Weight/Gravity Operated 3D Printed Switch Machine....

Sumner Dec 5, 2020

  1. Sumner

    Sumner TrainBoard Member

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    This is a manually operated switch machine that sits under the turnout very similar to the 3D printed one that uses a servo ( HERE ). I've thought about it for some time and finally got around to designing it and trying it out over the last couple days. It uses weight and gravity primarily to move and hold the turnout's points from side to side. There is no need for rods and such going from it to the side of the layout to operate it. One only needs to run a string from the machine to the side of the layout. Simple eye hooks will probably suffice and the route doesn't need to be in a straight line from the side of the layout to the switch machine.

    Now that I feel good about the concept working I'll work on a single pulley wheel that will to above the weight on one side and a knob assembly that will go at the end of the control string on the side of the layout.

    [​IMG]

    Above are the two main 3D printed parts, the body and the control arm.

    [​IMG]

    Equal weights are hung from both sides with a simple string. The one on the right will always pull the control rod down on that side sine the lever arm out to it is twice as long as the one to the weight on the left side.

    [​IMG]

    If the weight is lifted on the right side by the string going to the side of the layout the weight on the left side rotates the control arm down on that side throwing the turnout's points to the other side of the turnout.

    [​IMG]

    I installed the switch machine on the same test setup I use for the servo operated machine I made earlier this year ( HERE ).

    [​IMG]

    With both weights hanging freely the machine throws the points to the right as shown above.

    [​IMG]

    I tried some different weights and came to the conclusion the hand-laid turnout I was using 3 oz. on each side seemed to do a good job of holding the points in place very similar to how I setup a servo controlled turnout. One could try different weights for their situation. I found a good source for 3 oz. and other size weights on the internet where if I bought 8 lbs. worth the cost per turnout would be about $1.50. Not a bad price for turnout control as if you have a printer or access to one these switch machines would come in at under $2.00 each.

    [​IMG]

    [​IMG]

    To throw the points one needs to only lift the weight on the right side. Here I'm doing it by hand but it could be done with a simple string to the side of the layout. Pretty low-tech.

    [​IMG]

    I've posted a short video on YouTube ( HERE ). I'll soon try and get a single wheel pulley bracket and pulley wheel that will mount under the layout above the weight on the right side. The control line would go from the weight up and over the wheel and then to the side of the layout, hopefully, through simple eye hooks where it could be secured when the weight is pulled up to throw the points. Release it and the points are thrown back in the other direction.

    You can find the files to print this on my thingiverse.com account ( Soon ).

    You can find all the files to 3D print this object and others on my thingiverse.com account ( HERE ).

    You can also find the above and what will be added soon on my web site here .....

    http://1fatgmc.com/RailRoad/Trackwork/page-26.html

    Sumner

     
    Last edited: Dec 5, 2020
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  2. Sumner

    Sumner TrainBoard Member

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    Was happy that the prototype worked well so wanted to share that now. Still coming though is the following.

    1. The test string will be replaced with fishing line.
    2. A mount for SPDT switch for changing the polarity of the frog will be added.
    3. Facia controls will be coming. I have ideas for a couple different options.
    4. 3D printed items to help when running the line in extreme, tight or 90 degree situations.

    NOTE: One will have to play with the weights to see what works best for the type turnouts they are using. This should also work with HO turnouts but hopefully someone will give me feedback on that and I could make changes if needed,

    Sumner
     
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  3. HemiAdda2d

    HemiAdda2d Staff Member

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    This is slick. I like how simple it is. Are you required to hold the string the whole duration of a train movement? I'm not caffeinated yet, I might have missed it.
     
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  4. Sumner

    Sumner TrainBoard Member

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    Not if you're Mark Twain,

    Sumner

    P.S. String holders will be coming.....
     
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  5. Sumner

    Sumner TrainBoard Member

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    [​IMG]

    Above a mounting location for a SPDT switch has been added to the bottom of the switch machine. Using it allows you to change the polarity of the frog as the points move. I've found these limit switches from a number of places and as low as $.50 each are less. Look for ones with the 9.5mm/.374” center to center distance between the screw holes.

    Sumner
     
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  6. CNE1899

    CNE1899 TrainBoard Member

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    Sumner,

    Looks good! It passes the KISS test. Do you think this will work for Z scale?

    Scott
     
  7. Sumner

    Sumner TrainBoard Member

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    Don't see why not, probably HO also if the throw is enough. Give me input if it doesn't work for either and I might be able to modify it. Also just finishing up one of the side-of-layout control options. Pics soon on that,

    Sumner
     
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  8. Mr. Trainiac

    Mr. Trainiac TrainBoard Member

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    This would be a good device to control spring switches. If you used a light weight on only one side, the switch would stay in one position, while still being able to be pushed aside by the wheel flanges when a train enters from the other leg.
     
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  9. Doug Gosha

    Doug Gosha TrainBoard Member

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    My brother and I used a similar system, based on an article in MR, at the time in the sixties. It wasn't as sophisticated, however and we used fishing weights. The weights were both connected to the throw rod and hung from holes in the layout table. A line run out to the layout edge was pulled to lift the 2X weight to allow the 1X weight to throw the points one way and released to throw the points the other way. It worked well.

    Doug
     
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  10. HemiAdda2d

    HemiAdda2d Staff Member

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    How thick can the roadbed/base be? I have a HCD, plus 4" of foam, plus cork roadbed under my track. I have considered your product, but will it work with about 6" of throw distance? My switches are Atlas c55, #5 or 7s.
     
  11. Sumner

    Sumner TrainBoard Member

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    I doubt that 6 inches or even 4 is going to work. I've got it on 1 1/2" total and that is fine and I think 2 to 2 1/2 might be doable.

    The problem is that the further the throwbar gets above the pivot point on the switch machine the less the throw is on the switch machine under the pivot point. Since it isn't traveling as far you are going to probably need quite a bit more weight hanging off of it.

    You have to have a force against the points to not only throw them but to hold them in place. The further the distance from the points to the switch machine the greater that force has to be since the points are at the end of a longer lever arm. This also happens when using a servo under the turnout as it moves less the further the turnout is above it. I'd be interested in knowing how far above a servo controlled switch machine people are getting away with?

    If I end up with thick layers of foam I plan on cutting some of it out so that the switch machine is on a thin piece of plywood under just one layer of it. That way I'd still be able to get to it from below.

    Sumner
     
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  12. HemiAdda2d

    HemiAdda2d Staff Member

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    I figured throw rod flexibility might also be a factor. I might need to dig a trench under the ROW and use a coffee straw as a throw rod tube, and run it from topside.
     
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  13. Sumner

    Sumner TrainBoard Member

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    The music wire does come in different diameters. The .037 wire is pretty stiff but you do have a point and that is another factor.

    Have you seen what I call "Hidden Switcher"?

    [​IMG]

    You print out the enclosure shown above and sink it in the foam. Then ....

    [​IMG]

    ... you insert the SPDT slide switch into it. The switch can change the polarity of the frog and also moves the points back and forth and holds them in place.

    Nothing really new except....

    [​IMG]
    http://1fatgmc.com/RailRoad/3D-Printer/page-4.html

    [​IMG]
    http://1fatgmc.com/RailRoad/3D-Printer/page-7.html

    ... I've designed a number of items that can go on the top of the switch to camouflaged it. You push them back and forth to throw the turnout. Put the control wire to the throwbar in the top of the foam or 'your straw'.

    More about it all here....

    http://1fatgmc.com/RailRoad/3D-Printer/3D-Printer-Index.html

    Sumner
     
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  14. HemiAdda2d

    HemiAdda2d Staff Member

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    I have seen your hidden switch covers; I hadn't considered how I would actuate those switches, although your idea is attractive. I might make a mechanical switch machine looking cover, as a fuel truck and drums might be a little out of place in a place where roads don't go! :p
     
  15. Sumner

    Sumner TrainBoard Member

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    I can understand that. The switch machine would look good. I've considered doing one of those but haven't. I also saw another person do a stack of ties. That might work well also. Be sure and let us see what you come up with,

    Sumner
     
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  16. HemiAdda2d

    HemiAdda2d Staff Member

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    I joined the 2020-2021 Layout Party, and it's one of my bonus goals. If there's time after I finish my main goals, I'll dig into this project too. I encourage you to join the party if you haven't already!
     
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  17. Sumner

    Sumner TrainBoard Member

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    [​IMG]

    Made up a stack of ties today that could hide the switch machine and maybe a small work shack wouldn't be out of the question in a remote area.

    I'll try and get myself organized to joint the layout party. Probably need it so I stay more in focus :(

    Sumner
     
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  18. Sumner

    Sumner TrainBoard Member

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    I got all the components together for a test run of the 'gravity switcher'...



    ... It worked well. I'm tweaking a couple of them now. Changing the vertical pulley a little so it hangs at the same level at the horizontal one. Also forgot to account for the thickness of the fascia for the pull control. Now it will work on a fascia up to 5/8". Also making a piece to capture the two lines below the weights that will replace the nut there. Also nut on pull knob will be changed from the test setup to something that looks better.

    [​IMG]

    I've also made a lever option that can be used alone or ganged as shown above. Need to do a test run with it also. I'll get the files up when I'm done with all the testing,

    Sumner
     
    Last edited: Dec 20, 2020
  19. CNE1899

    CNE1899 TrainBoard Member

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    Sumner,
    I checked out your site. Very cool! That lift sure is a sturdy workbench!
    I am lookin forward to be able to print the manual switch and levers!
    Thanks for posting,
    Scott
     
  20. CNE1899

    CNE1899 TrainBoard Member

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    Sumner,
    Another question I have, is how much height do I need underneath the layout to allow for the mechanism?
    Thanks,
    Scott
     

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