Does anyone know the diameter of the piston valves on an original K4 Pacifc (and also an M1a)? I am researching for a comparison of the design and performance of certain interntional locomotives, including the French Chapelon 240P, which had the same power HP output as the K4, but only a 41 sq. foot firebox, compared with the Pennsy pacific's 70.
Chapelon's work on improving the thermal efficiency of the steam locotive came after the K4 was produced, but the K4 was still a highly successful locomotive, especially I deduce in terms of reliabilty and ease of maintenance. I know that some K4s were rebuilt with 15" diameter piston valves, so possibly Chapelon's ideas on improving the ingress and exhaust of steam to and from the cylinders may have not been lost on the Pennsy, even though so few were modified.
John C. Hall Does anyone know the diameter of the piston valves on an original K4 Pacifc (and also an M1a)? I am researching for a comparison of the design and performance of certain interntional locomotives, including the French Chapelon 240P, which had the same power HP output as the K4, but only a 41 sq. foot firebox, compared with the Pennsy pacific's 70. Chapelon's work on improving the thermal efficiency of the steam locotive came after the K4 was produced, but the K4 was still a highly successful locomotive, especially I deduce in terms of reliabilty and ease of maintenance. I know that some K4s were rebuilt with 15" diameter piston valves, so possibly Chapelon's ideas on improving the ingress and exhaust of steam to and from the cylinders may have not been lost on the Pennsy, even though so few were modified.
The square footage of grate area was more dependant on the type and quality of the coal expected to be burned in the fire box. It could easily account for that large of a difference. The boiler size and evaporating surfaces will give you the horsepower potential. The Pennsy experimented quite a bit on the K4 series, poppet valves, differemt types of piston valves, etc, and the Pennsy was well known for documenting these experiments.
I found Brian Hollingsworth's "Illustrated Encyclopedia of the World's Steam Passenger Locomotives" to offer interesting comparisons.
One thing consistent through the listings is that the axle loads and hence adhesive weight and tractive effort of almost anything American was about double its counterpart anywhere else in the world.
The other interesting tidbit as that the Acme of French steam, that Chapelon "A1" prototype Northern, had about half the grate area, evaporative surface, and superheater surface of any of a number of US Northern Super Power -- that includes the N&W J, Niagara, GS-4, FEF, and so on. I am making kind of a rough generalization here, and the Chapelon numbers are a bit more than half, and there is some variation among the Super Power locomotives, but this factor of about a half is a reasonable approximation.
Hollingsworth claimed that the Chapelon A1 was good for 5500 HP "in the cylinders" -- I take this to mean indicated and not net at the drawbar. But tell me, what Northern in US practice was rated any higher. So the US Northern may have had twice the drawbar pull at start, but at speed, it seemed to be rougly comparable in HP and hence in thermodynamic conversion of heat into work.
So if Chapelon was getting roughly the same peak HP out of half the locomotive (grate, evaporative surface, superheater surface), that means he was evaporating roughly half the steam and getting the same mechanical output, or he was evaporating somewhat more but was evaporating considerably more steam per square foot of everything on the locomotive. My guess is some combination of the two -- he must have been perhaps 40 percent more thermally efficient and was getting perhaps 40 percent better heat transfer across surfaces owing to a more effective drafting system.
So there is evidence of perhaps as much as a 2:1 difference in the relation between boiler size and indicated HP based on simple expansion with "standard" smokestack and Chapelon's "hot rodded" steam passages, valves, smokestack system (steam ejector), and of course, Chapelon was using compound expansion.
If GM "killed the electric car", what am I doing standing next to an EV-1, a half a block from the WSOR tracks?
The only PRR K4 diagram I have which gives the valve size indicates that it was 12". Other sources indicate that the M1-M1a-M1b 4-8-2s also had 12" valves.
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