Can someone tell me when the change, for new freight cars, from H valves to K valves would have occured?

Thanks,
David Johnston

Since no one more knowledgeable has responded, may I suggest that it was about 1905 when the K triple came out. At some point I seem to remember going through several old air brake catechisms I have and found the that the copyright dates on the books first showing the K were '05. I could be wrong. Anyway if this is correct then I expect that some freight cars beginning that year could have begun to use K's as stocks of H valves were used up. As you probably know Westinghouse offered the service of rebuilding H valves into K valves, the H valves being sent in to the factory in Wilmerding, Pa. or to the Westinghouse Pacific Coast Brake Co. of Emeryville, Ca.

Just for kicks I did a google search. I found that the patent for the k valve was applied for on Jan 15, 1904, with the patent issued Feb. 16 1909. Some litigation appeared to have occurred with NYAB. Perhaps other than in testing, 1909 would be a better date to assume as the beginning of widespread use of K's on new cars.

Thanks for the information. The car we are looking at restoring was built in 1912, so it must have been a "K" valve by then.