There is and Atlas warns about this because the sparking can pit wheels and rails.
I know for a fact that the trains will still run fine. The short caused by the wheel tread is so momentary a DC powerpack won’t trip.
For DCC the problem is that momentary short will trip the auto reverser. The 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.
Have you tried this? Thought not. Even a DC powered train won’t “stop” if you flick the Twin Switch across center off, it reverses immediately. DCC won’t even notice the interruption in power. Certainly an onboard keepalive would prevent this from happening. Some decoders from QSI treat the reverse switch as a DCC signal substitute when running in DC mode. The interruption on power is almost indiscernible.
Nobody can know what another person is thinking, ever. One can know what a person wants even if they do not yet know it themselves. Advertising developers depend on this phenomenon.
Since the OP refers to “the other direction” it seems clear he has not noticed that there is no “other direction” across the reversing section he describes. By considering the "other direction&
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.
The April 2021 article in MRR does not mention the possible metal wheel effect.
The metal wheel effect will not trigger a DC powerpack short circuit protector. It of course will send a signal to a DCC auto reverser because that’s how they work. The idea is the auto reverser stops getting any wheel shorting signals for long enough that the last phase change it detects aligns the phase for the exit point.
The 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.
As the same lead set of wheels leaves the reversing section the wheel bridges the exit gap and the auto reverser can again reset the phase to match. Only the decoder needs the phases to match.
The issue is one of probability. Could the lead wheelset trigger a phase change at approximately the same time as a trailing wheelset under a car do the same thing. How lucky are you on a regular basis?
“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.
Well, that ain’t going to happen so just let him speculate and pontificate.
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.
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.
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.
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.
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.
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.
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.
Sheldon, it might be time for ‘post 3’ explaining exactly where the ‘short’ of a metal wheel occurs, why it doesn’t matter if the wheelset is cross-insulated or ‘resistored’, why it trips some devices but not others, and how proper gap design (e.g. wide kerf with epoxy filler) solves it. Until all those things go in one coherent post this discussion is likely to continue going pretty much nowhere.
Across the gap in the rail. It’s that short the auto reverser or Twin switch is required to address, the short is in the same rail not through the axle to the other rail. Ironically, that other rail is the same polarity as the rail that does short.