# My design



## rva1945 (Feb 11, 2016)

Hi:

I tried to follow as many rules as possible, I must combine my lack of knowledgment and space constrains, and came to this one. There will be a freight and passengers service, 2 trains.

The freight train will be able to access the yard, perform the shunting ops and exit the yard, all without interfering with the main line.

The passengers service will be able to access the "Terminus", move the loco to the rear and be taken back to service into the main line.

There will be no problem with polarity (I hope!).

Is this design sound?

But now I realize that the loco will become reversed!


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## Brakeman Jake (Mar 8, 2009)

Rigt now,you have a polarity conflict at the double tracks leading to your "Terminus".

We could be of more help with more info like:
-adding measurements to your plan
-wich scale?
-plan on running DC or DCC?
-locos and car types you wish to run
-available space in the room,where are doors and windows
-will operate alone?with children?any handicap?
-desired height?

There is no "perfect" layout.However,the most features thought about incorporated in the design from the get go is a much better warranty of long term enjoyment.


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## rva1945 (Feb 11, 2016)

Brakeman Jake said:


> Rigt now,you have a polarity conflict at the double tracks leading to your "Terminus".
> 
> We could be of more help with more info like:
> -adding measurements to your plan
> ...


Hi
I guess the polarity issue is above at the exit from Terminus where it connects again to main.
The L shape is 5 meter long and 2.6 meter wide. The narrow section alone is 2.6 meter x 0.40 meter.
Scale is HO.
Will run on DCC.
Diesel locos, a freight train and a passengers train, each one with its loco.

No problems with doors and windows, no children, no handicap. In fact the baseboard is already installed, as you can see in another post.

Worried about the polarity issue and no idea on how to solve it.

Thanks.


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## rva1945 (Feb 11, 2016)

Brakeman Jake said:


> Rigt now,you have a polarity conflict at the double tracks leading to your "Terminus".
> .


Is that switch (see attachment) that will create the short?


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## wvgca (Jan 21, 2013)

rva1945 said:


> Worried about the polarity issue and no idea on how to solve it.
> Thanks.


the polarity or DCC phase change in the terminus area will require that the section be electrically isolated, and then fed with either a manual DPDT switch or a auto-reverse module .. the lower end of the track may have to be longer to accommodate whatever length of loco and cars that you will have in that area

looks like it should be a nice layout when complete


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## rva1945 (Feb 11, 2016)

Thanks!

I my previous reply I attached a picture where I highlighted the switch that I understand will create the short when activated. Can you please tell me if I am correct or wrong?


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## rva1945 (Feb 11, 2016)

So far you guys know that I am a newbie here. Lots of childish questions by my part.


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## wvgca (Jan 21, 2013)

rva1945 said:


> Thanks!
> 
> I my previous reply I attached a picture where I highlighted the switch that I understand will create the short when activated. Can you please tell me if I am correct or wrong?


that whole area will need to be isolated so that the DCC phase can be changed, with either gaps cut in the track, or the use of plastic insulating track joiners, both rails on either end as shown in the sample pic attached ..the can be done in different spots rather than shown, but I have found that it's easier to do on a straight piece of track


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## rva1945 (Feb 11, 2016)

OK, I need to analyze it further later.

But coming from the main line, in the middle, not above (above is the exit, not the access to Terminus), I see that polarity remains the same, for example, the left rail remains positive, but the problem is in the switch that I highlighted.

But maybe I still don't fully understand how the switches are electrically connected to the tracks. If the problem arises when activating the switch, shouldn't just the moveable rails be insulated?

I didn't even know there were plastic joiners! I hope they will not stall the loco.


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## wvgca (Jan 21, 2013)

rva1945 said:


> I didn't even know there were plastic joiners! I hope they will not stall the loco.


they work the same as metal joiners but don't conduct electricity ..a very small gap [same as metal joiners] .. different colours are usually different stiffness .. as far as I remember the clear are soft, white or yellow are harder, depends on manufacturer
also, they come in different sizes to match the track, Code 100, for example


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## rva1945 (Feb 11, 2016)

The only way to test this safely will be using a DC power source with current limitation. I have one of these, it can produce from 1.5 to 16V and shorting its terminals will not excede 1 amp.

So I will power the layout with that source, and then operate all the switches to see what happens with the voltage. Any drop and it will indicate a short!


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## MtRR75 (Nov 27, 2013)

rva1945 said:


> I didn't even know there were plastic joiners! I hope they will not stall the loco.


No problem there. The plastic rail joiners are attached to track just like metal jointers, except there is a 1mm thick barrier in the center of the joiner that keeps the two rails from touching each other. Locos have multiple pick-up wheels, so when one of the pick-up wheels is momentarily sitting on the plastic joiner, the other pick-up wheels will continue to pick up power from the track.


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## rva1945 (Feb 11, 2016)

I highlighted what is a switch in my design but there is no need for a switch here. I don't know how to name it exactly but I think of a "fixed turnout".


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## Brakeman Jake (Mar 8, 2009)

Since there's no track beyond to allow switching anything,the turnout at the "terminus" end is useless and could simply be removed from the plan.Two parallel tracks to the terminus will serve the purpose just the same and avoid a shorting connection.


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## DonR (Oct 18, 2012)

Wvga

I agree with your suggestion to make the entire 
'terminus track as the isolated section, but there is
a need for a 3rd set of insulated joiners. That is
where the crossover turnout joins another.

RVA

The turnout you have circled is not the problem
and should be left connected. Use the gap or
plastic joiners where WVGA and I have indicated.
I suggest an automatic Reverse loop controller.
It lets you run trains without having to bother
with phase/polarity matching.

Turnouts pass the track current the same as
sections of track. The difference is the Frog where
the current of both rails are near each other.

However, in your case you have a continuous
oval. The polarity mismatch occurs when you
use a crossover to connect both sides of your oval.
You are effectively connecting the left and right
sides of your loop together. 

We encounter this very situation several
times a year. Often the modeller uses a
double crossover.

Don


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## rva1945 (Feb 11, 2016)

Here

http://www.building-your-model-railroad.com/model-railroad-wiring.html

it says "...In order for your engine to get on to the isolated track, the polarity of that isolated track must be the same as the polarity of the mainline track that the engine is coming from. When your train leaves the isolated loop, the mainline polarity has to be changed to match that of the isolated track your train is coming from...."

So when the loco enters the isolated track, this must match the same polarity as the main line the loco is coming from, then before leaving the isolated track, do I have to change the main line polarity?

What will happen to any other loco running in the main line?


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## wvgca (Jan 21, 2013)

rva1945 said:


> So when the loco enters the isolated track, this must match the same polarity as the main line the loco is coming from, then before leaving the isolated track, do I have to change the main line polarity?
> 
> What will happen to any other loco running in the main line?


the polarity or DCC phase that gets changed is only in the isolated area, not the main track itself .. 
an auto reverse module is a better long term solution [for DCC], and is more expensive, for short term testing [or a DC layout],a DPDT switch can be used
The terminus section polalrity must match the portion of the main track that the loco is going to proceed on ..


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## rva1945 (Feb 11, 2016)

So the polarity of the terminus section must change: first, it will match the polarity of the main line the loco comes from, then it has to be reversed in order to match the main line as it will return to it through another access, is that ok?

That can be annoying because the train will stop and even reverse its direction, but in my case, as it must stop at the end, that is a good moment to change (terminus) track polarity.

The switch I left at the end is intended for letting the loco, after uncoupling from the passengers consist, reverse direction and run parallel to the consist to the other end, couple the consist and return to service. Yes the loco will be reversed though its speed will be forward because I switched polarity in that section. Or am I wrong, because it's DCC and the phase will not alter the forward/reverse speed direction?


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## DonR (Oct 18, 2012)

RVA

You are running DCC. Unlike DC, the phase/polarity
of the rails does not affect loco direction or speed. Your
DCC controller sends a digital signal thru the rails to
a decoder in each of your locos. Only that will
be in control. The modified AC track voltage is
stable at around 14 volts. It doesn't go off and
on or vary. It is used to power the loco decoders
and carry the digital information.

A short explanation of a reverse loop controller.

When a loco's wheels span the insulated joiners (or gap)
there is a short circuit. The DCC reverse loop controller
reverses the phase of the isolated section matching
that of the main track. The loco
continues on smoothly, it's lights don't even flicker. 
(the loco does not stop or reverse) Then
when the loco reaches the 2nd set of joiners there is
another 'short' that causes the reverse loop controller
to again reverse the phase of the isolated section, again
matching that of the main line. The phase of the
mainline is unaffected by all of this action and there
no effect on any other locos running on the layout
at the same time.

And by the way, the reverse loop controller is totally
automatic. Once installed and working you never
touch it again. You won't even know it's there.

Don


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## rva1945 (Feb 11, 2016)

So the loco itself creates the short because the front left wheels will pick up a pole and the rear left wheels will pick up the other pole, and the same will happen with the right wheels. As the wheels at the same side are the same electrical connection, there is the short, ok?

Now, in my case, if I make sure that the loop polarity matches the main line before accessing it and after leaving it, everything should be ok.

I will control the switches or points with servos driven by an Arduino. In that case, I can make the switches work in sync in such a way that the access switch will be on while the exit one will be off, and vice-versa. At the same time, matching the corresponding polarities. I must study it later at home but maybe I must make sure that the loco will not reverse back to the main as soon as I changed polarities or the short will be created. But I can prevent that with the correct code running in the Arduino.

There are some detection modules but I don't like those that detect the short, I consider it dangerous for the decoders or the DCC power source. I'll try find a solution without the need for buying a module.

Thanks.


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## Brakeman Jake (Mar 8, 2009)

Simply identify the portion of track that needs polarity reversing,install insulated joiners at both tracks both ends then install a reversing module as per the easy instructions then forget it.It's that easy.And for your worries,these modules have been used for years without known issues.

There's no danger to the decoders as the modules react instantly as soon as the first axle of the loco jumps the gap while at least three other axles of the loco (diesel) are still on the main so that there's no current stoppage to the decoder.When leaving the reversing section,the polarity will change under the loco (wich the decoder ignores) but there still isn't any current interruption while jumping the gap.


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## rva1945 (Feb 11, 2016)

Well, I think here I have the freight ops yard and a passenger ops area with possibility of selecting among 3 locos.

No short, or at least that is what I think, please tell me if I'm wrong.

I'll feel truly happy if I can get rid of the shorting nightmare.

Regards,
R.


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## bluenavigator (Aug 30, 2015)

On that last image, I do not see any short anywhere. So it will be fine. Only that tracks in parallel, they might be too close to each other. NMRA recommendation was 2 1/4" center to center of the tracks, I believe. More width on curved tracks. That is to avoid bumping rolling stocks on different tracks.


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## DonR (Oct 18, 2012)

Clean as a whistle. But, you eliminated the loco run around
track for your passenger train.

Also, with all of that single track main line I sure would
want to add passing sidings. Those will make your
operation of trains more exciting.

Don


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## wvgca (Jan 21, 2013)

I was wondering how you intend to switch the turnouts, the one on the upper right would be a pretty long read for a manual ground throw, easy with throw rod, or electric throw ..


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