conventional block control questions

[msacco]

Although I've been collecting 0 gauge stuff for years and operating on simple loops, I'm now starting to wire a multi loop layout for block control.
I was wondering if this kind of thing is normal. I have an outer loop with an isolated blocked downgrade section. It's hooked up to a separate circuit on my new ZW with a reduced voltage setting. A loco will slowdown when it crosses over the block but it sort of surges up and down for a few sections.
I just realized that i'm carrying lit passenger cars and I think they are reading the higher voltage while the front of the train crosses over and enter the reduced voltage block.
Is this the reason and is it normal or is something up. I noticed on other blocks that I can cut power but if a lit car is still occupying a powered section of another block, the loco still get power even though the track under it is dead. Like the lit cars are carrying current all the way up to the loco.

Any help would be greatly appreciated.

Mike S.

[RRCharlie]

Mike;

Most passenger cars have pickup rollers on both trucks so when the car is straddling the gap in the third rail, current passes through the car and reenergizes the section you turned off.

Mel Hazen
Jacksonville, FL

[msacco]

Thanks Charlie,
Duh, I should have realized this. Electrical knowledge not exactly my strong point.
So I guess this is just part of normal operation then.

[Anonymous]

Mike

You can get around this problem using a SPDT relay. Have an approaching insulated center rail as long as the maximum train lenth. Use your spare ZW tap to trip the relay coil with an outside insulated rail. Use the relay contacts to break the center insulated section from the transformer and connect it to the ahead insulated block. This way the passenger cars will never bridge 2 blocks.You can drop the voltage with diodes in series,one in each direction.If you only run run train per loop all you then need is an outside insulated rail and a relay,you can drop the voltage right at the transformer using a diode array. Use 3 or 6 amp diodes or bridge rectifiers with the + and - connected and the ~ wired in series. Each pair of diodes will drop voltage .7 volts. Each rectifier will drop it by about a volt and a half.

Dale Hz

[lionelsoni]

The rectifier-diode scheme that Dale describes (or a resistor, like a prewar Lionel rheostat) is a much safer way to lower the voltage. The way you are doing it, a fault current is flowing through each of your passenger cars as it straddles the gap. This is the same current that would flow through a short-circuit to ground from a transformer set to a voltage that is the difference between the voltages on your two blocks. There is no circuit-breaker protection against this fault current in a ZW. I would fear for the internal wiring in the passenger cars if the train ever stopped over the gap.

(Your topic used the word "conventional". I assume that the ZW in question is a postwar one. I don't know what is in the new design.)

[msacco]

lionelsoni,
No, I'm using a modern ZW, and I've already had a train lay between sections with no problem. Is this an accident waiting to happen or is the new ZW, with I"m sure a more sensitive breaker, better equipped to handle this.
I don't really want to put anything in the line like a diode or such because I'm going to install rotary switches for all the blocks with the abilitly to assign any particular block to any of the 4 circuits on my ZW.
Any thoughts on this.

Thanks,
Mike S.

[Anonymous]

One way to break the current leakage across the blocks is to break the connection between the two rollers. I think each one connects to one bulb and there is a wire in the car connecting the 2 bulb sockets enabling either roller to power both bulbs. The downside of breaking the connection is that the individual lights will flicker whenever its roller is over an insulated section of a switch or crossover. You might try it with one car to start.

[lionelsoni]

Mike, I can't say what a newer ZW does in this situation. (I wish Lionel had not re-used the same designation for it. I have seen a lot of cunfusion on the forum as a result.)

A way around the two-pickup problem (if you want one) is to remove one of the pickups entirely. I have done this on some cars to reduce their rolling resistance. To solve the resulting flicker problem, put a small bridge rectifier feeding an electrolytic capacitor inside each car. I use the 1.4-ampere Radio Shack 276-1152, or its equivalent, and about 5000 microfarads, like the Radio Shack 272-1022.

You could also leave both pickups, but isolate them and provide a separate bridge rectifier for each one, both feeding the same capacitor and lamps. This wouldn't affect the rolling resistance of course, but it would keep the lights on when the car stops with one pickup off the rail.