Reverse Loop Basics/Spacing

Michael Doleman Jan 18, 2018

  1. Michael Doleman

    Michael Doleman TrainBoard Member

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    I've got just about all my parts gathered together for my first Z-scale layout, which is (purposely) very simple. I have an inner & outer loop, which join at a double-crossover, and then there is a small siding which exits from the inner loop. I handn't planned on it at first, but now am thinking that I'd rather like to isolate the inner loop & siding from the main, outer loop. I'm using all Rokuhan sectional track & controller components.

    I have to admit: I am not 100% on how to implement the Rokuhan Reverse loop controller. I think I get it, but I want to check-in on a couple things, not the least of which: can someone just -- generally -- clarify the concept for me?

    As I understand it now, you electrically isolate a section of track by adding insulating connectors to attach that section to the rest of the layout. From there you can wire the reverse loop controller (C003) in one of two ways: 1) by simply routing power through it, to the isolated section of track, and that section can either be on or off, based on position of the controller switch. Or 2) You can wire the RL controller such that power activation will be relative to the switch position of a particular turnout controller. Is that roughly correct?

    Specific stupid question #1: if I'm running a locomotive from the main loop, over to the inner loop, and the inner loop is set so as to be non-powered whilst the crossover switch is set for that transfer, then how does the locomotive "make it" over to the inner loop?

    Specific stupid question #2: the Rokuhan insulated joiners look wide enough (2-3mm) that they could introduce alignment problems for a loop, if not somehow adjusted-for with equally-wide "non-insulating" connectors. How is this accounted for?

    Thanks...
     
  2. markm

    markm TrainBoard Supporter

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    Michael,

    This is the same layout you posted earlier? It's unclear to me why you would need the reverse loop electronics ( http://www.rokuhan.com/english/products/C003 Reverse loop controller, instruction manual.pdf ). The double crossover can be power routing (default, as shipped). The two loops would operate independently of each other in the normal mode. In the divergent mode, the two loops would share power. In this mode, one of the throttles would have to be turned off and the direction switch set in the neutral position.

    As for the rail insulators, there is enough give in the rails and compression in the insulator that I haven't had a problem. Do check when the tracking laying is done that they don't bulge slightly above the rails.

    Hope this helps,

    Mark
     
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  3. Michael Doleman

    Michael Doleman TrainBoard Member

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    Hmm., okay, yes, it makes sense, but I had hoped to not use two separate controllers for the simple layout I am going to implement (which, incidentally, yes, is still very similar to the one I posted earlier, in principle).

    My only goal is to be able to have more than one locomotive on the track, but not necessarily run them all, simultaneously. E.g., I might want to leave a loco on the inner loop/siding, while running a train on the outer loop. That's pretty much it. I'd planned to use a Y-splitter to use my C003 controller to power the two segments of track, but then use the Reverse Loop controller to route power, putting the double cross-over into non-power-routing mode.

    I guess I am slightly confused, which means that perhaps I better just go with the set-up as recommended by Rokuhan. I guess what I could do is power the outer loop with a RC02, and the inner (which has two turnouts) with my RC03. But, then again, that means I'd have to add a separate turnout controller onto the RC02, so why not just get another RC03...

    Thanks for the input, though, as this is helping me think it through a little more. I already know to a certainty that I am -- of course -- eventually going to want a couple controllers, so I suppose I may as well get another one now -- I.e., I can't formulate a strong argument against it (other than the cost being slightly higher than my original plan). And now, of course, what I'm thinking I'd like to do is power-isolate the siding from the inner oval :-/ So tell me, is THAT object best accomplished with a reverse-loop? Assuming I don't care about running traffic on the inner loop whilst operating the siding?
     
  4. Greg Elmassian

    Greg Elmassian TrainBoard Member

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    It does not sound like you have a reverse loop. Perhaps you might google "reverse loop" and see why special controls are needed. In DC, in a real reverse loop, you have to reverse the mainline to "come back out"... you see the loop in that manual.

    The insulators are necessary because without them you create a short circuit, connecting the two rails together (follow the outer rail in the loop, one direction it connects to the "north" mainline rail, and the other direction it connects to the "south" rail, thus a short.

    Greg
     
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  5. markm

    markm TrainBoard Supporter

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    The function of the C003 is to switch the polarity of the power not the power itself. If you look at figure #3 in the instructions you'll see the negative side (heavy dark rail) is on the bottom and after switching the controller it appears on the top. They are using the power routing capacity of the turnout to control the power flow. The only value of the C003 on your layout is that it would allow you to run one loop clockwise and the other CCW.

    Maybe you could post your latest layout. Looking at the original post, I'd suggest using a power feed on the outside loop, a second feed above the turnout on the inner loop and insulating joiners on the upper upper of the inner loop. This way you can us a "Y" and a single throttle to power both loops, you can park a train on the right side of the inner loop by using power routing on it's turnout and placing that turnout divergent. This has the added advantage of allowing you to run a train from the yard out to the main line. At a later time you could add a second controller, replacing the "Y".

    Mark
     
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  6. Michael Doleman

    Michael Doleman TrainBoard Member

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    Thanks for all the info, here. It's actually served to clear-up what was remaining of my confusion over what, exactly, each of the controls was for. Based on the replies, I'm going to go with keeping the double-crossover in power-routing mode, and simply have two controllers. I'll get an RC02, for which I already have a separate, single turnout controller, and then use my RC03 to run the inner loop & siding (which has two turnouts).
     
  7. Greg Elmassian

    Greg Elmassian TrainBoard Member

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    Their reverse loop controller is basically making it somewhat simpler to reverse the polarity of the main line and the reversing loop at the same time to facilitate the train now running in the opposite direction on the main line.

    (clearly other locomotives on the main line would all reverse direction too!)

    Greg
     
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  8. Michael Doleman

    Michael Doleman TrainBoard Member

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    Yes, thanks. Now that I am (I think) seeing it more clearly, and understanding how it works, the difficulty that I'm facing now is puzzling-out why anyone would select the reverse-loop controller over simply adding-on a completely separate controller. I mean, the reverse loop controller costs about $15 to $20, while an RC02 compact power controller is all of $30 to $35 or so. It just seems to me, now, that if you are going to power-isolate a section of your layout, unless there is a compelling functional reason NOT to, why not just power it on its own controller, so that it's always clear what's happening, and you have complete operational control over everything? I feel like I'm still missing something, maybe. I mean, is the wiring not actually a bit simpler with separate controllers? Seems so...
     
  9. Garth-H

    Garth-H TrainBoard Supporter

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    1. A reverse loop is when you have a turnout and the main loops back to the diverging route so you end up with a short as left rail and right rail are connected to each other. The Rokuhan controller is a manual control and it is designed to control an isolated section of track inside the loop where you stop set the exit turnout for the exit change the direction on the main and then change the polarity in isolated section and restart your train moving forward to exit the loop. 2. if you have two independent loops you need two controllers with a power routing cross over . 3. if you convert your double cross over to non power routing, then a single feed point will allow you to cross over and back between the loop, and when set for cross over you need to match polarity of inner and outer loop while going through the cross over. 4. with two loops and double cross over set in default power routing mode and power feed in main loop when cross over is set to cross over power from outer loop is fed to inner loop and you can run around inner loop and back out onto main with double cross over still set for cross over. Once you have the locomotive on the inner loop id you switch double cross over to straight through then there is no power in inner loop and all is stopped, but outer or main loop remains powered. 5. The main feature of Z from Marklin day is all turnouts are non power routing or power everywhere and with one power pack you can run one engine anywhere on the layout with DC. However if you convert to DCC, you can run no DC engines but you can run more than one decoder equipped locomotive anywhere on the layout. Going with power routing turnouts you are going old school with blocks and you need to rout power to each block and crossing block boundaries you need to the polarity correct or you short out at the junction with a locomotive straddling the boundary.
     
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  10. markm

    markm TrainBoard Supporter

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    Michael,

    The reversing loop is designed for one very specific function, to turn a train around. But even then, it's not required. If it helps, consider the Rokuhan drawing of the loop and ignore all the reversing switch wiring. You could run the train around the loop and out using just the turnout by doing:

    1. run the train through the turnout with throttle set forward.
    2. set the throttle to neutral. throw the turnout.
    3. set the throttle to reverse and drive the train out.

    Unless you are doing some like this with the double slip or crossover:

    slip-8 sized.jpg
    really shouldn't need a reversing switch.

    Isolation and power routing are two valuable options in a DC layout and shouldn't be ignored. They allow you park a train and for multiple controllers and trains to operate over common track.

    Consider some of the options available to you running on your posted layout with just the modifications I mentioned:

    Set crossover and inner turnout to divergent. Use outer throttle to pull the train out of the yard through the inner to the outer loop. Set the inner turnout to main and inner throttle set off and neutral. Run the train through both the inner and outer loop. Set the crossover to normal and run the train
    on either the inner or outer loop with the associated throttle. A lot operational possibility, You get the idea?

    Hope this helps,

    Mark
     
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  11. Michael Doleman

    Michael Doleman TrainBoard Member

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    Thanks for all the help! I love this forum. It's interesting how the books I have don't seem to really answer the one or two head-scratching questions I actually need answered, in order for the last remaining pieces of the puzzle to snap into place. I tend to understand things in such a way that I sometime overthink it, and don't realize that the answer I'm looking for is actually pretty simple. Once I see an example or two, I've got it, and I'm off and running. This forum has been very valuable for that, and I truly appreciate it. I'm glad for having asked a few (dumb) questions, so that I get my first layout more or less correct on the first try, rather than having to waste a lot of time & money.
     

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