When a rail car manufacturer comes up with a new boxcar design, is there a certain load density considered when designing it? What I mean is this. A boxcar can be thought of as having two limits. Volume and weight. You can’t exceed the first and it is bad to exceed the second. Take for example the 60 foot excess height boxcar MT’s is putting out. Off hand I don’t know what the volume or load limit is on this prototype but one can assume that if you filled it with goose down pillows you have wasted a lot of its potential weight carrying ability. Likewise if you used one to haul tungsten steel ingots or depleted uranium slugs, you would quickly overtax its weight limits long before it is filled. Thus wasting volume. So what’s the answer? What is considered the “Ideal” weight to volume load? Something that would fill the volume of a big boxcar, while at the same time make maximum use of the cars weight limits? Are box cars designed at the time for a specific load, and only later used for general purposes? Such as the Red Caboose 62” “Beer Cars. This could apply to other enclosed rollingstock such as hoppers and tanks Does anybody even understand what I’m trying to ask? Because I’m not sure I have done a very good job of asking it.
You pose a very valid question. My take on this is: the RR's get paid more for a weight capacity-loaded car than a volume capacity-loaded car. Say a coal hopper has a max load weight of 118 tons. It is loaded to 117.9 tons, very near the max. Its volume capacity is (wild guess) 4000 cuft. The car is only loaded to 3800 cuft. But the RR gets paid for the full load. In an appliance boxcar, say 5000 cuft is the max volume, and 70T is the max weight. The car can be loaded with dryers and washers, to capacity, and maybe only weigh 40T. The car would make more revenue if it was loaded to max weight, but the physical capacity is maxed out. If the RR charges by the ton, the car wouldn't make the max revenue. A classic example of weight versus volume is a taconite train, completely loaded to max weight capacity, yet the cars look half full (especially if the cars are regular coal hoppers). Does that make sense? of course, the RR wants to load every car to capacity, to take advantage of revenue earning potential, but not every shipper can fill each car to capacity--volume or weight.
In the shipping industry, the phenomena you described are called mass-out and bulk-out. The "tonnage" you hear for a ship is actually a measure of volume; one ton is 100 cubic feet. Cargoes denser than this mass-out; less dense ones bulk-out. Whatever the reference cargo is, it must have an average density about 1/3 that of water. Anyway, back to trains... Different size cars are designed for different density loads. For example, 87' hi-cube boxcars are 100-ton capacity, no more than 50' boxcars. 20' containers have the same maximum load as 40'-53' containers; this is why you often see double-stacks loaded with a single level of 20-footers. A four-axle depressed-center flat is made for excess-height loads that aren't overly massive. One with 8 or 12 axles can handle heavy excess-height loads.
The railroads get paid by the "Ton-Mile". So much a ton per mile traveled. There is also a "minimum fee" for shipping. A carload of goose down pillows would cost the same to ship as a carload of dishwashers because of the "minimum fee". Also, some shipments are combined to get the car loaded to capacity. "LCL", or "Less than Car Load" service combines different shippers going to the same destination. Most freight cars are dedicated to a certain service - the one they have been designed to fulfill. Car manufacturers have tried to come up with multi-purpose cars for shipping. Grain cars with "hidden floors" and side doors in them so they could be used like a boxcar come to mind. Most all have failed. Who wants to ship furniture in a car that previously had onions for cargo? Versatility of a freight car goes into the design. Would you rather have a large inventory of load specific cars? Would you have a smaller inventory of cars that could carry a variety of cargo? The railroads have to strike a balance between the two choices. Stack wells can only carry containers, but if you consider the inventory in those containers then you are actually carrying all different kinds of freight.
Isn't LCL obsolete? One of those non-profitable businesses railroads were required by law to perform before deregulation?
LCL regulations are gone. Still, some shippers combine lading in a single car. It isn't nearly as prevalent as it used to be. Sawdust and wood chips are carried in specific cars to maximize tonnage. Hence their size.
