N&W A CLASS

[Anonymous]

Someone told me that the N&W A Class had more HP than the Big Boy, and the UP would of been better off ordering locomotives from the N&W instead of ALCO. Is this true, or is he just telling me a story??

keep asking keep learning

[Anonymous]

At 8000 hp, the Pennsy Q2 beat both the A1 and Allegheny. Maybe N&W should have bought from parent PRR??? I could be wrong, but I suspect the 8500 hp UP Big Blows have yet to be equalled.

[tpatrick]

There seems to be some confusion here. The N&W A class was not the Allegheny. That would be C&O's H-8. Pennsy tested N&W A no. 1218 in 1942. It was in competition with a C&O T-1 2-10-4 to determine which would be the best prototype for a new Pennsy freight hauler. According to Paul Carleton's "Pennsy Steam, a Second Look," the A-1 beat the Texan in tractive effort (114,000 vs. 108,750 without booster) and in maximum horsepower (7700 at 45 mph vs. "more than 7000").

According to Classic Trains' "Steam Glory," the Big Boy was rated at 135,375 lbs. TE and 6300 maximum drawbar HP at 41 mph. C&O's Allegheny had 110,200 lbs. TE and 7498 HP at 42 mph.

So which wins the comparison? It depends on whether you favor tractive effort or horsepower or something else. Pennsy went for the 2-10-4, rated lowest on both HP and TE. Their J class 2-10-4 was a success by any measure. U. P. wanted the hauling power of the higher tractive effort and was willing to pay the cost of slightly lower speed up the hill. It is significant that one reason Pennsy rejected the A was its relatively poor performance on hills exceeding 1%.

[Anonymous]

Ok, I took the advice of some people here who say I ask too many questions and did some searching on this subject. You guys must of made up those HP fiqures for the A and T1 because of all the sites I looked at claim the T1 made only 5100 dbhp and the A only made 5300 dbhp. In fact, I contacted the N&W Historical Society and they were nice enough to email me back. They said the A was 5300 dbhp and no more. They have no idea who and why made up those 6000 and 7000 hp figures. They said they have real test results from the N&W at 5300 hp and no more the rest is fantasy they said.

So the guy who told me that the A was more powerful than a Big Boy must of been kidding me. But I'm glad you tried to answer my questions even though you were pretending to know the answer.

[tpatrick]

You have just crossed the line from rude to insulting.

[Anonymous]

How am I insulting? I can't win. First people tell me to stop asking so many questions and do my own search. When I do that, and find out the N&W's very own historical society says something completely different than you posted, and I post their response somehow that becomes insulting???

Where did you get your answers becasue I can't find those figures anywhere. Don't pick on me. I'm sure the N&W historical society knows the right answer and if they say 5300 hp it must be true and the other sources you quote must be wrong.

keep asking keep learning

[Anonymous]

JMHO but they all could be right. IIRC Pennsy had an indoor dyno facility so the locos were tested under ideal conditions. In a Northern Pacific book I have which quotes official company performance documents, using a dyno car they often obtained very different numbers on the same engine at different times. The explanation was it depends on the fireman, the engineer running the loco and what his settings are, the weather, and the dyno car operator. I also wonder if these dyno cars were calibrated to some standard. There's also boiler hp and theoretical hp based on doing the numbers on a slide rule. Rated hp might also be the published number trainmasters use in making up trains for all conditions with the loco in less than ideal condition. And not unlike railfans, I suspect there's also bragging rights hp. The RR and builder PR departments loved running "World's _________ engine" ads [:D]

[Anonymous]

I don't see anything rude or insulting. Asking questions is a good thing and helps others.

It's difficult to compare steam engines as they were usually designed for very specific purposes and operating conditions. To say the C&O T-1 was a better engine than the N&W A or PRR T-1 isn't fair. They were all super engines for their designed railroads and purposes. The N&W A was a magnificent loco for the N&W. When tried out on the Pennsy it wasn't a good performer for them. The A was designed to burn some of the best quality coal on the N&W and the Pennsy wasn't as particular with what they burned. The A had heartburn using that grade/quality of coal and performed much less than expected. The N&W also tried a PRR T-1 and was so disappointed it cancelled the tests almost as they started. Those huge 80" drivers just wouldn't cope with the way N&W needed to operate it's passenger service.Other factors come out here too but the point is any of these engines wouldn't perform as advertised when the conditions of use changed.

Roger

[feltonhill]

A person should always ask questions; that how we learn. No one's off the mark doing that.

Discussions of locomotive horsepower generally suffer from the lack of adjectives. This thread is no different. The PRR Q2's oft-quoted 8000-horsepower is indicated horspower, measured in the cylinders, and was achieved at a very high evaporation and firing rate. The PRR's J1's 6000 horsepower +- was locomotive drawbar horsepower, measured at the rear of the locomotive on the Altoona test plant at a relatively high firing rate. The reading was not measured at the rear of the tender. The Allegheny's 7400 horsepower +- was a peak drawbar horsepower reading measured at the rear of the tender under over the road test conditions. However, if you look at the scatterplot of DBHP readings for the test, there are wide variations in the data points as speed increases. As a result, its sustainable DBHP reading is something on the order of 6600 DBHP, still a credible number and probably the highest reading ever obtained over the road. The Big Boy's 6100 horsepower rating is drawbar horsepower at the rear of the tender, and appears to be a sustainable reading based on Kratville's book on the subject.

N&W brings a slightly different slant to the table. The A's 5300 horsepower rating is sustainable drawbar horsepower at the rear of the tender using a moderate evaporation and firing rate, reflecting economical over the road operation. N&W typically did not test its locomotives by flogging them to obtain maximum readings. It wanted to know what the "dispatchable" horspower was and was very concious of coal and water usages & costs per gross ton-mile. Consequently, I know of no reliable documentation that indicates the maximum IHP or DBHP for N&W's locomotives which would be comparable to PRR's IHP and LDBHP figures, or C&O's peak reading for the H8.

So unless one knows the exact conditions of the tests, the firing and evaporation rates, what horsepower readings are being measured, and the purpose of the tests where the readings were obtained, meaningful comparison is difficult at best, and is usually impossible. Just for a little more fun with numbers, the type of evaporation must be known as well. Sounds simple, right? Well, like everything else steam, it gets complicated. Is it water from the tank, or is it total evaporation including the feedwater heater, or is it equivalent evaporation? Guessing can produce errors of 15 to 35 percent in this one factor alone.

It ain't easy being steam!!