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Thank you, Randy, this is great background information. Much appreciated.
From: main@RealSTMFC.groups.io <main@RealSTMFC.groups.io> On Behalf Of Randy Hees
Sent: Saturday, June 13, 2020 8:05 PM
Subject: Re: [RealSTMFC] brakes
The original Westinghouse automatic brake valve was designated the "F" It was patented in 1872. It did not have "fast action". In general it was good for a train of 8-10 cars. The F valve did not meet the minimum standard (no valve did) at the first Burlington Air Brake trial in 1886, which used a 50 car train.. In response Westinghouse offered the "H" brake valve, which did have "fast action". In a fast action, the air brake valve not only applies air in response to dropping the air pressure in the train line, but also recognizes a rapid air pressure loss as an emergency, and in that case in addition to a maximum brake application the valve also vents the train line, reducing pressure in the train line. As a result the change in pressure is much more rapid, and the brakes apply much quicker.