DPM pencil-pushy?

Trains Magazine Locomotives
1

Was DPM’s March 1961 editorial, Impressive But Not Convincing, on the H F Brown paper the last shot of the old steam-diesel debate?

Or is it a sleeping dog that has lain far too long?

After listing several of Brown’s contentions and leaving specific rebuttal to “more qualified pencil pushers” DPM rested his case largely on this one paragraph:

“We regard Mr. Brown’s paper as impressive but not convincing. For example, the merits of ‘modern steam power’ are better illustrated in specific applications than in over-all comparisons. It is true that Missabe Road 2-8-8-4’s moved ore trains of almost 18,000 tons gross off the range and that N&W 2-6-6-4’s managed 14,500-ton coal drags in flatland running. The equivalent, say, of perhaps three six motor, 1750 h.p. diesels. Driver axle loadings in this example range from slightly less than 50,000 pounds for the diesel to 70,600 pounds for the 2-8-8-4 and on up to 107,525 pounds for the 2-6-6-4. Clearances favor the diesel, too, as does the fact that the articulateds are indivisible. Put it this way: How many roads possess N&W’s physical plant? Again, even N&W found it necessary to manufacture two basic types of steam locomotives (simple 2-6-6-4 and compound 2-8-8-2) to operate in mountain and flat terrain on the merchandise trains that are now handled by multiples of a single type of diesel, a unit of which is also at home, say, on the Abingdon Branch, where formerly a 4-8-0 was the largest type of power assignable.”

DPM’s pencil pushing is pretty much straight arrow on the DMIR application, judging by his own Steam’s Finest Hour, p57, listing 565,000 WOD for the 2-8-8-4, and the November 1959 TRAINS on DMIR. Figure six motor units of the time commonly had 50,000 lb axle loads.

Re the N&W application, however, he is strictly pencil pushy. His own SFH, p67, lists 432,200 WOD for the Class A, which, divided by six, is actually less that the 2-8-8-4 fi

2

The N&W A averaged 72,000 lbs on each driving axle. Don’t know where DPM got his figure.

The best I can do on an estimate of a Class A’s capacity on level tangent track, at the total evaporation and firing rate N&W expected, is about 4,200 trailing tons at 60 mph. This reflects a maximum of about 5,550 DBHP at 40 mph, the usual high point on an A’s DBHP curve.

N&W rated its locomotives very conservatively, and the often quoted 5,300 DBHP is usually considered at the rear of the aux. water tank. Toward the end of steam, the A’s were developing slightly more than this in order to get 16,000-18,000 ton trains from Williamson to Portsmouth in something less than 4 hours. That’s where the 5,550 figure comes from.

There are many examples of A’s running a steady 60 mph on time freights nos. 84 and 85 (some of O Winson Link’s recordings), but I’ve not been able to directly relate a trailing tonnage figure to this speed. As a result, the above estimate is derived from Davis equations commonly used by the RR industry during the 1950’s.

3

You may want to pose that question in the “Could Steam make a Comeback” thread in the General Discussion forum:

http://cs.trains.com/forums/16/1378816/ShowPost.aspx#1378816

Several of the posters on that thread have good knowledge on the subject.

4

As you know, some freight cars are draggier than others, so nobody knows exactly what power would be needed at 60 mph, and certainly nobody knows for sure what power the A could be counted on to produce day in and day out. Could steam locomotives regularly match their test output? Maybe, but nobody has the data to say.

In any case, the claim of 7500 tons at 64 mph has never been documented. Originally (in 1936) the N&W said it was on “near-level” track, but later they said it was level, which would be unlikely.

Here’s a puzzle for you-- the 6/58 empl TT rates the A at 6500 tons Williamson to Portsmouth on “Time Freight”, except that Number 77 was not to exceed 4500 tons when hauled by any steam engine. But the “normal rating” for diesels on Number 77 was 2250 tons per unit, which would mean per GP9/RS11, or maybe even per RS3. Two GP9s on 4500 tons doesn’t sound like too fast of a freight, does it? So why was an A limited to 4500 tons?

5

Using the same estimating method as above, I changed the tonnage to 4500 and the grade to -0.022%, the average downgrade grade from Williamson to Portsmouth. The estimated maximum speed was 60 mph. An A didn’t average this speed from point to point. This is the best guess I can make as to why the A was rated at 4500 tons Wmsn-Ptsmth.

Since you raised the question, I believe that things were changing after 1958 and faster train times weren’t as important to the new management as they were to the old. It take a lot more DBHP (and $) to run 60 than it does 45, and maybe the average point to point speed wasn’t that much different. So if two GP9’s could get over the division at a maximum speed of 45 with 4500 tons, maybe that was all that was necessary to meet the RR’s standards after 1959.

6

Where did DPM get that twice cited figure in Steam’s Finest Hour of 125 cars at 60 mph?

King, Mercedes of Steam, does not quite say anything so specific, but it comes close.

Is this another bumblebee-can’t-fly proposition, if the A actually did pull large trains that fast?

Beyond any railfan trivia, there is a need to increase freight train speed economically.

Diesels cannot do it. The old steam-diesel controversy did not venture into fast, heavy trains.

7

Same tonage 1960 vs 1980 vs 2008. The big factor not considered friction bearings vs roller bearings especially starting a train.