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Thread: AC4400 speed control expert please raise your hand

  1. #1

    Default AC4400 speed control expert please raise your hand

    Hello, and thanks in advance.
    First, I want to admit to not having done an exhaustive search on the 4400 speed control system. Thus, those fond of admonishing with references to crimes against the common good for not reading a particular doc.... feel free to let me have it ! Both barrels.

    I learned to use that system on Sand Patch. Using the 4400's speed control got me a little spoiled so I made sure I also ran the SD-40 coal loading scenarios - to keep in shape.

    The motivation for this post, and subsequent questions, arises from trying to operate the 4400 speed control to load the various substances on Cane Creek. (potash and contaminated earth I believe)

    On Sand Patch, one sets up the speed control, releases brakes, and applies power. ( see Powering America part 1 )
    On Cane Creek - the throttle is inoperative if the speed control is on. (same indications as reverser being in Neutral)

    I am not asking for advice on Cane Creek scenarios as much as, "how does a 4400 speed control work?" Secondly is the operation of the speed control grade dependent ? If so, what else does it depend on?

    I ask the questions about grade since that is a notable difference between the two.

    Have a great day.
    73,

  2. #2

    Default

    Quote Originally Posted by Rebrecs View Post

    On Sand Patch, one sets up the speed control, releases brakes, and applies power. ( see Powering America part 1 )
    On Cane Creek - the throttle is inoperative if the speed control is on. (same indications as reverser being in Neutral)

    I am not asking for advice on Cane Creek scenarios as much as, "how does a 4400 speed control work?" Secondly is the operation of the speed control grade dependent ? If so, what else does it depend on?
    One must suspect a mental malfunction from a person who responds to their own questions. Who cares.
    Update, the 4400 speed controls behave identically on Cane Creek and Sand Patch.
    My prior observation was erroneous.

    And yes, there are dependencies, and quirks. The important dependency is load. Not being a real train guy, I will use non-train explanations. Load = weight of train + drag + pitch angle. Stating the obvious, the speed control system must have enough power available to accomplish its mission. What is needed in order to operate the speed control successfully is knowing how and when to provide the power.
    All of the Sand Patch Scenarios involve loading sites with reasonable pitch angles and well powered consists. Due to that, people such as myself come away with a poor understanding of what is actually going on with the speed control system.
    Cane Creek changes that.

    Additional dependency: If there is more than one engine in the consist, the Speed Control system interacts with the Distributed Power system. There are some quirks in that area, in particular when there are three engines. I would like to say, "the dependency is the same as for normal operation under Distributed Power," but I'm not yet convinced. At a minimum, there are differences in how the operator applies the throttle on the Lead engine. And that is with Distributed Power working perfectly. If there is an engine, especially a third engine in the consist that is not set up correctly for Distributed Power - that engine will ignore signals from the Speed Control System.

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