Maybe I'm missing something but would it matter if a loco was on one reversing section and a car in the same train with metal wheels was still on the other, the metal wheels on cars are insulated and the second reversing section wouldn't even know its there. I think the only time you might have a problem is if a loco or car with lights bridged both reversing sections at the same time, I can't see a problem as long as the distance between the two sections is longer than your longest powered car or loco.
If he is only running one train he could use only one auto reverser and have the putside loops part of the main and the inside segments in the auto reversing section.... but I do think that two reversers would be a better bet incase he dicides on more then one train later.
Every reverse loop needs it's own individual reversing module. If you wire two reverse loops to one auto reversing loop module, a major short circuit will occur if two trains enter both reverse loops at the same time. If you are going to use reverse loops in DCC do it correctly, one reverse loop needs its own reverse loop module/switch.
Bob, I don't think that is strictly true. If he were running only 1 train on the simple layout above, he could get away with one reversing module for the two loops... but he would hook the reversing module to the center V of track...He would still need to break it up into two reversing sections but instead of a module on each end, he could use one module in the middle. Of course, he is running two trains sometimes, so two is the way to go.
Sean: I had four reverse loops on the original JJJ&E plus a turntable. I used to run two -three 28 car trains on that layout all the time. The only proper way to wire a reverse loop is to give each reverse loop its own reverse loop module/switch. For the cost of a $20 reverse loop switch, why jeopardize ruining locomotives on a layout. It makes no sense. However you can wire your reverse loops in any manner you wish....It's your railroad. I'll wire my reverse loops in the manner described above. The "original" JJJ&E ran without any issues (four reverse loops) for nine years. Why take shortcuts to save $20? The original statement said two trains were going to be run at the same time, so putting two reverse loops on one switch is completely out of the question and should never have be suggested or considered.
Everyone who suggested a single autoreverser qualified their statements with the limitations of that option. Staying dogmatic in looking for solutions should never be suggested or considered. Explaining how one reverser can do the job if one is only running one short train, opens up the problem to a more complete understanding of how these things work. By extension, his track plan suggested how an autoreverser can solve a sticky issue like a double crossover without resorting to Rube Goldberg style wiring. And if proper modern circuit protection is implemented, even a miswired reverse loop should never result in damaged equipment.
I totally agree that two reversers is the way to go. I was just playing with theory... For a while I was thinking of using just a few reversers for ALL of my yards frogs. The theory is that you just have to make it so you would never cross two frogs on the same reverser and you could then power all of your frogs with reversers and not worry about polarity when throwing the switch. Neat idea, but I did not do it. So again, for the record, two reversers are the way to go in the target layout.
This layout is very close to one that I'm running. My DCC layout uses a Peco double slip switch for the 3-4 segment. I used two autoreversers from Tony's TrainExchange. The left side reversing loop consists of track segments from point 3 counterclockwise back to point 3. The double slip switch is fed stock track power (not controlled by autoreverser). The right side was a little tricky because the 2-4 segment was very short. I lengthened the right side reverse section by adding a DPDT switch controlled by the switch at 2. When S2 is reverse the the track segment to the right of 2 is fed from the right side autoreverser. When S2 is normal then the segment is fed from stock track power. Nancy
I use metal wheels on all my rolling stock. With metal wheels the reversing section must be as long as the last car with metal wheels. Nancy
You have a misunderstaning of what the autoreverser is doing. It is reversing the phase of the entire reversing block. It is exactly like a manual DPDT switch. It does not send a command to the decoders in the locomotive to do anything. How would an autoreverser know the address of which locomotive is bridging the gap at any given time? Answer: It doesn't. And it doesn't need to because that is not how it works. By definition, the polarity of the rails at one end of a reverse block will always be out of phase. A reverser can only match the phase at one end of the block at a time, not both. If you have a train just the right length such that you have a metal wheel across each set of isolation gaps at each end of the reverse block, you will cause a short. Typical worst case is a passenger train with lighted cars (powered by track power) which is effectively a string of 85' (scale) long jumpers that will absolutely cause a short if the train is longer than the reverse block. Edited to add: I guess I will need to quote your entire post in the future so that when you delete your entry it does not disrupt the flow of the thread.
Regarding the rail gaps, is there any advantage to staggering them? I placed all of the gaps at the ends of the switches. Nancy
I have not found that it makes any difference if the gaps are staggered. DCC Specialties does suggest when using their PSX autoreversers that the gaps be staggered about 1/8". The reason they give is that the current needed to sense the short may be reduced by the staggered gaps. Their PSX-AR devices are circuit breakers as well as autoreversers and I think the idea here is that you want the autoreverser to trip on as low current as possible so that it can try and correct the fault before the breaker has a chance to trip. We have three of their PSX-AR devices on our club layout and because of convenience in track laying, the gaps are not staggered. With the circuit breakers set at the default 3.5 amp trip current, we have had perfect operation of their autoreversers. I suppose it is possible that other brands of autoreversers could behave differently.
Why? The metal wheels are insulated so no power goes through them from one rail to the other, they are the same as plastic wheels as far as power goes.
Only one metal wheel bridges the gap between the two isolated rails. Picture a 1/32 inch gap with a metal wheel sitting in the gap making contact with the rails on both sides. If those rails are phased differently, there is a short circuit. A short will also occur if two wheels on the same truck are electrically connected through the truck. e.g. lighted passenger car trucks. One wheel will be in contact with the reverse section, the other with the main line. Either case shorts for only a fraction of a second but that's long enough to trip a DCC auto reverser. Martin Myers
But the metal wheel does allow current to flow across the rail gaps. On one side of the gap is the reversing section. On the other the rest of the layout. As I described above, one end of the reversing block is always going to be out of phase with the rest of the layout. Whether you use an autoreverser or a DPDT switch makes not difference: One end will be in phase and the other will be out of phase. If you have a train long enough to simultaneously bridge the gaps at both ends of the reversing section with their metal wheels, you will create a short. You might luck out for a while with metal wheels alternately bridging the gaps on one end then the other as the train moves, but sooner or later you will have wheels hit the gaps on each end simultanerously. With long conductive wheelbases like locomotives and lighted passenger cars, it becomes certain you will cause a train halting short. You need to draw a picture of a simple reversing loop through a single turnout and label the rails with + and -. Trace around the rails and see how one end of the loop will always be ready to cause a short at the gaps. All that is needed is a conductor to bridge the gap.
