Switch Crossovers

[Anonymous]

In using 2 switches to form a crossover between two loops of track (each loop powered by a different transformer), do I need to fully insulate tthe switches from each other?

Thanks

[Anonymous]

Cut a gap in the center rail between the turnouts or use an insulated track pin [round wooden toothpick or anything that won't conduct electricity].
Be sure your two transformers are in phase with one another because your Commons will be connected via the outer rails.
Try to set the voltage on both transformers about the same when running an engine across the gap or insulated center rail.

[lionelsoni]

If your switches have anti-derailing control rails that require an insulating pin, you may find that you have also inadvertently insulated both outside rails between the two loops, which you don't need. In that case, you may need to establish a connection between the common of the transformers and both loops' outside rails.

Simply running across a gap from one transformer to the other can be dangerous, although it is a little safer than running between two outputs of the same transformer. I recommend using a single-pole-double-throw switch for each loop to select which transformer it is connected to. Then you can connect both loops to the same transformer for the move between loops.

[Anonymous]

They are Lionel O22 switches so they do require the insulating pins.

[Anonymous]

lionelsoni, would several of the 180 watt power bricks of a modern ZW be considered seperate, individual transformers, or are they considered as one with regard to the danger of running from one track powered by a transformer outout onto another track powered from an alternate output?

[Anonymous]

I routinely crossover between power districts supplied by PowerHouses linked to TPCs without any problem, including lighted passenger cars where the pickup rollers are straddling the insulated gap between the two districts in the same manner as the two engine engine pick-ups.

The fixed voltage of my different district PowerHouses operating in Command is an advantage in this regard and if operating in Conventional one can regulate and match voltage of both transformers/districts via tthe unit's throttles or Cab 1. In addition to the voltage,I have always watched the panel ammeters on both districts when crossing and it is easy enough to balance the load in the districts if that emerges as a problem in crossing. I always anticipated the problem would arise when crossing with a 10-11 lighted car consist but It has just never been a problem. Of course , engines with mechanical and electronic innards both, have been crossing between insulated power districts on our layouts for years.

As suggested [above] one can set up toggles or rotary switches to temporarily control both power districts from one district's transformer. If you are operating in TMCC, the Block Power Controller [BPC] is designed to temporarily control both districts via the Cab 1 remote until the crossing is complete.

[Anonymous]

This discussion has me wondering. I am using an old Lionel SW transformer. While I am currently only using one side, I was going to re-wire my layout this weekend and isolate the inner and outer loops via switches. I was going to just wire the loops to seperate sides of the transformer. Will I run into problems with the outer rails? I thought this was what the SW was designed for.

[phillyreading]

If you use a large enough transformer you can safely power both loops from one transformer and supply a fixed voltage to the 022 switches. Here is how I have done that with a post-war ZW, control handles A & D supply power to the loops while control handle B or C powers the 022 switches using the fixed voltage plug on the side of the solenoid.
Lee in West Palm Beach FL

[Anonymous]

I have been told that crossing from one power district to another, where one pick up roller is in one district and the other, connected, pick up roller is fed by the other district, can be a problem for newer engines. Apparently, if there is a difference in the voltage supplied to each district, like 10 volts to one district and 13 volts to the other district, you can get a flow of current from one transformer output to the other, and this is a problem. In older, post-war locos and cars, it apparently is not much of a deal if done quickly and intermittently. With the newer electronics in the engines with TMCC or DCS, it apparently is a real threat to the engines' electronics. I did burn out a DZ-1000 switch motor on a Ross double cross over when I did a cross over from one district to another. The switch motor was connected to the tracks via a relay to control the power to the diamond rails. In any event, the "short circuit" caused the switch motor to die, and it also killed the relay. Luckily, it did not seem to hurt my engine, but I'm not taking that risk again.

[lionelsoni]

VA, crossing between blocks powered by separate controls on the same transformer is the most dangerous situation. Because Lionel put the circuit breaker in series with the common terminal, to save the expense of separate circuit breakers for the two non-common terminals, there is no protection against the fault current that flows between them when the gap is bridged. If it is only for an instant, there is no harm. But if, for some reason a train should stop on the gap, with the controls in different positions, a very large current will flow indefinitely, with a real danger of a fire.

Trevor, I'm not familiar with the design of the modern ZW; so I can't say how well they have taken that kind of operation into account.

[Anonymous]

What Bob Nelson says about the postwar ZW is correct. You should add fast acting circuit breakers or fuses to the A and B outputs of the postwar ZW.

The situation is better with the modern ZW or TPC300/400 being fed by powerhouses. The modern ZWs and TPCs vary the output voltage by chopping the sine wave so when the pickup rollers bridge two power districts, the first unit to turn on winds up supplying power to both districts until the second unit turns on. . When the 2nd unit turns on, the load will be shared between the 2 units as the bricks are fixed 18 volt transformers (you should verify that the bricks are in phase as some of the early 180 watt powerhouses were wired out of phase). Note that the wire between the pickup rollers will have to handle the load to the 2nd district until the 2nd ZW or TPC turns on. Since the wire between the pickup rollers is rather small, you should add fast acting fuses or circuit breakers to all the outputs (the powerhouse breakers may not act quickly enough if there is a short passing through the pickup rollers).

Daniel Lang