Oversize hoppers/coal gons

[Allen Hazen]

BobLI has posted a question about oversize tank cars: the "rail whale" tested in the 1960s, etc. I have assumed that these were banned by the FRA because of concerns about the amount of toxic/flammable/explosive liquid that could be spilled if a single car of this size ruptured (that would be my GUESS answer to his question), but if someone can give a DOCUMENTED answer, that would be great!

But the topic brings something else to mind. Back in the steam era, the Virginian railroad had a fleet of six-axle coal cars. Why has this not been imitated? Four-axle cars in unit trains from the Western coal fields are pushing the limits of axle-load permissible with normal-size wheels and rails made from ordinary steel. There are obvious economies in loading as much in a single car as possible: running fewer cars saves on capital costs (fewer cars, so fewer sets of brakes, fewer truck center plates, fewer couplers etc etc etc). Why hasn't someone built a fleet of six-axle (so, maybe, 180=ton capacity!) coal cars for unit train use? Maybe a NEW power plant could buy them: one which, since it was having to build a new car-dumper anyway, could get one that could accommodate the bigger cars.
Possibilities that come to mind include:
---For some reason 3-axle trucks cost a lot more than one and a half times what standard 2-axle trucks cost
---Current 4-axle cars are bumping up against some OTHER size limiting factor (structural strength of center sills?)
---You can't get anybody to lend you money to buy coal cars unless they are of a type the Equipment Trust holder can readily sell to other operators if you default
---Sheer institutional conservatism

Anybody out there know something? VGN "battleship" cars certainly made coal trains more interesting visually!

[v8interceptor]

There has been some design work done in recent years on a 181 ton capacity 6 axle coal gon:

http://www.railmotive.net/20181ton.html

http://www.railmotive.net/19highcapacitybolsterl.html

Note that the 6 axle bolsterless truck was also proposed for higher capacity well cars.
I guess the current industry standard 100 ton cars on conventional 2 axle trucks is considered sufficient at the moment.

[Allen Hazen]

v8interceptor--
THANKS!
Sounds as if these could actually get built if (i) the economy recovers (ii) some customer (and said customer's bankers) are just a little bit adventurous.
Weight and length of a loaded 6-axle hopper, as described, would not be too different from the weight and length of a modern 6-axle diesel.
(Hmm. Does Norfolk Southern own the reporting marks VGN? Maybe at least if and when these get built the owners would let some railfan group paint a few of them for use in a photo run-by (Grin!))

[Cowford]

Issues that a "mega-hopper" would bump up against: Truck (and car) cost... they'd be smaller production lots so car prices would be dear. Also, existing coal gons/hoppers are ~50'. That concept car posted by V8 is 75' in length. I would imagine that would cause significant compatibility issues as mine mouth and power plant. Here's what makes me the most skeptical: The concept car theoretically carries 50% more product... but also has 50% more axles, and the tare:load capacity ratio would be about the same as four-axle aluminum coal gon. The only benefit I'd see in this car is a very slight reduction in train length due to fewer couplings... too slight to be significant.

[John_Perkowski]

I think the elephant in this room is the rotary unloading gear at who knows how many coal fired plants.

[Allen Hazen]

John Perkowski--
I wondered if maybe the rotary car-dumpers had something to do with it. They make it pretty much mandatory to use cars of a STANDARD length, even if something bigger might in theory be better. (Hmmm. Seems to me this is an issue that arises elsewhere in railroad operations: Standard ... !)
So maybe 6-axle cars will have to wait until a new plant is built with a new, king-size, rotary car-dumper. At which point there will have to be a dedicated fleet of 180 ton coal-gons... I can see how standardization might be a problem....
(Fortescue Metals built an all-new heavy-haul railroad for iron ore in Western Australia within the last few years: big GE locomotives, but only 4-axle cars. Snif.)

[Allen Hazen]

Hmmm.. I **thought** I remembered considering standard-size car dumpers as a reason for the absence of six-axle coal cars, but looking at my original post again I see I didn't mention it: so, thanks, John, for bringing it up: it's certainly relevant.

Cowford-- I think having only two-thirds as many couplers (and air-hose connections) in a train could save on more than length, and MAYBE save a significant amount: the cost of the couplers, etc, themselves. And there might be operational advantages: the reduction in the number of places where a beak-in-two (or loss of brake-pipe continuity) can happen, the reduction in pressure-loss from imperfect connections of air-hoses between cars. But I have no quantitative idea of how important such savings might be.

[Cowford]

Good question Allen. With the widespread adoption of distributed power, I'd imagine the incidence of unintentional train separations has diminished significantly.

[Allen Hazen]

I would imagine that too, Cowford: if it's NOT so, the control software for distributed power needs refinement!
(Hmm. Confession of abysmal ignorance here: the 1970s version of d.p. -- radio-controlled "robot" locomotives -- had strain gauges on the draft gear of locomotives intended for "slave" use, which ***I assume*** allowed the on-board automation to over-ride instructions from the "master" at the head end. (At a guess, the big thing would be to reduce power if there is too much push being experiences on the slave's front coupler, so as not to risk jack-knifing the train.) Do current d.p. units have such sensors?)
--
Distributed power probably also makes another of my putative advantages of bigger cars less important: since the d.p. locomotives act as air brake repeater cars, leakage at air-hose connections is probably less bothersome.
--
I have an awful feeling the case for 6-axle hoppers is looking worse and worse as this discussion goes on: I hope there is something that can be said in favor of them!

[John_Perkowski]

As an aside,

Ordering 1000 cars to Specification X means the engineering is done. You're paying labor and materials.

Ordering new Specification Y means you take a hit on the engineering costs too.

There is a Depression out there, no matter what the folks inside the Beltway are breathing/drinking. Cost avoidance is the name of the game today.

[v8interceptor]

I would imagine that too, Cowford: if it's NOT so, the control software for distributed power needs refinement!
(Hmm. Confession of abysmal ignorance here: the 1970s version of d.p. -- radio-controlled "robot" locomotives -- had strain gauges on the draft gear of locomotives intended for "slave" use, which ***I assume*** allowed the on-board automation to over-ride instructions from the "master" at the head end. (At a guess, the big thing would be to reduce power if there is too much push being experiences on the slave's front coupler, so as not to risk jack-knifing the train.) Do current d.p. units have such sensors?)
--
Distributed power probably also makes another of my putative advantages of bigger cars less important: since the d.p. locomotives act as air brake repeater cars, leakage at air-hose connections is probably less bothersome.
--
I have an awful feeling the case for 6-axle hoppers is looking worse and worse as this discussion goes on: I hope there is something that can be said in favor of them!

You may want to read the TRAINS magazine issue from about 4 months ago with extensive coverage on the practice and history of D.P. The L&N did use the strain gauge system but only on a few sets of power in the mid 60's. The Harris Locotrol radio control system was used by N&W and Southern(and eventually L&N) and was the industry standard even early on. The modern versions of the systems do not have strain gauges on the draft gear but they do allow the engineer to monitor the performance of the remote units (i.e traction control systems) so the head end has some idea how the sets farther back in the train are performing..

[Allen Hazen]

Thanks for the information. I will try to find the "Trains" article.

[Stmtrolleyguy]

I don't really see a benefit right now to larger hopper cars.

-Mines/powerplants are designed around standard-size equipment - changing the dumping equipment would cost money (as mentioned.)
-Will the swing and overhang of longer cars also be a problem in potentially cramped/close clearance ares within a powerplant?

-Removing some couplings within a train might improve train handling a little bit, but the couplers are still the weak points.
-If a smaller hopper is down for repair, you loose some capacity. If a 2x as large hopper is down for repair, you've lost 2x the capacity.
-Larger (and longer) cars might actually be harder to load evenly - rocking and swaying might be a problem.

-Do you still get the same braking force with only 6 axles compared to a normal 8? What happens when these cars are moved empty? They might be more troublesome empty then loaded, since the brakes are set to stop the LOADED car.