Fix For Chicago Racetrack F40ph Brake Pressure / Drag

Discussion in 'Technical Reports' started by torfmeister, May 17, 2022.

  1. torfmeister

    torfmeister Guest

    So I returned to The Racetrack, and I noticed the same "drag" effect as seen on the F7 Empire Builder or the GM Aerotrain.

    Ever found it tedious to leave the station in "All Stops to Aurora Pt1" for example and trying to keep the speed at 10 mph? As soon as you go to idle the train is decelerating too quickly, feels the cars drag it to a stop.

    Now the reason again is, the loco fills the brake pipe to 90psi pressure only, but the coaches' cylinders need a pressure of 110psi on the pipe to fully release the brake cylinders. You can even see it as the cab shows the train brake cylinder pressure.

    I took the values from DTG's F40PH2 which is working correctly, with 110psi as usual for american passenger trains.

    Changed MaxSystemPressure from 90 to 110 and FullServicePressureDrop from 26 to 32.

    I've also edited the input sensitivity of the Throttle and Brake Handle and corrected the Brake Handle Positions from Release>SelfLap>Suppression>FullService>Emergency to the correct order Release>SelfLap>FullService>Suppression>Emergency.

    Enjoy!

    Before (drag effect because of brake cyl pressure >0, left arrow)
    f40ph_def.png

    Patch applied:
    f40ph_fixed.png
     

    Attached Files:

    Last edited by a moderator: May 17, 2022
  2. jbrowncs

    jbrowncs New Member

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    torfmeister -- I appreciate all the good work you are doing with these patches.
     
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  3. torfmeister

    torfmeister Guest

    Thanks, appreciate the feedback.
     
  4. 749006

    749006 Well-Known Member

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    Slightly OT but I wonder why the BP Pressure is so high on US trains?
     
  5. torfmeister

    torfmeister Guest

    Source: https://cs.trains.com/trn/f/111/t/226381.aspx

    Posted by Paul_D_North_Jr on Wednesday, January 8, 2014 9:28 PM

    Freight train may well be considerably heavier, unless it is mostly empties, as passenger equipment is generally roughly equal in weight to an empty freight car, even when fully loaded with passengers.


    Aside from that - and also a concurrent result of it, too - passenger trains are usually assigned a higher power-to-weight ratio (horsepower per trailing ton), so they will accelerate faster and climb grades faster than freight trains. The same considerations mean that a passenger train can usually descend a grade faster than a freight without risking a runaway from brake shoe fade, etc.


    Finally, most passenger train air lines are set for 105 or 110 psi, whereas the standard freight train pressure is 90 psi.* That means the passenger train can make more of a 'reduction' = harder brake application before the reservoirs equalize with the brake pipe (see: http://www.alkrug.vcn.com/rrfacts/brakes.htm#pressurevariation ). So, passenger trains can go somewhat faster closer right up to stops and speed restrictions, etc., thus resulting in faster over-the-road time than an equal length (and even an equal weight) freight train.


    *See: http://www.railway-technical.com/brake2.shtml - "3. Air Pressure Variations" at the bottom of the page.


    "Air Brake Pressure on Amtrak Trains Using Freight Power" at: http://www.trainorders.com/discussion/read.php?4,2422482


    http://www.sdrm.org/history/timeline/amatic.html


    Rule 100.6 on page 6 of: http://www.blet75.org/2013-05-01_abth_updated.pdf


    - Paul North.
     
  6. 749006

    749006 Well-Known Member

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    Having copied the above info you might have checked as most of those links don't work.

    Europe uses a brake pipe pressure of 5 Bar/72.5 Psi and has not problems stopping Passenger trains at higher speeds
    We use a twin pipe system where a Main Air supply of around 100 Psi is constantly charging the Air Reservoirs on the coaches.

    Peter
     
  7. torfmeister

    torfmeister Guest

    I'm sure using google you'll get the information you need, I found the copied post to have enough information. Railroads have developed differently in different countries, see also track gauges.

    It seems we don't have an american railroad engineer on the forums.

    My task is to make sure the stuff works as close to reality as possible.
     

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