Eastern Railroad Discussion > aluminum vs steel hoppers

Anyone know the difference in empty weight between a new aluminum coal use hopper car vs an older one of similar dimensions? This weight difference allows
that much more weight in load. Is this correct?

I doubt aluminum would allow more loaded weight per car, but it certainly allows a train to be longer at the same weight, so locomotives pull more $$$$$$$$$$.

BobE

aluminun cars weigh 48-52k mty. steel weigh 55-65k mty and have lower cu.ft capacity.

I dug up some pictures I had in an email that were brand new PSTX cars that are aluminum bethgons. LT weight is 40700. Load LMT is 245300. Compare that to older steel bethgon hoppers Lt weight 57400 and Load LMT 205500. That difference adds up in a 120 car train.

http://www.rr-fallenflags.org/csx/csx381925amg.jpg

<This weight difference allows that much more weight in load. Is this correct?>

You are correct. The AAR limits cars used in interchange service to a maximum loaded weight per axle. Currently, that maximum weight is typically 286,000 lbs (143 tons) for cars such as coal and grain hoppers. You still see many older cars running around with lower limits, for example, 20 years ago, that maximum was 263,000 lbs, which was raised to 268,000 lbs, then the current 286,000 lbs. If you add the tare weight (light weight) and load limit stenciled on the side of the cars, you should come up to one of those totals, depending on how new the car is.

In any event, back to your question, my observation is that the light weight of aluminum cars is approximately 10 tons less than the light weight of a steel car built to the same maximum weight. For a 130 car coal train, this adds up to about 1,300 additional lading tons per train, or the equivalent of an additional 11 or 12 carloads of coal.

Scroll down to the bottom of this page... compares a stainless steel Conrail G52X to an aluminum Bethgon II. G52Xs were built new, not Coalporter rebuilds from hoppers...

http://crcyc.railfan.net/crrs/gon/gong52xproto.html

I did some digging through some photos taken over the past couple of years to compare rapid discharge cars (RD's) of both steel and aluminum design.

Southern had purchased quite a few RD's from Ortner, LD LMT - 201700#, LT WT - 78900# = 286,000 @ 3,600 cf. Keep in mind that this is a four bay RD, with a steel body construction.

CSDU (Colo. Public Service) bought extremely similar cars to Southern with LD LMT - 219600#, LT WT - 66400# = 286,000 @ 4,000 cf. This is a five bay RD from Ortner or of similar design, also built from steel.

Both Progress Energy (used to be Va. Power and Carolina Power & Light, separately) and Ga. Power, "a Southern Company", have both bought Johnstown America/FreightCar America's AutoFlood III's within the past few years. Both orders were for 5 bay RD's with a 4,200 cf capacity and are aluminim in design. The PE's (lettered PGNX) are LD LMT - 236400#, LT WT - 49600# = 286,000#. The GP's (lettered ECGX - built in 04/06) are LD LMT - 235900#, LT WT - 50100# = 286,000#. The appliances appear to be the same on both cars.

N&W's H12 class coal hopper, was a 3 bay steel car, LD LMT - 204900, LT WT - 58100# = 263,000# @ 3,570 cf.

Hope this helps.

NSTopHat

NSTopHat Wrote:
-------------------------------------------------------
> Both Progress Energy (used to be Va. Power and
> Carolina Power & Light, separately)


Progress Energy is CP&L and Florida Power, not Virginia Power. Virginia Power is Dominion.

> This weight difference
> allows that much more weight in load. Is this correct?
------------

> I doubt aluminum would allow more loaded weight per car...

But yes, it would allow "more weight in load".

On Saturday, June 10, I witnessed a trainset of new coal hoppers interchanged by CSX to NS at Knoxville, TN at approximately 8:30 a.m. They bore reporting marks of HYWX 060NNN (N = number) beginning with 06001 according to my notes. The reporting mark belongs to the Southern Company. The hopper had built dates of 04-06 and 05-06 and were built by Trinity Rail. They appeared to be of aluminum construction. Unfortunately, I did not make note of the various weight values discussed in this thread. They were 5 bay hoppers.

Something that caught my attention. Two air hoses connected each car. Each car had two air reservoirs - one for the braking system and the other I assumed for the discharge system. But stenciled on each car were the words "DO NOT HUMP" and "ROTARY COUPLER" which implied (to me at least) that each car could be used either as an air discharge or a rotary discharge.

Comments please.

NS retrieved the cars from the interchange track at about 4 p.m. same day via a yard job which I was fortunate to witness.

Mike

timz Wrote:
-------------------------------------------------------
> > This weight difference
> > allows that much more weight in load. Is this
> correct?
> ------------
>
> > I doubt aluminum would allow more loaded weight
> per car...
>
> But yes, it would allow "more weight in load".




Here's the math problem: if aluminum and steel hoppers have precisely the same interior dimensions, then they haul precisely the same amount of coal. What you are suggesting is that the aluminum hoppers have larger interior dimensions, can hold more coal and therefore more weight of the load. Or you are comparing a contemporary aluminum (and I am not a mechanical engineer, so forgive some imprecision in the language) and modern construction techniques to steel hoppers built years ago which isn't really fair.

Simply put, the edge of aluminum is that the tare weight is lower therefore the same horsepower can pull more cars, because there's less tare per car.

BobE

<if aluminum and steel hoppers have precisely the same interior dimensions, then they haul precisely the same amount of coal.>

Well, yes, that is true, but since hopper cars are built to an AAR weight standard in effect at the time they are built (ie: 286,000 lbs. currently) the aluminum cars need to be built with a larger interior dimension to handle the additional 10 or so tons they can carry. The railroads are concerned with how much total weight is applied to the car's axles, and thus railroad track, not the volume of coal or other commodity carried.

Bottom line, if modern cars are built of steel, they will weigh 286,000 lbs. when fully loaded. If they are built of aluminum, they will weigh 286,000 lbs. when fully loaded. The only difference is that because the aluminum car weighs about 10 tons less when empty, it can carry 10 tons more of revenue producing tonnage. That is why aluminum coal hoppers are so popular.

A quick look at the numbers and most Al cars are indeed slightly longer with greater resultant cube size. While this could be read as more coal/train, it probably is more importantly less cars/train for the same as a steel-only consist.

Tom H>

I believe you'll find that aluminum cars built today are approximately the same length as the steel ones (53' over coupler faces). The difference in cubic capacity is achieved by additional height (upwards of a foot) and rotating the sideposts 90 degrees, so that each side of an aluminum car can be moved outward by some 1-1/2" and still be within the Plate C dimensions.

The new RWSX 06XXX cars are equipped for both rotary and bottom-discharge service as they are likely owned by a leasing company and may be under a less-than-lifetime lease agreement to Georgia Power.

Not only does each loaded 120-car train carry about 1200 more tons per trip; each empty trip means 1200 less tons of dead weight to haul back to the mine. That probably means one additional locomotive can be shut down for the return trip, saving all the fuel it would normally burn pulling the steelies.

In regards to Ga. Power cars they are looking for a larger capacity on new cars, because western coal is not as dense as eastern coal. Meaning 1 ton of eastern coal takes up less volume that the same weight of western coal. Off hand I do not remember the exact ratio, but it is significant enough to be in the 200-400 c.f. range.

NSTopHat