Foam and Servos....

Sumner Oct 30, 2019

  1. Sumner

    Sumner TrainBoard Member

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    If any of you are using foam board and also servos to actuate your turnouts I'd be interested in how you are mounting the turnout servos in the foam. If you have any links to someone else doing this that would also help.

    I have drawn up a jig to position a servo mount under 1/2" plywood that should make positioning and mounting the servos under the turnout fairly easy but haven't really come up with something that would be easy and repeatable using 1"-3" of foam.

    I'd like to be able to get to the servos easily in the future in case they need replaced. I'm using FastTrack hand laid turnouts and the SG-90 servos.

    Thanks,

    Sumner
     
  2. sidney

    sidney TrainBoard Member

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    you can go to model air plane sites and get pretty good info on mounting servos to foam. rc plane guys do it all the time. i used to build RC Planes. there is great info on that kinda stuff. go check out an RC PLANE forum ...
     
  3. JMaurer1

    JMaurer1 TrainBoard Member

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    Servo tape...good servo tape. Use it for attaching steering servos in cars and while I also usually use a backup (mount) the tape is usually strong enough and can be removed (with some effort) if it needs to be.
     
  4. Sumner

    Sumner TrainBoard Member

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    Thanks. I probably didn't word my request in the best manor.

    I've seen ways to mount a servo generically to foam. I'm interested in mounting them under a turnout in foam thicker than an inch using mounts similar to what people have made for using under plywood....

    https://www.google.com/search?q=ser...7cblAhUSOH0KHSeED6UQ_AUIEygC&biw=1280&bih=552

    Problem is I don't see those mounts working for thicker foam. I've seen some that are just buried under the foam with hot glue but it looks like down the road if you had to service or replace them it would be a mess.

    I'm surprised that with the number of people now using foam board that there hasn't been more posted about using turnouts with it that are servo controlled. I did find the following and it looks like the servo might be under foam about an inch thick. Maybe this is about the best I can hope for. I do have some foam, servos and the rest I need to try this out so guess that is the direction I'll take.

    Sumner
     
  5. freddy_fo

    freddy_fo TrainBoard Member

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    I've been looking at these servos with mounts and they look like they could work through a couple inches of thickness. Without having one in hand I can't tell for sure but I'm betting you could rig up something similar. If you needed a longer wand then move the servo side of it to the inner hole of the servo arm to regain leverage and reduce movement of a longer wire.

    [​IMG]
     
    Sumner likes this.
  6. Sumner

    Sumner TrainBoard Member

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    Thanks, whose bracket is that? Good idea about being able to move the wand in for less travel needed with greater thickness,

    Sumner
     
  7. freddy_fo

    freddy_fo TrainBoard Member

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    Tam Valley Depot on this page if you scroll down a little.
     
  8. Sumner

    Sumner TrainBoard Member

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    I tried a servo mounted on 1/2" plywood with 1" foam on top and didn't like how it was working. Felt the turnout had too much leverage on the servo. Might just be that some of the hand laid ones I've made take more force than say a Peco or Atlas to throw. Guess I'll stick with trying to cut and use 1/2" plywood for where the track is and foam on either side if I need relief.

    I'm still interested though if someone is having luck with the servos on hand laid turnouts with the servo mounted 1 1/2" or more below the turnout,

    Sumner
     
  9. vasilis

    vasilis TrainBoard Member

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  10. Sumner

    Sumner TrainBoard Member

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    Thanks for the links. There is a lot of math and theory there. I'd probably like to see some examples of what has been built and is working using the ideas presented there.

    I need to make a lot of these so need the mount to be fairly simple and easy to make and locate under the trackwork. I've made one mount that is pretty similar to others I've seen in action and think I've come up with a jig that will make it pretty quick and easy to place the mount under the turnout so that it is centered,

    Sumner
     
  11. vasilis

    vasilis TrainBoard Member

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    No problem. Forget the maths, the excel sheet is very simple. The excel sheet can help you to find the wire size and choose the lever lengths and more things such the force on the turnout to avoid damages, the angle of the servo movement and ...
    A short lever (from pivot to the servo) and demands a bigger wire diam and more force from servo to keep the position.
    Anyway
    The universal mounting under a variable and thick subroadbed is not exist without problems. A solution in the case of a thick foam is to have the mount in the foam (pocket) at the side of the turnout or under the throwbar. Another, more universal solution is
    https://www.trainboard.com/highball/index.php?resources/turnout-control-linkage.126/
    Keep in mind that short movements (small angles between the end positions) can hurt the servo.
     
  12. Sumner

    Sumner TrainBoard Member

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    Thanks, I've come to the conclusion, at least for now, that I'll probably stick with 1/2" plywood and roadbed for now where the track is to make mounting more universal and easier to do at my age. As you mentioned different thicknesses are going to warrant different solutions.

    Sumner
     
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  13. bill pearce

    bill pearce TrainBoard Member

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    I have used Tortoise machines mounted to plywood, so this is mostly a guess. I think I've seen this solution in magazines. A piece of 1/4 inch masonite or plywood is recessed into the foam with and ample margin around the edges, to hold a servo or stall motor. the foam under the wood is cut out, and the motor is screwed into place. Should work for all kinds of under layout systems.
     
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  14. jdetray

    jdetray TrainBoard Member

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    Hi Sumner -

    I use a bellcrank method. I've used this through as much as 6 inches of foam subroadbed and scenery.

    [​IMG]

    Here is what it looks like on the bottom of the layout. I glued 1/4-inch plywood to the foam. The servo is mounted with hot glue.

    [​IMG]

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

    [​IMG]

    With some ballast and scenery, it doesn't look bad (turnout linkage in lower left):

    [​IMG]

    - Jeff
     
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  15. Sumner

    Sumner TrainBoard Member

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    Thanks Jeff. I've looked at those pictures before and have considered that method. I'll setup one or two on a test piece of plywood/foam and see what I think. I appreciate the input,

    Sumner
     
  16. bill pearce

    bill pearce TrainBoard Member

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    WOOW!! it looks awful before the ballast, but after it's nolonger a sore thumb. But tell me, what is the advantage to the servo over a Tortoise? With the servo, how do you feed the frog?
     
  17. jdetray

    jdetray TrainBoard Member

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    For me, a big advantage of the servos is their very small size. They are only an inch high and will fit in places where Tortoises won't. I also like the fact that no soldering is required. You use standard servo extension cables to hook everything together. I find this convenient.

    I'm familiar with the servo system from Tam Valley Depot. Using their Octopus board (controls 8 turnouts) and other components, the cost is $25-$30 per turnout. That includes the servos, pushbutton controls with LED indicators, and Frog Juicers to switch frog polarity. For another $19.95, you can add DCC control to the whole system.

    I know there are other servo-based systems, and I'm sure they are also good products. I just happened to get started with the Tam Valley stuff when it first came on the market, so I have not used other products.

    - Jeff
     
  18. MK

    MK TrainBoard Member

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    And those Tower Pro servos are cheap. About $3/each.
     
  19. Sumner

    Sumner TrainBoard Member

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    [​IMG]

    Besides the size as mentioned one other is the cost. Around $5.00 for the servo and a servo controller and the parts to.....

    [​IMG]

    .... make it all work from the edge of the layout.

    [​IMG]

    The most common way is with a SPDT limit switch that the servo arm hits when the turnout is thrown in one direction.

    [​IMG]

    The limit switch will then power the frog with the right polarity.

    More info here...

    http://1fatgmc.com/RailRoad/Trackwork/page-7.html

    Sumner
     
  20. jdetray

    jdetray TrainBoard Member

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    Very nice, Sumner. I have a couple of servo testers from when I was active in R/C flying. At one point I set up a test installation to switch a turnout, but it was nowhere as complete as yours!

    In the end, I decided I wanted a solution that included DCC, so I went with the Tam Valley products.

    - Jeff
     
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