Reversing Loop + Peco Turnout + ?????

Discussion in 'HO Scale Model Trains' started by riverotter, Dec 31, 2007.

  1. riverotter

    riverotter Midwest Alliance Rail Sys

    I'll bet this topic has been posted before, but the Search feature didn't bring up anything quite like what I'm trying to find out, so at the risk of repeating 'common knowledge', I'll start a new thread.

    Simply put, if I'm using a Peco Insulfrog power-routing turnout at the 'throat' of a reversing loop, what else do I need to do to deal with the "polarity problem"?

    My new layout's Phase 2 plan calls for two reversing loops and I've never done one before. I've read a bunch of the literature, but none of it addressed this situation.

    Info: HO scale, DC power, Atlas Code 83 Flextrack and Peco Insulfrog power-routing turnouts.

    Thanks for any and all advice!
  2. TrainNut

    TrainNut Ditat Deus

    In this thread...
    I was trying to hook up a reverse loop modulator with Peco Insulfrog power routing switches and I had all kinds of problems. After lots of frusturating troubleshooting, it turned out to be my controller.:curse::curse:
    In this post of that same thread... can see pictures of my loop and how it is set up. If I understand your question right, simply isolate the loop at both ends from the switch with either gaps or insul joiners, power the loop through the reverse loop modulator and you should be set. The only thing I wish I had done (and still might but not quite sure how to do it yet) is to hook up the switch to the reverse loop modulator so it automatically switches back and forth depending on where the locomotive is at in the loop. Mine is in N scale but that should not matter for what you are asking. Clear as mud?
  3. riverotter

    riverotter Midwest Alliance Rail Sys

    Thank you for such a quick reply! I've downloaded the information in that other thread for when / if I convert to DCC.

    For now, I'm still running a DC layout and I don't know whether there are any reverse loop modulators for "plain old" DC.

    If not, I'll need some other kind of solution.
  4. rogerw

    rogerw Active Member

    Some one correct me if im wrong put if he is using insulfrog with dc, as long as he has only one turnout going into the wye/reverse loop switched at a time just that switch would feed the loop. He would have to stop once in the loop and flip the switch/switches and reverse his throtle direction he could continue on?
  5. steamhead

    steamhead Active Member

    Hi...There is no "magic" to DCC...What you want to avoid is a short circuit, whether it's DC or DCC. You need to isolate both rails at the entry and exit points, regardless of the kind of turnout you are using. The method you use to reverse the polarity of the loop and the main line is strictly personal. I plan to use a reversing module when I get to that point, but have used DPDT switches in my other layouts to do the same thing.
  6. rogerw

    rogerw Active Member

    But with a insulfrog the rails are insulated
    "Insulfrog (Insulated Frog) turnouts incorporate the minimum dead section due to the tapered frog rail design. Each PECO Insulfrog turnout is 'switched' so that only the track for which the blades are set is electrically alive (except OO slips & G-45 turnouts...obscure stuff).
    edit: I cant find a diagram I was looking for but I thought if the switch is set for straight tru the siding is dead.
    Edit edit just the rail of the frog of a insulfrog switch goes dead. You still would need to isolate the outer rail sorry my bad.
  7. pgandw

    pgandw Active Member

    The use of the Insulfrog turnouts does not affect reverse loop wiring, period.

    In reversing in DC, the train must be in a completely isolated section of track while the direction controller for the main line is toggled, switching the polarity of the main line. Obviously, an Insulfrog or any other type of turnout at the throat of a reversing loop does not meet the requirements of a completely isolated section, no matter which way the turnout is thrown.

    In DCC, since polarity change does not cause direction reversal, the isolated section has its polarity reversed while the train is in the isolated section to prevent a short circuit on exiting the isolated section. This is typically done by an auto-reverser that senses the short circuit and switches the isolated section polarity before the system circuit breaker can trip on the short circuit.

    To create an auto-reverse system in DC is not trivial, especially if travel in both directions through the isolated reversing section is permitted. A DC auto-reverse must know when the train is fully inside the isolated reversing section, and then switch the polarity on the main line to match the exit direction of the train.

    Trains longer than the isolated section create short circuits in both DC and DCC every time a metal wheel bridges the tiny gaps where rails are of opposite polarity.

    hope this helps
  8. TrainNut

    TrainNut Ditat Deus

    Oops. Missed that critical piece of information. Still, others have now chimed in with some very good advice and information.
  9. 60103

    60103 Pooh Bah

    The flexible solution requires a long section in the reverse loop that is insulated in both rails at both ends -- usually right at the point that controls the loop. The main layout and the loop are wired to separate direction (DPDT) switches (which are not the direction switch on the power pack). If you have a second reverse loop, it can be wired to the same direction switch. If you have multiple cabs, each will need a pair of direction switches.
    If you go the other route and wire the reverse loop through a switch machine's contacts, you have to stop the train in the loop, change the turnout and change the main-line direction.
  10. msowsun

    msowsun Member

    You are right!

    I did the same thing years ago on a temporay layout I had. Just be sure to use a Peco INSULFROG turnout. One turnout, fed from the points end and then a loop connecting the two diverging tracks. Instant reverse loop with no additional wiring or insulators or gaps needed.

    When the train gets half way around the loop, stop the train, throw the turnout, reverse the direction of your power pack, power up and continue all the way around.

    If you want to get fancy, you can try to throw the turnout and the reverse switch at the same time without stopping.

    Try it. It works!
  11. 60103

    60103 Pooh Bah

    I don't understand the insulfrog bit about no gaps or insulators. If you trace the outer rail around the loop it runs from the south rail around and becomes the north rail. No gaps means a dead short immediately. A single gap means the train runs until it crosses the gap and shorts out. The outer rail requires 2 gaps and a switch of some sort on it. The inner rail can be continuous and switched by the points if you like, and that will even work with an electrofrog turnout.
  12. doctorwayne

    doctorwayne Active Member

    Too much information! :eek::p:-D The easiest way to do a reverse loop in DC is to, first off, have a DPDT switch separate from the power pack to control direction on the layout. It can be on a control panel for a tabletop layout, or on a walk-around throttle for a larger layout. Set the direction control on the power pack one way or the other, and never touch it again. Run a pair of wires from the power pack, through this switch to the track. Run another pair of wires from the power pack to another DPDT, then run wires from there to the rails of the reversing loop. Regardless of what type of turnout is used, cut gaps in both rails at both ends of the loop (i.e. - near the turnout). I like to set-up the switches so that they throw in the direction of travel, which makes it easier to keep track of which switch to throw which way. Once you've sorted this out, with both direction control switches set for the proper direction, run your train into the reverse loop. As soon as all of the loco(s) are past the gaps in the rails, flip the main direction control switch on your control panel or handheld throttle, and when the last car of the train has passed the turnout and entered the reverse loop, throw the turnout to allow the now-approaching train to exit the loop. No need for split-second timing or stopping the train. ;):-D

  13. msowsun

    msowsun Member

    You are right. There must have been a gap on the outer rail. I did this many years ago and had forgotten that little detail. I would drive the train to the gap and then throw the turnout. I remember being able to keep the train running continually if I threw the turnout and reversed the power pack at the same instant as it approached the gap.
  14. doctorwayne

    doctorwayne Active Member

    Kinda tough to do with a doubleheader, though, eh? :p;):-D:-D


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