In older pictures of eastern railroads, I’ve seen photos of coal cars that had their side and ends raised, to increace coal capacity. Is there any inherent reason why a set of coal cars (technically gondolas, I would guess) could not be built shorter( in length) and taller (in height)? If each car were say, 20% shorter, but carried the same amount of coal; couldn’t it be roughly 20% more efficient? I realize that more power would have to be added. It would seem most other cost variables, like labor, and track capacity would see an improvement. The height limit of the cars could be similar to that of the locomotive pulling it. There has to be some really obvious reason why this wouldn’t work. What is that reason?
The reason is that coal cars are constructed to an overall length of 53’1" over couplers to fit in just about all of the rotary dumpers out there. Change their length, and everybody’s got to re-tool.
I’m not even sure that today’s coal dumpers could accommodate the increase in height of cars that would be brought about by an increase in gross rail load from 286K to 315K.
The laws of gravity and inertia are still in effect. The center of gravity is going to be higher, and it’s not like you can put the lighter stuff on top.
What you’re talking about is the “drop deck” effect aka doublestack well cars. You build the railcar so that the bottom is a few inches off the top of the rail to get the center of gravity as low as possible, then you can make the car both shorter lengthwise and taller heightwise.
Now, I don’t think you’d want to make heavy haul cars “taller” per se, but you do get an advantage if the center is as low as possible. That said, I think the Southern 100 was the best example of putting those principles to work. To recap, the Southern 100 was a four unit hopper using single axle bogies on each unit, and was connected to each other by a link pin. The single axle bogies allowed more “lower level” room for revenue product instead of taking that space for the two axle/three piece bogies with center plate et al.
Now, Overmod a while back mentioned the idea of using frame mounted wheels for the single axle railcar instead of wheels on axles. That would allow even more space down low for revenue product where the axle used to be.
OK Questions: Are the dumpers set up for only one 53’ car at a time? What is the effect of changing the center of gravity? Don’t some power companies own their own fleet of cars? Thanks
Dumpers are designed for either one or two cars at a time. Most power companies own their own cars or have them on long term lease. The effects of raising the center of gravity will be to make the cars more likely to derail. It takes less tipping from vertical to make the car fall over. When the center of gravity passes the outside rail the car will fall over. the higher the center of gravity the smaller the angle required to move the CofG over to the outside, so the car is less stable. This is one reason why most coal gons have some design of “tub” to lower the height of the load.
Other factors to consider, dumpers are designed for a particular car length and the utility may not want to replace the dumper. For strength reasons the center sill of the coal car either hopper or gondola, must be on the coupler line. Because of the high pulling and buff forces, these cars cannot use either drop centers or side sills.
It becomes a question of reducing tare in one aspect of the car design but having to add tare in another to maintain structural integrity. You can have drop centers and side sills in heavy haul cars (there are plenty of grain hoppers out there without center sills), but in order to provide the strength necessary to resist draft and buff you may be adding more tare in the drop deck and/or side sills than what you have eliminated in getting rid of center sills, center plates and axles (in the four wheel car concept). We don’t know because no one has tried to design a modern four wheel gondola for coal, since the single axle designs are out of favor and the four wheel axleless design has never been tried (as far as I know).
Don’t forget, a single axle or four wheel axleless gon would be half the length of a standard gondola, so the side sill and drop deck structural material need is less than that required for a longer version. You are adding two extra end walls for a 2 unit x 25’ carset compared to the 53’ four axle gon. But you are also able to use the side sills for both draft and buff resistance, and for containing the product.
No Grain hopper is designed for 360,000 lbs. drawbar loads. At least not yet.
If there were you would see 135 car Grain Shuttle Trains instead of the industry standard 110 car trains. All of the modern coal cars are designed for this load this is why none of them uses side sills, the trade off for enough strength to transfer that much drawbar pull from the coupler centerline to side sills increases the tare more than desireable.
You read about differing ideas and design changes pertaining to continers, but hardly anything about coal car developmet. Is there not much “new”, or, is it just not glamorous enough to rate any mention?
If the modern coal gon length is shorter than current coal gons, say half the length, you could probably go side sill and still maintain tare advantage. Let’s go back to the Southern 100 for a minute:
http://southern.railfan.net/ties/1965/65-8/toc.html
Granted, the Southern 100 used a center sill, link and pin connections between each 25’ sub unit, and multiple bottom dump openings. After all, this was the 1960’s, and the multiple openings and link and pin connections proved to be drawbacks to the cars success.
Now, if we “modernized” the design to be a true gondola, with the side sills, solid drawbars between the “A” and “B” units and the “C” and “D” units, a rotary drawbar between the “B” and “C” units, and rotary couplers on the ends, then we have something that has a load factor about 30% greater than the best all aluminun 53’ coal gon. The typical 53’ rotary dumper at the utility could also take the two subunits of a new 100. We’ve saved on tare, we have a lower center a gravity. The only thing standing in the way is the rail industries avoidance of single axle car designs.
That seems like an awful lot of engineering to save a small percentage of tare weight. Now factor in the additional maintenance costs over the lifetime of the equipment compared to existing designs and a reasonable discussion over designs can be had. New is not necessarily better. It may be cheaper in the long run to live with some extra tare weight in exchange for lower maintenance expenses.
The way I look at it, it is the utilities who decide what kind of railcar suits their needs. A 30% increase in load factor is no small potatos when analyzing the cost/benefit of new designs. My belief is that it is only the railroads’ resistence to perceived radical change that prevents such new designs.
Dave-
This car weighs 41,180 lbs and carries 244,820 lbs, which works out to 85.6%. http://www.rrpicturearchives.net/showPicture.aspx?id=248662
Do you have the figures for the short lived BN Trough Train, and what would the numbers be for your proposal ?
The car you pictured has a load factor (e.g. loaded to unloaded ratio) of 6.9 to 1, almost the same as the original Southern 100 using 1960’s technology. One might assume a more modern version would be able to increase the load factor by a fair amount due to modern material and car construction benefits, but I have no real figures to provide. But we do know that a gon will have reduced tare compared to a hopper via elimination of the bottom chute mechanisms, air suspension instead of spring suspension to supplement the primary suspension system, 36" wheels instead of the 100’s 38" wheels, using the same outside bracing of the “box” instead of the 100’s interior ribbing, and letting the side sills resist draft and buff instead of a “redundant” center sill should in theory increase the load factor even more.
I don’t know about the Trough Train, but since it was a bottom dump hopper type it might have a disadvantage compared to rotary gons, and it would be hard to convert a Trough-type car into a rotary dump gon. And multiple subunit railcars beyond a 5-pack are also out of favor with railroads.