Interpretation ID: nht76-1.14

DATE: 10/26/76

FROM: AUTHOR UNAVAILABLE; F. Berndt; NHTSA

TO: Toyoda Gosei Co., Ltd.

TITLE: FMVSS INTERPRETATION

TEXT: This is in belated response to your April 9, 1976, letter concerning the application of Federal Motor Vehicle Safety Standard No. 106-74, Brake Hoses, to certain combination hydraulic brake hose assemblies.

Figure 3 of your letter depicts two typical brake hose assemblies that are connected end-to-end. Figure 4 depicts the intended installation of such a pair of assemblies, with the joined fittings meeting at a bracket that is attached to a shock absorber. Figures 1 and 2 show two designs to simplify the structure at this juncture.

Treating these figures in reverse order, the "B type" design shown in Figure 2 is similar to the pair of assemblies shown in Figure 3, except that the pair of joined end fittings is replaced with a single center fitting. The National Highway Traffic Safety Administration (NHTSA) considers such a construction to be two distinct brake hose assemblies, which would be tested separately for compliance with Standard No. 106-74. The center fitting would simply be considered an end fitting for each of these assemblies.

The "A type" design shown in Figure 1 would be treated differently, however. In this design, the two separate pieces of hose are replaced by a single piece that runs the full length between the outermost end fittings. In place of joined fittings as in Figure 3 or a center fitting as in Figure 2, this hose would be surrounded by molded rubber and a metal ring. The ring would be mounted in the bracket that is attached to the shock absorber. The NHTSA considers this construction to be a single brake hose assembly, and testing for compliance with Standard No. 106-74 would be conducted accordingly. For example, the tensile strength test would be performed by pulling, at the outermost fittings, on the full length of the hose. However, this interpretation would not require the assembly to be capable of meeting the whip resistance requirement of S5.3.3 with the full length subject to flex. The NHTSA considers such a brake hose assembly to have two distinct "free lengths" -- one on either side of the center metal ring. Therefore, the whip resistance test would be performed separately on each of these portions. In other words, the metal ring would be treated as an "end fitting," for the purposes of the whip resistance test described in S6.3.

Sincerely,

ATTACH.

TOYODA GOSEI CO., LTD.

April 9, 1975

Richard B. Dyson -- Acting Chief Counsel, National Highway Traffic Safety Administration Dear Mr. Dyson

We want to obtain an approval for the two types of hydrauric brake hose assemblies as shown in the attached Fig. 1 and Fig. 2. Please tell us how to obtain the approval.

Sometimes we have to fix an intermediate point of hose assembly to prevent it from being in touch with any part of motor vehicle as shown in Fig. 4. Currently, in this case, we joint No. 1 hose assembly with No. 2 hose assembly as shown in Fig. 3 and use the joined hose, which we call "joint hose assembly". For example, its jointed fitting is fixed on the frange of a shock absorber as shown in Fig. 4.

We obtain the approval for each No. 1 hose assembly and No. 2 hose assembly when they are used as joint hose assembly. When we use A type and B type hose assemblies which are shown in Fig. 1 and Fig. 2 respectively, how can we obtain their approvals.

1. Explanation of A and B type hose assembly

a) A type hose assembly

This hose assembly has the part which is constructed with insert metal ring and molded rubber as shown in Fig

b) B type hose assembly

This hose assembly has the integrated "center fitting" as shown in Fig. 3.

2. Questions

Please answer the following questions.

a) About A type hose assembly

Can we use A type hose assembly from which the metal ring and molded rubber are taken off when we estimate its performance?

b) About B type hose assembly

1) Should we regard that this is composed of two hose assemblies and estimate their performances separately?

2) Or should we test it as one hose assembly?

In the latter case, how should we practice the following performance tests?

1; Constriction

* Can we test the constriction of the center fitting by using a long gauge plug as shown in Fig. 5?

2; Free length * Should we regard the sum of free length of the two parts as that of the B-type hose assembly? (That is, L[1] + L[2] in Fig. 2)

3; Whip test

* Should we test it using a special jig as shown in Fig. 6?

* Should we test B type hose assembly in the same method as usual hose assembly is tested as shown in Fig. 7? In this case we can not proof the required whip performance for this type hose.

* Or can we regard the whip performance of usual hose assembly, whose free length is equal to L in Fig. 2 as that of B type hose assembly? (cf. Fig. 8)

4; Tensile test

* Should we determine the tensile strength of the two parts separately as shown in Fig. 9?

* Or can we test it as the usual hose assembly with only two end fittings as shown in Fig. 10?

Your kind reply will be appriciated

Very truely yours,

Katsuhiko Yokoi -- Chief staff Ist. Product Development Sect

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