I have installed an AR1 on a wye. This is a very simple arrangement at a junction between a main line and branch, with no other reversing sections on the layout. The reversing section is one side of the wye. Each end of the section has been double-gapped, and power feeders have been run from the reversing section to terminals 1 & 2 of the AR1, and from a main (normal-polarity) track section to terminals 4 & 5, as per installation instructions. There are no track feeders from the reversing section to the power bus, or from the AR1 to the power bus. The layout powers up normally and runs fine.
When locomotives enter the reversing section, they will cross the first gap with no problem, but will short out at the second (if the are travelling through the wye in the opposite direction, they will short out at the first gap, and cross the second with no difficulty). Once I push the locomotives across the gap manually, they resume normal operation.
Faulty AR1, or faulty installation? Thanks in advance for any advice.
Dayliner: I agree with Richhotrain’s comments. One question: Does that AR1 reset after the short? There is an adjustment for current tolerance on the AR1 (you probably know this). It might need to be adjusted, or the adjustment mechanism might not be working properly.
Dayliner: Sorry I forgot this part: Does any part of the train extend beyond the reversing section of track? That can interfere with its proper functioning.
This should not be a problem unless you are running passenger cars or a caboose, etc., with interior lights. If all the rolling stock wheel sets are insulated they should have no affect on the AR1’s operation.
I disagree. A metal wheel rolling across the gap can cause a short and trigger the AR to reverse whether or not there is an electrical load in the car.
Rich, I had originally connected terminals 4 & 5 directly to a “normal polarity” section of the track. After reading your reply, I have reconnected those terminals to the power bus, but the problem persists. Parenthetically, Digitrax’s instructions on this point aren’t too clear, and suggest that the connection be made directly to the rails. I’m not sure how to post a track diagram in here–as I explained in my original post, the reversing section is one side of the wye, between two turnouts that face each other. The gaps are located 2.5 and 4.5 inches in from the frogs respectively; the turnouts are Atlas Code 55 (powered frogs). The short occurs at either end of the section, depending on the polarity of the section (i.e., how I hook it up to the AR1).
Ray, I have adjusted and readjusted the TTC screw to no avail. I can’t say whether or not the AR1 resets. As I say, if a push the locomotives across the gap manually, the system resumes normal operation.
With respect to train length, all that I am trying to run through this side of the wye at the moment is a pair of consisted Atlas GP9s. They fit in the section fine. Normally, all that will be run through this side of the wye is either (a) consisted power being turned, usually no more than two units; or (b) very short trains, two or three cars at most. That’s the reason I selected this side of the wye as my reversing section, as it will not normally have long trains running through it. In any case, most of my rolling is equipped with plastic MT LP wheelsets.
Thanks to everyone for your comments and suggestions.
Make sure you have gaps that are entirely ‘clean’. Any material that is the least bit electron tranmissible will allow some current to get across the gap. This includes ballast with water from taps that was added to glue mixtures. Make doubly sure your rails are cut clean-through, all four gaps on that side of your wye.
What turnouts are you using? Pecos are power routing sometimes, even if not designed to do that. I have some Pecos that show current thrown either way and others that show no current on the non-lined route.
I had similar problems earlier this year after making a similar setup with a PSX-AR. I finally cut two sets of gaps to account for possible train lengths greater than the reversing section, per DCC Specialties’ instructions. What I mean is that, to keep a single metal truck and tire set from causing a short, but also to run trains longer than the reversed side of the wye, you cut double sets of gaps just sufficiently far apart to be longer than any of your metal passenger car trucks’ axles.
With proper and clean gaps, and the power for that entire length only being afforded by the AR, there is no reason for you to get shorts, except for one tip…you are suggested to stagger the gaps by a couple of mm at each end so that they are not in line transversely across the rails to keep any one axle from shorting the system when both wheels cross their gaps simultaneously. Otherwise, there is another issue, perhaps power to the AR, or the AR itself.
Thank you for those tips, Crandell. I have gone back and taken a razor saw to the gaps and ensured that the rails are cut through entirely and that the gap is free of any debris, but no joy. The track is newly-laid and hasn’t been ballasted yet, so I can count out that potential culprit.
The turnouts are Atlas Code 55 (with powered frogs). So far they have been utterly dependable everywhere on the layout.
At the moment, the length of the reversing section is not an issue. Never say never, but I don’t plan to run long trains through that length of the wye. It will only be used for turning locomotives or for routing very short trains, and the reversing section is long enough for those purposes.
Your point about the staggered gaps is well-taken, and of course now I remember reading about it somewhere else. Foolishly, I made the gaps at one end of the reversing section in perfect alignment with each other, and I can now see the potential problems it may cause in the future. However, I can rule it out as the source of the present difficulties, because by reversing the polarity on either the input or the output of the AR1, I can move the short to the other end of the reversing section and trains run fine across the “aligned” gaps.
The AR is powered directly from the track bus; the track is getting power and the trains run across the section until they get to one or the other sets of gaps. The only source of power to the reversing section is the AR. It looks like I’m doing everything by the book, but I’m beginning to think the problem is a dud AR.
Thanks for posting this, Rich. I should just clarify that all turnouts are powered frog Atlas 55s. Gaps and feeder are marked in red; you can ignore the other little lines across the track.
Are these N Scale turnouts? If yes look at the turn out frogs. On Atlas N scale code 55 turnouts, there should be a gap between the frog and rails. Some times the rails shift and touch the frog which will cause a short. Push the locos past the frog, the short goes away. I’m helping a friend build his N Scale layout with code 55 Atlas. I found a problem turn out where the loco shorted out because the rails were touching the frog. Get a sharp X acto blade and CAREFULLY push it between the frog and rails if this is your problem. Joe.
Just as a follow-up to this whole issue, the OP and I have been emailing back and forth in the Messages section. A test track was set up to determine if the AR-1 is performing properly, but it is not.
The test track was properly wired and gapped so that if the AR-1 was operating properly, the loco should be able to move back and forth across the gaps entering and exiting the reversing section without a short occurring. But the shorts persist.
If the output wires from terminals 1 and 2 are reversed, the short will occur at opposite ends of the reversing section. If the input wires from terminals 4 and 5 are reversed, the short will occur at opposite ends of the reversing section. So, it seems as if the AR-1 is faulty and acting as nothing more than a set of rail joiners between three sections of test track with the reversing section being the middle track.
We would be interested in any other thoughts or comments on this issue.
I want to thank everyone who contributed to this discussion. It is always helpful to get a number of different perspectives on a problem like this.
As Rich said, he and I have discussed this fairly extensively, and at his suggestion I set up an isolated test track not connected to any turnouts. The AR1 behaved exactly as it did on the layout. Our conclusion is that the problem lies in the AR1 itself–an unusual situation but I guess it happens from time to time. I’ll pick up a new unit this week and let you know how it works on the layout.
Once again, thanks everyone, and particular thanks to Rich for his suggestions and help.
Sounds like the cause has been found. The wye was a really simple setup, pretty straight forward as far a wiring. OP had it wired right, your test showed it to be a bum AR-1. Good investigative work.
Dayliner and Crew: I have exactly the same set up (wye leading to a branch line) and a very similar shorting problem. Simple wye, with one leg isolated and connected to the AR-1 and the main connected to the AR-1.
But, in my case, the short resets after a moment or two (the loco does stop) and then the loco/lashup completes the transition. This happens to me as to Dayliner, one direction only.
On my layout, the main line and bus are all connected to the Digitrax DB100 thru a PM42.
Dayliner hasn’t mentioned whether he is using a PM-42 on his layout.
In my case, is it possible that the AR-1 and the PM 42 are conflicting/competing to resolve the polarity discrepency? If so, would the solution be to remove this portion of the layout from the PM-42 and run directly into the DB100?
It sounds like you need to play with the settings on your AR1 and the PM42. First make sure the trip current setting for the PM42 is at least 3 amps. 3 amps is the default setting and the limit will apply to all four PM42 sections. Short circuit sensitivity should be at standard. This can be set differently for each section so you only need to adjust the one that’s powering the AR1. Slower may work as well but there is the possibility that the booster may trip before the PM42 section. Try standard first which is also the default setting.
Now adjust the AR1 until it operates faster than the PM42. Best way to do this is to just keep running an engine back and forth through the reverse section and adjust the AR1 until the PM42 stops tripping but the AR1 works as advertised. After getting the reverser adjusted, quarter test the reverse section just to make sure the PM42 will still trip when it’s actually needed.
