Reversing Loop Conundrum, or is it two?

[ITG]

hi,

I'm planning a future layout, and I like complex(ish) track plans which give options for multiple routes; not least because I plan to use DCC, Z21 & iTrain to manage routes, so that trains can be running, circiling, reversing etc, whilst I shunt and handle arrivals and departures. (iTrain does support the combination of manual and automated running). But in the planning, I've stumbled across a conundrum involving a reversing loop, or is it two? I should add I'm familiar with reversing loops with DCC, as I have one which operates successfully on an existing layout using a  GM Prodigy Advance2 with a Gaugemaster auto reverse module.  I also use live frog points with various methods of switching frog power, such as Gaugemaster frog juicers, DCC Concepts ADS units and MTB point motors with switching. All/some of these can be/will be incorporated on the proposed layout.

 

The attached track plan is theoretical and simplified. The actual one I'm still scribbling on, and using Anyrail, will be significantly more complex, but the principle shown on the plan is a simplification of an intended reversing loop, inside a roundy-roundy circuit, but which can be approached in both directions.  The orange lines show where breaks would be, normally on the inside frog rails of points, but I guess these will need to be on both rails? Effectively they will be, as the short track lengths between pairs of turnouts AB, BC, DE and EF make them effectively crossovers with each turnout in the pair having an inside rail break. If my theory is correct, tunrouts B & E will be part of the reversing loop?

It seems to me the true reversing loop is that straight between X & Y (which in practice will easily accomodate my longest trains). But if accessing that X-Y length from, say turnout A and leave it via turnouts B & E to turnout D, then its not a reverse loop; its simply a passing loop. The same applies to access via turnouts C to F. So, I'm left thinking that a reverse loop auto module will come into play only when it needs to on the X-Y stretch. But how will this affect the frog polarities in turnouts B & E, as they will change polarity to allow a train approaching to pass? Will they therefore be in conflict with the rev loop module?  Or do I need something different to manage polarities?

I should also add that I will be using current sensors around the layout for train detection. ( XY will probably be a single block, and is likely to have 3 feedback sensors). That raises other questions.  I currently use current sensors in a test situation as I learn iTrain, and thus only need to 'sense' current on a single, always the same, rail. How will I need to arrange current sensors for XY, as the polarity will change? Where, between power source, and rail does the sensor module and auto-rev module go?

I see this - rightly or wrongly - as a wiring dilemma; hence the question on this forum, and not on the specialist iTrain forum. The mention of iTrain is only to give background.

 

If you've taken the time to read and understand my dilemma, you may have the answers I'm hoping for. Thanks in advance.

Ian

[KeithMacdonald]

Looks like a good candidate for radio-controlled engines running on unpowered track!

Then no worries at all about switching polarities.

You'd just have to worry about power to points motors or servos.

[Mike Buckner]

I don't know if this is practical at all, but a thought that occurs:

 

All engines that will traverse the central section to be fitted with high-capacity stay-alive.

 

All traversals to be completed in one move - i.e. no stopping in the central section.

 

Central section to be isolated and unpowered.

 

[WIMorrison]

You have challenges when using reversing blocks with automation programs because most, but not all, auto-reversers draw sufficient current when in their idle state to show the block as occupied, therefore trains will never enter under automatic control because the program will consider the block occupied.

 

This is solvable by using the correct type of auto-reverse module. In your case, the logical place to make the reverse section is all the track between the orange slashes you have placed over the track. This would appear to break the iTrain rules, however I believe there is a way to achieve your aim, and retain this track layout.

[NickC]

Make the reversing loops from A - C and from D - F

if you use Digikeijs DR5013 reversers everything will work with iTrain

[DCB]

5 hours ago, NickC said:

Make the reversing loops from A - C and from D - F

if you use Digikeijs DR5013 reversers everything will work with iTrain

I think it will also work with 1 (one) train.   Its like my abandoned loft layout, the problem is a) using more than one train, and b) any unplanned  loss of power.    For more than one train you probably need something a bit more sophisticated than bog standard one point motor one switch operation like Diode matrix route setting.   The plan looks interesting but a bit pointless, some indication of stations etc would be interesting but it looks like it would provide the operator(s) a pretty hectic time..

Mine merely sought to allow trains both clockwise and anticlockwise access to the layout from their hidden sidings and the problems were too expensive to fix.  That said I have to spend my £500 fuel bonus on something so maybe I can have another go.

[ITG]

Thanks all, some thoughts to ponder. It’s helped me to better understand what hardware I may need, I have now managed to find info about Lodi and DIgikejis products that may go a long way towards helping with this.

 

I have plenty of time to plan, as the room in question is not yet built. As it’s a only one part of an 18 week build which started last week, plenty of planning time. The room will be 5.25m x 2.5m approx, but I may try to keep one corner clear (a) because there’s a door and (b) as a workbench area.

What I’m trying/hoping to achieve, all with 00 double track, is

1. A high level terminus station

2. A roundy-roundy circuit

3. A separate goods yard area

4. A low level storage loops yard

5. A reversing loop(s) which can be accessed by trains travelling in either direction

 

I accept this is going to be busy, with hidden tracks needing to include the tighter curves.
The essence of the operation is for multiple trains (at varying intervals) to leave either the station or the goods yard, complete x number of circuits, be held in the storage loops (for varying durations), then reverse, and return to their origin. Because the station and goods yard are separate locations, trains won’t necessarily all have the same journey origins or ends, or even possibly will start/finish in the storage loops. Eg, intercity expresses which are not due to go to the terminus, but instead are just using the continuous run. Add all that together, and that’s why I think a reversing loop needs to be accessible to trains travelling in both directions.
One often sees reversing loops which can be accessed off, say, a circuit - but only by trains travelling in a single direction. Think of the traditional diagonal track across the centre of an oval. 
 

Here’s the layout thread which gave me the idea, and indeed helped to define the above 5 component parts, so thank you Bloodnok and Dongits.

 

[WIMorrison]

May I suggest that you look at YAMORC.DE which are new designs produced by the same designer of all the Digikeijs items and that have been redesigned and updated to take advantage of the latest technologies. This is especially valuable for you as he is gradually getting the components to build more and more capability.

Edited November 16, 2022 by WIMorrison
spelling ...

[DaveArkley]

3 hours ago, WIMorrison said:

May I suggest that you look at YAMORC.DE which are new designs produced by the same designer of all the Digikeijs items and that have been redesigned and updated to take advantage of the latest technologies. This is especially valuable for you as he is gradually getting the components to build more and more capability.

He needs to fix the website urgently, I'll not be buying products that I can't read about

[WIMorrison]

It is being repaired as we speak - it appears that an update by the hosting provider to the backend systems has broken this and several other sites that they host :(

[Harlequin]

4 hours ago, ITG said:

Thanks all, some thoughts to ponder. It’s helped me to better understand what hardware I may need, I have now managed to find info about Lodi and DIgikejis products that may go a long way towards helping with this.

 

I have plenty of time to plan, as the room in question is not yet built. As it’s a only one part of an 18 week build which started last week, plenty of planning time. The room will be 5.25m x 2.5m approx, but I may try to keep one corner clear (a) because there’s a door and (b) as a workbench area.

What I’m trying/hoping to achieve, all with 00 double track, is

1. A high level terminus station

2. A roundy-roundy circuit

3. A separate goods yard area

4. A low level storage loops yard

5. A reversing loop(s) which can be accessed by trains travelling in either direction

 

I accept this is going to be busy, with hidden tracks needing to include the tighter curves.
The essence of the operation is for multiple trains (at varying intervals) to leave either the station or the goods yard, complete x number of circuits, be held in the storage loops (for varying durations), then reverse, and return to their origin. Because the station and goods yard are separate locations, trains won’t necessarily all have the same journey origins or ends, or even possibly will start/finish in the storage loops. Eg, intercity expresses which are not due to go to the terminus, but instead are just using the continuous run. Add all that together, and that’s why I think a reversing loop needs to be accessible to trains travelling in both directions.
One often sees reversing loops which can be accessed off, say, a circuit - but only by trains travelling in a single direction. Think of the traditional diagonal track across the centre of an oval. 
 

Here’s the layout thread which gave me the idea, and indeed helped to define the above 5 component parts, so thank you Bloodnok and Dongits.

 

 

Hi ITG,

 

That's quite a list of requirements and I suspect that a plan that meets them in the space available would not look much like the topology in your opening question.

 

So it might be better to firm up the plan before worrying about reversing loop wiring.

 

Reversing loops are inconvenient space-hogs and bi-directional ones doubly-so!

 

[ITG]

2 hours ago, Harlequin said:

 

Hi ITG,

 

That's quite a list of requirements and I suspect that a plan that meets them in the space available would not look much like the topology in your opening question.

 

So it might be better to firm up the plan before worrying about reversing loop wiring.

 

Reversing loops are inconvenient space-hogs and bi-directional ones doubly-so!

 

Yes, Harlequin, I agree I also need to develop the actual track plan. But I also want to ensure that what I’m after - and may end up with - is actually technically within my grasp. Have you looked at Dongits? 
I know what the room dimensions should be but I’m loathe to firm anything up too far, until I can actually measure it, including door placement etc. I accept what I’m after may not be everyone’s cuppa, in terms of lots of track at the expense of scenic treatment but I will be trying to see what can or cannot be done within reason. I’m a fan of your plans and graphics so feel free to throw in ideas as this (potentially slow) journey progresses .

thanks.

Ian

[WIMorrison]

3 hours ago, Harlequin said:

Reversing loops are inconvenient space-hogs and bi-directional ones doubly-so!

I think that the only awkward thing about them is that they need to longer than the longest train using them (assuming metal wheels on rolling stock). Otherwise they are pretty much like any other bit of track on the layout.

 

Clearly the more complex the track plan, the greater the potential for them to exist - the more especially when circular layouts are involved but I haven’t found one yet that couldn’t be made to work - and I have seen some horrors! 😂

[Michael Hodgson]

 

 

21 hours ago, WIMorrison said:

In your case, the logical place to make the reverse section is all the track between the orange slashes you have placed over the track. This would appear to break the iTrain rules, however I believe there is a way to achieve your aim, and retain this track layout.

You also pointed out the problem of trains having to be shorter than the reverse loop at least with metal wheels.  I know it's only a sketch, but XY seems shorter than NickC's solution of AC and DF, so depending on the actual lengths, one solution may be more restrictive on train length than the other.

 

[WIMorrison]

43 minutes ago, Michael Hodgson said:

I know it's only a sketch, but XY seems shorter than NickC's solution of AC and DF, so depending on the actual lengths, one solution may be more restrictive on train length than the other.

 

But AC and DF is an expensive solution at double the costs of my suggestion (and more than double if DR5013 are used!) - plus as you say, it is not a scale drawing 😉.

[Crosland]

23 hours ago, WIMorrison said:

You have challenges when using reversing blocks with automation programs because most, but not all, auto-reversers draw sufficient current when in their idle state to show the block as occupied, therefore trains will never enter under automatic control because the program will consider the block occupied.

 

This is solvable by using the correct type of auto-reverse module. In your case, the logical place to make the reverse section is all the track between the orange slashes you have placed over the track. This would appear to break the iTrain rules, however I believe there is a way to achieve your aim, and retain this track layout.

 

It's solvable by not putting the reverse module downstream of the detection circuit. I.E. detect the section controlled by the reverser, not the input to the reverser.

 

[WIMorrison]

I have my reverse modules downstream of the detection units. As I said, you just need to be careful which units you buy. 😉

 

When you place the reverser upstream of the detection unit, as you suggest, then you will autoreverse all outputs on the detection unit (which may be 16), when you actually only need to use one, therefore you lose the use of 15 outputs 😪

 

 

[RobinofLoxley]

Going back to the original post a bit, I get the question as my layout stripped down looks similar and has two reversing loops, in my case in the locations BC and EF. They are obvious in my case as the other 'side' of the layout is more complex, but as @NickCpointed out, the loops themselves seem to be possible locations too. The layout is wired to have detection later, I just opted to do it in 2 separate stages. As far as frog switching is concerned I opted to have insulated frog turnouts. I dont want the discussion to veer off that way as there were a lot of reasons for my decision which I'm not going over again.

 

What I would suggest @ITGis that when you start to build, that whatever the track plan is you test at every step that adds something. Slips, cross-overs, turnouts, reverse loops. Once a reversing loop is installed and working, if it stops working later you know 99%+ its not the reverser but something added later, either track or its electrics, that produce the problem and it should be easy (i.e. make it easy ) to go back a step and reset. Large layouts are only more complex than smaller ones if they have lots of those items, not because the track is on 3 levels or has  a large fiddle yard.

 

 

[ITG]

To be clear for all who have/are contributing, the actual track plan will look nothing like the plan originally posted. That is simply a representation of the reversing loop track layout I’m considering. Distances in that representation bear no resemblance to the end result, but I am aware of the need to ensure reversing loop length is longer than maximum train length.

10 hours ago, RobinofLoxley said:

What I would suggest @ITGis that when you start to build, that whatever the track plan is you test at every step that adds something

Good advice. Not something I’d found necessary to do with previous layouts, although maybe I should have done!

[Bloodnok]

23 hours ago, Harlequin said:

loops are inconvenient space-hogs and bi-directional ones doubly-so!

Yes, they are ... but you can get sneaky with them too and hide them in unexpected places.

I have a double track triangular junction, which if built as you might think it should be, would have needed lots of reversing sections.
I also have a balloon loop storage yard, which would also need one.

But because the two are connected together via a double track ramp it worked out that by introducing a reversible third track in the centre of the ramp, all the required reversing moves could go through the one reversible centre line, and it became my only reversing section. Yes, the length of it does make a hard length limit on what can run, but a train long enough not to fit here also won't fit in my fiddleyard, and certainly won't fit in my terminus station, which is almost a metre shorter than the reversing section.

I have a computer running an NX signalling panel already, so adding in a DPDT relay and driving it from signalling and block occupancy data I'm already collecting wasn't hard. If you aren't starting at "NX panel with full block detection" doing what I did just for a DCC polarity reverser may be rather overkill.

The block detectors I use come in sets of 8, but I can wire each detector in the set individually -- it's not also a power splitting bus bar as it sounds like the ones discussed in this thread are. So I can have five detectors inside the reverser, and still use the other three for other things.  I needed five detectors in the reversing section to give the computer enough data to do the NX properly - it needs to know when the junctions are blocked, and when the train is in the berth track at each end, plus something for the centre of the section.

The reverser changes over in two circumstances. One is when a new route is set into the reversing section (which can't be done until it is clear).
The other is when the rear of the train (which yes, is to be detected electrically -- and I have a lot of resistors to fit to wagons to make this true...) is clear of the arrival junction and there is a path set away from the departure side.

The logic is just about dumb enough that I can stop and reverse a train in it too. A departing route can only be set once the junction is free (that ensures you have arrived properly), and it then just checks for when you stop hanging over the far end (which you shouldn't ever have been -- that would require passing a red signal to do that!)