No announcement yet.

Minnesota Twins

  • Filter
  • Time
  • Show
Clear All
new posts

  • #46
    I am going to build another one (lessons learned and all that) trying some different motors...and YES... I will reverse the crowns to the outboard sides.


    • #47

      Thanks for the props on the soldering thread. I looked back at it just now and saw that all of my photos are missing -- broken links from the SCI port-over.

      I guess I'm going to have to restore those photos myself. And also to the other sticky threads I've created or contributed to. Something to do when I'm in the mood to do mind-numbing repetitive work. And yes, it does happen to me.

      Ed Bianchi


      • #48
        EB: I'd like to read MM's opinion on how well controlled the rear axle is, given its unconventional inboard bushings.

        Of course Ed, you know Im always I'm happy to toss it around a bit. The center "bushing" in this case works as it should, with no peculiar behavior exhibited at this point in time. After a lifetime of being a fixer, some things just feel right to the touch; and at our venerable ages, we most certainly dont fix things that aint broke.

        My additional observations will continue to evolve; as I ponder all the fun I had playing with Jeff's build. Like any other axle the Twinns rear axle will take a "set" and locate itself within the provided tolerance, based on the force and direction with which it is applied.

        In the case of the Twinns, there was more clearance between the axle and the rear axle bushing than I personally would like to see, but I am often proved to be an idiot by what "will" run flawlessly in spite of my observations and preferences. What I found interesting was that the simultaneous, outboard, dual motive force kept the axle firmly planted across the center. I also consider that; for what the design gives up in support on the ends, the available surface area of the centered journal is easily four times what one normally runs in a typical two bushing conventional arrangement. My new take is open to the idea that any static axle "walk" initially exhibited, is "set" flat across the center journal when loaded on either end. Submission by force!.

        EB: Also, there is a brass post mounted at the rear of the chassis. I suspect its function is to keep the body from contacting the rear tires. True or not?

        I too assumed it was a standoff at first, but it's a bit short. Notably the chassis features the tried and true pin receptacles, 2 per side.

        EB: The dual motor drive might result in more powerful braking. Zat so?

        No sir! Once the platform was track sorted, the Twinns would pipe down the track on throttle, and glide down smoothly off throttle. As mentioned earlier, the finger roll was silky smooth and feather light, like that of a Mega Gee Plus, if you are familiar with them. They are completely devoid of any cammed feeling like armature poles clunking through their rotation when Polys or Neos are present for a finger roll. Additionally, if a mini can isnt snatching tools and whatnot off the bench, they arent poly or neo mag. No need to open them to look. No mas, because there's no gauss.

        Braking is what you'd expect with an easy roller motor: Essentially "flywheel over friction" due to little or no magnetic lug at the de-energized armature poles. With two armatures and middling ceramic magnets, there is a bit more flywheel effect than I expected. Nothing a dynamic braking circuit wouldnt fix.

        Interestingly, with the two motors, there is an impressive amount of on throttle flux assist when cornering, likely due to the greater combined field being directly exposed to the rail via the drop through configuration. At 1.60", with RC minicans, at 18v: one should be able to punch the tail out at will, almost anywhere you want. Such was not the case. In fact the Twinns resisted my attempts at sideways mayhem with considerable attitude, until the tires were sufficiently fuzzed up. I noted the combined field effect when I had the chassis on the track, tail slightly up for wiping the tires. I squeezed the throttle up; and immediately felt rear assembly suck down like the old AMRAC chassis, that would pinch your finger, albeit not as aggressive..

        I could blather on a while about this and that, but FWIW, thats my two cents Ed, and a penny back in change
        Last edited by model murdering; 08-13-2019, 09:29 PM.


        • #49

          Thank you much! And here is a 1/50th scale dollar for your troubles!

          Ed Bianchi


          • #50
            Could you dumb this down for us mere mortals?? ;-)

            there is an impressive amount of on throttle flux assist when cornering, due to the greater combined field being directly exposed to the rail via the drop through configuration.


            • #51
              When the motor is energized the armature becomes another electro magnet between the two already existing permanent magnets. When you have the juice on, the total magnetic field intensifies. The more juice, the stronger the elctro magnet becomes, and thus more attraction. With the juice off, the fields arent combined. In the case of your Twinns, the effect is doubled.

              The higher you rev, the grabbier it gets.


              • #52
                Thank you!


                • #53
                  Per Ed's suggestion...reversing the positioning of the two crown gears, having them inboard of the pinions instead of outboard. And trying a couple of different motors.