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Not versed well with proper terminologies, may need a little help - Thanks.
Would like to ask some questions about braking a a long train.
4 units up front, 100 cars, arriving at a 3 percent negative or decline grade, when the Engineer applies brakes (air), to bring the train down to 30mph (from 45), its my understanding, air service brakes, apply at the rear car first, and follows along the string of cars, in effect, "dragging the train down", to avert violent bunching (let alone potential derailments), then applies dynamic brakes to hold the trains speed, release the air brakes, increase the rate of dynamics as the case warrants or need be.
And exactly how does it work, if still 4 units up front, with the addition of two helper engines at the rear, of braking actions?
Is that statement accurate? Any direct references to links would be most appreciative.
Thank you sirs.
George Harris Member # 2077
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For starters, you are highly unlikely to see 4 units 100 cars on a 3% grae. Try say 1.5 to 2%. Normally braking starts with the engine and propogates through the train, so the cars immediately behind the engine are braked first.
With helpers on the rear, brakes could be applied from the rear through them. Mid train units have also been used to provide for more even application of the brakes and quicker set up time.
Skill in handling brakes in heavy grade territory is both a science and an art of which I know very little.
there are a number of on-line sources of information on this subject with wildly varying elvels of accuracy and completeness. Some searching would be in order.
Thunderbush Member # 30533
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Actually helpers and DP units have their auto brake valve cut out. So air only comes out the working brake valve ie the first locomotive. You are right about them pumping air into the train faster.
Coming down a big hill like that? Rutledge Iowa has a good grade ( CP told us if it was another 2 miles long they would have designated it mountain grade) Two ways of taking a train down it. Set 10 pounds of air then dynamics to regulate you to 10 mph or you can do it old school style. 10 pounds of air and throttle to keep you at 20 mph ( speed on the hill) and just hope the intermediate was clear lol. Even with having to stop at the bottom your brakes would be hot enough that once you shut down the throttle the train would come to a quick stop. Most class ones tell you no stretch braking dynamics only and just use air rarely. I am for using all the tools to get me over the road in one piece and safely.So at the top of the hill start shutting down your throttle to idle as the train gets to midway over the hill your in idle waiting to go to dynamic. Set a minimum and see what she does. SOme trains can be controlled like this. If you have to get to heavy in the dynamics set up to 10 pounds.If this controls it and lets you reduce your dynamics great. If not you need 15 pounds of air. If at any time you hit a point where nothing is working you plug it and hold on!
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