Re: brakes

Schuyler Larrabee

Thank you, Randy, this is great background information.  Much appreciated.





From: <> 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.

The "K" valve was introduced in 1906/07 as an improved "H" valve.  They used the same mounting flange (to the brake reservoir if a "HC" or "KC" ("F" used a different flange) Externally the only difference between a "H" and "K" was an added flange on the valve body casting.  Westinghouse offered a kit to convert a "H" to a "K".  That kit included a sheet metal flange to be added to the valve body to give the "H" valve the same silhouette as a "K".

On the D&RG(W) "F" valves were used on tenders until the end of operation.  Most passenger cars on the D&RG(W) had "F" valves, and they are in use on the C&TS historic cars.  The D&RG freight car order of 1903 (3000 class box cars, 30' stock cars, & drop bottom gons all had "H" valves, all of which were converted to "K" with the added sheet metal flange.

Randy Hees

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