Anyway, I am glad I witnessed this race. From Moutain View or Tower View on the rear of the Broadway (never dreaming that some day I would be a small shareholder in the owner of Mountain View, Pullman Classics Limited). As I recall we lost and the Century won. We had head end cars added on the Broadway, while the NYC (both still all-Pullman) began with the baggage dorm and had a shorter consist. Both trains were pulled by EMD E-units at the time. But I had traveled to Chicago on the Century, returning via the Brodway, change to Clocker at N. Phila, MU at Trenton, Princeton Jc. and back, and then mu to NYC.
You know, Dave, I have no idea! The original teller of the tale didn't specify what was pulling the trains or when the incident occurred. We just have to accept is as a fun bit of railroad lore and let it go at that.
Now I want to know: If the Century was headed by a Niagra, was the Broadway by a T-1, or two K-4's? If it was a J3A vs single K4 contest, well the winner would be quite obvious.
Concerning the New York Central's high speed runs to and from Chicago, there's a great story I'd like to pass on.
Both the 20th Century Limited and it's arch-rival, the Pennsy's Broad Way Limited, used to depart Chicagos Englewood stationat the same time on adjacent tracks. This always (well almost always) led to a race between the two, to the absolute delight of the passengers. Mind you, OFFICIALLY the railroads said they weren't racing, and OFFICIALLY the train crews were forbidden to race.
One day, a NYC official was aboard the Century, when he felt an abnormal acceleration. He looked out the window and saw the Broad Way running "neck and neck" with his own train. As the Broad Way sped up, the Century did as well. He saw a conductor passing down the aisle and called out "Conductor!" "Yes sir?" replied the conductor. "Step this way, sir." and the man came over. "Are we racing the Broadway?" "AHHHH, ERRRR, OHHHHH," stammered the conductor. "I see," said the official. "Get word to the engineer. If he looses, he's FIRED!"
Crandell,
I enjoyed reading Lars Loco's posts as well.
- Erik
Just a FYI, and a bit startling, but lars loco has asked that his account be deleted. He reports that he can no longer devote the time to the forum that he was used to. I think it safe to say that he will be missed. I wish him well.
Crandell
Thanks for more top rate inputs.
With respect to Firelock 76’s (20.4.11) comments, this is an almost perfect articulation of my belief, namely that, like any successful species, the North American steam locomotive was well adapted to its environment, (operating, social, political, economic and so forth). (It is by the way true that in this country as in the US, locomotive efficiency was relatively low in the operators priority list, getting the train over the road near the top; in the heyday of steam our railways were privately operated also, fighting to stay alive from the 1920s on as road transport took off, fighting for the country’s existence during the war years, so most of the other considerations about US railroads also applied). It has been suggested by Porta that efficiency improvements to US designs might have been possible by reducing backpressure. I am looking to establish if this was indeed the case; my view is that, given the relatively low priority of efficiency, any improvement would have to be very significant for it to have had a worthwhile impact. I do think that it is likely that the answer to this question will turn on how hard locomotives (let’s restrict it to passenger locomotives) were actually worked so I will come back to the point about the southbound mail later.
With respect to NM_Coot 20.4.11, we are I think in violent agreement on all points. I know the gentleman who translated Chapelon’s book into English, and he makes sure I don’t deviate from the straight and narrow, though of course there are factors that with 20:20 hindsight, which is what high speed computing can give you, aren’t quite as important as Chapelon thought. On point 4, you speak of ‘Nozzles’ How many did the 3460 class have? I will come back to NYC performance.
With respect to feltonhill 20.4.11, yes, I’m absolutely certain that the 750F for the NYC Hudson is inlet steam temperature, not superheat level. Given that I believe that superheat is the dominant factor in determining efficiency, it would be good if one could estimate what would be delivered from published dimensions. I have a book with a most unpromising title ‘The Great Book of Trains’ written by two top rank British writers, Hollingsworth and Cook, which is remarkable in that it makes a great general interest coffee table book, (super line drawings), and, as far as I can tell also provides reliable technical details on hundreds of steam locomotives from around the world, and exceptionally knowledgeable write ups. At $10 second hand on Amazon, it’s an absolute snip! I’m telling you this because last week, I spent 2 hours extracting all the technical data on the US designs featured, to try to address this point. I was surprised how different some of the key dimensions were, particularly in quoted superheater areas. (Sadly, my computer ate the spreadsheet, so need to start over!). However, I believe that superheater area itself is not the sole determinant of superheat achieved. Test results over here showed that superheat always increased with the number of flues; however they also showed that if the distance between the tube plates was more than about 18’, superheat begins to go down, possibly because the flue gases are cooler than the steam in the last few feet of the flues, so the steam gets cooled. Obviously, the longer the flues, the higher the superheater area at a given number of flues, but this does not guarantee high superheat. We found best practice was to have not much more than 17’ between the tubeplates. The class with the largest superheater area over here did not generate the highest superheat, in part I believe because it was 19+’ between the tubeplates. From the very limited US data I have, this also seems to apply, in that the T1 (18’ between plates, 1430 sqft superheater) delivered higher inlet steam temperatures (750+F) than the Niagara, (20’ between plates, 2060 sqft superheater, which gave ca 680F at 52500lbs/hr). This is a point I would like to explore further, hoping the texts I am getting will provide details on this important dimension. But 750F for a Hudson does not seem unreasonable to me.
With respect to NM_Coot, 21.04.11, thanks, this is just the kind of data I’m looking for. With respect to the 3460 class, the 44 sqins nozzle are must mean they had four 3.75” nozzles? Depending on the steam rates normally used, going down to 40 sqins wouldn’t be too tragic (See Below).
Now for some more analyses, which I’ll try to keep simple. Hollingsworth and Cook give a quote for a Hudson hauling a 940 tonne 20th Century, which made it from Toledo to Elkhart (133 miles) in 112.5minutes net, and on to Englewood (93.9 miles) in 79.5 mins, both about 71mph start to stop. I am assuming this is an example of very good running. Since it’s basically downhill form Elkhart to Chicago, and I’m not sure if speed restrictions applied beyond Gary, I’ve ‘built’ the line from Toledo to Elkhart. What I found was that, using standard resistance equations, and assuming a relatively modest start, I could get to Elkhart in 111.5 minutes without exceeding 3000IHP. On the gentle upgrades to Wauseon, speed rose to about 71mph (32mins). In the gentle dip down to Stryker, speed rose to 81 mph (43 ¼ mins), before falling to 67 mph up to Corunna. Finally, on the descent to Elkhart speed rose to 90mph. covering the 44 miles on to Dunlap in 32 minutes, and averaging 84mph over the 38 miles from Kendalville. If a more vigorous start had been made, power required later would have been less. Now my computer programme says that the Hudson would need about 42000lbs/hr to the cylinders to deliver 3000 IHP, and even if the Hudson blastpipe diameter were only 6.5”, this would not lead to excessive back pressure. So, adding this to my analysis of the MILW F7, and extrapolating wildly from just two data points, this says that the actual working rates of these Hudsons in normal service would not lead to efficiency losses due to restricted blastpipe dimensions. Now I’m sure an NYC Hudson could sustain much more than 3000IHP. The question is, whether there is a run on the proverbial 8 hour late southbound mail that demonstrates this.
The second set of analyses was to look at the acceleration tests with a Niagara east from Utica with 1005-1875 short tons. The line is pretty flat, perhaps a very slight downgrade to the canal bridge. Now these represent the most astonishing running I have ever come across. I only have the bare details of loads, times, and distance to reaching 75mph, but the times reported can only have been achieved by working the Niagara in full gear right from the off, with power reaching about 6000IHP at about 45mph. From then on, cut off was gradually eased to maintain just over 6000IHP until 75mph was reached. I’m almost speechless! The sight must have been unbelievable, blastpipe pressures phenomenal. Now I recall David P Morgan reflecting on how every steam fan in the early 1950s knew that beyond about 20-30 mph, a Niagara could outperform a contemporary 6000 HP ABA E unit, and this is what these tests surely demonstrate. The point Morgan was really making however was that, even though this was true, it was irrelevant. I believe also, that even though this performance was surely possible, it was rarely needed in practice, except on the 8 hour late mail. If you put a Niagara on 1200 tonnes east from Toledo, accelerate more gently than the above tests, and work at up to 6000IHP on to Elkhart, then, having self imposed a 90mph limit, I get to Elkhart in 96mins, running at 90 mph up hill and down dale from Swanton on. Maximum power is about 5700IHP, less on the downgrades. Did a Niagara ever do this in normal service? I doubt it, but would love to be proved wrong. So, I suspect even the Niagaras were actually worked at steam rates which did not involve excessive blastpipe pressures. All data to the contrary very welcome.
Heading off to Catalan Spain for 10 days from tomorrow, to a computer free zone, so will be off the case for a while.
NM_Coot - Thanks for the figures! I have two of the three sources: NYC 4-6-4's (Reed) and Santa Fe's Big 3 (Farrington). I assume that Profiles 26 is the Milw F7 and/or A? Don't have that
Farrington's book is the real gem here. He apparently had the clout or $$ to put what he wanted into his books. As you already know, and others should be aware, he frequently puts in copies of actual test reports. He doesn't paraphrase or editorialize. He lets the railroad's test department do the talking. It's great stuff.
On the other hand, Reed tends to include a lot of numbers so that his analyses look technically rigorous, but he doesn't always use consistent data in his comparisons. Some of his other articles where I got into the details, he got a bit fast-and-loose at times.
This will keep me off the streets for a little while. Thanks again!
Here are some numbers with sources.
Loco Profile 2, Table II, text. Loco Profile 26, text. The Santa Fe's Big Three, text, tables, figures. I've compared three contemporary 4-6-4's. I put in some numbers that may be of use to others. That's all! This is not a mine's bigger, better, whatever, effort.
Railroad NYC CMStPP ATSF
Class J-3a F-7 3460
builder ALCO ALCO Baldwin
year 1937 1938 1937
boiler pressure (psi) 275* 300 300
grate area (ft^2) 82 96.5 99
total evap surface (ft^2) 4187 4166 4760
superheat surface (ft^2) 1745 1695 2080
superheat temp (deg F) 750 *** 775
superheat/total evap (areas,%) 41.8 40.6 43.7
total evap/grate area (ratio) 51.1 43.3 48.1
wheel dia (in) 79 84 84
valve diameter (in) 14 12 13**
piston diameter (in) 22.5 23.5 23.5
max travel (in) 8.5 7.5 7
exhaust nozzle dia (equiv in) 7.25 7 7.5
choke/stack dia (in) 21.5 18.5 24
max hourly evap rate (lb) 93,000## ? 89370#
max inp (hp@mph) 4900@75 ? 4350@65
max dbhp (hp@mph) 3935@65 ? 3600@50
* Later 265 psi. Designed for 300psi.
** Open throttle indicator cards show drop of about 30 psi, boiler to valve chest.
# 1st District, Arizona Division, heavy grade at 45 mph, 3997 ihp, steam consumption was 68700 lb/hr.
## Test, Selkirk.
*** Class A superheat was 680-700 deg F. F-7 no reference value.
? No reference value in my library.
I think the numbers support a conclusion that the F-7 superheat was low typical. The author of Loco Profile 26, Brian Reed, says, with regard to the A class: "This was not a very high degree of superheat." I think the numbers above would tend to indicate a similar condition for the F-7. The users of this data are completely free to draw a different conclusion!
Regards and happy contemplations
NM_Coot
Add flue sanding, keeping any necessary and installed smokebox netting clear, petitcoat pipes mounted correctly....they were complex machines that needed skilled and experienced, not to mention attentive, operators.
MEGO also!! Help me out here. I'm as good a number cruncher as the next person but I need some assistance.
The NYC J3a is credited with a superheat of 750 degrees. I'll bet this is total steam temperature, not superheat. The J3a's operated at 265 psi, which would be a saturated temperature of about 410 deg F. For a total steam temp of 750 deg F, the superheat would have to be about 340 deg, which is a very high figure. Where did it come from? I'm not doubting it, just want to know the source.
I've re-read most of the thread and would also like to know the source of the MILW F7's "low" superheat? Anyone have the figure? I've never read anything that indicated the F7 was deficient in that area. But stuff happens in any design. Maybe I haven't read enough.
NMCoot - I believe you're in good company with the water treatment comment. Wasn't Porta a proponent of this idea?
Some brief comments if I may.
1. Water treatment is far more important to good boiler operation (and maintenance) than feedwater heating.
2. Chaplelon was far more concerned with the entire steam circuit than he was about the exhaust configuration per se. The exhaust point is but one of many critical points in the steam circuit. He was as concerned about the drafting interaction with combustion as he was about back-pressure.
3. I don't quite understand the pokes at Chapelon. He was a modest engineer who achieved remarkable results. In fact, I will go so far as to say that if you do not know and understand Chapelon's work you do not really understand all the important elements and inter-relationships of modern Stephenson locomotive design. His book which summarizes his fundamental work was published (in French) in 1937 and revised and expanded in 1952. A English translation was published in 2000. The contents are as valid today as they were in 1937.
4. Stephenson steam locomotive design is a constant trade-off of factors. Once you get the exhaust about right, continued tweaking isn't going to gain much in day to day service. For example, soft exhaust often led to problems with smoke and water vapor obscuring forward vision. Farrington, in The Santa Fe's Big Three, reprints many Santa Fe test reports. The 3460 class developed 4350ihp at 65 mph and 3600dhp at 50 mph. Because of drifting smoke, the ATSF test engineers gradually reduced the nozzle openings from 3 3/4" to 3 1/2" and the stack diameter from 26" to 24" without any appreciable change in performance. The smoke problem was particularly problematic when working lightly. There are also some interesting relationships between firebox draft, smoke box draft and oil atomizer pressure. How about that folks! Anyone interested in seeing how a railroad evaluated locomotives in service should read this book.
5. As best I can research, the Milwaukee F-7 class is a development of the A class. These two classes handled low tare weight trains at high speed over a relatively flat line. ALCO essentially designed both. The 84" drivers were used to keep piston speeds within reasonable limits. ALCO did pay attention to the steam circuit. The relatively low superheat is unusual. the A class could do about 3000-3300ihp and I would venture that the F-7 probably could do about 3500-3700 ihp (primarily because of rather low superheat). In the example given, a total weight of 855 tons with an engine weight of 395 tons really means that the train was there to provide braking effort. Both classes did what they were designed to do but of the two the A class is really the big step forward in performance.
6. NYC J-3a's regularly handled trains of 800 to 1000 tons tare and regularly achieved schedule service speeds of 80-90 mph. In my opinion a J-3a could handle the F-7 service and I doubt the opposite is true. The only question might be the 79" drivers on the J-3a but I think the proven lively performance of the J-3a would compensate. The ATSF 3460 class Hudsons had 84" drivers and could handle trains of 800 to 1000 tare at 90 mph when schedule compliance was required.
7. Ther are numerous examples of excellent US design practice. So the point isn't making "the case against US front ends." The point was simply that when small locomotives significantly out-perform very much larger ones, the designers first step in making the larger ones perform better is to look at what makes the small ones perform so well.
Regards
Ok folks, I think we're getting to the point here where we can't see the forest for the trees. All this technical data is starting to make my eyes glaze over and my head swim! I'm not an engineer, but I am an amateur historian, so let me give you all a little history lesson about American railroads, especially to our brothers and sisters "across the pond".
As opposed to railroads on the European continent which were state run, American railroads were strictly a private enterprise. No national treasury to back those boys up in the 19th Century when things got rollin'. American railroad builders had to raise the capital themselves. AND those investors were looking for a return on their investment as soon as possible. Ever hear the old saying "the best is the enemy of the good"? In the United States that meant a good roadbed, a good locomotive, good rolling stock, was a lot better than someting perfect in the future. The roads had to start making money NOW. Improvements could always be made in the future when the money started coming in. Certainly mistakes were made, often with tragic consequences, but it's too easy to critisise from the comfort of an armchair when you're not the one on the spot with stockholders looking over your shoulder.
So, American locomotives had to be built tough and durable. If some efficiency was lost, well, that's something they were willing to live with. Remember, if you build a perfect locomotive you need a perfect road bed to run it on, and in the old days that was usually lacking here in the U.S. By the way, those tough American engines were also a pretty attractive puchase for those building railroads in what we'd call "Third World" countrys, but I'm digressing.
Now if the locomotive builders got it wrong at times, well who's to blame them. No computer assist back in the old days. All the boys at Baldwin, ALCO, or Lima had to go on was their own knowledge of physics, geometry, metallurgy, and prior experience, and if they had a slide rule to help them they were lucky. Sure they got some things wrong, but boy when they got it right! Niagaras, Mohawks, Big Boys, Berkshires, the Norfolk and Westerns mighty Class A's, J's, and Y's! Even the 4-4-0 "American" type was a masterpiece in it's own right. By the way, even the present day diesel builders get it wrong from time to time.
So, remember the American philosphy was "keep the tonnage moving!" Get 'em in, get 'em serviced, get 'em out again. If the engine can't take it you get rid of it and get another. Keep them trains rollin'!
Mind you, I'm not attempting to denigrate any other nations locomotives. British, German, French, all were good machines for the evironments they operated in. All were gems in their own right. Hey, some were so beautiful they LOOKED like pieces of jewelry! Would they have been sucessful here in the U.S? Well, I don't know. I DO know that American designers were aware of what was going on with European steam, but there wasn't much they were willing to borrow. Superheating, the Belpaire boiler, the Walschaerts valve gear, as far as I know that was as far as they went.
So how hard was American steam run? Well, as the song says "I'll run her 'till she leaves the rail, 'cause I'm eight hours late with the southbound mail!"
Gotta go, my eyes are glazing over again! I guess it beats writers cramp!
Thanks for these comments; with respect to the video of UP3985 posted by Hamltnblue, then if you want to know why I find this topic compelling that explains everything perfectly. It has to be high up in my top ten of steam videos on You Tube. Unfortunately those of us with over active left hand sides of the brain try to explore this magic, and try and reduce everything to numbers!
Thanks to Lars Loco for the link to the previous thread, which contains some helpful stuff on feedwater heaters, a topic I’m going to need to get my brain round (they never caught on in the UK, we settled for exhaust steam injectors, which recycled roughly 6% of the heat in the exhaust steam), since this determines how much of the cylinder feed goes up the blastpipe, a very important correction especially at high steam rates. Also, the data on what the Big Boys put out at 14 mph (ca 4200IHP) is the kind of stuff I’m after. Lots of other interesting stuff in the thread too, don’t want to divert onto that!
With respect to NM_Coot’s data, that’s helpful, but not quite enough. Let me tell you what I’d ideally like, what I’d happily settle for, and why I think the point is important.
Between you, you have helped focus my original query into something like ‘How much would Chapelon style exhaust technology have improved the efficiency of latter day US steam locomotives?’ My original Porta quote implies he thought the answer was ‘a lot’. I think the answer is more likely ‘a bit, nothing game changing’. This depends on the rates at which locomotives were habitually worked, not what they could do on the occasions when they were worked flat out for short periods, for it is overall rate of working that determines overall efficiency.
Let me illustrate with some calculations I did some years back on the Milwaukee Road F7s. (Don’t take numbers too literally, my thinking has moved on quite a bit since then, but they are good enough to make the general point). In Jim Scribbins book ‘The Hiawatha Story’ are what I’d really like- detailed logs of the working of the heaviest/fastest US expresses. (My strong suspicion always was, as NM_Coot writes that freight is not the place to look for sustained high power; there are of course mountain grade where locos will have had to be worked flat out at the maximum end of their tonnage range, but a) because the speeds will be low, the cut off will be long, the cylinder efficiency down, and hence the maximum power will be some way below what the locomotive is capable of, as the Big Boy example shows) b) this is probably not typical of what they had to do over the whole trip: the short stretch from Cheyenne to Laramie is different to Laramie to Ogden or North Platte-Cheyenne. I don’t know what US freight speeds on reasonably flat terrain were, but am assuming it was probably at best 50 mph(?)), which will not require too much power - about 4000IHP with 4500 tons).
I have analysed the runs in the book, from Milwaukee to La Crosse. There is a northbound run with 100 plus 9 cars than got to Milwaukee in 73 minutes, 2 minutes inside schedule, having lost 3 minutes as far as Pacific Junction, possibly due to adverse operating conditions. Accelerating from Mayfair, #100 produced about 4000hp for a couple of minutes to get up to 90mph by Glenview. Thereafter, 2500-3500 ihp sufficed to cover the 56.4 miles on to Oakwood in 36 ½ minutes, maximum about 100mph. Coming south there is another run with 100, from Milwaukee to Chicago with 9 cars in about 68 minutes, net of a slowing at West Lake Forest, maximum claimed speed 110mph, well within the schedule and I suspect at the top end of the range of daily working. A full analysis is shown below; times were clearly noted at every milepost. Note that IHP rarely exceeded 3500 and was often less. The very detailed time course provided suggests there was a brief maximum of 107 mph just before Gurnee. The two claimed miles at 110mph are quite impossible- accelerating from 103-110mph over a mile is quite beyond an F7- an artefact of the timing process used!
Engine 100
Tare/gross wt
430/460 tons
Loco wt 395 tons
Total wt 855 tons
Miles
Schedule
Distance/cut off
Est speed
Log speed
Log time
Av speed
Av ihp
0
Milwaukee
0/25
0.01
01:38:03
1.1
Washington St
3
1.1/35
33.45
01:41:29
19.22
824
1.95
Kinnickinnic Draw
2.0/47
44.56
64/64/67/68
01:42:48
38.53
1923
7.55
Lake
9
6.6/65
72.59
75/78/88/92/92
01:48:24
60.13
3369
12.55
Oakwood
7.55/40
94.65
97/97/97
01:51:55
85.02
3505
16.05
Caledonia
9.2/44
95.49
97
01:54:05
97.33
3560
17.25
Tower A68
17
15.9/0
93.44
90/97/100
01:54:51
93.68
2671
19.3
Franksville
16.55/50
98.45
97/97/100/103
01:56:09
94.03
3919
23.5
Sturtevant
21
19.1/35
100.05
97/103/100/103
01:58:40
100.74
2833
27.65
Somers
22.6/0
102.97
103/103/103/103/103
02:01:09
100.16
2867
32.65
Truesdell
23/34
101.58
100
02:04:02
103.79
2587
33.65
Ranney
28
31.9/0
101.20
103/100/100/100
02:04:38
101.39
2770
38.1
Russell
32.65/32
99.87
100/100/100/103/100
02:07:19
99.37
2697
42.4
Wadsworth
34
38.6/45
102.45
103/110/106/103
02:09:51
101.86
3350
46.55
Gurnee
39.85/30
103.21
103/100
02:12:14
104.52
3366
48.35
Wilson
41.65/48
100.22
100/103/103/103
02:13:18
101.38
1962
53.1
Rondout
41
45.25/20
103.71
103/103/110/64
02:16:04
102.59
3642
57.05
West Lake Forest
48.2/44
71.96
73/78/88
02:19:14
74.87
-1700
61.1
Deerfield
51.5/40
92.87
88/90/97
02:22:07
84.39
4242
64.15
Northbrook
54.25 brake
95.14
103
02:24:00
97.05
2250
64.8
Tower A20
49
55.15/0
97.57
02:24:25
96.38
4844
64.95
Techny
55.75/60
98.10
92/100/103
02:24:30
97.84
4915
67.95
Glenview
59.05/46
100.89
02:26:17
3608
69.15
Golf
62.6/0
99.97
100/100
02:27:02
96.50
2253
70.9
Morton Grove
64.65/58
98.28
97/97/103/103
02:28:05
100.51
1300
73.65
Edgebrook
66.25/30
101.67
02:29:43
100.80
3720
75.1
Forest glen
69.1/0
68.81
72
02:30:41
89.17
-8437
76.45
Mayfair
70.5/48
51.58
46
02:32:20
49.32
-1908
77.25
Grayland
73.45/0
64.09
59/65
02:33:13
54.59
3848
79.05
Healy
Mostly
50.92
56
02:34:52
65.39
-843
79.9
Tower A5
Brake
48.02
02:35:54
49.04
135
79.95
Pacific Jn
62
and drift
48.65
02:35:58
48.33
2500
82.45
Western Avenue
28.80
02:39:11
46.56
-317
85.45
Chicago
75
0.50
02:47:39
21.26
-118
These and the other logs I have analysed suggest that a continuous output of 3500IHP from an F7 was more than enough to keep time with the standard load. Now there is also a report from the French Baron Vuillet that in 1943, an F7 took 16 cars from Milwaukee to Chicago in 63 minutes, averaging almost exactly 100mph from Oakwood to Edgebrook. This would require about 4200IHP sustained over the whole distance- perhaps a truer measure of what an F7 could do, though, I suspect, rarely required to. It is claimed that an F7 averaged about 120mph with 9 cars on test, and this would also require this level of power.
Now from some source or other, trustworthiness unknown, I have a blastpipe diameter of 7” for the F7. Using this, and making an intelligent guess on F7 superheat, I reckon that 3500IHP would require about 50000lbs/hr to the cylinders, and if all this went up the blastpipe (which it didn’t), this would give a backpressure of about 10psi, probably in truth nearer 8psi.
However, suppose what was actually required on a daily basis was more like 4500IHP. The rapidly rising backpressure means that efficiency would decrease and steam to the cylinders required would balloon to ca 72000lbs/hr, possible from a 96.5 sqft grate with Indiana coal, but seriously high blastpipe pressure. M. Chapelon could then claim he could deliver 10+% in coal savings, which would surely have got the MILW’s attention.
My underlying suspicion is this: everyone likes to quote what a steam class could do; it is reasonable looking at the data already to hand that if they operated at ‘could do’ level then improved front end design would lead to significantly more efficient locomotives; however if you look at ‘daily needed to do’ as the basis, most of the case against US front ends will disappear.
To understand this for other designs needs similar information on what they were actually required to do on a daily basis.
Now, whilst we had tens if not hundreds of folk timing trains all over our country with great precision from about 1900 on, so any train that moved was logged on some occasion, I’m not sure that detailed logs of the kind for 100 given above are common in the US. It would be great if they existed for the heavy high speed workings on the NYC, PRR, and Santa Fe, say, or any other railroad for that matter. If they don’t, just knowing typical loads, and schedules between the stops on say, the steam hauled 20th Century, Broadway and whatever the fastest steam hauled Santa Fe service was would suffice. The data would need to be for fast, straight stretches where it may be reasonably assumed there were no speed restrictions for curvature nor frequent speed restrictions for other causes, and what the speed limit, if any was. Routes that fit the bill would I think be for example Buffalo and Crestline to Chicago, Garden City to La Junta.
In all this, I am making the assumption that the second benefit of Chapelon style exhausts, namely providing more air to the fire, hence more reliable steaming was not really an issue in US practice, the need to operate reliably in harsh environments having already been given priority over other considerations. (It was in this country when people tried to draught increasingly large boilers with single blastpipes, in an environment where the distance between the top of the blastpipe and the top of the chimney was severely restricted by the loading gauge).
Thanks again for all your inputs.
Whenever I see a thread like this I usually do a quick google for the challenger freight video.
It puts it all into perspective. The fact that you have so much black smoke shows that there is a lot of unburned fuel/inefficiencies, but she is a beaut.
http://www.youtube.com/watch?v=XhgHrDbN4EU
Springfield PA
Volumes have been written on this! North American freight service, with a few exceptions, is NOT the place to look for continuous performance capabilities. Here are a few passenger examples. ATSF 4-8-4 classes worked 1791 miles, Kansas City to Los Angeles, 12 crews, Raton, Glorieta, continental, Cajon passes. Average engine worked 18 to 20 thousand miles per month. (2900 class 4-8-4 on freight service via Belen cutoff, only averaged 8000 to 9000). NYC 4-8-4 S-1b, in field tests, consistently produced 6600ihp at speeds of 75 to 85 mph and were capable of accelerating a 1000 ton train to 75 mph in 19,400 feet. They averaged over 20,000 miles per month. Kiefer was never able to optimze them because of dieselization taking place and bumping them from passenger service. SP GS3 regularly handled 925 ton trains up compensated 1.0% grades at sustained speeds in excess of 55 mph, which I believe is equivalent to about 5500ihp. NYC J-3a Hudsons worked the 20th Century, usually about 1000 tons, from Harmon to Chicago, 925 miles, in 16 hours with 7 intermediate stops. In practice the J-3a boiler, in line with most modern boilers, could produce more steam than the engine could consume. What made the J-3a so much more powerful and efficient was the care taken with the dimensions of live and exhaust steam passages and the high degree of superheat (about 750 degree F). J-3a's on average worked about 12,000 miles per month.
Not sure if this what you wanted. In any case it is just a sample.
"I’d like to understand; exactly how hard and for how long were US designs worked?"
Have a look here...
http://cs.trains.com/TRCCS/forums/t/161948.aspx?PageIndex=1
Great discussion, turning into a full time job to keep up!
I am in sympathy which most of what is written.
I do agree with CJ Hegewisch (12/04/11) that the perspective of operators was different to that of the gurus running testing stations. Our test stations were interested in cost savings from efficiency, because that is what they were designed to measure. Their work led to a few, trivial improvements to efficiency, all of which were ignored by the operators and not implemented. The only things they did that were accepted were to narrow the blastpipes of some designs, which made efficiency a bit worse, but improved the reliability of steaming. The basic philosophy (not well executed) of latter day UK designs was low maintenance. Efficiency was pretty good, but draughting stone age, because of the predilections of those in charge of design. Clearly if any feature which improves efficiency adds to maintenance costs, that needs to be factored in.
So, as Juniatha so eloquently puts it (13/04/11) efficiency is one thing, operating a railway another, and operational needs win out over efficiency if they are in conflict.
(Great memories of Hegewisch by the way; I remember well trying to walk from the station to State Line Crossing in a foot of snow, 13 degrees, early 1974, Train Watcher’s Guide to Chicago in hand. Crazy. Have a slide of an old CSSB unit there the following summer).
With respect to NM Coot 09/04/11, 10/4/11 and Juniatha 10/4/11 and 13/04/11 on the subject of Chapelon, he surely was one of the all time greats, and his designs demonstrated that. Juniatha’s stories of what he achieved are well known and oft repeated over here.
Secondly, it is in my experience nearly always the case that we often selectively cherry pick data to support our cases; A number of our 100ton (110US ton) Pacifics have achieved 3000IHP, one approached 3500IHP. Did they get anywhere near this in daily service? No. Could this have been expected? No, certainly not with handfiring, only at great inefficiency with Mechanical stoking. So, you will find me less interested in extreme claims, more interested in what operational practice and needs actually were, for this will determine how much benefit could be achieved e.g. by better draughting.
Whilst it is true that going faster and heavier, which is what efficiency allows you to do ought to be a universal good, experience over here says that speed and train length were not benefits always avidly sought. Those operators again.
Thirdly, with respect to his designs, the improvements obtained were simply by applying known best practice- three simple tenets, high superheat, low back pressure, high expansion ratio- nothing magic. (And, in the firing department, he was helped by Chauffeur Marty, who it seems was able to shovel approaching 10000lbs/hr of coal, for short periods at least. Over here, our guys seem to peak out at about 4500lbs/hr. Wimps. (I think I’m good for about 200lbs/hr)). High superheat was found in best US designs. Expansion ratio was sometimes poorer than it might have been because of the use of two cylinders only in many designs, which means that to generate high powers, particularly at low speeds you need to use longer, less efficient cut offs. However, I think it would be wrong to criticise this; I prefer to believe that the engineers had done their sums and in net terms, the simplicity of two cylinder designs far outweighed the benefits of going to more complex three and four cylinder arrangements, which could have operated more efficiently, except when they had no choice. So that leaves a draughting system with lower back pressure as the potential easy win.
As I said right at the beginning, it does seem to me that with 20:20 hindsight, it could well be that some US designs were suboptimal in draughting; this seems to me where Chapelon might have helped. I am interested in finding out if this is true, and whether under the operating conditions which were actually required, improvements would have made much difference. I suspect not, certainly not to a degree that would have saved the species for any length of time. There is no doubt, as Juniatha writes that with later European practice, e.g Chapelon, you can break the mould of the single blastpipe, where you do generally trade efficiency for steaming, and get the highly desirable combination of better draught and reduced back pressure. This would appear to be a low maintenance efficiency improvement that could have brought about some economy, potentially an easy win. How much is what I would like to establish.
Over here the high ups in British Railways were so anti fancy foreign practices that even the Giesl was killed off. In fact, this particular decision was not too unreasonable, since it turned out that the class on which it was tested were not often steamed at rates where its benefits would have kicked in. So the real issue was that the class was not being used to their potential. The Giesl could have been applied to good effect on other designs.
One of our railways, whose CME was a good friend of Chapelon, introduced Kylchap to this country; after his death, and following nationalisation and the expiry of the patents, it was widely adopted on their passenger designs, but only in the face of strong opposition from the top. Even as late as 1960 there is a vitriolic letter from a high up slating the use of such equipment, even though it had patently transformed the classes concerned. So I think an additional point is that, over here at least, design was determined as much by personal opinions and rivalries as rational considerations.
I agree with Juniatha’s critique that what I am interested in doing is looking back with 20:20 hindsight; I am not trying to resurrect the species, which is dead.
On Juniatha’s original input, point by point
1. My original query was exactly to ask what the backpressures experienced actually were. I am making no assumptions as to what they are. I agree that measurement is a problem. The model I use uses the standard equation for flow through a plain orifice, with the possibility of varying the discharge coefficient. This fits the measured values of blastpipe pressure with a discharge coefficient of 0.99 in nearly all UK tests. The exceptions are a) some higher values, when orifice plates, which I believe were a US invention were placed over the blastpipe nozzle. These reduce the discharge coefficient to 0.85-0.90. i.e. pressure is higher than it would be at the same orifice area without these devices. (Incidentally, although our blastpipe diameters were specified to the nearest 1/8”, and adjustments of that magnitude made, in service there could be deposits of up to ¾” of carbon below the lip- so clearly these locomotives would be very well draughted! b) lower values. These occurred in three cases. In two cases this was due to the pressures being measured at the base of the blastpipe stand, and there being very slight taper in the blastpipe. Allowing for this, the predictions are spot on. The other exception was the Lemaitre set up, where pressure measured was a bit below the theory. I have not investigated the reasons for this.
2. I was specifically vague about the Niagara blastpipe pressure at high outputs, because there are lots of unknown factors. Precisely what it is, is part of data that I am looking for, and precisely what I think it should be will fall out when I have other design details. My programme gets the pressure for the Q2 more or less spot on. It says the T1 had a free nozzle area equivalent to ca 8” diameter- this must be a matter of record, so this will say how good the programme is for this type. The T1 was 29 psi at 100000lbs/hr. The Niagara had a diameter of 7.5”, so by my estimation it would be higher, and the relationship is not linear. And the higher the backpressure, the more steam you need to generate a given power, so at a given target power you lose twice. So I don’t think my approaching 40 psi is too far wrong and I’ll wager it’s not too far out. We’ll see. The programme says at 52500lbs/hr the Niagara nozzle was behaving like 7.2”. This could be a measurement problem, a design feature, a build up issue, or a small inadequacy in the programme.
3. The H8 quote is from a very respected British Engineering Journal, quoting in great detail what I suppose are primary sources; some of the original graphs are included. Blastpipe pressures are given for both front and back engines, the former being somewhat lower than the latter. The 13psi is a fair average of back and front on the highest rate test, where the evaporation is quoted as 100800lbs/hr, the tank feed 91300lbs/hr. I understand the question of where the measurement was made is important (See above), and this may lead to misleading values.
4. Firstly I should say that in UK testing, the difference between exhaust port pressure and blastpipe pressure was negligible, especially considering the difficulties in measuring both temperatures and pressures of fast moving steam. On your comments about the Gresley set up, you make assertions, but provide no facts. The facts I know of are these a) There are plenty of UK tests on engines with similar lap to the original A1 that show no deficiency in thermodynamic efficiency. b) tests on the original short lap A1 showed the steam chest pressure was typically about 110psi. So, to develop any kind of power, engines of this size had to be worked in 50+% cut off at speed whereas the later designs with longer travel valves were worked at full pressure in ca 30% cut off. This makes a big difference to economy. c) one of the high preists responsible for perpetrating the original efficiency story recanted once he’d figured out what the computer programme was doing and saying d) At around the time the valve gear design was changed the superheat was also increased, then boiler pressure, which is why the A3 and A4 were more efficient still. I agree that the performance of the original Castle it was compared to with was far from inspirational. The claimed 2.83 lbs coal/dbhp for that design is quite unrealistic, as later tests showed. I think I’ve figured out how the 2.83lbs claim was made; a little not unreasonable leger de main was involved to generate a great publicity claim. Like all claims, once you’ve made it, it’s very hard to deny it. (The reason the Castle got to Plymouth faster was basically that the own line driver ran through speed restrictions over the limit. The A1 was actually developing more power going uphill, but because it weighed 30 tons more it didn’t go much faster). I’m not claiming that high MEPS generated in long cut off are not a bad thing- of course they are; but as noted above they are a consequence of sticking with 2 cylinder designs. My point’s a bit more subtle, but I’ll spare everyone that.
5. I agree I’m not taking pumping efficiency into account; I’m rather assuming that everyone understands that with more sophisticated exhausts you can, as noted above get a highly desirable reduction in back pressure whilst actually improving pumping, so, reducing back pressure looks like a bit of a no brainer now.
6. More than happy to look at the differences between the German types if you have the relevant dimensions.
7. Well, I suppose that’s another thing I’d like to understand; exactly how hard and for how long were US designs worked? I could ‘build’ the line from say North Platte- Cheyenne- Laramie, and if people have passenger and freight schedules, and tonnage ranges, I could work out how much power was actually needed on this long uphill stretch. Experience in this country says that whilst the draughting usually allowed 800-900lbs/sqft/hr evaporation, 1050lbs/sqft/hr on occasion, much over 600-700lbs/sqft/hr was rare. Maybe it was different in the US. That’s what I’d like to find out. But even the 20th Century only averaged 60 mph, and that on a Water Level Route.
Nor is it topical.
daveklepper Just for the record, N&W diesilization started with the Harrisberg Lline and its 4-8-0's....
Just for the record, N&W diesilization started with the Harrisberg Lline and its 4-8-0's....
No it did not!
.
Last operating steam on NKP was an 0-8-0 at Calumet Yard.
Just for the record, N&W diesilization started with the Harrisberg Lline and its 4-8-0's. Plus, of course, replacement of J's by run-through Southern Ry E-Units Monroe - Bristol.
blue streak 1 J: I believe that N&W retired their big steram last Switchers were first to go in my area.. I think that a "Y" was the last to drop its fires under regular service. Anyone more info?
J: I believe that N&W retired their big steram last Switchers were first to go in my area.. I think that a "Y" was the last to drop its fires under regular service. Anyone more info?
An S1 or S1a was the last to drop its fire. Sorry, don't have the exact engine # at my desk, however, it was written up in "Classic Trains" mag a year or two ago.
Well , I see what you mean . I agree with you as regards virtues of American Super Power steam . Yet , may I kindly invite you to read my paragraph on why the 141.R out-lasted the 141.P on the SNCF ? In a nutshell :as far as decisions were taken upon technical reasoning – there were numerous other considerations playing a part in which steam on which lines of which sheds etc had to go first – it was not regarding matters thermal efficiency in any which way , it was because of lower maintenance of the newer and more numerous , standard engine against the older and more traditional mechanical design in view of lesser assignments of steam where highest specific outputs were no longer needed . The Achilles’ heel of the 141.P was their out-of-date mechanical design inherited from PLM predecessor 141.D . However , composite plate frames and plain bearings of traditional design for instance were neither stringently correlated with nor sequel , effect or outcome of high (or low) thermodynamic efficiency . As a matter of fact , the mentioned Chapelon engines all were rebuilds of old engines inevitably inheriting old fashioned concepts of construction , mind it ! In contrast , the engines he had planned were to be of the same standards of mechanical design as was then practiced in the States – so where , then , was the difference upon which to state those engines would have been more costly to maintain ? Or in simple words : higher thermodynamic efficiency in cylinder work did not as such necessarily demand any extra expenses or complications in mechanical construction and therefore didn't have to change maintenance costs either . A steam loco of higher thermodynamic efficiency wasn't costlier to maintain just because of its high efficiency . Or in other words : you can't save on maintenance costs by sending consumption soaring . And further : costs of running coal traffic for locomotive coal were one of the issues that stood against steam ! The higher fuel consumption for a given work , the more fuel needed , the more traffic for loco fuel , the more costs for loco fuel and for bigger tenders (which added up to locomotive total mass and reduced edbhp for same ihp [2] ) and so on . Efficiency did matter in the steam / diesel competition years . [1] Coming back on the 242.A.1 – this also was a rebuilt engine . Still the 241.P based on the PLM 241.C.1 prototype was chosen for building a final series . This design concept was inferior both thermodynamically and mechanically at the same time , suffering for instance from overheating crank axle bearings and crank axle crackings and thus clearly was second choice in comparison to the 242.A.1 having a much sturdier single crank axle and no problems with it . [2] So , where was the advantage gained for maintenance by sacrifice of excellent efficiency and performance for second choice ? In fact , in determining decisions as to which designs were chosen there were other than technical reasons as I had already hinted with the pathway of the Berkshire / Mikado project . The American Super Power types certainly were magnificent engines for their time – no doubt about that . However , to propose they could not have been improved and improved upon would mean to deny technical progress . Let's not forget more than half a century has passed since these things were an issue . So , we don't need to get too deeply involved in all that , I don't think there is too much in discussing matters all over again . We will never find an undisputed lasting truth that would apply in general – too widely differing were the circumstances and the influences that intervened and played a role . Who was to decide what was right and what was wrong in individual decisions ?
Well , I see what you mean . I agree with you as regards virtues of American Super Power steam . Yet , may I kindly invite you to read my paragraph on why the 141.R out-lasted the 141.P on the SNCF ? In a nutshell :as far as decisions were taken upon technical reasoning – there were numerous other considerations playing a part in which steam on which lines of which sheds etc had to go first – it was not regarding matters thermal efficiency in any which way , it was because of lower maintenance of the newer and more numerous , standard engine against the older and more traditional mechanical design in view of lesser assignments of steam where highest specific outputs were no longer needed .
The Achilles’ heel of the 141.P was their out-of-date mechanical design inherited from PLM predecessor 141.D . However , composite plate frames and plain bearings of traditional design for instance were neither stringently correlated with nor sequel , effect or outcome of high (or low) thermodynamic efficiency . As a matter of fact , the mentioned Chapelon engines all were rebuilds of old engines inevitably inheriting old fashioned concepts of construction , mind it ! In contrast , the engines he had planned were to be of the same standards of mechanical design as was then practiced in the States – so where , then , was the difference upon which to state those engines would have been more costly to maintain ? Or in simple words : higher thermodynamic efficiency in cylinder work did not as such necessarily demand any extra expenses or complications in mechanical construction and therefore didn't have to change maintenance costs either . A steam loco of higher thermodynamic efficiency wasn't costlier to maintain just because of its high efficiency . Or in other words : you can't save on maintenance costs by sending consumption soaring . And further : costs of running coal traffic for locomotive coal were one of the issues that stood against steam ! The higher fuel consumption for a given work , the more fuel needed , the more traffic for loco fuel , the more costs for loco fuel and for bigger tenders (which added up to locomotive total mass and reduced edbhp for same ihp [2] ) and so on . Efficiency did matter in the steam / diesel competition years . [1]
Coming back on the 242.A.1 – this also was a rebuilt engine . Still the 241.P based on the PLM 241.C.1 prototype was chosen for building a final series . This design concept was inferior both thermodynamically and mechanically at the same time , suffering for instance from overheating crank axle bearings and crank axle crackings and thus clearly was second choice in comparison to the 242.A.1 having a much sturdier single crank axle and no problems with it . [2] So , where was the advantage gained for maintenance by sacrifice of excellent efficiency and performance for second choice ? In fact , in determining decisions as to which designs were chosen there were other than technical reasons as I had already hinted with the pathway of the Berkshire / Mikado project .
The American Super Power types certainly were magnificent engines for their time – no doubt about that . However , to propose they could not have been improved and improved upon would mean to deny technical progress . Let's not forget more than half a century has passed since these things were an issue . So , we don't need to get too deeply involved in all that , I don't think there is too much in discussing matters all over again . We will never find an undisputed lasting truth that would apply in general – too widely differing were the circumstances and the influences that intervened and played a role . Who was to decide what was right and what was wrong in individual decisions ?
There is romance in steam's lost case and we like to ponder it and contemplate what could have been – that's all . We should never forget about our hindsight perspective . I've offered my view – no insult intended . That said , I step out of this thread . Don't get at loggerheads about this matter , folks – the locomotives never come back anyways . [1] Regards Juniatha
There is romance in steam's lost case and we like to ponder it and contemplate what could have been – that's all . We should never forget about our hindsight perspective .
I've offered my view – no insult intended . That said , I step out of this thread . Don't get at loggerheads about this matter , folks – the locomotives never come back anyways . [1]
Addenda :
In view of the latest post commenting on comparison of SNCF Mikado types 141.P and 141.R I feel obliged to disclaim what seems to be a miss-interpretation of my comment written earlier on this matter . Inviting to re-read my text , I pointed out reasons why SNCF concentrated dwindled remnants of steam loco park on mainly one loco type , the 141.R , were largely disconnected from engine-technical considerations . Quite certainly , the fact a small number of 141.R engines outlasted practically all other types of steam on the SNCF was caused by vastly eased demands of engine performance with steam traction at that stage during the transition having dramatically lost mainline assignments – all first class train running handed over to electric traction and much of the more important secondary train running done by diesel traction , 141.P high performance standards were no longer needed . To secure remaining few secondary and lower ranging traction services , SNCF therefore preferred to keep the 141.R Mikado because of universal presence on the system , younger age , more sturdy construction and simplicity in design , parts being readily available .
No conclusion can be drawn on that in trying to find an answer to the age-old steam design issue ‘two cylinder simple expansion against four cylinder compound’ . There never was anything like the colloquially alleged ‘mass engine competition test’ carried out on the SNCF and thus , logically , there could be no winner. The question which of these two series of Mikados , 141.P or 141.R , was ‘more efficient’ could not be answered in such a widely undefined , general way – simply because engine characteristics vastly differed . Looking at heavy express run assignments formerly steam handled , the ‘P’ could clearly outperform the ‘R’ ; the ‘P’ could handle demanding runs the ‘R’ lacked both speed and power for – that left the ‘P’ without alternative in this class of train running . At the other end , in low ranking secondary train traction where performance was of little or no importance , clearly the sophistication of a 141.P was not needed . Yet , steam depots in the western part of France continued with their 141.P engines in such services as long as they kept steam running , never asking any 141.R for replacement . Both ‘P’ and ‘R’ stoker fired , the ‘R’s coal consumption was vastly higher at both ends of performance range – at the upper end because of degraded combustion efficiency and lesser thermo-dynamic efficiency and at the lower end because of grate too large for this sort of service . Yet , the ‘R’ was better digesting indifferent coal qualities because of larger grate and sharp draught . In average freight traffic , there was an advantage with the ‘R’ that grew with increasing load and decreasing speed (until getting at a disadvantage against the 150.X , German 44 class , in what was a good working range of that three cylinder Decapod) – yet this was not so much a question of two against four cylinders as it was a profit gained by sturdier construction with cast steel locomotive bed, Franklin automatic wedges , roller bearing on axles , boxpok drive wheels and a very good boiler design for high steaming rate . Beyond the obvious difference in cylinders , ‘P’ and ‘R’ differed drastically in mechanical design and this blurred any practical comparisons of maintenance costs as to seeking an answer to the old ‘two cylinder SE against four cylinder C’ issue . So , in actual service at different regions and in various qualifications of service there could be all sorts of answers to this issue – even on the same railway system ! I think this explains why there never was and never could be a definite answer found or agreed upon in the perennial ‘two cylinder SE against four cylinder C’ issue .
Edit (lighter shades of color) :
sentences added [1]
sentences clarified plus two missing words added [2]
Addenda inserted on issue two cylinder simple against four cylinder compound [3]
It's time to throw a bomb into this discussion. Chapelon's 242.A.1 may have pointed the way to improved efficiencies and performance, but that won't mean too much if such locomotives spend an inordinate amount of time being maintained. French steam was alloted a lot more shop time than would be tolerated by a North American CMO, so the fuel/maintenance trade-off needs to be considered in any discussion of efficiency. Vernon L. Smith, longtime Superintendent of Motive Power of the Belt Railway of Chicago, opined that North American steam locomotives were the best at what a locomotive should do by producing more ton-miles and passenger-miles with less down time than anywhere else.
Hello All
It wasn't my intention to divert the thread. It was my intention to indicate that you can't consider either predicted or actual performance without taking Chapelon's work into account. North American practice has always differed significantly from the rest of the world. The rest adopted some of the best NA practices, but it seems to me the converse is not true. I did try to indicate that what Chapelon achieved with 242.A.1 was simply a starting point for what could be achieved. Other engineers offered changes with considerable potential improvements. For example, Bulleid's concept for oil-bath valve gear was a massive conceptual leap but was let down by very poor detail work. Having said all this, the classic Stephenson steam locomotive could never compete with either electric or diesel-electric performance or operational benefits. But it is interesting to speculate on what could have been...
Three men, two 4-8-4 and one valiant Mikado
Ok, NM Coot, you put attention on André Chapelon – and rightly so: no discussion on steam locomotive efficiency could be complete without due consideration of his work. So far, I for one had kept my comments strictly limited to the initial topic of this thread, more precisely: the question in mind if locomotive performance and efficiency can be ‘predicted’ (questionable wording in view of ol..erh, classic! engines) respectively, can it be assessed closely enough and with tolerably correct correlations between various types of engines? So far, I didn’t want to extend discussion onto ‘how to optimize classic steam loco efficiency?’
In my remarks on draughting I was already hinting it would actually take more than just widening blast nozzle area if you wanted to lower back pressure at cylinders while to ensure gas pumping capacity always remains slightly above demand of complete combustion (i e λ ≥ 1.0 up to nominal boiler steaming rate, wherein ‘nominal’ is somewhat relaxed from maximum (like nom ≈ 80 to 85 % of max) if ‘maximum’ is correctly defined by grate limit, not by premature front end limit or by secondary considerations).
The Kylchap, often used in double arrangement on larger European engines, for a long time featured the highest pumping efficiency with neither Bulleid, nor Ister, nor Kiesel, nor Jabelman multi nozzles types coming close in performance and extent of efficient working range. In post WW-II years, an at least equally high if not superior efficiency was claimed for the Giesl ejector with Adolf Giesl-Gieslingen himself pointing out simplicity of his device, its ease of installation and (claimed) self-adjusting and the advantage gained by slimline shape of improved access to smoke box tube plate for cleaning and maintenance. A direct comparison of performance between Giesl ejector and double Kylchap on two engines of one suitable class of locomotive should have been interesting but I have no knowledge of it ever having been done; testing a double Kylchap 556 against a Giesl 52-80 light Decapod would have come closest – likely however, no comparative tests have been made, or I haven’t heard of it, since the classes were of different, if neighbouring, state railways: DR (Deutsche Reichsbahn) and ČSD (Československé Státní Dráhy). Drawing conclusions from what I know of relative performances of these locomotives it would appear it’s a close cut with the Kylchap 556 almost as much heavier as superior in maximum power output at speeds above some 40 mph – yet in absence of established data it is left to conjecture how much of that must be attributed to somewhat larger if closely similar boiler (equipped with stoker firing) and more efficient cylinders of slightly smaller relative volume (556 class b p of 256 psi against 228 psi was only 95 % of pressure for same t e with 21.7” x 26” as compared to 23.6” x 26” cylinders and identical 55” wheel diameter, disregarding difference in adhesion mass).
Later, Livio Dante Porta evolved the Kylchap into the Kylpor and from that derived the Lempor type, involving a Kordina and vortex or swirl flow of steam from blast nozzles. As by diagrams put up by David Wardale with these types of draughting devices even higher pumping efficiency can be reached. However, implications of these techniques must be considered with some caution. These highly effective draughting devices may lead to heftier than ample air aspiration through grate and firebed with abortive rather than supportive effects to continuous up-keep of combustion. Basically, these devices were developed with regard to running a thick firebed as used with gas producer combustion, involving a high degree of secondary air induced above the firebed.
Wardale has described intricate teething problems with his rebuilt 19-D 2644 to keep the firebed from being partially lifted and tumbling towards the front of the grate. I could imagine the typical railroad steam testing department having given up after a number of runs to just dump that tricky matter including rebuilt engine(s). While a comparatively steep incline of grate in the 19-D class certainly was not supportive of thick firebed plus high draught operation, Wardale identified several further adversely influencing factors and by scrutinizing sequences of testing / analyzing as well as committing co-workers and crew he was able to sort things out in the end. By reading his account on the testing period I got the idea these late hour advancements while holding a promising potential to increase both performance and efficiency of coal fired steam locomotives have much remained in a prototype stage of development (in spite of a time of regular running on the quite special Rio Turbio) and are far from simple to realize, keeping in mind Wardale’s noting of continuous and close support by Porta. This is not the sort of technique to put into effect hands down by your average preserved engine group. In the end, goals very much were accomplished with 2644 ‘Spooky’ and 3450 ‘Red Devil’ – in view of time then running out fast for steam on the SAR during the very years of rebuilding and test running these engines, they should be considered about as much of a success as could be realized under ruling conditions. While his superiors choose to remain blind for reasons obvious, I can read between the lines how reassuring it must have been to Wardale when the driver of 3450, ascending a bank at exceptional speed yet on shorter than usual cut off, in plain words summed it up by stating “there is a difference!” The engine certainly performed inspiring.
Much could be commented on the admirable 242.A.1 – a rebuild prototype to a proposed new family of types, an engine that stood all road tests, shattering established marks of steam traction top performance in France on any mainline tried and even beating electric traction on two runs Paris – Le Mans, arranged at a time when plans for Chapelon’s proposed family of new steam had been shelved and construction of the 2-10-4 had been cancelled in pretense of an alleged shortage of coal which was more likely imagined by politics than real, transient at any rate and concerning grades of coal used by steel industries rather than the railways. The proposed line of three cylinder compound 2-8-4, 2-10-4, 4-6-4 and 4-8-4 of 6000 ihp nominal output were to have many components in common, design incorporated many modern features of American practice which Chapelon had seen and appreciated during his visit to the United States.
As things turned out, this was not to be. However in the years of high hopes during tune up at Vitry and trial running the 242.A.1 attaining 5500 ihp, the series of test runs on the Ligne Imperiale, the classic mainline of the old PLM (Chemin de Fer Paris Lyon Mediterranée) passed with flying flags with a formidable sustained speed on the long 1 in 100 ascent to Blaisy Bas by the first and only 4-8-4 in France – Europe’s most powerful steam locomotive – marked André Chapelon’s triumphant return to the railway of his beginnings, the railway he had initially started to work for because of his early admiration of trains passing by on the PLM line near his parents house in a town in the vicinity of Lyon. However, leading heads of the engine department had turned down his ideas of technical optimization of existing locomotives and so he had left the PLM and ‘went west’ so to speak, to join the PO (C d F Paris Orleans), later PO-Midi, in the western part of France and covering hilly lines over the Massif Central. There, he found his proposals well received and in 1929 first materializing in Pacific 3566 massively rebuilt to his design. The story of success written by this engine and the following, renumbered 3700 series (later 231.700) is well known. Astonishing as these engines performed, they were topped when Chapelon even more radically transformed a number of smaller 73” wheeled Pacifics into 4-8-0s (4700, later 240.700) followed up by more rebuilts in the early years of SNCF, séries 240.P, shortly before WW-II. It was one of these engines that turned out 4700 ihp at continuous rating (real time steaming at constant water level) marking the highest specific power output per unit of engine mass to that date. It was with this series Chapelon engines started intruding the Ligne Imperiale as the smaller 4-8-0s vastly outperformed the large boilered yet cumbersome PLM Mountain types of various configurations of cylinders and drive axles of 79” and 71” wheels (PLM séries 241.A, .B, .D with prototype 241.C.1 and rebuilt 241.E).
With SNCF André Chapelon having been appointed head of the DEL (Division d’Études de Locomotives – locomotive development division) a new Berkshire type (pardon my expression) four cylinder compound of 5000 ihp was being considered. However with the onset of war, the PLM league had fought off what seemed hard to accept with established thinking and in view of austere times managed to bend the project into a Mikado basically intended to be an SNCF follow-up series of the PLM 141.D. Chapelon was then trusted with the task of turning a tolerably mediocre design into a good one – hopefully without changing all too much. In 1942 this gave birth to the 141.P series, the first lot allocated to high ranking Lyon-Venissieux, mainly for passenger service on the Ligne Imperiale. These were soon followed by more engines until later on early Lemaitre engines were exchanged for Double Kylchap engines and a number of the former got shelved serviceable in nearby yards (while lesser ranking sheds continued with old 141.D). The petite slender yet athletic 285 psi, 65” drivered four cylinder compound Mikado featured a steam flow arrangement reversed from the old 228 psi PLM design with l p cylinders now between frames while below the deflectors compact h p cylinders with large steam passages for live and receiver steam flow were set slightly angled to better comply with the angled position of the inside drives. Mechanically, the well balanced engine unit was designed for 150 km/h (93 mph), in actual service speed was limited to 120 km/h (75 mph). Power output characteristic differed from the original PLM Mikado as a superheated steam engine differed from its saturated predecessor: while output curve of the old 141.D leveled off at some 2000 ihp around speeds below 60 mph starting to fall off towards higher speeds, the 141.P curve kept climbing throughout the tested speed range reaching some 4000 ihp at 75 mph without attaining a maximum level – i e what had been a rather dull mule had been re-designed to become an exceptionally free running sparkling universal performer.
When the PLM mainline was electrified in the early 1950s, many 141.P were sent on a tramp never really ending to the last of their miles. With 318 engines built between 1942 and 1952 by several manufacturers – or ateliers, as railway workshops are sometimes called in France – during the main period of transition from steam to electric and diesel traction on the SNCF, from mid fifties to mid sixties, 141.Ps could be found at the head end of about any sort of train on the SNCF from miscellaneous freight to heavy express as well as any odd jobs on rural country lines while with electrification expanding and first class assignments getting lost to steam, increasing numbers became shelved with a cloudy future on doubtful tracks in the quietness of weeds detached from the busy centers of the roundhouse yards.
American built two cylindered 141.R proved better withstanding reduced maintenance and neglect as in the twilight of steam traction the formerly prevailing system of fixed assignation of engines of major classes to permanent crews had been replaced by common user system. The 141.P’s Achilles’ heel was their PLM design ancestry, mechanically out of date in certain ways from composite plate frame structure to plain bearings throughout or boiler with small firebox. ‘Les R’ as they were tersely called were less demanding in maintenance, yet reliable and thus ‘destinée d’écrire la dernière page de la vapeur sur l’SNCF’ – destined to write steam’s last page on the SNCF.
In his 1952 proposal of future high performance types of steam, André Chapelon was to conjoin the best of American practice in mechanical design with advanced thermodynamic design features – or in presenting his paper at the Arts et Métiers in Paris he offered exactly what was perceived as worst case by those who were already planning for steam’s abdication …
Juniatha
front elevation of planned Chapelon / DEL 152.Q – drawing: SNCF / bearings added plus coloring: Juniatha
In all the discussion on this topic I'm really surprised to so rarely see the name Chapelon mentioned. His designs and performance standards really exceeded everything being discussed in this thread. The ultimate steam locomotive, 242.A.1, was a rebuild of a poor performer and comfirmed Chapelon design principles and showed what could be possible in the future. Both his original designs and his rebuilds of poorly performing engines gave dramatic increases in power with significantly reduced fuel and water consumption. In North America, compounding had a horrific history and would never be accepted. That left 1, free exhaust clearance, 2, soft but effective exhausting, and 3, relatively high super heat to increase steam fluidity. I previously mentioned Chapelon's own book but there have been others that give considerable detail for both test bank and field trials of his locomotives.
Imagine a steam locomotive capable of continous output of 4000 hp at the drawbar at 50 mph on the test bank and 4000 to 4200 hp on service trains. Total weight was 148 tons and adhesive weight was 84 tons. Boiler pressure was 292 psi and a triple klychap exhaust was fitted. The grate was 54 sq ft. Because of the three cylinder configuration the locomotive showed no tendency to slip even at maximum outputs.
if you want dream steam imagine a Chapelon-designed 4-8-4 to the North American loading gauge. (Or better yet, a Chapelon-designed Garratt 4-8-4+4-8-4...) No North American locomotive would even come close either performance or economy.
@ Dreyfusshudson
A few more notes
quotes in >> French Croissants <<
– 1 –
>> Now these backpressures look horrendous to European eyes <<
Umpfhh - erh, do they, really? well, maybe to eyes in 'Old Europe' as Rumbling Rummy would have said ;-) From your previous postings I thought you knew these back pressures since originally you stated that the formulae you work with would allow to predict performance (basically) from just three parameters and back pressure was one of them – although not precisely defined where measured?
– 2 –
>> .. Niagara already a back pressure of 10 psi at 52500lbs/hr, 44 sqins blastpipe, which means that at the quoted rating of 6000IHP the blastpipe pressure would be approaching 40psi! <<
That compares ‘back pressure’ against evaporation on one hand with ‘back pressure’ against cylinder horse power on the other. Back pressure essentially depends on mass rate of steam flow and steam temperature for a given design of blast nozzle. It is not the same for different shapes and designs of draughting blast nozzle(s) of given numerical free cross section tip area at given steam flow! As I remarked on the Porta statement: draughting could have been a lot worse in that poor dimensioning would have produced much higher back pressures with same numerical cross section nozzle tip area or produced much less draught at same given back pressure. To make it plain and simple: Porta’s statement, as I had modestly let on before, was characterized by his eagerness and love of exaggerations – thumps down for anything FGS / thumps up for his SGS. In this context, mind that given parameters were severely constricting design of draughting arrangement with large engines and inevitably it got worse with larger diameter of boiler within a given loading gauge!
Further, an extrapolation of back pressure from a given lower steaming rate to back pressure at an upper steaming rate about double the former, first of all needs to take into account the specific flow coefficient and the pumping efficiency curve of that draughting arrangement – only to remain a vague enough approach with an exponentiated rate of inaccuracy as the quotient higher : lower steaming rate increases. Again, there is a decided difference between round nozzles of plain ordinary type and De Laval type as in the Niagara! Not to mention effects of a – properly designed – Kordina! Without knowledge of the design specs and behavior of the draughting this numerical extrapolation will lead astray. That is probably why your estimate back pressure (40 psi) for the upper steaming rate is way too high. The draughting arrangements of the NYC S-1b vs PRR T-1 (non-regarding the Q-2) were not directly comparable for several reasons and showed characteristic differences in performance. The UP Jabelmann double arrangement of the 4-8-4 (again the Challenger and BB should not be considered in this comparison) was as inferior in some aspects as it was superior in other ways.
– 3 –
>> .. C&O H8 which showed around 13psi at the same steam rate <<
Ooops ?? where did you get that figure from? Without considering very special interfering conditions this would appear an exceptionally low figure, actually unwarranted. In SE Mallet type locomotives there is a long exhaust line from the second drive unit cylinders to the draughting, therefore it would be all the more important to know exactly where this ‘back pressure’ has been measured. Principally, for a number of reasons inherent with basic arrangement of live and exhaust steam conduct in these engines as they were, back pressures on pistons were rather higher – not lower – than in ‘straight’ engines i e of but one drive unit with cylinders under the smoke box. In SE Mallets, what percentage of back pressure on piston would then have been left as pressure at blast nozzle(s) highly depended on the degree of free or not so free flow of exhaust steam to that nozzle(s) and could indeed vary widely.
– 4 –
>> Firstly the % loss of efficiency you get from high back pressure decreases as MEP rises << and
>> US MEPs it seems were higher than elsewhere <<
Why, actually it doesn’t. Again, it’s important to distinguish between back pressure on piston and ‘back pressure’ somewhere in the exhaust line or pressure at blast nozzle!
For an increment of exhaust pressure base line in the cylinder, for example from 10 psi to 20 psi, including consequential higher compression – provided the higher exhaust pressure base line does not lead to over-compression! – the absolute amount of lost energy conversion is directly proportional to the diagram area defined by the two exhaust pressure and compression lines from exhaust lead opening to admission lead opening. Never mix intake and expansion processes with exhaust and compression processes. In the Walschaert’s / Heusinger valve gear characteristics on both sides of the piston are mechanically interconnected but that does not say losses on the exhaust side could be compensated or downsized by beefing up on the intake side.
In fact, evaluating progression of steam pressure on the intake side during admission and expansion has to distinguish between depression by throttling or drawdown by expansion. As I understand, in paragraph three of your reply to me, you postulate valve gear characteristics while not irrelevant are of but small influence. Next, you offer the known example of the Gresley A1 valve gear redesigned for the A3, where, to quote >> well told story .. about how changes to these settings led to a massive improvement ..<< were proven by your program to have been >> wrong << and instead >> the benefit was all about the redesigned gear being able to operate in shorter cut off compared to .. the original design. << Well, now that exactly was the difference the redesign (basically from short lap to long lap) did make and that was what yielded higher thermo-dynamic cylinder efficiency in the A3 and in the A4 further improved along the same line of development, allowing higher outputs in the upper speed range, and higher rpm speeds the A1 did not reach. So, it did make quite a difference. After all, it is known the original A1 proved a slouch, frankly, when in the exchange trials it was compared with the Swindon Castle class four cylinder simple – which by itself certainly was not too inspiring in thermo-dynamic cylinder performance with its valve gear mounted between frames and derived piston valve actuation on outside cylinders (quite the opposite of what would have been mechanically preferable) and with Churchward’s cherished low degree superheating.
However, as you acknowledge, to quote from paragraph four in your reply to me, >> beyond 40 % ‘very big’ differences << we would agree there is a decided loss in cylinder efficiency at c/o ~ 50 % or over as often found in large American loco types at flat out performance. High >> US MEPs << were thus no protection against losses by elevated exhaust back pressure. On the contrary long c/o caused losses by truncating expansion rate. To claim with these high mean cylinder pressures, increased piston back pressure didn’t matter much would mean to suggest when driving a Big Block Chevy of the early years of unleaded gas and catalyser, a badly tuned 4 barrel carb doesn’t make much of a difference in mpg.
– 5 –
>> If one were to set a design goal of a back pressure of no more than 5 psi at some maximum design evaporation rate- let’s say 800lbs/sqft/hr, i.e. before boiler efficiency really plummets, then .. a blastpipe area sqins of 0.887* grate area in sqft- 2.14 would be required, so the target for a Niagara would be 86.5 sqins, for the Q2 about 106sq ins, about double what they had <<
You never seem to account for pumping efficiency of draughting and for boiler characteristics, incl grate and firebed resistances. Principally, with draughting arrangements as they were, already compromised in proportions by inevitable restrictions of loading gauge, just to increase the cross section of blast nozzle(s) would have lead nowhere. This sort of ‘re-draughting’ would simply have repeated faults that had been found in the German Reichsbahn standard types intendedly equipped with Wagner ‘wide’ blast nozzles in an effort to minimize piston back pressure. While with these comparatively light designs in contrast to the massive American engines here considered the desired design aim was reached tolerably well, effect on draughting left something to desire. A suggested ‘Super-Wagnerization’ of American engines would have taken out draughting to a much more serious degree and reliable steaming could no more have been sustained even at moderate steaming rates!
Although steam locomotives weren’t too complex as compared to more modern engines, they represented the type par excellence of inherently interweaving, interrelating design characteristics in most all of their components and functions. That is why no item could be modified without effects on several related elements and according changes needed to be made to the whole chain of functions if any real advantage was to be realized. That was one of the underlying basics of steam locomotive design obviously not fully appreciated, to put it mildly, by many designers, engineers and craftsmen. It may well be so your formula would predict an increased performance by super-enlarging blast nozzle(s) – yet in reality the contrary would have happened.
– 6 –
>> Exhaust design is historically a trade-off between steam raising ability and back pressure; in the UK, and I guess everywhere else, steam raising won out over backpressure i.e. efficiency every single time. <<
If the first part aims at balancing draughting arrangement between lowered piston back pressure and increased draughting over a wide range of steaming rates, then there is something in it, if considerations are strictly limited to single, round plain nozzle, single round chimney type of design – and then it still lacks to take into account boiler design in view of gas flow resistance.
As for the second part: on British Railways steam locomotive design in the 1950s had been decidedly advanced by Riddles in general – famed for his 9F Decapod were ‘F’ actually proved to stand for ‘fast’ as much as it was meant for ‘freight’ – and by S O Ell developing his theory on draughting, enabling a couple of engine classes formerly notorious for bad steaming to shape up with new draughting arrangements fitted. In France, SNCF equipped a large number of engines with more or less sophisticated draughting arrangements and attained – more or less – substantial improvements in reaching both aims at the same time: good steaming and low back pressure. In Germany, with introduction of standardized design of Reichsbahn series, ‘soft’ draughting intentionally preferred low back pressure at the expense of compromising steaming rate ceiling; the rather extreme original proportions were set right on DB by the 1955 re-draughting campaign while on DR improvements to grate, air conduct to grate and ashpan design were introduced with or without Reko type combustion chamber boilers which proved steaming well with Wagner type of draughting because their characteristics were especially designed to suit. This did not mean the same boilers wouldn’t have steamed even better with more advanced draughting arrangements but this never materialized as the Giesl engines were used to burn low grades or indifferent mixtures of coal.
What should have been expected of a reboilered 5035 or 5280 class light Decapod with high efficiency draughting can be concluded from CSD 556 series Decapod of sensibly similar leading dimensions if at 99 t compared to some 90 t of the DR classes. With a very similar if slightly larger boiler these engines equipped with double Kylchap attained 3000 ihp. The Czechoslovakian railways post war two and three cylinder S E engine series by Mares, were of both carefully evolved external lines and highly competent internal design, combining – if given suiting quality of coal, which was rare during most of their time in regular service – high specific power output with comparatively very good cylinder efficiency.
It would be interesting to try your formulae on the 556 versus 5035 or 5280 classes to see how improved features in the former's design numerically nearly identical in leading dimensions will show up.
– 7 –
>> Secondly, these figures, .. are probably at steam rates, which whilst achievable on test may not have been called for in daily service <<
Oh my, on exacting never-relaxing Union Pacific, in fast freight services these engines were usually run flat out at anything test runs had proven them capable of – and then some if conditions were favorable. After all, there were many small adjustments made over the years and incessantly things were being optimized, all in view of improving reliability and capacity of every day revenue service – so, maximum output was very much the daily challenge of performance asked!
I bet-cha!
Edit: my usual odd words and formatting .. plus seven sentences clarified, one intro added - April 9th
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