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Reverse Loop Control with DC Power

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Posted by SeeYou190 on Tuesday, April 6, 2021 10:48 AM

richhotrain
But, I have a one word reaction to DC reverse loops - - ugh! Thank goodness for DCC.

Thank you for the comment.

Absolutely true... DCC makes reverse loops so much simpler.

Maybe I should add a fourth question to me DCC or DC questions about reverse loops.

-Kevin

Wink Happily modeling my STRATTON & GILLETTE RAILROAD. A Class A line located in a personal fantasy world of semi-plausible nonsense on Tuesday, August 3rd, 1954.

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Posted by richhotrain on Tuesday, April 6, 2021 10:50 AM

SeeYou190

Absolutely true... DCC makes reverse loops so much simpler.

Maybe I should add a fourth question to my DCC or DC questions about reverse loops. 

I have often thought that a Sticky on DCC reverse loops and reverse sections should be authored - - much like this thread on DC reverse loops.

Rich

Alton Junction

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Posted by ATLANTIC CENTRAL on Tuesday, April 6, 2021 11:14 AM

richhotrain

Interesting and worthwhile thread.

But, I have a one word reaction to DC reverse loops - - ugh!

Thank goodness for DCC.

Rich

 

Well Rich, my new layout only has one, and it is not part of mainline operation, it is just a staging return on the WESTERN MARYLAND branch line. And it will be easy and logical to operate. And, you will not see it, it will be hidden.

I do have the wye, but that too will be semi automatic. If you are in the staging yard, and want to leave that leg of the wye and come back out on the main, all you is set the wye for the direction you want to go on the main, east or west, which only takes one button. Than you just set the direction on your wireless throttle to that same direction.

Your train will pull out of the staging and proceed on the main. Going in you just set the turnouts and pull in, nothing to do. 

To leave, you just have to think "when I reach the mainline which way am I going?" That is the way your throttle direction needs to be set.

Relays and turnout position do the rest.

So let's say I'm headed west on the main with a train and I want to turn the whole train on the wye and go east.

My steps are:

Push one button to set the wye to allow the west bound diverging route into the wye/staging.

Make sure I am pulling into a staging track that is available, push one button if needed to select a track.

Pull the train in until it clears the wye.

Push one button to align the wye for west bound exit from the staging.

Now, which way is my train going? It is still going west. So I don't change my throttle direction. Start the train, it will now back out of the staging and move west bound in reverse around the wye.

After you are fully on the mainline, reset the the wye turnouts to the main, again done with one button. Which way is your train facing now? East. 

Change your throttle direction to east, and proceed.

You have not pushed one more button, or flipped one more toggle switch (in fact no toggles were flipped), or aligned one more turnout, than you would have with DCC.

You just have to think in terms of east and west, not forward and reverse.

The throttles have two buttons side by side with little arrows, pointing left (west) or right (east), easy enough.

As you move around the layout, left is always west, right is always east, the trains never turn themselves around in relationship to your view.

That is why you are "inside" the benchwork at all times.

Even If I used DCC I would build my layout that way, always viewing the trains as if I am facing "north". Layouts built for operation are much easier to understand and learn if you do this.

Sheldon

    

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Posted by SeeYou190 on Tuesday, April 6, 2021 11:50 AM

ATLANTIC CENTRAL
Well Rich, my new layout only has one, and it is not part of mainline operation, it is just a staging return on the WESTERN MARYLAND branch line. And it will be easy and logical to operate. And, you will not see it, it will be hidden.

I added a description of the reverse loop on my next SGRR layout to the opening post in this thread. It will be simple and logical to operate as well.

ATLANTIC CENTRAL
I do have the wye, but that too will be semi automatic.

I did a wye in the Scale Rails of Southwest Florida N scale boxcar layout.

The tailing track of the wye was wired to a 4PDT switch. This switch changed the polarity of the reversing tail and the Tortoise at the same time.

Super-easy!

ATLANTIC CENTRAL
You just have to think in terms of east and west, not forward and reverse.

I always think in left and right. For some reason my brain does not interpret compass directions in a train room.

-Kevin

Wink Happily modeling my STRATTON & GILLETTE RAILROAD. A Class A line located in a personal fantasy world of semi-plausible nonsense on Tuesday, August 3rd, 1954.

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Posted by richhotrain on Tuesday, April 6, 2021 12:57 PM

ATLANTIC CENTRAL
 

My steps are:

Push one button to set the wye to allow the west bound diverging route into the wye/staging.

Make sure I am pulling into a staging track that is available, push one button if needed to select a track.

Pull the train in until it clears the wye.

Push one button to align the wye for west bound exit from the staging.

Now, which way is my train going? It is still going west. So I don't change my throttle direction. Start the train, it will now back out of the staging and move west bound in reverse around the wye.

After you are fully on the mainline, reset the the wye turnouts to the main, again done with one button. Which way is your train facing now? East. 

Change your throttle direction to east, and proceed.

You have not pushed one more button, or flipped one more toggle switch (in fact no toggles were flipped), or aligned one more turnout, than you would have with DCC.

Sheldon, my reply, which follows, is not meant to be argumentative but rather observational.

The operation of that part of your layout seems complex. I count four buttons to be pushed in addition to throwing turnouts. I haven't stopped to figure what would be required to conduct that same operation in DCC.

On my DCC layout, it is essentially a dogbone with reverse loops at both ends. But, visually, you would not see any "reverse loops" because the layout is large and the loops at both ends don't appear to be loops because the middle of the layout (which is the bulk of the layout) is a 4-track mainline controlled by four double slips, all wired in phase.  

What I actually have to deal with the loops are what I call four "reversing sections" of straight track that end with gaps leading into and out of the loops. Four auto-reversers controls the four reversing sections. So, I have to do nothing as the mainline trains enter and exit the loops. It is all handled automatically by the four PSX-ARs.

Whenever I want to switch a train from one mainline track to another, I manually throw spring-loaded Peco turnouts and/or double slips. But those movements don't happen often because in that area of my layout it is mostly high speed mainline running of trains.

That is the beauty of DCC.

Rich

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Posted by Lastspikemike on Tuesday, April 6, 2021 2:14 PM

The reverse polarity wiring problems are the same for DC or DCC. You can more easily automate DCC ironically because you can exploit the short circuit.

I think the OP has more than two reverse polarity sections of track.  The extra set of isolating joiners proposed will partially address one of the two additional reverse loops but not the third. 

Each reverse loop requires two isolating gaps at each end of the reverse polarity section. Normally that is at or near the frog rails of the turnout creating the loops, but it doesn't have to be.

When you have a diagonal connecting track you create two facing reverse polarity loops if you install the connection inside any form of oval be it dogbone or whatever.

I saw yet a third reversing loop outside the two in the diagram because there is a very long section of double track which becomes a single track at some point towards the opposite end of the continuous running oval. Isolating just the crossing diagonal track won't solve the whole problem.

Alyth Yard

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Posted by Dave K on Tuesday, April 6, 2021 3:52 PM
I have two sets of insulated joiners, one at the beginning of the turnback and one at the end of the turnback
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Posted by Dave K on Tuesday, April 6, 2021 3:54 PM

Kevin,  now only concerned about the one reversing loop.  I have insulater joiners at the ebeginning and end of the revers loop.

 

Dave

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Posted by ATLANTIC CENTRAL on Tuesday, April 6, 2021 7:02 PM

richhotrain

 

 
ATLANTIC CENTRAL
 

My steps are:

Push one button to set the wye to allow the west bound diverging route into the wye/staging.

Make sure I am pulling into a staging track that is available, push one button if needed to select a track.

Pull the train in until it clears the wye.

Push one button to align the wye for west bound exit from the staging.

Now, which way is my train going? It is still going west. So I don't change my throttle direction. Start the train, it will now back out of the staging and move west bound in reverse around the wye.

After you are fully on the mainline, reset the the wye turnouts to the main, again done with one button. Which way is your train facing now? East. 

Change your throttle direction to east, and proceed.

You have not pushed one more button, or flipped one more toggle switch (in fact no toggles were flipped), or aligned one more turnout, than you would have with DCC.

 

 

Sheldon, my reply, which follows, is not meant to be argumentative but rather observational.

 

The operation of that part of your layout seems complex. I count four buttons to be pushed in addition to throwing turnouts. I haven't stopped to figure what would be required to conduct that same operation in DCC.

On my DCC layout, it is essentially a dogbone with reverse loops at both ends. But, visually, you would not see any "reverse loops" because the layout is large and the loops at both ends don't appear to be loops because the middle of the layout (which is the bulk of the layout) is a 4-track mainline controlled by four double slips, all wired in phase.  

What I actually have to deal with the loops are what I call four "reversing sections" of straight track that end with gaps leading into and out of the loops. Four auto-reversers controls the four reversing sections. So, I have to do nothing as the mainline trains enter and exit the loops. It is all handled automatically by the four PSX-ARs.

Whenever I want to switch a train from one mainline track to another, I manually throw spring-loaded Peco turnouts and/or double slips. But those movements don't happen often because in that area of my layout it is mostly high speed mainline running of trains.

That is the beauty of DCC.

Rich

 

Rich, first there are several different things being discussed just in my post and your reply. So let me explain and separate them.

Regarding turning a train on my wye, when I say "set" the wye, those buttons I am pushing ARE the turnout controls. This does assume my train has already been given authority to use this section of the mainline, but even that requires only two additional buttons to be pressed and then left alone.

So as my train proceeds west, I push one button that aligns the two turnouts that will divert me from the main and thru the branch of the wye into the staging yard.

You would have to manually throw two turnouts.

Because the wye leads into a staging yard, entering the yard requires a clear track. Only if not already selected, that would require pushing one button that will throw the necessary turnouts, however many it takes in the yard ladder automaticly, and it would direct the power only to the selected track, all automaticly with one button.

I have pushed two buttons, you would have manually thrown a minimum of three turnouts, possibly more.

The train clears the wye and stops.

I push one button, and now the turnouts necessary to let the train out of the other leg of the wye are all properly aligned. And the polarity of the staging yard "branch" of the wye is reversed automaticly.

You would have had to manually throw two turnouts and reversed your throttle direction.

I power up my train, without touching the direction buttons on the throttle, my train now backs up, because even through the train is now backing up, it is still proceeding WEST on the layout.

The train backs out of the wye onto the mainline, now facing the opposite direction from when I entered.

After I clear the wye, I push one button that realigns the wye turnouts to allow thru traffic on the mainline.

My train is now facing east. I push my EAST direction button on my throttle and proceed east back the way I came.

You would have had to align two manual turnouts and reverse your throttle direction again.

Again assuming I already had authority on that section of the main, I would have pushed a maximum of four buttons, possibly only three, and changed throttle direction once.

You would have thrown at least 6 manual turnouts, possibly more for the staging yard, and changed throttle direction twice.

The point is it did not take me any more actions, or any great complexity to turn the train on the wye compared to DCC.

Keep this in mind, turning a train on a wye is a separate idea from your dogbone layout reversing issues.

Leaving my WESTERN MARYLAND branch line out of the conversation for now, my layout does not at any point contain a track arrangement like your dogbone layout.

A train going west NEVER goes around a loop and becomes an EAST bound train on a track parallel to the track is was moving west bound on.

Trains on the ATLANTIC CENTRAL portion of my layout are always EASTBOUND or WESTBOUND unless turned on the wye or rebuilt in the yard where there is a turntable to turn locos.

Next issue - Your dogbone layout - YES, you are correct that your layout would be bothersome to wire for DC.

No judgement here, and no disagreement about the advantage of DCC here, but personally I would not choose a dogbone track plan no matter the control system. It simply does not fit my desired operational scheme.

Important point - when you view my new layout, or any of my recent old layouts, you are inside a large double track squiggly oval. Left is always WEST, right is always EAST. And until you go thru a crossover they are two separate isolated loops.

There are no reverse loops on the ATLANTIC CENTRAL mainline. A west bound train does not disappear into staging and then return from that same tunnel as an east bound train.

If allowed to proceed all the way thru the staging, it reappears at the other visable end of the mainline still as a west bound train.

When a train moves thru a crossover from one mainline track to another on my layout there are no polarity issues, there are no special switches to set, no reverse loop toggles. Again, because there are no reverse loops. 

The wye is the only way to turn a whole train on the ATLANTIC CENTRAL portion of the layout.

The single track WESTERN MARYLAND branch line is a different story, better explained with drawings I don't have handy. But, it is a single track branch line and its operation is different from the ACR mainline.

I hope this makes sense.

Below is the track plan for other readers who may be trying to follow this.

Sheldon

  

    

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Posted by SeeYou190 on Tuesday, April 6, 2021 10:43 PM

Dave K
Kevin,  now only concerned about the one reversing loop.  I have insulater joiners at the ebeginning and end of the revers loop.

Did fully insulating the section of track help with the problem?

-Kevin

Wink Happily modeling my STRATTON & GILLETTE RAILROAD. A Class A line located in a personal fantasy world of semi-plausible nonsense on Tuesday, August 3rd, 1954.

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Posted by Dave K on Wednesday, April 7, 2021 6:52 AM

Kevin,

All of the support posts finally made me realize that I needed to add insulated joiners to the main line block to insulate it from the remaining main line track.  This means adding two more sets of insulated joiners.

Dave

 

 

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Posted by KitbashOn30 on Wednesday, April 7, 2021 7:39 AM

There is an extrememly simple and hassle free solution to the reverse loop (and wye) situation but so many modelers just ignore it - all you have to do is model electric traction with the overhead wire as one side of the electricity delivery circuit and the rails paired as the other side, the reverse loop problem does not and can not happen! Big Smile

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Posted by richhotrain on Wednesday, April 7, 2021 7:44 AM

ATLANTIC CENTRAL

The point is it did not take me any more actions, or any great complexity to turn the train on the wye compared to DCC.

Keep this in mind, turning a train on a wye is a separate idea from your dogbone layout reversing issues.

Leaving my WESTERN MARYLAND branch line out of the conversation for now, my layout does not at any point contain a track arrangement like your dogbone layout.

A train going west NEVER goes around a loop and becomes an EAST bound train on a track parallel to the track is was moving west bound on.

Trains on the ATLANTIC CENTRAL portion of my layout are always EASTBOUND or WESTBOUND unless turned on the wye or rebuilt in the yard where there is a turntable to turn locos.

Next issue - Your dogbone layout - YES, you are correct that your layout would be bothersome to wire for DC.

No judgement here, and no disagreement about the advantage of DCC here, but personally I would not choose a dogbone track plan no matter the control system. It simply does not fit my desired operational scheme.

Important point - when you view my new layout, or any of my recent old layouts, you are inside a large double track squiggly oval. Left is always WEST, right is always EAST. And until you go thru a crossover they are two separate isolated loops.

There are no reverse loops on the ATLANTIC CENTRAL mainline. A west bound train does not disappear into staging and then return from that same tunnel as an east bound train.

If allowed to proceed all the way thru the staging, it reappears at the other visable end of the mainline still as a west bound train.

When a train moves thru a crossover from one mainline track to another on my layout there are no polarity issues, there are no special switches to set, no reverse loop toggles. Again, because there are no reverse loops. 

I don't want to take this thread off topic by comparing our two layouts.

But on the subject of trains always going in one direction, it is inevitable except on point-to-point layouts. But, what I imagine as I operate my trains is that I am viewing a linear layout in which trains are always running East or always running West. The track just happens to connect over a long oval which the viewer does not perceive.

As for this thread, it is all about reverse loops and trains move West through the loop and return East. Reverse loops in DC require several gaps and switches to be thrown. On layouts like mine, operating in DCC, the auto-reverser(s) do it all automatically, not  manually. That is my only point in expressing a strong preference for DCC over DC.

Rich

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Posted by ATLANTIC CENTRAL on Wednesday, April 7, 2021 8:04 AM

Agreed, I just wanted to show that DC reverse loop and reverse polarity issues can be dealt with in a number of ways that do not involve flipping switches while the trains are running.

Yes, DCC allows the trains to just run anywhere, without regard for polarity or block boundries. And for some track plans, and some layout concepts that is an important benefit.

For other track plans and concepts, not as much.

My other point is this, I don't need or want reverse loops as part of my mainline to accomplish my goals, so toggle switches or expensive auto reversing equipment is not a factor for me either way.

The one reverse loop I will have will be hidden from view and still be easy to operate, only used to stage trains on the branch line.

It is all about what your priorities are.

Sheldon

    

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Posted by SeeYou190 on Wednesday, April 7, 2021 8:11 AM

KitbashOn30
There is an extrememly simple and hassle free solution to the reverse loop (and wye) situation but so many modelers just ignore it - all you have to do is model electric traction with the overhead wire as one side of the electricity delivery circuit and the rails paired as the other side, the reverse loop problem does not and can not happen! 

Catenary and 3-rail (Marklin/Lionel) are great systems that solve all kinds of problems. So is outside third rail, that was used in O scale for a long time.

-Kevin

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Posted by Dave K on Wednesday, April 7, 2021 10:05 AM

The Atlas Wiring Book, Page 31,  explainss how to fix my problem, I believe.  Need to add more gaps.

 

Dave

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Posted by SeeYou190 on Wednesday, April 7, 2021 11:45 AM

Dave K
The Atlas Wiring Book, Page 31,  explainss how to fix my problem, I believe.  Need to add more gaps.

I do not have the Atlas Wiring Book.

I hope you can resolve everything.

-Kevin

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Posted by Lastspikemike on Thursday, April 8, 2021 8:23 AM

Dave K

The Atlas Wiring Book, Page 31,  explainss how to fix my problem, I believe.  Need to add more gaps.

 

Dave

 

I have the 2003 edition.  Page 31 is part of Chapter 4 that deals with powering a DC layout through multiple cabs and common rail block system. There's nothing there to help with polarity problems caused by reversing loop tracks or wyes.

The key to solving your problem is to trace the rails one side at a time and see where the two rails are joined into a single rail. Anywhere you have that situation you need to create an isolated two rail section long enough to accommodate your longest train. A single set of two gaps will solve the short circuit but only until a metal wheel bridges the gap, then you'll get a short through the wheel. Only by creating long separately isolated sections separating the short points and each such section controlled by a DPDT can you prevent short circuits while running trains. Every point where the rails join has to be isolated and DPDT controlled in a long enough section of track to isolate the entire train.

"Reversing sections" are like an electrical airlock: as the train approaches the short circuit point you "open" the entry door to this airlock by setting the DPDT for that section to match polarity under the train as it crosses into the reversing section. Then only after the entire train is safely within the airlock you open the door at the other end by setting the DPDT for the main line to match the polarity under the train. That reverses the polarity at the main line end of the section your train just left but that doesn't matter because, unlike real airlocks your entry door automatically closes due to the isolating gaps. You'll see right away that you cannot match the exit polarity by flipping the DPDT for the reversing section. The train would immediately reverse back out of the reversing section. 

You may find Chapter 5 which deals specifically with reversing loops (and wyes) and especially pages 38 to 40 (if you have a different edition the page numbers may differ but the Chapter you want is a Chapter 5 ).

I think you have a combination of the situations in figures 5-10, 5-12 and 5-14. You seem to have a reversing polarity crossover track connecting two sides of an oval loop and two conventional balloon reversing loops and they seem to involve nesting within each other. If I am correct then you will find it tricky to locate exactly which sections of track require isolating and control by a DPDT.

Chapter 2 page 14 shows the schematic for wiring two DPDT switches for one reversing loop (figure 2-6). You need a DPDT for each reversing loop and one for the "main".

Alyth Yard

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Posted by Dave K on Thursday, April 8, 2021 8:45 AM

I am now aware of the need to block off the adjoining and turnback blocks.  I'll let all know what happens.

 

Regards,

Dave K.

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Posted by Lastspikemike on Friday, April 9, 2021 9:02 AM

Reading the April issue of MRR magazine and the DCC reversing loop article on pages 46 and 47.

Instead of trying to automate the polarity/phase change whether for DC or DCC the article reminds us that polarity/phase change can be triggered manually when the turnout is lined from entry to exit from the reversing loop/section.

Allan Gardner describes this as a NSDR or non short detecting reverser.

I described mine in the "other" thread. The polarity/phase change uses a relay triggered DPDT (mine is an Atlas snap relay, the discussion of which derailed the other thread right at the outset). Tortoise motors have this capability internal to their motors for frog polarity control.

NSDR can be used for DC or DCC with no change in the wiring layout. The difference is only in the timing of throwing the turnout. For DCC the turnout can be lined for the exit as soon as the entire train is within the reversing loop. For DC you must wait until the locomotives leave the reversing section but before they reach the turnout. DCC layouts using NSDR can have a longer reversing section on the same footprint.

When I realized the issue with our DC layout I extended the main line polarity about one flex track piece inside each end of our shortest reversing loop. That's enough for the electric wheelbase of our two AC4400 or our ABBA C liner consist. Our shortest reversing loop is shorter than it otherwise could be by using the NSDR connected to the turnout switch. To allow for this we intend to wire each of those end/entry sections as separate blocks. For DC we will connect power to the main line so the locomotive consist can leave the reverse section before the turnout is thrown (which reverses polarity inside the reversing section). For DCC it won't matter so we can instead then connect those same sections to the power supplied to the reversing section lengthening the usable section of the loop. 

The other two reversing loops were very long anyway, a dogbone loop with two crossovers which creates the situation in the diagram at the bottom right on page 47 of the article. Our crossovers are separated by 15' or so of pseudo double track  mainline creating nicely useful passing sidings, accessible in both directions.

On that note Gardner points out that you can choose whether the crossover section is mainline or the loops are. We chose the crossover giving us two independently powered blocks created by each reversing loop, in addition to the 16 blocks we have using Atlas Selectors. Center off DPDT switches for each reversing loop combined with isolating gaps create blocks that can be powered off as well as polarity reversed.

Reversing loops are no different electrically to ordinary power districts in DCC and act the same as double isolated  blocks in DC. The advantage of DCC is phase change doesn't change locomotive direction of travel. So, in a way, DCC doesn't treat a reversing loop any differently to any other power district. For DC there is a big difference in the effect on locomotives as they cross the rail gaps between blocks as compared to inside a reversing section, but not for DCC. 

 

Alyth Yard

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Posted by Dave K on Thursday, April 15, 2021 9:55 AM

I gave up n the two DPDT switches to control the turnback and have gone back to one.  Still having difficulty synchronizing the DPDT switch when the train leaves the block and enters the main line.  

 

Dave

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Posted by SeeYou190 on Thursday, April 15, 2021 10:05 AM

Dave K
I gave up n the two DPDT switches to control the turnback and have gone back to one.  Still having difficulty synchronizing the DPDT switch when the train leaves the block and enters the main line.

When using one, you should stop the train in the reversing section, change direction on BOTH the DPDT for the reversing section AND the power pack, then continue as normal.

SeeYou190
Operation: The turnout and reverse loop DPDT must be aligned for the incoming train. The train is stopped in the reverse loop section. Then the direction switch on the power pack, the polarity switch for the reverse loop, and the turnout direction are all switched.  Then the train can continue on the run.

I hope this works.

Please only use this thread for future questions to avoid duplicate postings.

-Kevin

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Posted by Dave K on Thursday, April 15, 2021 10:47 AM
I figured it out.  Run train into post reverse loop block.  Stop train and flip DPDT switch and power pack direction and go.  I cannot figure out why I am getting a short with DPDT switches but I will eventually solve.  I will also add a rectifier to the DPDT switches as you recommend.

Dave

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Posted by Lastspikemike on Thursday, April 15, 2021 1:56 PM

It shouldn't be necessary to stop the train. As long as the entire train is within the reversing section isolation points you simply reverse polarity of the main line while the train ls within the loop.

if your DPDT switches are shorting then you've accidentally connected a red powered rail to a black powered rail somewhere. Each DPDT should connect to its own reversing section and one of them should replace the function of your powerpack reversing switch. When you wire the reversing sections through their own DPDT then you also need to wire your main through a DPDT. If you don't install separate polarity control for both the main and the reversing section then you have to stop the train and change two polarity switches. The reversing switch on your powerpack is just a DPDT wired into the case. You need to bypass that completely by connecting the powerpack first to a DPDT and then to the main line rails.  You do the similar for each reversing section: wire direct from the power pack output to the DPDT and then to the rails. Atlas Twin switches do this for you internally. The positive terminal from your powerpack connects to the input positive terminal on each DPDT in parallel, same for the negative terminal. The output from each DPDT connects to a pair of rails in each section of track you need to independently control polarity.

Technically and electrically speaking there is no "main line", just three isolated sections of track independently controlled for polarity. Wiring a reversing section is no different to wiring a power district (DCC) or block (DC) assuming no common rail is used. A reversing section is just a separate block if double isolated. Reversing sections MUST be double isolated. You cannot include them in any section of common rail wired layout. 

You're halfway there.

How many reversing sections did you find in the end? 

Alyth Yard

Canada

  • Member since
    January 2009
  • From: Maryland
  • 10,530 posts
Posted by ATLANTIC CENTRAL on Thursday, April 15, 2021 7:57 PM

When Dave, or anyone, posts a reasonable drawing of the layout in question, I will offer my serious opinion on how to wire it.

Without such information, myself and others have already offered plenty of "theory" on the subject.

Base on the pictures posted of this layout in the other thread, I have my doubts that there is any really good solution.

And yes, I have some set rigid ideas about good layout design and DC control - based on 50 years of experiance and some very good teachers, who in their day helped put men on the moon and designed top secret radar.

Lastspikemike - I understand your theory on this, but feel as though you are not explaining yourself well for those who don't already understand the topic fully.

And I doubt that your approach would be very effective on what appears to be a very small layout. Of course your theory/method works, but it fails several basic operational requirements in my view.

Just my opinion, but reverse loops on small layouts are not practical.

As Dave seems to be finding out, they are cumbersome and complex.

I am a DC user, but I have long said that small layouts actually benefit from DCC in ways that do not matter as much on larger layouts.

So, here I am, waiting to see an actual track plan to offer a complete system wiring diagram that will work.

Sheldon

    

  • Member since
    January 2017
  • From: Southern Florida Gulf Coast
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Posted by SeeYou190 on Thursday, April 15, 2021 10:07 PM

ATLANTIC CENTRAL
When Dave, or anyone, posts a reasonable drawing of the layout in question, I will offer my serious opinion on how to wire it.

Sheldon,

Dave has been communicating directly with me via email about the issues he has been having and working towards the best solution.

He has a good handle on the problem, and is learning the realities of DC reverse loops in a very hands-on manner.

The responses in the thread don't quite tell the whole story.

-Kevin

Wink Happily modeling my STRATTON & GILLETTE RAILROAD. A Class A line located in a personal fantasy world of semi-plausible nonsense on Tuesday, August 3rd, 1954.

  • Member since
    January 2009
  • From: Maryland
  • 10,530 posts
Posted by ATLANTIC CENTRAL on Thursday, April 15, 2021 10:18 PM

SeeYou190

 

 
ATLANTIC CENTRAL
When Dave, or anyone, posts a reasonable drawing of the layout in question, I will offer my serious opinion on how to wire it.

 

Sheldon,

Dave has been communicating directly with me via email about the issues he has been having and working towards the best solution.

He has a good handle on the problem, and is learning the realities of DC reverse loops in a very hands-on manner.

The responses in the thread don't quite tell the whole story.

-Kevin

 

That's fine, glad you are trying to help. I have felt from the very beginning that there was not enough information. 

And if the layout is anything like how it appears in the photos, than it will be difficult at best to create an easy operational senerio.

Sheldon

    

  • Member since
    June 2020
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Posted by Lastspikemike on Friday, April 16, 2021 8:25 AM

The only complexity to reversing loops is timing the main line polarity change. You switch one DPDT at a time as the train rolls along.

Otherwise, wiring a reversing section is exactly the same as for any other isolated block. 

If you persist in using the powerpack reversing switch and a reversing section switch you will find reversing loops hard to use.

If you are not using common rail wiring then you can wire every block with a DPDT block power switch. I don't. I just wire one rail to a SPDT switch. Atlas 215 Selectors are handy for this. With a DPDT to a block you can control both power and polarity for the block which can be handy for some. I chose to use a version of common rail (one rail throughout the main line of the layout is connected to a bus wire) even though all blocks are double isolated.   

You cannot use common rail wiring in any reversing section. To understand why just try and wire up an Atlas 220 controller. Or look at the schematic of the 220 in the Atlas wiring book. For an even more interesting exercise try ganging and wiring three Atlas 220 with three reversing sections.....to three DC cabs (I don't think it can be done but if somebody knows then post how).

Size of the reversing loop is important. It needs to be longer than your longest train if you use metal wheels on all your rolling stock. 

Size of the layout has no effect otherwise. Reversing loops on large layouts can be hard to identify. The OP has chosen to build a relatively small layout but quite complex electrically.

A sketch is all we would need to identify where the isolating gaps need to go. Once you identify the track sections that are isolated you just power each such section separately with two feeder wires. You power each pair of feeder wires INCLUDING all the feeder pairs that are considered  "main line" (I.e needing the same polarity all the time) with their own DPDT taking power direct from the powerpack to the isolated section. All the main line feeders are powered from one DPDT. 

You control track polarity only with the appropriate DPDT. You stop using the powerpack reversing switch. The powerpack switch reverses polarity for the entire layout defeating the separate polarity control of all your reversing loop DPDT switches.

Or, you can stop your train and then have to throw two DPDT. One of those DPDT is the one on the powerpack. 

Stopping the train only to reverse track polarity twice simultaneously should inform anyone what's wrong with using the powerpack reversing switch when you have a reversing loop.

Alyth Yard

Canada

  • Member since
    January 2017
  • From: Southern Florida Gulf Coast
  • 12,106 posts
Posted by SeeYou190 on Friday, April 16, 2021 8:37 AM

Lastspikemike
If you persist in using the powerpack reversing switch and a reversing section switch you will find reversing loops hard to use.

The opening post, and the intent of this thread, was to present in a factual way, four different ways of controlling a reversing section in DC.

You are continuing to champion one way of doing it, and I am glad that worked for you, but that is not the intent of this discussion.

People try different ways, and do what works for them.

The opening post has been edited to include how I resolved the reversing section on my planned layout, including the operating scheme. One DPDT will work perfectly for my plan. Using the reversing switch on the power pack is actually the easiest way to use the reverse loop in my situation.

-Kevin

Wink Happily modeling my STRATTON & GILLETTE RAILROAD. A Class A line located in a personal fantasy world of semi-plausible nonsense on Tuesday, August 3rd, 1954.

  • Member since
    June 2020
  • 1,931 posts
Posted by Lastspikemike on Friday, April 16, 2021 8:40 AM

But you have to stop your train inside the loop. Then throw two reversing switches before starting up again. 

How can that possibly be easier than throwing just one switch and not stopping the train?

Alyth Yard

Canada

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