One of the better discussions regarding steam on here–and one of the best all-time articles in Trains, in my opinion–concerns how many railroads purchased steam engines with unnecessarily-high horse power to support unnecessarily large drivers to support unused speeds.
I suppose you either know what I am referring to or you don’t. In my novice understanding of the subject, there is some criticism regarding the 4-8-8-4 Big Boys, 4-6-6-4 Challengers, and 4-6-6-6 Allegehnees. The argument goes something to the effect that UP/C&O would have been much better off using low-drivered Mallets for the uses that they were employed–slow drag movements on heavy grades. The argument further goes that the Big Boys and Challengers belonged on the open plains of Wyoming.
Anyway, I am sure someone is going to correct/refine my presentation of this argument. But, my question is, rather than talking about all the railroads who got it wrong, can anyone come up with some examples of railroads that got it right–that bought high-horsepower, high-drivered steam engines and put them to the right use.
I was reading about the Illinois Central’s Paducah rebuilds. From the account I read, the IC actually used them in fast-freight service. The Nickel Plate might be another good example. Can anyone think of an articulated example?
You got it right with Nickel Plate and even earlier than NKP, Erie’s 70 inch drivered Berks moved high speed perishables across its line. New York Central’ s Mohawks had 72 inch drivers and were so good that they upped the ante with 75 inchers on their Niagaras. Of course, being the Water Level Route, NYC could get away with that. One western road that comes to mind is ATSF who moved freight fast behind their 74 inch drivered 2-10-4s. They probably pulled some of the same reefers that wound up speeding east on the Erie. But that’s just speculation.
One note about the Erie is that eastbound trains were split in half at Marion OH, because the Berkshires could not handle the load on the hilly terrain to the east. Had the diesel not arrived when it did, Erie might have considered a heavier hauler, perhaps with lower drivers, for service east of Marion.
Gabe, who would be judging whether a particular railway got it right or wrong?
On what basis would this judgment be made?
Life-cycle cost per gross ton mile would be a reasonable basis for comparison among railways and specifications. Anyone have that information for even one of these locomotive classes?
First, does anyone know why this site is taking 1-3 minutes per level to load tonight? Getting to this thread took 4 minutes of load time on DSL. No other site is that slow at the moment.
A prime example of a high-drivered loco being matched exactly to the job would have to be the N&W Class A. Relatively light at 573,000 lbs, it carried a large percentage of its weight on the drivers, 432,350 lbs or 75.5%. It could haul time freights mile after mile at 60-65 mph. This is documented in many recordings by O. Winston Link. It could also move 15,000-16,000 ton coal trains at 35-40 mph for very high gross-ton miles per train hour (something on the order of 500,000) in regular service Williamson-Portsmouth. On the east end of the line, 17,000-18,000 ton trains were the norm from Crewe to Norfolk with one loco in late steam, with speeds reaching 40 mph or more.
I disagree with some of the arguments agains UP’s 4-6-6-4’s and 4-8-8-4’s however. After pulling Sherman Hill at 25 mph, a Big Boy could ramble at 50 plus down the other side with far less stress on its machinery or frame than say an N&W Y6.
This argument is not all mine, because there are several retired N&W men who believe that the Shenandoah Valley line would have been better served by a simple 2-8-8-2, rather than a Y6. Although the Y6’s were allowed 50 mph, they frequently were run higher than that downhill or where grades were favorable. Apparently this increased maintenance costs on both locomotive and track to some degree, although they were capable of reaching these speeds on a daily basis without “grave injury” to themselves, crew, or roadbed.
On the other hand, UP had many miles of 50 mph running, which is way past the optimum point for a Y6, which is closer to about 30 mph.
I’ll let the C&O Allegheny go for this reply. They raise a whole bunch of other arguments.
A slight correction to an earlier statistic…the Niagaras all had 79" drivers, not 75" as stated. The clearances on the river routes were tighter than on other lines, so the NYC made their Niagaras more compact, and one way was to go a shade light on the often typical 80" diameter.
As little as I know about rail history and stats (I admit), I haven’t seen any video of the Big Boy’s doubled or with pushers/helpers. That could very well be a function of my limited exposure, but I have also not seen any still photos taken showing anything but the solitary leviathan doing its job on Sherman or anywhere else it was put to task. In that respect, it seems to have all been figured out pretty well.
My favourite engine, the Y6b, is often filmed doubled at the head end, and there was often a pusher at the rear with a trailing wooden caboose. Were the grades more demanding, and the loads, too? I would guess they’d have to have been because the much smaller Y-Class Mallets outperformed the Big Boy in tractive effort by a country mile. Even the mighty Allegheny H-8 (2-6-6-6, not 4-6-6-6 as described at the outset above) was shy on the Y6b. The H-8 was far larger, the heaviest of all Class 1 steamers, and was reputed to produce over 6000 hp at speed. I have yet to read a “review” of the H-8, and would be very interested…so, please, feltonhill,…
Yes, Crandell, the presentation of the N&W steam that I saw yesterday showed several trains with double-headed + pusher Y6b’s. I don’t remember just where they were running, but what I remember that was east of Lynchburg (though it may have been east of Crewe) was shown with a single locomotive. West of Lynchburg, and on to Williamson you definitely have a few noticeable grades which call for more power. Of course, on my way from Cincinnati to Norfolk on the Powhatan Arrow forty years ago next month, I did not notice them, except when going up to the Big Elkhorn tunnel. That grade was noticeable because we overtook and passed a coal train–and we passed its (diesel) engine inside the tunnel; the freight engine was rather noisy.
The IC was well suited for steam powered fast freight, with relatively flat lines with few curves. IIRC, the Edgewood cut-off from Kentucky to central Illinois had a maximum gradient of 0.3%.
Robert Le Massena’s article in the June 1968 Trains specifically stated that the UP operated the Big Boys at near optimal conditions. It is true tat they did spend quite a bit of time slogging up the grade to Sherman Summit, but there was plenty of opportunity for them to stretch their legs. Also bear in mind that the Big Boy’s DBHP peak occurred below 40 MPH (slightly over 6,000 DBHP) and they were capable of producing over 5,000 DBHP at 20 MPH. In other words, if you didn’t let the train go much below 20 MPH, you would be getting close to maximum power output from the engine and close to maximum gross ton-miles per train hour.
The C&O probably would have been better off with the Y6b than the H-8. For pulling a coal train up a grade, the Y6b had considerably less weight not on drivers and produced a higher percentage of peak power at the speeds typical of coal drags.
Ed King did claim that the AT&SF might have been better off with the Y6b over parts of the line as compared with their normal freight power. One reason for this was that the Y6b used less water than the typical Santa Fe power, and water was in short supply on the line.
Erik
P.S. I couldn’t access the Trains Magazine forum for several hours today, repeatedly got loading errors.
Fair enough, I am using an inappropriately pejoriative term of “right” and am assuming the accuracy of the paradigm expressed in the article and forum discussions that I only vaguely remember.
But, my understanding of the judgment was why use a 4-8-8-4 with 70+ inch drivers when you could use something with 66-inch drivers to more cheaply do the same job.
Oh RWM! Wouldn’t it be nice to see some numbers like that?! I suppose they exist… somewhere…
On the rest of the debate, though, there are at least two things – if not more – which come to mind. First, and perhaps the more important, is that it isn’t just driver diameter which is important here. Steam engines were an incredibly complicated series of compromises, and I have often thought that the question of ‘right’ was much more happy accident than anything else. Leaving out all the messy compromises regarding boilers, fireboxes, and grates (and superheaters and and and…) the rotating and reciprocating machinery was always a set of compromises between driver revolutions per minute, reciprocating weights (valve gear, side rods, main rods, pistons, etc.), available balancing space, and desired tractive effort, among other things. Springing and equalizing get in there too. If the mechanical engineers designing a particular chassis got things right, even relatively low drivered (say 69" – 70", e.g. N&W J class Northerns, the Challengers)(The Canadian Pacific Selkirks – 2-10-4 on 63" drivers – w
PS… an intriguing thought occurs to me. Other than the rather obvious point (if it works, don’t fix it) applied to the ‘conventional’ steam engine, one is inclined to wonder what would have been the result of trying a high speed/high power steam engine using an inherently balanced system of valves and pistons and shaft and gear drive – not, perhaps, unlike a Shea or Climax on steroids?
OK, so you are the chief engineer for ABC railroad and you need some new engines. You also have responsibility for upgrading existing power and decreasing maintenance as you are well aware of the maintenance costs. So you have a choice of say an engine with 66" drivers or one with say 72" drivers. Being an engineer you know that the 66" driver travels 207.24" for each revolution of the wheels and the 72" driver travels 226" for each revolution of the wheel ( diameter x pi). That means that for every 11 revolutions of the 66" wheel the 72" wheel will make ten revolutions. Will that reduce maintenance? Probably due to less wear and cycles. Now what makes 72" drivers possible today when you had 66" drivers before? How about better boiler steels allowing higher pressures, superheaters that are more efficient, general improvements in materials throughout the engine, roller bearings, etc. So yes that brand new engine on a straight and level track with nothing to hinder it will be capable of higher sustained speeds at the same number of revolutions so you advertize to the puiblic information they can relate to. In reality what you are doing is decreasing maintenace to keep the same speeds while reducing steam and fuel consumption and making your railroad operate more efficiently. Besides those tight curves that have speed limits prevent you from running faster any way as does the number of meets you need to consider. And you get to keep your job for awhile longer. Simplified? Very much but basically those are the kinds of decisions that needed to be made and why super power was purchased and used in drag service.
In a discussion over on the Steam & Preservation Forum last week, under the “top 5 4-8-4s” thread", I referred to the article on “The American 4-8-4” by Brian Reed in Locomotives in Profile (Volume Two, published by Doubleday & Company, Inc., New York, 1972, and Profile Publications Limited, Windsor, Berkshire, England, 1972, pp. 169 - 192). In Reed’s review of top speeds there, he wrote something to the effect that even in the late 1930’s it wasn’t fully appreciated that a locomotive’s top speed wasn’t tied too closely to the driver diameter. I’ll try to remember to look that up again tonight and post the pertinent excerpt.
There is an automatic assumption among many rail enthusiasts (and the trade press historically, which ought to have known better), that faster is always better. It rarely is.
On the cost side, from a network operations point of view, what matters is consistency and reliability. A single train attempting to move faster than all the other trains either stops all the other trains to clear its path, or cannot move faster than all the other trains. Fast trains are undispatchable on almost every railway line. Speed also incurrs heavy fuel costs, track maintenance costs, and mechanical maintenance costs. And it rarely provides significant savings in locomotive capital expense, car capital expense, and labor.
On the revenue side, merchandise customers worry about business days and inventory costs. For merchandise, transportation costs are in the 1-10% or less realm of the shelf price. They will pay for speed. Bulk customers care much less about inventory costs and much more about transportation costs. For them, transportation costs are in the 75-95% realm of the CIF price. Because speed costs money, bulk customers will not pay for speed. A railway company that has both types of freight on the same line will seek to split the difference as much as possible, speeding up the bulk and slowing down the merchandise, to obtain a railway line that’s dispatchable. If we look at almost any railway line with both types of freight, historic or present, we see locomotive purchasing and assignment practices that reflect this desire to try to keep everything moving within an acceptable diversity around the mean, using low-drivered locomotives (but not too low) for the bulk freight in order to get as much tonnage onto the drawbar as possible (and thus save crew costs), and high-drivered (but not too high) for the fast freight to provide make-up capacity for delays and to operate when possible at the upper end of the speed band available t
Can anyone explain in simple terms the components of ROW maintennace costs, as it pertains to the driver heights? Obviously, higher speed costs more in maintaining ROW, but how does the driver side affect it? The early discussion of revolutions and distance helped, but it is a little fuzzy.
Driver size/ diameter, by itself (not number of wheels or weight on each, rigid wheelbase length, etc.) does not affect the ROW maintenance costs too much. The primary effect of a larger driver is to increase the contact area with the rail head proportionately with the increase in driver diameter. Increasing the contact area deceases the contact stress approximately in an inverse ratio, which is a good thing. For example, going from a 72" diameter driver to an 80" driver is an increase of 8 inches or 11 %, which decreases the contact stress commensurately, to about 90 % of what it would be with the 72" wheel.
Contact stress affects MOW costs mainly in the various forms of rail wear, chiefly “shelling” - the peeling of the top surface of the rail that results from metal fatigue and plastic flow that is caused by repetitions of high contact stresses. It is a non-linear, “threshold”, straw-that-breaks-the-camel’s-back kind of effect - small increases in the contact stress don’t cause much additional cost up to a point, but once a certain value is reached, the increase in wear and cost is dispropotional to the last small increase in contact stress. (A separate discussion has been had here some time ago about how with the increase of gross car weights from 263 to 286 and now to 315,000 lbs., this characteristic can wreak havoc with rail life and costs. It becomes a battle between the sales and operating departments - who make and save money, respectively, and so think it is wonderful - and the MOW / engineering department - which incurs more costs, a
[quote user=“Railway Man”]
[snip] On the cost side, from a network operations point of view,what matters is consistency and reliability. A single train attempting to move faster than all the other trains either stops all the other trains to clear its path, or cannot move faster than all the other trains. Fast trains are undispatchable on almost every railway line. Speed also incurrs heavy fuel costs, track maintenance costs, and mechanical maintenance costs. And it rarely provides significant savings in locomotive capital expense, car capital expense, and labor.
On the revenue side, merchandise customers worry about business days and inventory costs. For merchandise, transportation costs are in the 1-10% or less realm of the shelf price. They will pay for speed. Bulk customers care much less about inventory costs and much more about transportation costs. For them, transportation costs are in the 75-95% realm of the CIF price. Because speed costs money, bulk customers will not pay for speed. A railway company that has both types of freight on the same line will seek to split the difference as much as possible, speeding up the bulk and slowing down the merchandise, to obtain a railway line that’s dispatchable. If we look at almost any railway line with both types of freight, historic or present, we see locomotive purchasing and assignment practices that reflect this desire to try to keep everything moving within an acceptable diversity around the mean, using low-drivered locomotives (but not too low) for the bulk freight in order to get as much tonnage onto the drawbar as possible (and thus save crew costs), and high-drivered (but not too high) for the fast freight to provide make-up capacity for delays and to operate when possible at the upper end of the speed
[quote user=“Railway Man”]
[snip] On the cost side, from a network operations point of view,what matters is consistency and reliability. A single train attempting to move faster than all the other trains either stops all the other trains to clear its path, or cannot move faster than all the other trains. Fast trains are undispatchable on almost every railway line. Speed also incurrs heavy fuel costs, track maintenance costs, and mechanical maintenance costs. And it rarely provides significant savings in locomotive capital expense, car capital expense, and labor.
On the revenue side, merchandise customers worry about business days and inventory costs. For merchandise, transportation costs are in the 1-10% or less realm of the shelf price. They will pay for speed. Bulk customers care much less about inventory costs and much more about transportation costs. For them, transportation costs are in the 75-95% realm of the CIF price. Because speed costs money, bulk customers will not pay for speed. A railway company that has both types of freight on the same line will seek to split the difference as much as possible, speeding up the bulk and slowing down the merchandise, to obtain a railway line that’s dispatchable. If we look at almost any railway line with both types of freight, historic or present, we see locomotive purchasing and assignment practices that reflect this desire to try to keep everything moving within an acceptable diversity around the mean, using low-drivered locomotives (but not too low) for the bulk freight in order to get as much tonnage onto the drawbar as possible (and thus save crew costs), and high-drivered (but not too high) for the fast freight to provide make-up capacity for delays and to operate when possible at th