DCC Question

 
  vrwalker Station Master

Can you put a passing loop within a reversing loop?

I will be using a Digitrax AR-1 Automatic Reversing Controller and use DCC Concepts Digital Cobalt switch machines, switching frog polarity with them.

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  bjviper Chief Commissioner

Location: Brisvegas
If it is completely encompassed within the reversing section, then there shouldn't be a problem.
  Aaron The Ghost of George Stephenson

Location: University of Adelaide SA
There will be a problem I you try and have two trains enter the loop from opposite ends at the same time.
  duttonbay Minister for Railways

How much distance is there between the points which form the reversing loop and the crossing loop points?
  Aaron The Ghost of George Stephenson

Location: University of Adelaide SA
That measurement doesn't change the answer.
  Kevin Martin Chief Train Controller

Location: Melbourne
There will be a problem I you try and have two trains enter the loop from opposite ends at the same time.
Aaron

Depending on the track plan, i.e. a single track mainline with a single point for the reversing loop, then 2 trains cannot enter from opposite ends at the same time.
It would help if the OP were to provide a simple sketch.
  duttonbay Minister for Railways

That measurement doesn't change the answer.
"Aaron"

Surely it does. If one of the lengths of single track is longer than a train length, then a reversing unit could be fitted there, with only ever one train triggering it at one time.  That would mean the crossing loop is not even located within the DCC reversing section.
  hosk1956 Deputy Commissioner

Location: no where near gunzels
Surely it does. If one of the lengths of single track is longer than a train length, then a reversing unit could be fitted there, with only ever one train triggering it at one time. That would mean the crossing loop is not even located within the DCC reversing section.
duttonbay

The passing loops can become reversing sections rather than the reversing loop itself? but would that mean you would have to have two ARC's, one for each passing loop? could the reversing loop be configured to operate with two ARC's like this??
I would presume if you were to do that (passing loop within a reversing loop) that you would be wise (better off?) to make the passing loops the full length of the reversing loop, ie, butt the passing loop points up to the reversing loop points.

Wayne
  duttonbay Minister for Railways

The passing loops can become reversing sections rather than the reversing loop itself? but would that mean you would have to have two ARC's, one for each passing loop? could the reversing loop be configured to operate with two ARC's like this??
I would presume if you were to do that (passing loop within a reversing loop) that you would be wise (better off?) to make the passing loops the full length of the reversing loop, ie, butt the passing loop points up to the reversing loop points.
"hosk1956"

Once you have a totally isolated section of track inside a reversing loop, powered through a reversing unit, then whatever is outside that section is effectively (electrically) connected to the rest of the layout directly. The only bit which reverses is withing the isolated section.  There's no reason why both loops in a crossing loop located in a reversing loop could not be treated as individual (electrical) reversing sections - there would be no interaction, and simultaneous entry from each end would be fine.
  miktrain Deputy Commissioner

Location: Adelaide SA
...There's no reason why both loops in a crossing loop located in a reversing loop could not be treated as individual (electrical) reversing sections - there would be no interaction, and simultaneous entry from each end would be fine.
duttonbay

[color=#333333][size=3][font='Open Sans', Calibri, Arial, Helvetica, sans-serif]duttonbay[/font][/size][/color] that sort of would work but uses two reversers

Actually the OP has not given enough info for a proper answer. [color=#333333][size=3][font='Open Sans', Calibri, Arial, Helvetica, sans-serif]vrwalker[/font][/size][/color] please enlighten us on the situation ie track/train lengths and point positions.

All answers given so far are both correct and wrong, as all are assuming different situations and looking at the problem from different angles.

If the passing sidings are long enough to hold all lengths of trains then it could be wired without any reverser at all, regardless of the lead lengths, by making both sidings floating blocks. It would only require two relays and have the points switch in tandem to opposite tracks. It is quite simple wiring and if you want to know more [color=#333333][size=3][font='Open Sans', Calibri, Arial, Helvetica, sans-serif]vrwalker[/font][/size][/color] just ask and I will post a diagram.

Tony
  Aaron The Ghost of George Stephenson

Location: University of Adelaide SA
Once you have a totally isolated section of track inside a reversing loop, powered through a reversing unit, then whatever is outside that section is effectively (electrically) connected to the rest of the layout directly. The only bit which reverses is withing the isolated section. There's no reason why both loops in a crossing loop located in a reversing loop could not be treated as individual (electrical) reversing sections - there would be no interaction, and simultaneous entry from each end would be fine.
duttonbay

This does not work! You have one train going 'forward' entering a loop, it is going to reverse through it. You have an opposing train going in 'reverse' into the loop, it is going to forward through it. Which polarity is your loop? Is it reversing for the first train or forwarding for the second train? Think fast... The answer is both trains are shorting and your reverse loop module is extremely confused and about to let the smoke out.
  miktrain Deputy Commissioner

Location: Adelaide SA
If the passing sidings are long enough to hold all lengths of trains then it could be wired without any reverser at all, regardless of the lead lengths, by making both sidings floating blocks. It would only require two relays and have the points switch in tandem to opposite tracks.
miktrain

In fact just having a second thought if there is only a single point in and out of the loop then this could all be wired very simply without any need for a reverser, no problems at all, and you can have as many sidings in the loop as you like.

Tony
  duttonbay Minister for Railways

Don't need to think fast. The electronics does it for me.  Each of the two lines through the passing loop has a reversing unit. So each will reverse independently. The tracks outside the passing loop are not switched at all, only the sections between the isolating gaps just on the inside of the frogs. Would you like a picture?

As I said earlier, it does need two reversing units.

If there's more than a train length between the reversing loops points and one end of the passing loop, then a single reversing unit will work too, hence my first question about lengths.

Unfortunately the OP seems to have disappeared and has not responded to any of the questions or suggestions.
  NSWGR1855 Deputy Commissioner

Don't need to think fast. The electronics does it for me. Each of the two lines through the passing loop has a reversing unit. So each will reverse independently. The tracks outside the passing loop are not switched at all, only the sections between the isolating gaps just on the inside of the frogs. Would you like a picture?

As I said earlier, it does need two reversing units.

If there's more than a train length between the reversing loops points and one end of the passing loop, then a single reversing unit will work too, hence my first question about lengths.

Unfortunately the OP seems to have disappeared and has not responded to any of the questions or suggestions.
duttonbay

I can't see why you need any electronic reverse unit if the passing loop is in the return loop, as first asked. All rails in the loop other than the frogs are wired with the return loop. The passing loop frogs can be switched using point motor contacts the usual way. Simply using the reverse loop point motor contacts handles the reverse loop polarity.


Terry Flynn.
  vrwalker Station Master

Thanks for all the replies.

I see I have been confused when asking the original question.

The track is single line powered by a track bus.

The operating system is a Digitrax entry level DCC controller.

The return balloon loop is quite large and the bus for this area is switched by the AR1 reverse loop controller, which is doing what it should without having the point motors wired in.

The switch machines are digital Cobalt machines that are powered from an accessories bus, wired the same polarity as the track bus.

The passing loop is entirely within the return balloon loop that has polarity switched by the AR1.

So do I power the switch machines from the 'return loop' bus or the main track/accessories bus?

I prepare all my Peco points as per instructions on the Wiring for DCC website.

There are breaks in the track as per the Digitrax instructions.
  NSWGR1855 Deputy Commissioner

Thanks for all the replies.

I see I have been confused when asking the original question.

The track is single line powered by a track bus.

The operating system is a Digitrax entry level DCC controller.

The return balloon loop is quite large and the bus for this area is switched by the AR1 reverse loop controller, which is doing what it should without having the point motors wired in.

The switch machines are digital Cobalt machines that are powered from an accessories bus, wired the same polarity as the track bus.

The passing loop is entirely within the return balloon loop that has polarity switched by the AR1.

So do I power the switch machines from the 'return loop' bus or the main track/accessories bus?

I prepare all my Peco points as per instructions on the Wiring for DCC website.

There are breaks in the track as per the Digitrax instructions.
vrwalker

The short answer is to wire the switch machine track frog connections to the return loop track power. The DCC decoder driving the switch machine can be connected to your accessory buss. I normally refer to switch machines as point motors, saves confusion with an electrical switch.

Terry Flynn.
  PeltonPinch Locomotive Fireman

This does not work! You have one train going 'forward' entering a loop, it is going to reverse through it. You have an opposing train going in 'reverse' into the loop, it is going to forward through it. Which polarity is your loop? Is it reversing for the first train or forwarding for the second train? Think fast... The answer is both trains are shorting and your reverse loop module is extremely confused and about to let the smoke out.
Aaron

The way around this is to use four reversing modules.

One for each approach track (and associated point) in the loop, and one for each parallel track.

There is still the risk that a train could enter a parallel track from either end, but short circuit protection should handle it. It may well serve as an effective collision protector as well!
  miktrain Deputy Commissioner

Location: Adelaide SA
...The return balloon loop is quite large and the bus for this area is switched by the AR1 reverse loop controller, which is doing what it should without having the point motors wired in.

The switch machines are digital Cobalt machines that are powered from an accessories bus, wired the same polarity as the track bus.

The passing loop is entirely within the return balloon loop that has polarity switched by the AR1.

So do I power the switch machines from the 'return loop' bus or the main track/accessories bus?

I prepare all my Peco points as per instructions on the Wiring for DCC website.

There are breaks in the track as per the Digitrax instructions.
vrwalker

If the system is working fine now, adding a passing loop within the reverse loop will not change that electrically but it may change it "mechanically" as now there may be trains entering and leaving the reverse loop at the same time depending on the actual track layout. This is why to get the right answer you should post a plan (simple sketch is fine) or a very detailed description.

Is there only one point to enter/leave the loop? If so, you don't even need a reverse loop controller and don't need to isolate the frog, only the outside rails and just have a relay to flip polarities when the point is switched.

The signal for the switch machines can come from anywhere, logic would suggest the reverse loop bus as best for later problem solving if needed. Track power for the frogs of the passing sidings must come from the reverse loop track power, that way it will always be the right polarity.

I don't like DagyTrax so have not read, and won't comment on their wiring instructions.

Tony
  miktrain Deputy Commissioner

Location: Adelaide SA
The way around this is to use four reversing modules.

One for each approach track (and associated point) in the loop, and one for each parallel track.
PeltonPinch

That is just plain over kill, do you have shares in a reverse controller company?

Tony

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