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S Gauge Prototypes - Boxcar-ology 101
American Flyer®
Connecticut S Gaugers

For Scale, Hirail and American Flyer S Gauge Model Railroaders

S Gauge Prototypes - Boxcar-ology 101
by Pieter Roos

A question came up recently at a meeting concerning the prototypes of the various S gauge box cars available. In this article I'll attempt cover the prototypes of the most common models together with a bit of their history. Additional information on this topic may be found in various books, past issues of RMC, Mainline Modeler and especially Model Railroading magazine and Railmodel Journal. S Gaugian has published articles on the prototypes of certain AF cars, and Ted Larson has some data on his web site. Also worth looking at are the Steam Era Freight cars site and the RPI site (although the later is now subscription only).

Prior to the First World War there were few standard designs for cars. Most railroads specified their own designs to builders, or built cars themselves, so nearly every railroad's cars were unique. The only RTR S Gauge car to fall in this period is the AF "Hayjector" car, an all wood boxcar with open vents in the sides and one open door. I'm not aware of any specific prototype, although it does resemble a ventilated boxcar of the type used for produce (ie: like the ACL "watermelon" car). The AF car is too big for most such cars, especially the height, but can be used as such. Paint it boxcar red, or red with yellow sides, and letter it for almost any eastern or (especially) southeastern railroad and it should work.

When the United States entered WWI, the railroads were not able to meet the demands of increased wartime shipping. As a result, the Federal Government took control through the United States Railway Administration (USRA). The USRA specified standard designs for locomotives and freight cars to expedite production, and assigned cars to the railroads to assure the movement of wartime freight. Two of the most common designs were the USRA Double Sheathed (DS) and Single Sheathed (SS) boxcars. RTR models both these are produced by S Helper Service, while 'S'cenery Unlimited has a resin kit for the DS car. Both were built by the thousands under USRA, and the railroads built more thousands of copies for themselves after the end of USRA. The DS car has wood sides, a heavy fishbelly underframe and Murphy steel ends (thin, round ribs tapering to a point at both ends) in three panels of five ribs each (called a 5-5-5 Murphy end). The SS car had similar ends, a straight center sill underframe, and horizontal wood side sheathing behind hat section steel framing. Later copies often had different end designs or "z" section steel framing. Most of the DS cars were rebuilt with steel sides during the 1930's, along with a few of the SS cars (although the majority of the SS cars remained in service as built into the 1950's). S Helper has a RTR model of a rebuilt USRA car. According to Don Thompson, the SHS car is based on the Frisco (SL&SF) rebuildings, which did not increase the car height. Since most of the rebuilds varied greatly in height and design, the model is not necessarily an exact for other paint schemes. They are still useful models, and represent cars that remained in service until the late 1950's or even the 1960s and a few into the 1970's.

In the 1920's major American railroads banded together to form the American Railroad Association (ARA). The association proposed a variety of standard car designs. Interestingly the designs were in some ways less modern than the USRA designs of ten years earlier, particularly in the inside height of only 8 feet 7 inches. Infighting between the member railroads (particularly PRR and NYC) kept the steel boxcar standard from being accepted. Non-the-less, the PRR built over 25,000 of their version as class X29, and other eastern and mid-western railroads built thousands more of their own versions. All these varied in the selection of roof, ends and underframe design, so the "standard" hardly existed. The AF steel boxcar appears to be based on a 1930's version of the X29. While most X29/ARA boxcars had the flat plate ends seen on the Walthers/Train Miniature X29 car in HO, the last PRR cars built and some of those built for Pere Marquette, C&O and Lehigh New England all had Dreadnaught ends as modeled on the AF car. The roof on the AF car appears to simulate the flat plate roof of the X29 while most others had Hutchins or similar ribbed roofs applied. It might be reasonable to save a carbody with broken ends by sanding off all the end detail and adding styrene sheet plate ends. The ARA design of the side sill was flawed, resulting in trapped rainwater rusting out the bottoms of the side sheets, which was repaired by fastening patch panels of sheet steel over the rusted areas. A carbody with cracked or broken lower sides could be saved by attaching thin styrene "patch panels". In converting these cars to scale, it is worth noting that the Ace conversion floor is not modeled after the ARA design, and that the PRR X29's all had truck centers 5 feet from the car end, while the Ace floor and most other ARA cars had 5 foot 6 inch spacing. Trainstuff once offered resin and wood kits for the plate end X29 and auto car version X28, as well as the double and single sheathed ARA cars. Bill Lane is importing a brass X29 car as well, all of these are more accurate models than the AF car, but Gilbert's car is still a reasonable representation of this important prototype.

By 1932 the ARA had been replaced by the Association of American Railroads (AAR). The AAR issued standards for a new, modern steel boxcar design which continued to be built in modified forms until the late 1950's. The depression prevented many of the AAR 1932 design cars being built, and those that were constructed had an amazing variety of components from Seaboard's flat plate ends and roof (like the X29) to C&O's "waffle iron" Deco ends and radial roof. No model of the 1932 design exists in S, although the major difference between this standard and the later 1937 and 1944 designs is the height, so a model of the 1937 car can be cut down by six inches to simulate these cars.

In 1937 the maximum allowed inside height of the standard was increased from 9 feet six inches to ten feet. Increasing traffic generated by the coming war and ending of the great depression caused an explosion of car building, mostly to this design. The concept and economic advantage of a standard seems to have caught on by this time, as less variation in components is found. Nearly all cars had Dreadnaught ends and murphy steel panel roofs (there were still exceptions). The earlier cars had square cornered ends, but the design of the Dreadnaught end was changed about the time this standard was introduced, so many more cars had the "w" corner post design with rounded corner ends. Pacific Rail Shops makes kits for the 1937 AAR standard boxcar, with both end types and in single door and double door 40'foot versions. Des Plains sells the PRS kit with the optional Viking corrugated roof panels used by some railroads.

By 1944 the standard interior height was raised to 10 ft 6 inches. Cars of this height can often be recognized because the Dreadnaught ends have two panels of five ribs each, instead of a lower panel with five and an upper panel with four ribs. PRS has these cars as well. In 1947 the design of the Dreadnaught end was revised to the "Improved" version. The end ribs changed shape (the new shape is often called "rolling pin taper") and the short "darts" between the ribs now extended across the width of the end. By 1949 the Murphy roof had changed from rectangular panels to the "diagonal panel" design, and soon after the Dreadnaught ends changed again to the "banana taper" late Improved Dreadnaught End (IDE). These later cars are represented by the American Models 40 foot boxcar (early IDE and diagonal panel roof) and the Pacific Rail Shops 50 foot single and double door cars. Note that if used as a steam/diesel transition car, the American Models boxcar should have the tack boards on the doors and ends mounted much higher, the position specified in the instructions is for later cars without roof walks. The AM boxcar also represents a car built to the earlier 1937 10 ft inside height. Such cars were built with Early IDEs for a number of railroads, although I think most or all had the earlier rectangular panel roofs.

Thanks to Don Thompson of SHS for his additional information and corrections.

Steam Era Freight Cars
Ted Larson's S prototypes page

The short version:

Start - End dates of use Model and Prototype designation

1900 - 1940s AF "hayjector"

1919 - 1950's SHS USRA double Sheathed and Single Sheathed

1923 - 1960's AF ARA/X29 boxcar

1932 - 1970's PRS AAR boxcars

1947 - 1980's AM 40' boxcar, PRS 50 ft boxcars.

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