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CONTROLLING HEAD-LAMP AIM

THE RESULTS OF PASSENGER VEHICLE INSPECTION IN CALIFORNIA AND EXAMINATION OF A 20-VEHICLE TEST SAMPLE INDICATE THAT PERHAPS ONE-THIRD TO ONE-HALF OF THE HEAD LAMPS IN ALL VEHICLES ARE MISAIMED. RESULTS OBTAINED FOR THE SAMPLE OF 70 SEALED-BEAM HEAD LAMPS OF THE VARIOUS TYPES IN COMMON USE SHOW THAT, WHEN CORRECTLY AIMED EXISTING LAMPS WERE SIMPLY REPLACED BY OTHER UNITS, NEARLY HALF OF THE NEWLY INSTALLED HEAD LAMPS FAILED TO MEET THE SAE AIM REQUIREMENTS. AFTER 90 DAYS OF NORMAL SERVICE ON THE TEST VEHICLES, INVOLVING AN AVERAGE MILEAGE PER VEHICLE OF 12,762 MILES, ABOUT HALF OF THE LAMPS-ALL OF WHICH BEGAN THE TEST PERIOD IN CORRECT ADJUSTMENT- NO LONGER MET THE SPECIFIED AIM REQUIREMENTS. A GENERAL SURVEY OF HEAD-LAMP HOUSINGS REVEALED A NUMBER OF DESIGN AND CONSTRUCTION FEATURES THAT APPEAR TO BE ENDOWED WITH AN INHERENT INSTABILITY AND THUS PROBABLY CONTRIBUTE MATERIALLY TO THE PROBLEMS OF CONTROLLING HEAD-LAMP AIM. PHOTOMETRIC TESTS WERE PERFORMED IN ACCORDANCE WITH SAE SPECIFICATIONS FOR EACH OF 165 SEALED-BEAM HEAD-LAMP UNITS PURCHASED ON THE OPEN MARKET IN NORTHERN CALIFORNIA. OF THE ENTIRE TEST SAMPLE, 64 PERCENT FAILED TO MEET THE PHOTOMETRIC REQUIREMENTS SPECIFIED. OF THOSE THAT FAILED, HOWEVER, ABOUT TWO-THIRDS COULD MEET THE PHOTOMETRIC REQUIREMENTS IF THE AIMING PLANE WERE SHIFTED TO SOME POSITION OTHER THAN THAT SPECIFIED FOR THE TEST. THIS INDICATES THAT THE AIMING PLANE, AS DETERMINED BY THE AIMING PADS ON THE SEALED-BEAM UNIT, IS IN MANY CASES NOT BEING ESTABLISHED WITH SUFFICIENT ACCURACY IN PRODUCTION, AND AS A CONSEQUENCE EVEN A CORRECTLY AIMED HEAD LAMP ON A VEHICLE MAY NOT PRODUCE AN ACCEPTABLE BEAM PATTERN ON THE ROADWAY. /AUTHOR/

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  • Supplemental Notes:
    • Sponsored by Committee on Visibility and presented at the 50th Annual Meeting. Distribution, posting, or copying of this PDF is strictly prohibited without written permission of the Transportation Research Board of the National Academy of Sciences. Unless otherwise indicated, all materials in this PDF are copyrighted by the National Academy of Sciences. Copyright © National Academy of Sciences. All rights reserved.
  • Authors:
    • FINCH, D M
  • Publication Date: 1971

Media Info

  • Media Type: Digital/other
  • Features: Figures; References; Tables;
  • Pagination: p. 32-39
  • Monograph Title: Visibility
  • Serial:

Subject/Index Terms

Filing Info

  • Accession Number: 00221656
  • Record Type: Publication
  • ISBN: 0309019923
  • Report/Paper Numbers: HS-011 999
  • Files: TRIS, TRB
  • Created Date: May 22 1972 12:00AM