Interpretation ID: 3261o
Volvo Cars of North America
Rockleigh, NJ 07647
Dear Mr. Shapiro:
This responds to your letter concerning the testing of hydraulic brake hose assemblies to the whip resistance requirement (S5.3.3) of Standard No. 106, Brake Hoses. I regret the delay in responding.
Your question relates to Table II of Standard No. 106, which specifies the amount of slack that should be introduced when mounting brake hose assemblies on the whip test apparatus. (The amount of the hose indicated as "slack" in Table II is the difference between the projected length of the hose assembly (when mounted in the whip test machine) and the free length of the hose while maintained in a straight position.) Slack must be present in the hose when mounted on the whip test machine to enable the proper "whipping" movement of a brake hose assembly. Without slack, an assembly would probably be incapable of withstanding any rotation of the movable header of the whip test apparatus described in Standard No. 106 without rupturing.
Table II specifies the amount of slack for some sizes of assemblies, and not for others. You ask whether a hydraulic brake hose assembly of a size falling in the latter category--viz., an assembly comprised of a brake hose that is 19 to 24 inches in free length, and which is more than one-eighth inch or three millimeters (mm.) in diameter--"need not be tested to meet or exceed the whip resistance requirement" of the standard.
With regard to NHTSA's Standard No. 106 compliance testing, your understanding is correct that Table II does not specify the amount of slack for testing assemblies of the size you describe. Due to the absence of the slack specification, NHTSA does not require testing of such assemblies to the whip resistance requirements of the standard.
With regard to your certification that the brake hose assemblies you manufacture comply with all applicable requirements of Standard No. 106, you are correct that hydraulic brake hose assemblies of the size you describe are not subject to the whip resistance requirements. However, the agency urges manufacturers to ensure that these assemblies perform in a safe manner while subject to environmental conditions of vehicle operations which may result in flexing of the brake hose or brake hose assembly.
Please contact my office if you have further questions.
Sincerely,
Erika Z. Jones Chief Counsel
ref:106 d:l2/9/88