reverse look, but no loop

Discussion in 'DCC & Electronics' started by daboonk, Feb 21, 2005.

  1. daboonk

    daboonk Member

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    reverse loop, but no loop

    i am looking to have a reverse loop on my layout but not using a loop, i have paralell tracks which are going in opposite directions and i am wondering if there is any way to do this, cross over from one to the other with out shorting out the track, thanks

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  2. 60103

    60103 Pooh Bah

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    If you have a curve joining the end of the two parallel tracks, you have a reverse loop. You will need to add enough separate blocks and wiring to cross a train over.
  3. railwaybob

    railwaybob Member

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    From the looks of your diagram, all you have is a crossover and not a reverse loop.

    Now, if you connect the top track to the bottom track at one end, you will have a reverse loop.

    And, if you connect the top track to the bottom track at both ends, you will have two reverse loops.
  4. Gary Pfeil

    Gary Pfeil Active Member

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    daboonk, to avoid shorts when using the crossovers, simply wire both tracks with the same polarity. Remember that with DCC the direction of travel is not affected by the track polarity. Now if those two tracks are connected by a turnback curve at each end, those turnback curves are reverse blocks, and will need reverse modules. This is preferable to having the blocks at the crossovers be reverse blocks, as the turnback curves are more likely to be a train length long.
  5. daboonk

    daboonk Member

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    if i block the turn backs will i need 2 reverse units?
  6. Gary Pfeil

    Gary Pfeil Active Member

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    Two would be best. But no, you don't need two. The restriction if using one to operate both loops is that you can only have one train at a time cross the gaps at either end of the reverse blocks. In other words, entering or leaving those blocks at the same time. You can have a train sitting at one end and run a train into the other, they just can't cross the gaps at the same time. Since the module works by flipping the polarity of the reverse block to match the polarity of the adjacent block. The reverse module, if only using one for both sections, will change teh polarity for both sections. If it sees conflicting requirements, you'll wind up with a short.

    So if you can live with only using one at a time, you can save some cash. You can always add a second one later.

    Gary
  7. daboonk

    daboonk Member

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    would this mean if i had 2 trains running at the same time on the straight section that they would be running in the same direction,
  8. Gary Pfeil

    Gary Pfeil Active Member

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    When using DCC, a trains direction is controlled by the throttle only (well actually the decoder) and is completely independant of track polarity. The only issue you have to deal with concerning polarity is that when a wheel bridges a gap between blocks that the polarity of the two blocks match, in order to prevent a short. Thus the use of the reverse module on any blocks which connect opposite rails together. It really is a different mind set than DC and takes a little getting used to.

    Gary
  9. railwaybob

    railwaybob Member

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    Hello daboonk. Before you get too concerned about reverse loops, is the diagram above going to be part of a reverse loop, or will it simply be a crossover? From the sound of the questions you are asking, you may be getting confused.

    If you only have a crossover, you only need to put a track feed into the middle of the crossover (what kind of turnouts are you using because you may not even have to do that).
  10. daboonk

    daboonk Member

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    yea, im thinking what will have is a cross over, makes sence,crossing from one polarity to another
    I am using atlas mark threes, thanks
  11. daboonk

    daboonk Member

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    so this cross over will need a polarity switcher, such as the one my mrc, since i am running dcc, is this correct? this is also two paralel tracs, switching from one to the other, one more thing, im not using an actualy cross over , but 2 turnouts
  12. railwaybob

    railwaybob Member

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    Hello daboonk. No, you will not, I repeat, you will not need a polarity switcher. Simply because you do not have a reversing loop. Your two Atlas Mark IIIs are DCC friendly and therefore do not need any insulating gaps. All you do is drop some track feeds in between the two turnouts.
  13. daboonk

    daboonk Member

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    ok, thanks for your help, but what are track feeds, and do you realise that connecting these to tracks will casue a short?
  14. railwaybob

    railwaybob Member

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    I've taken your diagram and redrawn it to show the two rails. The top rail of each track has been coloured red and the bottom rail has been coloured blue. At the top, I've added your track power buss - ie the two wires that will feed the rails. These are also coloured red and blue to correspond to the two colours of the rails.

    Wherever you see a round blob, either a red one or a blue one, that's where your track feeders are soldered either to the rail or to the track power buss.

    Notice that for the two tracks, Track A and Track B, that are to the left of the turnouts, you have two pairs of feeders. Also, for the two tracks, Track A and Track B, that are to the right of the turnouts, you have two pairs of feeders.

    And, in the part between the two turnouts, we have one pair of feeders. You will not get a short because you have an insulated frog on your turnouts.

    Now, what are track feeds, you ask? These are simply pairs of wires, one to the top rail and one to the bottom rail that will get the electricity to your tracks. You should install track feeds about every 3 feet or so to make sure there's lots of electricity getting to the tracks.

    And what is a track power buss, you ask? It's simply two wires, in this case, one blue wire and one red wire, which is run from the Rail A and Rail B connections of your command station (if you use a Digitrax command station).

    That's all you need to feed power to these rails. Simple, eh?

    I would suggest that you might want to visit my website to get a better understanding of how to wire your layout. From the index page, click on DCC.

    Bob M.

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  15. Gary Pfeil

    Gary Pfeil Active Member

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    dabonk, I suggest you post the rest of the track plan as what the two tracks do beyond the ends shown has an impact on a correct answewr.

    Gary
  16. jetrock

    jetrock Member

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    Another thing that daboonk has not made clear is whether or not he is using DCC--some folks have assumed he did, but it sounds like maybe he does not...
  17. Gary Pfeil

    Gary Pfeil Active Member

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    That's true jetrock, being that he posted in the DCC section and hasn't responded negatively to my posts stating "with DCC" I feel that he is trying to use DCC, but have wondered also.
  18. daboonk

    daboonk Member

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    thanks for all of your help, i am going to be using dcc when my mrc prodigy advace arrives, thanks railway bob for the help. i never knew about a bus line or track feeding every 3 feet, hopefully i can get this to work, i'll get the rest of my track plan on here if i can
  19. daboonk

    daboonk Member

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    ok, i geuss i didn't explain my situation very well, sorry for wasting you time railway bob, here is a better diagram, sort of, the two inner rails are the same polarity

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  20. jetrock

    jetrock Member

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    Your track plan is commonly known as a "dog bone", and the crossover in the middle, in effect, makes each end of the "dog bone" loop into its own reversing loop.

    A "crossover" is a term to describe a pair of switches arranged in the way you show in your diagram--trains can "cross over" to the other track.

    In terms of wiring--offhand, I'd say that insulators should go in between the diverging ends of the switches that make the crossover, as well as at either end of one of the two straightaway section--that becomes your "reversing loop" area. You'll need a separate polarity control.

    I'm not sure how DCC handles reversing loops--I am told that automatic controls are needed to avoid DCC chip frying shorts.