Interpretation ID: 86-1.27
TYPE: INTERPRETATION-NHTSA
DATE: 02/10/86
FROM: AUTHOR UNAVAILABLE; Erika Z. Jones; NHTSA
TO: M. Iwase -- Manager, Technical Administration Dept., Koito Mfg. Co. Ltd.
TITLE: FMVSS INTERPRETATION
TEXT:
Mr. M. Iwase Manager, Technical Administration Dept. Koito Mfg. Co. Ltd. Shizuoka Works 500 Kitawaki Shimizu-shi, Shizuoka-ken JAPAN
This is in reply to your letter of August 30, 1985, to Jere Medlin, Office of Rulemaking, asking for an interpretation of the recent amendment to Motor Vehicle Safety Standard No. 108 allowing motorcycles to be equipped with modulating headlamp systems.
In your first question, you asked for confirmation of your understanding of the modulation cycle and maximum power. We confirm that your interpretation is correct. Please note that the value of A on the modulation cycle of your diagram may be equal to or less than the value of D. However, the requirement relates to C/D rather than C/A, and it is the value of C/D that must be at least 0.17.
With reference to the electrical wiring diagram that you provided, you have asked whether the voltage drop maximum of 0.45 volt in S4.6.1(g) applies to condition (a) (when the modulator switch is "on") or condition (b) (when the modulator switch is "off"). The maximum voltage drop applies to both conditions (a) and (b), i.e., when the modulator is operating and when the headlamp is on. Paragraph S4.6.1(g) states "When tested in accordance with the test profile shown in Figure 9, the voltage drop across the modulator when the lamp is on at all test conditions ....shall not be greater than .45 volt." This not only includes the period of time when the modulator is operating, but also the period when the headlamp is on without the modulator. Paragraph S4.6.1(e) requires that both the upper and lower beams remain operable in the event of a modulator failure, and thus the agency views headlamp operation without modulator as one of the test conditions included in the term "test conditions" in S4.6.1(g). We would like to comment further that when the modulator is turned on, during the test profile of Figure 9, it should be activated when the headlamp is on, since most manufacturers of motorcycles wire their vehicles so that the headlamp is on when the ignition switch is on.
Your next question concerns the acceptability of three types of modulator switch systems which you have diagrammed. All your designs appear consistent with the requirements of Standard No. 108. The modulator must be capable of being switched out of the circuit if it fails, in which case upper and lower beams could be used im a steady-burning mode. This does not necessarily mean another switch, other than the Hi-low beam switch, however.
In response to your final question, you may write Herbert Thrower, Jr., President, Dotech Inc., P.O. Box 3322, Charlotte, N.C. 28210.
Sincerely,
Erika Z. Jones Chief Counsel
SUBJECT: ACTION: Request for Interpretation of Motorcycle Modulating Headlamp Requirements (FMVSS No. 108) by Koito
FROM: Barry Felrice Associate Administrator for Rulemaking
TO: Jeffrey Miller Chief Counsel
Rulemaking received the attached request for an engineering interpretation of the intent of certain requirements for motorcycle headlamp modulators.
Herein is the engineering interpretation of the requirements in question. Please prepare the official response to Koito based on this information.
In response to question 1:
1. Yes, 0.21 < y < 0.30 sec., as suggested by koito, is correct.
2. Yes, x/y = 50 to 70%, as suggested by Koito, is correct.
3. The value of A may be equal to or less than the value of D. However, the requirement relates to C/D rather than C/A. It is the value of C/O that must be at least 0.17.
In response to question 2:
The intent of the requirement in S4.6.1 is to assure that less than 0.45 volts is lost as a result of the addition to a headlamp circuit for the purpose of modulating the headlamp. The 0.45 volts is for night operation condition of the headlamp (i.e. condition "b" in Koito's letter).
In response to question 3.
We do not approve designs, but offer the following comments on the intent of the rule. The modulator should be capable of being switched out of the circuit if it fails, in which case upper and lower beams could be used in a steady burning mode. This does not necessarily mean another switch, other than the Hi-low beam switch, however. All your designs appear to be consistent with the requirements of the standard, however some appear more desirable, based on number of switches, case of use, etc., than others.
In response to your request for the address of Dotech, a modulator manufacturer, the following information is furnished:
Mr. Herbert Thrower, Jr.. President Dotech Inc. P.O. Box 3322 306 Clanton Road Charlotte, N.C. 28210 Tel. No. (704) 523-6727
Attachment