I came to OO from HO, not from Lionel. All of my locomotives until roughly five years ago were permag, including my one Lionel 4-6-4 which a prior owner converted to a permag DC motor and my two S-C 4-6-0 drives.

When I finally purchased a locomotive with an S-C Universal motor on it I will admit it, I found those four wires out the back of the motor intimidating! I located the wiring diagrams, and while I think I might have actually got the motor that seemed to be in the best shape (this one in the photo) wired up correctly, I could not get it to do more than hum. It was a bit frustrating. I moved on to other projects.

But, I knew I had seen these models run with the original motors, and S-C shipped lots of these motors so it had to be me not the motor. Fortunately, Dick Gresham sensed from the other post the info I really needed and provided it–how to wire up a Universal motor to bench test it. I think others out there need this basic rundown as well:

Scale-Craft 12V AC-DC motor – I have a caution tag that I think came with this motor. It says “This universal motor operates on 12 volts A. C. or 9 volts D. C. Oil motor bearing holes with fine motor oil before using.” I use the following procedure to bench test the motor. First I check that the coil wire is continuous by using an Ohm meter. You could also use a continuity tester or a test light, or just omit this step. Then I twist the end of one coil lead to the end of one brush lead. Next twist the end of the other coil lead to the other brush lead. Now you should have two wires to hook up to a DC or AC power supply. I apply only a few a few volts to the motor initially, and turn the armature manually if the motor doesn’t start immediately. I’ve run several of these motors in this manner…. Some of the motors seem to be sluggish. I surmise that the grease in the transmission has dried up, and needs to be replaced.

So the key is that you need to wire one side of the coil to one brush and the other side of the coil to the other brush. THEN you have two wires to connect to your power pack. Hooking up the wires in this manner I applied power from the little HO train set transformer on my workbench and the motor would only hum. I took it over to the layout, and touched the leads to the track leads, and it would run! I don’t have a meter to see how many amps it is drawing, but it needed more for sure than the little transformer put out.

On DC the motor runs the same direction no matter what the polarity is. The way to reverse the motor is to reverse the coil wires, to hook them electrically to the opposite brush. Then the motor runs the opposite direction. Which now makes the manual reverser that S-C shipped with models make lots of sense, as to reverse the model you have to manually switch the relationship of the coil wires to the brush wires.

The other thing that now makes sense is that the model runs on AC exactly the same way as in DC, with the manual reverse. I hooked the motor up to the transformer I use with the very little O-27 I have (mostly Marx) and it ran like a devil! I am sure it is kicking out more amps than what I use for DC models, maybe too many really. But the bottom line is if you normally run Lionel OO on AC you can safely plop a Scale-Craft locomotive with the manual reverse and the Universal motor right down on the rails just like a two rail Lionel 4-6-4 and it should run fine. It will run on AC or DC.

But note: if the locomotive is set up so that the Universal motor is wired with a rectifier this model is only for operation on D.C. Again, as S-C noted in their 1941 catalog, “It must be remembered, however, that the bridge rectifier cannot be used with alternating current. It is made for direct current only, and will be burned out in a few moments if used with an alternating current.”

The whole AC/DC problem came up because while S-C introduced their line as DC in 1937, Lionel made their models in AC in 1938. The S-C DC motor cannot be operated on AC. Their solution was the Universal motor, which can operate equally well on AC or DC. [UPDATE: But, it should be noted, this was not a new solution, as I see in the 1936 Nason catalog their motor was also AC/DC and was set up to be used with a hand reverse as well–S-C was the one who tried to go against the grain with the DC motor].

Dick did also have some very interesting notes on the early Scale-Craft DC motor that I would like to share as well.

Scale-Craft 24V DC motor – I only have one extra 24V DC motor. Initially it would not run. There is a Bakelite brush holder attached to the motor with four brass screws. I removed the brush holder and discovered one brush spring was badly bent and useless. I think the spring came into contact with the commutator when the motor was running. There is a steel ball in the brush holder to reduce friction on the armature shaft. I wasn’t expecting a steel ball. It fell out, and I had to retrieve it. I found a spring in my supply of extra springs that would fit in the brush hole in the brush holder. This spring was considerably different than the original spring. I reinstalled the brush holder with my replacement spring. The Bakelite is brittle. I overtightened one screw and broke the corner off. I glued the corner back on with super glue. The motor ran very smoothly. I was able to start the motor repeatedly on 1 or 2 V, DC. When I reversed the DC polarity, the motor ran smoothly in the opposite direction.

I will keep working on the two locomotives I have with the Universal motor. The motors are still are a bit sluggish on my 20VA DC packs so I may need to upgrade there, but they will operate on the layout with the original motor.

UPDATE: Short version: I purchased a new, larger DC power pack and while it works great, something about the output waveform won’t allow the motor to run. Bench testing the Universal motor as described above is best done on AC.

UPDATE 2: Another short update, it is for me anyway the easiest to bench test motors when connected to a tender that has the correct rectifier setup. But the method above clearly works on AC.