Newbie help? - switches in conflict

Discussion in 'G / O / S Scale Model Trains' started by randow, Mar 2, 2005.

  1. randow

    randow New Member

    I'm pretty new to the three-rail "thing", after working with HO-gauge years ago. My problem is this...

    I've got a 4-switch MTH-brand layout, with 2 switches working fine. The other two, which join on the curved sides, seem to short out when activated, regardless of what I do. I've tried track power vs aux power, wired toggles and DCS. If I physically move the switches to other locations, they work, so I'm fairly sure it's something with the layout. I understand blocking and such on two-rail layouts, but I thought that three-rail was immune to that.

    I have attached a quick diagram with 4 switches indicated. Number 2 and number 4 are in conflict. Interestingly, if I disconnect the tract between them, the problem goes away and both switches work. Is there an approved way to insulate the two from each other, or is there a better way?

    Any help would be appreciated.

  2. randow

    randow New Member

    Sorry. It appears that the diagram didn't attach. The two faulty switches are connected by an s-curve and the "turn sides" are connected. This causes them each to use opposite rails as ground, I guess.
  3. randow

    randow New Member

    Update: here's the layout diagram

    Thanks for the help on the image, which should now be attached

    Attached Files:

  4. N Gauger

    N Gauger 1:20.3 Train Addict

    Ok - It's not a switch problem :( Follow the track from 2 through the turnout to "4" Then follow the path the engine would take to "1" then it would go around that left hand turn Back To "2"....

    This is a loop - You cant do that inside a layout without plastic rail joiners, The easiest way to fix it is to turn one of the switches around Either "1' or "2'

    Move switch 3 to either 1 or 2 and that should fix it.
    Just swap either pair (1 & 3 ) or (2 & 3) and that should do it.

    Otherwise you'll have to put plastic rail Insulators just above "1" and to the track to the Left of "2" and to the track right above "2".

    This will make that loop a separate power block.
  5. N Gauger

    N Gauger 1:20.3 Train Addict

    Here's the result First with 2 & 3 Swapped out - Notice the "loop" is now a "Square"

    Then Second, There are your Insulating Rail joiner Locations. Blue ones must be done -- green (to the right of 4) is optional.

    Insulators must be put on all 3 rails at each location. You will need to power these with separate power leads & you will need a DPDT switch to reverse the power to the loop.

    Attached Files:

  6. randow

    randow New Member

    Thanks! I suspected something like that, but thought that 3-rail wiring meant I didn't have to do the blocking that I used to do on 2-rail layouts. Looks like it's time to go buy a book on 3-rail wiring. Darn! That means a trip to the train store. <smirk>

    Thanks again!
  7. TR-Flyer

    TR-Flyer Member

    Hey guys:
    I don't think this is the problem. The thing about three rail track is both outer rails are tied to the "common" pole on the A/C transformer and the center rail is variable. When it loops back on itself teh same arrangement is still there. Both outers are "common" and the center rail is variable. That's the beauty of three rail track vs my "S" gauge two rail. I have to use the toggle solution on a loop.

  8. N Gauger

    N Gauger 1:20.3 Train Addict

    OOPS... Yeah - 3-rail is wired this way :( I'm so used to 2 rails - that I loked for thre loop :( Try it & see what happens - you never know.. But if it still shorts out - then TR-Flyer is right!!!
  9. Greg Elems

    Greg Elems Member

    He shouldn't have to use a toggle switch at all. It has been a while since I have used any power switches on my O27. When I did, I had to make sure the wiring was the same, with the three post controlers on my Lionel switches. I'm not familiar with MTH switches. How many posts do they have on the switch for control? If you unhook the controler on the #4 switch, does #2 work right?

  10. randow

    randow New Member

    Thanks for the response. I "un-reversed" the loop and that made the switches stop complaining. That fixed the problem, but I suppose it also changed the concept of the layout. During my debugging, I did find that insulating the joint in the s-curve also did the trick, so I may try an official insulated track. I'll do that next time I make it to the store. There's certainly something going on that doesn't quite hold up under the "double common" theory. As I continue to play with it, I'll add notes here for those who may be interested. As an FYI, I failed to mention earlier that I'm using MTH's RealTrax, not that it should make any difference in the theory involved.

    Thanks again!
  11. Greg Elems

    Greg Elems Member

    Looking at your layout picture, it would seem the conflict would be in #1 and #2 rather than #4. I remember on my Lionel switches one of the three wires was considered the hot or + and had to be on the #3 post with the #1 being next to the edge of the switch and #2 in the middle. The only reason I had the insulated section was to make it a non derailing switch which ment that it would snap to the route need for the train going to the single track. Not sure if that makes sense....

    Anyway, if the insulation joint works, does it work like the old Lionel switch? Doesn't MTH have infer red activated switches in Realtrax too?

  12. randow

    randow New Member

    The MTH RealTrax switch allows me to use either the wired toggle or their DCS system (remote control to "Acessory Interface Unit" to send signals to locomotive and switches). In both cases, the results were the same.

    Forgive my lack of proper terminology , but I'm told that the "inside rail on a switch" is electrically different from the rest of the track. By "inside", I mean this: On a right-hand switch, the right rail of the straight track and the left rail of the curve are "dead" or something like it. Picture the "V" that the switch makes. I'm told that the "inside of the V" isn't grounded like other track, and that when my #2 and #4 switches (in the original layout) bump into each other, they complained.

    I'm still coming back to the thought that when #2 and #4 were insulated from each other, then the current ran in the same look compatibly. Although they're both grounds, the outside tracks between the switches were grounding on opposite rails. I thoght that the A/C current made it a moot point, but the continued dialog suggests it's just not that simple.

    I certainly appreciate the debate and the ideas! What a great forum for a newbie!
  13. TR-Flyer

    TR-Flyer Member

  14. 60103

    60103 Pooh Bah

    I'm working from something that's half a century old, but the Lionel non-derailing feature required an insulating (fiber) pin in the rails past the frog. This bit of rail was isolated from the restof the layout and when metal wheels hit it, the switch changed to that direction. Do your instructions say anything about this? If you take the loop apart and the touch a common wire to the rail, does the switch change?
    I've seen pictures of new Lionel ones, and they now seem to have the activating rail already isolated.

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