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Someone replied to the thread: As some have guessed, the sanding systems were related to the braking, in particular to the wheel slide system. The Proceedings of the 1948 Annual Meeting of the Air Brake Association contain a paper entitled Decalostats and Decalostat Sanding by W. Frederick Klein, Project Engineer, New York Air Bake Co., which sheds quite a bit of light on the subject. The concept of local sanding on "trailers" first appears in a paper delivered at the ABA Annual Meeting of 1937, concerning Electro-Pneumatic Braking, also presented by a NYAB Engineer. From the 1948 paper it is clear the Burlington car system was connected to the protection valve of the Decalostat pneumatic anti-slide system. When a wheel slide was detected, the valve vented the cylinder pressure and it also applied sand as it restored the pressure, so that the wheel would not slip again. In the question and answer session, another gentleman describes the Great Northern's equipment, which utilized the American Brake Shoe Co. anti-slide system, which was an electrical unit that piloted magnet valves to vent the cylinder pressure and apply sand. There were even provisions for a system to determine car direction if that was considered necessary in the application, but the Cal Zephyr cars only had it on one end because they ran in a directional consist. In the 1949 Proceedings, Mr. C.L. Eksergian, The Executive Engineer and Assistant to the Vice President of the Budd Company presented a paper entitled "Wheel Slip and What Can Be Done About It". That paper also describes sanding as part of the means to improve adhesion during braking, and why it is only useful for disc brakes. The paper also discusses the packaging of the sand box inside the car to prevent freezing. In particular the author expresses appreciation to the staffs of the Burlington, Santa Fe, Milwaukee and Pennsylvania Railroads, who assisted in making tests. As for what caused the system's demise, a number of things more than likely related to maintenance did it in. First, Budd truss-side cars leak, it's a fact of life, which no doubt made keeping the sand dry as the car aged a difficult task. Dealing with a clogged sand box the side of a car must have been a real delight! All sanding systems are susceptible to moisture which clogs the traps, sanding that is not used for long periods of time becomes more susceptible to failing to function when it is needed. Imagine the world a sand trap and delivery hose under a car lived in, water form toilets and sinks, steam escaping from traps, snow and debris kicked up by the wheels...you get the picture. Lastly, the reason to have such wheel slide systems, brought on by the HSC Electro-pneumatic brake and the intention of the railroads to speed up their trains, had disappeared. By the 1950's the writing was on the wall for new high speed services, and the HSC brake system. The latter was hard to maintain with the technology it employed, and if you had one car in the train that did not have it, the entire train had to operate in the conventional pneumatic mode. So, one by one, the railroads dropped the HSC system and along with it the need for the local sanding. RDC cars continued to use the system because they were "locomotives" and required to have sand, but most operators abandoned the in-wall sand boxes for ones below the floor that could be pounded on to break up clogs, or easily removed for service. I lived though that first hand in my railroad mechanical job, where our RDC's and our Push-Pull Cab Cars all had external sand boxes below the floor for that very reason. At 02:35 PM 7/1/2013, you wrote: On Train Orders, there is a thread related to the Sand Traps on the __._,_.___
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