Concerning dynamic augment, or "pounding", I read an interesting book published in 1952 called "The Steam Locomotive" by Albert Bruce. It wasn't a "gee-whiz" railfan book but a pretty scholarly study done by the author of a system of motive power that he knew was on the way out, and as a journalist Mr. Bruce just wanted to tell the story.
Anyway, Bruce mentioned high-speed motion pictures shot of locomotive drivers undergoing tests, and the "pounding" didn't occur until a certain speed was reached, keep the engine under that speed and the pounding just didn't happen. Of course, balancing had a lot to do with it but it seems if you pushed the engine too hard you were asking for trouble.
Mind you, I'm not a mechanical engineer, just a student of history. It used to be military history until I got tired of reading about people killing each other and switched to rail history, just as fascinating and a lot more positive, if you know what I mean, "con-structive" as opposed to "de-structive".
And as far as slipping and adhesion is concerned, well we know too many roads had a bad habit of abusing equipment. Hang too many cars on the back of the engine and you're begging for a slip. The old RF&P here in Richmond Va. ALWAYS made sure to tailor the tonnage to the ability of the engine to pull it, as a two-track bridge line they couldn't afford to have any breakdowns or failures, they had to keep those trains moving, and were quite successful at it. A class act was the RF&P.
Just a side note, jobs on the Richmond Fredericksburg and Potomac were so highly sought after the locals used to say RF&P stood for "Relatives, Friends and Parents", meaning you couldn't get a job there unless you knew someone who worked there!
Dear Firelock76:
You're thinking of Alfred W. Bruce. Mr. Bruce was more than a journalist; he was Director of Steam Engineering at ALCo. Yes, his book is one of the standard references on the subject. I keep my copy close at hand.
In writing from memory, I made an error in accrediting some information to Dr. Kaye Lamb. He IS an accomplished rail historian. However, the book I was referring to is by J. Parker Lamb. Dr. Lamb retired as the Chair of the Mechanical Engineering Dept. at the University of Texas, Austin. He has a lifelong interest in the steam locomotive. His Perfecting the American Steam Locomotive, Indiana University Press, 2003, is, in my opinion, THE contemporary study of North American steam. His book begins with a survey of the history of the American locomotive, examining its development in the 19th Century. He carries this through with a more detailed history of the technology developed by the Big Three and railroad shops in the 20th Century. Finally, he discusses the reasons the highly developed steam locomotives could not compete with the Diesel. While Bruce primarily described what is, Lamb gives more insight into how and why things developed. I found it gave me better insight into the types of choices that had to be made in high-end steam locomotive design. It is a well-illustrated survey intended for the interested layman rather than Bruce's comprehensive work for the railroad professional. I think the two books complement each other and recommend them both to any student of the steam locomotive (or, as it was once called in its earliest days, the "aeropteron").
With regard to balancing I'm sure you know the larger the drive wheels, the easier they are to balance. Once a reliable design of stoker made truly large locomotives possible, the increasing revolving and reciprocating masses had to be compensated by better than "rule of thumb" mechanics. Although it used to be "common knowledge" the maximum speed of a locomotive was the driving wheel diameter times 1.1, this rule went out the door with the 57-inch drivered 2-10-2s and heavy Mikados of the WW1 period. Anything over 30 mph would kink the rails horribly. What Lamb refers to as the Third Generation steam locomotive -- characterized by high horsepower, high speed capability and four-wheel trailing trucks -- required the first intensive scientific studies of wheel balancing. Eventually, cast driving wheel centres helped distribute the balance weight better. (Also, cast driving wheels did not fracture or get bent out of shape like spoked wheels could under maximum load!)
As I recall, the PRR thought well of the N&W J, but believed that 72-inch drivers were simply too small for fast passsenger service.
..- er-hm .. 70 ins ...
( and , yes , me too , I believe diameter was ok for N&W , yet too small for PRR Crestline - Chicago racing ground ;
it's a whole different matter to stage one short burst attack at top-max hyperated speed the engine was juuust able to attain - or to run such speeds continuously sustained for miles on end and in regular service day by day ; ( I believe , what the N&W wanted to make sure was their 4-8-4 had an ample reserve of speed potential above daily demand - first for 'just in case' performance reserve and , second for lower stress / lower wear in actual daily service , which perfectly made sense )
that said , diagram showed indicated power output line started to decline above a comparatively decent speed and that would have made sustained running at 90 - 100 mph rather inefficient , even if published ihp diagram profile was true - which is quite unlikely since it would propose there was a certain degree of steam flow throttling building up at a certain rate above , say 70 mph , only to fade out at higher speeds for no reason explained , which would violate physics of gas flow without presence of some indeed very special effects ..)
= J =
Something that should be noted here - during the PRR test N&W 610 was still operating at 275 psi. The pressure wasn't raised to 300 psi until ca August 1945. As a result, the J was not operating up to its final capability. Yet it was still capable of performing extremely well in PRR's regular passenger service.
There were several mentions of high average speeds. Railroad correspondence confirmed averages of 80 mph or more over 45-50 miles. The highest average was 94 mph for 45 miles. While PRR stated that it thought the machinery speeds were too high using 70" drivers (it preferred 80"), they left no doubt that the locomotive could accelerate quickly to these speeds and sustain them.
Finally, the reason that 610 was tested on the PRR's "racetrack" in contrast to areas where it would be better suited (e.g., Middle or Pittsburgh Divisions) is that's the only place it fit. Clearances were inadequate elsewhere to accept the J's 16' height, 11' width and general cross-section profile. The party dress that the J's wore concealed a real "body-builder" underneath!
Firelock76Bruce mentioned high-speed motion pictures shot of locomotive drivers undergoing tests, and the "pounding" didn't occur until a certain speed was reached, keep the engine under that speed and the pounding just didn't happen.
Hi Feltonhill
Sure , as for PRR standards , # 610 acceleration must have been nothing less than admirable , also high speed performance sure was way superior compared to an M1 of 72 ins drivers - the PRR class of locomotive coming nearest of then existing .
No question 90 - 100 mph could be sustained since # 610 was by far superior to an M1 in performance ( if an M1 could have reached this speed level ) , further , roller bearings prevented immediate effects of excessive mechanical stress as witnessed in the famous Mallard high speed run . Still , those were individually arranged loco exchange test runs - not actual service upheld for years !
By the way , since cylinder volume was already more than ample with 275 psi in regards to working at or above 90 mph , later extra 25 psi pressure could do nothing to improve on that - with 275 psi full throttle runing would have asked for exceedingly short cut-off , which was practiced in Britain but nor in the US , AFAIK . So , of necessity throttle had to be eased back to keep , not surpass , speeds with given train load . What 300 psi boiler pressure did improve was the engine's medium speed output and boiler heat energy reserve plus it provided an extra safety margain against priming / creeping water carry over at high output .
Standardizing drive wheel diameter of one passenger with one SE Mallet freight loco class (J and A classes) was an extreme case of engineering taylored to existing lines and profiles of a railroad - which certainly Roanoke was best at , being the RR's own manufacturer .
Regards
Juniatha
To jpp452: Now that's interesting, I didn't know Mr. Bruce worked for ALCO. And I'll have to keep a lookout of the J. Parker Lamb book you mentioned, sounds interesting. And with a name like J. Parker Lamb he just would HAVE to have been associated with the University of Texas, VERY Southern sounding name!
To Timz: In the Bruce book he talks of a literal "bounce" when the dynamic augement starts, that's bounce as in "boing-boing-boing" bounce!
As to the heavy "Mikes" and 2-10-2's of the World War One era, let's not forget a lot of the roads were operating on fairly light rail at the time, 80 to 90 pound stuff, WAY too light for the behemoths coming out of BLW and ALCO. Push those engines to the max and you were asking for track damage. Rail weights had to catch up, and quick!
Oh, and on the PRR and N&W's "J"s, I still think the mighty Pennsy couldn't admit those hilbillies down in Roanoke were better at steam engine design than THEY were. Hey, this was the "Standard Rairoad of the World", how could they admit otherwise? The USRA engines of the First world War era were GOOD engines, but the Pennsy didn't want anything to do with them either.
Don't forget the BIG role egos have in the business world, both then and now!
Hi Firelock
Big Egos in Big Business / Standard Pennsyroad of the World and the Normans & Wikings ( or Nerds & Witty if you prefer ) - *g* - oh , I can see why !
Besides , a thought sparked up in my mind visualizing the smooth contoured J on a PRR engine site : the N&W 4-8-4 must have contrasted quite a bit with standard PRR classes like K4s and M1 and not exactly to their advantage . This loco was like saying "See what an up to date steam power looks like"
Still , I'd like to add a word in favor of Juniata ( not Juniatha ) works : Responsibility for the big fiasco with the Big Engine was one shared by many in the industry , engineers from Pennsy , Baldwin , ALCO and - AFAIK - Lima , too . Conceded , designing this engine presented a huge step in development of length of single frame steam locomotives plus chosen w/a was quite special with novel concept of two identical drive sets in a single frame . Still , just why combined knowledge failed to foresee problems to such extent is somewhat difficult to comprehend today - and maybe was back then . Actually , I feel this might have been one - more or less unconscious - reason for apparent precipitous loss of interest in this locomotive , in spite of what had so far been achieved : simply nobody wanted to engage in solving unexpected mechanical malfunctions nobody seemed to understand . I still maintain it could have been tuned-up to work as anticipated with just that extra effort and detailed attendance such a very special design of a novel engine should be allowed to ask for .
Hi juniatha! Listen I just LOVE the look of the Pennsy S-1, the "Big Engine" , the star of the 1939 Worlds Fair in New York. (DaveK, if you're listening, you're a New York City kid. By any chance did you visit the Fair and see the S-1?). The S-1 just looked so cool, just like something out of a "Flash Gordon" serial from the 30's. Got to love something that out-of-this world.
The problem of course was, in the end, it was just TOO darn big! It makes me think of the guy who builds a boat in his backyard, THEN finds out it's so big he can't get it out from behind the house!
Too big for most of Pennsy's lines, bigger than any turntable they had, they had to limit it to the Crestline-Chicago line, and it was too big for that too, frequently derailing on the wyes when they tried to turn it around. I have to wonder, didn't ANYONE at the Juniata Works say "Uh, fellas, this things going to be a hit at the Worlds Fair, but THEN what do we do with it?"
Still, it's a pity that when the PRR was assembling a collection of locomotives at their Northumberland facility they didn't save the S-1, or a T-1, or the S-2 for that matter. Too bad.
As far as egos in the rail industry, there's a marvelous book called "The Men who Loved Trains" by Rush Loving Jr. It's a history of the near fall and then rise of eastern US railroading in the late 60's through the 70's and into the 90's. Some egos in that book let me tell you!
Interesting point, I guess I never really thought about the S-1 being TOO big!
But looking at it now, I can see why it derailed on wyes. Good grief, how big are those drivers?
The timbers beneath the rails are not the only ties that bind on the railroad. --Robert S. McGonigal
RE S-1: At 140 feet, three inches (per PRR diagram book) it was seven feet, five inches longer than the UP's Big Boy (UP diagram book). Comparative wheelbases were 123 feet, nine inches for the S-1; 117 feet, seven inches for the Big Boy.
RE THE ESTHETICS OF STREAMLINING: To love the look of any of these locomotives, you have to love streamlining, which I generally don't. There are a few exceptions in my book, the N&W J being, in my opinion, the most beautiful streamlined locomotive in the world. Unfortunately, I think truly efficient streamlining tended to be rather ugly, per the Gresley A4 class. I agree with designer Otto Kuhler that the bullet-nosed style of streamlining -- such as the S1's -- tended to be far more attractive than the "inverted bathtub" style. The only exception to the latter, I would say, were the Milwaukee's A Class Atlantics. The "inverted bathtub" was more efficient but didn't catch the lines of the steam locomotive, something that Kuhler felt was essential for public approval. The bullet-nose also identified the locomotive immediately as steam whereas the inverted bathtub looked too Dieselish (is that a word? It is now).
RE DYNAMIC AUGMENT: The definition, from the 1925 Locomotive Cyclopedia, is ""That force produced by the centrifugal action of the portion of the driving wheel counter-balance weight added to oppose the thrust of the reciprocating parts, and acting in a direction perpendicular to them. This force, when exerted downward, increases the pressure of the wheel on the rail and when acting upward tends to lift the wheel from the rail."
Juniatha, you make some good points. Certainly, there was room for tweaking. And, given some more time, PRR would have had the additional advantage of being able to use the newly-developed Franklin B poppet valve gear, with its infinitely variable cut-off. It wasn't available when the production duplexii came off the line. NYC's S-2a Niagara was fitted with it. Because NYC, too, had decided on the Diesel, Paul Kiefer was never able to fully test the potential of the poppet-valved 4-8-4.
The American steam locomotive's fate was already sealed by the time the AAR's mechanical committee recommended that poppet-valved locomotives be designed with a higher factor of adhesion. Again, this shows that the old thinking in engineering design had to be revised by the newest technology.
You students of all that is steam might know the name Livio Dante Porta (look him up on Wikipedia). Porta was an Argentine mechanical engineer who, up to his death in 2003, continued the development of steam, paying particular attention to steam flow and exhaust. I have seen video of a Garratt locomotive fitted with his improved exhaust system. Garratts, generally, were a very sure-footed breed. But this one is remarkably slippery. I conclude it was just too light on drivers to use all the extra power instantly available to it by free steam flow with minimal back pressure.
Juniatha By the way , since cylinder volume was already more than ample with 275 psi in regards to working at or above 90 mph , later extra 25 psi pressure could do nothing to improve on that - with 275 psi full throttle runing would have asked for exceedingly short cut-off , which was practiced in Britain but nor in the US , AFAIK . So , of necessity throttle had to be eased back to keep , not surpass , speeds with given train load . What 300 psi boiler pressure did improve was the engine's medium speed output and boiler heat energy reserve plus it provided an extra safety margain against priming / creeping water carry over at high output .
I've been saying the same thing for years on this forum. When the N&W raised the boiler pressure on the J from 275 PSI to 300 PSI, it did nothing to improve the high speed output. Nothing. It did increase the starting piston thrust (at the expense of adhesion since the weight on the drivers was unchanged), and marginally improve the efficiency / output at medium speeds. In the end, it didn't really matter. The J (like all steam) had dismal efficiency at 275 PSI, and it still had dismal efficiency at 300 PSI. The were all doomed to the scrapyard as soon as the War Production Board lifted restrictions on diesel-electric production.
By late 1966 the PRR published an equipment guide for all categories of passenger cars authorized to operate at 100MPH. My Dad was both Brakeman and Conductor on #28 through the last 3-5 years it ran all Pullman. I have CT220s marked with a notation that the train listed could operate at 100mph.
NYC's S2a was equipped with oscillating cam poppets, the same as the T1's. Rotary cam valve gear was available sometime in the 1930's, but didn't receive any wide application, except maybe on D&H. Vernon Smith recommended RC valves for the T1's but the production order was too far along, and the OC valves remained. FWIW, PRR T1 5500 was retrofitted with RC valve gear and the crews thought it was the best of the lot.
NYC's S2a was tested in the same detail as the S1b. Both are included in one 182-page report. Although it showed no significant gain in overall power between NYC 6023 and NYC 5500, 5500 used significantly less coal and water per unit of output.
Almost everyone on PRR that came in contact with 610 was pleased with all aspects of its performance. VP (at that time) James Symes noted its reliability and accessibility, resulting in short servicing times. The operating crews liked its fast acceleration, smooth ride and it's ability to handle even low grades of coal (there was a war on, pickyness wasn't part of the game). The only criticism was that the machinery speeds were too high because of the 70" drivers (which was true based on what PRR wanted to do).
The reason N&W raised the boiler pressure of the J's in 1945 wasn't output at high speed. As usual with most things on N&W, it was money, less operating cost in this case. Using constant speed (40 mph), tonnage (1,065) and grade (1.3%), N&W found that by raising the BP, the locomotive could be operated at 8% shorter cutoff (61% vs 66%), resulting in the use of 2.6% less water and 9.4% less coal., while still holding about 40 mph. These are average figures over four test runs.
Hi , Feltonhill
>> Using constant speed (40 mph), tonnage (1,065) and grade (1.3%), N&W found that by raising the BP, the locomotive could be operated at 8% shorter cutoff (61% vs 66%), resulting in the use of 2.6% less water and 9.4% less coal., while still holding about 40 mph. <<
Well , that pretty much confirms what I had written , see previous page
„What 300 psi boiler pressure did improve was the engine's medium speed output and boiler heat energy reserve plus it provided an extra safety margain against priming / creeping water carry over at high output . “
Saving coal and steam is just the reverse side of having more power available at the same firing rate .
Add.:
BTW - a 9.4 % saving of coal at a 2.6% saving of water is clearly out of proportion if all attending parameters have been kept unchanged ( as should be for a sound comparison to establish what has been gained with the increased boiler pressure - not sure if that was the case , though ) Of the two figures , water saving of 2.6 % would seem pretty nearly within measurement tolerances , especially in view of the ondulating profile of the RR's mainlines and testing method without constant speed / constant work secured by brake locomotives over at least 30 min , preferably 1 h at constant working rate of the tested locomotive . 9.4 % saving in coal consumption would only become plausible if work at lower boiler pressure had been hard up against grate limit ( where in the end extra coal does not generate any more steam ) In this case , any small saving of steam could have eased grate conditions over-proportionally . On the other had that would indicate N&W had run the 275 psi engine at "All cried out" pace , to quote Allison Moyet ( means : they had run the engine to its *very* limit of capacity - which might have been expected of N&W ) - this sheds a light upon what feats these big steam engines did perform , didn't come easy at all !
Juniatha,
Couple of clarifications and additions.
The grade was constant throughout the test. Christiansburg Hill is about 1.3% from Eggleston to Christiansburg. This is where the tests were run. Or did you use undulating in reference to general railroad profiles? I wasn't sure.
If you compare only the runs where the locomotive was running nearest to 275 psi and 300 psi, the percentages are higher than I quoted. I would be very hesitant to fault N&W's results as being out of proportion, unless I'm misreading what you wrote. They were very careful in both test procedures and conclusions drawn. Other railroads would usually use test methods that were way above anything expected on a daily basis. For example, check the unit evaporation rates of the J's boiler to generate a total of 100,000 lbs/hr, on the low side of what was accomplished during the test. They're very modest, somewhere around 80-85 lbs of steam per SF of direct heating surface.
As part of the test report, N&W stated that the locomotive was near maximum capacity during the 275 psi tests, but was not at capacity during the 300 psi tests. This was probably caused by working near the drafting limit (N&W was also testing different nozzle configurations) as opposed to the grate or evaporative limits. Defining "maximum capacity" for the N&W is not easy. Most railroads would use unit evaporation rates up to 125 lbs/SF DHS as a maximum, much higher than 80, which was an average figure recommended by Baldwin and other in the industry. According to surviving test reports, N&W didn't do this. They wanted to know what a locomotive could do any time, on any day, regardless of crew or weather. They didn't care about high figures (I have yet to find an indicated HP rating for any N&W locomotive), and did not beat an engine over a division to get a particular result
I had no idea....
Your remarks would call for a more detailed reply - yet I don't have time to spare presently , so just a few remarks :
Yes , with undulating profile I meant the N&W mainline in general . Yet , referring to the climb to Christiansburg , which seems to have been of major focus to the N&W , it was a pretty short stretch of line , only 12.6 miles up to Christiansburg from Elliston , where it's said they usually started a test run ( from stand still , too ) see http://brucebharper.info/nwrwy/divisions/NWRad.html
This was waaay toooo short to obtain anything near constant conditions of working in a big steam locomotive , especially when starting test from a standstill .
In the article on the PRR T1 test in N&W magazine 'The Arrow' , the text says up this 1.3 % climb load was adjusted so as to ask full output from the engine and by that a balance speed did self-establish and provided for precise measuring of continued output . However , besides being too short a stretch , in contrast to what the text conveys , a graphic plot of speed over the grade shows speed was always varying , there never was anything like constant output over any mile of the line . Because of that , logically no constant rate of evaporation was ever established , and consequently to try and take steam consumptions could only give momentary figures of uncertain configuration or telling , wherein it must remain specifically uncertain if amount of steam actually consumed by cylinders was the same or larger (drawing on boiler reserve ) or lower ( leaving some evaporation to rebuild boiler reserve ) than measured water feed - not mentioning extra complication - if so equipped - of taking into account variable hot water return to boiler by mixing type preheater . This was quite a tricky aspect to account for in order to obtain true steam consumption of cylinders and different approaches were used on various railroads ( US ) and railways ( EU ) resulting in non-comparable results having different meanings based on differing test set-ups , some of them listing 'cold water consumption' without explicitly marking figures as that , which of course led to substantial contortion of picture of cylinder efficiency !
In general , I wonder what could be learned by having an engine meant to be an essentially fast running locomotive type hammer up a grade in low speed range with maximum tonnage behind the tender . Ok , so test results were a J class loco could take a formidable load up to Christiansburg , about twice the train load at max demanded for actual passenger traffic - this might be seen as an ample reserve of power to deal with adverse conditions as they may be encountered in extreme cases of weather , fuel , load or other . However , since this low speed work always near maximum tractive effort transmitted to rail meant long cut-off working at low piston speeds little did this sort of running learn about valve gear characteristics and steam flow at shorter cut-offs and higher piston speeds .
In a graph showing drawbar power output , line reaches its apex at no more than 40 mph , then begins to fall and above some 60 mph takes on an unlikely , almost straight line , keeping the rate of falling constant as at around 60 mph . Unlikely for constant rate of evaporation , that is . If for some reason steaming rate increased with speed above 60 mph it may actually have resulted in such an untypical contour of output line . However , any graphic display of output line should always be based on constant steaming rate representing , by definition , standard , nominal or maximum sustained - however never variable steaming rate because that would introduce an arbitrary factor .
With maximum steaming rate largely depending on effectiveness of draughting , there might have been a degree of variation in gas pumping capacity which - if steaming really did increase with higher speeds and shorter cut-off - caused improved combustion conditions in upper speed range . Although this would have been contrary to expectable behavior of simple round chimney draughing devices in large boilered locomotives , it could indicate fiercer blast with lower speeds / longer cut-offs was rather too strong for optimum combustion conditions and may have partly fluidized fire bed with consequential high losses of unburnt particles of coal - thus super-increased fuel consumption . This was a general behavior of coal grate firing and was inevitable when working near to grate limit , as I had written before .
Side remark : if this condition was improved with introduction of 300 psi boiler pressure ( by modified draughting likewise introduced ) it could explain a 9.4 % reduction of fuel consumption for but 2.6 % lower evaporation - meaning a fairly substantial jump in boiler efficiency on this very small reduction of steaming rate , you see .
So , I'm not supposing N&W tests were faulty as such , on the contrary I believe they contrived their test set ups pretty much to tell them what they wanted to know . Only , you may pardon my wondering if these set ups could be considered fully up to scientific standards , such as concerns establishing truly constant engine working , number of runs at a certain combination of speed and tractive effort , number of tested points over the entire speed range and so on , each run demanding at least a 30 min span of measuring at constant conditions ( demanding a 'lead-in' of at least another 30 min and a shorter 'lead-out' - all in all easily summing up to 100 miles of test run on a constant profile or with brake locomotives to control constant conditions ) complete set of tests all in all asking for at least some 60 test runs to cover but four to five points of speed , not to mention various working rates , too . The way I see it , N&W tests rather were focussed on a practical evaluation of "does it do the job ?" and if so they didn't care so much about percentage of unburnt losses or exact values of specific steam consumption at this or that working point . This was ok as long as question was focussed on making sure their own class of locomotive performed all it could reasonably be asked to perform - and then something . Limitations of this approach to testing showed when the Pennsy T1 was run through the same sort of set up , never accounting for her very different characteristics .
Since it was noted N&W crews T1 engine handling markedly improved with repeated runs ( and from what I read in the article and data given I get an impression it wasn't bad from the start - arguably better than average handling on the Pennsy itself ! ) I believe the T1 , although not an ideal type of locomotive for the N&W , could have succeeded if only she had been asked to do what she had to offer - and that certainly did not include lifting a heavy passenger train made extra super heavy by adding up laden coal gondolas up a 1.3 % grade - a J1 would have been more fitting .
The DBHP graph you're referring to is calculated using the Baldwin method, a widely used and very conservative method of estimating locomotive performance. It is not a graph of actual performance. That's why it has the peculiar shape - rapid rise to a relatively early peak, then an almost straight line to whatever maximum speed was relevant. No actual curve looks like this. However, every estimate calculated using the Baldwin method does. You can spot it right away anytime it's used. I don't know exactly what article you're using for the DBHP chart, but it should have a note in the upper right corner stating that the curve is "theoretical." Without the note, it's not a complete copy of what N&W did.
Theoretically, N&W's methods may not seem to work, but based on results, apparently they did, at least for passenger power. Someone told me the story that when N&W was asked about the maximum power of a J they replied, "adequate." True or not, it sums up their general outlook. N&W freight locomotives were subjected to more extensive OTR testing, right down to the benefits of different sizes of coal.
Short term readings were used on many railroads during over-the-road tests. The NYC Niagara test, about as close to "gold standard" as we're going to get in the U.S., used short term readings to check IHP, DBHP and other items. N&W did the same thing, taking readings over a 2-mile stretch MP282-MP284. At this point, the locomotive would have been "warmed up," so-to-speak, and reasonable readings could be made.
it was a pretty short stretch of line , only 12.6 miles up to Christiansburg from Elliston , where it's said they usually started a test run ( from stand still , too ) see http://brucebharper.info/nwrwy/divisions/NWRad.html This was waaay toooo short to obtain anything near constant conditions of working in a big steam locomotive , especially when starting test from a standstill .
.
They would check the water level in the tender at Elliston after each run. Typical day would be Roanoke to Elliston while taking readings, stop in Elliston to check water usage, then make one or two runs Elliston to C-burg, returning to Roanoke after the last C-burg run.
BigJim :
>> And where on the N&W are you going to find a constant 1.3% (or greater) grade that is any longer? Gee Whiz, you have to keep in mind when all of this took place.
Without looking through my info, does it state that the test was started from a standstill?<<
Yes , in said article on the T1 at Roanoke tests author explicitly noted stop for water and water level check at E , then going up the hill . Really , to provide a minimum of pure test condition they needed to have re-checked water level immediately at arrival at Christiansburg again ( and then what about braking time / distance and speed !? if you don't account for it properly then you have an error influence in acceleration work not properly accounted for !)
>> Gee Whiz, you have to keep in mind when all of this took place.<<
That's what I tried to point out ! If you come to think of the means then available I think you'll see it should be difficult enough to assert precisely just how many gallons of water are present in tender tank and boiler (!) when starting and how many are left in the tender when arriving and how many are in the boiler at that point ( on such a short trip having somewhat higher or lower level of water in the boiler would easily be misleading due to the large amount of water circulating in the boiler ) I read in said article test engine was run around train at C'burg and returned tender first with train to E and then did a second run up the hill .
If that should mean water consumption of both trips combined was measured , probably by allowing for a certain consumption for shunting and returning and shunting again , then in spite of apparently greater safety by using an average figure obtained from both results , inexactitude is even larger because of variable influence of the return trip , if consumptions of this operation is not separated from grade climbing effort ( if it was, then recorded consummations of the two trips would be separated and combined accounting wouldn't make sense )
>>And where on the N&W are you going to find a constant 1.3% (or greater) grade that is any longer?<<
That's exactly what I wanted to point out : there was no long enough stretch of line offering constant conditions over sufficient distance and time to reach constant working conditions in an engine with that large a heat storage volume as was a big steam locomotive ( to mind : in a boiler explosion that heat storage is released in an instance and it amounts to some 1 - 2 million hp depending on size of boiler and live steam heat enthalpy !) - to balance that out between entering and leaving a recorded time span within a run ( total heat content of boiler at start of recording minus total heat content of boiler at end of recordings = nil ) was a very delicate task - how would you propose it was done ? Water content in boiler : just looking at the water gauge and in case filling up some ? then what exactly was 'same' in water level in boiler ? mind there are misleading influences by water treatment causing more or less foaming , by total amount of steam bubbles within boiler water at any instance - amount and volume varying widely with steaming rate and thus likely to propose 'higher' ( false ) water level at arrival with hot evaporation surfaces than at moment before starting - just checking water gauge would be waaay insufficient ! Further : same boiler pressure at start as at arrival ? well , at least ! however exactly what was 'same' boiler pressure ? needle at 300 psi while standing with throttle closed and fairly static conditions in boiler and 300 or rather ~ 290 psi while working full throttle and highly volatile conditions including pressure drops at steam dome main pipe intake , superheater header , throttle valve intake ( followed by further drop through throttle and live steam pipes ? You will see things were not so easy with the tools available at that time , there were no electronic flow meters etc .
Longer periods of constant working conditions enabled to contain measurement errors because (a) more uniform working could be established (b) consumption total was larger and thus small measuring errors did not account but for smaller portions of total consumption .
Repeat : I'm not trying to prove anyone at fault - I'm in contrast trying to point out how tricky it was to obtain correct data from a heat energy engine with characteristics as elastic and heat energy reserves as large in relation to output as was the steam locomotive .
Agree , that's what I was trying to point out ! As for the dbhp graph : no , there is no such line , there is a bottom line reading >> ROANOKE , VA , SEPT 7 , 1945 << Ok , if this is a 'theoretical' graph on Baldwin formula ( which was no formula built on true thermodynamic heat conversion acting in the engine , instead was one of these 'educated guess' formulae widely spread in RR engineering , evolved by extrapolation of known 'substitute' factors ) then it's not necessarily descriptive of the N&W J . I would still like to see an indicated output curve evolved over full boiler output - if built on an acceleration test to give at least a tentatively characteristic development of ihp over speed .
Stops were made at Elliston and Christiansburg to measure water level in the tender and boiler (T1 vs J, sentence bridging pg7-pg8). There is sufficient level track at both locations to accomplish this. Water readings are for the uphill part of the trip.
There were a lot of repetitions made during the 1945 tests. 23 runs were made between Elliston and C-burg from 8/6/45 to 8/18/45. This is one way to get around both between-sample variation
The DBHP chart I was referring to was made during the 1945 tests to compare BP. The 1948 graph shown in the T vs J article looks slightly different but still has the flat tail-off at higher speeds. I compared the two curves for 604 for the 1945 test and the curve attributed to 604 in the 1948 test. The differences are very slight, less than 2% which is about as close as you can read these two graphs. IMO, its the same 1945 curve, just redrawn. Unfortunately the 1948 Chart does not have the explanatory note that the 1945 test had.
That's exactly what I wanted to point out : there was no long enough stretch of line offering constant conditions over sufficient distance and time to reach constant working conditions in an engine with that large a heat storage volume as was a big steam locomotive
And the point I was trying to make was that I think you are asking too much from a test in that time period. Evidently they found they answers to their questions to whatever decimal point they felt was sufficient. As they say "hindsight is 20/20" and it is futile to try to apply the test measures that are available today to what happened sixty-seven years ago.
They did what they did with what was available. And, by golly, the boys from a little ol' town in southwest Virginia got it right!
"....the boys from a little ol' town in southwest Virginia got it right!"
And anyone who thinks the folks at Baldwin and the PRR weren't jealous and probably seething a little bit is kidding himself!
Firelock76 "....the boys from a little ol' town in southwest Virginia got it right!" And anyone who thinks the folks at Baldwin and the PRR weren't jealous and probably seething a little bit is kidding himself!
Jealous about what? The PRR had far different operational needs than the N&W, and neither the J, A, or Y Class wouldn't have done the PRR much good for those needs. Anyone who believes they know what the PRR or Baldwin was thinking is only kidding themselves.
I agree with what Junitha said 100%. But if it make the rest of you sleep better, just keep drinking that Kool-Aid and believe what you want to.
OK, about the Pennsy's operational needs: The Pennsy had to go up and down hills, the N&W had to go up and down hills. The Pennsy needed an engine that could approach the 100mph mark reliably, the "J" could run at the "century" mark if needed. If the "J" only had 70 inch drivers, so what? The balancing was so good it didn't make any difference how big or small they were. And the "A's" and "Y's" could PULL. What more do you need? We could go 'round and 'round with this but I think all are getting what I mean. Hills is hills and straights is straights and either the engines can handle them or they can't. The N&W's locomotives could and did.
I don't presume to know what Baldwin and the PRR were thinking, but I do know that big egos and the inability to admit that someone's got a better idea than you do, or the inability to admit you can learn from someone outside the "family" has lead to more business failures, lost wars, and governmental collapses than I'd care to go into. Trust me om this one, I'm no mechanical engineer, but brother I know my history.
Oh by the way, at the first opportunity I'll try GP-40's suggestion of trying some Kool-Aid mixed with some moonshine and see if it really tastes like some overpriced cocktail from a Yuppie bar, not that I'd go into one of those nests of insufferable snobs to begin with! Or maybe I'll try mixing it with some "Wild Turkey", no forget it, that'd be a mortal sin!
Firelock76 Trust me om this one, I'm no mechanical engineer, but brother I know my history....
Trust me om this one, I'm no mechanical engineer, but brother I know my history....
...and neither are the vast majority of people who write the steam choo-choo articles/books. That's why they are so messed up, inaccurate and full of Kool-Aid. They spend too much time trying to compare "historical" events taken out of context, rather that having a full understanding of the science and engineering that was going on.
Login, or register today to interact in our online community, comment on articles, receive our newsletter, manage your account online and more!
Get the Classic Trains twice-monthly newsletter