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Re: [Z_Scale] MTL F7 Motor Dis-assembly for Cleaning

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  • Loren
    Glen, You are definitely the whiz bang of the F7. Your advice, if followed, can certainly prolong the life of the work horse of work horses. Thanks for
    Message 1 of 8 , Oct 4, 2009
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      Glen,
      You are definitely the whiz bang of the F7. Your advice, if followed, can
      certainly prolong the life of the work horse of work horses.
      Thanks for passing this valuable info along to the masses. This bit of
      advice is invaluable.
      Loren

      ----- Original Message -----
      From: "zeeglen" <glen@...>
      To: <z_scale@yahoogroups.com>
      Sent: Sunday, October 04, 2009 12:00 AM
      Subject: [Z_Scale] MTL F7 Motor Dis-assembly for Cleaning


      > As we all know, production of the venerable MTL F7 has been discontinued.
      > This locomotive is a workhorse that can last for many years with periodic
      > maintenance. Here is a motor cleaning tip that might help F7 owners to
      > keep their irreplaceable units running longer and better.
      >
      > Am repairing an F7 that looks about 20 years old, the worm gears are metal
      > (not the later Delrin), the motor lacked the commutator inspection hole in
      > the top, and the motor commutator was so crudded up with dirt that the
      > plastic shell had melted and deformed from motor overheating.
      >
      > The crud was so old and hardened that the usual cleaning method (running
      > the motor while submerged in rubbing alcohol) did not work. I Tried
      > several times and the measured electrical current draw remained twice as
      > high as it should have been. Started thinking that I would have to tell
      > the loco owner that this was not a good candidate for the intended DCC
      > decoder installation.
      >
      > Then, feeling adventurous, I discovered that it is possible to
      > dis-assemble the motor for better cleaning access, and more importantly
      > that it can be re-assembled without damage. First mark the top of the
      > metal frame for re-assembly with the magnets in the same position,
      > otherwise the motor might run backwards. Then remove the brush holders.
      > Note the rear plastic piece has an upper (narrow) and lower (wider) notch
      > at the brusholders, the terminal tabs fit into the lower wider notch on
      > re-assembly.
      >
      > Pull off the spur gears and motor mounts, then pry the metal frame apart
      > just enough to release the plastic end piece from the raised shoulders of
      > the brush holder holes. Remove the plastic end piece. Now the rotor can
      > be removed (do not lose the fiber washers on the rotor shafts) and the
      > commutator is wide open for inspection and cleaning.
      >
      > I saw two bands of hardened crud circling the commutator on each side of
      > the brush contact area, and crud still stuck in the 5 commutator slots.
      > This crud is electrically conductive and shorts the commutator segments
      > together, resulting in excessive electrical current and heating. With the
      > commutator accessible, was now easy to scrape off the circling crud bands
      > and clear the slots with a toothpick sanded to a thin edge.
      >
      > After re-assembly with a new set of brushes and shaft bushings re-lube,
      > the current draw is back to normal. Might get another 20 years out of
      > this motor...
    • Jim Glass Sr
      If I remove the shell and throw the total mechanism in an ultrasonic cleaner, what would be the outcome? 1. Any damage to unknown parts? 2. Would cleaning be
      Message 2 of 8 , Oct 20, 2009
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        If I remove the shell and throw the total mechanism in an ultrasonic cleaner, what would be the outcome?



        1. Any damage to unknown parts?



        2. Would cleaning be complete and effective?



        3. What would be safest solution to use in the cleaner?



        4. Any other caveats?

        JimGl Redmond, WA





        To: z_scale@yahoogroups.com
        From: glen@...
        Date: Sun, 4 Oct 2009 07:00:41 +0000
        Subject: [Z_Scale] MTL F7 Motor Dis-assembly for Cleaning





        As we all know, production of the venerable MTL F7 has been discontinued. This locomotive is a workhorse that can last for many years with periodic maintenance. Here is a motor cleaning tip that might help F7 owners to keep their irreplaceable units running longer and better.

        Am repairing an F7 that looks about 20 years old, the worm gears are metal (not the later Delrin), the motor lacked the commutator inspection hole in the top, and the motor commutator was so crudded up with dirt that the plastic shell had melted and deformed from motor overheating.

        The crud was so old and hardened that the usual cleaning method (running the motor while submerged in rubbing alcohol) did not work. I Tried several times and the measured electrical current draw remained twice as high as it should have been. Started thinking that I would have to tell the loco owner that this was not a good candidate for the intended DCC decoder installation.

        Then, feeling adventurous, I discovered that it is possible to dis-assemble the motor for better cleaning access, and more importantly that it can be re-assembled without damage. First mark the top of the metal frame for re-assembly with the magnets in the same position, otherwise the motor might run backwards. Then remove the brush holders. Note the rear plastic piece has an upper (narrow) and lower (wider) notch at the brusholders, the terminal tabs fit into the lower wider notch on re-assembly.

        Pull off the spur gears and motor mounts, then pry the metal frame apart just enough to release the plastic end piece from the raised shoulders of the brush holder holes. Remove the plastic end piece. Now the rotor can be removed (do not lose the fiber washers on the rotor shafts) and the commutator is wide open for inspection and cleaning.

        I saw two bands of hardened crud circling the commutator on each side of the brush contact area, and crud still stuck in the 5 commutator slots. This crud is electrically conductive and shorts the commutator segments together, resulting in excessive electrical current and heating. With the commutator accessible, was now easy to scrape off the circling crud bands and clear the slots with a toothpick sanded to a thin edge.

        After re-assembly with a new set of brushes and shaft bushings re-lube, the current draw is back to normal. Might get another 20 years out of this motor...










        [Non-text portions of this message have been removed]
      • zeeglen
        ... This question would be better answered by those fortunate few who own ultrasonic cleaners. Some swear by them, and I do recall someone experienced with
        Message 3 of 8 , Oct 20, 2009
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          --- In z_scale@yahoogroups.com, Jim Glass Sr <Berjimgl@...> wrote:
          >
          > If I remove the shell and throw the total mechanism in an ultrasonic cleaner, what would be the outcome?
          >
          > 1. Any damage to unknown parts?
          > 2. Would cleaning be complete and effective?
          > 3. What would be safest solution to use in the cleaner?
          > 4. Any other caveats?
          >

          This question would be better answered by those fortunate few who own ultrasonic cleaners. Some swear by them, and I do recall someone experienced with their use (Loren? Karin?) long ago mentioning that a professional grade jeweller's ultrasonic cleaner is far better than the hobbyist type.

          That said, my thoughts FWTW:

          1 and 3. The chassis black paint would probably be removed if rubbing alcohol is used as the cleaning solvent. Other cleaning solutions? Don't know.

          2. While a motor alone (out of the chassis) would probably come clean if the crud is not hardened, cannot say if old hardened crud would be removed. If the motor is still enclosed in the assembled chassis the ultrasonic vibration might not be as effective.

          The main reason that I've never invested in an ultrasonic cleaner is that much of locomotive overhaul consists of removing dust and lint fibers and pet hairs that are multi-turn wrapped around axles and worms. These must be removed by scrubbing with a toothbrush/alcohol and unwinding with tweezers. I do not believe that an ultrasonic cleaner can cope with this type of cleaning. So will say it again - vacuum your tracks monthly, weekly even better.

          Other crud (old lube, fine dust) is said to come clean very nicely with an utrasonic cleaner. But the toothbrush/alcohol is effective too, especially for those who do not own an ultrasonic cleaner.

          4. Just guessing, but you probably do not want contaminent residue floating around and getting into the couplers. If you bathe a sideframe/coupler assembly, remove wheels and truck castings first and use a fresh shot of alcohol.


          Now let's hear from those with ultrasonic cleaners who are far better qualified to comment...
        • Loren
          Glen and Jim, Yes, the professional ultrasonic is the best way to go, but unless you are using it all the time, it isn t worth the money. Glen, I think all you
          Message 4 of 8 , Oct 20, 2009
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            Glen and Jim,
            Yes, the professional ultrasonic is the best way to go, but unless you are
            using it all the time, it isn't worth the money.

            Glen, I think all you said is most likely true, though I've never used one
            on trains. Sure works great for getting all the gunk out of watch
            bands..:o)
            Sometimes you can even use a steam cleaner to blow crud out of mechanisms
            after the crud is loosened by soaking or ultrasonic.
            Be sure to dry the mechanisms thoroughly though (air hose) or you may end
            up with rust?

            Little info from someone who doesn't really know too much about the issue,
            Loren

            ----- Original Message -----
            From: "zeeglen" <glen@...>
            To: <z_scale@yahoogroups.com>
            Sent: Tuesday, October 20, 2009 8:07 PM
            Subject: [Z_Scale] Re: MTL F7 Motor Dis-assembly for Cleaning


            > --- In z_scale@yahoogroups.com, Jim Glass Sr <Berjimgl@...> wrote:
            >>
            >> If I remove the shell and throw the total mechanism in an ultrasonic
            >> cleaner, what would be the outcome?
            >>
            >> 1. Any damage to unknown parts?
            >> 2. Would cleaning be complete and effective?
            >> 3. What would be safest solution to use in the cleaner?
            >> 4. Any other caveats?
            >>
            >
            > This question would be better answered by those fortunate few who own
            > ultrasonic cleaners. Some swear by them, and I do recall someone
            > experienced with their use (Loren? Karin?) long ago mentioning that a
            > professional grade jeweller's ultrasonic cleaner is far better than the
            > hobbyist type.
            >
            > That said, my thoughts FWTW:
            >
            > 1 and 3. The chassis black paint would probably be removed if rubbing
            > alcohol is used as the cleaning solvent. Other cleaning solutions? Don't
            > know.
            >
            > 2. While a motor alone (out of the chassis) would probably come clean if
            > the crud is not hardened, cannot say if old hardened crud would be
            > removed. If the motor is still enclosed in the assembled chassis the
            > ultrasonic vibration might not be as effective.
            >
            > The main reason that I've never invested in an ultrasonic cleaner is that
            > much of locomotive overhaul consists of removing dust and lint fibers and
            > pet hairs that are multi-turn wrapped around axles and worms. These must
            > be removed by scrubbing with a toothbrush/alcohol and unwinding with
            > tweezers. I do not believe that an ultrasonic cleaner can cope with this
            > type of cleaning. So will say it again - vacuum your tracks monthly,
            > weekly even better.
            >
            > Other crud (old lube, fine dust) is said to come clean very nicely with an
            > utrasonic cleaner. But the toothbrush/alcohol is effective too,
            > especially for those who do not own an ultrasonic cleaner.
            >
            > 4. Just guessing, but you probably do not want contaminent residue
            > floating around and getting into the couplers. If you bathe a
            > sideframe/coupler assembly, remove wheels and truck castings first and use
            > a fresh shot of alcohol.
            >
            >
            > Now let's hear from those with ultrasonic cleaners who are far better
            > qualified to comment...
          • Karin E. Snyder
            Hi Glen, you re correct. It is not worth buying an ultrasonic cleaner if your sole purpose is to clean motors. And if you DO have one I want to add this bit
            Message 5 of 8 , Oct 21, 2009
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              Hi Glen, you're correct. It is not worth buying an ultrasonic cleaner if
              your sole purpose is to clean motors. And if you DO have one I want to add
              this bit of advice; do not just set your parts on the steel bottom of the
              cleaner. Always use a plastic basket or flat piece of plastic so that you
              don't end up with abrasions on your shells or engine parts. It WILL happen.
              Most cleaners come with a plastic tray or basket, just be sure to use it.
              I suspend my items whenever possible. I have never used alcohol as a
              cleaner but ammonia diluted with water and some folks use "Mr. Clean" or
              Formula 409 diluted. One of these days I will get mine out and experiment.
              I'm sure we have a few gunked up Marklin 0-6-0's around here!!! These days
              a decent ultrasonic cleaner can be had for a very good price on that auction
              site. If someone wants me to experiment sooner than later, so that they can
              decide if they really want one, just contact me and I'll do it sooner.
              Karin

              >This question would be better answered by those fortunate few who own
              ultrasonic cleaners. Some swear by them, and I do recall someone
              experienced with their use (Loren? Karin?) long ago mentioning that a
              professional grade jeweller's ultrasonic cleaner is far better than the
              hobbyist type.


              [Non-text portions of this message have been removed]
            • sj_baz_man
              Glen, what do you consider good current draw ? What is the best and typical that you have seen ? Jeff SF Bay Area Z
              Message 6 of 8 , Oct 23, 2009
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                Glen,

                what do you consider good current draw ? What is the best and typical that you have seen ?

                Jeff
                SF Bay Area Z


                --- In z_scale@yahoogroups.com, "zeeglen" <glen@...> wrote:
                >
                > As we all know, production of the venerable MTL F7 has been discontinued. This locomotive is a workhorse that can last for many years with periodic maintenance. Here is a motor cleaning tip that might help F7 owners to keep their irreplaceable units running longer and better.
                >
                > Am repairing an F7 that looks about 20 years old, the worm gears are metal (not the later Delrin), the motor lacked the commutator inspection hole in the top, and the motor commutator was so crudded up with dirt that the plastic shell had melted and deformed from motor overheating.
                >
                > The crud was so old and hardened that the usual cleaning method (running the motor while submerged in rubbing alcohol) did not work. I Tried several times and the measured electrical current draw remained twice as high as it should have been. Started thinking that I would have to tell the loco owner that this was not a good candidate for the intended DCC decoder installation.
                >
                > Then, feeling adventurous, I discovered that it is possible to dis-assemble the motor for better cleaning access, and more importantly that it can be re-assembled without damage. First mark the top of the metal frame for re-assembly with the magnets in the same position, otherwise the motor might run backwards. Then remove the brush holders. Note the rear plastic piece has an upper (narrow) and lower (wider) notch at the brusholders, the terminal tabs fit into the lower wider notch on re-assembly.
                >
                > Pull off the spur gears and motor mounts, then pry the metal frame apart just enough to release the plastic end piece from the raised shoulders of the brush holder holes. Remove the plastic end piece. Now the rotor can be removed (do not lose the fiber washers on the rotor shafts) and the commutator is wide open for inspection and cleaning.
                >
                > I saw two bands of hardened crud circling the commutator on each side of the brush contact area, and crud still stuck in the 5 commutator slots. This crud is electrically conductive and shorts the commutator segments together, resulting in excessive electrical current and heating. With the commutator accessible, was now easy to scrape off the circling crud bands and clear the slots with a toothpick sanded to a thin edge.
                >
                > After re-assembly with a new set of brushes and shaft bushings re-lube, the current draw is back to normal. Might get another 20 years out of this motor...
                >
              • zeeglen
                ... If I recall correctly, with the motor removed from the locomotive about 120 mA from a pure DC source at 9 volts (a battery). I used to have data at
                Message 7 of 8 , Oct 25, 2009
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                  --- In z_scale@yahoogroups.com, "sj_baz_man" <sjbazman49@...> wrote:
                  > what do you consider good current draw ? What is the best and typical that you have seen ?
                  >

                  If I recall correctly, with the motor removed from the locomotive about 120 mA from a pure DC source at 9 volts (a battery). I used to have data at various DC and pulse voltages with the motor in and out of the loco, was lost long ago after a computer crash.

                  The problem with trying to make current measurements is the meter's response to pulsed current. Most DMMs are average responding, some are true RMS responding. If the power pack sources sine pulses, your reading will vary.

                  I make current measurements on an oscilloscope using a MRC Tech II 1400 Railpower that outputs 60 sine pulses per second. At 4 volts peak, the current sould be no more than 300 mA peak for a loco on the track. Useless answer for those who want to use a DMM.

                  Give me a few days, will make some measurements using both pure DC and 60 pulses per second as measured on a typical average responding digital multimeter from the hardware store. This should serve as an approximate set of numbers.
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