Two reversing sections - gaps here?

[Frisco-kid]

 

Just double-checking, are the gaps marked correct for these 2 reversing loops?

[jeffrey-wimberly]

I would make the distance between gapped sections at least two car lengths longer than my longest train.

[Texas Zepher]

Yup that would work.  If possible, I would move the right gap on the left loop, and the left gap of the right loop closer (as close as possible) to the main turnout causing the loop.  I assume there is more track as indicated by the "turnouts" off the main that might make this impossible.

[Frisco-kid]

Zeph & Jeff,

There are indeed some un-drawn sidings as indicated by the turnouts. I've clarified the drawing. I'll move the gaps up as close to the main loop turnout while keeping them below the lowest turnout for the sidings. That's the part that threw me a bit.

[MisterBeasley]

As drawn, you could put the insulators on both branches of the turnout closest to the upper left corner of the diagram, above the 3 parallel tracks.

On the right side, I would use 3 insulators, rather than 2.  The first would go on the rightmost side of the turnout closest to the upper right corner.  The second would go down the other path, but beyond the next two turnouts.  Remove the insulator closest to the lower right corner, and leave the remaining one where it is.

This arrangement would give you longer reverse loops, and reduce the chances of having a train span both breaks at the same time.

Klaatu barada nikto, Dude.

[Frisco-kid]

MisterB,

We have come to visit you in peace -- and with good will. 

To the topic at hand, I'm in N scale - all rolling stock wheels are plastic or nylon. By 'longest trains' I'm assuming the locomotive(s) are the only ones I really care about; their metal wheels will create the short circuit activating the reverser.

If that's the case, the reversing sections are already more than long enough to handle a 2- or 3-loco consist.

I do have a single Kato caboose with metal wheels; I'll take care with that one or swap out the wheelset.

[MisterBeasley]

On the other hand, since you're laying the track, why not make it as long as it can be?

Metal wheels do roll better, and, at least in HO, many of the better-quality cars already come with them.  That caboose will get you, sooner or later, and you might find yourself with some illuminated passenger cars some years down the line.  It' going to be easier to prepare for this now rather than re-do your trackwork later on.

My own reversing section is a diagonal crossover from one side of an oval to the other.  I made it as long as I could, based on the track plan, but I still end up with shorts now and then.  It's simply NOT long enough to accomodate the trains I'm running.  With this experience behind me, I like to warn others about the same traps.

After all, we come To Serve Man.

[Frisco-kid]

To Serve Man   ... it's a cookbook!!!

You're right that it's easy enough to make the reversing sections longer now rather than fight it later.

Not sure I understand your suggestion about 3 gaps on the right loop. Wouldn't it require multiple connections to the reverser?

About the caboose - if the polarity reversal has already occurred as the locos traversed a gap, what happens when any other metal-wheeled car subsequently passes over that same gap? Or is the problem when two gaps are bridged simultaneously?

[MisterBeasley]

First, imagine taking the insulator in the lower right corner and moving it up to just the other side of the turnout, on the straight branch.  Then, you would need another insulator on the curved branch.  Finally, move both of those insulators up just before the next turnout on each track.  There is still only one connection required to the reverser, but the turnout in the lower right moves inside the reversing section, so you need to have an insulator on each branch, rather than a single one at the point end of the turnout.

The auto-reverser will flip the polarity of the loop whenever it senses a polarity mis-match on either end of the loop.  In DCC with an auto-reverse unit, the loop is usually wired up to be the part that flips, and the main line stays the same.  (You could wire it so that the main line flips, but that's not usually the best way to do it, for a number of reasons.)  So, when the train first enters the loop, the polarity may or may not flip, depending on which way it was left the last time a train went through the loop.  Then, when the train gets to the other side, the loop's polarity will flip again, to line it up with the outgoing track.  In DCC, loco direction is controlled by the decoder, not by the polarity of the track.  (Exception:  If you are running a DC locomotive on your DCC layout as Engine Zero, this will not work.  The DC locomotive's direction is still controlled by the polarity of the track, even in DCC.)

So, that's the simple case.  You're right about that metal-wheel caboose.  If it is over the "entrance" insulator at the same time as the engine is over the "exit" insulator, then you've got a problem.  The auto-reverser will not be able to keep both sides happy, and you'll end up with a short circuit.

[Frisco-kid]

 

(Removed photo)

 

Well, I could make it as long as both entire loops this way, even longer if I moved the left-most gap all the way up ...  yes/no?  The reverser would power/monitor all tracks in each loop - can a single unit handle it?

[MisterBeasley]

No, that won't work.  On the right hand side, you actually have another loop inside the one you've isolated!  The lower insulator on the right side needs to be 2, or even 3, insulators.  Try taking that one out, and putting one on each of the three tracks right below it, beyond the two turnouts.  That will give you the longest possible loops.

Likewise, you can take the leftmost insulator (on the other loop to the far left) and put it above the 3-track yard, just before the track re-joins the main line.  This will put the 3 yard tracks within the reverse loop, too.

I use a Tony's Trains reverser, one generation back from the ones being sold now.  I believe the specs on it say it will support up to 2 amps, which should be plenty for anything in the a reverse loop.  I've got my whole yard in the reversing section, and I have no problems.

[Frisco-kid]

 

 

A hybrid of your first recommendation plus what we've been discussing - will this work?

Staging tracks will be the death of me yet ...

[MisterBeasley]

That's it.  With the loops that long, I don't think you'll have to worry about The Day The Trains Stood Still on your layout.