To understand the history of the modern coal hopper, we have to start out at the dawn of the steel-car era. In the 1890s, the typical coal car was either a hopper-bottom gondola (flat floors over the trucks) or full-blown hopper cars with sloping floors and horizontal drop doors under the center sill. Sawtooth-style hoppers came into somewhat common use in that decade, with the 35-ton Pennsy GG of 1895 combining the sawtooth hoppers and a sloped floor. About this time, Carnegie Steel was taking some tentative steps toward building steel ore cars for the newly-extended PB≤ and, as things turned out, the Schoen Pressed Steel Car Company ended up as the pioneer of the steel hopper. The first Schoen cars for PB&LE were built in 1897, and Schoen was building larger 40 and 50-ton cars along similar lines for the PRR, B&O, and P&LE by 1899.  Tens of thousands of cars were on order by 1900. Schoen was forced out about that time and the firm dropped his name, but the Pressed Steel Car Company was the undisputed master of the steel car market. 

Pressed Steel (PSC) developed a version of their car without separate side sills in 1900 and moved into the general freight car business. Cambria Steel Car (CSC) started out as a gondola builder in 1901, but soon moved into building Vanderbilt-design hoppers. The Vandy was a bizarre creature, with a hopper body supported by a maze of steel trusswork.    American Car & Foundry’s (AC&F’s) early steel cars were built at their Detroit plant, with one group of diagonal-truss hoppers going to the LS&MS in 1902.   Standard Steel Car (SSC) got its start in 1902 utilizing ex-PSC personnel to build their own hoppers made from standard channels and angles instead of the stampings characteristic of PSC’s cars.

Up until 1905, each of the main builders had their own proprietary design (except for AC&F which apparently abandoned its LS&MS design in favor of building PSC and SSC clones), but changes were on the way. In 1904, Cambria and AC&F built an 8-panel design with a combination of pressed and standard shapes (this eventually became the PRR Gv). A year later, B&O adopted a similar 8-panel car (class N-10), and PRR Lines West took delivery of a 6-panel version of the Gv (known as the GLa) from the “Big Four” builders. Also in 1905, another 6-panel design was adopted by the builders and built in massive numbers for the next two decades. This “early standard” design proved to be extremely popular. The old PSC designs and the Vandy hoppers were largely abandoned at this point, but variants of the Standard Steel car were adopted by a few roads (Reading and DL&W, for example) and built in fair numbers into the Teens. There was a blizzard of other designs, but most of these were one-offs or peculiar to one or two roads.   Most steel hoppers followed what quickly became the standard layout of two sawtooth hoppers and outside bracing for the sides. 

Thanks To David Thompson

It remained the unofficial standard until the 2-bay hopper design with offset sides that had been first proposed in the 1920s appeared 1934 to replace it. The AAR adopted it as a standard design the following year. The offset design permitted greater interior capacity than a rib side car with the same outside dimensions.  **Reference Bluford shops