I think you'll find that the engineer isn't really backing off the throttle to gain slack so much as adjusting the throttle to fit what he/she sees on the ammeter/traction meter.
Ideally, you want a constant pull. Otherwise you chance pull-aparts.
Recall that on older EMD's, advancing a notch gains you an increase in RPM over what it should be. The RPMs then drop a bit. Don't know why, but they do.
Larry Resident Microferroequinologist (at least at my house) Everyone goes home; Safety begins with you My Opinion. Standard Disclaimers Apply. No Expiration Date Come ride the rails with me! There's one thing about humility - the moment you think you've got it, you've lost it...
UlrichI'm guessing that's what's going on.. i.e. using slack/train's momentum to best advantage to accelerate the train.
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timz Ulrich I'm guessing that's what's going on.. i.e. using slack/train's momentum to best advantage to accelerate the train. Only way to let the slack run in (on the level) is to reduce the engine's pull. Why would doing that make the train accelerate better? If the engine quits pulling the train, and allows the train to nudge it, then the engine is slowing the train.
Ulrich I'm guessing that's what's going on.. i.e. using slack/train's momentum to best advantage to accelerate the train.
Only way to let the slack run in (on the level) is to reduce the engine's pull. Why would doing that make the train accelerate better? If the engine quits pulling the train, and allows the train to nudge it, then the engine is slowing the train.
Looks like they're saying it helps to take slack when the train is stopped, and you're trying to start it. That was true in steam days, and maybe it still is.
Once the train is rolling, the only way to accelerate it (on the level) is to pull on it. Quit pulling on it, and let the slack roll in, and the train quits accelerating.
Considering that todays trains are nominally from one to two and a half miles long - what one sees at the head end of the train is not necessarily the condition the engineer is modulating his throttle for - it may be a sag or knoll that is being enountered well back in the body of the train - far from the viewer.
Gradients that a idividual's eyes and senses cannot see are easily seen and felt by a locomotive engineer and his engine consist with a 15K ton two mile train. A train that the engineer is trying to both move and control the slack that is contained in the train - slack that can tear the train apart if not controlled.
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Could some of the action/ motion that Ulrich describes be caused by the (anti) wheel slip control of the locomotive ?
- PDN.
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