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Manual Reversing Loop Question

Fred runs N scale and posted this question:

“I know that Kato makes a polarity reversing switch. I understand isolating the loop from the main, and stopping the train within the loop before changing the polarity. I just cannot grasp the actual mechanics and timing of throwing the switch. Also, how do I set the transformer to move the the train out of the loop and operate it on the main?”

14 Responses to Manual Reversing Loop Question

  • You apparently are talking DC. When I built my home layout the reversing loop was a block of itself (isolated by insulating rail joiners at each end) and the track feeding it (the main line) was another block. The toggle switches are set in the same direction (Polarity) as the train enters the reversing loop. While the train is in the reversing loop, throw the switch of what will now be will be the exit track of the reversing loop changing the direction (this changes the polarity of the main line) allowing the train to continue in the opposite direction on the main. The same applies to the reversing loop at the other end of your main line. I used double throw, double pole, center off toggle switches. The wiring is explained in most HO wiring books. I built my layout and several others circa 1970 to 1980 (old school). It is DC and is still operable. I used Atlas controls on the other layouts I built. I run DCC at the club I belong to.

    • Fredsays:

      Ralph thanks for the info! Although I was able to understand the physical wire diagrams, I just couldn’t put together when to throw the switches, and in what order! I’m just not as clear as I once was. Thanks!

  • Randall Styxsays:

    This comment applies to DC.
    First, the loop will be fed by a turnout. Call the diverging ends S and C (straight and curved). The A end of the reversing loop connects to S and the B end connects to C.
    There are two ways. If you’re using only one dpdt switch (double pole double throw electrical switch). Wire the switch so that in one position the polarity of the A end of the loop corresponds with the S leg of the turnout, and in the other position the polarity at B corresponds to the C leg. If you set the polarity so that A matches S, you can drive your train onto the loop via S. Stop on the loop, change the polarity of the dpdt switch and reverse the direction of the train on the power pack. On startup, the train will then continue forward, even though the power pack says “reverse”.
    The other way is to use two dpdt switches, one for the loop and the other for the main line. Power both switches directly from the power pack. Enter the loop from whichever leg of the turnout matches its end of the loop. While the train is on the loop (you don’t have to stop it) throw the dpdt switch for the main line (and make sure to change the turnout). When the train exits the loop, it will continue. The “forward/reverse” of the power pack does not need to be changed in this case.
    A dpdt switch with a center-off position can turn the loop into a block where you can park a train while activity elsewhere continues.
    Some who read this might not know how to wire a dpdt switch for this purpose. The switch will have 6 wire connections – two on one side, two on the other, and two in the middle (like the 6 dots on a die). Connect the positive lead to one of the two contacts on one side and to the contact on the far opposite corner. Connect the negative lead to the other contact on a side and to the contact on the far opposite corner. That leaves the two middle contacts to connect to the track.

    • David Stokessays:

      Randall, the isolating block can be anywhere – it does not need to be near a “turnout”, the only proviso is that the section is longer than your longest train. There is no need to stop and start your train, nor fiddle with the controller knob – all you need to do is ensure the double throw, double pole switch wired into your reversing section is set correctly and the train should keep rolling just fine. Fred, please Google “model Train reversing loops” and you will get the information you need

      • Fredsays:

        David, I do understand that the entire train must be in the isolated section, but thanks for the reminder! I am going to look through the “googled posts” to continue getting the best understanding. Thank you.

    • Fredsays:

      Randall, thanks a lot, I think I’ve finally “got it”.I am only going to have a small layout, and introducing the start/stop activity should also help me in maintaining my concentration. I have envisioned putting a station in the loop.

  • Roland Psays:

    The easiest way is using an automatic reverser like Digitrax AR-1.
    Isolate a stretch longer than your longest consist, and feed power from the AR-1.
    The AR-1 is powered from your controler.
    When your train is entering the isolated track, the AR-1 will match polarity on its own.
    When your train is leaving this section, the AR-1 will match polarity to the track you want to enter.

    There are other products available, too.

    Advantage:

    – no DPDT switch
    – no train stop
    – two wires to the AR-1, two wires to the isolated section of track.

    • Fredsays:

      Roland, I have been interested in the AR-1 but it seems that while some say it works fine with DC others say it is for DCC only. I sure would like to learn if it does work with DC, as I don’t believe I’ll ever be using DCC. & I know it would definitely better if the grandsons are operating the train on their own!

      Thanks!

      • Roland Psays:

        Sorry, my mistake. You’re correct, those automatic reversers are DCC.
        But one might reconsider using DCC. There should be systems on ebay for low (lesser) money.
        I’m using ROCO multimouse and DIGITRAX PR3 as standalone for programming decoders, incl. Digitrax sounddecoders, on my N-scale layout. The PR3 is still cheaper than updating the ROCOmotion software for programming and allows to re-program soundfiles.

  • Dale Arendssays:

    Fred, the idea of a reverse loop puzzled me too at first. The concept leads one to think the track being reversed in polarity is the loop. It isn’t. The track that needs polarity reversal is the entry/exit from the loop. So, as long as the train is entirely between the two isolation points the reversing of the main can be done. Unless your train barely fits within those isolator there is no need to stop the train when you throw the switch.

    • Sheldon Clarksays:

      Doesn’t this mean you have to reverse the polarity of the loop when you send the train back from the terminus part of the layout?

  • David Broadsays:

    You are all looking at the problem from the wrong end. Isolate the loop at the point / switch both rails, Feed the loop from the controller and use the DPDT to change the polarity of the main line, or have a DPDT relay or switch operated by the point / switch motor. That way there is no need for fancy wiring and the controller does not have to be reversed or the train stopped.

  • Shaun Pollardsays:

    My loop has an independent supply – so as soon as the loco has passed thru the points you can change main polarity and then the points as the end of train goes by.
    I also have two tracks running to my loop and back to back points so you can select a different route in and out.By also fitting a bypass track I can have trains coming in on one main – go around the loop and return on the other main.
    it looks sort of like a “R” with a connection from the right leg to the loop

    • Fred Wagnersays:

      I sure would like to see a picture of that!

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