MEASURING THE FOOTPRINT OF A TIRE

A TIRE FOORTRPINT MEASURING DEVICE WAS DEVELOPED BY THE OFFICE OF VEHICLE SAFETY WORK AT THE NATIONAL BUREAU OF STANDARDS. THE DEVICE CONSISTS ESSENTIALLY OF A PLAIN SOURCE OF LIGHT OF UNIFORM INTENSITY, A GLASS PLATE ON WHICH THE TIRE PRINT IS PLACED, AND AN OPTICAL SYSTEM FOCUSING THE LIGHT PASSING THROUGH THE PLATE ON A PHOTOSENSITIVE DEVICE. A SILICON SOLAR CELL IS USED AS THE PHOTODETECTOR. TIRE FOOTPRINTS ARE OBTAINED BY INFLATING THE MOUNTED TIRE TO THE DESIRED PRESSURE, PLACING THE WHEEL ON A SPECIAL HYDRAULIC PRESS, INKING THE PORTION TO MAKE CONTACT, AND PLACING AN ACETATE SHEET BETWEEN THE INKED TREAD AND THE OPPOSING SURFACE REPRESENTING THE ROAD. WHEN ACTIVATED, THE PRESS CLOSES SLOWLY UNTIL IT REACHES THE PRESET PRESSURE AND OPENS UP AGAIN. THE ACETATE SHEET BEARING THE TIRE FOOTPRINT IS REMOVED AND DRIED. THE FOOTPRINT ON THE ACETATE CAN BE THEN BE PLACED IN THE OPTICAL INTEGRATOR FOR MEASUREMENT. THESE TIRE FOOTPRINT AREA MEASUREMENTS ARE MORE ACCURATE THAN APPRAISALS BY OTHER MEANS. REPEATABILITY IS EXCELLENT AND SUCCESSIVE MEASUREMENTS OF A TREAD YIELD A STANDARD DEVIATION OF 0.1 SQ. INCH FOR THE SAME LOADING AND INFLATION.

• Supplemental Notes:
  • Vol 54, No 6, PP 128-129, 1 FIG, 2 PHOT
• Corporate Authors:

  National Bureau of Standards

  Department of Commerce, Office of Technical Publications
  Washington, DC  United States  20234
• Publication Date: 1970-6

Media Info

• Serial:
  • Dimensions NBS

Subject/Index Terms

• TRT Terms: Detectors; Inflation; Loads; Measuring instruments; Optical measurement; Silicon; Tires
• Uncontrolled Terms: Contact area; Loading
• Subject Areas: Geotechnology; Highways; Materials; Safety and Human Factors; Vehicles and Equipment;

Filing Info

• Accession Number: 00223294
• Record Type: Publication
• Files: TRIS
• Created Date: Aug 26 1970 12:00AM