trafficdesign mlehman This is a case where either will work. It's a matter of tradeoffs in design. Those are often a matter of personal preference or experience. Don't see it as a conflict, so much as two different ways to do it. What's important is whatever way is more comfortable for you, so this may be the case where you want to take a few days to digest all the alternatives. I will indeed ponder the alternatives. Not as easy as I thought.... A question... if I decided to change the layout to a single cross over near the top loop and a second single crossover near the bottom loop with 2 AR1s and 2 reverse loops... How do I wire the in between? I get the wiring concept as presented in this schematic BUT no idea how to wire it "in phase" as you put it.
mlehman This is a case where either will work. It's a matter of tradeoffs in design. Those are often a matter of personal preference or experience. Don't see it as a conflict, so much as two different ways to do it. What's important is whatever way is more comfortable for you, so this may be the case where you want to take a few days to digest all the alternatives.
This is a case where either will work. It's a matter of tradeoffs in design. Those are often a matter of personal preference or experience. Don't see it as a conflict, so much as two different ways to do it. What's important is whatever way is more comfortable for you, so this may be the case where you want to take a few days to digest all the alternatives.
I will indeed ponder the alternatives. Not as easy as I thought....
A question... if I decided to change the layout to a single cross over near the top loop and a second single crossover near the bottom loop with 2 AR1s and 2 reverse loops... How do I wire the in between? I get the wiring concept as presented in this schematic BUT no idea how to wire it "in phase" as you put it.
You gap each crossover in such a way that you completely isolate each end loop, creating a reversing loop out of each one. All of the track in between the gapped sections is simply wired so that all of the red feeders connect to one rail while the blue feeders connect to the other rail, thereby in phase.
Honestly, though, my best advice is to leave the two crossovers where they are and create a single reversing section right there. One AR-1, less maintenance, less messing with wiring. Or, if you are feeling a little more ambitious, add that third track and have even more fun.
If you are at all worried about where those mainline gaps are located once you start running trains, buy a couple of inexpensive signal bridges that span two tracks and place those signal bridges right over the gapped mainline rails. Then, as trains approach from opposite directions, one train can stop right before reaching the signal bridge. Both Model Power and Bachmann make these signal bridges for around $10 to $12 each, and they will look cool and prototypical.
No one has yet given a convincing reason for creating two reversing loops, one at each end of the layout. Why do it? You still have the same issue of two trains simultaneously entering and exiting the reversing loop. I just see no reason to do it. Why create two reversing sections when you only need one?
Here is a teaser for you. if you are still in doubt what to do, how about moving those two crossovers left and place them just below the loop on the bottom of the layout. Gap the rails appropriately and make that end loop your one and only reversing loop. That end of the layout looks to be the least busy anyhow.
Rich
Alton Junction
Train length is important here because the auto reversers sense the short circuit that occuers where the gap is bridged between the track a loco is on and an adjacent section of track with the opposite "polarity" )since it's DCC, it's different than DC polarity, but the concept works so we'll avoid that discussion). The reverser acts quickly to change the section the loco is entering to the matching polarity. It happens so fast you don't even notice.
When a train is so long it bridges the gaps at both ends, the reverser just keeps flipping the juice in the opposite direction. Back and forth, back and forth, etc. So the train gets "stuck" in the reversing loop, or the reverse quits. This happens if any of the cars crossing the second gap have metal wheels.
An exception is if all the part of the train longer than the reversing section has plastic wheels, then it won't "trip over" the gap while the front with the locos is also crossing it.
Since Rich's version would keep the reversing section in the middle, you could send trains cross it when the polarities match that are longer. But keeping track of when that is will be difficult; there are ways to put in signals to tell you of a mismatch, but you're talking about one more thing you have to build, buy, maintain, and adjust. So it's best just to be certain no trains longer than the reversing section pass through it by making it long enough.
Mike Lehman
Urbana, IL
Like so many things, there is more than one way to skin a cat. I'd personally go with the two loops even though it means a second reverser, just because it is easier to understand.
A more typical scenario with a dogbone shape layout is that one crossover is near one loop, and the other near the opposite loop. That makes it a bit more obvious of how a single reverse section in the middle works. In this case, both crossovers are close together, near one end. That makes the potential reverse section rather short. Another reason I would prefer using the two loops themselves.
The issue with a short reversing section - assuming it's long enough for any anticipated loco consists, is the there IS power transfer if you run any lighted passenger cars. Or sound making cars like some of the new mechanical reefers. And if you run all metal wheels like I do - there is always the chance of one set of wheels on the gap at one end, and another set of wheels from another car on the gap at the opposite end. Momentary short, and maybe it only happens on 1 trip out of 1000, but it can happen. If the reversing sections are longer than the longest train (especially if there is another limit on the layout that means you can;t even accidently throw in 3 extra cars becuse it simply will not fit), there's no chance at all of something bridging the gaps at both ends simultaneously (short of failing to pay attention and having trains on a collision course).
--Randy
Modeling the Reading Railroad in the 1950's
Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.
trafficdesign Also I understand it here....not sure how to do it if I make the north and south loops the reverse sections.
Also I understand it here....not sure how to do it if I make the north and south loops the reverse sections.
By all means do what your comfortable with but gapping the reversing loops is really quite simple. At the place where the double track main line diverges to form the loop, gap both tracks. If you have a reasonable radius on the loop, it is unlikely you will have a train that is long enough to cross both gaps at once. If that is an issue, just move the gaps a little farther down the line away from the loops. Do that for both loops and each one is seperate reversing section.
trafficdesign Time to vote? Thanks everyone!
richhotrainAs originally drawn in the OP's very first diagram, the crossovers still are points of reverse polarity. To overcome this and the resulting shorts, all of the trackwork outside of the two end loops would have to be wired in phase, the opposite of his current feeder wire plan. Rich
Yeah, the feeders may have to be reset the way I'm thinking of the two loops, but that's not a problem. Here's what's happening and why this work with two loop reversing section only. Ever thing in between the two reversing sections is treated like a long double-track line for wiring purposes.
I was thinking about how this would work in DC and it made my head hurt. Since we're doing DCC, I'll stick to that. We have all track in between wired like a long double main. It is only where the two are connected by the end loops that anything is a problem -- and then only if the crossover is used after navigating the loop.
The key here is navigating the loop. An auto reverser simply toggles polarity back and forth as needed when it senses a short across one of the two pairs of end gaps.
The two ends of the loop reversing section will be different. One will match the "out of the loop" track and the other that is the opposite and doesn't. If our train enters the reversing section and no short is detected, things already match. Then as it navigates the loop, it comes to the second set of gaps. Zap! A short and the autoreverser trips. Train continues on.
Or the train shorts at the first set of gaps. Then when it comes to the second set, everything matches and it continues with no drama. The train can continue around the track looping and all section will find polarity matching.
Or the train can take the crossover when it comes to it. If it does, it will go on through, because the polarities match. The train continues down the line just fine, returning on its previous track. It is only when it comes to teh erversing section that issues may arise. If the first set of gaps in the reversing track matches the main trains on, it will continue to the second set, which then trips the breaker,. reverses polarity, matching the track the loco is entering.
mlehman richhotrain the problem remains that the crossovers each represent a point of reverse polarity that still has to be dealt with. Rich, I'm not so sure about that. If reversing was needed, because the train travels the loop, it's already been reversed back in the loop before it returns to the crossovers. In this case, it's just standard wiring to avoid a short when the crossover are thrown against each other, but it's not an actuall reversing section anymore. But I may have overthink this. Gotta go finish breakfast.
richhotrain the problem remains that the crossovers each represent a point of reverse polarity that still has to be dealt with.
Rich,
I'm not so sure about that. If reversing was needed, because the train travels the loop, it's already been reversed back in the loop before it returns to the crossovers. In this case, it's just standard wiring to avoid a short when the crossover are thrown against each other, but it's not an actuall reversing section anymore.
But I may have overthink this. Gotta go finish breakfast.
As originally drawn in the OP's very first diagram, the crossovers still are points of reverse polarity.
To overcome this and the resulting shorts, all of the trackwork outside of the two end loops would have to be wired in phase, the opposite of his current feeder wire plan.
If you look at the very first track diagram in the OP's initial post, the mainline is wired as a continuous loop with the outside rail color coded red and the inside rail colored blue. Because it is a continuous loop, the turnouts that form each crossover join the red rail to the blue rail and the blue rail to the red rails, producing dead shorts. To overcome this reverse polarity situation, all of the track outside of the end loops would have to wired the same, top rail (if you will) colored red and bottom rail (if you will) colored blue. Once in phase, there will be no reverse polarity at the center of the crossovers since blue rail will connect to blue rail and red rail will connect to red rail.
That said, I don't see the advantage of making the two end loops as reversing sections. You still have the problem of two trains entering and exiting simultaneously and it requires two AR-1 units instead of only one.
richhotrainthe problem remains that the crossovers each represent a point of reverse polarity that still has to be dealt with.
Basically, all that's involved in making the loops into reversing sections is to gap a section at both end that is longer than your longest train. It can be anywhere along the loop, in case that matters for any reason. People often associate turnouts with reversing sections, but lots of the time, they're not even included in the reversing section itself.
Turnouts are included if you do the reversing section in the center. They aren't if you choose to make it in the loops instead.
One more thing, and this helps me a lot since I tend to be somewhat dyslexic about electricity, is that doing the reversing section as part of the loop avoids any potential confusion when it comes to trouble-shooting later on. All you have in the loops to worry about in analyazing a problem with a reversing section is a pair of rails. In the center, it'll be somewhat more complex.
Bernard, if you made each end loop at reversing section, you would simply gap the entry and exit points of each loop and add an AR-1 to control each reverse loop. That would be all well and good, but the problem remains that the crossovers each represent a point of reverse polarity that still has to be dealt with. So, then you would need a third AR-1 to deal with that third reversing section. The best solution is to deal with the crossovers as part of a single reversing section.
I prefer the third track solution because that gives you more flexibility to keep trains moving and, quite frankly, adds to the fun of operating the layout.
Let's see how the others vote.
trafficdesign Fabulous stuff. Thanks to all who are responding. That looks doable however, I am taking a few minutes to read and absorb and will post my thoughts. Bernard
Fabulous stuff. Thanks to all who are responding. That looks doable however, I am taking a few minutes to read and absorb and will post my thoughts.
Bernard
Glad we could help. Reversing loops is one phase of electronics that I think I have good understanding of because it is pretty much the same issue as back in the DC days with block wiring. What's changed is the autoreverser. I don't think they were available thirty years ago. That's one of the best inventions this hobby has seen in recent times. Sure beats the old days when you had to manually change the polarity of the mainline for trains coming out of the reversing sections.
It really comes down to this. If the owner is willing to bear the cost of two ARs, I think making the loops the reversing sections is the best solution as it will offer the greatest flexibility, such as adding crossovers at a later date. You could use a single AR for both loops but that's asking for trouble with multiple operators. If the owner wants to get by with a single AR, making the crossover the reversing section seems the best solution, as long as it is long enough that a train won't be crossing two gaps at one time. The trade off for the single reversing section is that if future crossovers are added, it will require another reversing section. That wouldn't be an issue if the loops are each made a reversing section from the start.
Mike, my apologies. I misread your prior reply.
I mistakenly thought you meant that the OP would only have one reversing section.
My bad.
richhotrain mlehman gregc I think this is much easier to understand if there were only a single crossover. greg, Very true, but then you would only have reversing in one direction. And that would be bad because? Rich
mlehman gregc I think this is much easier to understand if there were only a single crossover. greg, Very true, but then you would only have reversing in one direction.
gregc I think this is much easier to understand if there were only a single crossover.
greg,
Very true, but then you would only have reversing in one direction.
And that would be bad because?
Because they're involved with this revrsing section thing I presume the crossovers are there so that whole trains can be turned, in addition to the operational possibilities not related to reversing they provide. If you want to turn whole trains, at least without backing up in one direction, you generally want to reverse them when running forward in either direction. You can do that with two crossovers (or one double crossover), but just one crossover will leave you backing up in one direction to reverse.
So, ten 50' boxcars in HO scale totals 70 inches, add 20 inches for two locos, add 6 inches for good measure, total of 8 feet. That will be the required length of your reversing section. Can you make it fit, as proposed?
Would you consider a double crossover in lieu of the two single crossovers?
How long will your longest train be?
Hoping for 10 50' boxcars and 2 engines. Should mention also HO scale and am modelling modern day freight operations.
How far does that upper east west set of tracks extend before turning sout?
See pics attached
How long long is that north-south run?
See pics attached.
Bernard, I'm not sure if you answered this, but how long will your longest train be and how far does that upper east west set of tracks extend before turning south and how long long is that north-south run?
Here is an intriguing possibility depending upon the length of the longest train and the length of those north-south mainlines.
The left side mainline could bypass the crossovers altogether in the following configuration, and the gaps in the middle of the two crossovers could be eliminated by wiring the middle track inside the gaps in phase with the right side mainline. The question is, does the OP have the space to do it.
mlehman Rich, My thoughts on this were because I wasn't sure about what the planned ops were. I was thinking of a train using one of the crossovers while another train was pulled up close to use the other pair of switches. It would have to stand well back of the turnouts or it would be in the reversing section depending on which line the trains were on.
My thoughts on this were because I wasn't sure about what the planned ops were. I was thinking of a train using one of the crossovers while another train was pulled up close to use the other pair of switches. It would have to stand well back of the turnouts or it would be in the reversing section depending on which line the trains were on.
Mike, I do see your point, and it is valid. I will take the liberty to expand upon it. A train traveling south on the right side mainline has now completed the bottom loop and is headed north on the left side mainline about to crossover onto the right side mainline. A train headed south on the left side mainline would have to stop before crossing the uppermost gaps to avoid conflicting the AR-1 as the northbound train crosses the gaps on the lower crossover.
That said, safety rules would mandate that the southbound train on the left side mainline not get too close for fear of a head on collision. So, the OP should mark the mainline gaps with signals or other markers so that trains do not proceed beyond that point.
gregcI think this is much easier to understand if there were only a single crossover.
Then there was future ops. The top part of the layout seems well-developed, but I wondered if the sparseness of the lower right area and the loop back to its left was due to the intent to use it for expansion later. That might add track to the area to the left of the crossovers that might result in complications with the reversing section being adjacent. But that's future/unknown stuff and one can always rewire and cut new gaps if needed. Your solution works for the current track arrangement in that area.
rich
i think your solution is best.
The top and bottom insulated gaps can be moved further away, but moving them all the way around the loops back to the turnouts just creates a too short "non-reversing section".
i guess there's nothing to prevent two trains crossing the reversing section gaps creating an impossible state for the auto-reverser.
I think this is much easier to understand if there were only a single crossover.
greg - Philadelphia & Reading / Reading
mlehman I'm not going to disagree with Rich that this can be done with a single reversing section, but I do want to throw a caveat in to think about. It doesn't ncessarily mean you shouldn't put the reversing section in the middle, just consider if it will work with your ops as envisioned... The thing about automatic reversers is they tend to like one train in the reversing section at a time. If you get more than a single train, either entering or leaving, things can get confused. This is usually not a problem with loops, as they tend to be at the end of the line and thus tend to get trains one at a time simply by virtue of that location. A reversing section right in the heart of the busiest part of the layout might be a handicap when trying to observe the one train at a time rule, even if long enough to accommodate the longest train. This is because that train will have to enter or leave the reversing section and no other train can enter the reversing section until it's completely clear of the previous train to avoid baffling the reverser. If that sounds like a limitation, it may be a case for going with two reversers and using a section of the loop at each end for the reversing section instead. If it doesn't, then Rich's solution will save you a few bucks and work just fine.
I'm not going to disagree with Rich that this can be done with a single reversing section, but I do want to throw a caveat in to think about. It doesn't ncessarily mean you shouldn't put the reversing section in the middle, just consider if it will work with your ops as envisioned...
The thing about automatic reversers is they tend to like one train in the reversing section at a time. If you get more than a single train, either entering or leaving, things can get confused. This is usually not a problem with loops, as they tend to be at the end of the line and thus tend to get trains one at a time simply by virtue of that location.
A reversing section right in the heart of the busiest part of the layout might be a handicap when trying to observe the one train at a time rule, even if long enough to accommodate the longest train. This is because that train will have to enter or leave the reversing section and no other train can enter the reversing section until it's completely clear of the previous train to avoid baffling the reverser.
If that sounds like a limitation, it may be a case for going with two reversers and using a section of the loop at each end for the reversing section instead. If it doesn't, then Rich's solution will save you a few bucks and work just fine.
Mike, I think in the OP's situation, there is a greater likelihood of two trains in the reversing section if it is one of the loops, as I indicated to greg. In my proposed solution, trains can pass each other on the mainline without any issue since only the one on the left side mainline would be entering or exiting the reversing section. On the other hand, it is not likely that one train would be entering the reversing section, as proposed, while another train is using one of the crossovers because of the possibility of a collision. This would be particulary true if the reversing section were just long enough to accommodate the longest train. I would not be concerned in the least placing the reversing section in the heart of the mainline.
greg, you could it the way you proposed but what I would be concerned about with that arrangement is the greater possibility that two trains would be inside that bottom reversing loop at the same time, or on entering as one is exiting. The reason for my solution is that the reversing section would be just long enough for one train and without the practical possibilty of another train entering or exiting the reversing section at the same time.
If there were only a single crossover, he would need three sets of gaps instead of four.
trafficdesign There is NO problem with creating mainline gaps 10 feet south of the gaps in the turnouts, but will there be a problem gapping 10 feet north with the current track arrangements and turnouts?
There is NO problem with creating mainline gaps 10 feet south of the gaps in the turnouts, but will there be a problem gapping 10 feet north with the current track arrangements and turnouts?
What is the distance from the center of the top crossover to the turn west at the top of the track diagram?
And how long will your longest train be?