sgriggs charlie hebdo sgriggs UP FEF2 (Best of the UP 4-8-4's by virtue of its higher performing Type E superheater) Milwaukee Road S2 (Seldom-mentioned type, fully qualified based on boiler & running gear specifications) Along the lines of Overmod's question: Why UP FEF2 rather than FEF3? Why MILW S2 instead of S3? UP FEF2 was built with Type E superheater, rather than Type A as built on FEF1 and FEF3. The Type E superheater was a more advanced design than the Type A, and nearly all late steam designs used the E rather than the A. Although I can't put my hands on it at the moment, I have seen references stating the type E produced higher superheat than type A. Higher superheat translates to more efficient steam use in the cylinders and more power. If you compare the specifications of the Milwaukee S2 and S3, you will see that the S2 has a much larger boiler, a higher operating pressure (285psi vs 250psi), the same size cylinders, and the same size drivers. The S2's were thoroughly modern engines with cast steel locomotive beds and roller bearings. Scott Griggs Louisville, KY
charlie hebdo sgriggs UP FEF2 (Best of the UP 4-8-4's by virtue of its higher performing Type E superheater) Milwaukee Road S2 (Seldom-mentioned type, fully qualified based on boiler & running gear specifications) Along the lines of Overmod's question: Why UP FEF2 rather than FEF3? Why MILW S2 instead of S3?
sgriggs UP FEF2 (Best of the UP 4-8-4's by virtue of its higher performing Type E superheater) Milwaukee Road S2 (Seldom-mentioned type, fully qualified based on boiler & running gear specifications)
Along the lines of Overmod's question:
Why UP FEF2 rather than FEF3?
Why MILW S2 instead of S3?
UP FEF2 was built with Type E superheater, rather than Type A as built on FEF1 and FEF3. The Type E superheater was a more advanced design than the Type A, and nearly all late steam designs used the E rather than the A. Although I can't put my hands on it at the moment, I have seen references stating the type E produced higher superheat than type A. Higher superheat translates to more efficient steam use in the cylinders and more power.
If you compare the specifications of the Milwaukee S2 and S3, you will see that the S2 has a much larger boiler, a higher operating pressure (285psi vs 250psi), the same size cylinders, and the same size drivers. The S2's were thoroughly modern engines with cast steel locomotive beds and roller bearings.
Scott Griggs
Louisville, KY
I interpreted "Top 5 4-8-4s" to mean my personal favorites, not necessarily the best. The FEF3 and S3 made my list because they both still exist and I have seen them run.
In my opinion, the effect of imposed pressure will limit, rather than exacerbate, formation of DNB film on affected surfaces, so in a sense there isn't much objective reason to plot the associated curves ... or to design boilers that can flirt closer to DNB in any component in normal operation.
I doubt that any 'conventional' Stephenson locomotive boiler approaches DNB in its usual components, and my analysis would be little different from yours. What I was referring to would be a fairly limited set of areas in large boilers equipped with multiple chamber syphons, specifically like those ATSF had diagrams for in 1947, and then quietly replaced. Since circulation patterns in such things are cheerfully drawn by the Nicholson people, but the actual water may not always follow those patterns as expected (perhaps in the presence of acceleration/braking or vibration, for some period of time) there may be a mismatch of where the fireside plume is producing high heat transfer at the inner waterside face and what the actual circulation at that point is providing.
That is not, of course, to say that it actually, or even repeatedly, would provide either short-term or runaway DNB at that point. Only that it can, and if it does the results are highly likely to be catastrophic in the cab.
I am almost completely certain that the 'detonation' of C&O Allegheny 1642 was due to the effect of low water complicated by the action of syphons doing just what Nicholson advertised as a 'safety feature'. At least part of the crown and perhaps some portion of the upper sheets was substantially exposed (leading to rapid plate heating) while the Nicholsons cheerfully pumped gouts of water over the exposed plate in nearly as perfect the wrong kind of random pattern as could be devised to quench the plate repeatedly to failure. Or perhaps more appropriately stated, quenched parts of the plate while leaving stochastically determined adjacent parts in full Leidenfrost/Eisenhoffer isolation even under boiler pressure.
Ah, understand terminology now. Everything I have read and understand suggests the only way you are likely to see critical heat flux on the water side of a steam locomotive heat transfer surface is if that surface is not adequately covered by water (i.e. running with low water over the crown sheet). In that case, there is not enough water depth to carry away steam bubbles that form at the surface via buoyancy forces. In the case of a circulator or siphon, the surfaces are nearly all vertical or inclined, and because of their position in the boiler, they should always be well below the water level (if the circulators or siphons are not submerged, the crown sheet is completely uncovered and the circulators are the least of your problems!).
I did some calculations which suggested to me that a steam locomotive water side heat transfer surface should never approach the critical heat flux point.
I've tried to attach the classic boiling curve for water. I realize this curve is for 1 atm. I have searched for curves at higher pressures and was never able to find anything. The Y axis shows heat flux in W/m^2, which is convenient, because Ralph P. Johnson's book "The Steam Locomotive" provides typical evaporation rates for direct heating surfaces such as firebox side sheets, crown sheets, circulators, etc.
Johnson gave evaporation rates of 55, 80, and 125 lbs water/sq ft/hr for direct heating surfaces. The 55 number came from Professor Goss' Coatesville tests in 1912, and represents a very conservative rating, while the 80 value represented what could be expected from a modern locomotive at a reasonable firing rate. The 125 lb/sq ft/hr rate is applicable for very high capacity firing (on the order of 150-200 lbs coal/sq ft/hr firing rate).
You can use the latent heat of vaporization of water to convert the Johnson evaporation rates to heat flux values in W/m^2, which can then be compared with the boiling curve. Below is a table with the results of these calculations:
What I infer from this is that even at direct heating surface evaporation rates consistent with 200 lb/sq ft/hr firing rates, the heat flux is considerably under the critical heat flux point. Therefore, the only way I can see approaching the critical heat flux point would be if the water side surface was uncovered.
DNB='really really bad ju-ju' in any water cooled reactor... Design criteria is that nowhere in the reactor will heat flux exceed 1/3 of the DNB limit.
TOF = "time of flight". In this context how long it takes a particle of carbon carried in the combustion plume to get from some point along its trajectory (where it reached a level of incandescence where heat transfer to the radiant section and hence the boiler water becomes net positive) to the point where it is generally accepted to leave the radiant section (ideally, where convective heat transfer becomes more effective than radiant).
DNB = 'departure from nucleate boiling', where heat transfer across the sheet or flue becomes so great as to cause film boiling. Steam is a good insulator, so for high heat transfer rates this can cause runaway heating of the underlying plate to produce Leidenfrost/Eisenhoffer effect even under pressure. Two of the things a LaMont waterwall firebox is supposed to do are keep the water speed very fast past the waterside metal and then arrange for very quick steam separation at the end of the circulation path, ideally giving much better radiant heat transfer out of the gas and into the steam.
Overmod sgriggs In terms of boiler evaporative capacity, direct heating surface (firebox walls and circulators) is approximately 6 times as effective as indirect heating surface (tubes and flues) on a lb evaporation per sq foot basis. The 3765 would be a more capable machine. I suspect the Santa Fe made the change because they felt the performance gain afforded by the additional siphons in the 3765 class did not justify the additional maintenance. This is precisely the sort of answer I like to see. There is a bit more to radiant uptake in syphon or circulator area that might not have been fully appreciated by some steam designers: the 'available' heat that follows Stefan-Boltzmann fourth-power-of-temperature absorption depends to an extent on luminous flame (which in both coal and oil firing means actual bright carbon in the plume). Problem with lots of uptake area configured to optimize internal water circulation, as with both syphons and tube circulators, is that they are cold as well as black as night to the plume, and with the TOF in a typical plume 9almost wholly at subatmospheric pressure combined with relatively high mass flow) once the glowing carbon quenches it may not be able to reach high luminosity before it hits the rear tube sheet or enters the tubes and 'goes out' to form soot. Conversely there may be so much heat in the plume in certain regions that some forms of circulator could encounter DNB leading to high spot overheating associated with mechanical stress from thermal distortion. You may recall that the 3760 class had a boiler design as late as 1947 that involved double chamber circulators (I don't remember if they were syphons and think they were only tubes). That boiler was not retained, and although documentation, at least that I have seen, is not very specific about the reason for that, the removal of the revised boiler despite its nominal great steam-generation advantages speaks to fairly dramatic practical 'issues'.
sgriggs In terms of boiler evaporative capacity, direct heating surface (firebox walls and circulators) is approximately 6 times as effective as indirect heating surface (tubes and flues) on a lb evaporation per sq foot basis. The 3765 would be a more capable machine. I suspect the Santa Fe made the change because they felt the performance gain afforded by the additional siphons in the 3765 class did not justify the additional maintenance.
This is precisely the sort of answer I like to see.
There is a bit more to radiant uptake in syphon or circulator area that might not have been fully appreciated by some steam designers: the 'available' heat that follows Stefan-Boltzmann fourth-power-of-temperature absorption depends to an extent on luminous flame (which in both coal and oil firing means actual bright carbon in the plume). Problem with lots of uptake area configured to optimize internal water circulation, as with both syphons and tube circulators, is that they are cold as well as black as night to the plume, and with the TOF in a typical plume 9almost wholly at subatmospheric pressure combined with relatively high mass flow) once the glowing carbon quenches it may not be able to reach high luminosity before it hits the rear tube sheet or enters the tubes and 'goes out' to form soot. Conversely there may be so much heat in the plume in certain regions that some forms of circulator could encounter DNB leading to high spot overheating associated with mechanical stress from thermal distortion.
You may recall that the 3760 class had a boiler design as late as 1947 that involved double chamber circulators (I don't remember if they were syphons and think they were only tubes). That boiler was not retained, and although documentation, at least that I have seen, is not very specific about the reason for that, the removal of the revised boiler despite its nominal great steam-generation advantages speaks to fairly dramatic practical 'issues'.
Overmod,
You'll have to forgive me, but can you define the acronyms 'TOF' and 'DNB'?
Scott
sgriggsThe Type E superheater was a more advanced design than the Type A, and nearly all late steam designs used the E rather than the A. Although I can't put my hands on it at the moment, I have seen references stating the type E produced higher superheat than type A. Higher superheat translates to more efficient steam use in the cylinders and more power.
That the FEF3 returned to the type A configuration (considering the way UP intended to use these locomotives) may give you a guide to the issues with the type E on large engines run for relatively long distance at high speed. The E design had higher heat transfer, but remember that the Superheater Company formulae for proportioning superheater area in that era did not include superheater dampers, so at high speed the superheat even at 'efficient' mass flow could run crazily high, beyond what any contemporary cylinder oil could handle without starting to coke.
Meanwhile, of course, the useful enthalpy for expansion per degree of superheat is not all that great; by far the most important contribution of Schmidt superheating is reduction of various kinds of condensation during the important parts of expansive working. While it can be nice to have a few extra "free" BTU/joules from heat otherwise 'wasted' in the exhaust, once you've accounted for nucleate condensation up to working cutoff you start encountering reversible volume problems that complicate compression effects AND excessive exhaust-tract steam volumes in the wrong ways if you have too much superheat in the steam.
Part of the reason why jacketing is much more effective than 'more' superheat in the inlet steam can be seen in some of the physics associated with wall condensation. Only something like .007" of wall metal actually cycles between superheated and exhaust steam, and while it's theoretically practical to 'really' overheat the metal so it cycles up and then stays above where nucleate condensation starts in the expanding steam at any given point in the effective stroke, in my opinion it's easier and better to heat up the cylinder itself (or at least the part of it adjacent to the bore and heads) so that the actual cycling removes less superheat from the steam.
sgriggsIn terms of boiler evaporative capacity, direct heating surface (firebox walls and circulators) is approximately 6 times as effective as indirect heating surface (tubes and flues) on a lb evaporation per sq foot basis. The 3765 would be a more capable machine. I suspect the Santa Fe made the change because they felt the performance gain afforded by the additional siphons in the 3765 class did not justify the additional maintenance.
very fine analysis [quote user="sgriggs"]:
Here is my top 5:
N&W J (Huge boiler, clever and unorthodox approach to running gear design)
ATSF 3765 class (Perhaps the only other 4-8-4 that could match the N&W J's physical specifications and peak output)
NYC S1a (The 4-8-4 optimized for very constrained Northeast loading gauge and NYC track pans)
UP FEF2 (Best of the UP 4-8-4's by virtue of its higher performing Type E superheater)
Milwaukee Road S2 (Seldom-mentioned type, fully qualified based on boiler & running gear specifications)
[/quote above] Thanks for putting the matter straight as possible, in my opinion.
A similar comparison can be with the various 2-10-4's, with the AT&SF tops, and the PRR-C&O next, but C&O before PRR if you value the booster, then Missabi, and then T&P, but all great locomotives. And then we can look at 4-6-6-4s. Were the last of the UP\s the best? New threads?
Overmod Why 3765 and not 3776 class? Please be specific because the small details here become important (to us motive-power nerds at least!)
Why 3765 and not 3776 class? Please be specific because the small details here become important (to us motive-power nerds at least!)
Direct heating surface was significantly reduced on the 3776 class, compared to the 3765 class (ref http://steamlocomotive.com/locobase.php?country=USA&wheel=4-8-4&railroad=atsf). In terms of boiler evaporative capacity, direct heating surface (firebox walls and circulators) is approximately 6 times as effective as indirect heating surface (tubes and flues) on a lb evaporation per sq foot basis. The 3765 would be a more capable machine. I suspect the Santa Fe made the change because they felt the performance gain afforded by the additional siphons in the 3765 class did not justify the additional maintenance.
sgriggsUP FEF2 (Best of the UP 4-8-4's by virtue of its higher performing Type E superheater) Milwaukee Road S2 (Seldom-mentioned type, fully qualified based on boiler & running gear specifications)
I have just joined this discussion as this has always been my favorite class of steam locomotive from when I was too young to understand different classes. First, I would like to say that unless we can line up these locomotives today and have some type of pull of or timed trials we can speculate all we want. That being said we do have a number of examples still left in operating order that some type of steam off could be arranged. More interesting to me is how only one Class I railroad has bothered to maintain its legacy as it was steam that powered the greatest challenge to our democracy has faced during WWII. Personally, I grew up along the North line of the C&NW railroad so I like the H-1s. Also I like FEF, but all the Northern class locomotives were the peak of locomotive engineering and it took a few decades for single unit diesel power to catch up. It was the costs a frequency of maintenance that killed steam power.
I suspect a place should be provided for the Timken 'Four Aces' locomotive, probably far more important than the A-1 Berkshire in the evolution of modern steam -- and far, far better-looking, too. It's certainly the one most regrettably lost to preservation.
Seeing as there has been a resurgence, here is my top list:
SAR Class 25 (Condensor) such as 3511 “FREIDA”. What other Locomotive can attain speeds of 65-70 MPH whilst reusing the steam multiple times to avoid water stops? Oh, and did I mention it sounds like a jet engine rather than a steam engine. For a cape gauge engine, their 234 ton weight was massive. They ran at 225 PSI with a tracktive effort slightly over 45,000 (compare that to a D&RGW K-36 which can hit maybe 30 MPH with 36,000 pounds of tracktive effort).
SAR Class 26 RED DEVIL, literally a Class 25 (non condensing) rebuilt by Wardale in the style of the famous L.D. Porta, to be even more effective. It features a Gas Producer system, lempor exahust, Power reverse, and many other improvements and modifications, however the South African Steam age was already drawing to a close. Fast forward to 2018, and 3450 has just been returned to working order in signature red paint.
Of course one must then agnowledge at least 1 of the “traditional classics”,
SP GS-4 4-8-4, such as the famous No 4449, all that glory and power, and the other usual reasons.
Canadian Pacific K-1-a, everyone knows the CP H Class ”Royal Hudson’s”, but few are familiar with the big brother, the 4-8-4 variants, No 3100 and 3101, both of which spent time semi streamlined, and streamlined with smoke deflectors. They have 75” drivers and 60,798 pounds if tracktive effort, operating at 275 PSI (sure it isn’t 300, but this was 1928). They weighed in at more than 350 tons, sadly too much for some CP Rails, which limited their operational availability.
The great SAR 520 Class 4-8-4 (similar to a T1 nose wise), with the original being named SIR MALCOLM BARCLAY HARVEY, and being 1 of 2 preserved, and a noted preservation star,sadly curtailed by diminishing Broad gauge (5ft3) in South Australia. This class of loco even gained entry into the Thomas & Friends Series, as “SHANE”, despite still have the “SIR MALCOLM....” nameplates on the side. These locomotives could actually burn coal and oil. Their 66” drivers were fairly small compared to other American engines, but they were well suited for reasonable speed and climbing in the shallow gradients.
Essentially any 4-8-4 that isn’t N&W 611......
Farrington may not have been an engineer, but I have to hand it to him for getting his hands on real engineering test data from the Santa Fe and then publishing it. If most decent-size railroads possessed test data on their steam locomotives at one time, very little has found its way into the hands of latter day students of steam locomotion.
It pays to remember that Farrington was something of an amateur enthusiast, more a duck hunter than a technologist. I remain unsure whether his coverage of the WM M-1 (in 'Riding the Locomotive Cabs') actually represents a superior design of late 4-8-4 otherwise rather pathetically underdocumented or just the presence at hand of good comparative data for the 4-8-4 and 4-6-6-4.
All this discussion and no mention of the seminal 242 A1.
And what's wrong with the Q4s?
If I remember correctly, the one thing that stuck out in my mind reading Farrington's book was that he wasn't happy that he had to stand up while riding on the N&W J. Poor guy! I wonder how much that affected his rating?
.
Top 5:
C&NW H-1
CMStP&P S-3
CB&Q O5-B
UP FEF-3
CRI&P R-67
The 2900's have to be right up there from the Santa Fe. They were designed to run 90+ MPH with a 20 car passenger train and did haul those during the war. They also grabbed freight trains and hauled them all over the system. They got run hard 2926 in her 13 years of active service reached 1.5 million miles. They were underrated on TE also Santa Fe rated them at 66K when they actually had well over 75K lbs of power. The engineers and roadmasters knew it so they used the power in the hills.
Regarding Farrington's choice, I see no reason to question his choice of the last of the pre-WWII Ripley-designed 4-8-4's. The wartime engines had to make do without certain lightweight steel products that the last prewar engines had. My personal choice in 4-8-4's had always been the Norfolk and Western J, but this is a persoal choice, and would not question anyone choosing the Ripley AT&SF, the Central's Niagras, the SP's Daylights, the second group of Lackawanna's Pocanos, the C&O Greenbiars, CN-GTW, etc. All great locomotives, but all subject to who is running them, who is firing, what the trailing load is on a particular day, coal quality, even weather. An should be throw in the PRR T1 as well?
aboard!
Trains, trains, wonderful trains. The more you get, the more you toot!
Hi, Chuck, and welcome. I am still here, some have moved on one way or another.
As I said in my original reply in 2009, the topic has to be 'managed' with a strict adherence to criteria or it becomes a fan-boy discussion and little else. What criteria did Farrington feel were the most salient ones, why, and what were his various conclusions based on something more than his senses when in the cab of a wide variety of 4-8-4 steamers? Did he account for the confounds of driver skills, terrain, trailing tonnages, state of the tracks, proper valve adjustments, the lengths of runs between stops, whether the engine had roller bearings throughout, whether engines had been very recently shopped or were due to be shopped, and so on. Two engines of the same type operating with the same tonnages on separate days, but with different hogheads or firemen, would very likely offer different experiences and impressions to observers who managed cab rides both days. So, I wonder what published and verifiable data Farrington used to draw his conclusions, and if they would be widely supported by other experts in the industry.
As Feltonhill said later in the thread, many is the quicksand hole to be found in attempting to calculate the performance impetus in steam locomotives.
I am new to this forum, and just came across this thread from years ago about which was the "best" 4-8-4. So I am not sure anyone initially involved is even still participating in tihs forum. However, after reading the comments I did have one thought I wanted to offer. While the participants made a number of very valid points to defend their choice, I expect most of them were - like me - more involved with railroads as a hobby rather than a vocation. Moreover, no one seems to have much actual experience with steam locomotives - not surprising given how much time has passed since they were actually used in revenue service. Therefore I felt it worth mentioning that a well known writer who actually had first hand experience riding many railroads' steam locomotives - and could therefore knowledgeably draw comparisons - was very clear in several of his books about which 4-8-4 was the best one in the nation. The writer was S. Kip Farrington, Jr., and his clear choice was the Santa Fe 3776 class engines.
feltonhill Since you mention it......The 4400 horsepower figure for the N&W J was first used in a specification list dated March 11, 1941, seven months before the first J was completed Oct 20, 1941. It is a Rated Maximum Horsepower figure, and is apparently based on a maximum evaporative capacity (N&W's words) of 11,500 gallons/hr, or about 95,833 lbs/hr total evaporation, BP of 275 psi. I ran this through the Baldwin estimating method that was favored by N&W in that era, and came up with a calculated drawbar HP of 4410 at 35 mph, using an evaporation rate of 74.4 lbs water/SF of DHS/hr, producing a total figure including FWH of 95,833 lbs/hr. These figures are too close to be coincidental, so I believe I correctly used N&W's method of estimating. Moving ahead to 1982, I found NW Mechanical Dept Drawing for 611, no number but the date is 7-28-82, initialled by M.D.B. This drawing replicates exactly the Nominal Top Speed - 85 mph and Rated Maximum Horsepower - 4400 words and figures from the March 1941 specification sheet. This is virtually the same drawing as published in the ASME booklet. Based on the above I have to assume that (1) 4400 is not an actual rating, and (2) it is based on a 275 psi J, not 300. Just by way of a tickler, the maximum DBHP for a Class J is not 5,028 at 41 mph. N&W never said it was. The often cited DBHP curve was calculated using the Baldwin method. It was neither actual nor maximum at 300 psi. N&W so stated and cited its estimating method. Hope this helps
Since you mention it......The 4400 horsepower figure for the N&W J was first used in a specification list dated March 11, 1941, seven months before the first J was completed Oct 20, 1941. It is a Rated Maximum Horsepower figure, and is apparently based on a maximum evaporative capacity (N&W's words) of 11,500 gallons/hr, or about 95,833 lbs/hr total evaporation, BP of 275 psi. I ran this through the Baldwin estimating method that was favored by N&W in that era, and came up with a calculated drawbar HP of 4410 at 35 mph, using an evaporation rate of 74.4 lbs water/SF of DHS/hr, producing a total figure including FWH of 95,833 lbs/hr. These figures are too close to be coincidental, so I believe I correctly used N&W's method of estimating. Moving ahead to 1982, I found NW Mechanical Dept Drawing for 611, no number but the date is 7-28-82, initialled by M.D.B. This drawing replicates exactly the Nominal Top Speed - 85 mph and Rated Maximum Horsepower - 4400 words and figures from the March 1941 specification sheet. This is virtually the same drawing as published in the ASME booklet.
Based on the above I have to assume that (1) 4400 is not an actual rating, and (2) it is based on a 275 psi J, not 300.
Just by way of a tickler, the maximum DBHP for a Class J is not 5,028 at 41 mph. N&W never said it was. The often cited DBHP curve was calculated using the Baldwin method. It was neither actual nor maximum at 300 psi. N&W so stated and cited its estimating method.
Hope this helps
feltonhill,
thank you for your correction and clearing this,
lars
For passenger service, I'd like to put in a vote for the Rio Grande's 1800-series 4-8-4's. They could pull an 18-car train up a 1.4% grade at 40mph. They were the first Rio Grande steamers with a one-piece cast steel frame, and had roller bearings on all engine and tender wheels. And they were mighty handsome devils, too, perhaps the best-looking of all 4-8-4's.
Feltonhill,
'tip my hat again about your superiour knowledge and helping us to put some data into right order.
feltonhill As I've written here before, analyzing and comparing steam locomotive performance is a very difficult process, if it's possible at all.
As I've written here before, analyzing and comparing steam locomotive performance is a very difficult process, if it's possible at all.
Yes, as before another member at a different thread pointed out preciesly "to sad, they did not do tests like "Road & Track" on steamlocomotives...
It is even more frustrating with books, many figures must be carefully examined and revised with other sources. Often numbers are out of whack (es. German books featuring US engines, aarghhh!); you think you are lucky to gain some drawbar tests, only to be got teached to forget all about this again... its a natural learning process in general.
Great, here are very well informed members on this forum, willing to grant some knowledge.
BTW: looked at J's technical drawing at the ASME booklet, dated 1982, the rated max. drawbar hp is 4400. Hmmm, maybe nobody told the J about that, itseld did not care about it and put additional 600hp?
Kind regards
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