Separate transformer for switches

Yes you can hook the common of both transformers together.  But you must phase the transformers.  When you have them hooked up common to common, set each with an output voltage, and touch the other outputs together. If the produce a large spark, unplug one of them and reverse the plug in the socket and touch again.  If they are phased they should not spark or barely spark compared to being un- phased.

You did not state the make of your switches, the type of transformer or its wattage.  I do not know if you need 18 volts to operate the switches.  If they are Lionel 1122 or such usually need 14v  and have two lights on the controller and one light on the switch they will constantly draw 4 or 5 watts times 9.  Additional wattage will be drawn momentarily when switching.   These type of switches will add up and you are wise to get a separate switch transformer.  I run Marx 1590 switches, 31 of them and they do not have lights and draw zero wattage unless switching.  I use a small 40 transformer that outputs 14 volts with no issues.

Charlie

Step one when using multiple transformers, even if you don't initially need to, is always to "phase" them.

The process is simple, and has been discussed here hundreds of times. You can do a search for "phasing transformers." The process ensures that the high peaks and low peaks of alternating current from multiple sources coincide, and do not fight each other.

In your case, one side of the switch motor 18Vac output needs to be connected to the outside rail (RETURN) supply of the traction transformer. (This transformer is the one you will use to make the trains go.)  The other side of the 18Vac gets connected to the switch motor pins (the HOT side).

Once the transformers are in phase, you will never get a short or heavy spark, or any other electrical problem related to the fact that you are using more than one transformer.

If you are using a traditional transformer on a relatively small layout, you can also consider using one output from a multiple-output transformer, such as the old ZW type. In that way, you needn't worry about phasing, because all the outputs are in phase by design.

Be sure to equip the switches with lamps that can handle 18 Volts, or you will get overheated and melted lanterns. if you are using old tubular switches, you can equip them with 24-volt lamps and not worry about the heat. Type 1437 draws 0.06 Amp, and is rated for 24-28 Volts.

Thanks for the responses!! The switches are old o72 and o22. The transformer for the trains is a KW 190 watt. I know I can run everything off this but was just trying not draw everything from it. I have an old 1033 I was gonna power the switches with. 

which leads my next question, I ran the meter on the terminals on the 1033, but what terminal is the common, that would be paired with the (U) on the KW? Thanks for all your help!

On a 1033, the common post is the A post and the "hot" side is the U post. BUT...if you intend only to use the 1033 for the switch motors, and not for any other track-associated loads, then it doesn't matter which post, A or U, you assign as the common. 

(The letter designations on transformers are sort of ambiguous, and arbitrary. They vary, as you have seen, from one model to another. Lionel didn't really have a logical system.  The designations are put there to allow a kid to hook up his trains to a single transformer without a lot of head scratching. Remember that in talking about outputs from A-C toy train transformers, there is no "hot" or "ground" or "return" until the user assigns those designations by actually fastening wires and devices to the posts. One man's hot is another man's return.)

Here's the procedure:

Connect the U from your KW to the U from your 1033.  Plug them both in, and set their outputs at the same voltage, using a voltmeter. 

Using your voltmeter, take one test lead and touch it to the A post on the KW, and the other test lead and touch the A post on the 1033. 

You are looking for a reading close to zero volts, if the transformers are in phase. 

If you get a reading that is close to the sum of the individual output voltages, they are not in phase.

If that is the result, reverse the line cord of one transformer, and then mark the plugs so that you will always plug them in the same way in the future.

If you have 9 switches , you have 18 bulbs at 3 or 4 watts that's at least 36 whtts drawing on your transformer, if you keep your voltage at 18V the bulbs get very hot...Try using a higher watt bulb like 24 watts they will stay cooler.

"Try using a higher watt bulb like 24 watts they will stay cooler."

Correct, but I think you mean "volts" not "watts."

In a previous post, I suggested the type 1437, rated at 24 Volts.  One of them draws 0.06 amps. Multiply the current draw times the voltage, and you'll get (roughly) the power in Watts.  .06 A x 18 V = 1.08 W.

outlet saver

The above product, generally intended to allow "just one more" device to be added to an outlet strip, is useful as a permanent way to ensure that two transformers are always plugged in the correct way.  You can find them for less money; this is just an example.

Incandescent bulbs behave like ballast resistors. They draw near the same current regardless of voltage. Switching to an LED bulb would be better.

I don't think anyone offered an opinion that would dispute that. What we calculated was the wattage which DOES vary with voltage, assuming the same current draw, as you pointed out. Power = Voltage times Current

U on a KW should always be deemed to be ground, as with ZW, VW, & Z4000.  On MOST BUT NOT ALL transformers, U is common and A,B,C,D should be deemed hot and used for center rail.  There is at least one exception in the Lionel line, but I don't recall which.

There are LEDs bulbs available that are direct replacements for the incandescents in 022 switches & controllers.  Run nice and cool, and use little powewr.  The standard 022 bulbs are deemed to draw 5 watts, per very old Lionel literature

Thanks for all the info guys i appreciate it. do you know the model no. of the LED replacement bulbs?  

Chris

"There is at least one exception in the Lionel line, but I don't recall which."

The 1033, for one.

Chris, look for Town & Country Hobbies.  They used to come to the York show.