Sand Patch Braking Query

Discussion in 'TSW General Discussion' started by hairyscotsman40, Sep 28, 2020.

  1. hairyscotsman40

    hairyscotsman40 Member

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    hi folks

    I am doing the service where one uses the 2 locos transferred to sand patch to transfer coal wagons back to Cumberland. What are the recommendations for control of speed downhill? I have all 3 brakes (auto, dynamic & independent) all at max yet can not maintain speed below limit, what am I not doing?

    TIA
     
  2. Trainmania100

    Trainmania100 Well-Known Member

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    The best solution to maintain control of speed going downhill is to not let the speed runaway in the first place.
    Once you've got a significant amount of momentum from the mile-long consist , on a steep downhill gradient, if you apply all 3 brakes you'll end up sliding down the hill,
    The thing I do is maintain around 10mph below the actual speed limit using the automatic brake at around maybe 15% service with dynamic brake on about 4, then release/apply more depending on whether i'm gaining or losing speed
    It's not good practice to reach the speed limit and then slam on the brakes expecting to slow down straight away (which would work with a ECW class 377, but not a mile long heavy train :) )

    Obviously if you've got it set to snowy weather or torrential rain, then you need to be slower still
    it is definately tempting to floor it , it is a long route takes long time, perhaps dinner ready soon; but patience is a virtue and may be worth saving / resuming later if you dont have time.
     
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  3. Class395

    Class395 Active Member

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    All of the above + this: Applying independent brakes + automatic (train) brake is pointless. Independent brakes are the locomotives brakes and are applied as part of the Train Brake system.

    Also, if it helps you understand as to why you don't want to slam on the brakes on a very long and heavy train:
    Train brakes apply sequentially as pressure drops in the brake pipe on the entire length of the consist, this means that the brakes will first apply on the locomotives, then the first car, then the second, third... and so on until finally the brakes on the last car apply. This can take up to a couple of minutes, same with releasing the brakes.
    Hope i was helpful
     
    Last edited: Sep 28, 2020
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  4. bones.n.hombre

    bones.n.hombre Active Member

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    I’m new and struggled with this as well, but now I only use one brake.

    Auto brake - works on every unit on the train and is based on air pressure.
    Independent brake only works on the tractor unit/engine unit.

    I found neither of these are of use for slowing down/controlling momentum when at higher speeds.

    Now the Dynamic brake is where it’s at. How that works (simply) is it reverses the direction of drive from the engine. It would be rubbish at slow speeds and for stopping, but for speed control it’s perfect and all I use. Throttle needs to be to zero. Place the Dynamic brake in ‘setup’ for at least ten seconds (to charge it)
    Then increase the ‘reverse throttle’ (Dynamic brake) as you need to reduce speed. Remember like everything, it isn’t a ‘quick acting’ thing and you have to think ahead.

    I can fully control the highest slope downwards without using the other brakes and maintain a decent speed.

    At lower speeds I use Auto brake.
     
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  5. Class395

    Class395 Active Member

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    Real life engineers use the dynamic brake to control speed because having friction brakes (train brake) constantly applied over a long period of time would simply burn out the pads and render the train brake completely useless. Dynamic brakes lose their efectiveness as the train slows down. What basically happens when the dynamic brake is applied is the traction motors are essentially reversed and used as generators in order to generate resistance for the spinning axles. The generated electrical current is directed to the radiators and bleeded off as heat.

    [​IMG]

    So essentially, the train needs to be moving for the dynamic brakes to work. I hope my technical explanations help you get how the braking systems work, for me it was always easier to know how to use something if I already know how it works ;)
     
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  6. Teza

    Teza Member

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    Yes, Dynamic brake is an engine brake, and is not pushing pads to the wheels, and it sole function is for this down hill heavy train
    as in real life you would not want to apply the pads to the wheels all that way down a big long hill,
    as they would over heat and wear out fast, when you are starting the down hill part, and can set throttle to off for 10 sec
    and then put Dynamic brake to set up mode, wait for 10 sec and then apply it,
    as you apply the engine will sound like its Throttling up, this is the brake
    set it to 8 for full engine brake, you will not have use of the Throttle now it is disabled when Dynamic brake is in use.
     
  7. Driver8666

    Driver8666 Active Member

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    That's the radiator and air intake.. DB is behind the cab.

    Source: Instruction Manuals for GE locomotives.
     
  8. Driver8666

    Driver8666 Active Member

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    Not the way it's applied in practice. It's a high pitched whine. And very telling too.
     

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