[traction fan]

I've generally assumed that designations like "50 ton hopper", "70 ton hopper", Etc. referred to the maximum load the car was designed to carry. Another assumption is that these designations did not include the weight of the car itself. Am I right? Also does anyone know the overall weight of a fully loaded small two-bay hopper that would be a close prototype to the Micro-Trains N-scale model?

Thanks;

Traction Fan :smilie_daumenpos:

 

[mesenteria]

Cut 'n paste from another forum/site:

The maximum gross weight is the number that matters. It's an admittedly arbitrary number within a certain range (there's no practical difference between 286,100 lbs and 286,000 lbs.) but it is the number that is established by agreement among the railroads. The line has to be drawn somewhere and that's where it's drawn. The car is placed on a scale, and whatever it weighs is subtracted from the desired maximum gross weight, and that difference becomes the capacity.
Steel castings and forgings (truck sideframes, wheels, etc.) have small variations in wall thickness, etc. Steel shapes and sheet have dimensional tolerance range according to their specification. If you want to buy 0.5000 sheet steel and not 0.5010 sheet steel or even 0.5001 sheet steel you can do that, but you will pay a tremendous amount of money for it.
Consult your ANSI standards for sheet steel and shapes, and AAR standards for steel castings and forgings. They will describe to you the tolerance range that is the standard for the steel manufacturing industry and the railroad industry, respectively.
The variations tend to mostly cancel each other out within a narrow range.
If you want precision you will pay for it. No one needs precision in a freight car body. For each order the manufacturer provides a guarantee that the cars will fall into an agreed-upon weight range, a range which is derived by the manufacturere from experience. If you wanted every car in an order of 1000 cars to weigh within 100 pounds of each other you would pay a huge premium to the manufacturer. Will you realize that premium in car efficiency or rate reductions? Absolutely not.
Manufacturing has tolerances established for everything. The tolerances are only as tight as they need to be for the function of the product, within economic reason. At a certain point the cost of manufacturing to tighter tolerance exceeds the value realized from the tighter tolerance, and that's where you establish your tolerance range limits.
S. Hadid

 

[MichaelE]

To put that into perspective the maximum take off weight of a fully loaded Boeing 727-200 Advanced is 70 tons. One fully loaded hopper or box car.

 

[gregc]

Also does anyone know the overall weight of a fully loaded small two-bay hopper that would be a close prototype to the Micro-Trains N-scale model?

isn't that information posted on the car? "load limit" and "light weight"

 

[ebtnut]

Right. That BNSF car, fully loaded, would weight 131.5 tons. Note also that a "full" car is also dependent on the material it is designed for. A 100-ton coal hopper is full when it crowns the load of coal. However, if that same car was assigned to haul something else, like iron ore, "full" may only be half the hopper because iron ore is much denser than coal.
That's why dedicated iron ore service cars were so short with a 70-ton load limit.

 

[cv_acr]

I've generally assumed that designations like "50 ton hopper", "70 ton hopper", Etc. referred to the maximum load the car was designed to carry.

Short answer, yes.

"50 ton hopper" would refer to the (nominal) design load capacity of the car.


*Very* roughly speaking,

50 ton capacity cars were typical of cars from about WWII and earlier.

70 ton capacity cars were built through the late 1950s-70s.

By about the 1980s, many hopper cars were built to 100T capacity, although some other cars like boxcars were still ~70ton.

Most modern cars today are 100 ton capacity.

 

[cv_acr]

Right. That BNSF car, fully loaded, would weight 131.5 tons. Note also that a "full" car is also dependent on the material it is designed for. A 100-ton coal hopper is full when it crowns the load of coal. However, if that same car was assigned to haul something else, like iron ore, "full" may only be half the hopper because iron ore is much denser than coal.
That's why dedicated iron ore service cars were so short with a 70-ton load limit.

And why modern 100 ton covered hoppers come in so many sizes from short 2-bay cars for sand, salt, and cement service (heavy) to "standard" 3-bay cars for grains and many other dry bulk materials such as fertilizers and dry chemicals, to larger 4-bay cars for light materials like plastic pellets.

Covered hoppers can also vary with specialized unloading features for using air pressure for unloading some types of commodities. These types of cars can be extremely specialized to the load(s) they're meant to handle whereas boxcars can be more generic and standardized.

 

[Jscullans]

I can tell you that at the local mines they load those jokers down to the loaded weight limit every time. Same thing with the plastic plant we have in the area. It’s awesome seeing a string of 6 to 9 gevo locomotives ripping a 200 car unit train of loads out of a rail yard clawing their way to the bigger terminals outside of Chicago. I ran across a dash8 painted in bn scheme there the beginning of summer.