panel would be the test requirement. At the same time, a separate test of the joint between the bow and the panel that contacts the bow would be required, with 60 percent of the weaker component's tensile strength established as the level of strength for testing.

I trust that this discussion will permit a determination of what portions of your products are subject to the requirements of Standard No. 221 and what test procedures are employed in satisfaction of the requirements.

SINCERELY,

BLUE BIRD BODY COMPANY February 13, 1976

Richard B. Dyson Assistant Chief Counsel National Highway Traffic Safety Administration

The purpose of this letter is to request interpretations on whether or not certain portions of our bus body construction are considered to be joints, which are subject to the requirements of FMVSS 221, School Bus Body Joint Strength.

As you can see this is quite a lengthy letter; however, we feel it is necessary because the definitions given in the subject standard leave considerable latitude for interpretation.

We have prepared individual sketches and photographs of each area in question and keyed these sketches to the enclosed isometric drawing #47, Body Construction and Conventional Joint Strength, and photograph #48, Blue Bird All American front section and photograph #49, Blue Bird Conventional front section. These sketches are not necessarily to scale, but are rather intended to communicate the pertinent construction details.

In order to facilitate consideration of these construction areas, I will list them by sequence using the balloon numbers on the isometric drawing and two front end photographs.

1. Upper cowl to cowl. The upper left photograph shows these two members on the left front corner of the body. The upper right photograph shows this same sub-assembly from the inside. The front portion where the body cowl meets the chassis cowl is forward of the windshield area while the rearward portion is aft of the windshield area.

We know of no practical way that this seam can be tested using the procedure outlined in S6 because of the embossed portion of the upper cowl and because of the radius of curvature of these members.

Is this a joint under FMVSS 221 and if so, how should it be tested?

2. Front header to front corner post. The photograph shows the upper right corner of the bus body near the entrance door area looking from inside the bus. The horizontal lower surface of the front header is an exposed panel in the interior body area. However, we know of no practical way to assure 60% joint strength between this panel and the tubular vertical front corner post, which is a structural member; nor do we know of a practical way in which it can be tested using the procedure outlined in S6.

Is this a joint under FMVSS 221, and, if so, how should it be tested?

3. The photograph shows the wire molding, which is installed just above the side window area. The photograph is taken from the opposite side of the body looking up from a seated position. The sketch shows a section of this molding with its attachment to the 14 gauge bow and its function in covering and providing access to the wire harness. The wire molding runs the full length of the bus body on the inside on both right and left. It covers and provides access to the main body wiring harness. However, in some models, the wiring harness is only routed on the left side, but a right side wire molding is still provided.

We are assuming that this wire molding is a "maintenance access panel" as described in S4 and, therefore, not subject to the joint strength requirements.

Is this also a valid assumption on those models in which there is no right side body wiring harness, but the wire molding is still provided?

4. Header to headlining. The photograph shows the header which acts as a lintel above each window and is bolted between the main body posts. The photograph also shows a headlining panel in place looking from inside the bus. The sketch shows details of how the headlining rests on a ledge which is formed into the header. This ledge merely acts as a locater to facilitate installation of the headlining panel during the manufacturing process. The headlining panel is then riveted to the bows. There is no welding or mechanical fasteners between the headlining panel and the header. As shown in photograph #3, this is completely covered by the wire molding and, therefore, in our opinion, does not constitute a "portion of a bus that encloses the bus's occupant space" as referenced in S4, and is, therefore, not subject to the requirements of FMVSS 221. Furthermore, we know of no way to connect the headlining panel to the header to meet the requirements of FMVSS 221 or to test it according to the procedure in S6.

Are we correct in our assumption that this is not a "body panel joint" and, therefore, not subject to the requirements of FMVSS 221?

5. Inside side panel to gusset. The gusset is a formed longitudinal body frame member which runs the full length of the bus body on either side. The formed flange in the gusset is used as a mounting ledge on which the outboard side of the passenger seats is mounted. The inside side panels are shown in the upper portions of the photograph and the gusset is shown in the lower portion of the photograph.

Is the area of contact between the inside side panel and the gusset a "body panel joint"?

6. Gusset to floor. This shows the area of contact between the 14 gauge floor panels and the 16 gauge longitudinal floor gusset which is a formed longitudinal framing member running the full side of the bus body on both right and left. The upper portion of the photograph shows the longitudinal gusset ledge; the mid portion of the photograph shows the vertical portion of the longitudinal gusset; and the lower portion of the photograph shows the 14 gauge floor. Because these members meet each other at right angles, we know of no practical way to test them using the procedure described in S6. Furthermore, the area of contact between these members presents no edge to bus occupants. We are, therefore, assuming that this does not constitute a "body panel joint" as described in S4 and is, therefore, not subject to the requirements of FMVSS 221.

Is this assumption correct?

7. Wheelhouse assembly. The photograph shows a rear wheelhouse assembly which provides tire clearance when the suspension goes into the jounce position. In the finished bus this assembly is covered with floor covering where it meets the floor.

Because of the configuration of this assembly, we know of no practical way to test it according to the procedure defined in S6.

Is this a "body panel joint" and, if so, how should it be tested?

8. Inside side rear vision panel to bow. The photograph shows the rearmost side split sash window and the rubber mounted rear vision glass looking from inside the bus. As seen from the photograph and in the cross section sketch, the joint between the inside vision panel and the bow is completely covered by the extruded aluminum frame around the window.

In our opinion the joint between the inside rear vision panel and the bow does not enclose the bus's occupant space and is, therefore, not a "body panel joint", which is subject to the requirements of FMVSS 221. Is this assumption correct?

9. Side vision header. The photograph shows the left rear inside rear vision panel where it contacts the header, looking from inside the bus with the headlining panel and the wire molding removed. The sectional sketch shows the area of contact between the inside rear vision panel and the header. The upper edge of the inside rear vision panel is completely covered by the wire molding.

We know of no way that the area of contact between the header and the inside rear vision panel can be joined or tested according to FMVSS 221.

We are assuming this is not a "body panel joint" and is, therefore, not subject to FMVSS 221. Is this assumption correct?

10. Wire molding to rear upper inner panel. The photograph shows the longitudinal wire molding where it butts against the rear upper inner panel. This is a butt joint and, in our opinion, the wire molding constitutes a "maintenance access panel".

We are, therefore, assuming this joint is not subject to the requirements of FMVSS 221. Is this assumption correct?

11. Upper emergency door trim. The photograph shows the emergency door opening looking from the outside of the bus with the emergency door open. The purpose of the upper emergency door trim is to provide a door stop and dam against which the rear emergency door weatherstrip can seal. This is strictly a trim part which provides no structural function.

It is our opinion that the area of contact between the rear header and the upper emergency door trim does not constitute a "body panel joint" and is, therefore, not subject to the requirements of FMVSS 221. Is this correct?

12. Rear header to bow. The photograph shows the butt joint between the rear header and rear bow. The rear header goes across the full width of the bus above the rear emergency door. The lower surface of the rear header is an interior panel. We know of no way to join the rear header to the bow or test it according to the requirements of FMVSS 221. We are assuming this is not a "body panel joint" and is, therefore, not subject to FMVSS 221. Is this assumption correct?

13. Upper corner post to bow, belt bar and header. The photograph shows the left rear corner of the bus body looking from inside. The isometric sketch shows the right rear corner of the body looking from outside. The upper corner post acts as an interior panel. We know of no way to join the upper corner post to the bow, belt bar and header or to test it in accordance with FMVSS 221.

We are assuming these are not "body panel joints" and are, therefore, not subject to the requirements of FMVSS 221. Is this assumption correct?

14. Lower corner post to bow, belt bar and floor panel. The photograph shows the left rear corner of the bus body looking from inside. The isometric sketch shows the right rear corner of the bus body looking from outside. We know of no way to join the lower corner post to the bow, belt bar and floor panel or to test it in accordance with FMVSS 221.

We are assuming these areas of contact do not constitute "body panel joints" and are, therefore, not subject to FMVSS 221. Is this assumption correct?

15. Tag panel to floor. As seen from the sectional sketch, the tag panel meets the floor panel at right angles. We know of no way to test this in accordance with the requirements of S6.

We are assuming this is not a "body panel joint" and is, therefore, not subject to the requirements of FMVSS 221. Is this assumption correct?

16. Rear center skirt panel to rear emergency door post support. Because of the configuration of these parts, we know of no way to test them in accordance with the procedure of S6. We are assuming this is not a "body panel joint" and is, therefore, not subject to the requirements of FMVSS 221. Is this assumption correct?

17. Bumper trim strip. As shown from the photograph, this is merely a trim strip to improve the appearance of the rear of the bus where the bumper meets the body. Because of its function and because we know of no way it can be tested in accordance with the procedure of S6, we are assuming the bumper trim strip is not subject to the requirements of FMVSS 221. Is this assumption correct?

18. Bumper trim panel. As can be seen from the photograph, the bumper trim panel serves the purpose of improving the appearance where the bumper meets the outside side panel. It can also be seen that the bumper trim panel is below the floor line and is therefore outside of the occupant space.

We are, therefore, assuming this panel is not subject to the requirements of FMVSS 221. Is this assumption correct?

19. Side and rear vision inside to outside glass opening with rubber. The photograph shows the area of contact between the inside and outside rear vision panel flanges with part of the grazing rubber removed. As can be seen from the sectional sketch, this area of contact is completely covered by the glazing rubber which holds the glass in place. We know of no way to join the inside and outside rear vision panels or test them in accordance with FMVSS 221.

We are assuming this is not a "body panel joint" and, therefore, not subject to the requirements of FMVSS 221. Is this assumption correct?

20. Floor to floor. As can be seen from the sectional diagram, the testing procedure of S6 would put these fasteners in a tearing mode rather than in shear as was apparently assumed when the testing procedure was developed. The 14 gauge floor panels are covered with rubber floor covering in the finished bus.

We are assuming this is not a "body panel joint" and, therefore, not subject to the requirements of FMVSS 221. Is this assumption correct?

21. Floor to auxiliary cross member. The photograph shows the bottom side of a floor panel with hat section auxiliary cross members spot welded to the floor panel.

Because these auxiliary cross members are attached to the outside of the occupant space and are below the floor line, we are assuming the area of contact between the auxiliary cross member and the floor is not a "body panel joint" and is, therefore, not subject to the requirements of FMVSS 221. Is this assumption correct?

22. Rubrail to rubrail overlap. Because rubrails are attached to the exterior skin of the bus body in our opinion they do not "enclose the bus occupant space" and, therefore, do not constitute "body panel joints".

Therefore, we are assuming rubrail overlap joints are not subject to the requirements of FMVSS 221. Is this assumption correct?

23. Side vision side panel. The area of contact between the outside side vision panel and the outside side panel is covered by the rubrail as seen from the sectional diagram.

Is this a "body panel joint" or not, and, if so, how should it be tested; with or without the rubrail in place?

24. Wheelhousing trim to side panel. As seen from the photograph and from the isometric drawing #47, the wheelhousing trim is simply an angular piece of sheet metal to trim the cut edges of the side panels around the wheel opening cutout. This trim provides no structural function and is outside the bus's occupant space.

We are assuming this is not a "body panel joint" and is, therefore, not subject to the requirements of FMVSS 221. Is this assumption correct?

25. Plywood floor to metal floor. The photograph and sectional diagram show the installation of 5/8" thick plywood which is installed over the 14 gauge steel floor panels as optional equipment for insulation purposes. This option is primarily used in cold climates. The plywood provides no structural strength to the body. It is covered with rubber floor covering on the finished bus. We know no way to join the plywood to the floor or the plywood to itself in accordance with FMVSS 221.

We are assuming the plywood to steel and plywood to plywood are not "body panel joints" and are, therefore, not subject to the requirements of FMVSS 221. Is this assumption correct?

26. Bow cap to bow. As seen from the photograph and from the sectional sketch, the bow cap is merely a trim part to finish off the exterior of the structural body bow. Because of the configuration of these parts, we know of no way to test them according to the procedure of S6.

We are assuming the area of contact between the bow cap and the bow does not constitute a "body panel joint" and is, therefore, not subject to the requirements of FMVSS 221. Is this assumption correct?

27. Rubrail to side panel. As seen from the sectional sketch, the rubrail is added to the exterior skin of the bus body and does, therefore, not enclose the occupant space. We are, therefore, assuming that the area of contact between the rubrail and the outside panel does not constitute a "body panel joint" and is, therefore, not subject to the requirements of FMVSS 221. Is this assumption correct?

28. Side panel rubrail to sill. We know of no way to test the area of contact between the window sill, the outside side panel and the rubrail in accordance with the procedure of S6.

We are assuming these areas of contact do not constitute "body panel joints" and are, therefore, not subject to the requirements of FMVSS 221. Is this assumption correct?

29. Side panel to side panel. By the definition we understand the area of contact between the outside side panels to be "body panel joints", but two things are unclear. (1) Is our assumption correct that the area of contact below the floor line does not enclose the occupant space and is, therefore, not a "body panel joint"? (2) When this body panel joint is tested, should it be tested with all the members attached which include the rubrail, the two outside overlapping side panels and the body bow?

30. Aluminum trim to roof panel. The aluminum trim shown in the photograph and sectional diagram is used for appearance purposes only when transit type windows are ordered. Because the aluminum trim is added to the exterior skin of the body and does not serve to enclose the occupant space, we are assuming that the area of contact between the aluminum trim and the roof panels is not a "body panel joint" and is, therefore, not subject to the requirements of FMVSS 221. Is this assumption correct?

The following items are keyed to photograph #49, Blue Bird Conventional Front Section.

31. Fresh air intake. The fresh air intake which is shown in the photograph in our opinion constitutes a "maintenance access panel" and is, therefore, not a "body panel joint". Is this assumption correct?

32. Conventional switch panel. In our opinion this switch panels constitutes a "maintenance access panel" and is, therefore, not subject to the requirements of FMVSS 221. Is this assumption correct?

33. Conventional left hand heater to bow and cowl. In our opinion the panels and trim enclosing the heater cores and ducting shown in the photograph constitute "maintenance access panels" and are, therefore, not subject to the requirements of FMVSS 221. Is this assumption correct? photograph is covered with a rubber floor covering on a finished bus. In our opinion this panel constitutes a "maintenance access panel" to the transmission and linkage and wiring and is, therefore, not subject to the requirements of FMVSS 221. Is this assumption correct?

35. Dash covers and lower dash trim to belt bar. The end dash cover, the center dash cover and lower dash trim provide access to defroster ducting, instrumentation and wiring. In our opinion these constitute "maintenance access panels" and are, therefore, not subject to the requirements of FMVSS 221. Is this assumption correct?

36. Conventional transmission plate to floor. The transmission plate as shown in the photograph provides access to the transmission and linkage. In our opinion this constitutes a "maintenance access panel" and is, therefore, not subject to the requirements of FMVSS 221. Is this assumption correct?

37. Heater duct to floor and gusset. The photograph and sectional diagram show the heater duct which is designed for ventilation. It is, therefore, not to the requirements of FMVSS 221. Is this assumption correct?

38. Conventional right hand corner defroster and heater. In our opinion these panels are designed for ventilation purposes and provide maintenance access and, therefore, are not subject to the requirements of FMVSS 221. Is this assumption correct?

The following items are keyed to photograph #48, Blue Bird All American Front Section.

39. All American center grill access to radiator. In our opinion this panel is a "maintenance access panel" and is, therefore, not subject to the requirements of FMVSS 221. Is this assumption correct?

40. All American switch panel and stationary switch panel. In our opinion these are "maintenance access panels" and are, therefore, not subject to the requirements of FMVSS 221. Is this assumption correct?

41. Plastic dash to belt bar and angled dash trim to heater panel, All American. In our opinion these panels constitute "maintenance access panels" and are, therefore, not subject to the requirements of FMVSS 221. Is this assumption correct?

42. All American driver's floor board panels. In our opinion, these are "maintenance access panels" and are, therefore, not subject to the requirements of FMVSS 221. Is this assumption correct?

43. All American right hand heater. In our opinion these panels provide ventilation and access to the right hand front heater and are, therefore, not subject to the requirements of FMVSS 221. Is this assumption correct?

44. All American engine hood and ledge. In our opinion these components provide for maintenance access to the engine and are, therefore, not subject to the requirements of FMVSS 221. Is this assumption correct?

45. All American instrument panel. In our opinion this constitutes "a maintenance access panel" and is, therefore, not subject to the requirements of FMVSS 221. Is this assumption correct?

46. All American front access panel. In our opinion this constitutes a "maintenance access panel" and is, therefore, not subject to the requirements of FMVSS 221. Is this assumption correct?

The preamble to FMVSS 221, School Bus Body Joint Strength, as it appeared in the Federal Register dated January 27, 1976 said, "It is anticipated that this rule will burden manufacturers only to the extent of requiring the installation of more rivets than are currently used. The NHTSA has reviewed the economic and environmental impact of this proposal and determined that neither will be significant." In light of this, we are assuming that the NHTSA did not intend for major structural changes. We are certain that you understand that many of the areas discussed above would constitute major structural revisions if they were judged by you to be "body panel joints" which are subject to the requirements of FMVSS 221. Obviously, there is not time for such changes between now and October 26, 1976, the effective date for this standard.

We feel that to resolve each of the questions raised above, a meeting is required between NHTSA personnel and Blue Bird personnel. We are hereby requesting that such a meeting be held on February 24, 1976.

Thank you for your consideration of these requests and your early reply.

W. G. MILBY Staff Engineer

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