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Sidings inside reverse loops

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  • Member since
    February, 2018
  • 3 posts
Sidings inside reverse loops
Posted by Jeff-F on Monday, April 30, 2018 8:13 AM

I'm new to the forum and designing my first DCC based layout.  I have a question about reversing loops.  I would like to create a reversing loop that has a siding in it and the loop is controlled with a PSX-AR autoreverser.  If I park a locomotive on the siding and then enter the loop with a second locomotive that traverses the loop and then exits.  Then if I startup the first locomotive and come out of the siding and then exit the loop, will the PSX-AR handle this correctly?  

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  • From: Bedford, MA, USA
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Posted by MisterBeasley on Tuesday, May 01, 2018 11:47 AM

Yes, that should be just fine.  A PSX-AR has the capacity to handle multiple locomotives.  I have two reversing sections, and each has multiple sidings coming off of it.

This probably is irrelevant, but if you are in the process of converting from DC to DCC and you have a DCC system that allows you to run DC locomotives (Digitrax, Lenz and maybe a couple of others) then you will find that DC locomotives do not work with auto-reversers.

It takes an iron man to play with a toy iron horse. 

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  • From: Dearborn Station
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Posted by richhotrain on Tuesday, May 01, 2018 3:39 PM

Jeff-F

I'm new to the forum and designing my first DCC based layout.  I have a question about reversing loops.  I would like to create a reversing loop that has a siding in it and the loop is controlled with a PSX-AR autoreverser.  If I park a locomotive on the siding and then enter the loop with a second locomotive that traverses the loop and then exits.  Then if I startup the first locomotive and come out of the siding and then exit the loop, will the PSX-AR handle this correctly?   

Yes, the PSX-AR will handle it correctly. Since the siding is inside the reverse loop, the first locomotive to enter the loop will flip the polarity to match the section of track from which the locomotive is entering the loop. If the polarity already matches, then when the locomotive exits the loop, the polarity inside the loop will flip to match the polarity of the section of track that the locomotive is exiting to. Meanwhile, the polarity of the siding inside the loop always matches the polarity of the loop itself.

Rich

Alton Junction

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Posted by gregc on Tuesday, May 01, 2018 6:08 PM

what happens if both trains leave their respective siding tracks in opposite directions?

greg - Philadelphia & Reading / Reading

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Posted by ROBERT PETRICK on Tuesday, May 01, 2018 6:12 PM

gregc

what happens if both trains leave their respective siding tracks in opposite directions?

A short will occur if both locos cross both ends of the reversing section at the same time.

Robert 

LINK to SNSR Blog


  • Member since
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  • From: Bedford, MA, USA
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Posted by MisterBeasley on Tuesday, May 01, 2018 7:07 PM

ROBERT PETRICK
A short will occur if both locos cross both ends of the reversing section at the same time.

Make that "exactly" the same time.  In a true reversing "loop" where the loop starts and ends at the same turnout, you would of course have a collision.  If you've got a reversing "section" where the loop rejoins the main at two different points (think of a diagonal track across an oval) you MAY get away with it.  That's one of the advantages of a high-end, solid state reverser like the PSX.  It can switch polarity fast enough that both engines may make it out of the loop as the AR unit flips polarity in milliseconds to keep both sides happy.

I've got one of those diagonal-across-an-oval situations.  Sometimes, I run a lighted passenger train through it, and the train is longer then the reversing section, but the reverser unit can usually handle the string of polarity flips.

It takes an iron man to play with a toy iron horse. 

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Posted by Jeff-F on Tuesday, May 01, 2018 9:10 PM

Thanks everyone for your helpful replies.  I don't think I'm ever going to race two locomotives to opposite ends of the reversing loop to see if I can short out the circuit!!  I just want to make sure I can park a locomotive or two inside a loop and then bring them out without worrying about a short circuit.  Sounds like I can!

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  • From: Dearborn Station
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Posted by richhotrain on Wednesday, May 02, 2018 4:06 AM

MisterBeasley
 
ROBERT PETRICK
A short will occur if both locos cross both ends of the reversing section at the same time. 

Make that "exactly" the same time.  In a true reversing "loop" where the loop starts and ends at the same turnout, you would of course have a collision.  If you've got a reversing "section" where the loop rejoins the main at two different points (think of a diagonal track across an oval) you MAY get away with it.  

That's why I alway make a distinction between a "reverse loop" and a "reversing section". I have reversing sections on my layout that look nothing like a loop. In a true reverse loop, the train enters and exits a section of track at the same point. In a reversing section, the train enters and exits at two different points.

Rich

Alton Junction

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Posted by selector on Wednesday, May 02, 2018 12:17 PM

And really, it's any 'offending' metal tire on any item of rolling stock that could cause the short.  As soon as any one metal rim makes contact across the gap when the two rail ends are out of phase, the reverser must react immediately. It might be a locomotive, it might be a caboose...but the rail end-to-rail end gap that gets bridged by one metal tire will cause the short if the ends are incompatible electrically.  So, at least one DCC supplier recommends gaps that are staggered, and DCC Specialties recommends double staggered gaps if your reversing section is likely to be longer than any consist you have.  The second set of gaps are further into the section to be reversed by just over the distance of your longest cars' trucks axles' wheelbases.

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Posted by gregc on Wednesday, May 02, 2018 12:52 PM

 so it really doesn't matter from which end of siding/reversing-section either train enters or leaves from.

i was thinking of the purpose of a siding being for trains traveling in opposite directions to pass one another or a faster train passing a slower train.

is the siding being used for staging?

greg - Philadelphia & Reading / Reading

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