PRR Duplexes and Experimental Engines Discussion ( S1, S2, T1 etc.)

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Posted by daveklepper on Sunday, October 28, 2018 8:28 AM

Back to PRR experimentals.  It would be interesting to compare the PRR K-5 with the contemporary NYCentral J-1 to see why the PRR never considered a Hudson.

And I think the post-WWII Reading Pacific might also well be included in the comparison.  Not the CP Post WWII Pacific, which was specifically a light-duty branchline locomotive.

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Posted by Jones1945 on Sunday, October 28, 2018 10:36 AM

daveklepper

Back to PRR experimentals.  It would be interesting to compare the PRR K-5 with the contemporary NYCentral J-1 to see why the PRR never considered a Hudson.

And I think the post-WWII Reading Pacific might also well be included in the comparison.  Not the CP Post WWII Pacific, which was specifically a light-duty branchline locomotive.

The PRR K5 #5698 had a much higher TE (54,675 lbf) than NYC J-1 or even J-3a Dreyfuss Super Hudson (41,680 lbf). Overmod mentioned the main reason of why there was not a single Hudson in PRR system. Let's review a quote of his reply: 

"PRR wouldn't buy Hudsons from Baldwin for the reason I gave earlier: they had just spent to get 475 K4s, including 200 from Baldwin, some as late as 1928 (into the real Hudson era).  By the time they were looking at better power, it was into the era of the true high-speed 4-8-4 and there was no point in considering anything but eight-drivered power -- had the divided-drive 84"-drivered locomotive worked out there would have been no need for a trivial little Hudson, and modern balancing made an 80"-drivered locomotive perfectly fast enough for what 'used' to demand an 84" wheel.  (You will note the somewhat lamentable history of 84" drivered Hudsons in practice, with C&NW notable for being unable even to reach 100mph in AAR testing, and Santa Fe getting little faster even with much more heroic proportions; no one claims comparable top-speed limitation for the S1 if they are even borderline sane.  The question was getting that fast, not sustaining it...)" (quote end)

Note there was a lot of surplus K4s during the electrification from 1928 to mid-1930s as well. Smile

Reading Class G2-sa 

 

 

 

PRR K5 4-6-2 # 5699 with Caprotti Valve Gear

NYC Class J-1e #5336

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Posted by Overmod on Sunday, October 28, 2018 11:56 AM

The G2sa is pretty, but Mr. Klepper meant this:

This from a railroad with some of the best 4-8-4s ever built, and if there were any use for a 4-6-4 over it, they'd have built it.

I was expecting someone might raise the idea that PRR did not use Hudsons because Alco was not a usual supplier.  Remember that the 'first' Hudson design wasn't Alco's, it was Baldwin's, to C.H. Bilty's spec, probably the first locomotive truly documented to run over 100mph sustained -- and a logical example for PRR to study if they had wanted a 4-6-4.

Note that almost any conceivable Hudson (or Baltic) would require a stoker.  PRR didn't even put stokers on the K5s, by intent (and it's arguable whether they would have if the Government hadn't mandated it as late as the mid-Thirties) and that in my opinion was a shortsighted waste, but I think it's a strong argument why PRR did not adopt one at the time.

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Posted by Miningman on Sunday, October 28, 2018 11:57 AM

Yeah, just a matter of timing really. Like all things in life and history, it's all about timing. 

I suppose they could have scrapped 100 or so fairly new K4's for Hudsons like later PRR management did with the T1's and Q2's for Diesels, but management at that time wasn't so reckless. 

Certainly could have used better timing here and there in my own life but the arrow points one way and one must deal with the consequences as to where you place your markers along the line. C'est la vie. 

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Posted by Jones1945 on Sunday, October 28, 2018 2:18 PM
Overmod
...This from a railroad with some of the best 4-8-4s ever built, and if there were any use for a 4-6-4 over it, they'd have built it.
 
After reading some brief history of Reading's T-1 4-8-4s, it triggered my curiosity. It amazes me that they were rebuilt from I-10a 2-8-0 and managed to archive satisfactory performance. They look decent as well.  
 
 
 
Overmod
I was expecting someone might raise the idea that PRR did not use Hudsons because Alco was not a usual supplier.  Remember that the 'first' Hudson design wasn't Alco's, it was Baldwin's, to C.H. Bilty's spec, probably the first locomotive truly documented to run over 100mph sustained -- and a logical example for PRR to study if they had wanted a 4-6-4. 

Milwaukee Road class F6 by Baldwin which served in MILW system for 24 years! An early Hudson class built in 1930 got overshadowed by the overrated F7 by Alco. The first thing caught my attention was the design of the leading truck of this class, reminds me of the trucks using on PRR T1 and C&O M-1. By the way, If PRR wanted to order Hudson in 1930s, why didn't they keep purchasing from Baldwin or build them in their own shops instead of buying them from a company which they wanted to keep their distance from it. 

 
 
 
 
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Posted by daveklepper on Monday, October 29, 2018 4:28 AM

Jones1945, your NYCentral T.E. for Hudsons is without the booster operating, I presume.  With booster, then equal to RR K-5?

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Posted by Jones1945 on Monday, October 29, 2018 7:43 AM

daveklepper

Jones1945, your NYCentral T.E. for Hudsons is without the booster operating, I presume.  With booster, then equal to RR K-5?

Thank you for the question, Dave. As you may note that the booster engine was not a device fitting the style of PRR management; when I compare K5 and NYCentral's Class J Hudsons, I used the T.E without the booster engine. If I estimate the TE of K5 with a booster engine, that would be 65000 to 70000lbf! Note Pennsy and Baldwin successfully increase their Pacific's TE from 44,460 lbf of K4 to at least 54,675 lbf of K5 #5698, even though the FA was a bit "below average". 

I wonder what kind of powerful monster we would have had if Pennsy decided to make a 4-6-4 base on a K5. CoffeeSmile

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Posted by M636C on Monday, October 29, 2018 8:01 AM

I wonder what kind of powerful monster we would have had if Pennsy decided to make a 4-6-4 based on a K5. 

If you compare an NYC J3 to an NYC L3, they look pretty much the same...

So since the M1 basically used the K5 boiler with an added combustion chamber, I'd expect Pennsylvania P6 (or would it be a P1?) to look similar to an M1, with a longer firebox and one less driving axle...

Peter

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Posted by Overmod on Monday, October 29, 2018 11:27 AM

M636C
So since the M1 basically used the K5 boiler with an added combustion chamber ...

Don't you have that kinda backward?  The M1 with internal steam pipes predates the K5, and my understanding has always been that the K5 boiler was derived from that, rather than the other way round.

Hard to believe that a boiler suitable for an eight-coupled wouldn't be sufficient for any six-coupled locomotive without going to obligatory larger fireboxes requiring stokers.  When PRR went to larger fireboxes it was for 'enlargement' of the M1 (into a design with five driving axles instead of a booster), so presumably the point of any "P6" would be to implement the moral equivalent of a fourth driving axle via a high-speed booster ... something PRR didn't make nearly the use of as the it-was-invented-here NYC. 

Meanwhile, of course, with all those K4s and then increasingly little for them to do with the high-speed electrification progressing, cheap doubleheading was FAR better use of capital than some Hudson with only enhanced starting TE and some high-speed nominal economy to recommend it. 

Meanwhile there is the parallel, and far more important, question why PRR never considered a 4-8-4 in those critical years, the logical follow-on to Pacifics so many other places.  At least part of this is timing (and in this respect PRR was spared the kind of horror it encountered with, say, the L5 electrics) in that true express Northerns weren't really 'there' until the advent of proper balancing knowledge, several years into the Thirties, but cost effective roller rods and the like not until much later (PRR having firsthand experience via N&W, so a great deal of this is circumstantial and not conservative hidebound balking at the considerable added cost) when the siren call of duplex low augment was at its height and as yet untainted by practical road experience.

 

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Posted by Overmod on Monday, October 29, 2018 11:29 AM

M636C
So since the M1 basically used the K5 boiler with an added combustion chamber ...

Don't you have that kinda backward?  The M1 with internal steam pipes predates the K5, and my understanding has always been that the K5 boiler was derived from the I1 Decapod design.

Hard to believe that a boiler suitable for an eight-coupled (let alone ten-coupled size now with deep water legs) wouldn't be sufficient for any six-coupled locomotive without going to obligatory larger fireboxes requiring stokers.  When PRR went to larger fireboxes it was for 'enlargement' of the M1 (into a design with five driving axles instead of a booster), so presumably the point of any "P6" would be to implement the moral equivalent of a fourth driving axle via a high-speed booster ... something PRR didn't make nearly the use of as the it-was-invented-here NYC. 

Meanwhile, of course, with all those K4s and then increasingly little for them to do with the high-speed electrification progressing, cheap doubleheading was FAR better use of capital than some Hudson with only enhanced starting TE and some high-speed nominal economy to recommend it. 

Meanwhile there is the parallel, and far more important, question why PRR never considered a 4-8-4 in those critical years, the logical follow-on to Pacifics so many other places.  At least part of this is timing (and in this respect PRR was spared the kind of horror it encountered with, say, the L5 electrics) in that true express Northerns weren't really 'there' until the advent of proper balancing knowledge, several years into the Thirties, but cost effective roller rods and the like not until much later (PRR having firsthand experience via N&W, so a great deal of this is circumstantial and not conservative hidebound balking at the considerable added cost) when the siren call of duplex low augment was at its height and as yet untainted by practical road experience.

 

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Posted by Jones1945 on Tuesday, October 30, 2018 2:16 AM
Overmod
Meanwhile there is the parallel, and far more important, question why PRR never considered a 4-8-4 in those critical years, the logical follow-on to Pacifics so many other places. 
 
Alvin F. Staufer, the author of "Pennsy Power" raised a "what if" question indirectly in a caption of a pic of M1a; what we could have had if Pennsy canceled their last 100 K4s (#5400 - #5499) in 1927 and 1928 and replaced them with M1 or M1a? If NYC managed to increase their Mountain’s top speed to 80mph like what they did on their Class L-2d, I believe Pennsy could have done a similar thing to their 4-8-2 as well; that would make M1s suitable for higher speed passenger services. Judging by the specs on paper and reaction of the crews, M1s was a durable and reliable Class. I won’t doubt it if someone says M1s could outperform NYCentral’s Mohawks.
 
Replace the last two orders of K4s (100 engines in total) with M1 would have helped Pennsy to eliminate the double-head K4s problem and provide enough power for longer consists before, during and after WWII. But I heard Pennsy had the 80-inches-driver fetish. (Until they tested the N&W Class J 4-8-4, which was an eyes opener for ALL of them. Note the driver’s size of S2 turbine and Q2 duplex) TE of PRR M1b was 69,700 lbf, 4,500hp (estimate), already powerful enough to haul 1200 tons consist and hit 100mph according to AAR's test data. Pennsy should have noted the usefulness of their M1s.
 
 
 
I don't and probably never would fully understand why the management of Pennsy was so insisted to "ALL-IN" the concept of duplexes when they could have easily built a very successful “Northern” (base on Pennsy's track record of building conventional steam engines) if they thought their M1b were not powerful enough; the duplex adventure of Pennsy was an unrestrained gambling. Besides all the reasons we discussed in this post, it is a reasonable doubt that there was illegal rebate offered; probably by Baldwin or Franklin to some individuals inside or outside the management of Pennsy. I think it is a reasonable doubt, but I am not trying to accuse anyone without solid evidence. 
 
Note Q1 was designed by Pennsy itself; it had nothing to do with Baldwin and Franklin (except the booster engine). It was the only alternative duplex which could handle passenger service beside Baldwin’s T1 at the time (B&O Class N-1 was still there I guess). Intended or not, it increased Pennsy’s bargaining power even though it seldom or probably never towed a passenger train.
 
 
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Posted by Jones1945 on Tuesday, October 30, 2018 10:50 PM

Porthole window which you can find on the lower front end of T1s was one of the common characteristics of Streamline Moderne. But a ship-prow-style smoke box was not common for streamlined trains. Loewy's design for the two prototypes T1 of 1942 reminds me of The McKeen Railmotor. Note in Loewy's conceptual design for T1, there were 4 portholes instead of 3. Probably a coincidence.


 

Moving it from Trains Forum for the record:

Overmod
selector
Is that report available for reading/download?

Here you go:

https://catalog.hathitrust.org/Record/001615135

A practical evaluation of railroad motive power by Kiefer, Paul Walter (1947)

 

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Posted by Overmod on Wednesday, October 31, 2018 11:11 PM

Jones1945
what we could have had if Pennsy canceled their last 100 K4s (#5400 - #5499) in 1927 and 1928 and replaced them with M1 or M1a?

The answer is likely what you get when you fill in the missing part after realizing 'cluster' is only half a word.

The practical beginning of modern balancing, Eksergian's paper, came out in 1928, and even in the mid-Thirties some people who should have known better* had not figured out what was involved.  In order for a locomotive with 72" wheel to be able to run at "full K4 speed" more would be required, and the PRR motive-power people would have been highly aware of that.  (Note that they did not recognize much of the point of Voyce Glaze's balancing even as late as the AAR testing, even with the anomalously high speed staring them in the face.)

By the point in the 1930s that the implications of good balancing, even 'retrofitted', was fully realized, PRR was on to the 'bigger and better' thing, rather pointedly avoiding the characteristics of something like a C&O T1 at the time in favor of a piece of experimental science fiction justifying its "M1-plus" cost with M1-plus available features (including a reasonable compromise between M1 and K4 wheel size combined with lower augment).

They certainly figured out about the T class, even if it had to be a learning experience partway shoved down their throats; they never did try improving the M1 even though the N&W J was legitimately in their corporate control and other railroads, UP being one that came to mind, did precisely the kind of kit-of-improvements on their 4-8-2 (suggestively numbered 7002) that PRR should have considered when the time came for state-of-the-art balancing to be applied.

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Posted by Jones1945 on Thursday, November 01, 2018 3:56 AM

Overmod

The practical beginning of modern balancing, Eksergian's paper, came out in 1928, and even in the mid-Thirties some people who should have known better* had not figured out what was involved...

...PRR should have considered when the time came for state-of-the-art balancing to be applied.

I absolutely agree. Many say Pennsy's management style was conservative and slow on the uptake, I partially agree that since they were the only one railroad "had the guts" to use a fleet of the duplex and built a direct-drive steam turbine engine in the States. But at the same time, it seems that they were very slow on updating their knowledge of various cutting-edge technologies. This caused them a lot of troubles and cost them a lot of money; from simple things like the mechanical stoker to balancing, front end throttle etc. They were not only underestimated the potential of M1; probably the only Mountain Class in the States that could fit into the "superpower" category; they also underestimate their capacity to lead the railroad industry. 

Back to 1944, upgrade the design of the M1 with all up-to-date technologies: lightweight rods, roller bearings, state-of-the-art balancing, front end throttle, Franklin poppet valves, Q1-style streamlining etc. The new M1 should be powerful and fast enough to handle the post-war passenger traffic. But I can understand that during the peak of wartime traffic, PRR's management thought there was a need to build a fleet of powerful and fast engine like T1 and Q2. 

  

Anyway ...... I still prefer the looks of Q1 to M1 Stick out tongue

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Posted by Overmod on Thursday, November 01, 2018 1:38 PM

Jones1945
I still prefer the looks of Q1 to M1

Provided, as you do, it's the version without the goofy side sheets and bullet nose. 

Similarly, I'd like the look of the Q2 much better if it didn't have that ghastly open space with nothing in it between the front running-board side panels and ... anything near them ... at so many angles it was seen in service.

Here, though, it's shown as intended...

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Posted by Jones1945 on Friday, November 02, 2018 1:41 AM

Overmod

Similarly, I'd like the look of the Q2 much better if it didn't have that ghastly open space with nothing in it between the front running-board side panels and ... anything near them ... 

This is exactly the reason why I prefer the looks of Q1 to Q2; it looked like something was missing at the front end. I am not impressed by the as-delivered version of Q1 though. I love how Pennsy removed those cumbersome plates from her and kept the streamlined "skyline", the cab and the lower front end. Those 77 inches drivers also make her looks sexier than her younger sisters. (bigger is better? Confused )

(Nice model of Q1, but the pilot wheels should have made larger)

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Posted by Overmod on Sunday, November 04, 2018 8:24 PM

Jones1945
Was it really called “the weed electric railroad”

No, in fact, it was the WEEMS Electric Railway, as covered in the contemporary trade press, as here

 http://www.catskillarchive.com/rrextra/odweems.Html

and in

patent 376567

 And I was wrong.  Testing reached the 150mph range, but actual service speed would be quicker than that.  Think mail and express from New York via Philadelphia to Chicago in less than four hours, before 1890...

I retrieved the correct information on this 'late' while looking up references to that cockamamie Hyperloop predecessor touted, during the great age of LBJ's Keynesian stimulus of ground transportation, by the inimitable WHOOSH corporation.  (It's patent 3630153, if you're curious...)

Interestingly enough, there is something I had not known about, an actual passenger interpretation of the system.  This in fact might be the thing that so inspired that unsung science-fiction author John Jacob Astor in the early pages of A Journey In Other Worlds.  Patent 406804.

 

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Posted by Jones1945 on Monday, November 05, 2018 12:11 AM

Overmod

No, in fact, it was the WEEMS Electric Railway, as covered in the contemporary trade press, as here

 http://www.catskillarchive.com/rrextra/odweems.Html

and in

patent 376567

 And I was wrong.  Testing reached the 150mph range, but actual service speed would be quicker than that.  Think mail and express from New York via Philadelphia to Chicago in less than four hours, before 1890...

Very interesting and inspiring! It was probably one of the most ambitious and forward-looking designs in the era. Note that the patent was filed when Albert Einstein was a child. 

"Imagination is more important than knowledge. For knowledge is limited, whereas imagination embraces the entire world, stimulating progress, giving birth to evolution."

 

But but but....how about the ride quality? Smile, Wink & Grin

 

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Posted by Overmod on Monday, November 05, 2018 12:59 AM

Jones1945
But but but....how about the ride quality?

You cut right to the heart of one of the probable issues with achieving high speed with these things.

Note that many of the discussions of issues with HSR will also apply to practical high speed of the magnitude these plans involve.  This is implicit in the discussions by the early 1890s that put single and double track on high trestlework when the service is established; I think it is likely that a fairly careful system of adjustment in the field would be developed with a little hard experience.

But looking at the machine that was given to the Smithsonian, you immediately note that the suspension travel and compliance are too low, and the likely weight too high, for extended high-speed running on trestlework as light as that indicated.  This also applies to both the pressure and the current transfer through the 'top contact' that was originally intended to 'hold the lower wheels on their rails' to the extent that the slight lowering of the point would not give aerodynamically -- that the three-point rail contact was essentially abandoned after just a couple of years of design and test indicates to me there were problems there that neither the Baltimore nor the New York versions of the company could solve.  Comment has already been made that the drilling of the wheels on the preserved 'locomotive' is evidence of careful dynamic wheel balancing, another indication of attempted solution problems associated with or observed with increased speed.

I provided the security picture to note that the date of issue is past the financial trouble in 1893-4 that I thought was the principal reason for 'disappearance' of implementation of this system.  I am looking to see if more has been put up on the Web and via more recent scholarship regarding the fate of this attempt, which represents a far more sensible application of very high speed service than a full-scale human-carrying system would be at that time.

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Posted by Jones1945 on Tuesday, November 06, 2018 7:01 AM

Reply by Jones1945

 

 
Overmod

...that the three-point rail contact was essentially abandoned after just a couple of years of design and test indicates to me there were problems there that neither the Baltimore nor the New York versions of the company could solve.  Comment has already been made that the drilling of the wheels on the preserved 'locomotive' is evidence of careful dynamic wheel balancing, another indication of attempted solution problems associated with or observed with increased speed.

...I provided the security picture to note that the date of issue is past the financial trouble in 1893-4 that I thought was the principal reason for 'disappearance' of implementation of this system.  I am looking to see if more has been put up on the Web and via more recent scholarship regarding the fate of this attempt, which represents a far more sensible application of very high speed service than a full-scale human-carrying system would be at that time.

 

 

I am still fascinated by these conceptual designs including Patent# 3,630,153. If it had overcome all those technical obstacles in the 1890s, It had the potential to become something that could have changed the world, as well as the definition of Trains. Besides all the technical difficulties you mentioned from previous posts, I believe it was quite a risky business since one single crack or defect on the rail within the 900 miles system could ruin the whole business by one single serious  accident; especially a passenger "container" travel constantly at such high speed (150mph+), high frequency on a daily basis.

There weren't any easy solution which wouldn't increase the operating cost. During that era, Stagecoach was still playing an important role and many horse carriages didn't have leaf springs for suspension. Instead, thread or leather strapping was used. Making the "passenger version" of Weems electric railway as comfortable as early Pullman sleepers seems impossible with the technologies available in the 1890s.  But a 4-hour schedule from NY to Chi-Town is very compelling! Yes

A birth control device in 1890sCoffeeSmile, Wink & Grin

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Posted by Jones1945 on Friday, November 09, 2018 10:15 AM

Unanswered Questions

Raymond Loewy never ever shared his thought about some of his most iconic works for railroading, S1 and T1. At least not in the books I own. Why the smoke box of T1 looked like a ship prow but not a Roman helmet, a sharp pencil, a fountain pen or a banana. Why there were three portholes but not five? Why made all portholes the same size? Did Mr. Loewy think that the de-skirted S1 looked much better than his original design?

More unanswered questions:

Did Mr. Loewy designed or involved the streamlining of the four K4s built for the South Wind and the Jeffersonian; as well as Q1. If he did, why Mr. Lowey never claimed they were his works? did he think they were not good enough?

Did he suggest alternative options when the PRR management decided to kill the F.O.M color scheme in 1947? Did PRR give him enough time and a high degree of freedom to finish his works? Did Pennsy alter his works without notice? What was his thought when Pennsy decided to dieselized all prime trains by 1948? Where did you hide your "Triplex" drawing Mr. Loewy? 

 


 

Some Franklin advertisements on Railway Age. Better posting them here than storing in my Hardrive. Laugh

 

Inevitable Fate

When folks working in Franklin were busy improving their products to max out steam engines performance, the rich and famous in the city were driving their new fancy cars traveling from city to city. 

Can't afford a new car? There were tons of second-hand cars waiting for you!

Forget it, this one is not for sale. Coffee

Meanwhile, the standard railroad of the world was using some beaten up; state-of-the-art duplex steam engine to power their prime train --- the Broadway Limited. Observe! Mr. Loewy, this is your fascinating work. 

"Daddy, can I take a photo with the new engine?"

"I am afraid not my dear son, it looks like your abused toys......"

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Posted by Jones1945 on Tuesday, November 13, 2018 2:37 AM

Moving the post here from Trains Magazines Forum for reader's convenience. 

Link of original post:

 

 "An assessment of the benefits of the application of Franklin valves on the PRR K4 and T1 classes".

http://cs.trains.com/trn/f/740/t/272776/reply.aspx

 

Dreyfusshudson

 

You folk have been very helpful to me in the past, and I’m posting this in the belief that you will have some further useful commentary. Its aim is to throw some light on the development trajectory of latter-day US steam.

 

 I was recently sent copies of the PRR test reports on the Franklin valve K4, the T1, and Q2- something of a holy grail for me finding these. There are also snippets of information on the tests of the K5, which I see as the missing link in the PRR chain.

 

The particular interest for me was whether the supposed benefits of the Franklin poppet valves were real. I have written a report on this, and what is below is a rather lengthy summary of what I discovered. The bottom line is that much of the hype about the poppet valves is unjustified. They did change performance characteristics, but, at that time, the leakage problems that had dogged such designs since they were introduced in the 19thcentury were not solved, and they provided no advance in engine efficiency. There were in addition well known mechanical issues on the T1s.

 

In addition to the test reports themselves, my additional sources are primarily a random selection of ‘Keystone’ articles, and several from Railway Mechanical Engineer, plus articles by distinguished US authors in the post-steam era... But some of you may have access to other primary sources.

 

Please do not interpret this as in any way a criticism of the T1 new build project. This is an amazing effort which deserves everyone’s full support.

 

I would be happy to forward the full report to anyone interested, though fear its primary use would be as a cure for insomnia.

 

Summary

 

·         This paper analyses plant and road test data in Altoona Bulletins on the PRR K4 and Duplex T1 classes with Franklin A poppet valves, to see what benefits the valves gave. Comparators are the original K4, a 1930s modified K4 and a Walschaerts Duplex, the Q2.

 

·         The context of this work was the belief in the late 1930s that US passenger trains of the future would need to run at 100mph, and load to 1000 US tons.

 

·         A 1930s piston valve K4 was tested on a 1000 ton test train for the AAR. It developed about 2800IHP at 75-80mph in a 40% cut off, a steam rate in the high 40000s lbs/hr. It could not reach 100mph on the relatively flat PRR main. It was noted that the steam rate achieved was some way short of the 65000lbs/hr achieved on the test plant and that this could not be achieved without use of excessively long, inefficient cut offs.

 

·         The resistance of the coaching stock was established on these tests, which showed that over 3000EDHP would be needed to move a 1000 ton train at 100mph on the level. With 2000HP for the locomotive, plus acceleration needs, this gave target cylinder power around 6000IHP.

 

·         It was believed that poppet valves were to be preferred for high speed running and would use steam more efficiently in part because more is admitted at a given cut off, allowing more economical cutoffs to be used. This also helps to deliver the enormous power required.

 

·         Lentz poppet valves, initially with oscillating and then rotary cams had been tested in the UK, with Gresley taking the lead. Oscillating cams were unsuccessful, rotary cams on the D49 showed more promise, but showed no efficiency savings, and were quickly removed from P2 2001. Leakage was the suspected problem. The D49s would likely have been rebuilt had other priorities including WW2 not intervened.

 

·         In the US, the Franklin valve company visited Lentz in London and produced their own oscillating cam version, the Franklin A valve. The Franklin Valve company fitted K4 5399 with these valves and improved steam circuit, and it was road tested in a similar fashion to the standard K4. It produced about 3400IHP and achieved speeds of 85-90mph. Later plant tests imply the steam rate was 55000+lbs/hr, much higher than the original K4, with cutoffs again approaching 40%. That is, the higher power was mostly due to the higher steam flow the poppet valves allowed, in turn allowing the boiler to be steamed harder.

 

·         The increased performance of 5399 meant it was sufficiently powerful to eliminate wasteful double heading of K4s on premier trains. So although the boiler would be operating inefficiently at the high steam rates required, it was likely overall much more economical.

 

·         Before being tested on the Altoona plant, 5399 was then fitted with a new sine wave superheater, which eliminated much of the serious pressure drop to the steam chest on earlier versions, and a much wider exhaust.

 

·         It proved possible to steam this machine at 77000lbs/hr (1100lbs steam/ sqft grate/hr). It showed marked improvements in engine efficiency over the Standard K4 at a steam rate of 70000lbs/hr, with particularly marked advantages at high speed. This was taken as a resounding endorsement of the suitability of Franklin valves for a future high-speed design and was a critical factor in the decision to fit the duplex T1 with Franklin A valves.

 

·         There was clearly a great sales push by the Franklin Valve company to recoup their development effort, but it reads like the PRR’s desire to gain a breakthrough technological lead made them more than willing partners.

 

·          However, as a number of contemporary observers had suggested, analysis of the test plant results with modern techniques says:

 

o   The increase in engine efficiency on the test plant over the Standard K4 was entirely due to higher steam chest pressure and wider exhaust, not the Franklin valves.

 

o   The higher steam flow at a given cut off allowed by the Franklin valves ought to have given a further significant improvement in efficiency by reducing the very long cutoffs needed to work at high steam rates. This does not appear, and analysis of the data says that, as with other poppet valve setups of that era, steam leakage was occurring which negated any benefit that the lower cut off gave.

 

o   The enhanced efficiency benefit of 5399 at very high speed was again not due to the poppet valves, but rather that 5399 was operating at much lower back pressure, thus lowering the over compression that occurred at high speeds on the original K4.

 

o   In any event, 70000lbs/hr is quite impracticable in service from a 69 sqft grate.

 

o   By inference, the superior performance of 5399 in road testing was almost entirely due to the fact that the greater steam flow at a given cut off given by poppet valves allowed 5399 to be steamed at higher rates than the standard K4. A similar result could have been achieved by raising the boiler pressure to 250 psi, and indeed Altoona testing of a 250psi K5 Pacific showed it had superior efficiency to all K4s tested, but changes to the boiler design on the K5 made it a temperamental beast.

 

o   It is not possible for 5399 to have averaged 100mph for 25 miles on end as claimed, nor does the time course data support this claim.

 

·         Based on the contemporary interpretation of the 5399 results, two prototypes of a futuristic high power high-speed Passenger locomotive, the T1, were built, incorporating both Franklin A valves and also a four-cylinder Duplex drive. Both features would enhance the flow of steam at a given cut off, hence increase power at that setting.  Driven in the same cut off as a K4, a T1 would produce nearly twice the power at speed.

 

·         Prototype 6110 was tested on the Altoona test plant. It proved able to meet the 6000+IHP at 100mph brief, although the boiler performance was deteriorating quickly at the high steam rates needed, with low efficiency and high levels of black smoke. Maximum service IHP would likely be have been no more than 5000-5500IHP.

 

·         The high steam rates required needed a narrow blastpipe, acknowledged to be sub-optimal.

 

·         Even at 5000-5500IHP, and with a target load now reduced to 880 US tons, a T1 could have comfortably averaged 100mph over long stretches of the PRR Crestline to Chicago main, had the necessary investments in infrastructure been made. (They never were).

 

·         At a more realistic 4000-4500IHP, major schedule improvements with plenty of 100mph running would still have been possible.

 

·         Its higher pressure, superheat and large grate meant the T1 was far more economical in coal consumption than double-headed K4s, hence a major step forward. Note however Altoona felt the need to test 6110 with reduced superheater area, reducing efficiency because superheat was ‘somewhat higher than is desirable from a maintenance perspective’.

 

·         The massively high powers achieved by 6110 were far higher than anything needed on PRR schedules of that era. The Altoona report acknowledges this in as much as it was recognized that at the very low cut offs needed in service at full boiler pressure (due to valve design and four cylinders) ‘the action of the valve was not entirely satisfactory’. For this reason, tests were done at 150-170 psi steam chest pressure to establish what was needed in practice, this negating the efficiency benefit of 300 psi boiler pressure. At these lower in service steam rates, too high superheat and back pressure would not have been problems.

 

·         As with 5399, analysis of the results says that the engine was not as efficient as it ought to have been. Using test results on the Walschaerts Q2 and K4 as a comparator, it can be shown that the Franklin valves on the T1 were also leaking to a degree which significantly reduced overall engine efficiency, negating the benefit of shorter cut off, so contrary to even recent commentary, did not provide an efficiency benefit, even at full boiler pressure. This coupled with the fact that four valves and cylinders will inevitably leak more than two means that the T1 was likely no more efficient than a PV 4-8-4 working in longer cut off, and under typical service conditions, quite possibly worse.

 

·         The combination of two radically new technologies, Duplex drive and Franklin valves led to a number of operational issues with the 50 T1s purchased on the back of the 6110 results. Development work was done to eliminate these problems, including a newly designed rotary cam Franklin B valve, but the T1s were made redundant before they were even built by the purchase of diesels, so it was all irrelevant. The leakage problem was not recognised, and whether it was a tractable one is not known, nor whether Franklin B solved this problem.

 

·         Overall, one can say that the misinterpretation of results on 5399 meant the speed and economy logic for poppet valves on the T1 was quite spurious. Further, leakage of the poppet valves, which paralleled earlier UK experience with both oscillating and rotary cam valves, had not been solved at that time.

 

·         More fundamentally, one may speculate that the creation of 5399 was a consequence of the failure of the K5, which could have matched 5399. This failure has been linked to deficiencies in its boiler design, consequent on the firmly held belief that, since greater evaporative capacity was needed the evaporative surface area of the K4 boiler had to be increased. Modern analysis says this is not so; heat transfer does not limit evaporation and power.

 

·         The British persisted with poppet valves, and a class of about 30 4-6-0s was built with valves to a modified Caprotti design in the 1950s. They worked in service for a decade without adverse comment, the right kind of compliment! A Pacific with the same set up showed good efficiency when tested. It was suggested that the modified Caprotti valves might seat better (i.e. be more steam tight) than the Lentz arrangement because their weight is not carried on the valve spindle.

 

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