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  • #31
    I don't think anyone is whining or whinging, they seem quite happy with the status quo.

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    • #32
      Originally posted by RichD View Post
      I still have not found out if the HOST motors are N20s.
      HOST motors are M20s. Most Gravity builders, including myself, are using the M20 motor. The N20 is ok for an inline setup, but I prefer the M20 or M10 for a siderwider or anglewinder setup.

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      • #33
        N20's? M20's? Now I'm confused.

        Is there somewhere to find a definition for what constitutes an N20 or an M20? And are there any other such standards?

        Ed Bianchi

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        • #34
          Okay, I found some information online...

          An M20 can is 15mm long, 10mm wide and 8mm high.

          An N20 can is 15mm long, 12mm wide and 10mm high.

          So the N20 is a larger motor -- larger by 2mm in width and height. Both motors have the classic can geometry, with two flat sides and two round sides.

          There is also an M10 motor, with the same width and height as an M20, but a shorter 12mm long can.

          Shaft diameters seem to be 1mm as a standard. Shaft length can vary. There are some of these motors with dual shafts, that is, the armature shaft extends out both ends of the motor.

          There also seem to be "dash" designations for these motors. "-ULV", "-LV", "-MV", "-HV" and "-UHV". At a guess these stand for "Ultra-Low Voltage", "Low Voltage", "Medium Voltage", "High Voltage", and "Ultra-HIgh Voltage". Again, that is a guess.

          Aside from the voltage rating of the motor -- determined by the armature winding -- I haven't yet seen any nomenclature that calls out the internals of these motors. Specifically, the kinds of brushes or magnets. I do know you can get N20 motors with carbon brushes and rare-earth magnets, which I consider to be the premium setup. Some N20 motors come with holes in the can to provide cooling. But there are N20 and M20 motors that come with "precious metal" brushes. I consider these to be inferior to carbon brushes. I believe carbon brushes can stand up to surge-currents better, and have a longer service life. But that is just my impression, based on a few experiences with "precious metal" brushes.

          I don't know if there are variations in the types of rare-earth magnets available, or what their characteristics might be.

          I found some test results listed online for a number of different micromotors. (See the tables attached to the link, below.)

          https://www.rcgroups.com/forums/show...r-Micro-Motors

          The tests at 7.0 volts are the most relevant for us. The motors I have been using are rated at 7.2 volts, but seem perfectly happy on 12.0 volts.

          The power and efficiency ratings of M20 and N20 motors, as listed, seem to be very close. It is very possible both M and N motors could compete in the same class. The slightly lower center of gravity of the M motors might compensate for their potentially lower power (due to a smaller diameter armature.)

          I'm sure there is more to learn here. But this is a start.

          Ed Bianchi
          Last edited by HO RacePro; 04-01-2019, 08:26 AM.

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          • #35
            The M20 motors I am using have arms that are 3.5 - 3.8 ohms. M20 motors do not have carbon based brushes. They are metal fingers. There are neo and rare earth magnets available, but work needs to be done to match motor to magnets.

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            • #36
              I had a nice chart for this type of motor filed away someplace, I have not been able to find it. There is lots of info here: https://www.mabuchi-motor.com/produc...ignations.html
              M or N would refer to the armature diameter and 20 would refer to the size of the case.
              Here is an FF-N20: https://product.mabuchi-motor.com/re...l?t=1554132633 and here is an FF-M20: https://product.mabuchi-motor.com/re...l?t=1554132633
              For motors with carbon brushes the numbers would be FC-N20 and FC-M20.

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              • #37
                Originally posted by RichD View Post
                For motors with carbon brushes the numbers would be FC-N20 and FC-M20.
                If you find a M20 with carbon brushes, let me know. I don't think they exist.

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                • #38
                  Possibly not, a Google search did not turn up anything, I did find FF-M20 motors.

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