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Thread: Starting a Short But Heavy Train On A Downgrade

  1. #1
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    Post Starting a Short But Heavy Train On A Downgrade

    Retaining control when starting a short heavy train on a downgrade is anything but easy.

    Once you release the parking brake, the train gets up to 15 mph very fast. Before you know it, you're way over 23 mph.

    I would think the only way to retain control is to set handbrakes on several cars in the train. Am I correct here? If yes, which ones, i.e. by place in the consist or by weight?

    Also, am I correct to say the independent brake has to be released if the Dynamic brakes are in use? I recall reading that doing otherwise causes flat wheels on the locomotives.

    Thanks,

    Robert

  2. #2
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    Normally about a minimum application of 6 PSI (I believe that is the minimum in Run8) is required on a heavy grade as you would have if you were going down the hill anyways (It's been a while but you may have to release the auto brake to get rolling once setup has started before you put it back on again once rolling). The Indy break can then be set before a full release of ALL hand breaks.

    Once that is in place go ahead and get your dynamics set to a comfortable level depending on the train that would normally keep you at track speed. It will automatically adjust it's power to a lower level as the indy is on (or the opposite if you were to apply it at a slow speed for stopping). Gradually pull the indy into release, and the dynamics will start to kick in.

    At that point you should start to slowly accelerate (if not release the auto break and let it build back up). But on a heavy grade make sure you have set up the minimum PSI reduction as this will give you greater flexibility and control on the descent.

    Thanks

    Sean

  3. #3
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    Quote Originally Posted by SurvivorSean View Post
    Normally about a minimum application of 6 PSI (I believe that is the minimum in Run8) is required on a heavy grade as you would have if you were going down the hill anyways (It's been a while but you may have to release the auto brake to get rolling once setup has started before you put it back on again once rolling). The Indy break can then be set before a full release of ALL hand breaks.

    Once that is in place go ahead and get your dynamics set to a comfortable level depending on the train that would normally keep you at track speed. It will automatically adjust it's power to a lower level as the indy is on (or the opposite if you were to apply it at a slow speed for stopping). Gradually pull the indy into release, and the dynamics will start to kick in.

    At that point you should start to slowly accelerate (if not release the auto break and let it build back up). But on a heavy grade make sure you have set up the minimum PSI reduction as this will give you greater flexibility and control on the descent.

    Thanks

    Sean
    Hey Sean:

    Thanks for your help - worked great.

    Can you elaborate on the following:

    1 - Are we saying the independent brakes can be on at the same time as the dynamic brakes?

    2 - Before getting started rolling, can the dynamic brake be in setup?

    3 - Is it OK to leave the handbrakes set on a certain number of cars, or am I thinking about an adjustment where the brakes on some cars are left partially set?

    4 - What speed are the real-world engineers expected to use going downhill, i.e. how do they keep on schedule?

    Robert
    Last edited by ForestHIllsRob; 01-28-2013 at 11:44 AM. Reason: Added Additional Question

  4. #4

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    Stopping:

    When going downhill, use minimum brake set (84 psi), then dynamic brakes to control the speed. If you need over 50% dynamic brakes, then reduce the brake pipe pressure by one or two more psi. When it is time to stop, increase the dynamic braking to get the speed under 5 mph, then use loco brakes to come to a stop. The loco brakes plus the train brakes will hold the train.

    Starting:

    Engage the dynamic brakes at 5 or 10% and release the loco brakes and the weight of the locos will start the train moving (don't release the train brake!). Use dynamic brakes again to control the speed. By not touching the train brakes and using dynamics to control speed and loco brakes to start/stop, you can stop in every siding if required with no danger of running out of air.

    Starting from a saved game:

    Before moving off, apply the minimum train brakes (84 psi) and full loco brakes. Release the handbrakes (F5). Engage the dynamic brakes at 5 or 10% and release the loco brakes to get moving. If you need over 50% dynamic brakes to control speed then drop the train brake pressure by another psi or two.

    Remember: once you apply the train brakes, don't release them until you get to the bottom of the hill (caliente or mojave). Use the dynamic brakes above 5 mph and add loco brakes below 5mph when coming to a complete stop. Also, you would never have a train moving with the handbrakes set.

  5. #5

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    I usually take the train brake off coming downhill into Caliente. There's a stretch through the curve and the siding that is pretty much flat, compared to the rest of the hill. I may or may not re-engage the air at the west end of Caliente, depending on length and weight. The air always comes off about halfway thru Ilmon on the main, in expectation of the rear passing the 50 speedboard. The DB's stay on until Sand Cut and come back on once most of the train is over the top.

  6. #6
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    1 - Yes
    2 - I believe so but you need the dynamics on
    3 - I don't know if it's prototypical, personally I see no need for it.
    4 - Track speed, or other restricted speed based on type. I believe I heard Key Train is limited to 15 MPH.

    To echo the last response as well it's been a while since I started down hill so I'm glad you confirmed keeping the break on. The reason why that is of course and I've been guilty of this as well is putting too much break on or getting on a train where RD was set to too much break. Any time you release it takes time to build it back up so if you have too much your now relying totally on your dynamics to slow you down once the pressure builds back up before you can apply again.

    I've been using dynamics more and more with the minimum set to stop nice on a downhill. Uphill you can use the throttle modulation to stall out and set enough auto break to hold you on the uphill.

    Thanks

    Sean

  7. #7

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    Sean, you need to watch the amps on the DB's when the indy brake is engaged. The DB's get automatically bailed off as you apply the indy, which the pro's have indicated is prototypical for the GEVO and most other engines with modern electronics.

  8. #8
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    From what I've seen the amps only start to bail off when it's safe to do so. For example a full indy and dynamic will partially reduce it, but it isn't until the train comes to a full stop when the amps shut down. What that will do is prevent a rollback if a minimum auto brake is also in service.

    I normally don't set fully indy until under 15 (as I've been told that isn't good otherwise). Once it's set the dynamics are still doing most of the work until it reaches a threshold. Then it's safe to cut out the dynamic entirely since it will likely be at 0 amps by then anyways.

    Thanks

    Sean

  9. #9

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    Sean has posted a better summary than I did. That's correct, the amps start coming off once you are down to the point in speed where the indy brake begins to take more effect and the train starts to come to a stop.

  10. #10
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    I actually learned that by accident about a month ago when I was going a bit too fast towards the end of a siding.

    Thanks

    Sean

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