Gilbert 312 "AC"...

The "AC" locos will operate on either AC or DC. They have wire wound field coils. The "DC" locos had permanent magnet fields which operate on DC only. That's the short story.

Most American Flyer in the O and S gauge of that era use what are series wound motors - or universal motors. These were initially designed for use with the AC toy transformers of the day, but can be run on DC without major issues*. These items generally do not have a suffix, but occasionally an AC suffix will be applied.

As a presumed cost cutting measure, some American Flyer locomotives were manufactured with DC motors. These cannot run on AC. These almost always have a DC suffix.

Now, to further confuse things, more modern Flyer have "DC"/can/"maintenance free" motors, but have conditioning/command control circuitry designed to pull AC, not DC, from the rails. Obviously, this continues the roughly century tradition of low voltage AC on the rails. This command control circuity can be damaged by DC on the rails.

*These motors run hotter on DC and can result in unwanted magnetisim

@bmoran4 posted:

Most American Flyer in the O and S gauge of that era use what are series wound motors - or universal motors. These were initially designed for use with the AC toy transformers of the day, but can be run on DC without major issues*. These items generally do not have a suffix, but occasionally an AC suffix will be applied.

As a presumed cost cutting measure, some American Flyer locomotives were manufactured with DC motors. These cannot run on AC. These almost always have a DC suffix.

*These motors run hotter on DC and can result in unwanted magnetisim

So an "AC" engine is the same as always and was only given that suffix to differentiate it from a "DC only" loco...?

I had always understood that these would actually run better ( and cooler) on DC...

Mark in Oregon

You can revisit your thread here: https://ogrforum.ogaugerr.com/...tors-ac-vs-dc?page=1

Bottom line, these toy train series wound motors typically have 3 poles and that is what truly limits the "performance". Universal series wound motors run hotter on DC because of, unlike AC, the non-existent phase angle difference between voltage and current. The AC wave also provides a cooling break that is not provided by DC. You can geek out on the math behind all of this.

The Gilbert universal motors may run very slightly quieter on DC but never cooler.

Back to the original comment about the "AC" suffix on some engine numbers. In 1949 Gilbert began adding the "AC" suffix to engines and for the most part the tender lettering on "AC" engines changed to sans serif. Probably someone in design or marketing advanced this idea, there was no significant internal change in the engines that drove it. In 1952 with the introduction of knuckle couplers on two engines (Hudson and Northern) those two engines were numbered with a "K" prefix and the "AC" suffix was dropped (a 325AC became a K325). In 1953 with the wide use of knuckle couplers the "AC" suffix was dropped from use and the KC engines were up numbered so a K325 was now a 326. Serif tender lettering also reappeared on KC engines and "American Flyer" tenders again became "American Flyer Lines" tenders.

The last DC motored engines were made in 1950, from 1951 onward all Gilbert engines had universal motors so the "DC" suffix was not needed.

The "DC" suffix was not used for most DC motored engines. Most were just numbered as 332's and 342's but with DC motors. When purchasing a 332 or 342 it is necessary to look at the motor to see if it is a DC or a universal motor.