DISCUSSION OF REPORT OF COMMITTEE ON ECONOMIC THEORY OF HIGHWAY IMPROVEMENT

THE PAPER ON TIRE WEAR INVESTIGATION IS DISCUSSED. THE BUREAU OF STANDARDS HAS NO INFORMATION ON THE EFFECT OF TEMPERATURE ON THE ABRASIVE RESISTANCE OF TREAD RUBBERS, BUT THE FACT THAT HIGH TEMPERATURES HAVE A DETERIORATING ACTION IS WELL ESTABLISHED. THE INCREASE IN TIRE COSTS DURING THE SUMMER MONTHS IS PROBABLE DUE LARGELY TO THE DETERIORATION OF THE TIRES AS A WHOLE RATHER THAN TO A DECREASE IN THE ABRASIVE RESISTANCE OF THE TREAD RUBBER. THE AUTHOR REFERS TO THE LOW TIRE MILEAGE OBTAINED BY A CERTAIN BUS LINE WHICH DURING ITS COURSE DESCENDED A LONG STEEP GRADE. IT WOULD APPEAR FROM THE CONDITIONS STATED THAT THIS MIGHT BE DUE TO HIGH ABRASIVE WEAR CAUSED BY THE TANGENTIAL SHEAR ON THE TREAD RATHER THAN TO THE HEAT GENERATED AT THE BRAKE DRUM. THE FAILURES OF TIRES IN HOT DESERT REGIONS, ON THE OTHER HAND, ARE PROBABLY DUE TO DETERIORATION INTERNALLY FROM HIGH TEMPERATURE. RURAL TESTS HAVE SHOWN THAT THE ROLLING RESISTANCE OF DIFFERENT SIZES OF TIRES PER TON LOAD ARE ABOUT THE SAME. HOWEVER, OVERLOADED TIRES WILL HAVE A COMPARATIVELY SHORTER LIFE DUE TO DETERIORATION BOTH INTERNALLY AND EXTERNALLY. THE KANSAS STUDY ON TIRE WEAR INVESTIGATION MAKES TEMPERATURE CORRECTIONS WHICH SEEM SURPRISINGLY LARGE. HOWEVER THERE IS A WIDE VARIATION IN THE MANNER IN WHICH THE TREAD WEARS IN DIFFERENT SIZES AND TYPES OF BALLOON TIRES. THE FORMULA USED BY THE NORTH CAROLINA TEST FOR AIR RESISTANCE IS QUESTIONED. THE BUREAU'S INVESTIGATION OF THE ROLLING RESISTANCE OF TIRES AGREES WITH THE AUTHOR'S DETERMINATIONS. PROBLEMS IN CONNECTION WITH THE AIR RESISTANCE OF AUTOMOBILES ARE DISCUSSED. AN AVERAGE RESISTANCE CURVE IS OF DOUBTFUL UTILITY SINCE DEVIATIONS OF AS MUCH AS TWENTY PER CENT FROM THE AVERAGE ARE NOT UNCOMMON. IN TESTS MADE BY MEANS OF MOUNTING A FULL SCALE AUTOMOBILE ON A FLAT CAR THE EFFECT OF THE AIR FLOW AROUND THE FLAT CAR INTRODUCES A SOURCE OF UNCERTAINTY. IT IS FELT THAT AIR FORCE ON AN AUTOMOBILE CAN BE FOUND MORE CONVENIENTLY, QUICKLY, AND ACCURATELY BY WIND TUNNEL TESTS ON A MODEL. REFERENCES: REPORT OF COMMITTEE ON ECONOMIC THEORY OF HIGHWAY IMPROVEMENT, T. R. AGG, HIGHWAY RESEARCH BOARD PROCEEDINGS, VOL 6, PP 45-88, 1927.

  • Supplemental Notes:
    • Vol 6, pp 89-92
  • Authors:
    • Holt, W L
    • Wormeley, P L
  • Publication Date: 1927

Media Info

  • Monograph Title: Proceedings of the Sixth Annual Meeting of the Highway Research Board Held at Washington, D.C., December 2-3, 1926
  • Serial:

Subject/Index Terms

Filing Info

  • Accession Number: 00223284
  • Record Type: Publication
  • Files: TRIS, TRB
  • Created Date: Jun 11 1971 12:00AM