Clinchfield Brakes

Discussion in 'PC Discussion' started by space_ace96, Apr 8, 2021.

  1. OldVern

    OldVern Well-Known Member

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    We need a Run 8 style quick command, both to set up the cab/train and to overcome the PCS popping.
     
  2. DTG Natster

    DTG Natster Producer Staff Member

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    *Update* We have found that during the F7 introduction you can come across a problem where the rear loco and the front loco are both fighting for control of the brakes causing you difficulties.

    A temporary resolution you can use is to jump into the other cab to cut out the rear loco's brakes.

    We are already investigating how to resolve this and when we can provide you with an update.
     
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  3. Ravi

    Ravi Well-Known Member

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    Thank you. I also had to cut-out and cut in the brakes again before the lights reset. I was able to run the scenario again.
     
  4. Heerenrailfan92

    Heerenrailfan92 Member

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    same, only the emergency brake worked for me as well (PS4 user btw)
     
  5. solicitr

    solicitr Well-Known Member

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    Read the posts above. It's a setup issue in the tutorial (only)
     
  6. Heerenrailfan92

    Heerenrailfan92 Member

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    yup I did the tutorial again, it still didn't work but the scenarios are working fine luckily so It's not to bad
     
  7. solicitr

    solicitr Well-Known Member

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    You can do the tutorial: all you have to do is go into the rear cab and set the cutout valve on the brake stand to cut out, like it's supposed to be. By default it is (mistakenly) cut in, which means that from the front cab, as you are trying to reduce brake pipe pressure the rear loco is filling it up again.
     
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  8. blaze111csx

    blaze111csx Well-Known Member

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    https://drive.google.com/file/d/1Dxvv3jzENRd4WvvPfzEDhVO5RkVdavg8/view?usp=sharing
    this is an example of what happens (I realize I accidentally hit the engine run switch on my raildriver but that shouldn't turn the train off, just disable the controls) I also didn't turn on the bells and if you can't tell they are ringing on both engines. also the PCS on the F7 seems to turn off if you set the Auto brake to emergency and the reverser to neutral and then immediately shut them both off again
     
  9. speedstr99

    speedstr99 New Member

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    The automatic brakes do in fact not work. I'll just get to 15 mph go into emergency then neutral 100 independent then release auto to reset the system and repeat the cycle until I get tired of pissing with it and never play it again. I'll stick with sand patch; At least I know the AC-4400-CW auto brake works without flaw. Maybe it's something has a highly trained operator of CSX for 19 years that I seem to be missing. People make mistakes you know, but it could be a bug as well. INFO: I really don't know but in reality if the auto brake is not working properly, it gets tagged as an inoperable locomotive and the locomotive be out of service until the right people get to it and limp it to the shop. A giant folder, plum full of inspection and testing records. Its red and behind the second man seat on most. Can't miss it.
     
  10. speedstr99

    speedstr99 New Member

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    I did over look the rear Loco cut out valve. I'm resuming now and we shall see what I come up with. Give me a few minutes. Now I know why they get paid so well stress.
     
  11. OldVern

    OldVern Well-Known Member

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    The train brakes work fine, you just need to finesse the service application then back to lap - watch your gauges or the brake pipe reduction on the HUD. Having traditional braking on the F7 adds to the challenge. Better get used to it because if we ever get steam locos in TSW, whether air or vacuum braked, pretty much all use set and lap braking system, not progressive/stepped.
    As I have said the only thing there needs to be is maybe more of a detent, to accidentally prevent going past service into emergency.
     
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  12. breblimator

    breblimator Well-Known Member

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    They work very very well. Just read the whole of this thread from A to Z :)

    ...
    This brake works like a faucet - it's turned on (service) - you add water to the bucket. You turn off (lap) - the water stops flowing, but also stays in the bucket (braking level). Running (release) position - you pour out the water - all. Pouring out takes a few moments. The bucket is finally empty - the train goes on.
     
    Last edited: Apr 10, 2021
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  13. speedstr99

    speedstr99 New Member

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    That's what it was. I set the rear locos cut valve to put and the brakes work great. Lack of sleep leave me alone lol.
     
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  14. JustWentSouth

    JustWentSouth Well-Known Member

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    I have become a big fan of driving the F7; so many things to love, especially the brakes. They are perhaps there most enjoyable brakes in the game for me.

    The initial application is not too much of a reduction and then, after that, it is easy to finesse small increments of braking with the apply and then lap settings. I feel like I have much finer control than with auto lapped brakes.

    I have not had the issues of accidentally sliding into emergency. I program the ; and . keystrokes to buttons on my gaming mouse and the brake reliably slides into initial service, lap, apply, and back to lap for me.
     
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  15. cwf.green

    cwf.green Well-Known Member

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    I have a question for Matt:

    Have the physics of the brakes in terms of the air brake curve as a function of speed been changed for Clinchfield compared to Sand Patch?

    What I mean with "air brake curve" is the weaker brakes for the same brake cylinder pressure at high speeds vs low speeds, sort of analogous to how dynamic brakes work better at low speeds (before they begin to fade close to zero speed). For an example, the brakes on the Class 101 model this quite well. The brakes will "bite" significantly at low speeds.
     
  16. breblimator

    breblimator Well-Known Member

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    I am very curious too :)

    If you haven't bought CRR yet - this is a change for the better, as long as it's not an illusion. The F7 and SD 40 are more sluggish, they are less responsive to commands, they require planning and proactive driving.
     
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  17. blaze111csx

    blaze111csx Well-Known Member

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    the air brakes are weird to say the least, sometimes they work great and others... well le's say i've had to set the emergency brakes a few times.
     
  18. OldVern

    OldVern Well-Known Member

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    The only thing I would add is there does seem to be an issue with rolling inertia. Running down a 0.1% gradient which is near as darn it level, with the loaded manifest train I was constantly in and out of light dynamics to keep the speed from rising. Whereas in reality I would probably have needed light power to keep rolling. Obviously we don't want the sticky glue wheels on rails effect from the Class 66 or Class 70 in TS which wouldn't coast at all, but it may be some tweaks to the physics are needed.
     
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  19. solicitr

    solicitr Well-Known Member

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    Keep in mind that the grade half a mile behind you may well be steeper than what's under your seat.
     
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  20. cwf.green

    cwf.green Well-Known Member

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    I noticed this as well, but there might be some (non-bug) reasons for this:

    1. Speeds on Clinchfield are so low that there is very little air drag.

    2. The grades are undulating and the trains are long so there might have been a steeper down slope behind the locomotive that is pushing down the train.

    3. The trains are heavy. If I'm not mistaken the manifest train is over 4000 tonnes? Let's say the average grade was in fact 0.2%, that would result in a grade force of around 80 kN (18 klbf).

    4. The F7 were some of the earliest locomotives to use dynamic brakes so the technology isn't exactly perfected on these locos. I read that the maximum force is attained at around 23 mph but at 10-12 they have faded to almost nothing. If you were driving on the slow sections the air drag would be essentially zero and the dynamic brakes would be very ineffective.

    I'm not saying the inertia/friction is realistic, but it might be difficult to sense whether it is, without testing and quantifying the physics.
     
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  21. breblimator

    breblimator Well-Known Member

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    Someone once posted a graph showing the effectiveness of dynamic brakes against speed. It would be nice to see it again.
    EDIT with some pro-commentary in the context of F7 / SD 40
     
  22. OldVern

    OldVern Well-Known Member

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    No this is on a sustained slight down grade, for sure.
     
  23. Callum B.

    Callum B. Well-Known Member

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    Dynamic brakes on DC locomotives lose their usefulness around 10 to 15 MPH. AC locomotives can use dynamics to come to a near stop. For the F7, I found its dynamics to fall in line with how I would expect a DC locomotive to at lower speeds.

    Cheers
     
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  24. gordon.ramsden

    gordon.ramsden New Member

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    For those who are interested I have just found this https://www.alternatewars.com/BBOW/Railroads/EMD_F7_OM.pdf which seems to be the 4th edition of the original EMD F7 Operating Manual from 1957, looks to have a lot of useful information and may answer some of the question in this thread.
     
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  25. raretrack

    raretrack Active Member

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    Great find, Gordon! I'm sure that manual will help with general ops and driving technique tips too.
     
  26. Callum B.

    Callum B. Well-Known Member

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    I just had this phenomenon happen to me on the CRR 92 Southbound Manifest service (with an F7). I was messing around with the automatic and manual electric field settings when suddenly my power dropped to zero. To my surprise, the engine shut off and, sure enough, the bell in the rear locomotive of my A-B-B-A lashup started ringing.

    Another curious thing: only once this happened was I able to move the Transition lever past the 2 setting (Parallel Series Shunt) into a previously-inaccessible notch 3 and 4, which had just Parallel and Parallel Shunt if I recall correctly. After fixing the train and restarting everything, I could no longer move the Transition level to notch 3 and 4, no matter whether I was in Automatic or Manual mode. Very curious indeed.

    I have no idea if I can replicate this issue on demand but I can definitely say it occurred when I flipped the switch on the back of the cab to change transition modes. I never once touched a brake handle.

    Cheers
     
    Last edited: Apr 11, 2021
  27. Callum B.

    Callum B. Well-Known Member

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    Alright, I think I figured out how to reproduce this bug consistently. This is actually one of several ways I have been able to trigger the effect, but this is the simplest method.

    1. Load into any service with an F7. I'm not sure if it also works in a scenario, but it definitely works in multiple timetable runs.
    2. Set up everything to move forward (Control & fuel pump, generator field, engine run, rotair valve set to Freight, etc.).
    3. Set the Transition lever to 1 or 2, doesn't matter which one.
    4. Increase the throttle to start moving forward.
    5. Increase your amp load to at least ~750 and then cut the transition lever to OFF. The engines should now cut out and the bells will start ringing.
    Why does this happen? And why does this unlock the Transition Lever control stand notches 3 & 4? I can record and attach a video demonstration if requested.

    Cheers
     
  28. Coastway trainspotter

    Coastway trainspotter Well-Known Member

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    The same is on Xbox
     
  29. solicitr

    solicitr Well-Known Member

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    Query: when you do this, do any of the fault lights come on? According to the real-life manual, a "chime" is supposed to sound whenever one of those lights is lit.

    IIRC, one is not supposed to move the transition lever when the throttle is in Notch 7 or 8
     
  30. solicitr

    solicitr Well-Known Member

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    This issue has been covered so often, DTG have temporarily added a splash screen to the game: go to the cab of the rear loco and set the brake cut-out valve to Cut Out. Problem sorted.
     
  31. Coastway trainspotter

    Coastway trainspotter Well-Known Member

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    Ah yes , I did notice that . I thought it was just a small tutorial
     
  32. Lamplight

    Lamplight Well-Known Member

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    In this F2/F3 manual, only for transition from 2 to 3 is it mentioned that it doesn‘t work in notch 7 or 8. Curious thing is though that when I was playing around with manual transition this morning, I could only move from 2 to 3 with the throttle in run 8, the transition lever wouldn‘t budge upwards while I was in any lower notch.
     
  33. OldVern

    OldVern Well-Known Member

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    Something else further to my earlier post.
    The rolling resistance seems consist related. Running downhill on a 0.3% gradient with the coal hoppers on Greenbriar Part 3, I was not experiencing undue acceleration. Turning out on to the branch line and the 1.9% downgrade, I overbraked to a stand. After releasing the brakes I then actually had to apply power to get going, whereas in reality on that degree of hill the train *should* have started rolling of its own accord.
    Obviously looks like there is further work to be done on the physics in all respects.
     
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  34. breblimator

    breblimator Well-Known Member

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    CRR trains are not as long as SPG but Dash 8 train equipped with EOT (plus AFM indicator in the cab) needs up to 10 minutes for the brakes to be 'released' (from the full application) in terms of some rail rules (75 PSI EOT, airflow < 60). As I said, CRR trains are not as long. I assume You know all that :)
     
  35. solicitr

    solicitr Well-Known Member

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    Yup. Depending on grade and train weight, you ain't gonna budge until the BP pressure at your end gets up to anywhere from 65-80 psi.
     
  36. cwf.green

    cwf.green Well-Known Member

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    I think I have seen similar graphs. For old DC locomotives the dynamic brake effort will be linear up to some speed of maximum effort and then decrease as 1/v (v = speed) above that point.

    When a current is driven through a loop there will be a magnetic field that curls around the conductor (imagine gripping the conductor and pointing the thumb in the direction of the current, the fingers will curl around the conductor in the same way your fingers are). If you place the loop in a static magnetic field and let the loop connect to the power source in such a way that if the loop turns then the polarity is reversed, you will get a torque on the loop due to Lorentz force. There's your motor (probably badly explained and might be wrong on some details).

    When the motor is rotating with angular velocity w there will be back emf, basically the motor acts as a generator. This back emf is proportional to the angular velocity of the wheel/rotor.

    V_emf = K_i * w (K_i = constant, w = angular velocity in rad/s)

    The current will then be the difference between the source voltage and the back emf (divided by the motors electrical resistance R)

    I = (V_s - V_emf)/R = (V_s - K_i*w)/R

    The torque of the motor is proportional to the current above
    T = K_t * I (K_t = constant)

    This explains why the current and torque decreases with increasing speed of the locomotive

    T = K_t * (V_s - K_i*w)/R

    At some angular velocity the back emf is equal to the source voltage V_s so the torque is zero.

    So what happens when the source voltage is turned off? I'm not actually sure what happens. If the equation still holds but V_s = 0 that would imply that you have a braking torque of

    T = -w*K_t*K_i/R

    but we know that locomotives don't suddenly start to brake when you reduce the throttle to zero. Perhaps this is what happens in the small toy DC motors? Maybe DC locomotives have electromagnets that are powered off when the throttle is turned off. Then the magnetic field would be zero and the torque would also be zero.

    Either way, it does not surprise me that the dynamic brake force is linearly proportional to the speed at low speeds (T = - C*w, C = constant).

    Perhaps there are people that know more about these things on the forum willing to explain? :)
     
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  37. Callum B.

    Callum B. Well-Known Member

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    No fault lights come on. In fact, all lights are dark without engine power.

    I don't doubt it. I was able to trigger the same effect in a different way without the throttle in notch 7 or 8 (using the switch on the back panel) but it was less consistent.

    Cheers
     
  38. RestrictedProceed

    RestrictedProceed New Member

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    That's how it works. Most older DC traction motors are series-wound, which means their field windings are in series with their rotating armatures. Once you cut the power off, there's no current flowing through the field windings and thus there's no magnetic field. In reality, there would be a weak field left due to remanent magnetization.
     
    Last edited: Apr 18, 2021
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  39. RestrictedProceed

    RestrictedProceed New Member

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    Something like these?
    Sources:
    Link
    Link2
    r01w0007-figure-02.gif obrázek_2021-04-18_140258.png
     
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  40. breblimator

    breblimator Well-Known Member

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  41. RestrictedProceed

    RestrictedProceed New Member

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    Note that SD60's dynamics (graph 1) are very effective even at low speeds. I'm quite sure that's because it uses extended range dynamic brakes. Nice explanation of their function is here.
     
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