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Thread: Braking on Descending Grade

  1. #1
    Join Date
    Nov 2003
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    Wilmette, Illinois
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    Default Braking on Descending Grade

    For the real engineers reading this, what is the prototypical procedure for using the train and dynamic brakes on a downhill grade? Searching the forum I've seen mention of using the DB by itself whenever possible. Yet, what happens with the buff forces when all the braking is from the head end? Don't you risk run-in? If the grade were especially steep wouldn't you also risk derailing some of the cars at the front of the consist? It would seem the DB acts like a locomotive brake that hasn't been bailed.

    So, on behalf of those who both want to understand and do it as "right" as we can on the current MSTS, could someone please clearly explain whether and how to combine using both the train and DB -- and how to judge whether a specific gradient and train makeup requires one, the other, or both.

    In advance, thanks for taking the time and effort.

    Barry

  2. #2
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    Stalinist,broke United Kingdom (Hey buddy,can you spare �1.3 trillion?))
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    Default RE: Braking on Descending Grade

    Here in UK we do not have dynamic brakes (on freight trains,dont know about our modern passenger trains)so no problem,friction brake only.With any braking/accelerating,as has been discussed here before the trick is to be gentle and not go violently from buffered up to run out and vice versa or you are liable to break couplings or buffer lock.I admire my US counterparts with the size of train they handle.The heaviest I have driven is only 3000 tons but with a single loco.

  3. #3
    Join Date
    Nov 1999
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    Doreen, Victoria, Australia.
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    Default RE: Braking on Descending Grade

    Hi Barry,

    I asked a similar question of a driver that I know and this is what I got:-


    To contol the slack you have to realise that it is better to have the train all bunched in or drawn out, To have the train in different modes IE front bunched up and rear drawn out is to invite disaster or at the very least a smack into the windscreen.

    Keeping this in mind you now have to look at the geography of the track in question as to the method applied to brake the train.

    Going over the top of a substancial grade you would let the train dribble over the top (say 15 to 25 kph) of the grade and set up and apply the dynamic brake early as its most efficient between 50 and 60 kph.

    Going down hill the dynamic brake would be selected and brought up to the required amount of amps, when the train has settled
    the automatic brake would then be moved to the minimum reduction position and after the brakes have set on the train the automatic brake would then be moved to the applied position (then lapped on A7EL) at the required amount of braking force nesassary to stop or impede the train to the desired speed.

    A good rule of thumb is 1kph per wagon for releasing the brake so 40 wagons you cannot release the brake under 40 kph or you could pull a coupler or smack into the windscreen as the front releases before the back.
    This can change with a down heavy grade (such as ingleston) as you will have the dynamic in hard and the train is bunched in on the locos due to the gradient so lower speed releases can be attained here.
    Usually you lose from 15 kph to 40 kph depending on the lenght of the train upon release of the brake but this can be greater with over 50 wagons.

    A word of warning here you dont release the dynamic brake until the flow meter has started to settle and the train brakes have released fully as the brakes on the rear of the train are still releasing and a runout might result with the accompanied visit with the face to the windscreen or coupler damage.

    Going into a sharp dip say with a speed curve like at Creswick you would get in early with the dynamic brake bring the speed down to under the speed knowing that the train is going to gain X amount of KPH (experience) going down the dip and not release the dynamic brake until proceeding up the grade, then apply light power picking up the train 1 wagon at a time advancing the power as the load comes on to the locos.

    Going up hill you would use 2 to 3 notches of power and make a minimum reduction to set the brakes at the same time releasing the independant brake to set the train in a drawn out mode then making greater reductions until stopped or the desired speed has been attained. the

    On the flat either method works depending on the mood or hurry to get home or with just a straight air application to stop being ok as well the 1kph per wagon for releasing the brake rule applies here..
    The Dynamic brake should be used whenever possible as its very energy efficient and prevents wheel/brake block wear.
    experience is what matters here as how you plan your moves.

    Cheers
    Derek

  4. #4
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    Default RE: Braking on Descending Grade

    Here's an illustrated primer on how I do it on the rather unique grade on my route:

    [Link Expired]

  5. #5
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    Default RE: Braking on Descending Grade

    Based on information from various sources -

    briefly, on downhill grades, use dynamic brakes (apply slowly to allow train to bunch up slowly); train speed controlled by adjusting dynamic brake setting.

    For steeper downhill grades, apply train (automatic) brake, then apply dynamic brake to (fine) control train speed.

    The degree of air and dynamic brake application, of course, depends on the steepness of the grade and train weight.

    It helps to know the route, so you can set up the brakes to the proper settings and at the appropriate time to avoid clashing between cars and locomotives, and (in extreme cases) to avoid the possibility of a runaway train.

  6. #6
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    Default RE: Braking on Descending Grade

    I think even on steep grades, you would get the dynamics slowly applied before applying the train brake so that the train becomes bunched. Experience would tell you whether you will need air or not or how much.

  7. #7
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    Atlanta, GA, USA.
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    Default RE: Braking on Descending Grade

    You need to start reducing throttle as soon as the engines start down hill. Then you want to be in idle when half of the train weight is on the downgrade, i.e. the weight of the train is balanced at the crest of the grade. Then you get about 300 amps of dynamic brake to bunch the slack and catch the rear half of the train as each car comes over the crest. Once the entire train is on the down grade, use the dynamic brake to control the speed of the train, using as little air as needed to supplement. Once the train reachs the bottom of the grade and the engines start up grade you can release the dynamic brake. Releasing the dynamic too soon on the downgrade can cause a slack runout and break the train in two. If you try to maintain whatever speed you topped the grade at until the entire train is on the downgrade, this will allow you to control the train speed with the dynamic brakes on all but the steepest hills. Don't try to get back up to track speed too soon.

    Richard Kimball

  8. #8
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    Default RE: Braking on Descending Grade

    >For steeper downhill grades, apply train (automatic) brake, then apply dynamic brake to (fine) control train speed.

    That will get a kiss of the windscreen.

    Cheers
    Derek

  9. #9
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    Wellington, NZ
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    Default RE: Braking on Descending Grade

    Sorry folks! Yep, I got that around the wrong way; should be dynamics first and then the train brakes.

    >>For steeper downhill grades, apply train (automatic) brake,
    >then apply dynamic brake to (fine) control train speed.
    >
    >That will get a kiss of the windscreen.

    Not necessarily. I'm talking about slight application of train brakes. Excessive air braking may cause clashing (between cars, locomotives); this also depends on braking system used (electro-pneumatic valves, or standard pressure drop valves). Excessive air braking will cut out the dynamic brakes also.

    The key is to apply brakes GENTLY, whatever type they are.

  10. #10
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    Default RE: Braking on Descending Grade

    >>That will get a kiss of the windscreen.
    >
    >Not necessarily. I'm talking about slight application
    >of train brakes.

    If you are on a downhill grade with a long stretched train and apply any air brake, you WILL smack the windscreen.

    The air brake works from the front to the back, so the front of the train is braking before the back. When the unbraked part hits the braked part <smack>.
    Cheers
    Derek

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