LONGER COMBINATION TRUCKS - BOTH DOUBLES AND TRIPLES - MEET PRESENT BRAKING RULES

A LARGE COOPERATIVE BRAKE TEST PROGRAM WAS CONDUCTED ON DOUBLES, A TRACTOR AND TWO 27-FT. OR 40-FT. TRAILERS, AND TRIPLES, A TRACTOR AND THREE 27-FT. TRAILERS. THE TESTS INDICATE THAT THESE LARGE COMBINATION TRUCKS HANDLE AS WELL AS STANDARD HEAVY-DUTY VEHICLES IN SERVICE AND EMERGENCY BRAKING. TEST RESULTS SHOW SPECIFICALLY THAT: (1) THEY HAVE STOPPING DISTANCES COMPARABLE TO THOSE OF SHORTER COMBINATIONS, (2) THEY SHOW IMPROVED BRAKING WHEN BRAKE SYSTEM PLUMBING IS MODIFIED TO SPEED UP AIR TRANSMISSION, (3) THEY ARE STABLE DURING LOCKED WHEEL STOPS, AND (4) THEY DO NOT SUFFER EXCESSIVE LOADS ON THE CONNECTIONS DURING EITHER ACCELERATION OR DECELERATION. STOPPING DISTANCES OF VARIOUS COMBINATIONS WITH SERVICE BRAKES ON DRY AND WET PAVEMENTS ARE PRESENTED IN FIGURES. METHODS OF IMPROVING VEHICLE DIRECTIONAL STABILITY DURING BRAKING ARE: (1) POSITIONING HEAVILY LOADED TRAILERS AHEAD OF LIGHTER UNITS, (2) TORQUE BALANCING THE BRAKES UNTIL ALL ARE EQUALLY EFFECTIVE, THUS REDUCING THE TENDENCY TO SKID INDIVIDUAL TIRES, AND (3) FITTING A LIMITING VALVE TO CONTROL AIR PRESSURE TO THE FRONT BRAKES. FIVE COMBINATIONS WERE TESTED FOR STRUCTURAL INTEGRITY DURING BRAKING. RAPID BRAKE MODULATION WAS SHOWN TO PERMIT A MORE STABLE AND SAFER STOP.

• Supplemental Notes:
  • Vol 77, No 9, PP 68-72, 4 FIG, 3 TAB
• Authors:
  • Nelson, R E
  • FITCH, J W
  • Kaye, M C
• Publication Date: 1969-9

Media Info

• Serial:
  • SAE Journal of Automotive Engineering
  • Publisher: Society of Automotive Engineers

Subject/Index Terms

• TRT Terms: Air brakes; Brakes; Braking; Deceleration; Modulation; Stability (Mechanics); Stopping distances; Testing; Tractor trailer combinations
• Old TRIS Terms: Modulation
• Subject Areas: Highways; Motor Carriers; Safety and Human Factors; Vehicles and Equipment;

Filing Info

• Accession Number: 00223041
• Record Type: Publication
• Files: TRIS
• Created Date: Oct 13 1994 12:00AM