This SAE Recommended Practice (RP) provides test procedures for air braked trucks and truck-tractors used to tow single and multiple trailer combinations on highways. This RP is not intended for off-highway applications.
This document provides a method of determining the capability of towing trucks and truck-tractors to supply compressed air to the reservoirs and parking brake chambers on towed vehicles. This is a test procedure only and it does not have criteria for data comparison. Therefore, the usefulness of the procedure is to evaluate air system changes relative to each other. The test reservoir assembly is to simulate the supply system of a trailer. The 49 170 cm3 (3000 in3) reservoir is typical for four type 30 service chambers. The orifice in the line is to simulate the value through which the reservoir fills and the 9.84 mm (.3875 inch) diameter x 13.72 meters (45 feet) long tube is intended to duplicate the trailer supply line.