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Thread: Clinchfield - SD40 - Selector 1 thru 4 - and gratuitous commentary

  1. #1

    Default Clinchfield - SD40 - Selector 1 thru 4 - and gratuitous commentary

    Hi, I'm primarily hoping to grab the attention of our resident SD40 expert(s).

    My question is, what do the 1 thru 4 settings do on the Selector Lever?
    I got the "B" setting so no need to go in to that. I'm only concerned with 1-4.

    TIA

  2. #2

    Default

    Unit Selector Switches: 1-4
    The unit selector switch is used only on locomotivesequipped with dynamic brakes and a field loop circuit.Its purpose is to adjust circuit resistance for uniformdynamic brake operation .This switch should be set to the No. 1, 2, 3, or 4position, depending on the number of locomotiveunits physically and electrically connected together .The switch position should not be changed for anyreason other than to correspond to a change innumber of units being operated . For example, itshould not be changed if one of the units is isolatedor shut down while it remains in the locomotiveconsist .This switch position is of importance only in the leador controlling locomotive unit during operation indynamic braking. It has no function in intermediate ortrailing units.NOTE : Switch position may be changed only whilethe throttle is in IDLE or locomotive is at rest .It should never be moved while operating indynamic braking.

  3. #3

    Default

    sorry I had failed to notice "lever" in your question. Here's the info for "selector lever" 1 thru 4

    The controller is equipped with a selector lever, in instances where the locomotive unit is equipped with dynamic brakes or when it is necessary to manually control transition on trailing units not equipped for automatic transition . On units so equipped, this lever serves to establish proper circuits for either of these functions. The position of the lever is indicated in the lower of the two illuminated windows located at the upper left corner of the controller front panel . The lever is spring loaded so that movement all the way in one direction will index. Selector Lever12372CAB CONTROLS the selector cam one notch only in that direction . It must be allowed to return to center position before indexing again in either direction . When the selector lever is indexed to the B or braking position, the dynamic braking electro-magnetic contactors are energized . In this position the throttle lever moves freely(without notching) to control a braking rheostat and dynamic braking strength. When the lever is moved to the center or OFF position, all circuits are open. This position is used for locking the controller in unattended or trailing units. For operation under power, the lever would be indexed to the No. 1 position . Succeeding positions such as Nos. 2, 3, and 4 would be used only when it is necessary to cause transition on any non automatic trailing units operating in the locomotive consist.
    Last edited by SMRY; 05-29-2021 at 05:05 AM.

  4. #4

    Default

    Quote Originally Posted by SMRY View Post
    Unit Selector Switches: 1-4
    The unit selector switch is used only on locomotivesequipped with dynamic brakes and a field loop circuit.Its purpose is to adjust circuit resistance for uniformdynamic brake operation .This switch should be set to the No. 1, 2, 3, or 4position, depending on the number of locomotiveunits physically and electrically connected together .The switch position should not be changed for anyreason other than to correspond to a change innumber of units being operated . For example, itshould not be changed if one of the units is isolatedor shut down while it remains in the locomotiveconsist .This switch position is of importance only in the leador controlling locomotive unit during operation indynamic braking. It has no function in intermediate ortrailing units.NOTE : Switch position may be changed only whilethe throttle is in IDLE or locomotive is at rest .It should never be moved while operating indynamic braking.
    Interesting. Thank you.
    Uniform Dynamic Breaking across directly attached locomotives, and has nothing to do with distributed power when dynamic breaking is not selected. Gotcha

  5. #5

    Default

    Quote Originally Posted by SMRY View Post
    sorry I had failed to notice "lever" in your question. Here's the info for "selector lever" 1 thru 4

    The controller is equipped with a selector lever, in instances where the locomotive unit is equipped with dynamic brakes or when it is necessary to manually control transition on trailing units not equipped for automatic transition . On units so equipped, this lever serves to establish proper circuits for either of these functions. The position of the lever is indicated in the lower of the two illuminated windows located at the upper left corner of the controller front panel . The lever is spring loaded so that movement all the way in one direction will index. Selector Lever12372CAB CONTROLS the selector cam one notch only in that direction . It must be allowed to return to center position before indexing again in either direction . When the selector lever is indexed to the B or braking position, the dynamic braking electro-magnetic contactors are energized . In this position the throttle lever moves freely(without notching) to control a braking rheostat and dynamic braking strength. When the lever is moved to the center or OFF position, all circuits are open. This position is used for locking the controller in unattended or trailing units. For operation under power, the lever would be indexed to the No. 1 position . Succeeding positions such as Nos. 2, 3, and 4 would be used only when it is necessary to cause transition on any non automatic trailing units operating in the locomotive consist.
    Also interesting, but seems to complicate matters.
    It appears there is a remote control function other than Dynamic Braking, "...when it is necessary to control transition.."
    I don't know what transition means in the "locomotive" context.
    But now I wonder whether the SD40 units in Clinchfield are non-automatic trailing units.

    I don't think the additional information breaks your original answer though. I'm going to count locos, set the lever, and leave it alone. :-)

  6. #6

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    Honestly, I don't have TS2, but, willing to bet in game "Selector Lever" serves no function. Perhaps others as well.
    "Transition" moving, operating between 2 or more modes. RR doesn't simplify anything, esp. in writing.
    Having been at it a lifetime, I find myself preforming, explaining myself in same fashion.
    You'll discover that in many other areas here at TS. I've no trouble writing a novel, to even the simplest of questions... lol

  7. #7
    Join Date
    Nov 1999
    Location
    Doreen, Victoria, Australia.
    Posts
    7,003

    Default

    Hi John,

    Transition relates to the way the traction motors are wired.
    When starting the traction motors are wired in a series/parallel network to limit the current draw at start.
    At some speed, the wiring is changed to parallel only to be able to get higher current at speed.
    Cheers
    Derek

  8. #8

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    In RR world, even a simple 3 step input from the reverser, operators are to allow a 10sec transition period before moving to next position. Same with Throttle Lever. Nothing's to be preformed slam/bam.

  9. #9

    Default

    Quote Originally Posted by derekmorton View Post
    Hi John,

    Transition relates to the way the traction motors are wired.
    When starting the traction motors are wired in a series/parallel network to limit the current draw at start.
    At some speed, the wiring is changed to parallel only to be able to get higher current at speed.
    Interesting.
    Now I am curious about, as you said "At some speed..." and wondering whether each throttle position has a speed threshold at which a "transition" is initiated.
    If so, that may shed light on something I have wondered about forever, which is a difference in overall behavior in different throttle ranges. I know throttle settings are not the same a geared transmissions but often they seem to have characteristics that change across the throttle settings. (similar to a torque factor) The transition thresholds, if they exist, could account for what I have observed.

    The observation was originally logged trying to gain as much speed as possible before hitting a steep uphill grade.
    I got a better result walking the train up through the throttle settings than going straight to the max. The max was sluggish - like when you put your car in high gear to start off from a stopped position.

  10. #10
    Join Date
    Nov 1999
    Location
    Doreen, Victoria, Australia.
    Posts
    7,003

    Default

    Some discussion here:-
    http://cs.trains.com/trn/f/741/p/249329/2783262.aspx

    Transition will happen at a set speed.
    Cheers
    Derek

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