Not to reopen that somewhat rancorous discourse we had some months ago after the Ed King article in trains, but the widely quote figure for the C&O Allegheny is 7498 HP. What is the source for that number? Why so exacting when locomotive HP is so affected by coal, water, conditions, mental state of fireman, etc.

I don't have a primary source but Eugene L. Huddleston says in his book, "World's Greatest Steam Locomotives" on page 23:

QUOTE-------------
The figures are too well know to require elaboration: 7,498 maximum drawbar horsepower for the H-8 and 6,300 for the A. These figures were derived from actual instrument reading (made in 1943 and 1941 respectively) on dynamometer cars, N&W's built in 1920 and C&O's in 1930.
END QUOTE ------------

I think the horsepower indicated is the highest observed horse power from the tests and isn't necessarily the typical horsepower obtained in normal operations.

Also, in addition to the factors that you noted, speed in relation to piston stroke and bore and driver size affects horse power as well. In a comparison between the N&W "J" and the Penn "T-1" run by the N&W using their dynamometer car in 1948. The engines used were the N&W 604 and the PRR 5511. The J produced more HP through about 60 mph then the T-1 surpassed it. The J produced it's max HP about 40 mph of 5,100 HP and the T-1 achieved it's max at 55 mph of 4600 hp.

PRR also borrowed a J, the 610, and an A to test. The J handled a 1,025 ton train at 110 mph near Crestline, Ohio, during the tests.

Ed

Closest to a primary source I can get is The Allegheny Lima's Finest, by Huddleston and Dixon, page 204, graph in upper right corner. Ed has it right from there. The 7,498 DBHP figure is a maximum reading on the scatterplot, probably a data point recorded from the dynamometer tape. If you get a chance to see the graph, note how the range of data points gets more erratic as speed increases. This is where scatterplots are really good presentations to analyze what's going on. IMO the curve drawn through the data points is optimistic above 30 mph. The sustained DBHP at 47 mph is closer to 6,600 than 7,000, still a very impressive figure. I don't know if the original test report has survived or not, but C&O Historical Society may know. I do know that C&O did not typically correct for acceleration based on other tests I have, so that may be part of the answer regarding the peak reading.

I agree that HP comparisons are always a pain. Too few will take the time to make sure that test conditions are similar, or define what HP they're talking about. This is what causes all the bad feelings in discussions (other than the usual - my loco is bigger and badder then your loco, fill in your favorite).

The N&W A max HP figure is one example of the effect of test conditions. The 6,300 DBHP reading is generally regarded as a fluke, possibly occuring when momentum was running out just past a sag. Others opine that the dyno drawbar was sticking, and that after fixing it, the 6,300 was not repeatable. Have not found the test report for this either, but as more material gets cataloged by N&WHS, it may surface.

Of course, with N&W you get into the idea of "dispatchable" HP (my term) where the RR was most interested in what could be applied to the trailing tonnage every day, not just when the crew was feeling good, or the engine was on its best behavior. N&W didn't much care about maximum figures. So, could an A actually develop 6,300 DBHP? Under conditions of high firing rate, maximum evaporation, and full flog throttle and cutoff, maybe. Wouldn't very economical, though.

The figures quoted above for the J and PRR T1 on N&W are also very accurate and agree with the curves drawn by N&W (congratulations, Ed, this rarely happens with this relatively obscure test!!!). However, if you want the absolute highest reading on the graph for the J (Chart 1 from the test report), it's 5,250 DBHP at 41 mph. Comparative figure for the T1 is 4,640 DBHP at 61 mph. Fun with HP!!

Again, not to stir up the proverbial hornet's nest-but what about some of the Pennsy articulateds? I'm not talking about the 6-4-4-6 or the T-1 4-4-4-4 (the exotic/"slippery" stuff); but more traditional-looking 4-4-6-4 (Q class?) locomotives. I seem to recall one book or magazine quote attributing horsepower in excess of 7,000.

PRR also borrowed a J, the 610, and an A to test. The J handled a 1,025 ton train at 110 mph near Crestline, Ohio, during the tests.
Interesting you bring that up as that was UPs criteria for the FEF series 4-8-4 was the ability to handle a 1000 ton train at 100 mph...............Wooly

PRR's T1, S1, Q1, and Q2 were rigid frame duplexes, not articulateds. The road had a strong averson to jointed power.

The Q2 4-4-6-4 tested at 7,987 indicated HP (measured at the cylinders, not the drawbar) at 57.4 mph. Test conditions included a very high firing and evaporation rate. This figure was obtained on the Altoona Test Plant. This figure was meant to be an absolute max number. See Railway Age, 12/22/45, pp 1014-1016, as well as Tom Harley's book on the subject.

PRR seemed to forget one thing when it ordered 25 Q2's: it was a 50-mph freight railroad. The existing J1 was just fine at speeds of 40-45-50 mph, and the extra expense of the Q2 didn't produce any noticeable gains in productivity. They were retired early, and the J1's soldiered on to the end of steam.

I think most Class I railroads viewed train sizes/speeds pretty much the same way because they were looking for the economies of scale and to be competitive in marketing except for a few railroads such as the MEC with a small customer base or N&W which considered itself as a "mountain railroad" in which grades and curves imposed technical limitations on the trains. The 1000 ton 100 mph passenger train was indicative of the general growth of train size and weight through the first half of the twentieth century. As a sort of rule of thumb, the Pacific was considered good for 400 to 600 ton trains. The Hudson was used for 600 to 800 ton trains, and the Northern type was the final expression of this growth of high speed steam, an engine that could pull a 800 to 1000 ton train at eighty to one hundred miles an hour.

Ed

A lil off the subject of the H8. Here is some infomation not many know. C&O barrowed two T1 duplex's from the PRR for two weeks in sept of 1946 ran from Huntington to clifton forge. numbers 5511 and 5539. 5511 was recalled and 5539 was sent in its place. I have a copy of the 39 page test report on the 5539 pulling the FFV. It stalled out at Cotten Hill WV on the new river div. A crew from handley had to go get her and farry her all the way to hinton. Only one picture of the 5539 was taken and you can see it at gottrains.com under C&O cabin creek pictures 1st picture at the top of the page. It was taken at Cabin Creek Jct by Arthur Hoffman


Scott

K4, I have to object in part to what you posted. The test report you refer to shows that the stop at Cotton Hill was 30 seconds, from 5:59 pm to 5:59:30 PM (pg25), not enough time to dispatch a crew from Handley, 19 miles west. Further, there are no qualifying remarks regarding that stop. Nothing untoward happened there. I believe the account you refer to can be found in the book C&O Power, ca 1965. This description was later retracted by Dr. Huddleston in his book New River Train. In that source he notes that the problem occurred in Waynesboro, VA, where the grade was 1.31%, considerably steeper than the grade at Cotton Hill. BTW, the T1 made up all of the 6-minute delay at Waynesboro by the next stop at Charlottesville. Compare test report info at pg 28 with timetables of the era. Subsequent correspondence between C&O and PRR adds additional information that is also little known. T1 5539 did not slip in the attempt to start the train, and both T1s handled C&O trains well. The test report confirms all of this. I submitted an article on this test to C&OHS last fall, due for publication in March or April. Stay tuned.

Dave-very informative answer-thanks. Now, next part of the question. When people debate which steam locomotive was the "most powerful" (to use layperson's terms), the arguments tend to center around Big Boy vs. Allegheny vs. N&W Y-class. Rigid frame vs. articulated aside, why are the Pennsy locomotives you elaborated on not mentioned in said debate?

Actually, the Q2 is often mentioned if maximum horsepower is discussed. But.... comparing indicated HP (Q2) with drawbar hp (Big Boy, H8 and Y6)is apples and oranges. I don't know of any reliable IHP estimates for those three.

PRR brings another variable to the table. When DBHP is listed for a PRR loco, it probably means a test plant value, which is locomotive DBHP. This quantity is measured at the rear of the locomotive, and excludes rolling resistance and wind resistance. It's less than IHP and greater than DBHP at the rear of the tender.

Even drawbar HP is a problem. Is it peak, average, sustainable, over the road, special test.....? Most people aren't very careful when using adjectives to define which HP they mean. In addition to all that, most powerful to some means highest starting tractive effort. That's a little more stable quantity to deal with. BTW, the VGN 2-10-10-2 usually wins this one, with something like 176,000 lbs starting in simple.

Most powerful is like asking how high is up? In spite of that, locomotives are fun, as long as nobody gets their feathers ruffled.

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