U terminal for Common, or A,B as common

[stuartmit]

illustrations from Lional indicate that transformers with more than one throttle would use the U terminal as a common ground, connecting to the running rails. Transformers with only one variable throttle connect, the U terminal to the center rail, and then show the a or B terminal connected to the running rails. The back of the RW transformer shows that if the a terminal is connected to the running rails, you get a 19 V fixed tap by connecting D terminal as fixed voltage, which would be good for accessories, if a little on the high side.

If I phased a V in parallel with an RW, and if I connected the U terminal to the running rails and connected the a terminal or the A terminal of the RW to the U terminal of the V, would I be able and safe to connect to connect the U of the RW to the center rail, and  use the D terminal of the RW as a fixed voltage source for 022 switches?

[smokey1]

I may be wrong here but if memory serves me right, Lionel reversed the lettering on some single throdel transformers. I alway use U for outside and A-B-C-D for you middle rails. But from my understanding there are transformers lettered backwards, so for that reason if I'm not familiar with the transformer I will put leads from my tester on U of both transformer to see if I get a showing of voltage, if so then I know the other is lettered backwards. I have come across a ZW backwards, which tells me someone rewired it wrong.

[pennytrains]

Lionel also used "X" on some "Multivolt" transformers and the throttle lever itself on others had a threaded nut for a wire.  I'm talking about the old A to Z types with metal voltage taps on top btw, not the postwar TrainMasters.  But it shows that Lionel wasn't always consistent.

[stuartmit]

I have a copy of the manual Operating Lionel Trains 1955. In it, there is info on two pages relating here. On a page early in the book which shows the terminals of 1033, KW, ZW, RW, and TW, the connections of the (multi throttle) KW, and ZW show U connected to the running rails; all the others which only have a single throttle show U connected to the center rail.  Further back in the book, in a section covering "common ground" connections, and including older transformers like V and Z, charts afre also organized in a way which seems to indicate the dichotomy detailed above. So it seems the difference is purposeful on the part of the electrical engineering and design staff.

[ADCX Rob]

stuartmit

illustrations from Lional indicate that transformers with more than one throttle would use the U terminal as a common ground, connecting to the running rails. Transformers with only one variable throttle connect, the U terminal to the center rail, and then show the a or B terminal connected to the running rails...

This IS  the convention, a study of the service documents with the transformer schematics will confirm it.

stuartmit

...would I be able and safe to connect to connect the U of the RW to the center rail, and  use the D terminal of the RW as a fixed voltage source for 022 switches?

Yes, but the usable ~75 watts output of the RW will be used up quickly as just the bulbs on a pair of 022 switches & controllers will draw 10-12 watts, before you even throw a switch.

[lionelsoni]

Two Lionel-transformer ideosyncrasies that may be useful to know:

o  The Lionel schematic diagrams show the whistle diodes reversed from their actual polarity.

o  "Phasing" is desirable only between transformers that feed adjacent track blocks.  Otherwise, having transformers out-of-phase with each other can be used to decrease voltage drop in the layout common.

[Swiss-Colorado-Lines]

All of the above is true!

An invaluable resource is " The Big Book of Lionel" by Robert Schleicher. There is a table on pages 80 and 81 that breaks down all the various transformer posts on different models. 

Useful for postwar transformers!

Paul

[stuartmit]

but my question is as follows. Can I connect  A from RW to U from SW to achieve common ground with  two transformers?

I  am building a traditionally wired layout based on Seneca Falls layout in CTT several years ago. My plan has  it divided into 3 major sections, each of which has 2 or three toggle switch controlled blocks.  I have an SW with two throttles which are variable, and it also has a 14 volt fixed tap and a 19 volt fixed tap. The two throttles will control two major routes on the track plan, which are essentially 2 pairs of passing tracks. So with some care and practice, you can run two trains in opposite directions simultaneously. Further, to the left of the original plan is an oval with a siding which can operate without affecting the two trains running in opposite directions. For the oval, I plan to use an RW. The RW allows D and A to give fixed voltage, with A as ground, U connected to center rail, and D as fixed for switches. I Plan to use U from the SW to common and A and D of the SW connections as variable speed control for level sections where trains run in opposite directions with the B and C fixed taps for up and down hill sections to help climb or descend in a manageable fashion.    

Is this electrically sound? I believe there is no reason I can't connect the U terminal of the SW to the A terminal of the RW.

   The total input wattage is 240 watts (so perhaps 170 watts out?)  tosupply perhaps 3 locomotives, but most likely 2 (how many things can you monitor at once?) I am prepared to omit lamps in switches--too much wattage use. My only distrust of the arrangement is that the throttles of the SW operate in opposite directions. In an urgent moment, I might do exactly the opposite of what I intend.

I feel I need three throttles and three fixed taps. I guess I could use 3 RW's which I do have, but that would take up more panel space. So I would rather not.

[ADCX Rob]

stuartmit

...but my question is as follows. Can I connect  A from RW to U from SW to achieve common ground with  two transformers?

Yes.