AC and DC Lionel trains on common tracks with two transformers

Charlie....I removed the links you had in your post above because they were being hosted on OGR.  I also deleted the original in the 2015 thread here on the forum.  These links, because they were copied directly out of the book, violated copyright.  Keep in mind, just because one purchases an old book from decades ago, copying and posting material from it is a copyright violation.

Hopefully the more electronically knowledgeable will chime in, but my answer would be no. If you have a whistling tender or a postwar unit with a horn, it would continuously go if you tried what you are saying. Also, if you have both AC and DC power on the rails at the same time, I wonder what the impact would be on a postwar engine, since they can run on both DC and AC. I suspect it would be like having two AC transformers hooked up to the same track , you would end up with speed that would be basically a function of whether the waveforms were in phase or not, could be a sum of the two or the difference between them (if it is DC and ac, might be a bit different in terms of net value)..the upshot would be you wouldn't have speed control per se unless you changed the voltage on both transformers simultaneously . Here i am talking a single post war engine using two transformers to describe its behavior.

The DC motor would do the same thing, it would be some kind of combination of the two voltages. DC motors can run on AC but they don't operate properly, they heat up (and can easily burn out) trying to reverse 60 times a second.

In other words, it isn't like a (bad) analogy of having two different frequency signals on the same track, it isn't the AC engine only reading the AC power, and the DC engine doesn't read the DC power level only, it will be combined in both cases.

There may be a way to make this work by modifying the engines to read only DC or AC via a filter circuit that would allow only DC or AC to get through, I suspect that is what Gilbert did (GRJ might know of something), but it would not work unmodified I am pretty sure, even with my knowledge (I might have grown up in a family with EE's, I am not one of them

What Gilbert did in postwar S gauge was build two different types of engines. The most common were those with series universal motors. These work equally well with either AC or DC track power. They have a F-N-R-N reversing unit that determines the direction of engine travel, similar to the Lionel E unit. The engine can also be locked in a single direction. Beginning in 1947, ending in 1950, Gilbert made some S gauge engines with permanent magnet DC motors. These required DC track power for operation and a DPDT switch for direction control. Both could be run on the same track at the same time as long as the track power was DC. It would be a bad idea to connect both a DC power pack and an AC transformer to the track. Gilbert never made an engine that would only run on AC track power, every engine Gilbert made will run on DC.

I will leave it to the Lionel experts to discuss the O gauge products.

@AmFlyer posted:

What Gilbert did in postwar S gauge was build two different types of engines. The most common were those with series universal motors. These work equally well with either AC or DC track power. They have a F-N-R-N reversing unit that determines the direction of engine travel, similar to the Lionel E unit. The engine can also be locked in a single direction. Beginning in 1947, ending in 1950, Gilbert made some S gauge engines with permanent magnet DC motors. These required DC track power for operation and a DPDT switch for direction control. Both could be run on the same track at the same time as long as the track power was DC. It would be a bad idea to connect both a DC power pack and an AC transformer to the track. Gilbert never made an engine that would only run on AC track power, every engine Gilbert made will run on DC.

I will leave it to the Lionel experts to discuss the O gauge products.

Thanks, Tom, that makes sense. So basically the two engines would have the same speed, but you could change direction on one engine via the usual cut off button, the other engine would change direction via polarity . Raises an interesting question, if you reversed the polarity wouldn't that cause the engine with the reversing unit to run in reverse as well, since it would by bypassing the reverser basically....(and this is just my curiousity)?

The engine with the universal motor does not care what rail is what polarity when DC powered. The only thing that changes the direction of that engine is the reverse unit stepping when the power is interrupted and then reapplied.

The Gilbert reverse unit changes the direction of current flow through the field winding in relation to the armature windings to reverse the rotation direction of the armature.

The desirable thing to do is to get modern equipment with remote control that can have multiple trains running on the same track. You are asking what is possible, and that is something else. You "could" put one transformer on the center rail and the right outside rail and put the other transformer on the center rail and the left outside rail. This would require all axels to be insulated, all outside rails to be isolated, accessories could no longer be triggered by insulated track, switches might need to be rebuilt, and no reverse loops. It would be super expensive, time consuming, and difficult to operate. In other words, don't go for what is possible, go for what is desirable.

There's always another way.  But the other way may not be practical, just theoretically possible.

Using locos that can run on DC, you could feed two DC supplies to the track, each through its own diode, and both returning through the outside rails. The locos would need to have their own matching diodes in their respective motor circuits.   The + facing diode supply would feed the + loco through the center rail, and the - facing diode would feed the - locomotive

This method would not require rebuilding the three-rail track.

I think dead-rail is the best rail. Complete independent control of many locos and no track electrical worries.

If you're willing to live without the whistles, AC motors (also called universal motors) will also run on DC.  The E-units would not work but installing a bridge rectifier would allow the AC motors to reverse with a reversal in the DC current direction.   See this thread:

https://ogrforum.com/...4#157547622929387854

The number of rails has nothing to do with whether the current is AC or DC.  Three-rail just avoids the headaches of reverse loops, wyes, turntables, etc. regardless of whether the electricity is AC or DC.

@bigkid posted:

Raises an interesting question, if you reversed the polarity wouldn't that cause the engine with the reversing unit to run in reverse as well, since it would by bypassing the reverser basically....(and this is just my curiousity)?

No.

The way to reverse a motor is to change the RELATIONSHIP between the current through the armature and the polarity of the magnetic field of the field.

In a can motor, the field is a fixed magnet so its magnetic field is constant and in the same direction. The Gilbert DC motor has a fixed magnet for the field, similar to a can motor. That's why reversing the polarity of the voltage going to the armature reverses the motor direction. That's also why it cannot operate on AC - the motor would be trying to reverse direction 60 times a second.

In a universal motor, AKA a pullmore motor, AKA a series wound motor, the E-unit reverses the direction of current through the armature while keeping the field current going the same direction, regardless of armature current direction.

Running on AC, the current direction changes 60 times a second, but the relative direction of the current in the armature stays the same as the field, until the E-unit reverses the armature current.

Radio Roy',  I want to run a British DC O Gauge  2 -rl, loco on 3-rl track.  If I apply a positive lead and a negative lead to the outside rails, will the loco run?

Thanks in advance...

@Quarter Gauger 48 posted:

Radio Roy',  I want to run a British DC O Gauge  2 -rl, loco on 3-rl track.  If I apply a positive lead and a negative lead to the outside rails, will the loco run?

Thanks in advance...

It depends on the brand of track and how it is installed/wired.

Traditional three rail track has both outside rails electrically connected to each other, so that would subject your DC power supply to a short circuit.

Check that first. If the outside rails are not electrically connected to each other, your scheme will be fine.

Gargraves and maybe Atlas have all three rails isolated, but it depends on how they are wired after installing them.

Thanks Roy, I use Atlas track.  They would be wired only with a DC LOAD, on the outside rails.  No AC will be on the tracks at all.... So, the Dc Loco should run fine'....