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Thread: Speed Matching?

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    Default Speed Matching?

    After reading comments posted in the DCC Complexity thread I thought about this Speed Matching thing and how engines need to have that done to be able to run (properly) in a consist. But, why is that needed?

    If I buy two identical engines each with an identical decoder, say TCS Decoder as an example, shouldn't both engines run identically?
    Cheers Tony

    "Knowing what to do is one thing ... being able to do it is another"
    "It is easy to criticize ... a lot harder when you have to justify it"

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    Quote Originally Posted by wombat457 View Post
    If I buy two identical engines each with an identical decoder, say TCS Decoder as an example, shouldn't both engines run identically?
    Usually, yes. At least close enough. There may be variations in the motor or wherever that make the speeds a little different, but if you are talking about identical locos with identical decoders then they should run very close as long as you have the CV settings the same. Identical locos running at the same speed is generally how people run multiple locos on DC after all (though you can also add resistors to try to speed match DC locos, but I've never tried that).

    Where speed matching really comes in is with different locos, or different decoders (maybe I want sound in one, but don't want to pay for sound in all of them). Yes it's a little bit of a pain, but it's possible.

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    Thanks OTFan, logically they should but, hey who knows
    Cheers Tony

    "Knowing what to do is one thing ... being able to do it is another"
    "It is easy to criticize ... a lot harder when you have to justify it"

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    I should probably also mention that there are all kinds of variables here... For example, I have two Kato C44-9Ws, but they were made a decade or so apart. They do not run at the same speed (at least not before speed matching), despite being the same type of loco from the same manufacturer. My (untested) assumption is Kato changed motors some where in between those production runs... or maybe the older one just has a lot more run time... but whatever the reason, they are not the same speed. That was actually one of the things that prompted me to switch to DCC - they're now chipped, speed matched, and run happily together. Another time I noticed that the pair of locos I run the most (an Atlas GP38 and GP 30) were no longer speed matched. I started messing with CVs until it dawned on me to disassemble, clean and lubricate... then they were speed matched again at the original CV settings. So yeah, lots of things can mess with the idea that identical locos with identical chips should run the same.

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    Quote Originally Posted by wombat457 View Post
    If I buy two identical engines each with an identical decoder, say TCS Decoder as an example, shouldn't both engines run identically?
    Not really, Tony. No two motors are identical -- at the price point to keep the model affordable -- in performance at a given voltage, no two drive assemblies and wheel sets have the identical friction that would pose the identical load to the motor. You can observe that simply by placing two, say, new Atlas GP38s -- DC only -- put the identical voltage to them, and watch how they run.

    And no two decoders are identical -- transistors and resistors especially, even in microprocessors, have some degree of +/-tolerance.

    Quote Originally Posted by OTFan View Post
    they should run very close as long as you have the CV settings the same.
    Not my experience. I've found wide disparity in CV settings using identical decoders in identical locomotives. And Tony's question really asks why adjusting CVs is necessary with identical locomotives using identical decoders. It's because friction, motor performance and decoder performance create a degree of inherent variances from locomotive to locomotive.

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    Thanks and I doubt I will have a need to run two engines in consist BUT, if I did, they would be the same engine, make and decoder purchased for that reason. In fact I have two never been run Kato ES44AC engines with (hopefully) current ESU Lok Sound decoders in them. They would be the two engines I ran together if any at all.
    Cheers Tony

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    Paul,

    Thanks - you and I must have posted at the same time
    Cheers Tony

    "Knowing what to do is one thing ... being able to do it is another"
    "It is easy to criticize ... a lot harder when you have to justify it"

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    Okay so just to confuse things a bit more - if I wanted someone to speed match two engines and say program them to their cab numbers for me and they use a digitrax system, will those engines still work for me using an NCE system? In simple terms, if someone with a digitrax system programs the engines will my NCE c read them?
    Cheers Tony

    "Knowing what to do is one thing ... being able to do it is another"
    "It is easy to criticize ... a lot harder when you have to justify it"

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    Controller shouldn't make a difference. Even if the signals sent from NCE and Digitrax don't match eachother (and for speeds at least I'm pretty sure they will), in your thought experiment you are not running NCE on one while running Digitrax on the other. Either both are getting packets from NCE or both from Digitrax so they will get the same speed packets at the same time.

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    As stated above, two identical loco should run the same. But, sometimes is not what we want. And is not at the wrong moment. My F7A and F7B units, are bought at the same time, and i was expected to run the same being known are consist units. From box, without any CV changing, running on default settings, unit B is more fasten than unit A, in both direction. Like this, default settings, small differences on mechanical friction, electrical motor, etc, make the units to run different. I make the test on my diorama, with 1/2 inch distance between the unit. Forward, unit B push unit A, reverse is pulling if them are coupled, if not, go slowly far away. not a big deal. I just make the test with both on address 3. I am curious to see if is the same if i program them in consist and run with the same 1/2 inch gap, to observe the difference. I did not stated the brand of locomotives, BLI, the one which make a trail of parts on track after a while. Still run okay, i not have another trouble. But mine was running only 40-50m on my diorama. Who know in time if start to rain with gear components also in my yard.
    I LIKE TO WORK WITH BIG SHIP ENGINES BUT I SPEND MY FREE TIME AROUND N SCALE TRAIN MODELS.

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