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I speculate that official rules called for tying down all hand brake on set out cars, but that crews often did less, and relied on the air brakes with cars that were only temporarily set out. Check published or online rule books for operation of trains. My knowledge comes mostly from air brake instruction manuals, which tend to focus on ideal rather than actual operating practices.
On October 8, 2020 at 5:52 PM Climax@... wrote:
Since I model the 1900 to 1927 era this is important to me. If, as you say, a train set a few cars on a siding did all the hand brakes need to be cinched down or would they only do one car? Dave
From: John Stutz
Sent: Oct 8, 2020 5:04 PM
Subject: Re: AIR BRAKES 101.... was Re: RGS #20. Was: [HOn3] Division Point K-27 question
Circa 1900 brake cylinders used leather gaskets to seal the brake cylinder, and they usually leaked off slowly. This is why set out cars are supposed to always have the hand brake set.
The air and hand brake act independently, through the foundation brake gear, the set of rods and levers that carry braking force to the brake shoes. The air brake cylinder piston has a hollow stem holding a push rod. When the air brake is activated, this rod pushes on the connected lever. The hand brake is connected to the same lever, usually through a chain. When the hand brake is wound up. the chain pulls on the lever, and pulls the push rod partially out of the brake piston's stem.
The triple valve is the heart of the automatic air brake, and some version has been used from the first automatic system of circa 1870. The triple has undergone frequent revision ever since, to adapt it to evolving RR demands for better control of longer, heaver and faster trains. But all versions have essentially operated in the manner that Earl described. The KC or KD brake is simply the standard freight car apparatus of circa 1890-1940, fitted with the type K triple valve of circa 1902, and arranged in the Combined or Detached format. The principle improvement of the AB valve is the provision of separate service and emergency valves, with separate air reservoirs, so that full emergency power is always available.
On October 8, 2020 at 1:20 PM Climax@... wrote:
Lets say a box car was left on a siding with a grade. Now there is either a very slow leak or can someone come along and pull the bleed off rod and would that result in the brakes being applied through springs to not let the car roll, or would the brakes release and let the car roll? If it did roll, and you jumped on the car to get to the Brake wheel, does that apply or release brake pressure.
The triple valve is on an AB system while a K system did not have that feature of triple valve?