# Reverse loop operation



## Sehender1 (Jan 21, 2015)

So I'm creating a layout with TWO reverse loops in it. 
I have an operations question. I know that with one reverse loop, I'd need to keep from having more than one train in the loop at a time. Two trains, one loop = short circuit, right? 

I'm running DCC, just FYI. 

But with two loops, on opposite ends of the layout, would the same rule apply? Would I need to make sure both loops weren't being operated at the same time? 
Or would it be okay, since the loops will be separately powered by auto reverse modules? 

Here's a crude diagram of the layout I'm asking about.. Could there be, say, one train each in the blue areas, simultaneously, without causing a short?


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## DonR (Oct 18, 2012)

You must have 2 reverse loop controllers, one for each BLUE 
isolated section. You would want each isolated section to
be as long as your longest LIGHTED passenger train but
no longer. That is to try to keep only one train in an
isolated section at a time.

If you tried to control both of the BLUE sections with
one controller you would have difficulties when a train
is in the top loop isolated and another train enters
the isolated section in the bottom loop.

I think you mentioned the Digitrax Ar-1. You would need
two of these. I see them under 25.00 at Micromark.

Don


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## Sehender1 (Jan 21, 2015)

Hey Don. Thanks for the note. 

Actually, my question is a little different. 

I've got the part about the two auto reverse modules. That makes sense. 

But I'm wondering whether both auto reverse sections could be operated at the same time - in other words, could trains be in both simultaneously... 

Thanks!


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## DonR (Oct 18, 2012)

Yes, you could have trains in both isolated sections at the same
time since each would have it's own controller to keep the
tracks in phase. Remember, the controllers will reverse the
isolated section only, so the Main will always stay as wired,
per your red/black drawing.

If there were two trains crossing the insulated joints in either
isolated section at the
same time that would cause a short circuit.

Just a reminder, when the loco spans the insulated joint it
causes a short. The reverse loop controller senses this
and very quickly reverses the isolated section track phase
to match the main. Then it does it again when the loco exits
the isolated section. So if a loco is spanning the entry
insulators and another is spanning the exit insulators at
the same time the controller is unable to match phase
and a short circuit occurs.

Don


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## cv_acr (Oct 28, 2011)

Yes, as long as each reversing section is powered by it's own separate auto-reversing controller, you are fine.

As DonR mentions above, what cannot happen is two trains (or two ends of the same train) crossing the opposite boundaries of the *same* reversing section at the same time. That will cause a short that the system cannot handle.

So your reversing section(s) should be large enough to handle a full train (if you use plastic wheels and do not have lighted cabooses or passenger cars you can go with the longest set of engines you will use) and located so that two trains cannot normally enter from opposite ends at the same time.

Having multiple reversing sections won't affect each other as long as they are separate.


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## RT_Coker (Dec 6, 2012)

cv_acr said:


> Yes, as long as each reversing section is powered by it's own separate auto-reversing controller, you are fine.
> 
> As DonR mentions above, what cannot happen is two trains (or two ends of the same train) crossing the opposite boundaries of the *same* reversing section at the same time. That will cause a short that the system cannot handle.
> 
> ...


I use trains with mettle-wheeled-cars that are longer that my reversing loops. What I had to do was to make the rail-gaps big enough so the mettle-wheels do not short it. Why the gaps do not already come this way is a great mystery to me!
Bob


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## DonR (Oct 18, 2012)

Metal wheels on a long train can be pesky in an isolated section.
This is true especially when the isolated section is in the main
lines as on this layout. But there are easy fixes.

As Bob suggests, a larger gap, or some have used a tiny dab of clear finger
nail polish on the rails on one side of the gap,
or even a plastic filler in the gap, a tiny fraction
higher than the rails to prevent metal wheels from contacting
rails on both sides of the gap at the same time.

Don


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## vikramgoel (Mar 2, 2015)

On advise from Larry of Tonys Train excahange I have found if you stagger the gaps it works best for reversing loops.

Here is the email I received from Larry:

"The first thing to try is to stagger the gaps at the start and end of the reverse loop. Most people tend to try to make them exactly equal. This can result in a short circuit that will cause the engine to hesitate. On one of your loops, try offsetting the insulated gaps by about 0.25 inches (about 6mm). Make sure BOTH rails at EACH end of the loop are completely insulated from the main track...."


Hoep this helps.

Regards,

Vik.


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## DonR (Oct 18, 2012)

I suppose a quarter of an inch offset is not that much of a
haggling point. But, I don't see why it is any better than
equal insulated joiners. The first loco wheel that spans the
staggered joint is going to 'short' and thus trigger the
reverse loop controller to operate. I don't have any blinking
headlights or locos pausing at reverse loop isolated track joints
and my insulated joiners are at even spacing in the track.

Don


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## vikramgoel (Mar 2, 2015)

DonR said:


> I suppose a quarter of an inch offset is not that much of a
> haggling point. But, I don't see why it is any better than
> equal insulated joiners. The first loco wheel that spans the
> staggered joint is going to 'short' and thus trigger the
> ...


Don,

I had an issue with stalling going into and out of the reverse loop, using the method given by Larry fixed the issue, I think it has to do with each wheel gong thru the gap at different times, and it does not short as both wheels going at the same time will short and thus giving reverse loop controller time to switch polarity (I think) 
It did work for me so I am good on this.

Regards,

Vik.


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## DonR (Oct 18, 2012)

Very interesting.

I had not heard of the problem or that solution before.

Will have to keep it in mind for those who are
experiencing shorting on reverse loop joints.

Don


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