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A SURVEY of recent developments in the field of air brakes is presented here. For instance, improved versions of the compressor, brake valve, relay emergency valve, and the hose coupling are described. The rotochamber, which is an improved type of brake chamber is covered, as well as a new, combined quick-release and limiting valve, and also the protection valve, which seals off the straight air and emergency trailer connection on the tractor, should the trailer break away. The author also emphasizes the importance of maintenance in keeping the brake system operating at top efficiency, for he believes that most of the chronic braking troubles being experienced today on heavy-duty vehicles could be eliminated if the brakes were analyzed and then subjected to a well-planned and executed periodic maintenance program.

THE principles of the basic air brake system for trucks, trailers, and buses are reviewed in this paper. The author emphasizes especially the dual-pressure and high-pressure systems, which are able to supply air not only to the brakes, but also to other power functions. Some additional applications are air suspension, air-powered steering, antiskid devices, transmission shifters, crane and shovel controls, and engine auxiliary controls such as air assist booster for clutch control.

“Zoning” a catalytic converter involves placing higher concentrations of platinum group metals (PGM) in the inlet portion of the substrate. This is done to optimize the cost-to-performance tradeoff by increasing the reaction rate at lower temperatures while minimizing PGM usage. A potentially useful application of catalyst zoning is to improve performance using a constant PGM mass. A study was performed to assess what the optimum ratio of front to rear palladium zone length is to achieve the highest performance in vehicle emission testing. Varying the zone ratio from 1:1 to 1:9 shows a clear hydrocarbon performance optimum at a 1:5.66 (15%/85%) split. This performance optimum shows as both a minimum in FTP75 non-methane organic gas (NMOG) emissions as well as a minimum in hydrocarbon, carbon monoxide, and nitrogen oxide light-off temperature. Overall, an improvement of 18%, or 11 mg/mi of combined NMOG+NOx emissions was obtained without using additional PGM.