Separate control for (2) post war lionel trains on connected inner and outer loops?

Connect all the outside rails (except control rails of turnouts) to the U terminal of the ZW.  Put gaps in the center rail to create blocks.  Wire the center rail of each block to the common terminal of a single-pole-double-throw switch.  Wire the other two terminals of each switch to the (for example) A and B outputs of the ZW.  Now each block can be assigned to either of those ZW controls.  If you create blocks cleverly, you should be able to get both trains onto the same loop while still controlled separately, and then maneuver one of them off to the other loop, to swap loops.

Do not try to run trains across a gap between blocks powered by different ZW outputs.  Unless the voltages are set exactly equal, a fault current will flow which is not protected against by the ZW circuit breaker.  This may at the least cause arcing and erosion of the pickups and at worst burn up wiring or your transformer.

Great!

Thanks! Bob... I knew it could be done.

Kurt

One other thing that Bob forgot to mention when going across two ZW outputs is run away trains if the voltages are much higher, it happened to me once.

Lee Fritz

Bob,

I think I remember you saying this once or twice before but I'm not sure I get it.

I have a new ZW and I have a loop which includesa Lionel trestle grade broken up into three blocks. I use one zw output set higher for the climb and another output set lower for level and the down. I have never experienced a problem except for passenger car lights with double pickups.

  I'm a bit confused because Lionel's original postwar directons always talked about using the zw's multiple outputs for ups and downs of a loco.

What gives?

Mike S.

I'm afraid that Lionel just got it wrong.  They did acknowledge the problem one time, in the fine print of the service manual for the KW transformer:  "Note that the circuit breaker does not protect binding post combinations A-B, B-D and C-U."  The A-B connection in this case is just like the A-B connection for a ZW, and other multiple-output transformers.

If the voltage difference is small and the train doesn't stop over the gaps, you can get away with this without starting a fire; and many operators do, without realizing how much luck has to do with it.  But the only point to doing it on a grade is deliberately to have substantially different voltages, which obviously increases the arcing and fire risk.

A safe way to use different voltages on a grade is to use a single transformer output, but to adjust the voltages by putting voltage dropping elements in series with the center-rail segments.  Back-to-back diodes can do this without sacrificing voltage regulation, so that different trains will see the same voltages.  You can also do it with rheostats; but heavier trains will see lower voltages than light ones.  It may be that someone at Lionel unwisely updated earlier, safe advice involving rheostats to later, unsafe advice when variable transformers became common.

Mike S.

I know about the old ZW transformers made until 1966 and as far as I know there is no article mentioning the ZW having a problem. There may be a problem with the newer type ZW's besides having external power sources. I think that Bob is staing a fact about another transformer that is not the same as a ZW.  The ZW is either 250 watts or 275 watts, with four control handles, the KW is a 190 watt smaller two train transformer with a single lever for both whistle outputs that is pushed one of two ways for the whistle to work.  The only thing like I mentioned before is watch out for the voltage settings, NO Sparks should occur!!    If you were to connect two ZW transformers together than maybe you will see sparks at crossovers, I don't recomend hooking two ZW's together.

Lee F.

I'm talking about virtually all Lionel multiple-output transformers, including the ZW and the Z.  They all share the same design flaw with the KW, which is the only one that Lionel seems to have acknowledged.

I cannot see how one could both set the voltages exactly the same, to eliminate fault currents and arcing, and yet set them different enough to get the advantage of higher voltage to go up the hill.

Actually using separate ZWs is significantly safer than using two outputs from the same ZW.  With two transformers, the fault current does pass through the circuit breakers.

I don't know guys I guess I've been lucky so far. I've been running for a little over 6 months or so and no problems. I was just running over this trestle loop and looked for sparks from the rollers where the voltage increase starts. Nothing. THe loco jerks a bit because it's obviously accelerating but no sparks that I can see.

Mike S.

Bob,

1)When you say that you don't see how somebody can set the voltages exactly the same or close to the same you seem to make an arguement without merit because there are such things as voltage meters for lower voltages available at electronics stores. Another way to set resonable voltages is to use a lighted car or locomotive in nuetral.

2)When you mention about fault currents you make me think of GFI(ground fault interruption devices) used on 120 volt outdoor equipment.  I have even talked with a friend of mine with Florida Power & Light, he is an electrical engineer, and the extremely low risk that a fault current may pose is not worth considering below 50 volts.

3)There are such things as eddy currents but we are not into electronics design here and don't have to worry about this.

Far as problems with Lionel ZW & Z type transformers NOT even Lionel is willing to address a problem via thier website.  There is one thing about older ZW transformers and that is the circuit breaker is slower to trip than the new transformers but this can be cured by buying circuit breakers or fuse holders for 32 volt fuses at 10 amps.  A word of caution on circuit breakers MATCH THE VOLTAGE as close as possible, DO NOT USE 120 volt circuit breakers as you will be sorry!!!

Lee F.

I do think there is some merit to the statement that, even with a voltmeter, neither I nor anyone else can set two voltages so that they are simultaneously the same, and yet one be higher than the other.

There are all kinds of faults in the world.  A ground fault is one.  A fault current is another.  GFIs protect against ground faults.  Circuit breakers protect against fault currents.  I was talking about the latter, which is the sort you would get if you stuck a paper clip into a two-wire outlet, or a wrench across your car battery's terminals, or a derailed train across your track.  A fault current that does not pass through a circuit breaker is not protected against by the circuit breaker, which is why it is unsafe to operate across blocks powered by different outputs of the same ZW or similar transformer.

Indeed there are such things as eddy currents; but I for one was not even thinking about them, much less worrying.

Any circuit breaker rated for the desired current and for a voltage at least as high as used in the circuit will work fine.  Higher voltage rating will not make anyone sorry.

Pbugos, yes, Radio Shack has a wide variety of SPDT switches.

What you say about the use of a paper clip is extremely dangerous, maybe to illustrate a point but not very practical to do. 

Circuit breakers are designed to protect against electrical overload, in otherwords if you try to use too many amps on one circuit the circuit breaker heats up inside and trips the circuit off to protect the wiring and the building.  A 15 amp 120 volt breaker will blow if used to power two 7 amp motors or appliances at the same time, reason behind this is that motors take 125% starting torque upon initial starting, even your ceiling fan does that.

As for the circuits on the ZW transformer a direct short should trip the circuit breaker regardless if using two controls.  Circuit breakers are rated by the metal strip's capacity to heat up at a certain wattage rating, most people assume that a 120 volt circuit breaker will protect on lower voltages but this is a TOTAL FALSEHOOD, because the metal strip inside will not heat up fast enuff to give any protection. Try to use an 18 volt light bulb on 120 volts and see how fast it blows-a fraction of a second.  Circuit breakers are best described as being rated more for watts than for amps like wire, so to say that a 120 volt breaker rated at 10 amps is 1200 watts, now what part of 1200 does 24 (24 being maximum voltage from most transformers) equal?  50 amps!!  WOW! what a fire or fried circuit board that will equall, eh Bob?  And like I keep saying use the proper rated circuit breaker or have a Bob Nelson fire.

While on the subject of the ZW's the worst that I have heard of or experianced was the roller wheels needing replacement from years of use or the diodes going bad and not operating the whistle control button or the circuit breaker not being fast enuff for the newer trains.

Like I may have mentioned before I have studied alot about both Industrial & Residential AC, also know about automotive DC current and circuit breakers

Lee

I did not intend that anyone should stick a paper clip into an outlet, nor a wrench across a car battery, nor derail a toy train.  I gave these as examples of fault currents, not as recommended recreations.

If I may use the expression, it is a TOTAL FALSEHOOD, that a closed circuit breaker cares what the line voltage is, any more than that a bird perched on a 7200-volt distribution line cares about that voltage.  Voltage is meaningful as a difference in electrical potential between two conductors; and both terminals of a closed circuit breaker are at the same potential, regardless of whether that potential is that of the earth (ground) or 25 volts or 7200 volts.  Only after the circuit breaker has detected a current greater than its rating (in amperes, not watts) does the voltage matter.  Then and only then are the two terminals of the circuit breaker at different potentials.  Then the voltage rating matters, since it determines whether the breaker can stand the arc that results from its opening.  Since a lower voltage produces less arcing than a higher, I promise that you will not have a "Bob Nelson" fire from using "too high" a voltage rating.

Here is a schematic of a ZW transformer:  http://pictures.olsenstoy.com/cd/transfmr/psvw1.pdf  Start at the B terminal and trace the circuit through to the C terminal.  It goes through however much of the secondary winding as is set between the B and C controls.  It does not go through the circuit breaker.  If you short B to C current will flow between them.  How much current depends on the open-circuit voltage set between them and the resistance of the rollers and wires involved.  The same is true of any pair of terminals A, B, C, and D.  Do not attempt to settle this question by setting two outputs to their highest and lowest (non-zero) voltages and connecting the two terminals together.  The circuit breaker will not trip.  The transformer will be ruined.  There may be a "Lee Fritz" fire.

phillyreading wrote:

As for the circuits on the ZW transformer a direct short should trip the circuit breaker regardless if using two controls.  Circuit breakers are rated by the metal strip's capacity to heat up at a certain wattage rating, most people assume that a 120 volt circuit breaker will protect on lower voltages but this is a TOTAL FALSEHOOD, because the metal strip inside will not heat up fast enuff to give any protection. Try to use an 18 volt light bulb on 120 volts and see how fast it blows-a fraction of a second.  Circuit breakers are best described as being rated more for watts than for amps like wire, so to say that a 120 volt breaker rated at 10 amps is 1200 watts, now what part of 1200 does 24 (24 being maximum voltage from most transformers) equal?  50 amps!!  WOW! what a fire or fried circuit board that will equall, eh Bob?  And like I keep saying use the proper rated circuit breaker or have a Bob Nelson fire. Like I may have mentioned before I have studied alot about both Industrial & Residential AC, also know about automotive DC current and circuit breakers Lee

You are wrong on this one Lee, and we have been through this before.  The correct way to calculate power is P=R*I^2 (resistance times current squared).  Simplified, this means the number of electrons passing a given point squared times the resistance they overcome. Because V=IR, voltage is often substituted into the power equation, giving the classic P=V*I.  The best illustration of this is the world of microprocessors.  As microprocessors have shrunk in physical size, the voltage requirements have gone down.  Resistance across each cell has also decreased.  But the heat production has gone up because the currents have gone up.  From our equation, because heat and power are related to the square of the current, we can see why.

But if you still don't believe me, buy some 1 (you can use 3 amp if you have a larger transformer) amp in-line fuses (I think you can still get them) rated for both 125 volts and for 18 volts.  Wire them up one at a time to your train track, and create a short circuit on the track with about 12-16 volts.  I defy you to tell which fuse blew faster.

The voltage rating of a fuse or circuit breaker is used to design the components to prevent arcing and consequent premature opening at the circuit operating voltage.  It is the resistance of the metal strip and the circuit current going through it that causes the breaker or fuse to open.  Therefore, the current rating of the breaker or fuse is determined by the resistance of the metal strip.

The reason why the 18 volt bulb blows on 120 volts is that the resistance of the bulb is intentionally designed to be much less than a 120 volt bulb.  Say it takes 1 amp to produce the desired brightness from a given filament.  For the 18 volt bulb, I want the resistance to be 18 ohms when white hot.  Similarly, I want the 120 volt bulb to have 120 ohms when white hot.  So when I put 120 volts across the 18 volt bulb, I now have over 6 amps passing through a filament designed for 1 amp.  The 120 volt bulb has a much longer filament (more resistance), which is why very tiny light bulbs have to have low voltage ratings.  There is simply not enough physical room to get a long thin strand (higher resistance) inside the vacuum bulb. 

Postwar transformers are pretty rugged beasts, and can take a lot of overloading and abuse.  The multi-control transformers (KW and ZW especially) use the same transformer windings for both throttles.  Each throttle has its own contactor/roller.  But when your 2 center rollers on the engine span the 2 control sections, there is a direct short between those 2 throttle contactors on the winding.  Basically, you have shorted out a portion of the transformer winding.  The voltage applied to the short is proportional to the distance between the 2 throttle contactors.  Since Lionel did not put a circuit breaker in each throttle leg, but rather in the common return leg, there is no current limiting on the short.  So the greater the disparity in the throttle settings, the greater this fault current will be.  If the train derails or stops with the center rollers bridging the 2 sections, this fault current can go on long enough to start creating real problems.  Problems are likely to be arcing at both the pickup rollers and the throttle contactors, which will if repeated over time, cause premature wear on both.

If you use separate transformers for the 2 trains, then the fault current does go through the built-in circuit breakers, and is limited by them.  But the best solution is to put circuit breakers or current limiters in each transformer output lead.

just my experiences and electrical engineering training

Fred W

With all this said...

I will be installing these blocks with DTDP (double throw-double pull) switches, so I can power my LEDs seperately from from the track voltage, so the LEDs will be illuminated even without track voltage.  I will run the block power through a fuse block and then to each track block.

1.  Should the DPDT switches match line voltage 18v or 120v, and what size amp rating am I looking for?

2.  The new ZW transformers talk about their protection at 10.5A.  Is this true of the earlier PW ZW? What voltage and amp rating should I be looking for in a fuse?

Kurt

The switches will probably be rated for 120 volts AC or, if they are intended for automobiles, 12 volts DC.  The AC switch rating is well above the voltage you are using, and therefore the switches should be acceptable.  DC is much harder on a switch than AC; so, even though your AC voltage is half-again higher than the 12-volt DC rating, I would expect those switches to work just fine in an AC circuit.

The old ZWs had 15-ampere circuit breakers.