# Double-crossover reverse loops



## DonStaff

I have a doubl-crossover separationg dog bones on opposite sides if the top level of a 3-level layout. I posted this question on TrainBoard, and got a lot of good advice, some of which I've incorporated, but I'm still not totally cleat on exactally how to hook up the wiring.
I'm working on final plans for modifications to a train club N-scale layout.

The first attached file shows the present three-level layout with dotted lines representing the location of grades that enable movement between levels. The design allows switching between either DC or DCC operations. DPDT center off switches at the beginning (lower) and end (upper) points of the inclines that connect the three levels insolates the three power packs (one for each level.) The center off switch positions connect to short track sections with insulated rail joiners at each end. Having to go through the center off switch position prevents inadvertantly shorting between two power packs. This is all for DC operation. In DCC operation, a DPDT switch allows switching from any level's power pack to a Digitrax Zephyr. This arrangement allows our club members to choose whether they want to run DC or DCC equipment for a given operating session. This all works perfectly well.


On the top level is where the double crossover divides the teo dog bones as shown in the second drawing. 

Now, for the time being, ignore the wire from the DPDT switch that would connect the "DC" terminals of the switches to the power bus. IE. the layout would be wired for DCC only. That being said, do I have all of the wires connected correctly for DCC operation? If not, which connections do I need to change?
Thanks in advance for your help.


Don


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## DonR

Here we go with the Don and Don show.


This is a very interesting layout. Lots of activity.

I see why you elected to isolate the 2 loop ends but
there is a problem.

The layout main lines are actually EITHER a figure eight,
OR a simple oval.

The difference is the way the double crossover points
are set. If all 4 set to divert it is a figure eight. If all 4
set to straight it is a simple oval.

Draw out the mains with a red and a black pencil
representing the 2 rails and you have no short circuits.

BUT

If you go through the crossing and around a loop then
go STRAIGHT by-passing the crossing you have a polarity
mis-match. 

We had a similar issue on another thread last month. The
solution was easier for him, since he used 2 pair of turnouts
and no crossing. 

At first it would look that tracks to be isolated are the 2 'bypasses' that
make the main an oval. But they are not long enough
as drawn. One other option would be to make the entire
double crossover an isolated section, but it also is not
long enough.

Is it too late to consider eliminating the double crossover
and use 2 pair of turnouts instead? In addition, we would need
more track length for each isolated section so that a loco isn't
spanning both ends of it at the same time, and that you are not
running lighted passenger cars.

Now, if you could make each of those 2 'by passes' long enough
to accomodate the longest train with lighted passenger cars they
could become your solution.

Something will have to be changed to make the layout work with DCC.

Also, it looks like you'll have quite a mess of switches and
wires to make it work as a DC layout.

Let us know your thinking.

The other Don


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## DonStaff

Thanks Don,

I think it is too late to consider eliminating the double crossover
and use 2 pair of turnouts instead. I considered that in the beginning, along with a turntable or wye on this level, but there is just not enough right of way to do it with anything but a double crossover. The function of the crossover is of course to enable locos to go back down the grades head first, and that is indispensable. Isn't there some way that reversing modules can be made to compensate for the reverse polarity created when the crossover is set tto cross?

The other Don


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## DonR

Sometimes a 'light' will 'light' while shaving, but I just don't
see how you can resolve the polarity problem without going
to 2 pair of turnouts and a crossing...there are crossings that
match the degree of the double crossover.

Each pair of turnouts would be farther back up the main from the crossing
both above and below the crossing. I see it would be crowded below
the crossing, tho. That would permit us to make the 'arms' of
the X as the isolated areas, they would still be shorter than
desirable, but it would make it possible to have the same 
operations as the double crossover. These 'by passes' would
be much longer but still might be a problem for LONG lighted
passenger trains. (if loco wheels span one end of isolated section
and lighted car wheels the other end you would have a short).
You would still need 2 DCC reverse loop controllers.

Using the double crossover itself as the isolated section would
work electrically, but that would be 4 entrances and the likelihood
that more than one loco would access it thus a short circuit. In
addition it's just not long enough.

And, as I said, you'd really go whacky trying to make this work
as DC manual control.

See what you can do to get close to my suggestion above.

Don


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## DonStaff

Don,

The following has been recommended as a solution: Making the loop to the left of the double crossover the reversing section, and doing it with a DPDT relay controlled by the crossover; That when running DC this would reverse the train so it would be a good idea to stop the train before throwing the crossover, and that with DCC you could just throw it and keep on rolling.

Does this seem feasible to you?


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## DonR

The polarity mismatch problem is not with the two loops.

You actually have a simple figure eight main line. There
is no polarity problem with that.

But when you add the ability to by-pass the crossing and
connect loop to loop, there is a mismatch.

When a DCC reverse loop controller operates it must
match the track phase (polarity) TWICE. First when
the loco spans the entry insulated joint and the second time
when the loco spans the exit insulated joint. As you
mentioned, it is fully automatic and the train does not
even pause.

Your DPDT relay would match only one time and a 
mismatch would occur at the exit insulated joint.
Even if it did work, you would have to have a means
to disconnect the DCC reverse loop controller from
the track when it was DC. Keep in mind when you
reverse polarity on a DC track you cause the loco
to go THE OTHER WAY.

Draw a simple take on your layout, just the figure eight
and the double crossover. Take a red
and a black pencil and draw the basic figure eight and
the two by passes. Red for one rail, black for the other.
You will see where the red meets the black thus a short
circuit.

However, that light may have come on. I did a lot of red and
black drawing and it looks like we can do this a simple and
easy way, simply declare the entire double crossover to
be your MAIN for this purpose. Both loops would be
isolated and each fed juice by a reverse loop controller. (2)
You would put insulated joiners where the four turnouts
meet your tracks. It would get the track power from
your main DCC controller. This is required since you cannot
have 2 reverse loops abutting each other, there must be
a 'main' between them, short as it may be.

This resolves another issue, each loop has only the main line
access points. Even so, the likely hood of 2 locos entering
at the same time can cause a short circuit.
These isolated loops are far too long but they do let you
have long lighted passenger trains.

I also have concerned about yard and spur track activity. Those
tracks would also be access points to the reverse loops.

Frankly, I don't know how you can do all this as a DC layout.

Don


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## RT_Coker

Don,
The op is on at least two forums. There is one solution here: http://www.trainboard.com/grapevine/showthread.php?156844-DC-DCC-Wiring&p=1023204#post1023204 at post number #47.
It would be good to have somebody like you check it out.

If you can't see the picture, here it is:









Bob


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## powersteamguy1790

RT_Coker said:


> Don,
> The op is on at least two forums. There is one solution here: http://www.trainboard.com/grapevine/showthread.php?156844-DC-DCC-Wiring&p=1023204#post1023204 at post number #47.
> It would be good to have somebody like you check it out.
> 
> If you can't see the picture, here it is:
> 
> 
> 
> 
> 
> 
> 
> 
> 
> Bob


Don:

The above diagram is the way to wire your double crossover and reverse loops. It isn't at all complicated.


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## DonR

Bob 

Your mention of a 'black box' and the
double crossover somehow controlling the
phasing that I didn't follow.

Yes, Your drawing is what I was proposing in my previous post,
except that I was using the insulated joiners
at all double crossover track joints. Your drawing looks good because it
is a one black line drawing.

This layout could be considered a large oval.
Or it could be considered a figure eight.

The problem shows up when you do a red rail/black rail drawing. You encounter
phase mismatch anytime the turnouts are set for 'bypass' of the crossover
If you wire for a figure eight.

If you wire for a large oval, anytime you set the turnouts to using
the crossing you encounter a phase mismatch within the double
crossover itself.

There is no interconnection between the straight thru tracks on
a double crossover as you speculated, so that is not a concern.
But, remember, a double crossover is usually used to move a train
from one parallel track to another. The right rail is the same on
both left and right tracks. In this layout it is used to
connect the bottom half of an oval to the top half and there's 
the rub. The left rail is Red on the left track and right on
the right track, so the crossing causes a short.

Two pair of turnouts would solve the whole thing and
still give the nearly the same operating abilities.

Moving the insulated joints back as in your drawing does not completely resolve 
the problem. It looks fine until you do a red rail/black rail drawing.
On your drawing anytime you used the crossing you have a mismatch.

The more I look at it I'm not sure my solution would work either. More
and more I think that going to 2 pair of turnouts is going to be the only
solution as I said from the beginning.

Bob, do the red rail/black rail drawing and see if you see what I see.

In addition, You are aware the club wants this to work for both
DCC and DC. I have no idea how to do an automatic
DC system for this layout.

Don


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## RT_Coker

Don,
Things are getting too mixed up.
Here is a copy of the solution that I am talking about.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~








Donstaff,

On another forum you ask about a “DPDT relay controlled by the crossover”. 

Here is another way this layout level could have the track sections separated and wired. It shows what may be the simplest way as an example that can maybe help you figure out what you want. It also assumes that the original power connections and added track-isolation-gaps are not present. 
If I am not mistaken your Kato crossover is isolated so that all four track-connections are electrically independent of each other. This is represented by the red-circle on this crossover. The green connections provide fixed-phased power to the right track-section and adjustable-phase power to the left track-section. The black-box contains the “DPDT relay controlled by the crossover”.

The crossover is set for either a dog-bone loop or a figure-eight loop, and the relay sets the phase of the left track section accordingly. Of course for safe operation the train should typically be inside one section when the crossover is changed, and DC trains inside the left track section should be stopped first. 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Bob


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## DonR

Bob

See my post # 9 above yours and let me know what you
find.

Don


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## RT_Coker

Don,
In reference to post # 10. I may be missing something, but it seems simple to me. 

The loop can obviously be set up as either a dog-bone or a figure-eight without any problems for DC or DCC. As a dog-bone the left and right outer most rails of the loop are the same phase (say + DC). As a figure-eight the left and right outer most rails of the layout would be opposite phases. So if the double crossover is setup only to operate loop as a dog-bone or a figure-eight, and switching the double-crossover also switches the phase of the complete left side of the loop (with say a DPDT relay), then there is a switchable choose between dog-bone and figure-eight that works for both DC & DCC (provided the DC trains in the left track-section are first stop for this switch). The phase of the complete right side of the loop stays fixed because of the DC/DCC track that exits this level. The only rail-gaps that are actually used are those of the double-crossover.

The black-box is the DPDT relay or something equivalent. I believe if one is going to try and run DC and DCC on the same layout, that it is a good idea to keep the operation as simple as practical.
Bob

I probably should be using the word “polarity” instead of “phase” in this post.


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## DonStaff

Bob and Don,

I very much appreciate your discussion and would like to be able to post my latest drawing which clarifies the electrical connection points. If either of you could explain how to upload my updated drawing I would also appreciate that. Suffice it to say that there are no electrical changes to the drawing.

Don, am I correct in understanding that, with your proposed solution, the DPDT switches that I show in my drawing enabling switching the left and right side isolated sections between DC and DCC would not be necessary? Also, could you show or describe any other changes to the drawing to more accurately illustrate your solution?

Donstaff


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## RT_Coker

A red-black line drawing of a switchable dog-bone/figure-eight loop. When the double-crossover switch is changed the phase (or polarity) of the left half of the loop is also reversed. The blue line is where the rails are gapped. The right half power feed is a fixed polarity connection and the left half is a reversible polarity connection through a DPDT relay that is switched in conjunction with the switching of all four turn-outs of the double-crossover.
Bob


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## DonStaff

Bob and Don,

I think I have figured out how to upload my updated drawing clarifying the electrical connection points. It may not be correct though, as it appears that with Bob's solution, only one reversing device would be required and that the DPDT switches to allow switching between DC and DCC might also not be needed. 

Is the DPDT relay referenced in Bob's solution equivalent to reversing modules such as the Digitrax AR-1 and the Mrc AD520? 

The red and black lines along with the blue line depicting the isolation of the double crossover were very helpful, but I'm still a little foggy.


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## DonR

Bob

Very engenius. Yes, I see, I didn't understand what track section
the DPDT was going to affect. Your black/red rail drawing is
very clear.

They could use a plain single coil DPDT if their turnout motors
are Tortoise, but would need a latching relay if they use
twin coil motors.

As you said, it would work for either DC or DCC and does away
with the need of any reverse loop controllers.

But they will have to gap the double crossover straight tracks
in the middle where you indicate with the blue line.

I love relays. I have built a radio station automation system
using relays in a circuit that could count which would permit X plays from
A tape and Y plays from B tape.

Don


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## RT_Coker

DonStaff said:


> Is the DPDT relay referenced in Bob's solution equivalent to reversing modules such as the Digitrax AR-1 and the Mrc AD52.


Not if you want to run DC trains on the loop.



DonR said:


> But they will have to gap the double crossover straight tracks in the middle where you indicate with the blue line.


Yes, thanks Don! I missed that. 
From the pictures I see on the web, the two outmost rails of the double-crossover will have to be modified to add these missing gaps.

[Makes me wonder why the Kato double-crossover does not come with them already gapped so that it would be directly usable in more configurations. System engineering is defiantly not one of the strong points of the hobby! But it does give us forum users a lot to talk about.] 

This raises another possible problem. What (if any) are the internal power connections to the frogs inside the double-crossover? I searched the web, but it was not much help.

DonStaff ,
Unless I here different, I will assume that adding gaps to the two outmost rails of the double-crossover is not an acceptable solution for you.
Bob


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## DonStaff

Bob and Don,

Referring to Bob's earlier solution:

"...On another forum you ask about a “DPDT relay controlled by the crossover”. Here is another way this layout level could have the track sections separated and wired. It shows what may be the simplest way as an example that can maybe help you figure out what you want. It also assumes that the original power connections and added track-isolation-gaps are not present. If I am not mistaken your Kato crossover is isolated so that all four track-connections are electrically independent of each other. This is represented by the red-circle on this crossover. The green connections provide fixed-phased power to the right track-section and adjustable-phase power to the left track-section. The black-box contains the “DPDT relay controlled by the crossover”. The crossover is set for either a dog-bone loop or a figure-eight loop, and the relay sets the phase of the left track section accordingly. Of course for safe operation the train should typically be inside one section when the crossover is changed, and DC trains inside the left track section should be stopped first. 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~~
Bob"


You both seem to agree that the DPDT relay solution will work for both DC and DCC, that with it, no other reversing modules will be needed, and it also assumes that the original power connections and added track-isolation-gaps are not present. The attached drawing shows what I understand to be that wiring change. Please let me know if I have this right.

I examined the Kato double crossover and discovered that the blue vertical line on the double crossover in Bob's last-submitte drawing does not exactly depict the switch's make-up. One of the outside rails (either top or bottom in the drawing) of the Kato 20-210 is not gapped. It is solid from end to end. The opposite outside rail, along with all of the other rails are gapped. Does this make a difference?


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## DonR

Don

I think Bob will agree the wiring as in your latest post is
exactly what is called for in the DPDT relay system.

It's my opinion that you must have a gap in both rails
of both straight double crossover tracks in order to make the system work.
You are going to be reversing both DC polarity and DCC phasing
and I don't think a common rail can do that.

I do want to point out that when running DC trains you would
want to make sure none is running in the left loop isolated area when
you push a double crossover button to change routes. If
the train was running when you did, it would start
going in the opposite direction since the DPDT would
reverse polarity. This applies only to DC. 
The decoder would ignore the phase change during
DCC operations.

Don


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## DonStaff

Don,

I have included 2 images for reference of the Kato double crossover that I referred to in my last post. Also included is my layout drawing showing possible locations for the insulated rail joiners. If these locations are not correctly positioned, please advise me on where they should be placed.


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## DonStaff

DonR,

In your post reply (#16), you said, "They could use a plain single coil DPDT if their turnout motors are Tortoise, but would need a latching relay if they use twin coil motors." Later in the same post, you said, "But they will have to gap the double crossover straight tracks
in the middle where you indicate with the blue line." To clarify, the four switches on the mainline, of course including the double crossover, are all Kato, but I don't know which kind of relays that kato switches the solution would indicate that I would need. The other four switches (for the switchbacks), on the level are manually thrown Pecos.

Hope this helps.

Donstaff


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## RT_Coker

DonStaff said:


> One of the outside rails (either top or bottom in the drawing) of the Kato 20-210 is not gapped. Does this make a difference?


Donstaff,
Both outside rails must be gapped!
Bob


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## DonStaff

Thanks Bod,

Please refer to the two attached drawing, noting that the two rails are represented by a single line. The rails are already gapped at the points labeled as insulated rail joiners in the first image. On the double crossover, however, (see other attached image), the top rail is not gapped from the manufacturer. All of its other rails are gapped. Do I also need to gap this top rail of the double crossover? And, are the insulated rail joiners in the proper position?

Donstaff


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## DonR

Don

The DPDT relay is to be controlled by the double cross over
motors. Tortoise uses 'stall' motors, so they are controlled
by a simple SPDT switch, the power stays on to the motor
even after it completes the throw. That power would hold in
a simply DPDT relay, and release it when thrown the
other way, thus reversing the phase/polarity of the left loop.

The Twin Coil machines are controlled by a momentary
push button. The power is off after the throw is completed.
Thus you would need a twin coil DPDT LATCHING relay that would
pull in AND STAY IN until the other coil is activated when the
push button changes the points again.

The information on the Kato turnout motors is not all that
clear but they seem to be the twin coil type which uses a momentary
push button or switch. The instructions to your crossover should
give you correct information or a KATO N scale user could tell us
for sure.

If they are twin coil, you would need a LATCHING DPDT relay. They
are readily available from electronic supply houses. You would need
one with 12-14 Volt Coils and DC or AC depending on your turnout
motor supply source. The Relay contacts should have at least a
5 amp capability at 14 to 20 volts.

Both rails of both straight tracks on the DOUBLE CROSSOVER would
have to be gapped. I couldn't tell from the pic but it looked like
only one was in each straight track. A razor saw or dremel cutting
wheel could cut whatever is needed.

All of the insulated joiners that you have indicated in your
drawing would no longer
be desirable. The entire left loop would be fed by the DPDT relay.
The entire right loop would always stay the same polarity/phase.
So only the gaps cut into the crossover straight tracks where
Bob shows the blue line are all that should exist.

Don


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## DonStaff

Don,

Thanks to Steve Jackson, Northern Virginia NTRAK: T-TRAK Division, here is a description of the Kato # 20-210 N-scale double crossover: "There are four switch machines packed in side of there along with some wires. The copper-colored coils influence the magnets which are located in the black plastic actuating pieces and cause the turnout to throw."

Can you tell from the two attached pictures whether the relay that I would need would be the latching type as you suspected?


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## DonStaff

Don,
Sorry, the image with the red lines really referred to a modification that Steve Jackson was making to the double crossover. The second image, showing the inside, is the one to reference to see if you can tell which DPDT relay type I would need.
Donstaff


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## RT_Coker

Don,
Some Kato turnout information here: http://www.rr-cirkits.com/Notebook/Kato-Switch-Machine.html.
Bob


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## DonR

Don


The link Bob posted describes the Kato turnout motors to be a single
coil unit that requires a momentary pulse of a MINIMUM 15 V DC.

Therefore:

1. The power source for your turnouts must be at least 15 v dc.

2. You will need a latching relay, DPDT with 15 or 16 volt DC
coils since it will be actuated by the momentary pulse that
will throw your points. It should have minimum contact
capability of 5 amps.

Mouser Electronics is one supplier you might try
if you don't have a local dealer.

http://www.mouser.com/?gclid=CjwKEA...ZfvQ6d8b5TFeG8vCNhlzWW1POMcx9VBcZuBoC3Hrw_wcB

I would recommend calling them with the specs and let them
recommend from their selection.

Don


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## DonStaff

Thank you so much Bob and Don and to everyone else who has contributed to this discussion and to Model TrIn Forum for providing this valuable platform to the model railroad co,munity.

Don Stafford


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## DonStaff

DonR,
I have updated and attached my drawing to show the latching DPDT relay recommended by Mowser. I have two additional questions. 1. Do you think that the operation or control of the double crossover by a Kato 24-840 turnout control switch could be affected by adding the gap to the top rail? 2. If needed, could additional drops from the bus be added on either or both sided of the crossover and if so, where?
Donstaff


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## DonR

There was no link to the Mouser relay.
I do see in your relay 'box' that it is a 24 V
relay. What voltage will your turnout power
source have?

I doubt that the Kato controller would have
a problem with the gap in both rails of both
straight sections. It takes power from a separate
source, to throw the points and the new
relay, not track power.

No, you would not want to add drops to the 
double crossover. Since we have eliminated
all insulated joiners it will pull power from the
tracks to which it is joined to keep your
trains running.

Don


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## DonStaff

The Mouser relay I ordered was #655-RT424A24, rated for 24v. My understanding from the gentleman at Mouser was that it would work.


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## DonR

Do you have a 24 v dc power supply for it and the double crossover turnouts?

Don


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