disregard, this comment was a duplicate. stinking 504 network timeout!
Conductor_CarlI don't know how else they would have gotten a drawbar pull
Overmod I thought they relied on their plant. But didn't C&O test one at some point around when they tested the T1?
I thought they relied on their plant. But didn't C&O test one at some point around when they tested the T1?
the N&W tested a Q2 against the A but no Dynamometer car was involved.
Don't know about the C&O, but I don't know why they would. for the T1 the C&O was seeing if it was worth buying some of these basically new high speed engines as opposed to getting more J-3's. But seeing how even after all of the controversy and lawsuits the C&O would buy 15 more Alleghenys in 1948, I think they wern't interested in any other solutions for high speed freight.
It must have been N&W I was thinking of.
Lehigh Valley went far enough as to prepare a diagram for their version of a 4-4-6-4 duplex, with a little set of eight wheels probably denoting a 'water bottle' auxiliary tender. That's the only evidence I have of the idea... and I don't think LV used regular dynamometer cars in that era.
OK, initial update.
Someone pass me the crow sauce. I turned up a Web copy of the original test-plant report:
https://www.coalstonewcastle.com.au/downloads/test-resources/prr_q2_test_report_1945(dist).pdf
which clearly notes that the high horsepower figure is indicated (using a Maihak 'improved Bacharach' indicator) at 280rpm (which is where the "57.4mph" came from). Actual peak dbhp noted in the test was about 7013, at 240rpm.
Note page 18 where they discuss that considerably more 'forcing' of the boiler was possible, but give reasons why it would be pointless to 'test' such operation. (They also note that even 7000hp was stressing the capability of the contemporary Test Plant...)
Note the section about phase-antiphase oscillations being severe at lower, rather than higher, rpm. Then consider the possible effect that surge of that magnitude might have if running in 'uncertain rail conditions'...
Overmod BigJim I'm trying to figure out how my name got drug into this conversation?
BigJim
Y'all can argue and toss around your mathmatical equations all you want. As an "operator", not a "statistition", I am more concerned about over the road performance. And, that my friends, in the case of the N&W Class A and in its operating enviroment, has been well established!
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Overmod OK, initial update. Someone pass me the crow sauce. I turned up a Web copy of the original test-plant report: https://www.coalstonewcastle.com.au/downloads/test-resources/prr_q2_test_report_1945(dist).pdf
This is all really neat!
Interesting things to me are that while the indicated HP is what is usually talked about the test report compares everything with drawbar HP, so you can see where the priority lies.
Also the drawbar HP is confusing to me. Whithun quotes 6645 as the maximum drawbar HP. is that a corrected number adding in the calculated tender resistance, because that number never shows up.
The information on the power imbalance between the front and rear engines as well as the surging caused by the harmonics is really interesting. Makes me wonder how many of these issues are less to do with duplexing as a concept and more to do with the front and rear engines being two different sizes. Would a challenger type arrangement have mitigated a lot of this?
BigJim Y'all can argue and toss around your mathmatical equations all you want. As an "operator", not a "statistition", I am more concerned about over the road performance. And, that my friends, in the case of the N&W Class A and in its operating enviroment, has been well established!
Thats fair. While I think that the A is overrated (i.e. people attribute to it things that it could not actually do (6300 DBHP)), the N&W built a engine that the overwhelming majority of railroads wouldn't build and then operated it in a way that the overwhelming majority of railroads wouldn't operate, and basically got the maximum over the road performance out of that design that it was possible to.
That's fair. I think that the Big Boy is overrated too.
BigJimThat's fair. I think that the Big Boy is overrated too.
I have been of the opinion since the early days of the T1 feasibility plan that we need to restore 1218, make a proper set of Timken lightweight rods and valve gear, put Snyder pre heaters and a Cunningham circulator on her, and see exactly how good an engine results. Leaving her display-only is a crime.
BigJim That's fair. I think that the Big Boy is overrated too.
Hey, that brings us back to the topic of this thread!
I'm creeping closer to that conclusion. I understand why the corrected drawbar pull was calculated, but using that on drawbar horsepower readings that are already gaming the drawbar pull bump that increasing the grade provides when noone else that I am aware of does that seems sketchy to me.
That and the fact that people talk about how it was designed to go 80 even though there is no evidence it ever did also reeks of people assigning capabilities that it did not have.
Of course, that could be a question of if the engine was on routes and given loads that would allow it to utilize all of that, or if it is looking more like a WM challenger (which theoretically is able to make over 6000 HP, but on tests was never able to break 5000 in either drags or fast freight work)
The "80mph" represents the balancing speed of the engine, which you might think of as a kind of Vne for locomotives. You often see it expressed in rpm or rps in this context, with the corresponding 'road speed' (from drivers of known diameter at that rotational speed) understood as less important. For grins, the equivalent balancing speed for Glaze's J 4-8-4 was 540rpm...
At some point it became a Federal requirement that testing be conducted at 10% over the anticipated maximum service speed. I do not know for certain if this was a requirement during the 'golden age of steam'.
Conductor_Carl ... that are already gaming the drawbar pull bump that increasing the grade provides when no one else that I am aware of does that seems sketchy to me.
The point of testing a locomotive is to compare it with other locomotives you've tested. Naturally you want conditions to be the same for all the locomotives, but you're testing them in different places, on different grades. So you adjust the figures for each one: here is what its drawbar horsepower would have been, on level track, at constant speed X.
Theory doesn't say a WM 4-6+6-4 could exceed 6000 HP. Ralph Johnson tried to predict its power, but his calculation was all empirical -- a square foot of heating surface will evaporate X pounds per hour of steam, which will produce Y horsepower. All guesses -- based on experience, but still guesses. As he knew.
Somehow that "80 mph" got stuck to the Big Boy -- it was always in the early publicity. But no "people" with any sense have ever paid any attention to it.
Overmod The only issue is why the "6300hp" number -- with lower boiler pressure, at an early stage of development, and never remotely repeated -- keeps getting repeated.
timz Conductor_Carl ... that are already gaming the drawbar pull bump that increasing the grade provides when no one else that I am aware of does that seems sketchy to me. Nothing sketchy about it, of course. Anyone testing a locomotive should do the same. The point of testing a locomotive is to compare it with other locomotives you've tested. Naturally you want conditions to be the same for all the locomotives, but you're testing them in different places, on different grades. So you adjust the figures for each one: here is what its drawbar horsepower would have been, on level track, at constant speed X. Theory doesn't say a WM 4-6+6-4 could exceed 6000 HP. Ralph Johnson tried to predict its power, but his calculation was all empirical -- a square foot of heating surface will evaporate X pounds per hour of steam, which will produce Y horsepower. All guesses -- based on experience, but still guesses. As he knew.
Nothing sketchy about it, of course. Anyone testing a locomotive should do the same.
My issue with the compensated HP is that the drawbar pull measured is a empirical no kidding value. The compensation that is added to it is calculated using a coefficient for friction. This may not be 100% accurate. Also, if the value is not clearly called out to be based on compensated pull (as Big Boys generally isnt) then comparisons with other locomotives are skewed.
WRT the WM M-2, it is at least a educated guess to its capability. There im just pointing out a ready example of a engine that seems to be fundamentally ill suited to the road it was on, as I think that it is more likely that the length of train allowed and speed limits account for the 1000 HP miss in power during testing than the engineers being so crap that they misjudged what they were building by about 30 percent.
BigJim Overmod The only issue is why the "6300hp" number -- with lower boiler pressure, at an early stage of development, and never remotely repeated -- keeps getting repeated. I have no idea where that figure originally came from. The only person that I can think of that would know is Feltonhill. As for being repeated, you know how these things acquire a life of their own! Yet, being that it is just an arbitrary number on paper for someone to use as bragging rights, does it really matter?As I said earlier, what really matters is what happened out on the road between point A and point Z! And that, the N&W Class A had in spades...eastbound and westbound!
I have no idea where that figure originally came from. The only person that I can think of that would know is Feltonhill. As for being repeated, you know how these things acquire a life of their own! Yet, being that it is just an arbitrary number on paper for someone to use as bragging rights, does it really matter?As I said earlier, what really matters is what happened out on the road between point A and point Z! And that, the N&W Class A had in spades...eastbound and westbound!
Well, imma learn you up!
https://archive.org/details/sim_railway-age_1936-09-26_101_13/page/435/mode/1up
And
https://archive.org/details/sim_railway-locomotives-and-cars_1936-10_110_10/page/421/mode/1up
Are the articles published in 1936 announcing they built the most powerful locomotive in the world. The decade later modification of that curve down for the later, higher boiler pressure locomotives would not get a special announcement in public magazines. In this case that arbitrary number for bragging rights probably had some importance tied to it from a publicity standpoint. In general that number has significance because it is used often when people jabber about who has top trumps and is used as evidence that it is the third (or second) most powerful steam locomotive ever... when it just isn't. And finally, that number has particular importance with regards to the C&O. If the Allegheny is being specifically designed to be more powerful than the A, and the reported power level of the A is something like 900 HP above what it realistically is, that is going to really affect what you are building to. So that number has more impact than you would think.
I would be interested to see speed figures for the Seaboard R-2s (including on their 'second wind' as some of the best fast locomotives on B&O). Their 'diesel replacement' had a chassis explicitly designed for higher speed than other builders provided for heavy freight engines.
And the A's were probably faster.
I am still hoping that there is something in the NWHS archives that confirms that the last five As were built to 'compete' with the C&O M-1s in achieving high speed over the mountainous part with their version of a supertrain to Cincinnati -- that great perceived market that never appeared. Six-coupled versions of an engine proven over 110mph with one extra driver pair...
... like I said, the 'science project' restoration next after 5550, with the knowledge we have about how to forge Timken rods, and Voyce Glaze's balancing book and all the drawings for the specific Timken rod-eye forgings in the archives...
Excellent discussion, thanks
Conductor_CarlI'm just pointing out a ready example of a engine that seems to be fundamentally ill suited to the [WM] road it was on
Fans like to say, why did they buy 12-driver engines when 16-driver engines can pull more tonnage? Like the railroaders didn't know that. We have no idea why they did what they did -- all we know is, we don't know anything that they didn't know.
By the way -- when BigJim said he didn't know how the 6300 dbhp figure got started, he probably meant he didn't know what test Pond was basing his 1936 statement on. Unlikely anyone else can answer that.
All kinds of infrastructure factors also went into steam locomotive purchases.
Turntable size, lateral clearances for cylinders on double track or past sidings, or through passenger stations, track radius in engine terminals, etc, etc.
Tender size for operating distance coupled with turntable size might also be another factor impacting the length of the actual locomotive.
Driver size - is fast freight capability needed in addition to coal drag capability? Is a wheelbase of four 56-inch drivers the way to go or three 69-inch drivers the better solution for intended needs while still fitting engine and tender on existing turntables?
Lots of factors in addition to 16 drivers versus 12 drivers.
https://www.steamlocomotive.com/locobase.php?country=USA&wheel=4-6-6-4&railroad=wm#342
Interesting discussion at the attached link.
Conductor_CarlWell, imma learn you up! https://archive.org/details/sim_railway-age_1936-09-26_101_13/page/435/mode/1up
"Riddle me this Batman", according to the article, it lists the starting tractive effort at 104,500 lbs. Yet, the graph shows it to be about 118,000 lbs. Where did this figure come from? Did the N&W possibly turn the screws up to 300 psi on said test?
The 104,500 lb calculated TE at 275 psi was a fairly conservative guess. The A was somewhat limited cutoff (75% as I recall) so N&W assumed less than the usual 85% MEP.
But yeah, 118000 lb drawbar pull does sound pretty impossible with 275 psi.
Not necessarily that there were too few drivers, but it appears that the goal was to increase the overall productivity over the big ol' 2-10-0's with a higher horsepower engine (as said ol' 2-10-0's had higher tractive effort). However, on tests the challengers where only about 10% faster. When the max HP recorded is over a thousand below what baldwin ballparks it should be its pretty apperant that the routes it was put on never allowed it to really get up speed and put all those horses to work.
But you are right, the people at the WM railway knew about all of the little idiosyncrasies of their line and perhaps they went with this high HP engine as opposed to one that had greater tractive effort because the passing sidings put a hard cap on train length, or something to that effect. If that is the case then a challenger is probably the next logical step up from a 2-10-0 if the line is too curvy for rigid frame locomotives like a 2-10-4, and the WM was just taking the next logical increment up. I just don't know the line well enough to know if a lower HP Yellowstone would have been better suited or if the only way to improve was with HP.
BigJim "Riddle me this Batman", according to the article, it lists the starting tractive effort at 104,500 lbs. Yet, the graph shows it to be about 118,000 lbs. Where did this figure come from? Did the N&W possibly turn the screws up to 300 psi on said test?
So the easy thing for me to do here is just say "I think the HP is crap so why wouldn't I think the drawbar pull is crap" and call it a day, but that is boring.
Typically engines toward the end of the 1930s were able to put a bit more power down than the tractive effort calc would imply because they had a greater actual Mean Effective Pressure than the formula stated (usually mean effective pressure is that .85 which is just matched to the common 85% cutoff). Allegheny could beat its numerical tractive effort because its mean effective pressure was .94 of the total as opposed to .85. and while they didn't show the Cylinder pressures for Big Boy their actual vs calculated drawbar pull curve has the Big Boy outpulling what the calculation says it should.So the A having a mean effective pressure of something like .87 instead of the number they used in the calc (.77?) Isn't out of the question, its just impressive.
I further do not think that they bumped it up to 300 for the tests because the later drawbar pull/speed curve has the A pulling around 124,000 pounds ish, so beating this test. Finally, if you tested your engine at 300 and you know you built the boiler for 300 why not start at that? Why putz around for 6 years with 275 PSI when you have proven how capable it is at 300?.
Conductor_Carlif you tested your engine at 300 and you know you built the boiler for 300 why not start at that?
https://babel.hathitrust.org/cgi/pt?id=mdp.39015013029783&seq=593
it says riveted boilers are "not satisfactory" above 250 psi. What does that mean? Another thing us fans know nothing about.
It means that higher pressure boilers are going to be harder to build and maintain. All those bolt holes for the rivets and such are just more points for wear and failure and are going to require patching. The article looks to be looking forward to welded boilers, as most engines at the end of the age of steam were still all riveted (A, Allegheny, Big Boy, Y6B, Yellowstones).
Conductor_CarlIt means that higher pressure boilers are going to be harder to build and maintain. All those bolt holes for the rivets and such are just more points for wear and failure and are going to require patching. The article looks to be looking forward to welded boilers, as most engines at the end of the age of steam were still all riveted (A, Allegheny, Big Boy, Y6B, Yellowstones).
And welded high pressure boilers have their own set of issues. The higher the pressures the more critical the construction methods as failures are more catastrophic as the pressures increase.
Never too old to have a happy childhood!
timzit says riveted boilers are "not satisfactory" above 250 psi. What does that mean? Another thing us fans know nothing about.
To make this easier on readers, the correct page number in the magazine is 450, and the page in the Hathitrust file is 590, nowhere near where the link provided dumps you. That wouldn't be too bad except that it takes forever and a day to scroll to that page (I had to switch to thumbnail view to do it at all) and then when I get there, the page crashes when I have read only a little and I have to do it all over again.
It is not rocket science to figure out that in December 1942 there was still emerging trouble with silicomanganese and nickel steel -- possibly relating to improperly reamed and tapered rivet holes in the 'thinner' plate that gave the design weight reduction.
For fun, see if you can deduce the 'railroad' from which the accompanying table was taken. There were two railroads with 300psi 4-6-4s, but what about 4-4-2s...
Amusingly, this is also the issue of RME that has coverage of the 5-year trial of the D&H experimental welded boiler (p.258) and a CMStP&P adoption of the method (p.250) and a discussion of the 3776 class 4-8-4s (p.367).
To put the cracking observations in perspective, remember the colossal amount of 'reboilering' required for engines with clever boiler alloys in the period after 1945. The Niagaras, for example, were designed (and tested) at 290, and 'railfan sources' note that they were derated to run at no more than 265... after every locomotive in the S1 class had to have its boiler completely replaced. I never went through and made a comprehensive list of railroads that had to do this -- or that scrapped their "modern" locomotives in favor of other motive power when they began observing the practical maintenance concerns -- but it may be that someone has (perhaps at steamlocomotive.com).
There were other concerns with high-pressure construction -- see the issue reported with cracking knuckles in throat sheets on p.113, for example. The woeful ATSF 3460 class, when it got its 'reboilering', had chamber syphons put in. The only part of that I have documented is that you see them as a kind of 'palimpsest' on Santa Fe diagrams, where they were drawn in and (probably not too much later) erased. Brashear has a note that they didn't perform as expected -- I suspect the situation was more complicated, and considerably more concerning.
The boiler problem was so advanced that it induced Alco to build a whole vertical annealing facility for welded boilers by 1947... just in time for the mass abandonment of any new reciprocating locomotives. (They would then expediently scrap this, only a few years before it would have become invaluable in Alco's attempt to rebrand itself as a nuclear-technology company!)
A point to remember is that the boilers were 'unsatisfactory' as commodity items, repaired and serviced to a price, and not given the full 'attention to detail' in fabrication and finishing than, for example, modern 'replicas' have.
In that connection, Balt's comment about changing boiler design from riveted to welded construction has some 'teeth'. The folks doing the Tornado Peppercorn Pacific replica didn't pay careful attention to a couple of key components when they went from 'riveted' dimensions to welded -- and had cracks in the mud ring and a part of the boiler where two different sheet thicknesses were juxtaposed, requiring carefully-underreported cost to 'rework'...
Meanwhile, a fairly large part of the issue around boiler pressure of '300psi' or higher was that much greater economical gains in operation could be achieved by reducing exhaust back pressure than in increasing steam-chest pressure with an overly restrictive exhaust. This was exacerbated by increased issues with compression at required high-speed cutoff with the higher pressures, something that was only imperfectly beginning to be addressed by Okadee et al. when the market of concern collapsed.
I just tried the link again -- works fine, in Chrome anyway.
What none of us knows anything about is what "unsatisfactory" means -- how much more does a 300-psi boiler cost, considering everything? If a 300-psi engine performs better, is it worth the cost? Apparently some RRs thought so, some of the time.
The point is that many railroads found that 300psi for 'better thermodynamics' did not translate into either 'better availability' or 'lowest operating cost'.
Something I didn't mention is that, with the advent of 'obligatory' water treatment for modern alloy boilers, there was an increased importance on water rate, both in terms of avoiding blowdowns and conserving generated steam. The former is where some of the continuous-blowdown scam comes in; the latter accounts for putting air horns on steam locomotives.
"Conventional wisdom" -- reading between the lines -- was that any pressure higher than 300psi was rapidly noneconomical. If I recall correctly the KCS 2-10-4s ran 310psi in a comparatively lightweight boiler... but not for very many years. N&W had their experiments with up to 315psi, but even with efficient 'boosted' compounding that never (at least to my knowledge) became standard.
Keep in mind that most of the 'trouble' of higher pressure is not in the pressure in the convection shell at all. There were 'locomotive-type' boilers in oilfield service that routinely (and reasonably safely) ran 500psi for extended time. The two things that caused issues were the staybolted construction of large-area water legs, and thermal cycling of diffrent parts of the boiler. B&O reasonably happily got 350psi out of the Emerson watertube firebox, although I don't think they had an engine that could make proper use out of that steam pressure with single expansion.
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