Interpretation ID: nht75-1.31
DATE: 06/10/75
FROM: AUTHOR UNAVAILABLE; R. L. Carter; NHTSA
TO: Mercedes-Benz
TITLE: FMVSS INTERPRETATION
TEXT: Please forgive the delay in responding to your letter of December 12, 1974, requesting an interpretation of the definition of "permanently attached end fitting" appearing in Federal Motor Vehicle Safety Standard No. 106-74, Brake Hoses.
You have described a process of heat shrinking plastic vacuum booster hose over short corrugated metal connecting tubes, the ends of which are flared to retain threaded hex fittings. You have submitted sample hose assemblies and requested confirmation of your interpretation that the end fittings are permanently attached. While these fittings may meet the common understanding of the words "permanently attached," Standard No. 106-74 defines "Permanently attached end fitting" as:
an end fitting that is attached by deformation of the fitting about the hose by crimping or swaging, or an end fitting that is attached by use of a sacrificial sleeve or ferrule that requires replacement each time a hose assembly is rebuilt.
Deformation of the hose about the fitting by heat shrinking is not "deformation of the fitting about the hose by crimping or swaging." The latter part of the definition is inapplicable because the assemblies are not subject to being rebuilt. Therefore, to classify these end fittings as permanently attached would require an amendment of the standard. Such an amendment is being considered.
Your January 7, 1975, petition for reconsideration, requesting exclusion of the above described vacuum hose from the coverage of Standard No. 106-74, was received more than 30 days after the most recent amendment of the definition of "brake hose". Therefore, it has been treated as a petition for rulemaking. The Standard defines "brake hose" as:
a flexible conduit manufactured for use in a brake system to transmit or contain the fluid pressure or vacuum used to apply force to a vehicle's brakes.
The conduit between the vacuum booster and vacuum pump in your brake booster circuit clearly falls within this definition, and hence is subject to the Standard's requirements. The NHTSA has concluded that, because of its flexibility, this hose is exposed to the same hazards as the more traditional types of vacuum brake hose and so should be subject to the same performance requirements. Accordingly, your petition to amend the definition is denied. The conduit between the vacuum pump and the intake manifold, however, falls outside the definition of "brake hose" because, as described by Mr. Craig Jones in a conversation with Mr. Howard Dugoff of this agency on March 17, 1975, the booster system produces full vacuum even when this conduit fails. Therefore, this conduit need not comply with the requirements of Standard No. 106-74.
Sincerely,
ATTACH.
MERCEDES-BENZ OF NORTH AMERICA, INC.
December 12, 1974
Office of Chief Counsel National Highway Traffic Safety Administration
Subject: Brake Hoses
Gentlemen:
Federal Motor Vehicle Safety Standard 106; Brake Hoses, defines under Section S4 a "permanently attached end fitting" as being a fitting that is attached by deformation of the fitting about the hose by crimping or swaging or an end fitting that is attached by use of a sacrificial sleeve or ferrule that requires replacement each time a hose assembly is rebuilt.
Vacuum booster circuit conduit can be constructed with materials and techniques so as to satisfy, what we believe to be, the intent of this definition. Specifically, thermoset plastic materials can be heat shrunk over corrugated connections at end fittings and mid-circuit devices such as check valves. Additionally, threaded hex fittings can be secured to metal end pipes by means of flaring. These construction techniques not only provide satisfactory performance but result in an assembly that cannot be disassembled without the disstruction of one or all of the various components. Examples of these construction techniques have been forwarded to the Docket Room.
These assemblies as used on Mercedes-Benz vehicles are completely and finally assembled by our suppliers. Installation of these assemblies into our vehicles entails only the threading of the fittings into the various parts of the vacuum cricuit. There is no final construction of these hose assemblies in our manufacturing facilities. Additionally, these assemblies are offered for spare parts usage only as complete assemblies.
We hereby request clarification as to whether or not this type of vacuum conduit assembly construction satisfies the intent of the definition of permanently attached end fittings as used in this Standard and thereby permit banded identification of the complete assembly rather than a separate identification of each component.
Should you require additional information or material to clarify this request, do not hesitate in contacting this office.
Very truly yours,
Heinz W. Gerth Assistant Vice President Engineering
MERCEDES-BENZ OF NORTH AMERICA, INC.
January 7, 1975
Office of The Chief Council National Highway Traffic Safety Administration Subject: Petition for Reconsideration FMVSS 106, Brake Hose
Gentlemen:
Pursuant to discussions with Mr. Driver in Washington on July 26, 1974 and with Mr. Dugoff on November 4, 1974 during his visit to Germany, we would like to restate our position that the flexible vacuum conduit used in Mercedes-Benz passenger vehicles in the brake boost circuit does not fall within the definition of brake hose as outlined in Standard 106.
While this particular conduit may not satisfy the hose flexibility requirements of paragraphs S9.2.2, S9.2.3, S9.2.7 and S9.2.10, it does offer the important advantages of being resistant to high temperature and ageing.
Additionally, the installation in Mercedes-Benz vehicles is such that it is subject to very little vibration between the intake manifold and booster. The material was specifically chosen because its limited flexibility permits safer, simpler installation requiring fewer mounting brackets. The complete assembly, when installed, is still sufficiently rigid so as to prevent any abrasion, and in appearance is similar to tubing so that a mechanic will not be tempted to push it aside to gain more workspace.
A sample of this assembly has been forwarded to the Docket Section for review. Should you request additional material or information for this Petition for Reconsideration, please do not hesitate in contacting this office.
Very truly yours,
Heinz W. Gerth Assistant Vice President Engineering