I will have a wye that looks something like this:
My layout is HO/DCC. I've labeled the proposed track feeder wiring simply as black and red. There is an obvious problem with how to handle the section with the purple and green labeled feeders. I want to achieve continuous operation and I have heard about something called an "auto reverser". Will this solve my problem? If so, how does it work and how is it wired?
Thanks for any light you can shed on this.
Basically you would isolate that section of track, like you would in normal DC wiring for a reverse loop or track. The auto-reverser has two tracks that connect to that reverse section, and two that go to the regular track. When an engine enters the reverse section, if the polarity of the tracks don't match, the auto-reverser detects the short (as the engines wheels cross into the reverse section) and automagically change the reverse section polarity to match the regular track.
Here's a link to Digitrax's version. (It's nice in that it has an adjustment screw so you can set it so it trips correctly at the power your system uses):
http://www.digitrax.com/v1/ftp/ar1.pdf
You don't need to gap more than one of the three sides, but it should be part of the wye, not the base comprising the major line. So, in your diagram, your ? side could be wired any way you choose, but it should get its power directly from an auto-reversing unit. That unit, in turn, will get its power from the bus. Let it do the logic and reversing...it will. Your other two sides of this triangle will be oriented okay if you keep the same side orientation to the wires as you have shown. Black to the rail closest to the top right corner of the image, and red on the other sides.
As for gapping, only your ? side is gapped. The other two are not contra-oriented as they are shown, especially wired as you show. No need to gap them at all, anywhere.
selector wrote: As for gapping, only your ? side is gapped. The other two are not contra-oriented as they are shown, especially wired as you show. No need to gap them at all, anywhere.
Thanks!
Okay, I think I understand. I keep the entire "?" section of track electrically isolated from the rest of the track. Insulated rail joiners at the two turnouts?
Then, a train entering from the bottom heading to the right will cross the gap after the turnout, causing a short. The auto reverser will switch polarity and the train will continue. Then, when it crosses the gap at the other turnout (to the right), another short will occur and the reverser will switch polarity again. Correct?
Since it's DCC, it will continue in the same direction. Correct?
Gap both rails on the divirging route right after the turnout. Then hook up one side of the auto reverser to the main and one side to the remaining 'tail' of the WYE. If ou are using a Tortoise switch motor for the WYE, you can just use the contacts built into it to do the reversing rather than an auto reverse unit.
Jim
Modeling BNSF and Milwaukee Road in SW Wisconsin
AlreadyInUse wrote: selector wrote: As for gapping, only your ? side is gapped. The other two are not contra-oriented as they are shown, especially wired as you show. No need to gap them at all, anywhere.Thanks!Okay, I think I understand. I keep the entire "?" section of track electrically isolated from the rest of the track. Insulated rail joiners at the two turnouts?Then, a train entering from the bottom heading to the right will cross the gap after the turnout, causing a short. The auto reverser will switch polarity and the train will continue. Then, when it crosses the gap at the other turnout (to the right), another short will occur and the reverser will switch polarity again. Correct? Since it's DCC, it will continue in the same direction. Correct?
It may depend on the turnouts you use. I would suggest Peco Streamline Code 83 #6 because they will handle all but brass steamers with longer driver bases...you should be okay with plastic 2-10-2/4 and engines of the Northern type.
You can use plastic joiners if you are comfortable with handling them and if they work on the curves you generate for the legs of your turning wye.
Your description of the reverser's work is correct. On either end of the gapped leg, if the polarity is incorrect from one side of the gap to the other, the auto-reverser changes is to match in microseconds...seamlessly, and you engine will trundle along as if it were a real steamer on dead rails.
As Jim has pointed out, you could also put the reverser on the tail of the wye, where the train pauses, and then reverses out the other route of the wye turnout. However, in any case, the turnouts should be power routing on the turning wye so that when the route is lined at the turnouts, the power is right. That way, only the mismatch at either gapped end of the segment of isolated track is what the auto-reverser has to deal with.
You know that you will always have to make doubly sure your train length is never longer than the length of the gapped track...right? It isn't a problem with dead axles on trailing boxcars and such, but any lighted or powered devices, passenger cars for example, must be within the same length of contiguous track when the reverser acts.
selector wrote:As Jim has pointed out, you could also put the reverser on the tail of the wye, where the train pauses, and then reverses out the other route of the wye turnout. However, in any case, the turnouts should be power routing on the turning wye so that when the route is lined at the turnouts, the power is right. That way, only the mismatch at either gapped end of the segment of isolated track is what the auto-reverser has to deal with.You know that you will always have to make doubly sure your train length is never longer than the length of the gapped track...right? It isn't a problem with dead axles on trailing boxcars and such, but any lighted or powered devices, passenger cars for example, must be within the same length of contiguous track when the reverser acts.
The best place for the reversing section is the tail. Any cars with metal wheels (not just lighted/powered cars) will trip the auto-reverse. Which is why the reverersing section needs to be longer then the longest train length.
Nick
Take a Ride on the Reading with the: Reading Company Technical & Historical Society http://www.readingrailroad.org/
Nick, I just learned that you are right about the metal wheels. I had thought that they had to be separated electrically from the other rail, but I can see that when the metal tires bridge the gap on their own rails, they will possibly encounter the opposite polarity. Point taken, and I have learned something. Funny, we had this conversation just weeks ago, and no one corrected me. So, thanks for pointing that out.
I do think you are mistaken about the tail aspect, though. A train that can be contained within the bounds of a contiguous gapped length, whether on either side of the turning wye, or its tail, will trip the mechanism whenever the mismatch takes place, and that can be anywhere the gapped length is placed...don't you think? The need to trip will take place wherever the gap is, and that can be on any of the wye turnout's exits, or at the other end of the two legs of the turning wye at the other ends when the other gaps are encountered.
Have I forgotten something?
-Crandell
Jeff But it's a dry heat!
I am looking at page 29 in the (highly recommended),MR "DCC Projects" book. They show that you isolate both branches of the "tail" turnout with plastic joiners. The wirig of a "wye" is not the same as that for a simple reverse loop. The power to the Red main rail, is also branched through the auto reverse module to the Red wire on the "tail rail", (beyond the tail turnout). The "Black" power source that is connected to the black main rail, is also branched through the reverse module to the "black" tail rail, (beyond the tail turnout). Use "jrbernier's" advice to use Tortoise switch engines, which provide constant power to the rails, and have contacts that eliminate the need for auto reverse modules. The "power source" should be through a booster (which is protected by a "circuit breaker). This set-up makes sense, since the length of the train has nothing to do with it causing a short circuit. My layout's loops within loops, within wyes, is requiring the advice of our club's electronic engineer. Get help, or you may "fry" your expensive DCC equipment. Bob Hahn