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Voltage on Z

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  • jjabour@xxxxxxxxx.xxx
    Hello I have a question on Z scale voltages. I have both Marlkin and MT engines. The documentation for both say that you should not exceed 8 volts. Also the
    Message 1 of 7 , Dec 12, 1999
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      Hello
      I have a question on Z scale voltages. I have
      both Marlkin and MT engines. The documentation
      for both say that you should not exceed 8 volts.
      Also the MT says not to run them on pulse power.
      I own 2 Marklin power packs (the large white ones
      that cost alot of money and aren't as good as some
      MRC power packs that I have for HO). I put a dc volt
      meter on them (actually I tried 2 different ones)
      and both power packs put out a maximum of 12.5
      volts. So what I do is only run them up to 3/4
      maximum. Am I missing something? Also why does MT
      say not to run them on pulse (do they have coreless
      motors)? I installed a Digitrax DCC in one of the
      Marklin engines. When I run it on DCC I set the VMAX
      to 8 volts (but don't know if I have to).
      Thanks for any help in advance.
      John Jabour
    • Jeffrey MacHan
      Hi John, Welcome to the list. George Menzie of MT is a member of the list. Perhaps he has some wisdom to share with us regarding the warning concerning pulse
      Message 2 of 7 , Dec 12, 1999
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        Hi John,

        Welcome to the list.

        George Menzie of MT is a member of the list. Perhaps he has some wisdom to
        share with us regarding the warning concerning pulse power with the MT F7...

        ...in the meantime I will hasard a guess.

        Small DC motors tend to warm up considerably when running on pulse power.
        The MT F7 has no air space to help cool the motor and the shell is quite
        thin. The danger, I believe, is not to the motor per se, but to the shell
        which could possibly warp.

        Some modern transistor throttles inject pulses at low voltages to help
        overcome resistance and to get the loco off to a slow speed start. The
        pulse form drops as voltage increases until the loco is ultimately running
        on pure DC at normal speed. The problems would start to show up with a Z
        loco running constantly at a crawl on pulse power. It wouldn't take too
        long to generate a lot of heat and turn the shell to putty.

        The floor is open to other opinions.

        Happy Holidays,
        Jeffrey

        >From: jjabour@...
        >Reply-To: z_scale@onelist.com
        >To: z_scale@onelist.com
        >Subject: [z_scale] Voltage on Z
        >Date: 13 Dec 1999 00:35:05 -0000
        >
        >Hello
        >I have a question on Z scale voltages. I have
        >both Marlkin and MT engines. The documentation
        >for both say that you should not exceed 8 volts.
        >Also the MT says not to run them on pulse power.
        >I own 2 Marklin power packs (the large white ones
        >that cost alot of money and aren't as good as some
        >MRC power packs that I have for HO). I put a dc volt
        >meter on them (actually I tried 2 different ones)
        >and both power packs put out a maximum of 12.5
        >volts. So what I do is only run them up to 3/4
        >maximum. Am I missing something? Also why does MT
        >say not to run them on pulse (do they have coreless
        >motors)? I installed a Digitrax DCC in one of the
        >Marklin engines. When I run it on DCC I set the VMAX
        >to 8 volts (but don't know if I have to).
        >Thanks for any help in advance.
        >John Jabour
        >
        >------------------------------------------------------------------------
        >CraZy 'bout Zee!
        >
        ><< text3.html >>
      • BJKRONEN@xxx.xxx
        John: First, welcome to the list. ... Oh boy. Your first question will no doubt have quite a response. This is not the easiest of questions. Brace
        Message 3 of 7 , Dec 12, 1999
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          John:

          First, welcome to the list.

          > I have a question on Z scale voltages.

          Oh boy. Your first question will no doubt have quite a response. <grin>
          This is not the easiest of questions. Brace yourself for several different
          answers.

          > I have both Marlkin and MT engines. The documentation
          > for both say that you should not exceed 8 volts.

          Aaaaahhh. Read that again. MT says not over 10 volts. Marklin, for 24
          years, said nothing over 8 volts. Marklin recently brought out a new power
          supply and now says no more than 10 volts. But mind you, the new Marklin
          pack is not a "DC" pack, its a processed waveform pack.

          > Also the MT says not to run them on pulse power.

          That is a correct statement of what the label says.

          > I own 2 Marklin power packs (the large white ones
          > that cost alot of money and aren't as good as some
          > MRC power packs that I have for HO). I put a dc volt
          > meter on them (actually I tried 2 different ones)
          > and both power packs put out a maximum of 12.5
          > volts. So what I do is only run them up to 3/4
          > maximum. Am I missing something?

          One thing at a time.

          First, if the power supply in question uses a resistor to vary the output
          voltage, and you measure its output with no load, you will see the full
          rectified output of the transformer. Why? Because if there is no current
          across the variable resistor, you will not have any voltage drop between the
          transformer and your point of measurement. It will always show you a false
          reading, no matter the knob setting. If you really want to see what it puts
          out, put a automotive stop light bulb across the output, so some real current
          flows. Then measure it.

          If the power supply is a solid state unit, measuring its output may or may
          not meaning anything.

          The problem is that almost any meter a hobbiest can afford is an RMS meter.
          That simply means the meter expects to encounter re-occuring and identical
          sine waves and give you a reading on the "heating effect" of that sine wave.
          In other words, what DC voltage would be equal in "power" to the AC waveform
          you are measuring.

          But if the supply puts out a pulse or processed waveform, and all bets are
          off as far as the meter telling you anything meaningful. I have a chart I
          picked up from an engineering magazine that gives you a multiplier if all you
          have is a "affordable" meter and a strange waveform. The multipliers run
          from 0.2 to 3.8 depending on the waveform you think you are connected to.

          > Also why does MT say not to run them on pulse (do they have coreless
          > motors)?

          The fatal enemy of any motor is heat. The purpose of any pulse supply is to
          force more enegy into the motor than it would otherwise accept at a given
          speed. While this results in a more responsive motor, the result is also
          extra heat.

          In the case of MicroTrains, their motor is totally encapsulated inside a
          metal loco weight. There is no place for the heat to go. I guess is, the
          motor runs at a safe temperature margin, but at the top of the range.
          Anything beyound that and Poof !! Neither Marklin or MicroTrains has a
          thermal path for heat to escape the motor.

          So, what should you do.

          Well, if you want to be very conservative, stay with pure DC, and insure you
          buy a pack that does not put out too much voltage (Marklin or MT). Or epoxy
          a "stop" to block the knob of a 12vdc pack so it cannot exceed the rated
          voltage. Or put diode pairs in its output leads to "kill" the extra voltage
          (that's another email).

          If you elect to try pulse, you can use solutions others have found to be
          acceptable over the years. Use some caution in taking "advice" and ask more
          than a few questions. Its YOUR train that will burn up.

          Or you can monitor the temperature of your motor every 30 seconds for an hour
          of operation to see if "this loco" and "that kind of pulse pack" is a good
          combination. Folks on the Nn3 list write about Marlin motors going up in
          smoke in 60 seconds on some exotic pulse-width type pulse packs.

          You see a lot about the 2800 packs. Folks I have a high level of confidence
          in use them. It is NOT a pulse pack, rather it has an interesting processed
          and complex output waveform. But plan to block them at less than full
          rotation. At full output, it puts out a full 12.5vdc RMS on the rails. Far,
          far too much. Measuring it with a "normal" meter is only accurate near the
          high end of the speed control. At the low end, your meter will lie, without
          a doubt.

          I actually own a "true" RMS meter. One that is not bothered by waveforms.
          Thank heavens for oil company surplus equipment auctions, otherwise I'd never
          own one ($3,000usd). Internally, it uses the input voltage to heat a
          thermocouple, then measures the temperature of the thermocouple and reads in
          "volts" of effective DC. If I can get "roundtuit" I'll hook a 2800 up to the
          meter and see where the 8 and 10 points are. You are the second person I've
          promised that to. Guess I'd better get busy.

          So what do I use. I make my own throttles from LM317 integrated circuits.
          Pure 8 VDC. Works for me. Very similiar to this circuit (not my web page):

          <A HREF="http://www2.ebtech.net/~pais/TTR_Throttle.html">TTR Throttle
          Circuit.</A>

          Clean rails, wheels and drivetrains are more important than exotic throttles
          in this scale anyway, or at least I think so.

          > I installed a Digitrax DCC in one of the
          > Marklin engines. When I run it on DCC I set the VMAX
          > to 8 volts (but don't know if I have to).

          Now I'm jealous. And yes, 8 volts is typical. Remember, DCC puts pulse
          power to the motor, not DC. Watch the heat. If you are really into DCC,
          some DCC motor overheating discussions can be found at:

          <A
          HREF="http://elnus.etech.hs-bremen.de/dccproject/measurements.html">Measuremen
          ts</A>

          and the full decoder project described at:

          <A HREF="http://elnus.etech.hs-bremen.de/dcc_decoder.html">dcc decoder </A>

          Glad to have you with us.

          Bill Kronenberger
          Houston
        • gunnar.edebrant@xxxxx.xx
          Greetings, Nothing much to add really after Bill and Jeffreys postings, but here are a few points who might be of interest: First of all: Märklin states that
          Message 4 of 7 , Dec 13, 1999
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            Greetings,

            Nothing much to add really after Bill and Jeffreys postings, but here are a few
            points who might be of interest:

            First of all: M�rklin states that the locos will cope with
            a max output of 10 V. Apparently they've tested this, at
            least it says so in the Swedish catalogue, and found that it
            won't harm your engine. I now too sure about that, but since
            you seldom run your trains on full speed it's probably not
            your main concern.

            Secondly, the only M�rklin power-pack that I have, 67011,
            (don't know the US one though) uses some modified pulsed
            way of supplying the power. From what I can remember it
            starts out using the pulsed output and then, once you turn
            the speed (knob) up, it converts to plain DC-levels.

            What really is the trouble is the wave-form of the pulsed
            output. A pure PWM (Pulse Width Modification, an output
            of max voltage hacked up into smaller parts) generates a
            lot high frequency components in the output. (I could
            probably try to explain this but since it was so long since
            I took the course in Fourier-analysis I'd probably make a
            mess of it.) Anyway, these high frequency components do not
            really like the coils in the engine and create a certain
            amount of excessive heat. The more square shaped the pulsed
            output is, the more high frequency components needed.

            Regarding the heat-dissipation, the steam locos usually have
            metal casings but are much more cramped under the shell. The
            electric/diesel engines has more "air" under the shell but
            their shell is plastic (at least on the M�rklin ones). I
            can't tell which one is the worst combination, I do not have
            the experience needed in this area...

            Myself, I use both M�rklin and CoolCrawler power-packs. Both
            works fine but since my layout isn't completed yet (will it
            ever?) I seldom get the long running hours.

            Well, these are just my 0.05$,



            Cheers GeDe, from a cold and winterlike Gothenburg, Sweden.


            Ps. The CoolCrawler uses a sine-wave pulsed output which
            generates less amount of these dreaded high frequency
            components. For me, it works great, I haven't had any
            problems running my locos on this. I know there is a web-
            site somewhere describing how to build one of these but I
            no longer have that URL in my memory/history list. Anyone
            else knows?

            ----------------------------------------------------
            Guide Datakonsult AB Volvo Penta AB
            gunnar.edebrant@... it5.edebrant@...
            Guide: +46 (0)706 840142 Penta: +46 (0)31 667988
            ----------------------------------------------------
          • BJKRONEN@xxx.xxx
            ... http://www.mcs.net/~teller/www/tractronics/articles/ccartcl/ccartcl.html From a warm, but rainy Houston. Bill Kronenberger
            Message 5 of 7 , Dec 13, 1999
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              Gunnar:

              > I know there is a web-
              > site somewhere describing how to build one of these but I
              > no longer have that URL in my memory/history list. Anyone
              > else knows?

              http://www.mcs.net/~teller/www/tractronics/articles/ccartcl/ccartcl.html

              From a warm, but rainy Houston.

              Bill Kronenberger
            • Ztrack@xxx.xxx
              ... True statement! I was once shown an unfortunate MT F7 that someone tried to run on pulse power. The shell was not warped, it actually was melted through!
              Message 6 of 7 , Dec 13, 1999
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                In a message dated 12/12/99 8:28:38 PM, jmac_han@... writes:

                >The danger, I believe, is not to the motor per se, but to the shell
                >which could possibly warp.


                True statement! I was once shown an unfortunate MT F7 that someone tried to
                run on pulse power. The shell was not warped, it actually was melted through!
                Now that took some heat.

                Rob Kluz
                Ztrack Magazine
              • M. Gottschalch
                Gunner, ... In my opinion the metal body should be the best as it acts as a heat sink to draw the heat off and let a much larger area disipate it. A principle
                Message 7 of 7 , Dec 14, 1999
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                  Gunner,

                  >Regarding the heat-dissipation, the steam locos usually have
                  >metal casings but are much more cramped under the shell. The
                  >electric/diesel engines has more "air" under the shell but
                  >their shell is plastic (at least on the M�rklin ones). I
                  >can't tell which one is the worst combination,

                  In my opinion the metal body should be the best as it acts as a heat
                  sink to draw the heat off and let a much larger area disipate it. A
                  principle used in cooling many high output electronic parts that would
                  get too hot by themselves is to add a heatsink, just a large chunck of
                  metal with fins in it to increase the heat disipation area.

                  I think that the plastic shell even though it has air space adds to the
                  heat because it does not even allow air flow to get to the motor. The
                  best heat disipation there is through the metal frame. Though the body
                  does allow heat out through the plastic, that plastic is not as good a
                  conductor of heat as metal is.

                  Manfred
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