S curve question

Mike Connolly Feb 1, 2010

  1. Mike Connolly

    Mike Connolly TrainBoard Member

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    Hi All,

    I'm not new to the forum and I read a lot but I don't post very much. But I need advice and searching the forum hasn't given me much to work with on this issue. So it's time for a more direct approach.

    I had planned to use a PECO 55 double slip to replace a long crossing but I am thinking about a pair of RH turnouts connected point to point for the same functionality. I know this creates something of an S curve but apparently there's a reliability issue with double slips as well. I need to do one or the other so, given the choice, what would you do?

    Thanks,

    Mike
     
  2. MRLdave

    MRLdave TrainBoard Member

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    I'm not familiar with the Peco doubleslip, but doubleslips can be troublesome, especially on a mainline. I'd vote for the standard switches, and use the biggest # switches you can.....#8 is better than #6 is better than #4. The bigger the switch, the less "s-curve" effect you'll see.
     
  3. ppuinn

    ppuinn Staff Member

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    Mike:
    Is the RH crossover between 2 parallel tracks located close enough to a right hand curve that the crossover from the left track to the right could be accomplished by going through the curved portion of a right turnout into the straight portion of a left hand turnout? Your mainline would pass through the curved portion of the Left handed turnout, but, if you were using right side running, it would always be going through the turnout with trailing points rather than facing points.

    If the RH crossover is located in a place where the parallel tracks curve to the left, then the crossover from the left track to the right track would be accomplished by going through the straight portion of a left hand turnout into the curved portion of a right hand turnout.

    The upside: absolutely no S-curves. The downside: loss of the classic crossover between two parallel (and straight) tracks.
     
  4. Mike Connolly

    Mike Connolly TrainBoard Member

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    Thanks but I don't think that will work here. The geometry would be two straight track in parallel then heading south right to left then straight or right again to replace the crossing. The attachment shows it with the crossing.

    Mike
     

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  5. Mike Connolly

    Mike Connolly TrainBoard Member

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    MRLdave,

    Revised track plan substituting ( in purple) a RH #8 south and a RH#6 north on the yard/round-table side of layout in lieu of the double slip.

    Thanks for you help.

    Mike
     

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  6. jagged ben

    jagged ben TrainBoard Member

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    Which one is cheaper? ;)

    Seriously, I kinda think it's six of one, half a dozen of the other. But I would lean a bit toward the double slip, since if the double slip works correctly then you have no S-curve problem. Also it allows that siding to be a little longer.

    I don't have experience with peco double slips, however.

    If you do go with the back-to-back turnouts option, one option would be to re-plan your operations so you are usually going through just one diverging route. i.e. have left hand running standard to the 'north' of the turnouts.

    The only thing I would add is that I don't really see why you are replacing the crossing at all. Knowing your reason for doing that might make a difference to my advice.
     
  7. Mike Connolly

    Mike Connolly TrainBoard Member

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    I too like the double slip IF it works correctly but from what I've read in other posts, that's iffy and as you can see in that configuration, it is in a critical location as a train crosses it coming in and, if reversed, going out as well. But as you point out, I lose six to eight inches from both lines and since both were supposed to function as passing tracks for the other, I don't like giving back two car lengths. Particularly so since the track leading in from the turnout at the right top of the layout is on a 2% grade until it finishes the turn.

    What's cheaper isn't a real issue but since I have a spare RH 6, the two switch option is about $35 cheaper than the double slip.

    Why change from the crossing? The "normal" direction of travel is from the peninsula to the yard area using the lower approach. As presently configured, depending on how the right top turnout is set, one side gives me the option to approach the yard and turntable areas first then the option to reverse or continue the loop via the upper line. The other line forces the reversal, there is no other option. Now I know I can make that decision at the right top turnout but that turnout must flip the other way if the reverse loop is used so the chance it will be set "wrong" as the next train approaches it are fairly high with the crossing and me in control. The switches give me the ability to recover and more operational flexibility.

    Mike
     

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  8. jagged ben

    jagged ben TrainBoard Member

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    Ok, I think I followed that...

    What about not having the tracks cross each other, but having them stay parallel? This would reverse which track goes where entering at the 'top right' turnout. (But so what?) Then you could put a crossover between them with right hand turnouts. The crossover would allow you to do your 'recovery' trick if you ended up on the line that forced the reverse. Slightly less flexible operationally, but it solves the main problem you've explained, and perhaps you'd have more reliable trackwork.

    Just a thought. Maybe you don't have the space for that, I can't really tell.
     
  9. Mike Connolly

    Mike Connolly TrainBoard Member

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    Ben,

    As I explained my answer to your question "why change from the crossover" to my wife of 42 years, she pointed out to me that neither track was presently a passing track because both tracks were used by the reverse loop in and out anyway. So says she, you're not losing anything you have now, the double slip gives you a switch you'll worry about and the other solution gives you a shorter passing track than you want so get rid of the second track altogether and simplify the problem. And so I tried it her way and it does. Your question was the key to rethinking the issue and I really appreciate it. Thank you.

    Mike Connolly
     

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