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Wiring a reverse loop

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Posted by alan76 on Sunday, March 6, 2016 3:56 PM

Scotty

I don't know how to wire a reverse "Y" with an AR1 because the "Y" connects to the Main in two places. In other words, the main is not split at the "Y" but joined to both ends resulting in 3 turnouts....

 

                                                                                                            So.....I'm having a problem hooking up a Digitrax AR-1. I model in HO. The tail of the Y off of the mian is going to be a branch line. I have the gaps as shown in the drawing but closer to the main and the AR-1 hooked up as shown minus the booster. My problem is that the engine can come into and leave the right side of the turning wye just fine but when I try to enter or leave the left side of the wye, the engine stops as soon as the first truck on a diesel or or !st drivers on a steam engine cross the gap. If i push the engine the rest of the way over the gap, it will continue on its merry way.    I called Digitrax and was told that my gap probably wasn't wide or deep enough (I had a styrene shim level with the track height in the gap) to cause it to trigger the change in polarity. I made it deeper and wider but it didn't help.                          I sent them back the AR-1 and they replaced it. The new one still acts the same way. What am I doing wrong? 

Thanks, Alan

OMG.....NEVERMIND.....I figured it out with the adjustment to the potentiometer. I was not turning it enough counter-clockwise. Now all my engines, diesel and steam, both work without a problem. Except for the larger gap that the Digitrax guy told me to make. Since it's on a curve, the pilots on my steam now sometimes derail. So now I have to replace the styrene I took out of the gap. Easy enough. 

 Thanks for letting me vent and rethink my problem, Alan

Tags: AR-1 , auto-reverse , wye
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Posted by floridaflyer on Saturday, February 20, 2016 12:44 PM

If you are going to power the reverse loop from the track buss, the feeders from the buss have to go to the input side of the AR-1 and then from the AR-1 to the track in the reverse loop. You cannot go directly from the track buss to the reverse loop. 

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Posted by TrainsRMe1 on Saturday, February 20, 2016 12:30 PM

I also have a reversal loop, in my track plan,  be it just staging, the question is this, I'm using a AR-1 to reverse the polarity, does my feeders from the track bus powering the loop have to be reversed also?

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Posted by BigDaddy on Saturday, February 20, 2016 12:14 PM

danno54

Speaking of reverse loops, i'm interested in one of the H.O. layouts shown in the layout data base. I like the double mainline and number of stations/terminals.

It's called "Metropolitan Passenger Terminal". I am having a hard time figuring out the wiring reguired for this layout with all the cross overs and reverse loops. Any input would be appreciated.

That's probably worthy of it's own thread; it's a complicated trackplan.  More people will look with the link http://mrr.trains.com/how-to/track-plan-database/2010/11/metropolitan-union-passenger-terminal

Henry

COB Potomac & Northern

Shenandoah Valley

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Posted by danno54 on Saturday, February 20, 2016 8:36 AM

Speaking of reverse loops, i'm interested in one of the H.O. layouts shown in the layout data base. I like the double mainline and number of stations/terminals.

It's called "Metropolitan Passenger Terminal". I am having a hard time figuring out the wiring reguired for this layout with all the cross overs and reverse loops. Any input would be appreciated.

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Posted by MisterBeasley on Wednesday, February 17, 2016 3:45 PM

Who made the turntable?  Some of them have built-in split-ring reversers and need no additional circuitry.

It takes an iron man to play with a toy iron horse. 

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Posted by Steven Otte on Tuesday, February 16, 2016 10:31 AM

Since a turntable by definition reverses polarity when it rotates, either the turntable or ALL the tracks coming off it need to be on a reversing circuit. If you're going to have a bunch of tracks coming off a turntable, it would be simplest to let the turntable be the track controlled by the reverser.

Which would mean a second reverser for this setup, unless you let the turntable do all the locomotive-turning duty, and eliminate the wye.

--
Steven Otte, Model Railroader senior associate editor
sotte@kalmbach.com

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Posted by floridaflyer on Tuesday, February 16, 2016 10:24 AM

Steve, in the situation you describe, would the tracks leading into the roundhouse or parking area be wired to the reverser if the turntable is powered by the DCC buss?  

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Posted by Steven Otte on Tuesday, February 16, 2016 9:56 AM

Scotty
Sketch shows my problem exactly. Thank you for taking the time to help. The other end of the tail goes to a Turn Table with no motor, can I use the same AR1 to reverse the polarity on the Table?

A DCC locomotive doesn't care what polarity the rails are; it's OK with having the polarity switch underneath it, unlike a DC engine, which will reverse direction. That's why you put a reversing unit on the tail end of the wye; it will switch itself to match the polarity of the track a train is entering.

Which is all a roundabout way to get to this point: If the turntable is powered by the same reversing unit as the rest of the wye's tail track, turning the turntable will cause a short, because the reversing unit can't match the other track's polarity without reversing that track's polarity too. So what you need is something to power the turntable rails independent of the rest of the wye. The simplest solution is to power the turntable rails directly from the DCC bus. That way, engine enters the tail of the wye, reversing unit flips the wye tail's polarity to match; engine enters turntable, reversing unit flips the wye tail's polarity (if necessary) to match it; turntable rotates and locomotive exits, wye tail's polarity flips again; then, engine leaves wye, and tail flips as necessary to match exit track's polarity.

But here's a serious question. A wye and a turntable can both serve the purpose of turning a lcoomotive. If you have one, why do you need the other?

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Steven Otte, Model Railroader senior associate editor
sotte@kalmbach.com

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Posted by Scotty on Monday, February 15, 2016 4:25 PM
Got it, thank you.
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Posted by Scotty on Monday, February 15, 2016 4:25 PM
Sketch shows my problem exactly. Thank you for taking the time to help. The other end of the tail goes to a Turn Table with no motor, can I use the same AR1 to reverse the polarity on the Table?
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Posted by Scotty on Monday, February 15, 2016 4:21 PM
Thank you. I understand.
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Posted by MisterBeasley on Monday, February 15, 2016 1:05 PM

It's important to note that, as the picture shows, the auto-reverse section must include the turnout, not just the leg beyond it.

It takes an iron man to play with a toy iron horse. 

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Posted by NP01 on Monday, February 15, 2016 10:05 AM

Sounds like you speak of the classic Wye shown in the picture below. As Steven said, only one of the legs needs to be a reversing section. 

(Photo from www.building-your-model-railroad.com)

Hope this helps. 

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Posted by Steven Otte on Monday, February 15, 2016 9:17 AM

You only have to isolate one leg of the Y. So wire your reversing unit to the leg with the single turnout, not the legs with two turnouts that attach to the main.

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Steven Otte, Model Railroader senior associate editor
sotte@kalmbach.com

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Wiring a reverse loop
Posted by Scotty on Friday, February 12, 2016 11:49 AM

I don't know how to wire a reverse "Y" with an AR1 because the "Y" connects to the Main in two places. In other words, the main is not split at the "Y" but joined to both ends resulting in 3 turnouts. Think of it like a "Y" with a line accross the top. Hope this is clear. Thank you. 

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