# Reverse loops and DC



## Hutch (Dec 19, 2012)

I got my reverse loop working today and immediately notice some things I don't like. 

I have to switch the track and the power direction before leaving the loop causing any other train to stop and reverse also.
I have to switch 2 seperate switches.
I have to make sure all the turnouts are in the proper positions.
I know some of the problems will go away when I switch to DCC but in the mean time.


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## sstlaure (Oct 12, 2010)

You could break up the outer loop into a separate block and run it with a completely separate powerpack (Run A/B cab switches to control which powerpack is running each train.) 

Without block control and DC you're pretty limited as to how your engines can operate.


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## timlange3 (Jan 16, 2013)

With DC you should isolate your 'S' curve reversing section between the turnouts. It should have a polarity changing switch between power and track. So train would go in (with polarity switch set correctly for that entrance) and once completely in the block you would stop the train. Then change the polarity to match the exit. Of course changing polarity to match the exit would change direction on DC, so you would have to change your direction switch before starting.

Not sure what you mean by other trains stopping and reversing, you are controlling multiple trains with one DC controller????

If your turnouts are powered, wire the two in parallel, so they both change at the same time.


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## DonR (Oct 18, 2012)

You have an interesting track layout.

The reverse loop DPDT switch contro, as already suggested, along with
powering your outer loop with a separate pack is the only
way to go to run it on DC.

However, there is one additional potential polarity mismatch...
and that is the Crossover between your outer and inner
loops...if you have the outer loop outer rail Positive (and
the other negative) then the inner loop outer rail must also
be positive when you use the crossover...tricky if you
have a loco running in the inner loop...and more DPDT switches.

Now you see why the extra moolah for DCC is worth it.
All this is handled automatically with a reverse loop
controller.

Don


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## Hutch (Dec 19, 2012)

Just trying to have fun with this until I get my tax return. I planned on DCC from the start but it is expensive. I'll get there.

I've got the loop insulated and I switch it with a cross wired DPDT switch. Now if I could get the controller to switch when I switch polarity, that would be nice. I'm sure there's a way using more switches but I haven't figured that out yet. I haven't seen any shorting inner to outer loop yet so I think I've got that part right. 

I like to keep one train on each loop and watch them pass each other. Nothing else to see yet.


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## DonR (Oct 18, 2012)

Hutch

That crossover potential shorting would occur if you use
a separate power pack for the outer loop...it will be OK
if you are using only the one power pack...

With 2 packs you could have the outer loop outer rail positive
and the inner loop outer rail negative depending on your
train operations. That would not be nice.

Maybe you could get lucky on Craigslist as I did...found a
guy who had a huge collection of cars and the like for sale.
Turns out he had the controller and 2 locos of the
Bachmann DCC Starter set...I got them and a number of
cars for about half what my brother paid for the New DCC
Starter set. I've found a number of values in their posts.

Don


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## Hutch (Dec 19, 2012)

DonR said:


> Hutch
> 
> That crossover potential shorting would occur if you use
> a separate power pack for the outer loop...it will be OK
> ...


I plan on building my DCC system using MERG kits. I'm already a member so the switch to DCC isn't too far off. With that said, I don't want to add to my DC collection out of impatience. I think I'll just get started on scenery and enjoy what I have for now. 

I should get in the habit of watching Craigslist though. 
Thanks to all for your input


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## Southern (Nov 17, 2008)

DonR said:


> Hutch
> With 2 packs you could have the outer loop outer rail positive
> and the inner loop outer rail negative depending on your
> train operations. That would not be nice.


It will not hurt anything. This tyco F7 runs out of one block onto a block from a sceand contoler that is opposit polirity.




 
you do not want to do that. i just wanted to show that it was not going to explode


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## JerryH (Nov 18, 2012)

Love it!:appl:


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## Hutch (Dec 19, 2012)

:laugh: My grandkids might appreciate that.:laugh:



Southern said:


> It will not hurt anything. This tyco F7 runs out of one block onto a block from a sceand contoler that is opposit polirity.
> 
> you do not want to do that. i just wanted to show that it was not going to explode


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## DonR (Oct 18, 2012)

Southern

If you are running a DC loco forward into a block that
is of reverse polarity it should trip your pack breaker but
even if it did not...the loco would back up,
wouldn't it, since it's now seeing reverse polarity. 

If one loco truck is in a block with outer rail +
and other truck is in block with outer rail -...you have
a short in the locos wiring and the 2 power packs won't
think too much of it either.

I had this type crossover with a single power pack but with
blocks capable of reversing polarity on a DC N layout
decades ago...I can't remember any of the
operational problems from it tho...

Don


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## timlange3 (Jan 16, 2013)

DonR, there will not be a short circuit if there are two power packs. The engine will go back and forth until the power to the engine from each truck cancel each other out in the motor windings. Then the motor should just heat up. Probably take minutes before something gets hot enough to make something bad happen.

Doing this with a single power pack will cause a short. Remember, the positive/negative of one power pack have no relation to any other power pack. This is why common ground works.

You can have multiple power packs controlling multiple loops of track, plus another pack for lighting, plus another to control switch machines and so on. Designate one of connectors on each power pack to be 'negative' and connect them all to the same, somewhat heavy wire. Then run one 'hot' wire from the other connector on the power packs to the different locations/things. The more power packs and things to connect the more wire you can save by running all 'negatives' to the same wire. The power packs can be different voltages and ac and dc can be mixed.

I've seen a lot of older railroads wired this way to save wire. They run one 'negative' bus, one 'positive' track bus (or more), one 'positive' lighting bus, and one 'positive' switch machine bus.


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