Duplex Steam Locomotive / Steam discussion

[dubousquetaire]

Like all mechanical solutions inside cylinders solved some problems and created others, the size of the inboard cylinders was an issue. The Nord railroad in France tried a few unconventional solutions one on its 1911 Baltic designed by Du Bousquet which preceded Hudsons by quite a few years used one cylinder before the other to stay between the frames and yet increase the diameter on the LP cylinders both had extended piston rods for balance. Later Marc De caso designed his 3120 pacifics with a cast Cylinder block bolted to the frame in front of the HP cylinders between which was reinforced box like caisson, and which was wider than the frame; but then all it had to hold was the frontbuffer beam. This permited to make two inside cylinders whose diameter was greater than the width of the frames. All of these where De Glehn -Du bousquet type 4 cyl Compounds with divide drive.  This provided the same advantages that were saught after by the duplex design in U S practice later and could be balanced so that the engines did not tend to tear themselves appart. In america where axle loads of over Twenty tons where common this may not have been perceived as an advantage (parts could be beefed up) but in France where axle loads had a hard time to reach 20 tons per axle, this was a definite advantage. Contrarilly to what is thought usually, because of these and many other advantages of compound working these engines where economical to maintain. Considering the accessibility for maintenance one should read J.Van Riemsdjik excellent book on the history of compounds.  There remained the safety issue : One was not proud when he had to get inside the frames to work on an engine stored in a yard - if ever there was a rough shunt.  But then a main rod could easely be carried by two whereas on a two cylinder simple it was a lot heavier.

[Overmod]

Adding one more small point to feltonhill's note -- having inside cylinders restricts the permissible cylinder bore, and makes driving onto anything but the leading driver axle the same kind of interesting mechanical exercise seen in some locomotives with three- and four-cylinder drive. There's also the cost and complexity of providing a cranked axle.

There is a (preserved!) Belgian express locomotive from the 1930s which used inside cylinders, presumably for the reduction in lateral force at high speed with comparatively high piston thrust that's already been mentioned.

I'd note that, absent the use of high-pressure steam and advanced valve gear to allow very early and well-timed cutoff in smaller cylinders, the volumetric restriction imposed by gauge limitation on cylinder bore will radically restrict the size of a locomotive using inside cylinders ... and the costs of generating very high-pressure steam for this application will almost certainly outweigh any gains to be derived from the arrangement.

A potentially-interesting topic here might be the relative location of inside and outside cylinders on locomotives that use both (including where the HP and LP cylinders for compounds are sited).

[germanium]

QUOTE: Originally posted by feltonhill

IMO outside cylinders and machinery have more advantages than disadvantage, at least in US service.

Not the least of which is that they make more attractive models than inside-cylindered engines.

[feltonhill]

Inside cylinders would allow the locomotive to pass a more restrictive load gage as far as width on the lower end is concerned. Probably there some advantages having the piston forces forces within the frames. Would cut down on yawing when the pistons travel in the same direction for 1/4 of the stroke. Some may prefer the esthetics of having the machinery hidden with just the connecting rods visible. I believe the British liked this sort of approach.

On the other hand, don't even mention maintenance!!! Can you imagine trying to keep after all those moving parts stuffed between the frames?

IMO outside cylinders and machinery have more advantages than disadvantage, at least in US service.

[Murphy Siding]

I'm not really sure on my terminology here, so bear with me: A lot of British steam locomotives had "inside cylinders"(?), between the drive wheels, while the American designs had "outside cylinders"(?) to the outter side of the drive wheels. What would be the difference, and which seemed to be the better way? Thanks

[wallyworld]

Running the wheels off a locomotive trying to make up time against the schedule on a flagship run was part of the heroic romance of the rails which in reading these posts do have a common thread of the art of steam driving versus the science of the machine. That was one of the facsinating aspects of John Cosby's first person narritives. Many an engineer could use their ears alone to determine how an engine was performing. I think the steam engineers were a more important part of the equation in those times.There was no computer controls, anti-wheel slip, dynamic brakes etc. I have a great deal of repect for those men who had to crane their necks, putting their faces out in the elements in a driving rain, looking down the barrel of a boiler in bad weather at 90+ miles per hour.

[Overmod]

Odd you should mention "Second Engine No. 28" as I think I was thinking of a phrase from it when posting above about taking a relatively unknown engine all the way up to 115mph. I don't have the issue handy -- but doesn't he say something in there about taking a curve at some speed well over 90mph and 'the engine only seemed to follow the curve in short, sharp jerks" or words to that effect? I thought then, and still think now with a few different reasons, that when you got THAT kind of effect with a rigid-frame steam locomotive (presumably related to the lateral spring compliance in the leading truck?), you were just about begging to lift a flange or see some other dramatic effect ... but the author gave me the firm impression that it was the sort of thing that happened on the PRR when you needed to make time over the road... Seems 'of a piece' with the laconic reports about spring rigging that needs improvement at very high speeds,,, and taking the runninest SOAB as fast as they could get it to run...

[Anonymous]

Mr. Pausner:

Crosby's writings were some of the best that ever appeared in TRAINS. After you get finished with "Last Chance" try to find his "Second Engine #28" which, I believe, was in the May 1975 issue.

It tells the story of firing the second K4 on the Broadway out of Chicago when the T1 wasn't available. For a story, it might be better than "Last Chance".

Old Timer

[Anonymous]

Yes. I would like to read Crosby's "Last Chance" and would appreciate Trains.com posting it.

Joe Pausner

[Anonymous]

Overmod sayeth: "(I confess to being somewhat astounded that PRR would run up to 115mph in a basically uncontrolled environment on live track, with a 70" drivered locomotive!!!)"

I mentioned earlier that I had talked at length to the Mechanical Department man (Ed Payne) who was with the 610 on the PRR. He gave me a couple of quotes from the first PRR engineer to handle the 610 on the Broadway between Fort Wayne and Chicago (the engine had been put on the train at Crestline).

Payne followed the engineer as he inspected the engine at Fort Wayne; the man looked at the drivers and looked at Payne and said "this engine will never make the time on THIS railroad!"

The engineer got down off the engine to look it over after they arrived at Englewood on time; walked to the front of the engine and turned around and said to Payne "this is the runninest S-- of a B---- I was ever on in my life".

This engineer had experience on T1s, at that time. He couldn't have been talking about top speed, but acceleration and ability to cruise at a speed sufficient to keep the Broadway on time.

FWIW.

Old Timer

[Overmod]

Thanks, gentlemen.

(I confess to being somewhat astounded that PRR would run up to 115mph in a basically uncontrolled environment on live track, with a 70" drivered locomotive!!!)

I'd like to address an earlier point regarding how valuable all the 'late steam' innovations actually were. W.W.Stewart, discussing the NZR Garratts, says this (which I think basically addresses the whole general subject...)

"A large number of innovations ... were incorporated into this design, and at the time of the Garratts' arrival, a Junior Engineer (who later rose to be a District Mechanical Engineer) was instructed by Lynde [the CME responsible for the Garratt design] to work out the total of the savings that were claimed to be effected by the manufacturers of the various devices fitted. For instance, 8 per cent to 12 per cent on coal and water was claimed by the use of the exhaust steam injector. The Franklin grease-lubricated axle-boxes were reputed to run several months without lubrication. The [Nicholson] thermic syphons were supposed to save 10 to 12 per cent in fuel consumption because of increased heating surface and greater steaming capacity. It was claimed the stoker could fire coal of all classes more economically than could be done by hand, and so on and so on.

"The junior thoroughly totted up all these wonderful savings that were to be gained by the multitude of fittings, and in due course handed his report in to Lynde. After carefully reading the estimated and, of course, ridiculous result, Lynde rubbed his hands with glee and remarked, 'Good Lord, she will be puffing pound notes out of her chimney!' Alas, it was not to be."

One wonders how much of the actual benefit of many late-steam devices, similarly, was equal to the claims made by supply-company salesmen et al. ...

[Anonymous]

AFAIK, there was only one other valve gear failure on a J, and that was due to shop maintenance, as follows:

The exhaust ports of the J's power reverse were choked down so that the engineer could not make a quick movement with the reverse lever. No matter how hard you tried to pull or pu***he reverse lever, it would only move so fast (having had the privilege of moving J's reverse levers around the roundhouse, I know this from experience).

The J in question, the 600, was handling train #45 (the TENNESSEAN) and was passing through the dip at Hayter, Va., (a little less than 19 miles east of Bristol) at the speed limit of 65 MPH (according to the crew who, of course, wouldn't admit to violating the limit, but Hayter was good running ground and the speed was probably more than that by maybe a good ten to fifteen MPH). Unbenownst to the engineer, the choke in the front of the power reverse cylinder had dropped out due to not having been tightened properly at the last inspection. The engineer sought to drop the engine down a couple of notches to come out of the dip, and when he unlatched the reverse lever and applied a little pressure, she went right into the corner with him. The left eccentric couldn't take it and departed the locomotive, taking with it the turbogenerator (located on a bracket above the left drivers) and about half the running board skirt. They found the turbo 3000 feet from the point of the failure.

This is the only other VG failure I've heard of on a J, and it wasn't the engine's fault.

Old Timer

[feltonhill]

No N&W J was run on the Altoona plant. If it had, several of us on this thread would probably have heard about it. I'd have spent a lot more time and $ than I did to find what tests I have just to get my hands on that one. But, AFAIK no J at Altoona. Valve gear only failed once - on the road.

[Overmod]

OK, utter humility time here (and how appropriate, on the Lord's Day...)

ASSume I know nothing about the actual PRR testing:

1) If the valve gear failed multiple times -- once on the test plant, and once on the road, what might the dates be?

2) Was there 'pre-existing' damage from running on the test plant (to high cyclic rpm at presumably high load) that caused the observed subsequent valve-gear failure?

3) Was the SOLE cause of the valve-gear-parts failure, reported immediately above by feltonhill, the seizing of the valve in its cage (as seems likely from the crank being loosened) -- this seems to be the thing missing from the anecdotal accounts I've been hearing in the past...

4) How long was the interval (if any) between the testing on the stationary plant and the time of the (reported) road failure? What sort of feedwater treatment was in use during that interval, and what kind of care against carryover, etc. might have been used (or ignored) while the engine was in that road service?

5) I presume that the word "speed" is missing from the 'there is no doubt that excessive contributed'. If it's something else, tell me. (94mph average for 45 continuous miles is speaking for itself!)

I do not find it surprising that 'long-travel large-diameter' valves that did not have tailrod support might encounter difficulty when running with compromised lubrication. What I'd like to see is the cause of the 'yellow' color on the components, if that is known. If it's 'overheat' oxide (thinner interference layer of 'bluing') then the oxygen would have to come from somewhere, ideally NOT the steam flow. Would the steam be dissociating excessively (to hydrogen and oxygen) at these temperatures and conditions? How did the class J handle snifting?

[feltonhill]

I have some information on the PRR tests of N&W J 610 from a couple of PRR memos that were written just after the tests were concluded. Here are some exerpts from a memo from L. B. Jones to H. W. Jones (PRR CMP) on 1/6/45;

Speed - "The locomotive is euipped with a speedmeter which we did not calibrate but speeds of over 100 mph were reported. On one trip an average speed of 94 mph was maintained for 45 miles. This locomotive has valves of large diameter and long travel, giving large port openings at short cutoff. It is this feature that made these high speeds possible in spite of the fact that the diameter of driving wheels is only 70 in."

Valve failure - "On December 10th [1944], the locomotive was cut off at Fort Wayne due to failure of the valve motion when the gear connecting rod and the eccentric rod were bent, the eccentric crank loosened, and the reverse gear quadrant damaged. Cause assigned for the failure was poor lubrication but there is no doubt that excessive contributed."

610 made 24 runs total, 12 westbound and 12 eastbound. The locomotive was out of service from 12/10 to 12/18/44 to repair the valve gear.

PRR was very complimentary of the J, in contrast to some stories that they criticized the loco just because if wasn't one of theirs.

There's not much direct evidence on this series of tests ( I have only six pages, five PRR and one N&W), but there's enough to get the picture and support what Old Timer has relayed from Ed Payne.

[Overmod]

Sorry for dropping out so long -- honeydews, don'tcha know... ;-}

OT as usual makes good points here. For a variety of reasons (e-mail me if you want more grisly technical details of my opinions on this subject) you want as much VERTICAL space for radiant gas path, even folding that gas path as much as reasonably practical via arch structure. For another variety of reasons, you don't want drivers underneath your ashpan, blowdown cocks, etc. if you can avoid it.

Meanwhile, the higher you carry the boiler, the greater the stability issues with carrying a large water mass high up geometrically on a relatively narrow wheelbase...

Where you can DEFINITELY benefit from a 20' overhead height restriction is to do what the Russians did with their relatively huge overhead clearances: separate the steam circulation from the boiler proper so that very little opportunity for water carryover in the steam is possible regardless of virtually any amount of priming, etc. You'd also be able to run the convection section of the boiler entirely full of water, which allows some interesting ideas like inclining the flues and using a separate cross-drum for steam separation -- this can give you better-defined circulation patterns in the convection section to position circulator feeds for the firebox area. You can also keep the drum or over-crownsheet volume in the firebox reliably full, which eliminates much of the traditional problems related to up- and downgrades, and helps greatly with the steam separation (and therefore vertical firebox water circulation) in various sections of the radiant zones of firebox and chamber.

(Incidentally, the additional height would also facilitate packaging of many things like EGR and air-preheater ducting, enhanced economizer (via combustion gas) feedwater heating in addition to 'traditional' ACFI-style fwh, better physical devices for steam separation (e.g. cyclones) and better isolation of many of the flow-streamlined elements of the steam path 'forward' of the steam separators. Not to mention better lagging.

BTW -- returning to those J valves just a moment: How was something in the water treatment at PRR getting all the way through the steam to compromise the valve lubrication? (I presume the substance was a detergent, perhaps of a nature and in a quantity sufficient to give some 'proper' value of boiler-water alkalinity without additional 'ingredient$...?) Seems to me that the only way this could happen would be if substantial -- perhaps VERY substantial quantities of water were making it all the way through the superheaters etc. to the cylinders, but presumably the water treatment used by PRR would also be intended to reduce priming/foaming to a minimum. I do not know whether PRR or N&W personnel were actually at the controls of the locomotive during the test, and don't know if 'whoever they were' were watching for effects of water carryover, etc. at what had to be almost terrifying steam rates (and mechanical action!).

My comment about lateral deflection was not intended as a criticism of N&W design, and I apologize to all concerned if it came across that way. It is, of course, entirely possible that the valve seizure precipitated the valve-gear failure during the PRR test and the failure mode of the gear only mirrored that in the other cases I have heard reference to. The situation is that there is relatively little structural resistance in some valve gears to lateral deflecting forces, the assumption being that there will be relatively little resistance to motion posed by properly-designed valves, but under some conditions (IIRC usually related to drifting or compression braking, presumably without Okadees) on SOME locomotives, there could be very large unanticipated back pressure on the valves which put very high loads on the v.g., causing it at least occasionally to deflect (cyclically!) I had seen some discussion from what I considered plausible sources that this was the cause of the valve-gear failure that terminated the N&W test; if that is in fact wrong (and I think I'd take the word of someone who was there!) I stand corrected.

I also concur that a J could have done essentially everything NYC required of a general passenger locomotive -- I've seen reference to the idea that NYC "should" or "could" have used at least the later (e.g. L4 class) Mohawks on just about any practical service -- and even a J with a smaller boiler, etc. to fit NYC clearances would have been substantially better than a Mohawk... ;-}

No question, either, that N&W had the 'right' power for what they needed, which did involve 100mph operation but only for relatively short sprints, but also considerable periods of easily-controlled high tractive effort. I still think, though, that a version of this locomotive with properly-implemented variable-cam RC, and an adapted waffle-grate or rosepetal nozzle, would have been VERY interesting...

[Anonymous]

You'd still run into problems with a shallow firebox above drivers. One of the advantages of the trailing truck was having a deep firebox with more volume which provided better combustion. Good examples of engines in existence today are Southern's K 2-8-0s of 1903 (630 and 722) and the Ms 2-8-2 of 1911 (4501). Both have 54 Sq, Ft. grates but the deeper firebox behind the drivers of the 2-8-2 made it capable of supplying cylinders 5" bigger than those of the 2-8-0 (22" vs. 27" - as built; both the 2-8-0s were rebuilt as class Ks-1 with superheaters, lower boiler pressure and 24" cylinders - the 4501 was built with a superheater).

Look at the difference between UP 3985 and N&W's 1218. The Challenger has a grate area of 132.2 Sq. Ft. and a 106" combustion chamber to give it adequate volume to supply its 21x32-inch cylinders; flue length was an even 20 feet. The grate area approaches that of the Lima 2-6-6-6, but evidently is necessary to get the required volume.

Being able to place the firebox totally behind the drivers allowed the 1218 to use a 122 Sq. Ft. grate in conjunction with a 114" combustion chamber; flues could be 24 feet long. And this combination was completely satisfactory to supply 24x30-inch cylinders.

There were definite advantages in having the deep firebox.

Old Timer

[Kevin C. Smith]

I think the firebox grates are at or below the bottom of the boiler, so the entire boiler would ride above the drivers, rather than nestled in between to some extent. While clearances might no longer be a problem now days I think you'd have quite a difficulty with the center of gravity. Anyone that knows how to calculate that sort of thing have any ideas if/how it would balance out?

[Anonymous]

Well, here's another slight deviation from the discussion, but the mention of the "double" Belpaire boiler in a few posts (which needed a three axle trailing truck) and the height restrictions of the Niagra and the J's of 15'+, all brings a new question to mind:

With today's 20' max height on most mainlines, could it have been concievable for a large firebox design such as the Belpair to ride ontop of a second set of driving wheels? E.g. getting the necessary steam quality/quantity necessary for superpower steam, while at the same time keeping most of the locomotive's weight on the drivers. I know this is getting to be an abstract beyond most of your interests, but bear with me for a moment.

Take the J with the 70" drivers. That's a tad under 6 feet, and we'll assume it as the minimum for speed/drawbar pull optimization. For a 20' clearance, that leaves 14 vertical feet in which to place a large firebox, so let's settle for a max height of 19 feet and 13 vertical feet of firebox to be safe.

1. Is 13' of vertical rise sufficient space to place a large enough firebox to produce the desired steaming quality that superpower loco's demanded?
2. Given that a high riding firebox would negatively alter the loco's center of gravity, what more would be needed to keep the COG in an optimum range?
3. Other than for firebox support, did superpower steamers need to have a trailing truck for stability, etc.?

If there is room for affirmation to some degree of those three questions, then why not a duplex 4-6-6-0 with the same length of frame as the J's or the Pennsy T1?

[germanium]

Wallyworld -
http://www.5at.co.uk/5ATupdates.shtml shows the latest position. Also contains a link to the engineering specification - no mention of computers to control subsystems.

[feltonhill]

Check this link

http://www.5at.co.uk/5AToutline.shtml

for the latest proposal for new technology steam. Incorporates some of the features discussed on this thread but not all. David Wardale, author of the Red Devil... is involved. Status of project unknown, last update to site was a year ago.

[wallyworld]

This question is directed to feltonhill.This is abit off topic. All of the engines mentioned existed prior to the advent of computer control to coordinate subsystems in an engine. I noticed a common thread in your posts as well as in my reading elsewhere, that optimum operator control of an engine fell in almost direct proportion to the increased complexity of the engine. Through my reading of The Red Devil I am aware of Porta's continuing improvement to combustion and other areas for steam long after they were considered extinct. Outside of the ill fated Ace engine(which those familiar with the book
know that Porta considered too ambitious), has anyone proposed a reciprocating steam engine with all these above mentioned improvements as Porta would have preferred? It's hard to imagine no one has pursued this as the current oil crisis appears to be worsening. Maybe there is but I am unaware of any.

[feltonhill]

The B&O 4-4-4-4 was mentioned early in this thread by Old Timer. It was an experimental design, class N-1, four opposed cylinders (two under the smokebox facing forward, two under the firebox facing backwards), 18" bore x 26" stroke, 76" drivers 350 psi watertube firebox. It was built by B&O in 1937 (see B&O Power by Lawrence W. Sagle, published 1964 at pg 289-290) and scrapped in 1950.

[feltonhill]

Overmod, were you referring to the article and painting of a MILW F7 throwing a main rod? I believe it was in Trains or Classic Trains not too long ago.

From what I know, NYC was very restrictive about speeds except on tests. They used a device called the Locomotive Valve Pilot, and IIRC there was a speed recorder incorporated in this system. Most NYC locos were designed to cruise at 80-85 maximum on virtually level track (except for Albany Hill).

Some iconoclasts have argued that the Niagara was too big for Central's operations because they spent a large amount of time at part throttle. They were powerful enough that at full throttle and 80 mph, they couldn't be run at sufficiently short cutoff to maintain that speed. They contend that the Niagara didn't need to be as large as it was for Central's operations. The Niagara posted low operating costs and high mileages as it was designed (so did the N&W J) so the argument is more academic that anything else.

Although the N&W J may have been able to do anything required on NYC, it would not fit Central's load gage or weight restrictions. Maximum dimensions allowed by the load gage were 15'-3" high, 10'-8" wide. Locomotive diagrams indicate that the Niagara carried 68,750 lbs per driving axle, the highest of any NYC locomotive, so that may have been near the upper limit allowed. The Niagara was 15'-1 3/4' high, 10'-7" wide over both the cylinders and running boards and carried 68,750 lbs. on each driving axle. The J was 16' high, 11' wide over the cylinders, 11'-2" over the running boards and carried 72,000 lbs on each driving axle. So it would have take a considerable amount of "scrunching" to get the J shoehorned into NYC's clearances.

On the other hand, no 4-8-4 could do as well as the J on its home turf. It was an uncompromised design directly aimed at N&W operations. Trying to compare a 4-8-4 that actually registered drawbar pull readings (not TE, not a typo) around 80,000 lbs under 8 mph (Chart 1, readings taken from 1945 tests, highest three data points, 81,500, 78,800, and 78,000 lbs) with a locomotive that develops 62,500 to 61,000 lbs drawbar pull in the same speed range (from graph in test report of 6023) is not equitable.

See what I meant earlier? Trying to compare the J and Niagara is very difficult!!

[wallyworld]

This is a fascinating discussion and I have an appreciation of the amount of thought that have gone into these comparitive discussions on late steam design. The PRR, N&W and C&O are well known for their innovations and philosophies in design but recently I saw a photograph (which I cannot relocate) of surprisingly, a B&O engine that had (from what I recall) a duplex drive. Anyone know anything about this engine?

[Anonymous]

Quoth Overmod: "Opinion, likewise: the 'weak point' of the N&W J at high speed was lateral deflection of parts of the valve gear at high rpm, often encountered as a problem with 'conventional' piston-valve drives."

Where did that opinion come from?

The highest rotational speed credited to the J was undoubtedly the 115 MPH the 610 attained during tests on the PRR. This was just prior to the failure of the engine caused by the left valve freezing in its cage due to lubrication breakdown. If there was, as you opine, lateral deflection of the valve gear, it wasn't sufficient to cause problems at any RPM.

When I worked at Shaffers Crossing 1959-1961 there was a Night Roundhouse Foreman there named Ed Payne. Payne had been on hand with the 610 during its tests on the PRR, and described the engine failure to me. He said that when the engine was brought back to Roanoke Shop and the valve heads removed, the valves and cages were discolored (yellow) and the conclusion was that something in the PRR's water treatment cut the lubrication of the valves.

Bear in mind that the Js operated at 100 MPH every day (with, say, an inch or so of tire wear, that's 500+ RPM), but for relatively short distances. It was never necessary for the engine to be faster than it was; with the schedules and the territory on the N&W, speeds faster than that, sustained for long periods of time, were not necessary.

But the 70" wheel produced a horsepower curve ideal for the N&W's topography and heavy passenger trains. The engine was capable of running track speed (curvature limits) UP any of N&W's mountains with any of the normal train consists. It was necessary for the J to start and accelerate these trains in difficult situations, on curves and grades, in all kinds of rail conditions - Northfork eastbound, on Elkhorn Mountain; Marion, Va. on the Bristol Line, Ada, W. Va., etc. There were sharp curves on Bluefield Mountain (Jug Neck) and Elkhorn (Bottom Creek Curve at Landgraff) where the J would have to accelerate its train back to track speed after a 25 MPH slowdown. The engine was never found wanting.

I don't know enough about the Niagara and NYC's use of them to know what sustained speeds were expected of them. Did they operate at 100 MPH for miles on end?

If such speeds were not expected of them, if NYC's 80 MPH limit was strictly enforced (or even with a 5 MPH tolerance), then one can ask the following questions: 1) Could the J have done everything expected of the Niagara on the NYC with NYC's traffic and topography? 2) Could the Niagara have done everything expected of the J on the N&W with N&W's traffic and topography?

My feeling is that the answer to #1 is yes, and the answer to #2 is no.

In other words, the J's 70" drivers would not be as much of a liability on the NYC as would the 79" drivers of the Niagara on the N&W.

Old Timer

[Murphy Siding]

Overmod & Felton Hill, you point out some of the *issues* inherent in some of the later steam designs. Could you elaborate on some of the *cause & effect* of some of these design problems? For example, how would " lateral deflection of parts of the valve gear at high rpm's " affect performance & maintenance of a locomotive? Thanks

[germanium]

Overmod, Felton Hill - thanks for those informed answers and comments, and the effort obviously put in. I found them most revealing and of great interest, as I'm sure others will.

[feltonhill]

The referenced article the Central Headlight puts it this way:

"There was a choke in the live steam passages to the poppets. This minimum cross sectional area was only 52% of the minimum area of a 6000."

It goes on to reference two drawings of the cylinder saddle casting. It further references the location of the choke to the poppet inlet valves on page 35. You can guess which page I'm missing. Time to e-mail NYCSHS and see if I can round up the missing page (s).

The choke point may have been an aw-bleep on Franklin's part ,or GSC's part, or NYC's part. The article also mentions that 5500 couldn't be run out of steam but it just wouldn't burn the coal when pushed, so there must have been a restriction somewhere.

The fuel savings were about 16% according to the article. My earlier comments were not intended to belittle this percentage, but it was not significant enough when faced with the operating cost reduction of a pair or trio of then-available EMD E7's. I changed the earlier post to reflect this recorded figure.