How basic mechanical principles can change over time. Forty years ago on the Southern Rwy when an undesired emergency brake application occurred while pulling a train we "bailed-off" the Independent Brake and left the throttle in #1 position in an attempt to prevent the rear of the train from running into the head end. When in Dynamic Brake and the undesired emergency occurred we applied the locomotive brake to keep the slack compressed on the entire train. At this point in time no rule could require an engineman to fully apply the independent brake. All units were equipped with cast-iron clasp brakes whose coefficient of friction varied with the speed of the locomotive. An engineman then had the skill to graduate the independent brake consistent with speed to prevent flat spots on the wheels as the train speed decreased. As an RFE we always instructed " a rotating wheel has more retardation value than a sliding wheel". When depositions were taken after incidents occurred, we always managed to have this statement included.
Today with hi-friction material brake shoes and relair valves to control Brake Cylinder pressure to a multitude of different brake rigging designs in a mixed consist I guess one can stand by the decision to fully apply the independent brake and let nature take its course. One thing todays generation will never experience is how cast iron shoes would anchor a locomotive in a hurry at speeds below 20 MPH; and when flat switching no having to back up after getting a truck length over the switch points.
