Discussion relating to the PRR, up to 1968. Visit the PRR Technical & Historical Society for more information.
  by AnotherPennsyNut
Could someone please provide the horsepower and top speeds of each: the K4s Pacific, the H6a Consolidation, and the E3a Atlantic. I can't seem to find them anywhere. Thanks!
  by timz
No one knows.

As for "top speed", you'd have to spell out what you mean-- not that any of us could answer even if you did. How fast could it go down a 2% grade without actually flying to pieces-- that's one possible definition, but other definitions are reasonable too.

They did put the K4s on the Altoona test plant-- they originally claimed 3184 maximum cylinder horsepower, which presumably was with hand firing. The 5399 did better, of course, and Railway Age gave road-test horsepowers for it and a conventional K4. As I recall the conventional peaked around 2500 dbhp.
  by AnotherPennsyNut
Alright. 2500's a good enough figure for me. I'm just gathering data for some vehicles I'm modifying in a game called Chris Sawyer's Locomotion. As for top speed, I would have to say something along the lines of "average cruising speed on dead flat, straight track with 3-6 cars". I doubt that information is available, you're right. Oh well.
  by Eliphaz
here is a thread that discusses steam engine horsepower.
if you have principal dimensions, you can estimate horsepower developed.
  by timz
With 3 cars on the level we might guess the E3a could manage 80+ mph, maybe 90; with 6 cars, let's say 70 or a bit more.
  by Allen Hazen
There was a very rough rule of thumb in the steam era: top safe speed for a locomotive in m.p.h. = diameter of its driving wheels in inches.

(Very rough. At the high end, well-designed late passenger engines could exceed this by a wide margin: Milwaukee Road's 84" drivered Atlantics and Hudsons were regularly operated at well over 100 mph, and there are apparently reliable reports of runs on which their speedometer needles were hard against the 120 mph peg. And I think many low-drivered freight types were ... uncomfortable ... to ride on before they reached wheel-diameter speed.)

I think the highest RECORDED speed for a K4s Pacific was just under 100 mph, for a rebuilt and modernized (with poppet valves) engine on a test train in the late 1930s: a fairly heavy train, so a bit higher with a short train would doubtless have been possible.

H6 Consolidations were built for freight service, later used largely as switchers: I doubt they got anywhere near wheel-diameter speed on any regular basis. (PRR officially deemed its I1sa Decapod, with 62" drivers, good for 50 m.p.h.; they seem to be universally universally described as "rough riding".)

E3/E7 Atlantics were built for fast passenger trains, and later in their careers would have been used mostly with comparatively light trains. At a guess they would have hit 80 m.p.h. regularly in main-line service early in their careers.
  by Allen Hazen
In a much-publicized feat, E2 Atlantic 7002, making up time with a crack express, supposedly averaged 127.1 m.p.h. over three miles of the Ft Wayne division in 1905. (The Ft Wayne division -- western part of the Pittsburgh-Chicago main line -- was the site of much of the PRR's fastest running with steam power.) There is, however, some scepticism about the accuracy of the speed measurement....