My model railroad club has a WYE that leads into a staging yard that has approximately 30in radius curves. Our reversing section is about 3ft long. I am able to run walthers passenger cars that are lighting ready through it. Also freight trains with all metal wheels. Why doesnt this create a short? We tested it and subsequently used it at the 2014 Amherst Railway Society show this past January.
Running DCC or DC? What do you use to reverse the polarity of the reversing section? Toggle switches, DC automatic reversers or DCC AR's?
Running DCC/ Automatic reverser.
Edit: We havent run track powered lighted cars.
BMMECNYC Running DCC/ Automatic reverser. Edit: We havent run track powered lighted cars.
Depending upon the sensitivity of the auto-reverser, metal wheels and lighting-ready cars may not cause a short.
Locomotives and lighted passenger cars surely will.
What kind of auto-reverser are you using?
Rich
Alton Junction
On my layout, using PSX-AR units, the metal wheels and lighting-ready passenger cars don't trigger the auto-reverser but they do cause my crossing signals to misbehave. I use NCE BD20s as occupancy detectors and they are very sensitve, picking up current from the Walthers passenger cars even though I have not installed interior lighting.
Im not sure about that module, but I think we have PSX-ARs on our fixed club layout, again no lighted passenger cars, same installation, only 3-4ft for the reversing section. They are quite bulky about 3"x4"x1" boards with a metal shield (hence the x1") to prevent accident death by ESD I would guess. But I dont know the brand or model We just installed IR cross track detectors for Crossing Flasher application, they were a stretch with 3 track main on our modules but they seemed to work.
When a locomotive or lighted passenger car enters a reversing section the PSX-AR detects a short circuit condition and quickly corrects the short by reversing the polarity in the reversing section, so the train continues on. If you get a solid short circuit in the reversing section and the PSX-AR cannot correct it, the unit will act as a circuit breaker and keep the power off until the short is corrected.
A passenger car that is lighting ready, but without lighting, should not be drawing any current
If you have plastic joiners in the gaps for the reversing section, it may be nearly impossible for any one metal wheelset to touch both sides of the gap at once - the little palstic tab on most of them that's there to keep the ends of the rail from touching ech other usually sticks up slightly above the rails. If you cut the gaps with a Dremel and filled it with epoxy or a piece of styrene and then filed it smooth, same thing.
Plus, not only does a wheel have to bridge the gap at the entrance long enough to activate the autoreverse, at the exact same time, another wheel has to do the same thing at the exit of the reverse section. Now you'd have one end saying flip this way, and the other end says flip that way - a short. That's got to be extremely rare that the train is stretched just right to do that.
Unless you have cars with all wheel pickup, or metal wheels with metal axles in metal trucks, there's no connection between one wheelset and another, so even if the truck is straddling the gap, there's no path for current to flow.
--Randy
Modeling the Reading Railroad in the 1950's
Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.
What I am discovering about this thread is that there is resistance to making the reversing section long enough to accommodate the longest train.
While I will agree that a reversing section can be as short as the longest loco consist, that leaves no room for future expansion of your fleet of rolling stock, no lighted passenger cars, no end of train devices.
I will stand by the traditional recommendation. If you can, make your reversing section as long as your longest train.
Sometimes you can't make the reversing section as long as your longest train and even then it may not be necessary to make the section very long. When the first power drawing axle enters a reversing section and the polarity shifts it stays that way for the entire consist, including lighted cars. Even if you have a car with a FRED at the end it woudn't matter. My club has a WYE on our layout with the reversing section being about 14 inches long. A three loco consist makes it through fine even though both ends of the consist are out of the section.
One issue, and, admittedly, not all that common, is one loco entering and one loco exiting, simultaneously.
We could go on and on.
Actually, if one loco is entering a reversing section from one end and another is coming in from the other end at the same time, wouldn't the polarity of the reversing section be the same for both?
What is saving you from endless torment with the short reversing section is the PSX-AR. These are solid-state circuits, and they flip the polarity very rapidly. I have a reversing section that's a bit longer, but still too short for my longest trains. Most of the time, though, everything goes through without a hitch. I've got almost all metal wheels on my rolling stock, and I run lighted passenger cars, too. My PS-REV (the predecessor to the PSX-AR) is flipping the polarity back and forth many times as that passenger train passes through, but I don't even notice.
It takes an iron man to play with a toy iron horse.
We have some club members running trains as long as 50 cars through reversing sections connected to PSX-AR modules controlling sections as short as 2 feet, and none of them ever cause any problems, even with metal wheels; but all the rolling stock truck side frames are plastic, not metal. We got rid of every Kadee metal truck because they were shorting out the layout
Only if a locomotive consist is 4 or 5 units might the PSX-AR shut down the section in the event of two locomotives' wheels being in opposite ends of the reverse section simultaneously, but that is a rather rare occurrence.
Thank you for the explanation.
retsignalmtrActually, if one loco is entering a reversing section from one end and another is coming in from the other end at the same time, wouldn't the polarity of the reversing section be the same for both?
No, if it was, the you wouldn't need the reversing section.
retsignalmtr...My club has a WYE on our layout with the reversing section being about 14 inches long. A three loco consist makes it through fine even though both ends of the consist are out of the section.
Then that must not be the reversing section. The whole idea behind a reversing section is the polarity or phase of the track at each end does not match, so the section itself can match one end or the other, but not both at the same time. If you have a powered loco straddling both ends of the reversing section at the same time then you will have a short.
The trouble is the walthers cars that have both left trucks shorated to each other. Each time the car leaves a block and enters another block, for couple seconds (=time for the 85' car to pass the insulated joiner) theres a dead short betwen the left rail of block A and left rail of block B. And same for the right rail. There is no load between rails though (lights not yet installed).
This irritates my AR-1, my signalling system and me!!
NP.
BMMECNYC My model railroad club has a WYE that leads into a staging yard that has approximately 30in radius curves. Our reversing section is about 3ft long. I am able to run walthers passenger cars that are lighting ready through it. Also freight trains with all metal wheels. Why doesnt this create a short? We tested it and subsequently used it at the 2014 Amherst Railway Society show this past January.
Ken G Price My N-Scale Layout
Digitrax Super Empire Builder Radio System. South Valley Texas Railroad. SVTRR
N-Scale out west. 1996-1998 or so! UP, SP, Missouri Pacific, C&NW.
No, was simply asking why it worked. Which was explained by someone else several posts up.
BMMECNYC No, was simply asking why it worked. Which was explained by someone else several posts up.
Oops, missed that post.