I am curious about many things in OO. A conversation in the Facebook American OO Scale Railroading group – a thread on decals – led to a side discussion on the size of Scale-Craft OO tank cars and also Lionel.

Originally, I was thinking to simply update an earlier article (on two Athearn tank car conversions, here), but the topic is big enough to expand into an article.

To begin, I was thinking they were 10,000 gallon cars, mainly because they looked to me like scaled up versions of what I took to be 10,000-gallon HO cars. But it is not that simple, as lots of HO tank car models are really just approximations, they are not real prototypical (for example the classic Athearn models, which is why they work as conversions to OO).

Lionel was never specific as to size or prototype in their catalogs. But it was pointed out that in the 1937 Scale Craft catalog their model is described as being, quoting the catalog, an “A.R.A. 8000-Gallon Tank Car,” “used universally by all the large oil companies and railroads.” The 8,000-gallon figure is used in all subsequent catalogs until the final one (the Round Lake catalog), where the text is tightened up and the figure is omitted. Beginning in 1938 they also note that the car is “modeled from the drawings of the American Car Foundry.”

Looking at another resource, the recently published Kalmbach publication Freight Cars of the ‘40s and ‘50s, I also note that ACF “built cars for UTLX and other car operators from its own successful car designs,” and that the X3 was “the most common tank car of the transition era.” It would be classified as an ICC type 103 car, but that does not indicate size, just that it is a “general-purpose, non-pressure car.”

That information is all good, but what I needed though was a way to calculate the size of the models by tank size. Fortunately, a link was posted to information on a Sunshine Models kit (here), with prototype information. They note that “The Union Tank Line’s X-3 was the most numerous tank car in the U.S. during the classic era. The X-3 was as close to a standardized tank car as the nation’s railroads came.” For us though the money quote is this: “The 37’5″ frame X-3s carried an 8’7″ diameter 10,000 gallon or a 6’4” diameter 8,000 gallon (“skinny 8″) tank.”

With that info and my scale rule and calipers, the S-C tank car (top photo) diameter is around 7’4″ and must have a capacity of around 9,000 gallons. In the earlier article, I had converted an Athearn model (middle photo), that has a diameter around 6’9″ so that is about 8,000 gallons in OO (and the actual length is a bit longer than the S-C model, also seen in the middle photo). Finally, the Lionel model (bottom photo) scales out about 7’6″ diameter, so let’s say it is about 9,000 gallons as well. The frames on all three cars being within 4″ or so of 37’5″, with Lionel very close to on the money for length, compared to the dimension given of the UTLX X3.

Overall, I think the S-C car is a pretty decent model of the X-3 and looks quite nice on Schorr trucks. My guess is that S-C either made the tank too big by accident, or were aiming to create a model that was a good average in look between the 8,000 gallon and 10,000 gallon versions — and then backed away from that in actual marketing. Lionel followed their lead and made a similar looking car, with just enough changed details to catch your eye. I like both cars!

UPDATE: But would note a very valid comment (thank you Stefan B., who got the whole conversation rolling), 8,000 and 10,000-gallon were the standard sizes of the era. Making a car that was an average of the two visually, while maybe a good general idea in those early years of the hobby, leaves us today with OO tank car models that “look right” (to us) but actually are not correct. It would be an interesting project to build an accurate 10,000-gallon car, as the Athearn kitbash 8,000 gallon car is noticeably smaller (middle photo) than the S-C and Lionel models.

UPDATE 2: See this article for more thoughts on the topic.