How to move between 2 transformers

@Don Baird posted:

I am using a ZW to operate two mainlines on the lower level of the layout. A shorter run on the upper level is powered by a 1033.  Transformers are phased and share a common ground. The postwar locomotives have magnetraction and I’m using tubular track

There is to be a 3%  grade connecting the  two. Trains will be running both ways on the same track. Two questions:

1. Should the transition between transformers be at the top or bottom of the grade?  I’m thinking top in order to have the superior power of the ZW available for the uphill climb.

2.  What do I need at the transition point?  More than just an insulated center rail?  If only that locomotives will have a pick up on each side at once

Well, ISTM you have several issues you may or may not choose to address:

1. First, I don't think it will matter where the transition is placed (and yes, an insulated pin in the center rail is all you'll need between the blocks, as long as the outer rails are phased, with a common ground).  It's not the *power rating* of the transformer that determines the engine's speed, it's the *voltage* set by the throttle, and unless you are running your 1033 at the ragged edge of its capabilities, you shouldn't notice any appreciable difference, assuming both are set to drive a given engine at the same level speed.

2. Similarly, as long as the transformers are properly phased, a momentary bridge across the insulated pin will do no damage.

3. However, at a 3% grade, you will have a significant slowdown ascending and a significant speedup descending the slope. Using power resistors between the transformer powering the upper loop and the center rail of an isolated section encompassing the entire slope (with insulated pins at *both* ends), it is relatively easy to wire a section that will  slow down your consist while descending the slope (or speed it up if the resistors are between the lower track and its transformer, with full power provided to the slope), but I know of no configuration that will do both at the same time. IOW, you can insert a power resistor between the transformer and the descending slope section to slow any descending train . . . but it will *also* slow down any *ascending* train as well, adding to the effects of gravity.

4. However, if you can provide *two* slopes, one in each direction, you can use power resistors to reduce the voltage on the descending slope, and allow full voltage on the ascending slope with reduced voltage on the higher track, and wire the ascending slope as detailed above.

5. I'm assuming for the responses above you are running conventional -- if you are instead using command control, you should be able to power up *all* the track as usual, and let the engine's speed control use what power it needs to maintain speed, with the single transition positioned anywhere on the slope.

Your phasing should be fine with the ZW "U" common posts phased to the 1033 "A" common post. Transitioning the blocks on two sides of a center rail fiber pin should be OK with the throttles set to a similar voltage.

The real problem comes in when transitioning two blocks run by different handles of the ZW - this creates a brief but potentially very high amperage short between different points on the secondary if the handles are at different settings. There is no circuit breaker in play with this type of short. I have measured 30+ amps close to the ZW with just a 6-7 volt difference.

Thanks to both of you.  

Rob, Re:  “Transitioning the blocks on two sides of a center rail fiber pin should be OK with the throttles set to a similar voltage.”

similar voltage may be the issue. My thought is to have 5 or 6 lengths of flat track on the second level before the transition. I’m hoping this will give me ample time to lower the voltage from the uphill climb and lower it further for the downhill run.

Steve:  As I have planned my layout I have no idea where I would find room for a second run of tracks for the hill. My heaviest locomotive is my post-war Lionel Fairbanks Morse Diesel. I also run a couple of postwar steamers. I’m hoping that I can control downhill speed by reducing the voltage at the transformer (and by forbidding my grandkids from going down the hill.)

Ive learned some electronics while working on this project, but have only a vague idea of what a “resister” is, and no idea whatsoever how to install or use one.
Don

@Don Baird posted:

Ive learned some electronics while working on this project, but have only a vague idea of what a “resister” is, and no idea whatsoever how to install or use one.

A resistor is an electronic component that has a known resistance to the flow of electricity (measured in "ohms") which, when inserted in series with a load (think, a light bulb or toy train engine), will split the power supply voltage (and power) between that load and resistor, effectively reducing the voltage 'seen' by the load, similar in effect to physically reducing the throttle setting. Physically, component resistors are typically tubular or rectangular components with a wire at each end, and the power they can handle depends on both the size and materials used to construct them:

As an example, the video below briefly points out (about 50 seconds in) a bundle of beige, boxy power resistors (rated at 10 watts each) which I used to trickle a small voltage into the "stop" section of track, to keep the stopped engine's e-unit from reversing direction while still keeping the voltage low enough to arrest motion:

Interesting. Is it possible to have the resisters function only when a collision is threatened?

Will the same principal work if the two trains are on separate lines with separate power sources?

This is a new concept to me. transitioning between throttles.  I have always used blocks assigned to a throttle by a toggle switch and that throttle runs the train no matter where it is on the layout.  Never had the need to move from one block to the next an assign a different throttle to it.  Where would this be a plus in train operation?  Is this an issue for the larger layouts?

CALNNC,

The "Cab control" wiring you describe used to be the standard way to go before the days of digital train control.

For those not familiar with it, in its simplest form,  it involved having two power sources and any number of isolated blocks of track. A DPDT center-off toggle switch was connected to each block.

The two power sources were connected to the track through each of the toggle switches. The switches were wired so that if the switch was "up", power supply #1 was connected to that block. If "down", power supply #2 was connected. The middle position turned all power off to that block.

For simple layouts with 2 loops, each loop would be considered a block and be electrically isolated from each other and connected to a toggle switch.

In normal operation, loop A toggle would be up and loop B toggle would be down, providing independent train control with each loop connected to a different power supply.

When you wanted to travel between loops, put both switches in the same position so both would be connected to the same voltage source. Then there would be no bridging between power supplies as the train passed from one loop to the other.

Once the train was across to the other loop, the toggles would be reset for independent control of the loops.

It really doesn't complicate wiring that much for a small layout and you never have to worry about one power supply interfering with the other.

It also cures the problem with the ZW described by Rob when different handles are the two power supplies.

For very large layouts with multiple power supplies, rotary switches with many positions were used to assign a power supply to a block.

The arrival of TMCC and DCS sure made life easier for multiple train control.

Jim

@Don Baird posted:

Rob, Re:  “Transitioning the blocks on two sides of a center rail fiber pin should be OK with the throttles set to a similar voltage.”

similar voltage may be the issue…

You are over-thinking this.

If you transition from one transformer to another and they are NOT set to the same voltage, it’s no big deal. If the transformer we are going TO is set higher, the train will speed up a little If it’s set lower, it will slow down a little.

That’s it.

@Don Baird posted:

Interesting. Is it possible to have the resisters function only when a collision is threatened?

Will the same principal work if the two trains are on separate lines with separate power sources?

Well, the missing factor on collision avoidance is, "How do you know a collision is imminent?" , or more broadly, "Where are the trains?" You *can* use the same sensing and control/stop design in a linear fashion (e.g., divide a loop into sequential segments, and wire them to cut off (or reduce, with resistors) the power to the section behind the one being transitioned by a train. That is, when a train first enters a section, any train entering the preceding section will be stopped or slowed until the first train exits the section it was transitioning.

On the second question, if you are using a relay triggered by an isolated section, I see no reason why the relay contacts can't control an independently-powered separate loop (perhaps at an electrically-isolated track crossing on the two separate loops).

For both of the above, I'd want to sketch it out and think a bit before expressing absolute certainty, but my initial reaction is that isolated sections, relays and resistors can be used to create a degree of block control and automatic operation. However, if you really want a finer-grade of control, you might want to just jump into the current century and explore modern command control, with sensors and more modern electronics.