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Thread: Modeling #6 air brakes on steam locomotives

  1. #1

    Default Modeling #6 air brakes on steam locomotives

    I've been able to get what I think is a pretty good understanding of the different air brake systems on locomotives and how they're modeled in MSTS. I have one question I haven't been able to find an answer to though. On #6 train brake control valves, is the apply quadrant a simple on / off or is it variable like it is on the later 24RL type systems?

    Thanks!

  2. #2
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    Having run both 6L (on a very early production EMD SD-9 and the SP&S 700 steam engine) and the 24RL (on multiple later model ex-Southern Pacific SD-9E rebuilds) the only real difference in the two brake systems is that the 6L does not have the pressure maintaining feature. Since MSTS does not model train-line leakage, it does not matter whether a system has the pressure maintaining feature or not.

    Perhaps word of explanation here on the what the pressure maintaining feature actually does. A train that will travel over 20 miles must have it's entire train-line connected w/an air pressure minimum 75psi at the rear car (this rear pressure must be confirmed by an air pressure gauge in the caboose, a portable air gauge connected to the rear glad-hand or a functioning rear-end device aka FRED). A bottled air test must be performed and no more than a 5psi drop in the entire train-line is permitted. Now the 24RL pressure maintaining valve can inject enough air into the brake line to overcome a 5psi leak. On a 6L brake valve there is no valve to allow pressurized air from the main air tanks to hold a train air brake pressure reduction once the brake handle is placed into the "lap" brake quadrant. If you have a train with a good 5psi train-line leaker what happens is the brakes gradually apply more pressure to the wheels and will drag the train down causing a possible stall. The engineer must basically release the train brakes completely (remember you can gradually apply the trailing cars brakes, but you cannot gradually release them) and reapply the brakes with a fresh reduction in the train-line pressure. If the cars are not allowed to have their air tanks replenished he must take a deeper reduction to achieve the desired retarding force on his train (called "recycling the air") and if you need more then 3 recycling events you are dangerously close to losing control of your train, especially on a descending grade. When the new 24-RL came out it was a Godsend to engineer's in regards to train control. The new EMD SD-9 with it's 6-cylinder air compressors were impressive indeed in compensating for a leaky brake pipe. I have had 4 SD-9's coupled to a 50+ car train with a confirmed 7-9psi leaking brake pipe and the valve maintained a steady brake reduction pressure.

    I must also add that the 24-RL had one other feature that many do not know and it was called the accelerated release feature (the 6L system did not have this feature). Basically when you moved the brake handle into the "release" quadrant (on all brake systems including the 6L) air is allowed into the train-line at a controlled rate. One quadrant further to the right of the release position aka "running release", on the 24-RL, was this accelerated release feature. It opened a second port to the brake line that basically allowed high pressure air into the line to aid in recharging the train thus causing the train's trailing brakes to release quicker (the quick release feature that showed up in new freight car brake systems in the late '50's rendered this feature obsolete and even problematic as the high speed ingestion of air into the brake line, from the accelerated release port, would cause to the accelerated signal to literally bounce a shock-wave of air back forward from the rear closed angle-cock triggering an emergency brake application of the rear car). This extra air port feature on the 24-RL really added a lot of air into the brake line. I, on more than one instance, was able to get enough air pressure into a train-line on longer trains with an open rear angle cock and got the brakes to release on all the cars allowing me to move the train (again, this was with at least 4 SD-9's in run 4 with the big air-compressors). These two brake systems were my favorite to run as they added more challenge and work to be done by the engineer to control his train. Hope this helps with your brake question.
    Last edited by Turbo Bill; 11-20-2011 at 01:00 AM.
    Bill
    Rule of The Day: 147.7.16.B
    When all previously LISTED Trainhandling braking methods fail to produce desired results......JUMP!!!! Either way it's gonna hurt.

  3. #3

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    Thanks Bill!

    Your explanation is definitely one of the best I've read comparing the two systems, after scouring around online trying to study air brake information. Since I don't have any original air brake manuals, it's been a challenge to understand some of the descriptions of the different systems. The locomotive manuals I had looked at weren't much better, most having statements that they assume the crew knows how the air brakes work so they don't say much.

    Thanks!

  4. #4
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    I love reading Bill's explanations about how it really works. Cool info, thanks a lot!

    Steve

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    After reading my post a day later there is a couple things I would like to clarify. On the "Bottled" air test the engineer must (after being notified that at least 75 psi is present at the rear angle-cock of the rear car car) make a 20psi reduction in the train air line and wait for the signal to reach or activate all the brakes in the train. He does this by watching the two white needles in his two air pressure gauges. The right needle is the equalizing reservoir pressure and the left is the train air line actual pressure present at that moment(note: the left needle will always follow the right needle). When the left needle matches the right needle and the engineer can no longer hear air being bled from the brake pipe he then sets train brake control switch to "cut out" and times this portion of the test for one minute to allow for equalization of pressure in the brake line. Once that minute is passed he notates the air line needles position (left white needle) and times it for one more minute. He notates the brake line pressure drop, if there is one, at the end of the minute and the difference is the amount of leakage he has in the train for one minute. You can have up to 5psi/minute and no more. If it is over 5psi, the offending car or air line glad-hands that are leaking must be found and repaired or that car must be set out of the train in a yard or at the next available siding if enroute. A non-passing air test leak is quite easy to hear by the crewman walking the train and usually it's a damaged or wore out glad-hand gasket or angle-cock. The latter usually could be beat into silence by a couple good wacks with a sizable chunk of ballast or air hose wrench. I think this where the idea of wacking your ill running car engine with a hammer came from. At the end of the test, the engineer moves the brake handle into the realse quadrant and "cuts" the air back in with the brass brake system cut-out knob (you can see this nob on several American cabs in MSTS, it the little brass round nob under the train horn handle) and once he has confirmation of 75psi at the rear of the train he may continue down the line but only he is sure the conductor is on the train. Don't laugh I have heard of it happening back in the day before the disappearance of the caboose.

    Also the application quadrant on the 6L and 24-RL brake systems was a variable quadrant. The further you moved the handle to right in this quadrant, the faster the air evacuated out of the brake line. When satisfied with the amount of reduction made, the engineer would move the handle into the "lap" quadrant in the 6L system and the lap or pressure maintaining quadrant on the 24-RL.

    The new 26L brake system that replaced the 24-RL in the '60's had an application quadrant were you applied your reduction based on how far your brake handle was placed in this quadrant. Once the desired brake pipe reduction was reached you just left that handle at that position and the system would maintain the brake pipe pressure. You did not have "lap" or "pressure maintaining" quadrants at all on this system. Also the pressure maintaining valve on the 26L was a major improvement in air pressure sensitivity to keep up with the newer triple-valves in new railcars. The 24-RL having a more antiquated pressure maintaining valve many times would fluctuate the brake line pressure just enough to allow or trigger a release in one of the newer car's triple-valve and the quick release feature on this car would start ingesting a 2psi increase into the brake line causing the cars along the train in both directions of it's location to release their brakes. As soon as the railroad I worked for acquired a fleet of GP39-2s to replace the loner SD-9Es we were given by the Southern Pacific at the start-up of the regional the SD-9Es were given back except for a handful bought and retain for switchers and locals. A couple of these venerable six-axle beasts still forge on to this day but their time is limited by what I heard. These were without a doubt the best road switcher engines I ever ran. The electric relays were so much more faster in relaying commands from the throttle handle and so much faster to load up then the newer computer controlled models that you could easily add a good hour to your switching time using the newer engine over the older SD-9's. Also you didn't have to wait for that huge turbo to spool up when kicking cars around in a yard working a local.

    Sorry for the long posts but I hate giving less than as accurate answer if I can. Sometimes if takes a day or two to notice omit-ions in my original post.
    Last edited by Turbo Bill; 11-20-2011 at 02:47 PM.
    Bill
    Rule of The Day: 147.7.16.B
    When all previously LISTED Trainhandling braking methods fail to produce desired results......JUMP!!!! Either way it's gonna hurt.

  6. #6

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    Bill, I definitely have to say thanks again having read your follow up from your original reply. The details on doing the air test were particularly enjoyable to read as well as the further clarifying details comparing the old and new brake systems. The info. is invaluable in appreciating the differences in my MSTS locomotives, and identifying which ones need tweaked!

  7. #7
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    Bill, two other questions...

    I was looking through a couple of braking/operation manuals that I have (PRR stuff mainly), because I was trying to understand under what conditions it is necessary to do a brake test as you're describing. Certainly, if you were switching cars in a yard, you don't do a complete brake test every time you add or subtract a cut of cars?

    I've seen crews on the local short line here bumping cars around on the local sidings - one train sets cars out and then another comes from a side branch and drops cars off, and picks up the set off cars. They have to make several back and forth moves to swap all the cars given the track configuration, but I'm certain, watching them, they're not doing a brake test at any time other than when they've got their consist set for moving over the road. Then they sit and I hear the various air venting noises that seem consistent with doing the brake test.

    So what's the logic behind when you want to do the test?

    Incidentally, in one of those old PRR manuals, I found a reference to using 3 psi per minute as the maximum pressure loss requirement, seemed to be referring to MU equipment. Would there be different requirements depending on the service, like Passenger vs. Freight?

    Steve

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    Steve, I will give a detailed answer tonight. There are several instances where a brake test is required and not all of them require the airtest portion to be performed. I'll grab the 'ol rulebook out tonight and give it a double-check to make sure the answer is all correct. For the record when simming I do perform at least a set and release test before moving on the next customer or yard down the road. Stay tuned for more my fellow Hoggers )
    Bill
    Rule of The Day: 147.7.16.B
    When all previously LISTED Trainhandling braking methods fail to produce desired results......JUMP!!!! Either way it's gonna hurt.

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    OK, let's see if I can explain this so one can make sense of when to do what brake test and when you must do a brake test along with the air leakage test.

    When do you perform a train brake test? Remember these tests are performed before you proceed to the next point of your trip and after all necessary switch movements have been completed and train is ready to proceed to new location.

    1. When leaving an initial terminal with a car or block of cars. Note: Remember that an initial terminal can be anywhere you start your trip with that locomotive or train.
    2. When picking up or adding a car or block of cars to your train.
    3. When portion/s of your train have been uncoupled and recoupled.
    4. 1000 mile intervals on all trains that will travel over 1000 miles in a single trip w/o adding cars enroute. This test is the same as an Initial Terminal brake test.
    5. Anytime a locomotive/s is added or removed from the consist or when changing ends or rear car or caboose is replaced.

    You generally have ascertain one thing in regards to when you must incorporate the air leakage test or 'alt' for short. NOTE: A train considered “kept charged” has had its brake system charged to at least 35 psi within the last 2 hours. If it has been charged in the time allotted you only perform the brake test portion, if not charged with in the allotted time you must also perform 'alt' as well.

    Procedure For Initial Terminal Air Brake Test and
    Inspection

    A. Inspect Train For Air Brake System Defects
    Begin the test by inspecting the train for air brake system defects.
    1. Inspect the angle cocks and verify that they are properly positioned.
    2. Inspect the air hoses and verify that they are in condition for
    service and properly coupled.
    3. Inspect the system for leakage.
    4. Make necessary repairs to reduce leakage to a minimum.
    5. Inspect the retaining valves and verify that they are in EXHAUST
    (DIRECT RELEASE).

    B. When the brake system is charged within 15 psi of the regulating
    valve setting:
    1. Test brake pipe integrity with the brake pipe leakage
    test.
    *To conduct a leakage test:
    1. Charge the train brake system to within 15 psi of the equalizing
    reservoir as indicated by an accurate gauge at the rear of the
    train.
    2. Wait for the signal to apply the brakes.
    3. When you receive the signal, reduce brake pipe pressure by
    20 psi.
    4. Allow the brake pipe exhaust to stop.
    5. Wait 60 seconds.
    6. Move the automatic brake cutout valve to the OUT position.
    7. Wait 60 seconds.
    8. Measure the leakage for 60 seconds.
    a. Make sure leakage does not exceed 5 psi during this period.
    b. Do not actuate during the leakage test.
    9. Use the appropriate air brake test to inspect the cars.
    10. When you receive the signal to release the brakes, move the
    automatic brake valve handle to RELEASE and move the automatic
    brake cutout valve to the FRT position.

    2. During the test the conductor or certified employee must Verify that:
    a. Brakes apply on each car.
    b. Piston travel is correct.
    c. Brake rigging does not bind or foul.
    d. All brake equipment is properly secured.
    3. When the inspection is complete, give the release signal.
    4. After the release, inspect each brake to make sure all are released.
    The release may be verified during a roll-by inspection.

    Test With Yard Test Plant
    When the initial terminal air brake test has been performed with yard
    air and a locomotive has been added:
    1. Make a 20 psi brake pipe reduction.
    2. Verify that brakes apply and release on the rear car.

    *Before leaving the test location, make sure that 100 percent of the air
    brakes are operative. A train enroute must have at least 85% of it's brakes working properly.

    Notifying the Engineer
    A qualified employee who participated in the test and inspection or
    who knows the test was completed must notify the engineer either
    verbally or in writing that the initial terminal air brake test has been
    completed satisfactorily. However, the qualified person must provide
    the notification in writing if the outbound crew will report for duty
    after the qualified person goes off duty.
    Engineers receiving written or verbal notification of the air brake test
    must accept the notification as authority that the initial terminal air
    brake test has been completed satisfactorily.
    Bill
    Rule of The Day: 147.7.16.B
    When all previously LISTED Trainhandling braking methods fail to produce desired results......JUMP!!!! Either way it's gonna hurt.

  10. #10
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    Air Brake Test When Adding Cars

    *Adding Pretested Cars:
    When adding a block of cars pretested by the initial terminal air brake
    test:
    1. Make a 20 psi brake pipe reduction.
    2. Verify that the brakes apply and release on the rear car.
    3. Verify that brake pipe pressure at the rear of the train is being
    restored.

    *Adding Cars Not Pretested:
    Conduct an air brake test if cars are added to the train when:
    The train is not at the initial terminal.
    One or more cars have not been pretested by the initial terminal
    air brake test.
    To conduct the test:
    1. Test brake pipe integrity with the brake pipe leakage
    method.
    2. Make a 20 psi brake pipe reduction.
    3. Verify that the brakes apply and release on each added car and
    on the rear car.
    NOTE: When performing the brake pipe leakage test, verify
    that the brake system is charged to at least 60 psi.

    Yard Movement Test
    Test the air brake system on a train making a yard movement that
    does not exceed 20 miles in one direction. To conduct the test:
    1. Couple brake pipe hoses between all cars.
    2. Charge the brake system to at least 60 psi.
    NOTE: If a rear gauge is not available, determine brake
    pipe pressure by cutting out the automatic brake valve and
    noting the pressure at which the brake pipe pressure
    stabilizes, as indicated by the brake pipe pressure gauge.
    3. Make a 20 psi brake pipe reduction.
    4. Verify that the brakes apply on each car.
    NOTE: Yard movements are not limited to movements made
    within yard limits. When setting out or picking up cars during
    a yard movement, a more stringent test is not required.

    Air Brake Test When Cutting Off and
    Recoupling
    Conduct an air brake test when one or more cuts are made in a train
    and the cars are recoupled in 2 hours or less. To test the air brake
    system:
    1. Open the angle cock.
    2. Make sure that brake pipe pressure is being restored and the
    brakes release on the rear car.
    EXCEPTION: If the train does not have an operative end-oftrain
    telemetry device or occupied caboose:
    1. Make a 20 psi brake pipe reduction.
    2. Make sure the brakes apply and release on the rear
    car.

    Application and Release Test
    At a point other than an initial terminal, conduct an application and
    release test when:
    Any locomotive in the locomotive consist is changed (including
    changing operating ends).
    A caboose is changed.
    Helper locomotives are added or removed anywhere in the train.
    One or more consecutive cars are set out from the head or rear
    of the train.

    * Procedure For Application and Release Test
    To conduct an application and release test:
    1. Verify that the brake system is charged to within 15 psi of the
    regulating valve setting.
    2. Make a 20 psi brake pipe reduction.
    3. Verify that brakes on the rear car apply and release.

    Locomotive Air Brake Test
    Conduct a locomotive air brake test when:
    Making up a locomotive consist
    Adding or removing locomotives
    or
    Changing operating ends
    From the ground, observe that the locomotive brakes apply and
    release during the air brake test.
    *Making Up, Adding, or Removing Locomotives
    When making up locomotive consists, or when adding locomotives to
    or removing locomotives from a consist, use the following procedure:
    1. Adjust the regulating valve to the required brake pipe pressure.
    2. With the independent and automatic brake valve handles in
    RELEASE, apply the independent brake.
    3. After the brakes apply on both sides of all locomotives in the
    consist, release the independent brakes and observe that the
    brakes release.
    4. When the brakes are released on all locomotives and the equipment
    is fully charged, apply the automatic brakes by making a 20
    psi brake pipe reduction.
    5. Observe that the brakes apply on all locomotives.
    NOTE: You do not need to walk both sides of the consist
    after observing that the brakes applied during the independent
    brake test.
    6. Cut out the automatic brake and observe the brake pipe pressure
    gauge. Verify that the brake pipe leakage does not exceed 5 psi
    per minute.
    7. Cut the automatic brake back in and move the automatic brake
    valve handle to MINIMUM REDUCTION. Verify that the
    equalizing reservoir pressure does not increase.
    8. Actuate (Bail-off) the independent brake and observe that the brakes
    release on all locomotives.
    Personal note here: I do not remember doing the following portion of the locomotive brake test. I believe this following test portion was performed at the Roundhouse where the various locomotive consists where initially lashed up. Often times when we would tie up a long transfer train we would park it on the main short of the town or location of my Home Terminal and uncouple the lead locomotive and cut the brakes in on the second locomotive, tie sufficient handbrakes to prevent unwanted movement, set it's headlight to dim lock the cab and use the lead unit we cut away as a cab ride to the depot. The relieving crew would than take that locomotive back to the train, reconnect it and do the aforementioned locomotive brake test and a 20psi application and release test on the entire train before continuing to the next point.
    9. With the independent brake in RELEASE (not actuated), place
    locomotives in FULL dynamics.
    10. Put locomotives in EMERGENCY by opening the angle cock on
    the rear unit of the consist.
    CAUTION: Do not perform this part of the
    air brake test over a fuel spill containment
    area, since the locomotive will deposit sand
    while the consist is in EMERGENCY.
    11. Verify that the brakes apply as indicated by the brake cylinder
    pressure gauge.
    12. Verify that:
    Brake pipe pressure reduces to 0 psi.
    The PCS opens.
    Dynamic braking remains operable.
    * Changing Operating Ends
    When operating ends have been changed but the consist otherwise
    remains unchanged, perform the following air brake test:
    1. Release the independent brake and verify that the brakes release.
    2. Make a full service brake application and verify that the brakes
    apply.
    3. Actuate the independent brake and verify that the brakes release.
    NOTE: If conditions permit, you may perform this test at 1
    MPH to 3 MPH and allow the locomotive to drift with the
    throttle in IDLE.

    Hope this answers your questions. I know it may be heavy reading and confusing to some. Please ask here if you are unsure of any of this.
    Bill
    Rule of The Day: 147.7.16.B
    When all previously LISTED Trainhandling braking methods fail to produce desired results......JUMP!!!! Either way it's gonna hurt.

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