# Rail Gap Fill



## beepjuice (Sep 17, 2014)

What do you use to fill rail gaps? I know the rails should be tight but sometimes a gap occurs and I just can't always close it to my liking. Do you use anything to smooth these out?
Thanks


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## JNXT 7707 (May 5, 2013)

I'd say the rail gaps don't always need to be so tight. Depending on your layout and where it is situated, you may need those gaps for expansion.

As an aside, I am always amazed when I look at the trackwork of modular layouts at train shows and museums. I've seen some gaps that shocked me, looked like about a sixteenth of an inch or so. The trains rolled over it like nothing was there.


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## LateStarter (Mar 12, 2016)

Don't worry about gaps...
You'll need them during and after weather/season changes.


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## mesenteria (Oct 29, 2015)

LateStarter said:


> Don't worry about gaps...
> You'll need them during and after weather/season changes.


:thumbsup:

You need some gaps, especially in a climate where you can't control the mood swings...I mean the humidity swings... and your benchwork is milled lumber. However, the trick is to keep them small, just enough that your rolling stock don't hitch going over them, but large enough that they do allow for some shrinkage of the track system as the benchwork dries seasonally and compresses, or shrinks, as a result. I try for a bit less than 1/8" and not less than 1/16". I avoid them on curves, but they should be innocuous on tangent track.


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## DonR (Oct 18, 2012)

To fill a gap in a rail, cut appropriate length
from a scrap rail and insert it. Usually this is at
a joiner. If you file off the lower flanges it will
fit into the joiner nicely. A drop of CA glue will
hold it in place.

You can also insert a sliver of plastic if the gap
is not too wide. 

Don


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## CTValleyRR (Jul 26, 2014)

I don't fill gaps. In my view, anything big enough to require filling indicates bad track alignment which will just cause problems with operations later on.

My layout is in a climate controlled area, and all the exposed wood is painted, so expansion and contraction with humidity is minimal.


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## Chet (Aug 15, 2014)

I also never fill gaps. When I cut gaps, usually with a Dremel tool, I try to locate the gaps in a straight section of track if possible and never bother filling them. I do have a spot or two that are in a curve, but still never have any problems wit them.


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## santafealltheway (Nov 27, 2012)

beepjuice said:


> What do you use to fill rail gaps? I know the rails should be tight but sometimes a gap occurs and I just can't always close it to my liking. Do you use anything to smooth these out?
> Thanks


I typically cut a teeny tiny piece of rail and slide it into a rail joiner, in the center, then connect and solder it together.


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## traction fan (Oct 5, 2014)

*Gap filler*



beepjuice said:


> What do you use to fill rail gaps? I know the rails should be tight but sometimes a gap occurs and I just can't always close it to my liking. Do you use anything to smooth these out?
> Thanks


beepjuice;

After reading through this thread I agree with the general consensus about leaving gaps for expansion, but there are some gaps I do fill, also related to expansion.
When I make a turnout, or crossing, I have to cut insulating gaps to prevent short circuits. These gaps I fill with small pieces of the clear plastic that everything comes packaged in these days. (clear plastic blends in with the silver top of the rail best) I fasten the plastic insulator in place with super glue. When the glue has cured, I file the plastic to the shape of the rail. This same technique can, (and, in my opinion, should) be used whenever you cut a gap in a rail to insulate the two rail ends from each other. This would apply to gaps between blocks for DC, or signal detection, or power districts for DCC. Also such things as reverse loops, and wyes.
Rail expansion could potentially close an insulating gap. This would cause a short circuit that would be particularly nasty to hunt down, leading to some hair pulling frustration! 
Other gaps, contained within non-soldered metal rail joiners, would be left unfilled; to allow for expansion without deforming track gauge. 


Traction Fan:smilie_daumenpos:


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## Alouette (Feb 14, 2017)

I am returning to model railroading after 50 years so forgive me for asking what may be a newbie question. Also, please understand that my skill level at the moment is very close to zero.

I am building a DC HO layout (using Atlas code 83 track). I will have four blocks in this layout, including one reversing or crossover block.

I am using Atlas plastic rail joiners between the blocks. Based on what I have read, other than on the crossover block which must be fully insulated, all of my other three blocks should share a common rail with the plastic rail joiner only used on the rail on the side opposite the common rail.

My problem arises from the fact that since I am not proficient in cutting track, the presence of the plastic rail joiner on only one rail creates a rather large gap on the other side. I can’t seem to find a conducting joiner offered for sale that matches the spacing on the plastic rail joiner.

What is the preferred solution to this problem?

(a) Learn how to cut track
(b) Use plastic rail joiners on both rails (and wire the common rail from the same source separately in each block)
(c) Don’t worry about the gap
(d) Something else

While I have no plans at present to run a DCC system, what would the preferred answer be if I wanted to make converting to DCC in the future as easy as possible?

Thanks in advance for your accumulated experience on this subject.


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## DonR (Oct 18, 2012)

As mentioned in an earlier post in this thread,
I cut an appropriate size sliver off of a scrap rail,
file off the bottom flanges, then use a long nose to
push it into the joiner. A small dab of glue or
solder will hold it in place. 

Don


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## D&J Railroad (Oct 4, 2013)

Alouette said:


> I am returning to model railroading after 50 years so forgive me for asking what may be a newbie question. Also, please understand that my skill level at the moment is very close to zero.
> 
> I am building a DC HO layout (using Atlas code 83 track). I will have four blocks in this layout, including one reversing or crossover block.
> 
> ...


Just cut off a little from the longer rail and it will be fine. The main thing is to get both rails into the rail joiner.


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## CTValleyRR (Jul 26, 2014)

Alouette said:


> I am returning to model railroading after 50 years so forgive me for asking what may be a newbie question. Also, please understand that my skill level at the moment is very close to zero.
> 
> I am building a DC HO layout (using Atlas code 83 track). I will have four blocks in this layout, including one reversing or crossover block.
> 
> ...


My question would be: how big a layout are you planning and what is the purpose of your blocks? I can't think of a reason why each block doesn't need to be totally isolated. You need to preserve the polarity of your connections (so the right rail is always connected to the right rail, except in the reversing loop), but a commin rail defeats the purpose of using blocks.

That said, if your reason for using blocks is to operate multiple trains at once, then I'd recommend you take another look at DCC. It greatly simplifies the wiring, and really isn't that complex to use.

That said, I would strongly recommend you pursue solution a (learning to cut track) if you intend to remain with the hobby.


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## Alouette (Feb 14, 2017)

CTValleyRR said:


> My question would be: how big a layout are you planning and what is the purpose of your blocks? I can't think of a reason why each block doesn't need to be totally isolated. You need to preserve the polarity of your connections (so the right rail is always connected to the right rail, except in the reversing loop), but a commin rail defeats the purpose of using blocks.
> 
> That said, if your reason for using blocks is to operate multiple trains at once, then I'd recommend you take another look at DCC. It greatly simplifies the wiring, and really isn't that complex to use.
> 
> That said, I would strongly recommend you pursue solution a (learning to cut track) if you intend to remain with the hobby.


Thanks. I appreciate all of the comments and the message I am getting is that I need to learn to cut track _regardless of how I solve my block problem_. I will order a track cutter from the online vendor I have been using and attempt to hone my skill. (Part of the reason for my question was what I now think was the mistaken assumption that I could get away without cutting track-- something I was seduced into believing by doing my design using Atlas' "Track Planning Software" and only using standard track lengths.)

In a way I am more interested by your earlier comment in which you stated: "I can't think of a reason why each block doesn't need to be totally isolated." That has sort of been the direction I have been taking (nothing is glued down yet) since using pairs of plastic rail joiners avoids the gap. In order to control my four blocks, including my crossover block, I have ordered both the Atlas 215 Selector and the Atlas 220 Controller. In particular, I was following what I thought was the example in the 220 Controller schematic which (if I understood it correctly) appeared to recommend that the common rail be shared among those blocks other than the crossover block:

http://www.atlasrr.com/pdf/Item220Instructions.pdf

That said, it seems to me like it shouldn't make a difference if my three non-crossover blocks were fully isolated from one another assuming the "common rail" in each block gets its power from the same source. Does that sound right to you? (Note while I have an old Atlas power pack for troubleshooting, I won't actually be hooking up the power for real for quite a while. But I want to lay the track now in the way that makes the most sense.)


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## Shdwdrgn (Dec 23, 2014)

Look for a "jeweler's saw". You can find them in hobby shops for under $20, or about half that on ebay. The one I got also came with sets of different saw blades. These are similar to using a coping saw on woodwork -- you may have to remove and reattach the blade to get inside some pieces of track work, but you can cut an incredibly fine slot through a single or multiple rails (I've been using mine to gap hand-laid turnouts).

Don't worry about a small gap between rails. As mentioned above, a small gap won't hurt anything, and if you have metal wheels on your cars the gap will create a nice clicking sound like you hear on the real railroads.

Regarding your blocks... On a DC system, you may want to completely isolate different loops on your layout. Consider if you were running two trains in opposite directions, then having a shared common rail would actually short out between the loops. If you have a yard you may want to also fully insulate that so you could run a switcher independent from your main lines. Besides the reverse-loops, full isolation is used to keep each locomotive attached to its own power pack, so you have to keep that in mind when figuring out where to place your blocks. You can even run two trains on the same track, which requires full insulation of all your blocks, but this also requires a LOT of manual switching to keep each power pack attached to the right train.


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## Alouette (Feb 14, 2017)

Shdwdrgn said:


> Regarding your blocks... On a DC system, you may want to completely isolate different loops on your layout. Consider if you were running two trains in opposite directions, then having a shared common rail would actually short out between the loops. If you have a yard you may want to also fully insulate that so you could run a switcher independent from your main lines. Besides the reverse-loops, full isolation is used to keep each locomotive attached to its own power pack, so you have to keep that in mind when figuring out where to place your blocks. You can even run two trains on the same track, which requires full insulation of all your blocks, but this also requires a LOT of manual switching to keep each power pack attached to the right train.


Thanks for your suggestion regarding the jeweler's saw. 

Much more importantly I think-- given that I am doing a DC layout and that I have the appetite for wiring (which I used to know how to do quite well)-- you have hit the nail on the head when you mention my desire to run two trains in opposite directions (outside the crossover / reversal block). In fact, that is exactly what I want to do. (I have two basic loops-- one inside the other-- which I designed for exactly that purpose.)

So here's what I think you're saying (PLEASE correct me if I am wrong): If I want the ability to run trains in different directions on different (non-reversal) blocks, I have to:

(a) Fully isolate each block; and
(b) Use DPDT switches to switch the power pack source feeding the block.

_It now appears to me that in order to do that, I can't use the Atlas 215 Selector since that appears to rely on a series of SPDT switches which will allow two power packs to control different blocks but won't allow two trains in two blocks to run in different directions._

*Have I got that right? *(If not, please be patient.)

Here's the link, again, to the basic wiring diagram for the 220 Controller and the 215 Selector that I have been referring to:

http://www.atlasrr.com/pdf/Item220Instructions.pdf


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## DonR (Oct 18, 2012)

I agree with shdwdrgn about using insulated joiners
in both rails for your DC blocks and your two mainlines.

You have complete control of your block polarity that
way. You would have no problem running a train on
Main 1 clockwise, and a train on Main 2 counterclockwise.

Use the inexpensive DPDT switches from Radio Shack
to transfer power from the two power packs to each block.

Don


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## CTValleyRR (Jul 26, 2014)

DonR said:


> I agree with shdwdrgn about using insulated joiners
> in both rails for your DC blocks and your two mainlines.
> 
> You have complete control of your block polarity that
> ...


Yup. That's where I was going with the "purpose of the blocks" question.


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## traction fan (Oct 5, 2014)

*Common rail*



Alouette said:


> Thanks for your suggestion regarding the jeweler's saw.
> 
> Much more importantly I think-- given that I am doing a DC layout and that I have the appetite for wiring (which I used to know how to do quite well)-- you have hit the nail on the head when you mention my desire to run two trains in opposite directions (outside the crossover / reversal block). In fact, that is exactly what I want to do. (I have two basic loops-- one inside the other-- which I designed for exactly that purpose.)
> 
> ...


Alouette;

I am going to disagree in theory, but agree in practical terms, with some of the advice you have been given. Common rail is an old, established, and workable system for wiring a DC layout. There is a good explanation of how to wire it, and how it works, without causing short circuits, In an old book called "Electrical Handbook for Model Railroads" by Paul Mallery. The book is long out of print since it was first published in 1955! I have a second edition published in 1971.
The basic idea of common rail is that one rail has no gaps, except in special situations like crossovers, wyes, and reversing loops. I'm guessing that what you are calling a, "reversal block" is actually a loop where a train runs into the "reversal block" and comes out going the opposite direction, on the same track. Do I have that right? For reference let's say your railroad runs from east to west. That means you would have one "north" rail and one "south" rail. We will leave the north rail unbroken as our "common" rail. That rail, and one "track" terminal on each, of two separate DC power packs, will be wired together and can be electrically grounded for extra safety. The other "Track" terminals of each power pack go to your control panel. There they are connected to the two outer terminals of several SPDT (SINGLE Pole Double Throw) toggle switches. I suspect that your Atlas 215 selector performs the same function, though I have not used one. The center terminal of each toggle switch would be wired to one of your track block's "south" rails. (the ones that do have insulated joiners) You CAN run two trains in opposite directions on your two ovals, or even on the same oval, as long as they're not in the same block.
The main advantage of common rail is that it requires half as many wires from the track blocks to the control panel, and inside the control panel itself. It also means, as you have seen, that you only need half as many rail gaps, or insulated joiners. Sixty odd years ago, common rail was well; more common. On a large layout, with many blocks, this "fewer wires" idea was a big help. It was easier to construct, and easier to troubleshoot any electrical problems. Fast forward to today, and factor in your small, simple, layout; and that advantage no longer amounts to much. 
So you can use common rail, and use your Atlas selectors if you so choose. However the means of controlling trains, and the wiring to do it, have evolved a lot in the last sixty years!
Using DCC on your simple layout would require a whopping total of TWO wires. They would connect your DCC controller to the track. DCC can also make reversing loops automatic, no electric switch flipping required. There is a DCC accessory, called a reverser that does the switching for you. You will still need insulated joiners, in BOTH rails on reversing loops, wyes, and crossovers. This is equally true with any of the three following wiring systems. However, with DCC, those are the only insulated joiners you'll need, on the whole layout!

So you here are your three wiring choices. 

1) You can use the Atlas selectors and common rail, as originally planned.

2) You can insulate both rails at every block boundary, and not use the selectors, but build a small panel with DPDT (DOUBLE Pole Double Throw) switches.

3) Or you can go DCC and eliminate nearly all wiring and insulated joiners altogether.

One other thing. A jeweler's saw is a fine tool. I have one and it does indeed make very thin cuts. In my opinion it would not be a good tool for cutting rail however. The saw's frame would get in the way trying to cut gaps in track fastened to the layout. Also the blades are very fragile, and difficult to change, and then get tensioned enough to work, but not enough to break. (It's a very finicky, and frustrating, adjustment!) Also the very thin gaps cut by this saw could close up from expansion of the rails, unless some insulating material was glued into the gap. I do this when I build turnouts. The tiny gaps I cut to isolate the metal frog are cut with a jeweler's saw blade set in an electric Dremel saw. This is done with the turnout off the layout, obviously. I glue a thin piece of clear plastic in the tiny gap, and the resulting joint is nearly invisible.
Better rail cutting tools are "rail nippers" (a large pair of diagonal cutting pliers), or a Dremel rotary tool. Either will do the job well.

As for filling the gaps in the common rail opposite each plastic rail joiner, don't bother. The gap filled by the center nub on a plastic rail joiner, is tiny. The equivalent gaps, in the common rail, opposite each joiner; are small enough that they will cause no derailments or other mechanical problems. If you notice any tendency of wheels to go crazy at these gaps, try filing the sharp corners of the rail ends into a slightly rounded shape. This should help everything pass through the joint smoothly. As long as the metal joiners are tight, they wont cause any electrical problems either. You can wire around them as you said. It won't do any harm, but is not really necessary. 

regards;

Traction Fan:smilie_daumenpos:


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## mesenteria (Oct 29, 2015)

Traction Fan, I agree that a coping-type jeweler's saw would be ineffective for a turnout already in place and ballasted. However, prior to installation, or when hand-crafting one with rails and PCB ties, those items can be clamped in a vice, the thin filament blade can be loosened from one of the clamps on the saw's frame, inserted though the rails toward the frog (as an example), the loose end reinserted into its clamp, and then you start the sawing action. Tim Warris shows how to do this in his now-ten-year-old how-to videos posted on his site for Fast Tracks handlaid turnouts.

Onto another topic, and this is strictly an expression of my preference, not urging anyone to pay more than passing attention to me:

I dislike the clear plastic insulated joiners. Keeping in mind that I am in DCC and don't really need many gaps, except that the frogs of all turnouts are insulated and dead, I don't like how they look, and I don't have a lot of confidence in their ability to keep their integrity over time, especially on curves. Ballasting pretty much makes this moot because the glued ballast takes over the job of keeping track joints in place and aligned along curves. Soldered joiners on curves really help a lot as well.

I prefer just to leave open gaps. Again, the ballast keeps the rail ends aligned even if those ends are loose with no joiners. The gaps should not be very thin as they would be part of the arsenal of gaps allowing the rails to expand a bit during high temperature swings or when the subroadbed shrinks during dryer seasons and wants to bring the rails tightly together across gaps. For example, I also use Peco Insulfrog Code 83 #6 turnouts in my yard, Those are power-routing turnouts, so on either end of a siding, for example, there will be a short if one of the two Pecos is no lined for that siding....unless I leave a gap at one of them and power the rail between them either via the other turnout's rails or simply feed it with its own feeder. I can leave a slender 1/16" gap that is barely discernible, but it serves its purpose. Yard ballast keeps everything lined up. Or, has for ten years.


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## traction fan (Oct 5, 2014)

*Common rail*



Alouette said:


> Thanks for your suggestion regarding the jeweler's saw.
> 
> Much more importantly I think-- given that I am doing a DC layout and that I have the appetite for wiring (which I used to know how to do quite well)-- you have hit the nail on the head when you mention my desire to run two trains in opposite directions (outside the crossover / reversal block). In fact, that is exactly what I want to do. (I have two basic loops-- one inside the other-- which I designed for exactly that purpose.)
> 
> ...


Alouette;

I am going to disagree in theory, but agree in practical terms, with some of the advice you have been given. Common rail is an old, established, and workable system for wiring a DC layout. There is a good explanation of how to wire it and how it works, without causing short circuits, In an old book called "Electrical Handbook for Model Railroads" by Paul Mallery. The book is long out of print since it was first published in 1955! I have a second edition published in 1971.
The basic idea of common rail is that one rail has no gaps, except in special situations like crossovers, wyes, and reversing loops. I'm guessing that what you are calling a, "reversal block" is actually a loop where a train runs into and out of the "reversal block" and comes out going the opposite direction. For reference let's say your railroad runs from east to west. That means you would have one "north" rail and one "south" rail. We will leave the north rail unbroken as our "common" rail. That rail, and one "track" terminal on each of two separate DC power packs will be wired together and can be electrically grounded for extra safety. The other "Track" terminals of each power pack go to your control panel. There they are connected to the two outer terminals of several SPDT (SINGLE Pole Double Throw) toggle switches. I suspect that your Atlas 215 selector performs the same function, though I have not used one. The center terminal of each toggle switch would be wired to one of your track block's "south" rails. (the ones that do have insulated joiners) You CAN run two trains in opposite directions on your two ovals, or even on the same oval, as long as they're not in the same block.
The main advantage of common rail is that it requires half as many wires from the track blocks to the control panel, and inside the control panel itself. It also means, as you have seen, that you only need half as many rail gaps, or insulated joiners. Sixty odd years ago, when common rail was, well more common. On a large layout, with many blocks, this "fewer wires" idea was a big help. It was easier to construct, and easier to troubleshoot any electrical problems. Fast forward to today, and factor in your small, simple, layout; and that advantage no longer amounts to much. 
So you can use common rail, and use your Atlas selectors if you so choose. However the means of controlling trains, and the wiring to do it, have evolved a lot in the last sixty years!
Using DCC on your simple layout would require a whopping total of TWO wires. They would connect your DCC controller to the track. DCC can also make reversing loops automatic, no electric switch flipping required. There is a DCC accessory, called a reverser that does the switching for you. You will still need insulated joiners, in BOTH rails on reversing loops, wyes, and crossovers; with any of the three wiring systems. However, with DCC, those are the only insulated joiners you'll need, on the whole layout!
So you here are your three wiring choices. 
1) You can use the Atlas selectors and common rail, as originally planned. 
2) You can insulate both rails at every block boundary and not use the selectors, but build a small panel with DPDT (DOUBLE Pole Double Throw) switches.
3) Or you can go DCC and eliminate nearly all wiring and insulated joiners altogether.

One other thing. A jeweler's saw is a fine tool. I have one and it does indeed make very thin cuts. In my opinion it would not be a good tool for cutting rail however. The saw's frame would get in the way trying to cut gaps in track fastened to the layout. Also the blades are very fragile, and difficult to change, get tensioned enough to work, but not enough to break. (It's a very finicky, and frustrating, adjustment!) Also the very thin gaps cut by this saw could close up from expansion of the rails, unless some insulating material was glued into the gap. I do this when I build turnouts. The tiny gaps I cut to isolate the metal frog are cut with a jeweler's saw blade set in an electric Dremel saw. This is done with the turnout off the layout. I glue a thin piece of clear plastic in the tiny gap and the resulting joint is nearly invisible.
Better rail cutting tools are "rail nippers" a large pair of diagonal cutting pliers, or a Dremel rotary tool. Either will do the job well.

regards;

Traction Fan:smilie_daumenpos:


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## Cycleops (Dec 6, 2014)

I thought everyone used one of those secateur type cclippers now. You just need to remove the slight burrs with a fine fine. I find mine very easy and convenient to use.

Many like the click clack of rail gaps.

Just reminded how complicated DC wiring can be.


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## Shdwdrgn (Dec 23, 2014)

Power pack technology has changed a lot since I did model trains in the 70's. Back then every power pack started with an AC transformer, which electrically isolates both leads on the DC side, so if you used the single-wire solutions (and now that it has been mentioned, I believe I used that too, back in the day) the DC power leads from each power pack were completely isolated from each other with no chance for a short due to reverse polarity with respect to each other.

Today, however... We have electronic circuits that change the voltage with methods like the common DC-DC buck converter. The thing about these is that they all seem to force a common ground. Now your power pack could still employ a standard transformer for the initial voltage change, in which case common-rail wiring would still be feasible. I don't know if any manufacturers actually produce a power pack where this could be a problem, but since most people are going to DCC these days I think the possibility should be kept in mind, especially in cheaper train sets.


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## Alouette (Feb 14, 2017)

traction fan said:


> I'm guessing that what you are calling a, "reversal block" is actually a loop where a train runs into and out of the "reversal block" and comes out going the opposite direction.


I am sitting in a hospital waiting room now waiting for my mother-in-law to come out of surgery so I can't-- at the moment-- do the necessary justice to your incredibly detailed and helpful response. The one comment I want to make is in response to the nature of my "reversal/crossover" track (a term I have clearly been using too loosely). It is not a loop. To simplify, two of my regular blocks are concentric circles. I have a track from the outer loop-- a crossover track-- that reverses the direction of travel and reconnects (after going through a switch) with BOTH the inner AND the outer loop (in the opposite direction of travel). 

In a DCC context (yes, I am starting to smell the coffee), I assume that only the three points where the crossover block connects with the regular block would be fully insulated and that no other insulation would be required. Is that right?

Also, since you assumed (because of my oversimplification) that I had a reversing loop, would any of your prior comments-- assuming I continue with a DC implementation-- be any different now that I have described my crossover track to you?


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## DonR (Oct 18, 2012)

I noticed that you had mentioned a crossover situation
but without your actual track plan I had no idea whether
you mean an ability to turn a train around and go the
opposite direction on the same track.

Are you saying that you have, in simple terms, a
simple oval, running E and W for example, and that
you have a track that connects the N and S sides
to enable the reversal?

This can be a tricky wiring situation.

Can you provide a drawing of your actual layout.

By the way, Azatrax has an automatic reverse loop
controller that works on DC layouts.

http://www.azatrax.com/model-railroad-reverse-loop.html

Don


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## traction fan (Oct 5, 2014)

Alouette said:


> I am sitting in a hospital waiting room now waiting for my mother-in-law to come out of surgery so I can't-- at the moment-- do the necessary justice to your incredibly detailed and helpful response. The one comment I want to make is in response to the nature of my "reversal/crossover" track (a term I have clearly been using too loosely). It is not a loop. To simplify, two of my regular blocks are concentric circles. I have a track from the outer loop-- a crossover track-- that reverses the direction of travel and reconnects (after going through a switch) with BOTH the inner AND the outer loop (in the opposite direction of travel).
> 
> In a DCC context (yes, I am starting to smell the coffee), I assume that only the three points where the crossover block connects with the regular block would be fully insulated and that no other insulation would be required. Is that right?
> 
> Also, since you assumed (because of my oversimplification) that I had a reversing loop, would any of your prior comments-- assuming I continue with a DC implementation-- be any different now that I have described my crossover track to you?


Allouette;

OK no loop. But I think that I'd need to see a track diagram to understand your particular situation. It sounds to me,offhand, like you have two concentric ovals with a simple crossover between them. This would not constitute a reverse loop at all. The only thing needed to get a train through the crossover would be to set the direction switches on both power packs the same way. If that's not what you have, then I need a diagram to be of any further help to you. 
As for the common rail info I gave you, that would all remain true, unless, as suggested, there is something different about the power packs innards that would cause a problem. One thing that does not work with common rail is the "Dual power pack". This had one transformer feeding two speed control knobs, all mounted in one metal case. As said, the two packs have to be completely separate. Two single speed knob affairs, each in its own case. Since I'm not familiar with modern power packs,( I use DCC) I can't agree, or disagree, intelligently, with the notion that they might short. If you are determined to go DC with common rail, I suggest trying out your two packs on a short test track set up with a common rail. If it works you're "Good To Go" if not, the circuit breakers or other overload protection in the packs should prevent any damage.

good luck;

Traction Fan:smilie_daumenpos:


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## Alouette (Feb 14, 2017)

DonR said:


> I noticed that you had mentioned a crossover situation
> but without your actual track plan I had no idea whether
> you mean an ability to turn a train around and go the
> opposite direction on the same track.
> ...


Don,

Here's the plan from my home computer. (I had to tunnel in to get it.) I misspoke slightly before: my crossover track goes (starting at the top) from my outer loop and runs to my inner loop.

Each of the two outer loops is assumed to be a separate block. The third standard block would be the track going from the top and connecting to each of the two loops in the bottom (but with no change in direction).

Hope this helps. Once again, many thanks to you and your colleagues here for your time and experience.


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## Alouette (Feb 14, 2017)

*Sub-question regarding common rail on DC layout*

I need a clarification of something very basic.

Assume that my model railroad consists only of the two outer loop tracks in my layout shown above; each loop is a separate block. (In this simplified case, there is no reversal or crossover track.) Just two loops in two DC blocks that are connected as shown with turnouts illustrated at the bottom of my diagram above.

Assume that the outer rail on each loop is the common rail and that plastic rail joiners are used to isolate the inner rail on each transition from outer loop to inner loop (and vice versa).

It is my understanding that in order to reverse the direction of an engine, you need to switch the polarity of the two rails on which the train is traveling.

If this is correct, then how do I use two power packs to control two engines on my two loops where the engines are traveling in opposite directions assuming I have a common rail? Wouldn't I be feeding positive current into the common rail from one power pack and negative current into the same common rail from the second power pack?

(Even if this question reveals my ignorance, I hope my confusion is understandable.)


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## traction fan (Oct 5, 2014)

*How common rail works*



Alouette said:


> I need a clarification of something very basic.
> 
> Assume that my model railroad consists only of the two outer loop tracks in my layout shown above; each loop is a separate block. (In this simplified case, there is no reversal or crossover track.) Just two loops in two DC blocks that are connected as shown with turnouts illustrated at the bottom of my diagram above.
> 
> ...


Alouette;

Yes, you are correct about reversing the train's direction. It is dependent on the polarity of the DC voltage on the rails. 
But--- No. You would not be putting positive, or negative voltage into the common rail. The common rail is grounded. Either literally by being attached to the green wire in a three prong household electric plug; or virtually, by just being a common electrical point. What you actually do with your direction switch, is put either a positive (above the zero voltage of the common rail) or a negative (below the zero voltage of the common rail) onto the block rails (the non-common ones with the insulated joiners. The common rail is always at zero volts. The train changes direction, (and speed, for that matter) because of the voltage being fed to the non-common rails and the difference between that voltage level and the constant zero voltage on the common rail.
Now that I've thoroughly confused you I'll slip in some comments on your track plan. Please note that the following are suggestions, not commandments. What you do on your railroad is your choice. 
Your plan looks awfully busy. By that I mean there is track everywhere. If you plan to add scenery, that's going to be quite a challenge, since there's nowhere to put it. If you want to have structures, or roads, the same problem will come up. I know you said one purpose of building a layout was as a learning exercise,and that's fine, but many of us, and possibly you, look forward to being able to operate our railroads like a real one someday. The track plan you have does not lend itself to that long term goal. However, I don't know if you are even considering that, or not. It, like everything else about your railroad, is something for you alone to decide. 
:dunno:I'm not sure why you seem to be sticking with DC and common rail, except possibly as a learning exercise in how things were done way back when. It will serve as good training in electricity and wiring; and it will make you appreciate DCC even more, should you ever switch to that system.

Good luck with whatever you decide to build;

Traction Fan:smilie_daumenpos:


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## traction fan (Oct 5, 2014)

*My "aha moment"*



Alouette said:


> Don,
> 
> Here's the plan from my home computer. (I had to tunnel in to get it.) I misspoke slightly before: my crossover track goes (starting at the top) from my outer loop and runs to my inner loop.
> 
> ...


 Alouette;

Thanks for the diagram. Now I finally see what you mean by "your crossover track". It's actually a simple crossover like the two at the bottom right of your plan. It simply has more track between the two turnouts. Electrically, it should be treated as just another crossover, meaning insulate both rail joints. You could do that anywhere along the length of the "crossover track."

regards;

Traction Fan:smilie_daumenpos:


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## Alouette (Feb 14, 2017)

traction fan said:


> Alouette;
> 
> Yes, you are correct about reversing the train's direction. It is dependent on the polarity of the DC voltage on the rails.
> But--- No. You would not be putting positive, or negative voltage into the common rail. The common rail is grounded. Either literally by being attached to the green wire in a three prong household electric plug; or virtually, by just being a common electrical point. What you actually do with your direction switch, is put either a positive (above the zero voltage of the common rail) or a negative (below the zero voltage of the common rail) onto the block rails (the non-common ones with the insulated joiners. The common rail is always at zero volts. The train changes direction, (and speed, for that matter) because of the voltage being fed to the non-common rails and the difference between that voltage level and the constant zero voltage on the common rail.
> Traction Fan:smilie_daumenpos:


If I am understanding you correctly: My description of the two polarities on the two blocks is accurate but it doesn't matter. If so, I have just learned something very useful. FWIW, I've done a fair amount of wiring in the last 20 years, but it's all been 110 or 220 AC-- very different rules for grounding in that environment. That said, 45 to 50 years ago when I did lots of DC wiring I never had a situation with two isolated DC power sources which is what is present with two power packs. (I feel bad for having effectively hijacked a thread on the subject of rail gaps over something that ultimately comes down to my ignorance about how to handle multiple DC power sources.)



traction fan said:


> Now that I've thoroughly confused you I'll slip in some comments on your track plan. Please note that the following are suggestions, not commandments. What you do on your railroad is your choice.
> Your plan looks awfully busy. By that I mean there is track everywhere. If you plan to add scenery, that's going to be quite a challenge, since there's nowhere to put it. If you want to have structures, or roads, the same problem will come up. I know you said one purpose of building a layout was as a learning exercise,and that's fine, but many of us, and possibly you, look forward to being able to operate our railroads like a real one someday. The track plan you have does not lend itself to that long term goal. However, I don't know if you are even considering that, or not. It, like everything else about your railroad, is something for you alone to decide.


The interests of marital concord required that I limit myself to a layout no larger than 6 1/2 feet by 8 feet. In that context, I really wanted a reversing or crossover track, a bridge where one track crosses over another, two regular loops, and at least one diamond crossing (I ended up with three). This meant, for example, that I decided to use 18 inch radius curve (excepting a couple of pieces of 15 inch radius track on my yard approaches) even though that means-- as I understand it-- that I won't be able to run engines with three wheeled trucks on my layout. (I also was forced to opt for a 4% grade which appears to be steeper than what folks usually recommend.)

Bottom line: I am not good with delicate stuff generally which was why when I started my thread I expressed my reluctance to cut track. I am far from sure at this point that I'll be successful using the Woodlands Scenic plaster wrap to build the hill over my proposed tunnel and build the two embankments leading up to my 36 inch bridge. If I am successful, then I will undoubtedly start to wonder whether I could handle the construction and installation of buildings as well. But I am trying to keep my goals limited-- what you would probably call modest. That said, my roadbed and everything else will be installed on a one inch foam base which is already in place so if I decide I want to have less track and more scenery, I should be able to make the necessary changes.




traction fan said:


> :dunno:I'm not sure why you seem to be sticking with DC and common rail, except possibly as a learning exercise in how things were done way back when. It will serve as good training in electricity and wiring; and it will make you appreciate DCC even more, should you ever switch to that system.
> 
> Good luck with whatever you decide to build;
> 
> Traction Fan:smilie_daumenpos:


The simplest answer to your question is embarrassing but honest. The catalyst for this whole project was my stumbling a few months back upon a scale model of the very first train I ever took at the age of nine. (It was a self-propelled BUDD RDC mixed baggage and coach car operated by the Boston & Maine and the event had been sufficiently momentous that I never forgot the car number-- the exact car number on the scale model that I found on the web.) That said, as I mentioned in my earlier post, I am starting to smell the coffee of DCC. (And I do understand that in some cases at least DC powered engines can be converted to DCC. Whether this applies to my beloved Budd car or not, I cannot say.) More to the point, since I don't plan to buy my two DC power packs or any engines or rolling stock for several months ($$$), AT LEAST AS I UNDERSTAND IT, I can always wire it for DC now and then just join the block wires for all but the crossover block at my control panel and substitute a single DCC power source. (If I am wrong on this last point, please flag me.) For the moment, I am just using an old Atlas DC power pack for trouble shooting to make sure my connections are all good and that my engine can climb my grade, etc.


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## DonR (Oct 18, 2012)

Using an old Atlas power pack to test your layout
is the perfect answer. You should be able to run
your loco around with no problem. If you see stalls or
pauses, you might have to improve the track joiners,
or if old track, make sure it's rails are clean. You are
aware, that the crossing from lower right to upper
left won't work without special switches and wiring.

You should be able to upgrade your DC Budd commuter car 
with the addition of a $20.00 or so DCC decoder. They
are hardly larger than a postage stamp so there should
be a way to fit it in. The manual that comes with the
decoder will guide where you connect the wires.
There are a couple of tips but we'll save those for
when you start that project.

Don


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## Alouette (Feb 14, 2017)

DonR said:


> You are aware, that the crossing from lower right to upper left won't work without special switches and wiring.


Yes, that's what I've been calling my "crossover" block and I am assuming-- regardless of whether I end up with DC or DCC-- it will be double insulated at both the start and finish with a separate two wire feed from either the Atlas 220 controller or a DCC power pack. (The dead end 270 degree loop track-- see diagram above-- will be part of this block but I am planning to wire it under DC so that I can manually turn off the power to one rail in this section of the block so it can be used to park trains while allowing me to use the through track on the "crossover" block to run trains. In a DCC situation, I am guessing I could just leave this separate SPST switch for this parking track in the on position and pretend it didn't exist.)

THANKS!


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## traction fan (Oct 5, 2014)

*Don't worry, be happy!*



Alouette said:


> If I am understanding you correctly: My description of the two polarities on the two blocks is accurate but it doesn't matter. If so, I have just learned something very useful. FWIW, I've done a fair amount of wiring in the last 20 years, but it's all been 110 or 220 AC-- very different rules for grounding in that environment. That said, 45 to 50 years ago when I did lots of DC wiring I never had a situation with two isolated DC power sources which is what is present with two power packs. (I feel bad for having effectively hijacked a thread on the subject of rail gaps over something that ultimately comes down to my ignorance about how to handle multiple DC power sources.)
> 
> 
> 
> ...


Alouette;

Don't worry about "hijacking" your own thread. I'm not sure that's even possible. In any case, as long as you're getting the information you need to build your layout, then we are all doing exactly what the forum is intended to do.

That's really cool that you found a model of the exact same Budd RDC that you rode! What are the odds of that happening?

I hear you regarding "The interests of marital concord" (working my 36th year of marriage.) You are lucky to have a family member who shares your hobby, that's somewhat rare.

I'm not sure we are speaking exactly the same language with regard to DC wiring, polarity, or what matters electrically; but we do seem to at least be getting closer. I will try an analogy which although I know is flawed, may help anyway. 
It sounds like you worked as an electrician, or at least are familiar with house wiring. In a circuit breaker panel there are many separate "hot" wires going to different places in the house. These would be the equivalent of the separate "block feeder wires going to the various non-common rails around your layout.
A panel also contains two buses, neutral and ground. I'm going to choose ground. Here's where my analogy gets a bit shaky. Using the ground bus we have something similar to a common rail; every wire is always at the same (effectively zero) voltage. 
Now individual "hot" wires may have voltage or not (the breaker could be off, or the wire broken) Some hot wires may be powering something (TV, vacuum cleaner, whatever) and others may be idle. 
Now imagine Edison's DC had beaten Tesla's AC as the way houses were powered. If that were true, then we could wire it so that not only could the hot wires be turned on or off; but we would also have the option of putting positive voltage or negative voltage on any hot wire we chose. The ground bus and all the green wires in it would still be common point. (all at zero volts and all connected.) 
That's how common rail works. We make the common rail our solid immovable foundation; electrically speaking. We can dig down below the foundation to build a basement (so we have a big space for our dream layout!) We can also elect to build up above the foundation to build the first and second stories of the house. But the foundation stays steady and constant. It never moves above its original ground level, or below that same ground level. Only the hot wires (block rails) change their voltage level and/or polarity. The ground bus (common rail) stays at zero. 
I understand your approach to scenery and structures. Take all the time, and only the steps that you are comfortable trying. I'm now going to recommend that you go ahead with your layout as shown on your plan. Yes there are plenty of things that could be improved. (ie.All those Atlas snap switches, and the tight curves are likely to cost you a lot of frustration, and money, most of which you'll never recover.) However it will remain a great learning experience. You will learn about DC wiring, common rail, scenery. grades, and possibly the inadequacies of those layouts in the Atlas track plan booklets. But that's all in the future. For now go with what you have, learn all you can, and , most importantly HAVE FUN! In the long run that's all that really matters.

Traction Fan:smilie_daumenpos:


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## DonR (Oct 18, 2012)

Alouette said:


> Yes, that's what I've been calling my "crossover" block and I am assuming-- regardless of whether I end up with DC or DCC-- it will be double insulated at both the start and finish with a separate two wire feed from either the Atlas 220 controller or a DCC power pack. (The dead end 270 degree loop track-- see diagram above-- will be part of this block but I am planning to wire it under DC so that I can manually turn off the power to one rail in this section of the block so it can be used to park trains while allowing me to use the through track on the "crossover" block to run trains. In a DCC situation, I am guessing I could just leave this separate SPST switch for this parking track in the on position and pretend it didn't exist.)
> 
> THANKS!


There are automatic reverse loop controllers available for
both DC and DCC. If you used one your layout would not
need polarity matching switches and you would not have
the annoying need to flip switches to use the isolated
section.

Don


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## Alouette (Feb 14, 2017)

traction fan said:


> I hear you regarding "The interests of marital concord" (working my 36th year of marriage.) You are lucky to have a family member who shares your hobby, that's somewhat rare.


"Tolerates" is probably a better word than "shares". But my wife is nonetheless very supportive of this project so long as the traffic flow in our unfinished basement is relatively unimpeded.



traction fan said:


> Now imagine Edison's DC had beaten Tesla's AC as the way houses were powered. If that were true, then we could wire it so that not only could the hot wires be turned on or off; but _we would also have the option of putting positive voltage or negative voltage on any hot wire we chose_. The ground bus and all the green wires in it would still be common point. (all at zero volts and all connected.)


I am no electrician (although I admire those who are) but* your paragraph quoted above explains what I didn't understand before but now understand perfectly*.



traction fan said:


> Yes there are plenty of things that could be improved. (ie.All those Atlas snap switches, and the tight curves are likely to cost you a lot of frustration, and money, most of which you'll never recover.) However it will remain a great learning experience. You will learn about DC wiring, common rail, scenery. grades, and possibly the inadequacies of those layouts in the Atlas track plan booklets. But that's all in the future. For now go with what you have, learn all you can, and , most importantly HAVE FUN! In the long run that's all that really matters.
> 
> Traction Fan:smilie_daumenpos:


I actually spent a couple of weeks doing plans using 24 and 22 inch radius track but I could only achieve a fraction of what I wanted on an 8 x 6 1/2 foot table top. So I made the decision to restrict my self to 18 inch radius track. My modeling goal (in terms of rolling stock) is late 50's early 60's post-steam New England (which fits in perfectly with my B&M Budd RDC). So no double stacks, no high cube box cars etc. Whether the 18 inch radius track will fail me assuming locomotives with two axle trucks and freight equipment from this era will be a lesson I will learn over time. How much money I put into this will depend on how successful I am at each stage in the process. I've put about $1,000 in so far (and for the next two or three months at least it's all about sweat equity, not more money) and I figure if everything goes really well, I'll put in another $4,000 over the next four years. 

I've attached a picture of my raw board before I put on my one inch foam overlay (along with a border to protect the foam from being crushed and to provide a 1/2 inch lip above the foam to minimize derailments ending up on the floor) or before I laid out the track (without roadbed or glue) for my two outer loops or started the process of installing my inclines and bridge sections. The AC wiring (including the overhead lighting) was a snap. The board to hold my power pack(s) and switches will be to the left of the electric plug underneath the table.


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## traction fan (Oct 5, 2014)

*Go for it!*



Alouette said:


> "Tolerates" is probably a better word than "shares". But my wife is nonetheless very supportive of this project so long as the traffic flow in our unfinished basement is relatively unimpeded.
> 
> 
> 
> ...


Alouette;

Glad I could help you with the wiring/common rail business. You should be able to operate the small equipment you mentioned on 18" radius curves without problems. I model in N-scale, so for me an 18" curve is a broad generous one that will handle even the largest N-scale equipment with ease, and look good doing it.
Your table looks good, and very sturdy, You are off to a good start. It also sounds to me like you have thought this out quite a lot and have a definite plan in mind. Good for you! Unless you have further questions, I'm going to leave you alone and let you do your thing. I sometimes try to take new modelers too far, too fast, forgetting that we all had to go through a "teething" period before we started to have much idea of what we were doing. Good luck with your layout and keep us posted on your progress!


Traction Fan:smilie_daumenpos:

Photos of my layout


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## Alouette (Feb 14, 2017)

traction fan said:


> Photos of my layout


Maybe I'll be somewhere close by year four if I'm really, really lucky.

Thanks!


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## 89Suburban (Jan 4, 2017)

traction fan said:


> Alouette;
> 
> 
> 
> ...


I LOVE that boat!!!


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