Last night at the club we were discussing the need to always run a train shorter then the length of the reversing section. This particularly with an all metal wheels train or an all lighted passenger cars or a freight train with a caboose or rear end device taking power from the track, as a dead short is sure to occur.
While we all agreed to that statement, some said there is sure a way to overcome that and maybe it is a trivial solution. Since none of us could come up with an answer, I wonder if someone here can shed some light on this subject.
Maybe there is no solution to this dilemma.
Edit: Forgot to mention this is with DCC.
Jack W.
I had on my first layout a section that was reversing and it was just section of flex track and I used the Digitrax reverse (AR something) and running DCC. It worked with locos MU'ed and I would often run trains to where the front just missed the last car on the track it was reversing around and never had any trouble and all my wheels are metal. Sometimes I would hear the reverser clicking but it did not stop the trains. Now I am not sure how that would work with a DC set since that is reversing the current and not adjusting the phase like DCC does.
That all depends on the truck, wheel and the car
For example:
If the wheel is metal and fully isolated (doesn't conduct to anything other than itself) then you will throw the auto reverse every time you short the gap with it. It could possibly short if you stop over the gap perfectly.
If it's the truck (metal side bolsters with metal points on wheel axels) then it will short out.
If it's a like a walthers heavyweight where front and rear trucks share the same wire, then you will definitely short it out.
Is it possible? Yes
Are you asking for trouble: YES! YES YES YES YES!
I don't see why you would need to make your reversing section smaller than the train any way. You'll just be running into your own tail if you sectioned it properly.
Don - Specializing in layout DC->DCC conversions
Modeling C&O transition era and steel industries There's Nothing Like Big Steam!
Yes most of the time with an all metal wheels it will pass OK but sometime the train will hesitate. With all lighted passengers cars or a caboose/end of train device picking current from the rails it is different a dead short occurs every time.
If your only concern is metal wheels, then a short section of dead rail at each end of the reverse loop will prevent shorts. If you have trucks that electrically connect the wheels, then the dead rail has to be longer than these trucks. If you have a caboose or rear-end device that gets power from the track, then you just have to make sure the train is either short enough or long enough that the caboose/rear end device does not cross the reversing section boundary at the same time as the locomotives. If you have lighted passenger cars where the front trucks are electrically connected to the rear trucks(or even if the car is not lighted but wired for it), then you are out of luck, there is no easy solution.
There is no way out of this dilemma. With an all metal wheels train, or an all lighted passenger car train, or a freight train with a caboose or rear end device taking power from the track, the reversing section needs to be longer than the longest train. Otherwise, a dead short is certain to occur.
Rich
Alton Junction
richhotrain There is no way out of this dilemma. With an all metal wheels train, or an all lighted passenger car train, or a freight train with a caboose or rear end device taking power from the track, the reversing section needs to be longer than the longest train. Otherwise, a dead short is certain to occur. Rich
Only true for lighted passenger cars. See my previous post for how to handle the other situations.
But....
You can almost always be creative with the reversing section, and make it longer, up to the limit of the physical section (when the nose and tail of the train would hit each other anyway). Sometimes our perception of the reversing section gets "stuck" and we can't see the options for the location of the electrical reversing section.
Jeff But it's a dry heat!
After further though, you can even make it work with lighted passenger cars, but you have to rewire the cars. Have a dead section longer than a truck and wire a bridge rectifier between each truck and the lighting circuit.
In the situations with trucks that electrically connect the wheels, the length of the dead section is very critical, because you cannot bridge both ends of it at the same time. Ideally, you want the dead section barely longer than a truck; however, depending on the cars, that might allow the trucks on two adjacent cars to bridge the two ends of the dead section at the same time. If that is the case, then the dead section needs to be long enough for the two trucks on adjacent cars to be completely in the dead section at the same time, yet still short enough that the dead section will fit between the two trucks of a single car. With varying lengths of cars and trucks, this may not always be possible.
CSX Robert richhotrain: There is no way out of this dilemma. With an all metal wheels train, or an all lighted passenger car train, or a freight train with a caboose or rear end device taking power from the track, the reversing section needs to be longer than the longest train. Otherwise, a dead short is certain to occur. Rich Only true for lighted passenger cars. See my previous post for how to handle the other situations.
richhotrain: There is no way out of this dilemma. With an all metal wheels train, or an all lighted passenger car train, or a freight train with a caboose or rear end device taking power from the track, the reversing section needs to be longer than the longest train. Otherwise, a dead short is certain to occur. Rich
Nuts, I stand corrected on the all metal wheels train. I knew better but misspoke anyhow. As the OP subsequently indicated, the all metal wheels train will create a momentary short as the wheels enter the reversing section, but a dead short will not normally occur.
This thread does raise an interest issue, however, concerning the length of the reversing section.
As CSX Robert indicated, the length of the reversing section generally needs to be longer than the length of an all lighted passenger car train. Otherwise, a dead short will occur as the engine exits the reversing section while some, but not all, of the lighted passenger cars are still in the reversing section. In that situation, as the next of the lighted passenger cars attempt to enter the reversing section, a dead short occurs because the lead engine is also outside of the reversing section.
In the situation where a freight train with a caboose or rear end device is drawing power from the track, I have to agree with CSX Robert. A dead short? It depends. If only the engine(s) and the caboose or rear end device are drawing power from the track, then as long as the engine(s) have exited the reversing section before the caboose or rear end device tries to enter the reversing section, no dead short will occur. In that instance, the reversing section only needs to be longer than the engine or powered engines in a consist. (Of course, if the reversing section is too much longer than the engine or powered engines in a consist, then a dead short could still occur if the caboose or rear end device drawng power from the track tries to enter the reversing section while the engine or powered engines in a consist are still in the process of exiting the reversing section.)
The reverse polarity issue only causes a conflict where the length of the train results in units drawing power from the track when such units are both inside and outside the reversing section at the same time. For that reason, the general rule about reversing sections should still be adhered to whenever practical to do so. The reversing section should be longer than the longest train. If there are no units other than the engine(s) drawing power from the tracks, the reversing section should be longer than the length of the longest engine or powered engines in a consist.
Thanks to all the replies, a very interesting and informative dialog took place. I will print the thread and show it to the club's members. CSX Robert I will give a try to the short section of dead track you are referring about.
Thanks all.
It always amazes me when people try to "bend" the rules.
If you use metal wheels in plastic trucks, then you only need to worry about the wheels themselves. For that, as short section of dead track (like made of plastic) about a quarter-inch long will suffice, and shouldn't stall locos as only one axle at a time would be affected. For metal wheels, metal trucks and a plastic body, then a full truck-length of dead track is needed. That can hurt engine performance, particularly short ones.
I've got an oval with a diagonal crossover. The reversing section is just the part inside the oval, although I could be creative and enlarge it to include half the oval as well. Still, I almost never have a problem, even with illuminated passenger cars.
I think my secret is the Tony's Trains PS-REV, the solid-state autoreverser that they made before the PSX-AR. This is a very fast-flipping circuit. Being completely electronic, the flip-over time is much shorter than the less expensive relay-based units. When I run a passenger train through the loop, I'd imagine it flips over a dozen times or more, but I don't even notice.
It takes an iron man to play with a toy iron horse.
DigitalGriffin It always amazes me when people try to "bend" the rules.
I appreciate your concern, but don't worry the club is in existence since for 30 + years and we will not do anything to jeopardize the layout. If CSX Robert trick does not work we will simply revert back to what it was before and see what can be done to increase the length of the reversing section. For the time being lets just say that I learned a bit from this thread.
MisterBeasley I think my secret is the Tony's Trains PS-REV, the solid-state autoreverser that they made before the PSX-AR. This is a very fast-flipping circuit. Being completely electronic, the flip-over time is much shorter than the less expensive relay-based units. When I run a passenger train through the loop, I'd imagine it flips over a dozen times or more, but I don't even notice.
This is most interesting, we are using a 10 years old MRC auto-reverser, do you think a PSX-AR would be a better tool?
jalajoie MisterBeasley: I think my secret is the Tony's Trains PS-REV, the solid-state autoreverser that they made before the PSX-AR. This is a very fast-flipping circuit. Being completely electronic, the flip-over time is much shorter than the less expensive relay-based units. When I run a passenger train through the loop, I'd imagine it flips over a dozen times or more, but I don't even notice. This is most interesting, we are using a 10 years old MRC auto-reverser, do you think a PSX-AR would be a better tool?
MisterBeasley: I think my secret is the Tony's Trains PS-REV, the solid-state autoreverser that they made before the PSX-AR. This is a very fast-flipping circuit. Being completely electronic, the flip-over time is much shorter than the less expensive relay-based units. When I run a passenger train through the loop, I'd imagine it flips over a dozen times or more, but I don't even notice.
Some types of decoders (Sound decoders in particular) are more sensitive to power drop outs than others. A mechanical relay takes time to "flip" the polarity. As a result it's slower than solid state. If you are having momentary drop outs in reversing sections, this might be your solution.
Now to address Mr Beasley's statement, once the train enters the reverse loop, it is of the correct phase. So even if a metal wheel crosses sections, they will both be of correct phase. The only case where this would not be true is if the train is longer than the reverse loop. In that case, Yes you would have a series of momentary shorts as the wheel bridges sections.