Reverse Loop Variations

We've been talking about reverse loops in two threads, one in DCC and Electronics and another in N Scale. I've tried to explain what I see are the advantages and disadvantages of different types of reverse loops, and was asked for diagrams. Here they are.

In all diagrams we assume that the main line is on the right side of the diagram.

Here is a simple reverse loop:



The red area is connected to the reverse unit, in my case a Digitrax AR-1. I have built this loop and don't like it. A northbound train enters the loop through the two switches. Once the train is completely inside the loop you must remember to toggle the loop switch or you'll derail. Once back on the main you need to close that switch so you don't derail southbound traffic. Once you've reversed your train, unless there is another reverse loop on the layout, it will be southbound when it comes around on the main again. To reverse it to northbound you must back your train through the reverse loop. Of course, the length of the train cannot exceed the size of your loop.

When I get my new 5'x9' table up I'm going to build the double crossover reverse loop:



Again, the red area is powered through the reversing unit. The double crossover allows you to enter and exit the loop from either direction on the main. Also, you don't have to worry about derailing when you exit the loop; if you forget to toggle your double crossover you will just return to the main without changing direction. The only switches you have to worry about are the ones on the main line. I plan on putting them on the same port of my AR-1 so that they throw and close at the same time with one command. This larger loop accommodates larger trains.

If the Easter Bunny brings me more #6 switches, I'm going to upgrade the double to a deluxe:



Here I can catch the train inside of the loop. There are two shades of red here, if you want to permit one train to be entering and another to be leaving at the same time you would use two reverse units, one on each shaded block. If you don't need to accommodate two trains then they could share one reverse unit. There is a tradeoff in this scenario; the length of a train cannot exceed the length of the shaded blocks leading into the loop. This means shorter trains than the double crossover.

There was some talk about branching a yard off of the reverse loop. I will probably do this off of the top or bottom curve, coming back in the area above or below the double track entrance to the loop.

Feedback will be appreciated.

 

I hope you've noticed, but since you didn't colour it, you might not have:
The wye on the right of your last couple of plans is also a reversing section and needs wiring up as such.
It's easy to spot, just trace one rail (say the outside one on the right hand side) as a train goes around the wye (without using the loop) and you'll see it can reverse polarity and short the rails

Assuming the right most vertical track on the wye represents "rest of layout", I'm not 100% how to wire the resulting reversing sections. I'd be inclined to make the crossover + both legs of the wye + both leads to the "reversing" oval one section, but then you've got four entry/exit points and only one train can cross one of them at a time.

Although, two trains on that neck would collide on the crossover, so maybe it's not so bad?

 

After a few min. of study I'm not seeing the wye on the right as a reversing section. Technically its not a wye, its two turnouts feeding two parallel tracks... or maybe I don't know all the useages of the term "wye".

The way I trace the rails there is no reason to reverse the tracks leading into the double crossover. But it is possible for one train to switch the autoreverse unit twice entering the inner loop... once coming out of the double crossover and once going into the inner loop itself.

If I'm missing something can someone word it differently or diagram it please. I"m not saying ATSF Admirer is wrong, I'm just saying I can't see what he's describing.

 

If you took that crossover out and truly made parallel tracks, you would not need ANY reversing units (because you couldn't reverse the train). Once you put that crossover in, you need them. And the problem comes when it is thrown to crossover - it would work fine without a reversing unit if left straight rail all the time.

Once you line the switch for crossover, you are no longer running two parallel tracks, you are bringing one track into the other which effectively creates a wye. Here is an example trace... from the bottom turnout coming off the main follow the outside (left hand rail) along the curve, through the crossover and onto the bottom rail of the lighter orange track. Now, follow that same rail from the same starting point straight up the main to the other switch, then reverse your direction along the curve and straight through the crossover. You will end up on the top rail of the lighter orange track. So you have the same line on both tracks... time for a reversing section. You effectively have 2 wyes in your third diagram (one coming off the main, one off the loop).

I would agree with the suggestion of both wye leads and the crossover being the reversing section. Because the crossover makes BOTH wyes, it has to be part. If you wire it correctly, you can run more than one train through it simultaneously. Make sure the reversing section is in "normal" operation during straight rail and "reverse" when in crossover and you're good. For example, a northbound train comes off the main. You cross it over to the lighter orange track to head counter-clockwise around the loop (reversing section in "reverse" here). Once the train clears the section goes back to "normal." A southbound train then comes off the main and goes straight-rail through the crossover on the lighter orange track to follow the reversing northbound counter-clockwise around the loop as the first train comes off the loop through the red track and straight-rail throught the crossover and heads south (simultaneously on the double-track). Once the second train completes the loop it then comes off on the red track and crosses over to head north (reversing section in "reverse" again).

You could do without the crossover, use two switches to bring it down to single-track and then back out to the loop to see what we are talking about if that helps you visualize it.

 

Both guys are right Lownen. When the crossover is thrown to cross over, you have a wye on the right side. Actually, you have two. Focus on either the upper left or lower left turnout of the double crossover, and ignore the rest of it, and you'll see them.

 

Interesting very interesting. I have two reversing loops wired into my layout. Since I don't have DCC it becomes a interesting task to wire in. Lot's of DPDT reversed toggles.

It appears to me that all three guys are right! The ones responding just before my entry.

Lownen, Nice art work on the reversing loops and variation

Have fun.

 

You have posed an interesting question Lownen, which is:
What is the best track diagram for bringing a train (or more than one) off the main from either direction to reverse it?

One workable solution would be to take what you have in your third picture, and make both red sections PLUS the double crossover be the single reversing section.

I don't think that's how I would do it, though...

 

Okay, I'm taking everyone's word for it... still haven't figured it out. But that means instead of buying another AR-1 I'll be needing one of these:

Digitrax.com: Digitrax Power Management System-PM42

This means that I'll also have to lengthen the approaches to the double crossover from the east so that I don't limit my train length so much.

If I tried to make both sections plus the double crossover a single reversing section like Ben suggested then I limit myself to one train entering/exiting at a time... right?

 

I've taken your trackplan and drawn on it to try to help understanding:


I've coloured in the right hand rail of the left hand loop Red, and bought that along the neck to the crossover.
Note that as long as the two tracks of the neck don't touch, you've got no short - just a DogBone neck with two tracks of opposing polarity.

But, tracing both lines through the crossover you can see the short. Does that help any?


I'm still not decided on where I'd separate the sections were I doing this one. It seems to depend too much on how many trains you want to operate around this construct at once; so that you don't have metal wheels shorting both ends of the reversing section at the same time (bad!)

 

I see the short, I just don't understand why the auto reverse units I specified won't take care of them. They would simply switch both coming into the reverse block(s) and going out as well.

I'm still thinking about it though. Maybe I won't see it until I build it and my Zephyr complains.

Thank you very much for being patient with me.

 

If you only want one train in the area at a time, I see no reason why any auto-reverser (such as the AR-1) wouldn't do the job.
Take the deluxe plan and Paint the crossover half-orange and half-red horizontally. Gap both rails at places marked in blue.

Use one auto-reverser for all the orange and red sections (i.e. ignore the blue line across the crossover); and bob's your uncle. The caveat being that only one train can enter or exit the whole coloured bloc at any one time.

Now, problems start to crop up if you want to run two trains around the area; that's what hurts my head too much. If you had an orange reverse module and a red reverse module, they'd end up "touching" across the crossover, and I'm not sure what the system would do if a train ran from one reverser to a second reverser. I'm thinking "have kittens" and/or fireworks. But I'm sure it could be done if you needed it.

Alright, it sounds like you've got a pretty good idea of what you want to do, so I think I'll stop rambling and go do something with my "layout"

 

Your "rambling" is very much appreciated!

 

To show your real problem, ATSF should have drawn his lines on the right side, where your main is. Then he wouldn't have been drawing across your reversing sections. It's the same pattern on that side, completely symmetrical.

 

Don't spend the money on the more expensive product!

No matter how much I look at this, I can't see the need for a second reversing section.

Put your single reversing section in the neck of the loop, INCLUDING the crossover, like we've discussed already. Just make every distinct section longer than any train with metal wheels.

Here's the thing...
If the crossover is not thrown, then all you've got is a long, loop shaped siding. When a train crosses a reversing section boundary, the AR-1 will align the polarity of the reversing section with the main, at all four places. So if a second train should cross another boundary, it shouldn't cause a problem because the polarity will already be aligned at that boundary as well.

If the crossover IS thrown, then you would have a power shutdown when you try to run two or more trains over the reversing section boundaries. BUT, that will be a good thing, because it will prevent what would almost certainly be about to happen, which is a physical collision at the crossover.

BTW, for handling multiple trains, I'd put a siding in the loop with those two extra turnouts.

Also, for the heck of it, attached is a different sort of solution that'd work basically the same. (Pardon my use of MS paint.)

 

If I'm right, no. That'd be true when the crossover is thrown, but in that case you wouldn't want two trains moving at once because they'd collide at the crossover anyway.

 

I stated that in my original post. Straight rail has parallel track and you can run simultaneously through the crossover and reversing section. Crossover you can only run one. And like these guys mention, there is already a simple physical matter about that anyway. Just make sure you wire the "normal" position for your auto-reverser so that it matches up with straight-rail and the rest of the layout.

 

Hi! I've been reading this thread with interest. I don't think anyone has mentioned gaps in the rails. No matter if it's DC or DCC, you need gaps, to stop shorts. Try tracing the polarity around the track as + & -, and see where they might meet. Thats where you need gaps in both rails. In your track plan, you may need quite a few. Depending on where you put feeders to the rails, will determine where you may need the gaps. If you don't have a book on basic DC wiring, get one, it will explan where you need these gaps, around turnouts, crossover's, etc. Even with DCC, you have to follow the rules for DC wiring, or you will have shorts. DCC is like the wiring in your house, touch both wires together, and you have trouble. I hope this helps, and doesn't make you more confused. Bruce

 

Thanks Bruce. I took for granted people would recognize from my diagrams where I wanted the gaps. Actually, I use Kato's Unitrack products. In order to gap Unitrack we replace the "Unijoiners" with insulating Unijoiners.

 

A simple either-direction reverse loop (or loops). This was on a layout built by a club as a combination display/club layout in space furnished at a hobby store.


It is NOT a place to stage trains, and cannot be used by two trains at once, and it does not allow to run through reverse loop unattended without stopping. But doggoneit, it is a railroad JUNCTION. Trains routinely have to stop for clearance/ signals at junctions, furgoodnusssake.
It allows reversing in either direction -or- continuous running on the mainline loop.
Continuous loop trains can stay on the back route through the tunnel...or can take the front route across the crossing one way, around the tunnel through the mountain and cross the OTHER way on the crossing. That's not something a prototype train would be likely to do, but you don't have to do it...

Gaps are shown.
More gaps are needed if a live-frog crossing is used.