Power Question: Follow-up

[traindaddy1]

This is a follow-up to my question posted on 6/9 that was answered so well by Leonard and Dale Hz. Many thanks to you.

I have decided to have the ZW overhauled by a Lionel Authorized Service Center (Mainly because this "older" guy is somewhat electrically inept)

I have hooked up a small Bachmann HO power pack to my accessories.

Question: When I bring the ZW home, do you think that I can resume using three terminals to run three separate lines and the 4th for accessories or would you suggest that, as long as it is working, leave the Power Pack hooked up, thus leaving the unused terminal for a possible future separate line?

Side note: The original ZW instruction sheet says that the two outer terminals are for trains and the inner terminals are for accessories. Do you think there is any harm in using an inner terminal to run a train?

Many thanks,

[lionelsoni]

As long as you don't need the whistle control, you can run a train on any of the terminals. Just don't run a train between blocks powered from different terminals, whether inner or outer or any combination.

[Anonymous]

The 61 consumer catalog shows a ZW running three trains while the copy reads:

"Four variable voltage circuits will operate up to four different train sets simultaneously"

Just below this on the same page are the external breaker/direction control button that could be added (along with sound activation buttons) to allow full control of trains on the inner terminals.

[traindaddy1]

Bob-Chuck: Many thanks for the info.

[rha90272]

QUOTE: Originally posted by lionelsoni

As long as you don't need the whistle control, you can run a train on any of the terminals. Just don't run a train between blocks powered from different terminals, whether inner or outer or any combination.

Now you've got me worried: I'm designing a setup with four separate 3-rail O-gauge blocks, each controlled by one of the four ZW transformer terminals. I hope to be able to have a train go across blocks (separated of course by a fiber center pin), by merely roughly equalizing the power in the two blocks as it crosses. Is there danger in this?
Bob Anderson

[lionelsoni]

I'm afraid so. Unless the controls are set exactly the same, there will be a voltage across the gap. When the locomotive's pickups (or the dual pickups of a passenger car) bridge the gap, a fault current will flow, much the same as a short circuit on a single transformer set to the voltage difference across the gap. The ZW has only a single circuit breaker; and this particular fault current does not flow through it. (I'm assuming you have a postwar ZW.) If the train is moving fast enough and the voltage difference is small enough, you can get away with no more than some arcing and, if you're lucky, not high enough voltage transients to damage modern train electronics. However, if the train should stall over the gap unnoticed, you can burn up your transformer or wiring or both.

Individual circuit breakers or fuses are a good idea. But the cleanest way to fix the problem is to use, for example, an SPDT switch for each block to assign it to one of the transformer outputs. Then each train can stay with the same transformer output as it moves from block to block anywhere on the layout. A center-off switch allows you to shut off a block. And you can afford to make more and smaller blocks, since each one needs only one inexpensive switch, not another transformer.

[rha90272]

Bob - Thanks for your very thorough answer. I have a postwar ZW, and only postwar (1945-59) locomotives with no electronics. I was going by the statement in the ZW instructions, "When crossing from one loop to another it is important that the voltages supplied to the inner and the outer loops are approximately equal. This is done by setting both throttles at the same point. Unless this is done, the contact rollers of the locomotive crossing the insulating pins which separate the two circuits will bridge two dissimilar voltages causing a short circuit and stopping the train." I assume postwar non-electronic locomotives are a bit more robust in handling this problem, but your warning is important if I want to add electronic-control locos. The setup I proposed has the advantage of independent speed control of multiple non-electronic (and non-TMCC) operating locomotives, while also allowing them to occasionally cross over onto each other's blocks. I would lose that capability with the scheme you propose.
Bob A.

[Anonymous]

Bob A

You can get around the problem by using 2 DPDT relays and an insulated center rail buffer between the 2 blocks as long as the maximum train lenth you run. Past the 2 ends of the buffer you can install short outside insulated rails to work the relay coils. Wire the power from each transformer tap to the NC and NO contact of one of the relays and run the center rail buffer to the common contact blade.Wire this relay to be self latching and wire the other to cancel it. As the train passes through the block the relays will switch the power as the complete train passes through the block.The system is bi directional and will work as long as the trains are not too close to eachother.

Dale Hz

[lionelsoni]

Bob, note that the instructions do not say what happens after "stopping the train". That is when the transformer starts to burn. I have a couple of the actual transformers out of old model Z transformers, very similar electrically to the ZW, which clearly have been burned in that way.

You need not lose the capability to do everything you want with the scheme I proposed. You just need as many switch positions as you have transformer outputs. For many people, two is enough; but the idea can be easily expanded to many more. One way is to use a rotary switch. Another is to use multiple toggle switches. For example, with an SPDT and a DPDT in each block, you can switch the block among 4 transformer outputs.

[rha90272]

Bob N - Thanks for the clarification. I misinterpreted your earlier suggestion. This discussion thread (including Dale H's response) has been very useful.
Bob A.

[traindaddy1]

Boy Oh Boy! I got to tell you guys. When I posted the topic, I never expected to open quite a discussion. I, as always, value the information that I receive from reading the responses. Keep them coming, and again, many thanks for taking the time.