# Gapping rails to make blocks?



## MatroxD (Jan 19, 2018)

Just wondering, and this may be extremely rudimentary, but do you need to gap both rails, or a single rail? Just thought of this when reading another topic and idon't want to derail his thread.. Thank you in advance...

I would like to begin messing with signaling and this is the first obstacle from what I've observed so far...

Thanks again..

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## gregc (Apr 25, 2015)

generally, only one rail (and the same rail) needs to be gapped unless the polarity on the rails change (a reversing section)

you can experiment (to convince yourself) by temporarily removing a rail joiner.


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## MatroxD (Jan 19, 2018)

gregc said:


> generally, only one rail (and the same rail) needs to be gapped unless the polarity on the rails change (a reversing section)
> 
> 
> 
> you can experiment (to convince yourself) by temporarily removing a rail joiner.


Ah! Awesome! Thanks Greg! That's all ineeded to hear! And lol, honestly, I'm better with a dremel, so iit might, as strange as it sounds, be easier for "me" to cut arail in a few spots to create a couple blocks.. Awesomeness! Thank you again tremendously! 

Oh, and ineed to glue and then file some styrene in the gap correct? Just double checking.. 

Im trying to do some experimentation before we have to move, so, all of my fears, for things I'd like to do, Ican lay the groundwork correctly at the new place.. 

Thanks much again! 

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## gregc (Apr 25, 2015)

MatroxD said:


> Oh, and ineed to glue and then file some styrene in the gap correct?


not always necessary. expansion more likely on very long runs. leaving some gap at joiners can allow for expansion so that electrical gaps don't close completely. plastic ties may also help hold rails in place.


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## MatroxD (Jan 19, 2018)

gregc said:


> not always necessary. expansion more likely on very long runs. leaving some gap at joiners can allow for expansion so that electrical gaps don't close completely. plastic ties may also help hold rails in place.


Cool! Thanks a million! Ihave some sanding to do around the house(honey do list), but that actually sounds extremely easy.. I, like you mentioned, may start with maybe 2 gaps to see how it goes for aweek or so, then move on to add another...

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## graywolf06 (Aug 14, 2019)

Been following this thread and understand the gaps but what do you do to then add power to the separate blocks that you created. Can this be done automatically so that the trains just continue past the gaps as if they didn't exist? Right now my layout which is 3 times around is just one power block. It probably is 150 feet of track if strung out in a line. How frequently would you place the gaps? Thanks for any reply in advance. Paul


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## MichaelE (Mar 7, 2018)

I don't know if it is still done this way, but in times past there would be a bank of slide switches with a power wire going to each of the blocks from each of the switches. 

The switch bank is wired to track power.

A PITA really and a lot of wire coming from many directions to deal with.


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## graywolf06 (Aug 14, 2019)

Thanks Michael I am running an NCE powercab and would want all the powering of the blocks to run smoothly without me concerned with throwing the proper switch. As it is now if I have 3 trains running at the same time I have all to do to keep tabs of where they are on the layout and prevent crashes.


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## gregc (Apr 25, 2015)

graywolf06 said:


> I am running an NCE powercab


you may not need gaps.

gaps are needed on DC layouts to create blocks to control multiple locomotives, or fro reversing sections where rails of opposite polarity meet and must be reversed

gaps on DCC layouts are also required for reversing sections and are used to create detection blocks.


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## MatroxD (Jan 19, 2018)

Actually, and If i can find the video, i link it. If my yard is any indicator, there's not much needed to be done as far power is concerned. That is, as long as you have multiple track drops(locations) built into your bus. Basically, if you don't believe in the "only 2 wires for power are needed for a complete layout" philosophy, it's easy. 

I already have a very good idea of where to make my cuts on the main. I know that simply because, on my even simply small layout, i ran a drop set if wires to every quadrant of the oval/ dog bone like track side. I also, too the spurs(except one), ran a drop. My yard has one drop, and already has a gap in one of the rails, so I'm good there. 


I will then, add additional EB1 breakers for every block. Right now, i have a single breaker/EB1running the whole layout. This actually is a pain because if say, the N loop shorts(is the only one that ever does), the complete layout comes to a halt. Ihave to start and re arm every locomotive(I like lights on). But with blocks, this will not happen, and only the block with the short will go down. The yard is once again a perfect example. I will simply add the EB1in line with the power drop(just cut the drop, screw the wires in, set the jumper for the amp's, and done), and it's done. 

The nice thing about the EB1's is that you can add both led indicator light that flashes when a short and shutdown occurs, and a simple pushbutton switch to reset. So it's as easy as seeing a flashing light, looking on the track for the issue, in my case, putting the annoying N wheels back on, and pushing a button, to start only that locomotive and block. Nothing else on the entire layout will have even noticed. 

That part(adding the breaker) is easy and very convenient, not to mention, adds a safety factor. 

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## MatroxD (Jan 19, 2018)

MichaelE said:


> I don't know if it is still done this way, but in times past there would be a bank of slide switches with a power wire going to each of the blocks from each of the switches.
> 
> The switch bank is wired to track power.
> 
> A PITA really and a lot of wire coming from many directions to deal with.


Nooo.. lol.. electronic now dude, with visuals indicating the block short.. 

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## MatroxD (Jan 19, 2018)

Here is a to the video. He didn't have the external light and reset button installed on a fascia. 








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## gregc (Apr 25, 2015)

if you're creating blocks for circuit breakers, you need both rails gapped.


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## MatroxD (Jan 19, 2018)

gregc said:


> if you're creating blocks for circuit breakers, you need both rails gapped.


Ah... I figured there'd be a catch somewhere.. oh well..

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

Most of your block detection boards can only work with a set determined number of blocks. If you railroad doesn't exceed that number of blocks you're ok. When you need to introduce a second block detector board, you will need to cut both rails so the common rail of each block detection board will remain common but unique to that one board.


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## gregc (Apr 25, 2015)

D&J Railroad said:


> When you need to introduce a second block detector board, you will need to cut both rails so the common rail of each block detection board will remain common but unique to that one board.


not true, at least for the NMRA circuits that uses a diode bridge, or the transformer type, bd20. The detector goes in series between the power source and the rail. That circuit is either optically or magnetically coupled to the output circuit and each of the other detection circuits. 

i just wired up 5 staging track through 5 separate detector boards all having a common rail within a reversing section.


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## MatroxD (Jan 19, 2018)

gregc said:


> not true, at least for the NMRA circuits that uses a diode bridge, or the transformer type, bd20. The detector goes in series between the power source and the rail. That circuit is either optically or magnetically coupled to the output circuit and each of the other detection circuits.
> 
> 
> 
> i just wired up 5 staging track through 5 separate detector boards all having a common rail within a reversing section.


Hmmmnnn.. So basically, with my nce system, if I were only doing the blocks for detection, such as signaling, only one common rail would need to be cut(such as using the bd20)? But because I would like to incorporate the circuit breakers(ie, the EB1), I will need to cut both rails? 

Am I getting that correctly, simply because I'm gathering it's depending on exactly what you want to do, and what system you user, that determines the steps you must take? 

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## gregc (Apr 25, 2015)

MatroxD said:


> Hmmmnnn.. So basically, with my nce system, if I were only doing the blocks for detection, such as signaling, only one common rail would need to be cut(such as using the bd20)? But because I would like to incorporate the circuit breakers(ie, the EB1), I will need to cut both rails?


gaps should be cut in both rails for power districts (boosters, circuit breakers) and auto-reversing sections. Within those, detection blocks require a gap in one rail (and the same rail) and power to that rail run thru the detector.

in the staging loops i'm working on there are 5 staging tracks. 3 are in one reversing section and 2 in a 2nd reversing section. At each end, there is a detection block with turnouts that connect the staging tracks to one of 4 mainline tracks within the reversing section. The 4 adjacent mainline blocks are also detected.

if the leads from the booster are labeled A and B, they are connected to the auto-reverser and the outputs from the reverser for one reversing section are X and Y and the 2nd reversing section, V and W. The mainline blocks are connected to A and thru B to the detectors. The detection blocks for the 3 staging tracks are connected to Y and the common rail to X. The detection blocks for the 2 staging tracks connected to W and the common rail to V.

not sure how big a layout you have and how many circuit breakers you plan on having. On the one basement layout i'm helping build, auto-lamps are used on one rail to limit current during a short. the lamp is in series with one of the leads from the booster to a section of the layout. That basement layout has 4 lamps.


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## MatroxD (Jan 19, 2018)

Hmmmnnn. I have read your post a few times, trying to give asensible response. I have been thinking, that maybe I should only do one more "breaker " district, and perhaps focus more on the"detection" districts, in an attempt to negate cutting tons of track. I will have a different attitude and mindset on the next layout build. I can gap during the building process, which will keep the chance of destroying something to the minimum. 

I also caught on a YouTube video, that there signaling "systems", that do everything for you. Maybe, at this point, that is a better option for my smallish layout? It is only afn 8or, with another 2x3 used as my yard. I just don't know of any of the companies that offer the system. Do you by any chance? You or anyone else...

Thanks much..

D



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## gregc (Apr 25, 2015)

it may not be obvious why both rails "should" be gaped between power districts and breaker sections although they may not "need" to be.

breakers and auto-reversers monitor current thru both rails. If excessive current is detected in either rail, they trip.

while a short is likely between both rails, there's the possibility of a short between rails on different tracks powered thru separate breakers or while installing. I had a problem with a short because feeders were wired backwards for one block.

perhaps a simpler way of thinking about it is you want a single booster/breaker to provide power to both rails.


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## MatroxD (Jan 19, 2018)

gregc said:


> it may not be obvious why both rails "should" be gaped between power districts and breaker sections although they may not "need" to be.
> 
> 
> 
> ...


Ooohhh.. That makes sense then.. Cool. I just need to figure out how many breaker blocks im going to do. I probably will just start with one additional, and then go from there.. I don't have any reversing at the moment. Really all I have are dog bone type of ovals atm. 



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