# Double Crossover Electrical Interlocking



## Thelic (Jan 10, 2018)

I think I have this right....but would like confirmation before I get to soldering.

Questions:

Can I extend the frog sections (in green) like I have to protect the switches? If a train were to run into a switch not set for it then it would encounter zero voltage past the clearance point until the switch is thrown, right?
If 1 is fine, then can I extend the frog power from B (dark green) to act as the blue side of A. This would prevent trains entering from 1 and 2 if either A or B were set against them.
Is there more I could do with E and F? It's still possible for trains entering to get stranded between E and F.
Will I need any more gaps or does this just become an under table wiring puzzle.











Just for more complication. ABC and DEF are two different detection blocks to enable both mainlines to run at the same time when set straight. No crossing wires between blocks allowed.


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## Thelic (Jan 10, 2018)

As I currently see it:

Trains entering from 1 are always able to exit since they cant enter unless A and B are set for them. C and F act as a pair so nothing else blocks its route.
Trains entering from 2 are in the same situation as 1.
Trains entering from 3 can get stuck at F. E needs some sort of relationship with F.
Trains entering from 4 are in the same situation as 3.
Trains entering from 5 are always able to exit. if C is set for them and B and E act together then they can always exit.
Trains entering from 6 can get stuck at E. Again, there's a missing relationship between E and F.

As drawn nothing should be able to run against a switch, but it still doesn't protect the entire interlocking.


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## Dennis461 (Jan 5, 2018)

You need a gap between E F, on the green rail.


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## DonR (Oct 18, 2012)

I see these little 'ticks' at your turnouts...I assume they are 'gaps'.

Missing from your drawing and all important for the success of your
intent to protect loco from crashing into points set against it...are the
location of your track drops to bus. With all of the frog rail polarity switching
and gaps, you could end up with no voltage in some sections of
track. Make your 'gaps' bolder or of a 'loud' color...and show the
track drops as Red or Black.

Don


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## Thelic (Jan 10, 2018)

Gaps are shown in yellow, everything else is soldered together. Drops are shown in their respective color. The dark green at A/B is the frog power switched from B's tortoise.

All closure rails are connected to their corresponding stock rail.










Turnouts are modified as such, but without the option to bridge the point rails. In all cases I've moved the frog power to the next set of rail to feed back into the frog, just makes soldering easier.


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## DonR (Oct 18, 2012)

I'm drawing this out in Black/red...I can't follow all those colors.
But the first thing I noticed which will have to be corrected is that
you show a gap in all of the frog rails at ABCDEF. That would defeat
your derail protection by cutting power at wrong times. Normally,
with Electrofrog turnouts you must gap the frog rails but your
derail protection circuits do not want them.

The places where you show track drops would appear also to
defeat the derail protection.

What actual measurements are between A B and C? If tight, we may
not be able to use the 'dead section' circuitry but I have another solution.

If you are not using the Tortoise switched tabs we may be able to
use them to automatically throw points. Are they free?

After I get your response it may take some time to work this
chess game but hang in there in the meantime.

Don


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## Thelic (Jan 10, 2018)

I'm not sure if you are referring to the green ticks, or the thin black ones. The green ticks are feeders that match the frog polarity, the black are simply sections of track (not important)

I do see that if a train heading into the interlock on 5 encounters switch C thrown against it it will go from a Blue/Red circuit to a Red/Red circuit but since it has multiple pickup wheels it shorts down one side of the train into the previous block. It wont simply park, it will pop the breaker for both sections. This occurs in every case. Better than derailing a train onto the floor though as this is all hidden track.

The basic premise is to preferably pop the breaker alone rather than derail AND pop the breaker. In reality the tracks that are being connected to this have 30" or more buffer space compared to the longest train I can run, so I shouldn't have a problem with regularly testing the protection.

All of the turnouts are butt ended to each other, the stretch from E to F is ~12", this is constructed in N scale. All turnouts have their own Tortoise, one of the tortoise switches is needed for the frogs. A juicer would defeat the block detection.


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## DonR (Oct 18, 2012)

Much apologies...I sure would like to take back my post #6. My typing fingers got ahead of my brain...my idea would work with twin coil motors but
not the Tortoise. Ignore all of my #6. I'll go at it again after much more
thinking...this is a real 'poser' as some would say. I'll be back after a lot
more study.

I do understand what you are saying...that the main premise is to protect
the loco from derailing due to points set against it...and that you could
accept occasional short circuits that would protect the loco from points
set against it. I accept that, but would like to find a way to keep the
train running SAFELY, without short circuits. But then, I may be
tilting against windmills.

Don


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## Thelic (Jan 10, 2018)

That, like you alluded to earlier, would require an additional unpowered section before each switch. Probably where I've extended the frog rails.

Only problem is that you can get longer consists trying to push the lead loco because it will lose power first and simply stop. I'm told that this can lead to the second loco spinning its wheels in place, not good.

The other option is a stop command broadcast on the short section before a switch, some DCC systems can broadcast a "All Stop" using the programming track leads. If you couple this with inertia setting in the decoders you can get a train to glide to a halt, even prototypically. This is way too much extra wiring for my tastes. Maybe next time.

I think I prefer a simple shutdown, I'm running Digitrax BXP88's so each block has its own breaker. This means it wont effect anything except the immediate two blocks.


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## Thelic (Jan 10, 2018)

As for the original intent...I solved it last night.

We can make D pull its frog power through E's and F's Tortoise, such that it breaks when E is thrown and F is clear. However this is starting to get to be a lot of wires and frankly I don't think the tortoises have enough switches. As is it protects against derailments, unfortunately that's probably the limit.


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## DonR (Oct 18, 2012)

I quickly agree that since the turnouts butt against each other there's
no way to set up a 'killable' 'isolated' section. And if there was, the 2nd
loco in a consist of 2 would try to push the lead loco that was 'dead' and
spin it's wheels...which is why I was asking for
measurements....however, I doubt that the typical long N scale
train would have the thrust to push a 'dead' loco. 

And I do agree than any of the schemes to auto stop a loco facing
points set against, is going to mean wiring. 

You should have free switched terminals on your Tortoises
could control trackside signals that would warn about point
settings. My brother had that very arrangement on his
huge basement layout using Tortoises. It was very helpful
in a complex yard with 2 mains running thru it.

With the need to avoid shorts due to the frog change of
phase and the lack of trackage between turnouts it's looking
more and more like simple trackside signals controlled by the
Tortoises are going to be your best bet and easiest to install.

Don


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