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
  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.
     
  12. NotchHill

    NotchHill TrainBoard Member

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    I have installed servos on my layout. N scale. The servos were beneath the track about 4 to 5 centimetres (up to two inches) (foam board). There was a lot of flex with the wire on the horns moving the switches from one side to the other causing a heap of trouble. Solved the problem by purchasing Dingo Servo Mounts from the UK. Basically the servo horns move a sliding bracket with the wire moving sideways back and forth.
     
  13. videobruce

    videobruce TrainBoard Member

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    Then there was excessive movment with the horns? aka excessive travel?
     
  14. GGNInNScale

    GGNInNScale TrainBoard Member

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    I used the same method as Jdetray. It is easier to do than describe. Does not require a lot of precision. Cut a piece of the brass tube to fit from the top of the layout surface to just less than the height of the servo arm under the layout. Just punch the brass tube through the layout foam/drill if you have wood. Make the holes slightly smaller than the tube so it is a tight fit. I use K&B tubing from model shops or ACE hardware. Select an actuator wire just smaller than the ID of the brass tube. Use thin wire- flexibility is important. Bend the wire to latch into the switch throw bar hole and align with the tube. I usually put a bit of extra bend at the throw bar to prevent the wire from popping out of the switch throw bar. Feed the wire down through the tube, then using pliers, bend the wire using the brass tube edge as the break. This will give you a snug fit but easy to rotate. Then make a 45 degree bend about half way between the hole in the servo arm and the brass tube, then bend the wire up at the servo arm to go through the hole in the servo arm. I bend the wire a bit above the servo arm to make sure it does not come out. This will give you a bit of flexibility during actuation. I then put caulk on the tube where it comes out of the bottom of the layout board. Let it dry for at least 24 hours before actuation/testing. I will try to put some pictures on when I return home.
     
    Sumner likes this.
  15. GGNInNScale

    GGNInNScale TrainBoard Member

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    I took some pictures of one of the servo mounts for a PECO curved switch. This is a switch in a hidden area under a mountain. I made this one to drive the points with a central pivot. I made others with a side pivot, depending on the location on the layout. You can also see some of the wiring modifications needed to keep a PECO switch working without requiring constant cleaning- main power red and black, and the fine wires that connect the blades to the power feeds to jumper the hinge connection. The only insulators needed are at the two point rails to the left out of the picture. This servo is mounted on a small plywood frame, then caulked to the foam. I added some screws into the foam- actually just put some caulk in a hole, then inserted the screw for additional strength. After it dries it is more than sufficiently strong for a 5 gram servo. It is controlled by an Arduino UNO along with two other relays on the same UNO. s1.jpg
    s2.jpg
     
    Sumner and BNSF FAN like this.

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