Arosa And Braking - I Found A Way To Use Dynamics Without Derailing

Discussion in 'PC Discussion' started by paul.pavlinovich, Mar 25, 2021.

  1. paul.pavlinovich

    paul.pavlinovich Well-Known Member

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    In the six percent sections set the dynamics to 50%. Adjust the train brake until you can maintain 25km/h most of the time this is 31% vacuum brake. You still get a bit of jostling here and there but the train stays on the track.

    Paul
     
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  2. Oystein

    Oystein Active Member

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    How is this in real life? Braking for a long time will cause brakes to heat up. Do they normally use just the dynamic brake, or a combination (for the long parts with downhill) ?
     
  3. breblimator

    breblimator Well-Known Member

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    The discussion is partially about your concerns :) -> link
     
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  4. paul.pavlinovich

    paul.pavlinovich Well-Known Member

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    Rivet say that they use the vacuum brakes all the way down. A retired RhB driver commented on the one of the streams that isn't right.
     
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  5. appledates#4945

    appledates#4945 Well-Known Member

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    That is exactly how I finished the first scenario after failing multiple times! Works very well!
     
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  6. paul.pavlinovich

    paul.pavlinovich Well-Known Member

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    I've been contemplating and watching the carriages. There are two things that I think contribute to the derailment. The track isn't really curved its lots of tiny straight bits. When you do come off its where both a curve and a vertical transition exist. The other thing I notice is that the carriages do buffet each other - I think the couplings are modelled a bit too loose. If they were tight that wouldn't happen. It shouldn't matter that they're not modern automatic couplers. Logging operations used to loco haul link and pin or often simply chained log skeleton cars with the only brake being the reverser on the locomotive.

    Paul
     
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  7. Oystein

    Oystein Active Member

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    Speed alone isn't the cause of derailments. Tried to run the route in 80/90km/h and never derailed. If a train derails in TSW, it is most likely a bug. So I guess this will be fixed "soon".
     
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  8. breblimator

    breblimator Well-Known Member

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    Matt confirmed it's a bug in the latest video. It is related to dynamic brakes.
     
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  9. fabristunt

    fabristunt Well-Known Member

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    I don't think it's related directly to the dynamic braking, but it must have something to do with the rolling stock bobbing a lot. I detailed while accelerating at least twice, no brakes involved.
     
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  10. paul.pavlinovich

    paul.pavlinovich Well-Known Member

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    I did a couple of runs with locomotive only running light engine and they do not derail. I'll make another consist with one carriage and see what happens.
     
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  11. Rudolf

    Rudolf Well-Known Member

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    I ran this Tourist excursion train downward, mostly with dynamic brakes set to 50% and vacuum brakes between 30-55%. No problem at all. So it is possible, but you should not try to drive very sharp against the speed limit. It is quite steep and the wagons act like a mass, the couplers like a spring. Under circumstances they may start resonating. Which means the wagons start jolting and this easily may cause a derailment. Driving down is hard.
     
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  12. Glazier

    Glazier Member

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    I ran the first scenario with vacuum breaks on 48 and dynamics on 35-45 for different speed limits, works fine. The only problem is that you loose too much speed when entering flat sections of the track before you adjust both breaks, but it is still better than random derailments on curves :)
     
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  13. roggek

    roggek Active Member

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    Well on Bernina line with 7% gradients they use primary the dynamic brakes downhill all the time.
    At least on the six motor cars ABe 4/4 III:
    RhB Rätische Bahn, Automotrices série ABe 4/4 III 51 à 56 - YouTube
    At 3:26 your clearly hear the dynamic brakes, and at 3:54 your hear the vaccum brake applied to a standstill.
     
    Last edited: Mar 28, 2021
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  14. dbrunner#4864

    dbrunner#4864 Well-Known Member

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    Dynamic brake is the main brake used in Austria and Switzerland and many other countries when it comes to descending over mountains.
    Dynamic/electric brakes are mandatory for this scenario for the following reasons.
    -prevents over wear / heating of the brake pads when braking is required for steep slopes or long descent.
    -you can run out off air in the main cylinder if the air brake lever is used continuosly without being put in to release / recharge position. Extreme caution is needed, thus dynamic brake is far more safer for sections where continuous braking is needed
    -it offers a more fine tuning off the speed when going down
    -modern locomotives also use dynamic brake when automatic speed control is enabled
    -on lines with proper infrastructure modern locomotives can send the current generated during braking back in to the overhead wires this being more ECO friendly(Tgv duplex, the entire line of Siemens Eurosprinter locomotives and many more)
     
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  15. solicitr

    solicitr Well-Known Member

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    And in the USA too, where monstrous 100-plus car freight trains are the norm. For all the stated reasons, dynamics are your primary when descending a grade; friction brakes only as necessary. The tutorial video is simply wrong.
     
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  16. Rudolf

    Rudolf Well-Known Member

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    I am totally confused. For TS I long thought the dynamic brake was the primary brake to use going downhill. It worked fine. Then DTG introduced realistic braking and required to set the train brake a bit and use the dynamic brake for fine tuning. Same as Rivet recommends for Arosa. I see a video suggesting to use a mix of dynamic brake and use the train brake as well and the do fine tuning with the train brake. For the long US routes, this is not an option because you cannot release the train brake a little amount.

    To me it does not sound illogical to use some train braking combined with the dynamic brake. On the other hand, the GE4/4II vacuum brake behaves very different from the US train brakes and the vacuum brakes of the elder UK engines, it responds quite fast.

    So I still have no idea what is the correct answer and under which conditions. Probably we should not try to compare braking long US freight trains with a relatively light narrow gauge train like we see at Arosa line.
     
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  17. breblimator

    breblimator Well-Known Member

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    True. US freight is always balanced (mixed) braking.

    Arosa could be a little different, but - someones mentioned some stream commentary made by a real driver there* - mixed braking.
    *I could be an astronaut today, but... Interesting issue.
     
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  18. geloxo

    geloxo Well-Known Member

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    The problem with dynamic brake is that it´s not effective unless the locomotive is heavy enough, as it mainly uses the mass of the unit to reduce speed on the coupled wagons. In Arosa the locomotive is around 60 Tons only if I´m not wrong but the gradient is extreme compared to other routes, so the horizontal braking force the locomotive is able to produce is even lower while the resulting horizontal pushing force from the wagons all together is much higher. So basically the rear wagons are pushing locomotive too much even if they are light individually, leading to derailments. Using the vacuum brakes is the only way to reduce the wagons pushing force as it reduces the speed on all of them equally. But you can´t use too much vacuum braking for a long period of time without burning the brakes. So I think the best practice would be to use dynamic always but combined with at least a small amount of vacuum for sure to prevent wagons acceleration and their pushing. So clearly the mixed braking is the solution as with dynamic alone the disaster is granted.

    But there´s also another important topic: even if you are already braking you can still produce a derailment if you suddenly increase dynamic brakes too fast or you use locomotive brake too fast. That produces a sudden reduction in the locomotive speed and it will be still pushed by wagons, even if they are being held by some vacuum braking. So always try to increase both dynamic and vacuum braking forces proportionally to reduce speed and just release vacuum brakes when you are sure the locomotive won´t be pushed by wagons (at areas with regular gradients or at stations). This effect is also happening at heavy freight trains like the ones at Sand Patch but they behave different mainly because the consist mass there is so big that it takes much longer to react to a sudden braking application or release, not only due to its mass but also because the couplers springs disipate a lot of those small force variations while the brakes are being applied or released, and you have a lot of couplers in the consist. In Arosa the train is very short so any changes in the train physics are very fast and you can´t use the springs as an advantage.

    Cheers
     
    Last edited: Mar 29, 2021
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  19. breblimator

    breblimator Well-Known Member

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    The sequence is really important - not to go with all braking force to the front too fast.
     
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