[O] 3-rail vs. 2-rail

2-rail is DC and 3-rail is AC, 2-rail cars can run on 3-rail track but 3-rail cars will short out 3-rail track.

Also, while prototype cross section rail is becoming more prevalent in 3 rail, all wheels have larger flanges to allow use on tubular rail. Many 3 rail cars and locomotives are undersized and shortened, while 2 rail equipment are virtually always true 1:48 models of the prototype. In addition, 3 rail trains are usually designed to operate around sharper curves, so: o Cars sometime sit higher on the trucks to allow the trucks to swivel through more degrees of arc, o Cars are always equipped with truck mounted couplers, whereas 2 rail versions of the car come with body mounted couplers, o Locomotive models have modifications to allow use on sharper curves which may include: - undersized steam loco pilot wheels, - unrealistic big open spaces under steam loco fireboxes, - end steps on some diesels attached to the ends of the trucks to allow them to pivot and thus avoid super wide coupler openings. Geezer

3-rail equipment uses different track and wheel standards than 2-rail. Since there is no need to insulate 3-rail wheels, 3-rail equipment will short out on 2-rail track. It also won't run through 2-rail turnouts etc, but that's not an issue when there's no power... :-) 2-rail rolling stock will run on 3-rail track, but will bumpity bump through turnouts and crossings, and may even derail.

Then there are the couplers....

Bottom line: if you must have a certain car, and it comes only in the other version, you'll have some converting to do.

HTH

I'm surprised no one mentioned that 3 rail trains have many compromises because they are designed to fit a large O gauge train layout in a MUCH tighter space. Yes, they have non-prototype features so they can negotiate very tight turns. This allows a more complex layout to fit in a much smaller area. I like the bigger size of 3 rail O gauge over scale HO and focus on just the scale sized Lionel/Williams/MTH stuff.

2 rail O scale is definitely true to scale and true to prototype but you had better have a very large area to devote to your layout. My small O gauge layout is reasonably interesting but fits on a 6.5' X 12' table.

True. Three rail does come in at least a couple of sizes. Various manufacturers call it by different names. The key for a full sized O gauge item is whether it's referred to as 1:48 or quarter scale.

I wasn't aware of this while accumulating rolling stock prior to getting the layout started. The grandson ending up getting some of his inheritance a bit early when I gave him the smaller items. 1:48 intermodal just doesn't run too well with 1:64. Of course our friends in the UK compound the problem by using

1:43.

The most consistent verbiage I've found is when the catalogs indicate O versus O-27, As far as I'm aware, MTH's Premier line is all 1:48 as is Lionel "Standard".

I've found that the 1:48 is the most nearly prototypical, but it also requires the larger diameters. (To compound the problem O uses diameter instead of radius so O-72 makes a six foot circle.)

Carl

Carl Heinz wrote: [...]

Er, Carl, O _scalers_ refer to radius, O _gaugers_ refer to diameter. The difference? "O gauge" is "tinplate", a term that harks back to the time when toy trains were made mostly of lithographed tinplate. The habit of referring to diameter originated with Lionel, I believe. There's a lot more to the history of O scale and O gauge tinplate, some of it not very nice, but this isn't the time to discuss it.

Apart from the differences in the design and technology of the trains, I've found that both branches of the O scale/gauge fraternity accommodate tastes ranging from train runners to prototype operators, from bare plywood to completely scenicked. Yer pays yer money and makes yer choices.

Have fun!

True, but what I was trying to point out was that when reading such things as a Lionel or MTH catalog and the text indicates something like "requires O-72", that's a diameter, not a radius. I have a friend who is more familiar with N scale who had some trouble adjusting to this because he doesn't run O gauge. He thought O-36 referred to a six foot circle.

I fall into the O gauge category. Apologies to the O scale folks. :>)

Carl

My question came up when seeing cars that seem to be pretty close to prototype, but offered in both 2-rail and 3-rail versions.

For example, Atlas' 50' PS-1 boxcar:

Atlas makes 1:48 scale cars, and offers them in 3-rail versions compatible with Lionel etc as well. At a premium, not surprisingly. They are very well done - if there's one that catches your fancy, it might make a cool mantel piece display mounted on some well-modelled track on an oak plinth... :-)

HTH

The Lionel catalog

has listings such as: "Traditional Diesel Locomotives" and "Standard O Diesel Locomotives." How do they relate to 3-rail vs 2-rail categories? Are "traditional" Lionel products the 3-rail offerings, and "standard" products the 2-rail stuff?

Correct! I should have described this a question about O gauge equipment, not O scale equipment.

__________ Mark Mathu The Green Bay Route:

"I started out with nothing and I still have most of it."

messagenews: snipped-for-privacy@4ax.com...

has

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All of the Lionel items shown in the catalog are 3-rail (except the "Large Scale" items). "Traditional" and "Standard 0" are described on page 5 of the catalog.

Bill Bill's Railroad Empire N Scale Model Railroad:

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I forgot about American Flyer. They are 2-rail S gauge. All the 0 gauge items are 3-rail.

Bill Bill's Railroad Empire N Scale Model Railroad:

History of N Scale: Railroad Books, Toys, and Trains: to 1,200 sites: