Using your example, once the first wheel on Axle #1 triggers the reversal, the polarities match and stay matched until the first wheel exits the reversing section. When Axle #2 crosses the gaps and enters the reversing section, the polarities are already matched, so the auto-reverser takes no further action at this point.
So, on a 6-axle locomotive, once the first wheelset trips the auto-reverser, the remaining 5 wheelsets cross the gaps and enter the reversing section without causing the auto-reverser to trip again.
I followed the instructions and staggered my gaps. I am not qualified to judge their recommendation, but I believe what they are saying is that 2 shorts at once will reduce the current below what they can detect.
One side effect I’ve noticed is that because only one of the 4 wheels on a truck passes over the gap at a time, the rigid truck causes the wheel to ride over the gap rather than dropping in and creating a short. Mine doesn’t reverse when a steel wheeled car rolls over the gap - only a locomotive triggers it.
This recommendation from the manual is the one that really boggles my mind:
If your train is longer than your reverse block and has metal wheels, you may need to cut additional gaps into the reverse section. Simply cut another set of gaps at both ends of the reverse sections inside of the original gaps. The distance between these gaps and the original gaps should be longer than the wheelbase of any metal truck.
The likelihood of bridging the gap at both ends at the same time can depend on the kind of cars being used. On my old layout, normal freight and passenger trains fit in the reverse section (using a DCC auto reverser), but ore trains were too long so the last 8-12 cars and caboose were entering the section as the engine(s) were exiting. Since the ore cars are so short, with so many metal wheels so close together, it was very common to get a short. Fortunately at that time I still had a fair no. of ore cars with plastic wheels so always made sure to run them at the end of the train.
does anyone know how to wire these sections between the additional set of gaps?
If I understand this correctly, by cutting these extra sets of gaps there are three sections: the main reverse section which is several feet long and a very short section (~1/4") at each end.
if these short sections are wired to either the reverse or mainline section, what’s the point in cutting the extra gaps?
Actually, you left out the last part of that comment in the PSX-AR manual.
If your train is longer than your reverse block and has metal wheels, you may need to cut additional gaps into the reverse section. Simply cut another set of gaps at both ends of the reverse sections inside of the original gaps. The distance between these gaps and the original gaps should be longer than the wheelbase of any metal truck.
What I find perplexing about that last sentence is that it states that the distance between these gaps and the original gaps should be longer than the wheelbase of any metal truck. Since wheelbase is defined as the distance between the front and rear axles, that distance on a truck is inevitably going to be greater than 1/4". Also, that sentence refers to a “metal truck”. What about a plastic truck?
Quite frankly, that whole paragraph leaves me confused. I just don’t have such problems on my layout and I have four PSX-AR units, each controlling a different rever
Second gaps and staggered gaps are different animals. If you do the second set of gaps and the distance between the two pairs of gaps is less than the wheelebase of a metal truck, you run the risk of fixing nothing, in that the lead axle could be crossing the original gaps while the rear axle is crossing the new second set of gaps. While at the same time, another powered unit or some such is crossing the entrance gaps of the loop. Avoided, if the reversing section is longer than your longest train - none of this should be necessary if that is the case, just an isolated section powered by the AR. It’s when you start bending this rule that problem soccur. Note is is usually not an issue with a wye, either the tail track is as long as your longest train, or it becomes so because only a train that fits completely on the track and clears the turnout can be reversed on said wye. Simple balloon loops too are self regulating - you can’t run a train longer than the loop through it, or else the engine will strike the cars that haven’t yet cleared the turnout. It’s the more complex and tricky almost hidden loops that can have issues with train lengths.
Now, the whole idea of leaving dead sections as long as the longest metal truck wheelbase is asking for stalls, if you ask me. I don;t run passenger cars, so the longest conducting truck would be the ones on my Trainmaster (which are longer than most any passenger car anyway). So you would be effectively making a dead section that puts one whole truck on unpowered track. Such would be the case if you made the gaps spaced to handle a 6 axle passenger car but also run ordinary 4 axle diesels - not just tiny things like critters (those have zero chance of making it past such an arrangement without keep alives), but regular size things like standard F units and Geeps.
Best plan: just avoid such situations altogether. Relocated gaps if necessary, so there is no way a train can cross to sets of gaps that require the reverser cont
One thing worth mentioning is that rolling stock (passenger and freight cars) with metal wheels that are unpowered may not actually trigger the auto-reverser, depending upon the trip level of current. So, in some situations, it may be possible to get away with running a train that is longer than the reversing section of track, while still using only one pair of gaps at either end of the reversing section.
I don’t understand why it should matter if the wheels are unpowered? Or do you mean that having a truck with pickups so that a short exists for as long as both wheels are on opposite sides of the gap?
on the other hand, like the trucker racing across the bridge, does it matter how long the short exists?
What I am saying is that in some instances a locomotive pulling a string of cars with metal wheels can run through a very short reversing section, in which the train is longer than the reversing section, without causing a short.
my original post questioned whether a reverse section must be longer than the train and suggested that for a longer train, the auto-reverser will toggle multiple/many times as the train straddles the reverse section.
several people have said they’ve had no problems doing just that.
i don’t believe you need to hope that the auto-reverser doesn’t toggle when a metal wheel bridges the gap on a long train because it doesn’t excede the trip current of the reverser.
So Rich made me think about cars with pickups (e.g. lighted passenger). The pickups in each truck typically make contact with each wheel in a truck. A car with pickups doesn’t just possibly cause a short when a single wheel bridges the gap, but as long as both wheels straddle the gaps.
will there be a problem if a wheel without pickups bridges a gap at one end of a reverse section while a truck with pickups straddles a gap at the other end?
the wheel bridging the gap causes a short and the auto-reverser to toggle, but reversing the section polarity now causes the truck with pickups still straddling the gap to cause a short. will the auto-reverse quickly toggle a second time and everything is ok?
what would happen if trucks with pickups simultaneously straddle the gaps at both ends of the reverse section? Is this where the short isolated sections described in the PSX-AR manual are needed?
A train travelling 5 scale mph travels 1 in./sec. At 25 scale mph takes 200 msec/in. What does an auto-reverser do if sees a persistent short? for how long?
Not always. It SHOULD be a short, it’s a piece of metal crossing a gap. But if there is a spacer in the gap and it’s not flush with the railhead, the wheel can lift right over, like there was a ramp there, and never contact both sides of the gap at once. Atlas insulated joiners have a vertical bar that sticks up slightly above the railhead, and if you cut your own gaps and fill with a thin piece of styrene and then file to shape, you’ll have much the same thing unless you file all the way down into contact with the railhead, which then introduces problems of its own with scratches in the rail surface.
Even if this is NOT the case, inless the wheel is squeakly clean and the car it is used on has some weight to it (like NMRA recommended weight) AND the rail at the gap is nice and clean, the ‘short’ may not be a very low resistence one. For example, when I make resistor wheelsets, I put a 10K resistor on each axle I am converting, then paint in the conductive silver paint to complete the circuit. It doesn;t really conduct until the paint dries (solvent suspending the silver particles evaporates) but even so, 9 time out of 10, if I take a wheel set with otherwise clean wheels, and set it on a clean piece of track connected to my multimeter, it still shows as an open circuit, until I apply some gentle pressure to the wheels. When I pop them back in the trucks and put the completed car, which is weighted to NMRA standards (some are heavier, like open hoppers with their loads) and put it back on the same track, I get the correct reading.
So it’s both the speed of one tiny part of the wheel tread touching both sides of the gap as well as the quality of said contact that determines if the AR device even sees the mismatch to be able to take action.
In other words, they got away with running a train with all metal wheels that is longer than the reversing section. Metal wheels encountering reverse polarity across the gap should trip the auto-reverser but that does not always occur, as Randy so elegantly explained.
I have seen situations where a train that exceeds the length of the reversing section trips the auto-reverser on some passes but not on others. So when you crearte such a situation on your layout, all you can do is hope that the auto-reverser will detect the short and correct it.
you can’t rely on luck and I suggested that you don’t have to.
for a long train straddling both ends of the section, the auto-reverser should alternately toggle the polarity in the reverse section as whees bridge the gaps at alternate ends of the section. I see nothing wrong when this happens.
If for whatever reasons one set of wheels bridging the gap doesn’t cause the reverser to toggle, that’s fine. Maybe the next one will. But you can’t rely on that happening all the time.