I have not idea why Atlas calls this a "90 ton" hopper. It is all but certain that this hopper is patterned after the N&W H11a hopper, which was 1st built in 1963. Intitially, they were rated at 95 tons, then around 66 or so they were all re-rated to 100 tons. Many other roads subsequently ended up owning very similar hoppers. Mark
Can't say I have either... nominal capacity was always an odd marking, and I'm not aware of any rules regarding it's determination either. Pretty certain it was dropped in 1982 or so. Note that nominal capacity was rated to the nearest 1000pds, and load limit is to the nearest 100pds. Be careful thinking a car will volume out... sure a 70T coal hopper can generally carry 140,000 tons of coal... but what if that coal is wet... or how much gravel could it carry... lime, etc? Then you have roads like N&W who intentionally derated the nominal capacity of it's two-bay hoppers to 50 tons to avoid the use of an empty load brake, even though they were designed to carry some 57.5 tons (including heap calculation).
So are we saying the 90T Hopper is not prototypical? Is it still used? I've been collecting the CSX ones as they come out to make a decent coal train as an alternative to Kato sets or more expensive (but better) brands.
The only thing that makes it not proto is the trucks on it... many similar cars are still in use today, though due to age thier numbers are dwindling. For the price, I wouldn't worry about it.
In Britain, if you refer to a ton (not tonne), it's assumed to be a long ton. In the US, it's assumed to be a short ton, and that's what railroads use.
I think the thing to remember is that "90T" is really a marketing number, and the stencil numbers are the real deal. Here's an interesting quote (http://www.cohs.org/history/equipment/freight/): Because bituminous coal was slightly heavier than northern anthracite coal, the C&O's capacity ratings became very conservative. Standard cars of the times might have been listed as 55-ton designs, but after the AMC was formed, they became 50-ton designs for the C&O Lines. Eventually the standard 50 and 70-ton cars of the 1920s and 1930s would evolve into 60, 80, and 100-ton cars of the 1960s and 1970s. One of the things to remember is many shippers see these cars not as weight, but as cubic feet. 4000 cubic feet of coal may weigh one figure for one type of coal, and one figure for another type of coal. I think it's also not uncommon for a railroad to take a 100T car and say you can only put 90T in it in an effort to keep from beating up the equipment so much (car, bridges, etc).
We can't make the assumption that the data Atlas etc. put on their models is accurate either unless you have a prototype photo to compare it to.
Leo brings up 2 good points. "xxx Ton" car is a marketing thing, kinda like locomotive "classes". The AAR uses 2 formats to describe a car. A 2-letter "class" and a 1-letter + 3 number "type". The descriptor for a "90 ton" hopper like Altas' is a H250. The H250 "type" of car is unequipped (i.e. no cushioned drawbar), has a load limit of 155,000 to 184,999 pounds, and non-rotary couplers. The AAR "class" on this car is HT. A HT class car is described as such: In reference to restricting load depending on commodity, we run "100T" (H340) and "105T" (H350) cars on our rock trains, however they are restricted to 90T and 95T respectively.
