Interpretation ID: 7307-2
Manager, Specifications
Indiana Mills & Manufacturing, Inc.
18881 U.S. 31 North
P.O. Box 408
Westfield, Indiana 46074-0408
Dear Mr. Lawler:
This responds to your letter of May 18, 1992, concerning the test requirements of Standard No. 210, Seat Belt Assembly Anchorages. Your questions concern a final rule published on December 5, 1991 (56 FR 63682) clarifying the definition of "seat belt anchorage." That final rule had the effect of requiring seat belt attachment hardware, which previously was not included within the definition of "seat belt anchorage," to comply with the requirements of Standard No. 210. Your five questions are addressed below.
The first three questions refer to a safety belt design which incorporates a retractor.
l. If a test harness is used, can one end of the harness be attached to the attachment hardware (retractor frame), or must it be attached to the retractor spool?
The use of test harnesses for Standard No. 210 testing was permitted in a final rule published April 30, 1990, and effective September 1, 1992. More specifically, the final rule specified that "material whose breaking strength is equal to or greater than the breaking strength of the webbing for the seat belt assembly installed as original equipment" be used to transfer the test loads from the body block to the anchorages during the Standard No. 210 compliance tests. The amended standard also specifies that the attachment of this material should "duplicate the geometry" of the original webbing.
The amended definition of "seat belt anchorage" explicitly states that the seat belt anchorage is
any component, other than the webbing or straps, involved in transferring seat belt loads to the vehicle structure, including, but not limited to, the attachment hardware, seat frames, seat pedestals, the vehicle structure itself, and any part of the vehicle whose failure causes separation of the belt from the vehicle structure.
If the retractor spool breaks during a crash, the safety belt will not remain attached to the vehicle. Therefore, the retractor spool is a part of the vehicle whose failure causes separation of the belt from the vehicle structure, and, under the definition set forth above, is part of the seat belt anchorage. If a test harness is used, it must be attached such that the retractor spool is tested as part of the seat belt anchorage. The harness may not be attached directly to the retractor frame, since the retractor spool would not be tested in that instance.
2. If the harness must be attached to the spool, may it be attached around the spool as opposed to being inserted into the spool?
As stated previously, Standard No. 210 specifies use of "material whose breaking strength is equal to or greater than the breaking strength of the webbing for the seat belt assembly installed as original equipment" for Standard No. 210 tests. For compliance tests, NHTSA's preference is to use the original safety belt webbing whenever possible. When this cannot be done, due to elongation or breakage of the original webbing, NHTSA's first choice is to attach substitute webbing or other material to the original webbing near the anchorage. If the substitute material cannot be attached to the original webbing, NHTSA would attach the substitute webbing directly to the retractor spool. If the substitute webbing cannot be inserted into the spool in the same manner as the original webbing, attaching the substitute webbing around the spool would most closely duplicate the geometry of the original webbing.
3. We assume it is the intent of the agency to test only the strength of the attachment hardware--not the locking mechanism of the retractor built in accordance with FMVSS 209.
The strength requirement in S4.2 of Standard No. 210 specifies that anchorages must withstand certain forces when tested under specified conditions. Under S4.2.3, permanent deformation or rupture of a seat belt anchorage or its surrounding area is not considered to be a failure, if the required force is sustained for the specified time. If breakage of the locking mechanism (a part of the anchorage because it is "involved in transferring seat belt loads to the vehicle structure") caused separation of the belt from the vehicle structure, such breakage would be a failure of the Standard No. 210 test, as the anchorage would not have withstood the test forces. However, if the locking mechanism broke or released during the test without allowing the webbing to separate from the vehicle structure, the agency would not consider it a failure of the strength requirement test, since the belt would still be anchored to the vehicle structure.
4. A commonly used design is the "cable buckle". The buckle assembly is positioned in convenient reach of the seat occupant by attaching the buckle to a cable by a method called swaging. The attachment hardware consists of a flat end containing a hole for an attaching bolt and a ferrule which is swaged to the cable. The ferrule and the flat end are made in one piece. Please confirm that the attachment ferrule bolted to the seat/vehicle is what is required to withstand the forces dictated by FMVSS 210; separation of the cable from the ferrule would not constitute malfunction of the test harness and not non-compliance to FMVSS 210.
In the December 5, 1991 final rule, the agency stated that "the definition of seat belt anchorage included only the attachment points of the seat belt, and not the webbing, straps, or similar device, or the buckles which comprise the seat belt itself." For this design, the cable is a "similar device" to seat belt webbing, and would be considered part of the seat belt, not the anchorage. If the cable broke, the agency would consider that an incomplete test, just like breakage of webbing. However, it would be a failure of the Standard No. 210 test if the cable pulled out of the ferrule, since such pulling out would result from a failure of the ferrule rather than a broken cable.
5. Please confirm that the test harness could delete the buckle mechanism and attach directly to the upper end of the cable in the cable/ferrule assembly.
The answer to this question is yes. As stated previously, buckles are part of the seat belt, not the anchorage, and therefore, are not subject to the strength requirement of Standard No. 210.
I hope you find this information helpful. If you have any other questions, please contact Mary Versailles of my staff at this address or by phone at (202) 366-2992.
Sincerely,
Paul Jackson Rice Chief Counsel ref:210 d:7/23/92