Thank you for your interest and desire to help One of the guys at my local shop tells me that I DO NOT have to use a reverse polarity unit like the one Digitrax offers on the reverse loop of this layout, but from previous posts that I've found on the Atlas forum (when it was up & running ) says you do have to use one. I am in the wiring phase of this layout and I am not too experienced when it comes to electricity and DCC I am using the Atlas Commander set up and later as time and money permits...I will upgrade to Digitrax One more thing...How do you "post" pics on this forum? I'll try to add a pic of this particular layout in order to facilitate more info on what I am pursuing with this post. Thanks! Rob
Rob, Any reverse loop or wye needs a way to change rail polarity so that no shorts occur when the metal wheels of the loco cross the insulated gaps between the loop and main line. You can use a DPDT (double pole double throw) toggle switch to manually change the rail polarity, or use one of the automated devices that are available. The toggle switch is cheapest, but requires manual operation while the train is in the loop. If you check any book on layout wiring for DC operation, the same applies for DCC with respect to reverse sections. And remember that changing the rail polarity can be done while a train is moving. The DCC signal tells the loco which direction to travel, not the rail polarity. Russ
After the advise given you, I would be suspicious of future advise from them. Use an automatic reverser and if this is the layout of your dreams, then latter, a turnout that will automatically throw the mainline so that you can have continuous running. The reason I say latter is that you will need sensing devices(2)to detect direction as well other equipment to do the throw for the turnout, based on the sensor's info. Of course, you will want an override so that the turnout can be operated manually as well.
Thanks for your replies guys! RSN48, you lost me on your post. "if this is the layout of your dreams, then latter, a turnout that will automatically throw the mainline so that you can have continuous running. The reason I say latter is that you will need sensing devices(2)to detect direction as well other equipment to do the throw for the turnout, based on the sensor's info. Of course, you will want an override so that the turnout can be operated manually as well". Can you elaborate a bit more or direct me to a source about this? A book, diagram...Your expertise has never let me down Thanks a lot!
With a reversing loop, you have to manually or electrically throw the turnout so the train can proceed after traversing the loop. So, with reversing loops, you can't have continous running of a train. By continous running, I mean no "hands on" involvement of the training moving down the mainline. By using detectors and a decoder to respond to the detectors, an electrical turnout can be thrown automatically once the train has gone around the loop, so that it will proceed back down the main line, without having to use a "hands on" approach to throwing the turnout. But occassionally, you might want to use the reversing loop in switching operations, hence the "manual" override of the "auto" function.
Thanks for elaborating my question! It makes more sense now... Does Digitrax have these sensors you talk about? Robert from the Rockies!
Digitrax doesn't and this is an area I am not super knowledgeable because I am not "there" yet on my layout (with 2 reversing loops). But there are sensors available - and I can't tell you which ones are best. But there is a lot of info out there on sensors as they are also used for detection in train signaling; so they have been around for a long time.
Automatic reversers are available from a couple of sources. MRC makes a really cheap one, about $20, but it has a tendency to make excess noise. At our club we have 3 reversing sections (two loops and a wye) and we have used a TTX product, the Power Shield Reverse/Breaker. They work smoothly and flawlessly under heavy operation, but will run you a little more money at $40. Here's a link to the product page. http://www.tonystrains.com/technews/new_pscombo_details.htm
Thanks a lot for that info guys! So, as far as it goes...the N-16 layout has two reverse loops that need to be isolated individually with each loop having a dedicated reversing unit? Or will one unit will do? Rob
Well, that will depend. It certainly is possible, but what is the distance between the loops? If they're close, ok, but if they're at other ends, it's a problem. Also, if you plan on having a train on each loop simultaneously, you can't do it, because you will get conflicting phases. So in short, it can be done, but I strongly advise against it.
Corey, Have you seen a drawing of the N-16 layout? The two reverse loops are next to each other on the lower right. So far, all I have done is drop the feeders, but I have not purchased any reversing units until I get this clarified. Electricity and I do not mix, but I can follow instructions if they are provided Thanks for helping out Rob
Corey, Bottom line is this: If you know that only one reverse loop will be used at a time, you can use just one reversing unit. And, the reverse loop, or block, needs to be longer than your longest train, assuming you use metal wheels. This because metal wheels crossing the gaps are what activates the reversing unit. If wheels cross the gaps at both ends simutaniously, or are crossing the gaps of the other reverse loop simutaniously, the reversing unit will attempt to reverse polarity back and forth, creating an undesirable effect to say the least. If funds are a problem, buy one unit and make sure you only enter or leave reverse blocks one at a time. Note that a train stopped within the reverse block will not be affected by the polarity change. This assuming it is not an analog loco. So you can have a staged train in one loop while entering the other loop. Once the train clears the gaps, the other train can depart. The physical location of the loops makes no difference. If money is not a problen, do yourself a favor and buy two. Also, I initially bought the MDC units, I have replaced them with Tony's. The MDC units usually worked with diesels, but sometimes with a short delay which required me to reset the default time setting on my digitrax chief. they do not work at all when metal wheels in the pilot trucks of my steam locos crossed them. My breaker would trip every time. This is not a problem with Tony's. I don't know for sure, but think the MDC unit requires a current draw in addition to simply having the gap bridged. I noticed the polarity would not change when the gap was crossed with a screwdriver blade. I highly recommend buying two of Tony's units if feasible. Gary
I didn't want to reply to this thread until I found the page with the diagram I saw for manually switching a reversing section with DCC. I found the site tonite and here it is: http://www.loystoys.com/rev_sec_ctrl.html There are a few good ideas for DCC users on the page, even if you don't use Digitrax (I use a North Coast Engineering Powerhouse Pro system.) Drew
