Servo mounting & installing the piano wire in N Scale

videobruce Sep 18, 2021

  1. videobruce

    videobruce TrainBoard Member

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    It seems that the typical way to mount servos is to feed the piano wire up from the horn to the throw rod of the turnout. I guess that is easier in HO scale, but just how can one find the hole in the throw rod in N scale under the table??

    Is there any reason why the procedure can't be reversed and thread the piano wire down from above first and then thread in thru the hole on the servo base, then the horn arm before one secures the mount to the underside of the layout?
     
  2. videobruce

    videobruce TrainBoard Member

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    No one uses servos here?
     
  3. Shortround

    Shortround TrainBoard Member

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    Try posting your request in the 'N' section. I don't have any. Only manual.
     
  4. videobruce

    videobruce TrainBoard Member

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    But this isn't a scale issue, under the table is basically the same with either HO or N.
     
  5. jdetray

    jdetray TrainBoard Member

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    Bruce -

    The method I use for throwing turnouts with servos employs a bellcrank actuator. I have used this method through up to 6 inches of scenery and benchwork.

    Servo_Actuator9.png

    Here is what it looks like on the bottom of the layout. Although the subroadbed for my layout is XPS foam, I laminated 1/4-inch plywood to the bottom of the foam to provide a solid surface for mounting servos, circuit boards, and other items. The servo is mounted with hot glue and further secured with a styrene strap. I later added a wood screw to each end of the styrene strap for even MORE security.

    The music wire has to be pulled slightly downward to reach the servo arm. This has the added benefit of applying a small amount of downward tension on the wire, preventing it from sliding upward in the brass tubing, which might cause the wire to slip out of the hole in the turnout's throwbar.

    upload_2021-9-28_17-45-43.jpeg

    On the topside of the layout, the linkage looks like this.

    turnout_linkage3.png

    Once the area is scenicked, the ballast is added, and a (non-operating) switch stand added, the music wire and brass tubing pretty much disappear.

    Turnout_Scenicked_3.png

    Another post, from forum member gary60s, also illustrates the bellcrank linkage. I had not seen his post when I devised essentially the same sort of system for my layout. His diagrams are much nicer than mine:
    https://www.trainboard.com/highball...linkage-thread-with-images.88824/#post-952770

    I'll be happy to answer any questions.

    - Jeff
     

    Attached Files:

    Last edited: Sep 29, 2021
    Shortround likes this.
  6. Shortround

    Shortround TrainBoard Member

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    Thanks for the information and the link.
     
  7. videobruce

    videobruce TrainBoard Member

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    Thanks for the post, but I've seen that before.
    I just can't see how doing all those precision bends for the wire is easier that just doing a single right angle from the top down. Again, especially in N scale which that is not.
     
  8. jdetray

    jdetray TrainBoard Member

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    The single best feature of the method I describe in my post above is that NO measuring is required. Although my diagram shows certain dimensions, that's simply to provide a sense of scale. When I actually install a servo and its linkage, I find no need to measure anything.

    - Jeff
     
  9. videobruce

    videobruce TrainBoard Member

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    Measure or not, all of those bends are are real challenge. It's hard enough to bend piano wire once for a '90' at the very end, but there are 3 of those too deal with and that brass tube.

    AFA the hole for a conventional install, that rod above the table is just as noticeable.
     
  10. Shortround

    Shortround TrainBoard Member

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    Besides getting through the tube with the bends.
     
  11. COHiker06

    COHiker06 TrainBoard Member

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    Work from the restricted end back. My RC aircraft connections are formed first for and attached to the surfaces then laid in to the servos/horns where I have more room to work and make adjustments.
     

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