I am rebuilding my layout and want to incorporate a reversing loop. Normally, this would not be a problem, but I would like to turna 10 car passenger train. Because of the length it would extend over the line that connects both sides of the oval. I realize that I would have to isolate part of my mainline to include the length of the train. I understand the concept in going in one direction, but not sure what I would need to do in going the other direction.
to the forum. Your posts are delayed in moderation for a bit.
This is a case where a visible track plan would be helpful. Posting pictures in this forum is unique and you have to follow the directions here
Henry
COB Potomac & Northern
Shenandoah Valley
It sounds like you're talking about a simple oval with a single revering track bisecting it. What you'll have to do is divide th elayout into at least three blocks, the reversing section and two blocks on the oval, each "half" where it is divided by the reversing track. That way you can swap the polarity if each half of the oval to match the polarity at the two ends of the reversing track.
Hello All,
DC or DCC?
This makes a huge difference in how you can switch polarity.
In DC you will need a manual solution while in DCC you can use a manual solution or automate the process.
A track diagram always helps.
In a polarity reversing section only the electronic components need to be isolated in the section.
Unless the cars or caboose have electrical components; lights, axles with resistors for detection circuits, then only the motive power has to be in the section when the polarity shift occurs.
For example: If only the locomotive(s) is/are the only "electrical component" in the train, no matter how many cars being pulled- -even with metal wheels- -the entire length of the train doesn't need to be isolated in the polarity reversing section.
If however, you have a caboose or passenger car(s) with lights or rolling stock with resistors installed on the wheels for block detection, then those components need to be factored into the length of the polarity reversing section.
Keep the questions coming and...
Hope this helps.
"Uhh...I didn’t know it was 'impossible' I just made it work...sorry"
CSX RobertThat way you can swap the polarity if each half of the oval to match the polarity at the two ends of the reversing track.
wouldn't reversing the mainline polarity reverse it in both blocks?
greg - Philadelphia & Reading / Reading
Here we go again, if everyone would just ignore Laststpikemike maybe he will go away. He just enjoys mudding up every topic he can. Mel Modeling the early to mid 1950s SP in HO scale since 1951My Model Railroad http://melvineperry.blogspot.com/ Bakersfield, California Aging is not for wimps.
Folks, we don't even know if the OP is operating in DC or DCC, and we cannot be sure at this point what his layout even looks like.
Rich
Alton Junction
We need to know if this will be DC or DCC before we go much further.
I've built these crossovers on ovals, and if I had it to do again, I would extend the insulated sections outward, beyond the turnouts for the reversing section so that parts of the oval would actually be parts of the reversing section. This lengthens the reversing section.
I have run trains with illuminated cabeese and passenger cars. I run miy reversing crossover with DCC. It's a fast, solid state one, and tolerates the rapid changeovers at the end of the train well.
It takes an iron man to play with a toy iron horse.
While we are awaiting the PO to pony up a few more details and get through moderation, I had thought that metal wheels would trigger a short across the gap.
JJD has a different opinion.
jjdamnit -even with metal wheels- -the entire length of the train doesn't need to be isolated in the polarity reversing section.
If he is correct, why isn't there a short in that situation.
Lastspikemike richhotrain Folks, we don't even know if the OP is operating in DC or DCC, and we cannot be sure at this point what his layout even looks like. Rich Physically the reversing section is constructed the same way for DC or DCC. The only difference is how you reverse the "polarity".
richhotrain Folks, we don't even know if the OP is operating in DC or DCC, and we cannot be sure at this point what his layout even looks like. Rich
Physically the reversing section is constructed the same way for DC or DCC. The only difference is how you reverse the "polarity".
BigDaddy While we are awaiting the PO to pony up a few more details and get through moderation, I had thought that metal wheels would trigger a short across the gap. JJD has a different opinion. jjdamnit -even with metal wheels- -the entire length of the train doesn't need to be isolated in the polarity reversing section. If he is correct, why isn't there a short in that situation.
None are resistored and none of the rolling stock is lighted. Yet, metal wheels on each and every piece of rolling stock are detected by the controlling PSX-AR.
LastspikemikeWhy do you see three as the minimum?
That was my initial thought because he specifically stated his train would be longer than the reversing section. After thinking about it more, he could extend one end of the reversing section out onto the loop, although that could cause issues if he ever wanted to operate a shorter train within the reversing section while also operating one seperately on the loop.
LastspikemikeThe difference is only which switch on the Atlas Twin switch you throw. For DC it must be the one that controls polarity in the section the train is not in (unless you stop the train and really why would you?) whereas for DCC it doesn't matter.
LastspikemikeThe real issue is the OP doesn't seem to yet realize he actually wants two reversing connecting tracks, not just one.
Maybe just sit back and learn something this time.
Mike
jjdamnitFor example: If only the locomotive(s) is/are the only "electrical component" in the train, no matter how many cars being pulled- -even with metal wheels- -the entire length of the train doesn't need to be isolated in the polarity reversing section.
To clarify my response, I am NOT referring to metal wheels crossing the gapped section of track causing the DCC Auto Reversing Unit to trip at each pass of a wheel- -a "micro-short"- -for lack of a better term.
What I am saying is; if a train has metal wheels, and ONLY the motive power is drawing power from the track, crosses into a reverse polarity section, the only "component" (the motive power) needs to be completely in this section.
The rest of the train, with metal wheels, does not need to be entirely in the reversed polarity section. The cars can be half in the reversed polarity section and half in the non-reversed polarity section, as long as the metal wheel(s) are not bridging the gaps in the track.
In the April, 2021, Model Railroader magazine; pg. 46, in the article "Dealing with reversing sections" there is a graphic of what I am feebly trying to describe in relation to reversing polarity sections and units that draw track power.
If you just have metal wheels, particularly with plastic trucks, and the wheels don't provide power, and you don't stagger your insulation joints, then the contact is momentary and generally not much of a problem. However, if you're running a string of passenger cars with power from both rails going through both trucks, you have a long period where the auto-reverser needs to keep polarity aligned. If, at the same time, the engine at the other end of the reversing section also crosses to the main loop, the auto-reverser has an unresolvable conflict that only the 0-5-0 work crane can deal with.
jjdamnitWhat I am saying is; if a train has metal wheels, and ONLY the motive power is drawing power from the track, crosses into a reverse polarity section...
jjdamnitThe rest of the train, with metal wheels, does not need to be entirely in the reversed polarity section. The cars can be half in the reversed polarity section and half in the non-reversed polarity section, as long as the metal wheel(s) are not bridging the gaps in the track.
"Drawing power" is not the critical attribute, it's continuity between the wheels. If a car is wired for easy installation of track powered lights with the wheels of both trucks wired together, then the entire car has to be either in or out of the reversing section, even if it does not have any lights installed and therefore is not drawing power. If the car is not wired but the trucks still have continuity between the wheels on each truck, then each entire truck has to be in or out of the reversing section.
RR_MelHere we go again, if everyone would just ignore Laststpikemike maybe he will go away. He just enjoys mudding up every topic he can.
Well, that ain't going to happen so just let him speculate and pontificate.
LastspikemikeThe auto reverser sees the initial short from the lead axle of the train (that could be the first locomotive or the last car if the train backs into the reversing section). That sets the phase for the train to enter and travel through the reversing section.
DCC Auto Reversing Units don't see the short from the axle (paraphrasing).
The ARU detects feedback in the electronic signal or "short" and reacts appropriately. Some ARUs reaction times can be adjusted while some are factory set.
"Reactions" from an ARU can vary from a polarity shift to a complete shut-down of that circuit (track section).
The false premise that insulated metal wheels- -not specifically bridging the gapped track- -will cause the ARU to constantly phase shift in an endless loop (feedback) is not correct.
LastspikemikeThe locomotive and following cars will then trip it again and again at the other end of the reversing section and so on. You need the whole train to be inside the reversing section so that the auto reverser can reset the phase just once.
This opinion predicates that for some reason all wheelsets are electronically "connected".
In reality, unless the frame(s) of the car(s) is/are a conductive material, and the couplers are conductive making the entire train a "live load" then the sixth example on pg. 46; April, 2021, MRM applies.
CSX Robert"Drawing power" is not the critical attribute, it's continuity between the wheels.
Yes, I agree completely!
It's not THE critical attribute.
Any open circuit between the rails needs to be considered as a load or "drawing power" from the tracks or a "load".
That's why one caveat is wheels with resistors installed for block detection purposes.
When these metal wheelsets have been modified they also need to be considered when there is a polarity shift section that cannot accommodate the entire train.
See: Model Railroader Magazine, April 2021; Pg. 46, Fig. 1, Ex. 6.
jjdamnitAny open circuit between the rails needs to be considered as a load or "drawing power" from the tracks or a "load". That's why one caveat is wheels with resistors installed for block detection purposes.
I don't know what you mean by this, why would an open circuit need to be considered a load? It's not the load that triggers the autoreverser, it's the short. And what does that have to do with resistor wheesets, a resistor wheel is a load.
Resisitor wheelsets don't need to be considered any different than regular metal wheels when dealing with an auto reverser. If they bridge rails of opposite polarity (side to side) they simply put a light load on the track just as they are designed to do. If the wheel tread bridges the gap and creates a short, that would happen with or without the resistor.
You may get away with running metal wheels on a train that is longer than your reversing section, but best practice is not to. Even if the wheels are passing over the gap fast enough to not trip the autoreverser, you'll still be getting shorts and micro-arcing as the wheels cross. That's something best to avoid because it leads to dirtier track and wheels and possible pitting, and could even lead to reduced life of the reverser.
Personally, I'm not a fan of autoreversers anyway. They detect a problem and correct for it, I would much prefer to prevent the problem before hand by matching the track polarity before crossing the gap.
CGW103Every one of my metal wheels has one wheel that is insulated electrically from the axle. I don't see how a short is gonna happen.
When you cross a gap into a reversing section, if the polarity or phase dose not match the metal wheels will cause a short when they cross that gap.
CSX RobertWhen you cross a gap into a reversing section, if the polarity or phase dose not match the metal wheels will cause a short when they cross that gap.
That's what I thought but some seem to think it is so transitory or so "unloadworthy" that it doesn't make a difference. For some reason a Seinfeld episode about sponges comes to mind.
I have asked Larry Puckett on his youtube channel. Will report back
On a full size railroad wheel the area on the wheel that actually touchs the rail is only about a the size of a quarter. On an ho model it has to be quite a bit smaller. I highly doubt that could cause a short.
CGW103 On a full size railroad wheel the area on the wheel that actually touchs the rail is only about a the size of a quarter. On an ho model it has to be quite a bit smaller. I highly doubt that could cause a short.
If it couldn't, then your trains wouldn't even run.
I asked Larry "We are having a discussion on the MR forum as to whether an insulated metal wheelset (no car lighting involved) will trigger a reverser. Can you shed some light please?"
He responded
"If you are using a device that senses the mismatch in “polarity” like the dual Frog Juicer and several others, then metals wheels will trigger the autoreverser since there will be a short when the metal wheels bridge the gaps. Plastic wheels will not trigger the device."
Many years ago on a friends DCC layout I was helping build, we clearly observed that metal wheels of cars would short and trip auto reversers thereby requiring that reversing sections be longer than the longest train.
Does every wheel short out every time, likely not based on how your gaps are cut/created, how "big" they are and whether or not they are filled by insulated rail joiners or some other material.
In my case I use mostly metal trucks, so on one rail, the metal wheels do conduct to the truck and back to the other wheel and will short out over a gap of mismatched polarity every time.
Auto reverser theory is that the first wheelset trips the circuit, and now the polarity is correct for all the rest, and that it stay that way until the whole train is in the reverse section.
DC is no different, I would NEVER drag a train with metal wheels across gaps of mismatched polarity.
I have been reading some of this, and I am busy designing a wiring solution for another poster from another thread, so I will not get into all the questionable information posted here so far.
And I will repeat again, without seeing track plans, knowing what kind of control and operation is desired, it is near impossible to offer "best practice" solutions for this or any OP needing to deal with the "reverse loop" issue.
As a 54 year DC operator of model trains, and a professional electrical designer, I am constantly amazed at what some people don't know about electricity and model trains.
Sheldon
ATLANTIC CENTRALI am constantly amazed at what some people don't know about electricity and model trains.
not sure why you're so "amazed". the same could be said for plumbing, carpentry, ... as well as accounting, law, ... my in-depth understanding and experience has made me realize how ignorant i must be of other fields
having asked on forums, i believe a very significant majority of modelers are mostly interested in scenery and structures. joe f confirmed this recently. when i joined a large club, i was surprised to learn that only the owner of the house was an engineer. no one other than him had an electrical, much less an electronics background.
why? i think one reason is what my neighbor's mother said when i was thinking about college. she was british, had two sons that became engineers and recommended that they be mechanical engineers because -- you can see what the mechanism is doing. you can't see electrons flow.
i try to be patient. often frustrated by simplified the non-technical explanations. sometimes get confused myself. but have been surprised by the quick understanding of some.
i try to be succinct.
ATLANTIC CENTRALDoes every wheel short out every time, likely not based on how your gaps are cut/created, how "big" they are and whether or not they are filled by insulated rail joiners or some other material.
Here is another OP never to be heard from again after his first post. Everybody else and his brother replied, but not the OP.
How often does this happen?