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wye wiring

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  • Member since
    March, 2008
  • 5 posts
wye wiring
Posted by blueridgehobo on Sunday, March 30, 2008 4:09 PM

I'm about to lay track and Digitrax DCC power for the first time.  I intend to include one wye.  The wiring diagrams show insulated track connectors on both branches of the wye.  I don't see why the wye needs the circut break on both branches.  If the locomotive comes in on one branch and out the other it should need only one polarity change, not two.  If it backs out the way it came in, no polarity change is needed unless it crossed the gap on the way in, in which case it will cross it again on the way out and revert to its original polarity.  Am I confused?

Thank you, all who responded.  This has been a good education for me on wyes. 

  • Member since
    October, 2004
  • From: Colorful Colorado
  • 8,639 posts
Posted by Texas Zepher on Sunday, March 30, 2008 5:48 PM

 blueridgehobo wrote:
I'm about to lay track and Digitrax DCC power for the first time.  I intend to include one wye.  The wiring diagrams show insulated track connectors on both branches of the wye.  I don't see why the wye needs the circut break on both branches.  If the locomotive comes in on one branch and out the other it should need only one polarity change, not two.  If it backs out the way it came in, no polarity change is needed unless it crossed the gap on the way in, in which case it will cross it again on the way out and revert to its original polarity.  Am I confused?
Yes you are. If I understand what you are saying, you have the concept right but you are mis-interpreting the diagram. 

A wye has three branches.  Assuming the wye is free standing, only one of the branches must be insulated.  This requires 4 rails be insulated, which, to you, must look like two branches being insulated.

  • Member since
    September, 2007
  • From: Charlotte, NC
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Posted by Phoebe Vet on Sunday, March 30, 2008 7:10 PM
The section of track that is to be reversed must be completely isolated from the section of track from which the train is approaching.  It must therefore be isolated at both ends.

Dave

Lackawanna Route of the Phoebe Snow

  • Member since
    February, 2005
  • From: Southwest US
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Posted by tomikawaTT on Sunday, March 30, 2008 9:17 PM

 Phoebe Vet wrote:
The section of track that is to be reversed must be completely isolated from the section of track from which the train is approaching.  It must therefore be isolated at both ends.

True - but if the wye has a single stub leg (the most usual configuration) the isolation is only required at the two legs of the turnout from that stub.

If, however, the wye is a junction where a branch meets a main line (the railroad equivalent of a T intersection) then the 'reversing' leg must also be isolated a full train length back from the turnout.  Otherwise the entire branch would automatically reverse every time a train entered the wye.

Either way, there is only one completely isolated reversing section, which needs only one auto-reverse module.

Chuck (modeling Central Japan in September, 1964)

  • Member since
    September, 2007
  • From: Charlotte, NC
  • 6,095 posts
Posted by Phoebe Vet on Monday, March 31, 2008 6:43 AM

tomikawaTT:

I don't understand with what you are taking issue.

If the common leg of the wye is a dead end, it is already isolated at that end.  Isolating the two input legs completes the isolation of the reversing track.

As I stated, the section to be reversed must be completely isolated from the approach track.  If it is not, a short will occur when the section power is reversed.

 

Dave

Lackawanna Route of the Phoebe Snow

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