4-6-4 vs. 2-8-4 question.

Hi Guys,

Great topic with much useful information!  I would like to pose a question.  There has been much discussion regarding the various steam locomotives operating day to day and under test conditions.  Much documentation has been presented. And more importantly, actual, first hand experiences have been presented.

Regarding the N&W A.....what was the full story of them not being chosen by the PRR when tested against the C&O 2-10-4 and other designs?  I have read many various reasons, with no documentation.  That is until the late Charles Meyers wrote a short article feature in the Railroad Museum of Pennsylvania magazine "the Milepost" many years ago.  He told the story of testing of both the C&O 2-10-4 and the N&W A and the reasons that the PRR chose the C&O design. 

If anyone has read this article and has additional information that they could add, please do.

There have been many articles of PRR steam being tested on the N&W and of N&W steam being tested on the PRR.  And of PRR steam being tested on the C&O.  What I would like to read is the full story with dates, routes, schedules and such of the N&W A being tested on the PRR and why it was turned down.

Steve

I believe the main reason that the N&W A did not convince PRR that it was a good choice was basically this: it was a 4-cylinder articulated locomotive.  PRR did not like this, period. 

After the tests were run PRR accepted the C&O 2-10-4 as its next standard freight locomotive, and it was a good choice.  Concurrently, PRR developed the Q1 4-6-4-4 duplex.  It was not a complete failure, nor was it a complete success either.  Later, it advanced the Q2 4-4-6-4, potentially one of the best high speed freight locomotives of all time. But....

  PRR was a 50 mph freight railroad, and the Q2 developed its best DBHP at close to 60 mph.  Not exactly a match.

The only thing I've found that to survive regarding the N&W Class A tests on PRR is a photo which can be found at the RR Museum of Pa in Strasburg, and a DBHP graph developed by PRR (both of which I've found).  The graph indicated that the A could develop something like 5,200 DBHP over the middle division, and it was not competitive with the other locomotives being considered.  If anyone has better information I'd like to know the source.  The whole thing's a mystery to me.  I've seen nothing beyond these few overall and very sketchy  figures.

I'm happy to see that others have read Charlie Meyer's articles (in Milepost??).  He was one the earliest shining lights regarding PRR's developments and how they fit into the overall scheme of things.  I hope his work will resurface again following his untimely passing in 2004, but at this point, I'm not hopeful.

Right, it's all about how much money the bean counters have to shell out for each unit.

Big Jim

Isn't that why the NS now owns the best of the former PRR.  Your bean counters were better than their bean counters? 

That may also explain why the NE corridor is now government owned. 

With the aid of the Earth's core it may be possible.

Thermal power from the core of Earth drives volcanoes and earthquakes which can certainly move objects and people at a velocity.

Fellas, this is getting silly.  If it is outside the jurisdiction of the Surface Transportation Board it probably does not belong under the heading of "Real Trains."

Maybe we should have titled this thread, which we hijacked by the way, "Back in the Day".

Did anyone other than the OP notice that one person actually did answer the OPs question? 

If anyone has any constructive criticism to add to that answer I'd love to hear it.

PRR's super hot-rod Q2 was tested by N&W in 1948.  It was no match for the

class A in the arena where N&W chose to test it.  I've been of the opinion

that those 25 duplex freighters would have a lot better off as Lima built

2-10-4s...as was originally planned.  Of course one aspect of the testing on

the Penn was the quality, or lack thereof, of the "freight coal" .  The N&W A

was, no doubt, designed for the homebrewed fuel that this bunch was famous

for.   Bon Apetite !   The Lima AMC 2-10-4,  and the Big Jay that followed

would run hot on Sunday morning's leftover pizza!

Feltonhill,

The Milepost is a magazine that is published by the Railroad Museum of Pennsylvania. Charlie Meyers articles, that I am referring to,  was in that publication.

I agree with you; there have been numerous articles on N&W steam..testing on other roads and visiting roads power on the N&W.   But I cannot locate ANY thorough documentation of the N&W A being tested on the PRR and not coming out the winner.  If the PRR was that set against 4 cylinder articulated power, then why did they make arrangements with the N&W to have the A tested in the first place.  I do not buy the argument that the PRR was dead set against 4 cylinder power.  Their Decapods won out over 4 cylinder power when they were tested against them and came out the winner.  The Keystone, a publication of the PRR Historical and Technical Society, had a fascinating, 2 part article, telling the whole story behind why the Decapods came out the winner.  That they were better and more powerful and useful than the articulateds of that era.  Oh, and one of the articulates tested was a N&W engine.

Steve

That is because your point is unsatisfactory in terms of physics.  And if you read carefully, I explained things in terms of both force and power, not just force. The work being done by both machines is equal. Its two different machines accomplishing the same task differently, but ultimately the same work is being done. 

Otherwise, what is being described is a machine that is so exceptionally superior to the other one must wonder how diesels replaced steam.

You're still missing the point, which is that although the two machines developed pretty much the same DBHP, the speeds at which their maximums were reached was far from the same.  The DBHP of the F7 maxed out at 20 MPH or less, after which it eroded fairly quickly, as did its tractive effort.  The DBHP of the A maxed out at between 40 and 45 MPH and after that was fairly flat, maintaing a high DBHP output as speed further increased. The diesel accelerated the train more quickly up to the point where its horsepower peaked, and only gradually after that.  The top speed of the A was much higher.  In the final analysis, equal work (or nearly so) was accomplished, but in different ways.

Sorry.  I think this explains the physics quite well, both in terms of force and power.

And it's not just theoretical; it's confirmed by the actual performance in the field.

You make no allowance for the difference in the speeds of maximum DBHP output.

EdKing

Maybe I can put this non-argument to rest.   N&W made a graphic comparison between the A, Y6b and 6,000 HP diesels as part of the 1952 tests.  I'll be in Roanoke next week at the NWHS archives work session. I have the sketch number,  know the location where it should be (if it survived, not all drawings did), and will make a copy of it.  The curves should show the DBPull of the diesel starting very high , then falling off rapidly as speed increases.  The A curve  wilol start at a lower figure, then decline at a lesser rate.  My guess is that the curves cross at about 25 -30 mph and above that the DB Pull curve of the A will be greater than the 6,000 Diesel. DB Pull at a given speed is what moves the train, so that should answer the question.

From what I know about F7 EMD diesels and from what I have read about the N&W A class, the drawbar HP was pretty close. The F7s were evidently rated at 6800 "net Input HP" to the generators for traction under standard conditions. (Production F7s were rated at 1750 net input.) If I use the 85.3% EMD efficiency (320/375) that EMD promoted as a calculation, the rail HP would have been almost exactly 5800, and the drawbar HP, which changes with speed due to wind resistance, etc. would probably have been 200-600 HP lower, which is what would have been required to move the locomotives. (If it was hot and at altitude, the site conditions for the diesel would have required that more "net input HP" be deducted, reducing the rail HP and the drawbar HP further. Bob Hord told me once that an A could do "5500 DBHP all day", and he was told this by Pond. And steam locomotives do not have the site derate issues that diesels do.)

Ed is correct that at low speeds, before the DBHP curves crossed, the diesel would have had the advantage. At speeds higher than that, the A would have had the advantage. I seem to remember that the average speed of both trains was about 31 mph, so for some portion of each trip the speeds might have been in the 40-50 mph range, or higher. The almost identical over the road times indicate to me that the total area under each speed-tractive effort curve is about the same.

So even though these early diesels were rated "high" for this test, a lot less HP was available at the drawbar, and it is certainly conceivable that EMD knew about the class A performance and elected to "even the playing field" a bit.

There can be no other reason for the almost identical results. (A few minutes on a freight train schedule is not very important, and certainly not as important to the RR as which motive power did the job the most cost effectively.....)

For passenger servive, minutes are "everything".

And passenger service was an area where the class A got some extended

time. Just the place to unleash more of that Horsepower at speed, although

not in the PRR, NYCS realm.  The above kinda makes me wonder what the

N&W thought of the PRR Q2 for DBHP, when they tested 6180 in 1948.

Did they use a Dyno, or just work out some rough calculations via speeds/

weight??  One thing is for certain, that big Q never got close to that 7900+

number that everyone loves to toss around !

Maybe I can put this non-argument to rest.   N&W made a graphic comparison between the A, Y6b and 6,000 HP diesels as part of the 1952 tests.  I'll be in Roanoke next week at the NWHS archives work session. I have the sketch number,  know the location where it should be (if it survived, not all drawings did), and will make a copy of it.  The curves should show the DBPull of the diesel starting very high , then falling off rapidly as speed increases.  The A curve  will start at a lower figure, then decline at a lesser rate.  My guess is that the curves cross at about 25 -30 mph and above that the DB Pull curve of the A will be greater than the 6,000 Diesel. DB Pull at a given speed is what moves the train, so that should answer the question.

feltonhill

That would be spectacularly helpful.  If we could visualize the differences it would be a great aid in understanding diesel and steam performance at variable speeds.

jayagee -

Dave Stephenson of the N&WHS obtained a lot of PRR correspondence relating to those Q2 tests on the N&W including trip logs.  I used Dave's information in a writeup of those tests in the revised book on the N&W Class A.  It's available through the N&WHS.

No horsepower ratings were given, since the dynamometer car was not used.  The Q2 was used in Kenova District coal drag service, not its best arena.  The 6180 was not in good condition when it was furnished to the N&W, and had to spend about three days in Portsmouth Shop to be made ready for service, and even then the anti-slip butterflies didn't function properly.  The Q2 was never intended for that kind of service in the first place, and it was regrettable that they didn't make a round trip or two in time freight service where it could use its horsepower to better effect.

The 7900+ horsepower claim was not drawbar horsepower, but a cylinder horsepower reading obtained on the Altoona test plant by an engine tuned up for the test.  Those who "toss it around" should realize that it is an orange that they want to compare with somebody else's apple.

EdKing 

I have a copy of the Q2 test on the Altoona Test Plant, all 159 pages of it. The summary is most interesting, with the following conclusions (among a host of others):

-The boiler was very free steaming, and Table IV under the genaral heading "Boiler Capacity" quotes a max evaporation of 137,479 lb/hour. (It also provides max evap for the T1 at 102,816 and an M-1a at 99,095).

-The clearance volume in percent for each of the four cylinders ranges from 12.6 to 15.9%. This is very high, as the steam trapped in this clearance volume at the end of each stroke does no work at all! The PRR conclusion was that "This large clearance volume has an adverse effect on boith efficiency and power, and in any redesign of the locomotive an effort should be made to reduce it."

(A reasonable number for this clearance volume is 8% and the preliminary PRR calculations were based on 8%.) A design goal was less than 6%. The PRR test engineers actually moved the cylinder compression rings outward to try to compensate for this large clearance volume, but this relocation of the cylinder compression rings closed the cylinder ports too early.

-the front engines produced 44% of the power and not the 40% design goal. (The design for the power split between the front and rear engines was based on the number of driving axles in each engine group.) The rear cylinders contributed 56% and not 60% as designed. (The cylinder sizes were different front to rear, and the front used 12" piston valves and the rear 14" in an effort to balance the amount of steam to the front and the rear engine sets based on the number of drivers and the different cylinder sizes front to rear.)

-Part of the reason for the lower than designed power from the rear engine set was the long steam delivery pipe to the rear cylinders (vs. the front cylinders), and the discovery of pressure waves in the steam supply to the rear engines as a result of the weight of 300 psi steam and its kinetic behavior. The test led to the discovery that the piston valves of the rear engines opened when the steam pressure was at a minimum. The report stated that they were not able to devlop this subject "in the time at our disposal".

-The highest drawbar horsepower developed was 7016 in test 1749 at a speed of 49.2 mph, with a cutoff of 47% and a coal rate of 3.48 lb. (This DBHP figure was at the LOCOMOTIVE drawbar and NOT the tender drawbar, so a calculation of DBHP at the rear of the tender would require deductions for wind resistance and weight and resistance of the tender. The calculation would yield DBHP AT THAT SPEED ONLY and might not be the max DBHP that the locomotive could produce.....the reason being that at a lower speed loco friction and wind resistance would be lower......

I discovered a number of things unique to the PRR Test Plant when the test setup was described.....

-The test engineers had to add a significant amount of overbalance to the drivers of the Q2, and even with this overbalance the amplitude of the locomotive at wheel speeds of 200 rpm threatened to damage the drawhead of the dynomometer. This was due to the "in-phase" and "out-of-phase" operation of front and rear engines. (Think of a 621,100 lb. locomotive (less tender) "trying to leave the building!!!)

-Evidently, PRR and its concern for its chassis dyno, did not run tests below a speed of about 35 mph. In the Q2 tests, this involved publishing a speed -tractive effort curve  with an estimate of drawbar pull at all speeds below 35 mph, and is shown on the curve by a "dashed line".....

So PRR could not determine actual performance below 35 mph using this test method!

-The "baseline" performance standard shown in much of this report is the PRR M-1a and not the J-1. Before we conclude that there was some sort of nefarious plot to "hide" an unfavorable comparison of the Q2 vs the J1 2-10-4, I have another conclusion...

The Q2 and the M1a are described throughout the report as a "high speed freight engines". I don't think, in retrospect, that the J1 was considered a "high speed freight engine", if you consider its use on C&O hauling coal, and if you remember that Harley and Hirsimaki both indicated that PRR had dynamic augment (i.e. rail pound) problems with the J1's when they were first built, and one design goal of the Q2 was to reduce dynamic augment. 

So PRR, which had many different engines tailored to specific types of service, was probably unconcerned that to different locomotive designs having almost equal power would be rostered.

-PRR ran tests on the plant at various dynamometer wheel rpm, and not based on locomotive driving wheel size, so there are tests at various dyno roller rpm, including 160, 200, 240, 280 and 320 rpm. For the Q2 test, the speed below 200 wheel rpm were discarded, due to the inability to obtain consistent readings as a result of the movement of the engine on the rollers.

Not to be overlooked in the 1952 steam vs. diesel tests is the fact that although N&W steam won by a narrow margin, it used two completely different locomotive types to do so. EMD came very close with a technology that was improving at a rapid rate, and did so using only one type of locomotive.....

This does not discredit the N&W designs, which were, as near as I can determine, two of the most highly evolved (but specialized!) designs of steam locomotives.

The PRR J1 developed track damage issues AFTER they had bee in service for

a short while, as a result of not using the latest C&O specs for the locos,

when built at Altoona.  I recall that the steel used in the equalizer bushings

and pins was a mild 1030 type steel, and not properly heat treated at the

time.  This issue was flushed out, and the offending parts replaced with a

combination of better materials and heat treat.   IIRC, later tests showed

that the Big Jay could be run up to 60+ MPH without track damage.  As for

the Penn's efforts to "hide" the J1 and it's capabilities; this comes as no

surprise.  The The Lima/AMC inspired 2-10-4  clearly blew away Altoona's

darling Q1 loco, and egos were no doubt bruised in the process.  The Q2

was among other things, an attempt to leapfrog ahead of the J1, and

whoever else might be considered as big steam competition.  FAIL! The "Q"

suffered from chassis issues, as pointed out above, plus boiler issues with

water carry over, and massive course leakage problems.  A good comparison

between the J1 nad Q2 can be had twenty years later with the SD45 and

SD40.  The 45 had a bit more power, but were high maintenance fuel hogs

compared to their little brothers...and we all know how that story ends.

There was a lot of resentment in Philly and Altoona over the J1 vs Q2

business, and it shows up in various accounts in various sources. In the

end, PRR only had one steam freighter that could even remotely compare

with the N&W's finest...it wasn't the Q !!

One thing that should always be remembered about Pennsy's "oddball" designs (S1, S2, T1, Q1, and Q2).  Even if they were 100% perfect locomotives, in the long run they would have made no difference in stopping dieselization.  They were 91 locos out of a roster of several thousand.  Consider that railroads like the N&W, DM&IR, NYC, Santa Fe, and UP had excellent designs of steam locomotives, and yet that they all succumbed to the economic advantages of the diesel.  So Pennsy's attempts should not be looked upon as failures per se, but more like a last gasp as preventing the inevitable.

Stuart

Agreed!  PRR steam didn't have a prayer once the war was over, no matter

how good it was.  The whole PRR steam infrastructure was in ruins by 1945

and the locomotives, except for a very few modern or finicky prototypes,

wern't gonna delay the big D movement for one nanosecond.  Indeed, the fifty

production TEEs would not have been built, except for the quantities of

material already on hand, and paid for, when the word from Clement came

down.

Hudson5432

Regarding the PRR Q2 - I wanted to make sure you knew about the Q2 article written by David Slee and Neil Burnell in The Keystone, Vol.43, No.3, pgs 61-74.  He alleges that the Q2 had severe water carryover problems, among others, and discusses them in considerable detail.  This managed to lower the superheat significantly and reduce the available power.   Your mention of the large clearance in the cylinders may well be another piece of the story.

In developing a system to estimate locomotive performance in the years prior to this article, the Q2 had always proved a mystery - I could never get the IHP as LOW as 7,987 at 57.4 mph.  I was always around 8,600+ at that speed.  However, lowering the superheat to reflect Slee's ideas corrected the problem.   Was there anything in the test that recorded the steam pressure and temperature at the steam chests?.  This should reflect the degree of superheat.

Also, the power imbalance toward the front engine may indicate why N&W had so much trouble with the Q2 at lower speeds and high power demand.  The front engine wouldn't keep its feet, even on sand, when the slip controls were inoperable (which was most of the time).

Thanks for posting this.  At least one copy of the Q2 test has survived for certain. I've heard rumors that another is at the RRMofPa archives but I never pursued it.

What's more telling is the simple fact that the Penn built prototype 6131 in 1944, and then without really debugging it, went after twenty five copies of the original flawed design.  If getting new power was such an issue, then why not let Lima go ahead and build the 25 2-10-4s that were already on order. Lima already had the plans.  But no, Philly had to make a point...good, bad, or indifferent! 

I suspect that if PRR had persisted, the WPB would have allowed them to build 25 locos from each builder, what with PRR's critical role as an east/ west route.  Would twenty five more J1s have saved Pennsy steam?  Nope, they were great machines...but not that great!

feltonhill,

From the summary, p.16:

"Steam Temperature

The temperature of the steam to the engines was measured where the steam passage fom the superheater header divides into branches going to the front and rear engine.....At the maximum output of the boiler, the max steam temp of the Q2 was about 735 degr F, which is the same as that of the M1a at its maximum rate, but is about 65 degr F lower than that of the T1, which produced steam too hot for good lubrication of the cylinders and valves."

"All tests were made with the water level carried at approx. 3" in the gage glass. On no occasion was there evidence of carryover. The distance from the top of the dry pipe to the water level when carried at the second gage cock is 29-3/8" and the depth of the steam space at the rear of the flue sheet is 20". The diagram, Fig 13, is a vertical section showing the relative location of the dry pipe and roof sheet with respect to water level."

"The steam space in the boiler is 285 cu ft and the water space is 1044 cu ft."

The above is the only reference to carryover, where it is explicitly denied. So unless there is other evidence to the contrary, I do not believe that the info you referenced is correct.

A friend is a member of the PRR Historical Society, and I obtain locomotive performance articles in that magazine that interest me. I have at least one article by Slee and Burnell re PRR steam, the one that summarizes the K5, and there are a number of errors that lead to possibly incorrect conclusions. I have had correspondence with Neil Burnell, a big fan of the T1. I also had several conversations a number of years ago with Charles Meyer when he was living in Colorado and working for Maxtor. He really missed the east and his beloved PRR. He asked me what I thought of the T1. I told him from my first hand conversations with Tom Harley, a good friend, the T1 was very slippery. I also told him that there were, in my opinion, two paramount reasons for the negative performance reputation of the T1. I told Meyer that one reason overlooked is that the T1s were equipped with an "air assisted throttle". I suspect that this type of arrangement reduced an engineman's "feel" for the locomotive, and that this type of throttle possibly had a significant time lag "built in".

Of course the most important reason, in my opinion, was that PRR crew assignments would be reduced by almost half if one T1 replaced two K4s, and keep in mind that crews consisted of five individuals. So I think that the T1 was sabotaged by PRR crews.....

Hudson5432,

Thanks for the info.  If the measurements were at or near full BP, that would indicate that the Q2 was producing about 315 deg SH, not bad at all.

I should have mentioned that the Slee/Burnell article was in reference to extensive over-the-road tests.  There were many reports of Q2's working water over long distances, which led to very high coal and water consumption compared to the J1's.  The principle variable I used to reduce the DBP curve was lower superheat, which seemed to work for teh road tests.

However for the test plant results, it seems now that the clearance volume and steam flow problems were likely the cause, not reduced superheat. Back to the drawing board for the test plant results.

Fun with numbers!

Ed,

I do not know what the PRR crew assignments were in the steam days, but my comment was based on what I saw on NKP. Every time I saw two Berkshires on a train, there were two cabooses on the rear. I assume that each was occupied, but in retrospect, I don't believe that I ever looked!

I agree with you that changes to cylinedr bore, or cutoff adjustments between front and rear engines, or even lap and lead changes would have made more sense. Here are the exact words:

"Examination of the indicator cards, Figs 18 to 22 incl., shows that pressure at the end of compression is too low even at the highest speeds and shortest cutoff. After test No. 1735, the main valves were changed by increasing the distance between the admission rings 1/8" and that between the exhaust rings 3/8". The object was to advance the lead and compression. Our calculations, based on an assumed clearance volume of 8 per cent, showed that this change would considerably increase the pressure at the end of compression so that with the earlier lead, the average pressure during the admission period would be higher.

When cards taken after the valve change are compared with those taken before it, it is difficult to see any effect due to the change in the valve dimensions. This can be attributed to the fact that the clearance volume, which was not measured until after the tests, was found to be higher than usual, as shown in Table VI."

What follows is a table of head end and crank end clearance volume in percent for both front and rear engines, with the front engine range from 14.9 to 15.9%, and the rear engine range from 12.6 to 14.7%.

And...

"This large clearance volume has an adverse effct on both efficiency and power, and in any redesign of the locomotive an effort should be made to reduce it."

The PRR J1 weighed 575,880 lb. and were big engines. The Q2 weight in working order (engine only) was 621,100, and were REALLY big.  (The 1952 Loco Cyc. has a weight of 619,100 for these engines. The higher weight is from the PRR Test Report.) It's too bad that a lack of attention to a few details during design and construction affected their performance.

Interesting.  N&W's class A weighed 573,000 pounds (with more on drivers than the Q2).  The 2100-series 2-8-8-2s in final form with leaded LP frames weighed 611,530 pounds.  Before, their weight was 582,900 pounds.  But neither was considered REALLY big.

Like I say, interesting.

EdKing

Ed, you know that the N&W knew that all that mattered was weight on drivers.  Anything else was simply wasted.

Stuart

You mean horsepower doesn't do anything?

OOPS!  I forgot about horsepower.

But, still, carrying excess weight on non-driving axles is not a guarantee of better performance.  The N&W Class A had both more horsepower and tractive effort than any Challenger type, and also outperformed the Allegheny, with one less unpowered axle and lower overall weight.

Stuart

Engine          Percentage of Weight on Drivers

N&W Class A 2-6-6-4           75.3

N&W Class J 4-8-4          58.3

C&O 2-6-6-6 (last series - lightest)         67.0

UP 4-8-8-4 (1st series - lightest)          70.8

N&W Y-3 2-8-8-2          90.0

N&W Y-5/6/6a/6b 2-8-8-2          89.7

EMD F7          100.0

How many F7s did it take to replace C&O H8s on Allegheny Mountain on tonnage coal trains?  Somebody tell me, because I don't know offhand.  But I'd guess it wasn't anywhere near 7498 DBHP worth . . .

EdKing

How about an A-B-B-A consist, totaling a paltry 6000 horse power?

Stuart,

The N&W A outperformed the C&O Allegheny?   How so?

Steve

hello guys and gals.........

How does the Santa Fe class # 5011 2-10-4 compared to the 4 unit ABBA F-7's in terms of drawbar horsepower and speed of the same era ?  This engine has 30 by 34 cylinders, 310 PSI boiler pressure, 121.7 SQ grate area, 74" inch drivers and working weight of the engine is 536,000 pounds (less weight) than the J-1's or Q-2's. according to the  www.steamlocomotive.com, this engine # 5011 to 5035 produced 108,961 pounds of tractive effort and no booster.  The 16 wheel tender is 24,500 gallons of water and 7,000 gallons of oil.  Pennsy leased them in sandusky, ohio in 1956. The # 5000, 5011,5017,5021 and 5030 were saved from scrap. 

the woman who loves toy trains

Tiffany

The 5011 is faster over the road, once it gets going, than the PRR J1. The Big Jay can start a heavier train.  Keep in mind that the AT&SF Texans were kept in near excellent condition prior to the PRR lease of '56. 

The PRR J1 were in terrible condition, as was all of their steam power from about '54 on.  There's a video/ DVD from Herron, which shows a J1 moving away from a stop in early '57, with the piston rod and guide jumping up and down with each power stroke; amazing the whole thing didn't just lock right up!  Rumor has it that when the 5011s were done on the Pennsy, they good for nothing but scrap.

It is a shame nobody copied what the N&W was running.  But did the Y classes evovled from a USRA concept?

I am not an engineering type, but according to what I have read on the DM&IR M4 Yellowstone they had the most weight on the drivers of any locomotive. Does that not translate into the greatest adhesion and least loss of power of the big articulated steam engines. And again I`ve read they could pull 180 iron ore cars on relatively flat terrain but with some grades at speeds of 40mph.

I have loved the discussion and with study I think I`m understanding most of the physics involved.

Thanks

Bob [merely a musician]

The N&W received 50 USRA 2-8-8-2s in 1919 (2000-2049), 45 from Alco's Schenectady Works and five from Baldwin.  These were class Y-3; themselves direct descendents of N&W's Y-2 2-8-8-2 of 1918.  With 35 years of well-thought-out refinements, these evolved into the 2100-series (Y-5/6/6a/6b) 2-8-8-2s that made the railroad a ton of money throughout their service lives.

Could be that the DMIR 2-8-8-4s hauled the heavy trains, but I'd be interested in seeing a comparison on a Gross Ton Mile per Train Hour per Dollar basis.

When you factor those nasty old dollars in there, that changes the game.  But it was the bottom line that counted.

EdKing

I'll presume to answer for Stuart, Steam Guy.

How so?  In Gross Ton Miles per Train Hour per Dollar, that's how so.

The 2-6-6-6 was more expensive to build, operate (with 260 pounds of boiler pressure, it didn't get as much out of a pound of coal or water as the A did at 300), man (its weight on drivers put it one bracket higher on the pay scale chart for engineers and firemen), and maintain than the A.  I'm willing to be convinced that its 80,000+ pound driver axle loadings were no more detrimental to track and structures than the A's 72,000 pounds, but its going to be a hard sell.  The comparative purchase figures are quoted in my book on the A, and lest you figure that the A's costs are understated, they're comparable to what the UP paid Alco for the first Challengers of 1936.

Look, Steam Guy - it's very simple.

A locomotive is merely a tool that a railroad uses to help it make money - a profit, if possible.  It's nothing more, nothing less.

Steam locomotive analysts are fond of comparing drawbar horsepower, cylinder (indicated) horsepower, starting tractive effort, boiler evaporation - in short, any statistical means to bolster the arguments for their favorites.  But factoring those evil old dollars into the equation makes a lot of impressive locomotives less so, and a lot of less impressive locomotives more so.

And when you figure the dollars in, its tough to fight the N&W's J, Y-6 and A. 

Hope this helps.

EdKing

The above kinda makes you wonder what C&O might have achieved with a revised upgrade of the H7a 2-8-8-2??  Anyway, Cleveland had to know what they were getting, at least to a certain degree, with that 1M + Lbs. worth of Lima articulated.  

A lesser locomotive may have been more profitable and more effective, if used correctly, but that would not have provided the emotional release that some of these people were seeking!  Yeah, there's big kids playing with trains, both then and now....and always will be.

And therein lies the big secret with N&W modern steam. Not only hitting the mark at the bottom line sixty years ago, but still pulling all the right emotional cords as much today as then...probably even more so. Tough to compete with N&W???? No, nearly impossible!!!!

When people talk of the Yellowstones pulling 180 ore cars, IIRC, these are little iron ore jennies that were like 1/2 a full size car....

 Other than going down into Duluth, I think northern Minnesota is relatively flat...

I guess an answer to my boiler explosion question is out too....