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Maintaining Twin-Coil switch motors & Eshleman Turnout Links

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  • Maintaining Twin-Coil switch motors & Eshleman Turnout Links

    Back in 2009 I built a 9-track staging yard using Homasote on plywood and commercial track and turnouts.

    Locating 3-way turnouts

    I mounted a mix of NJI, Kemtron and ?AHM? twin-coil switch machines under the table, connected to the throw bars with Eshleman's Turnout Links (also recycled).

    Underside of staging yard

    Then I built a diode matrix for 1-button operation of the left (layout west) throat:Diode side of matrix board

    It's now been in service 12 years, but the turnout links and most of the switch machines were manufactured before 1974.

  • #2
    The first problem to appear was in the diode matrix. I had used some tinned buss wire I had around (likely dump pickings from scrapped Hytron test rigs thrown out in the 1970s). It turned out to be tinned with really crummy solder.

    Back of diode matrix board

    Three of the original buss wires remain, the rest were replaced with plain or insulated copper, using quality 60/40 solder in 2018. No problems with it since then.


    • #3
      Years ago, some of the ladder turnouts had started to get a little balky. I'd have to push a button two or three times to get one or another turnout on a route fully thrown. And if the points stopped moving at the wrong point, they'd short the DCC power. Switch power was independent of DCC, so the button could be pushed as many times as necessary. But it left me operating the staging turnouts so visiting operators didn't have to deal with its quirks. After Mill City 21's two op sessions, I decided it was time to clear out under there, crawl in and not let up until it was fixed. Here's what it looks like today:

      Click image for larger version

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      The red twin-coil units are 50 year old Kemtron products. The blue one is NJ International, a Kemtron clone imported in the 1990s. I think I got the beige machine at the upper right from AHM, IHC or some company in that orbit. No markings whatsoever.
      Attached Files


      • #4
        Exploring the turnouts from above, I found several turnouts didn't have good spring return action when I pushed the points out of position. I made a list and continued underneath.

        I found one wire that wasn't well soldered to its machine's lug. Easy fix.

        Then I found a Kemtron machine with a bind near the mid-point of its action. I fiddled with it a bit using screwdrivers and pliers, but nothing acted like it had gotten bent. So I got my box of old Kemtron machines. Most came from Hub members who had switched technologies, and some baseplates were rusty. Several of these had the same bind mid-motion. I thought about lubrication, but not something which would dry to gum. I got my squeeze bottle of lock graphite (Kadee Greas-Em should work too) and applied a good puff into each end of the solenoid tube. Problem cured, even on old rusty machines. Back underneath, I puffed all the machines.

        Back on top, I noticed a funny reflection off the smooth top of an Eshleman shaft. It was turning but its lever arm wasn't. Take it apart, take shaft and arm to the vise, re-solder, making sure solder flowed into the joint from both sides. Reassemble, adjust,

        Finally, I thought about how to reduce friction under the throw bars. I'd painted the top of the Homasote but I hadn't gouged out the area between the headblocks, so the throw bar was riding on the Homasote. I found a small screwdriver whose blade was about the width of a throwbar. I slid it under each end of each throwbar and pulled it out while pressing down firmly. The Homasote compressed enough to clear the throwbar. If the Homasote swells again, I'll make a little hook scraper out of a street sweeper blade and actually excavate a cavity down there.

        So now that end of the staging yard is working better than it has since 2013. I'll see if that lasts through an op session in early November...


        • #5
          Wow! This is what Knowledge and Patience can produce! Far better results than I can get here in less than two years! Congratulations!

          in Michigan


          • #6
            Excellent diagnostic and repair skills. Sometime that's all it takes. Thanks for posting.

            New York, Vermont & Northern Rwy. - Route of the Black Diamonds