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The Most Suitable (non-mallet) Compound for U.S. Use

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Posted by Sara T on Tuesday, March 23, 2021 10:11 PM

Overmod. >>Not dead, but sleeping.  The dwarves dressed her up at the end and she sleeps in her glass coffin waiting to be brought back to life when the right prince takes the initiative<<

Nicely written.  Sleeping - (smile), no, dead. We all faded away on the outmost track in the yard at Hamm in the winter of '58.  I know you wrote 'sleeping' because you believe some congregation could bring her back to running order. But if that would happen so on a subtle level would a new soul come settle in her, these subtle things are difficult to explain, and I don't want to go deeper into it, see pm. In short this is why one loco that had been a reliable performer in regular work times, could be a lazy performer no matter how scrutinazingly checked or a vicious one in newly re-built time, like I heard of the re-built 03  2295 is (or was).     

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Posted by Overmod on Tuesday, March 23, 2021 11:39 AM

Sara T
Oh, yes, you are correct, Sina (002)! I didn't feel it because she sits in a house dead.

Not dead, but sleeping.  The dwarves dressed her up at the end and she sleeps in her glass coffin waiting to be brought back to life when the right prince takes the initiative.  As I said on another forum, the most appropriate music that should be played at the restoration to operation should be the end of the Firebird Suite, when the world wakes up from frozen horror and the steel casts off its chains and starts to dance...

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Posted by Flintlock76 on Tuesday, March 23, 2021 11:07 AM

AND there's the 2-6-6-2 the Western Maryland Scenic purchased from the B&O Museum!  To use an old cowboy saying she was "Rode hard and put away wet!"

Another one that toward the end of it's service life just got enough TLC until it's diesel replacement was on the property. 

I can't help but think that if the WMS knew what they were getting into they'd have told the museum "No thanks!"

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Posted by Overmod on Tuesday, March 23, 2021 9:39 AM

Flintlock76
just do enough maintenance on the steamer to keep it alive until the diesel replacement showed up, and maybe not even enough!

There was more.  One relatively unremarked thing about modern steam was that parts of it could deteriorate with horrifying speed if poorly maintained.  I was told that on Q2s in storage, the alloy boiler steel could rust through nearly the full plate thickness in about a year -- granted that might have been accelerated by industrial pollution where the engines were stored, but it is indicative.

The A-2-A Berkshires were stored upon retirement from active service on the P&LE (this being one service where diesel-electrics were indeed much better suited, that being recognized almost as the engines were being built).  NYC had enough respect for Kiefer and the design to transfer the locomotives to NYC System use around Indianapolis, where they would have been useful ... except that in the comparatively short time they had been stored, they were ruined beyond economic repair as far as reliable service was concerned.  (See the Polarowitz book on the locomotives for details.)  Much of their 'street cred' as unwanted dogs with a bad name apparently stems, more or less directly, from this problem.

Kelly at Strasburg called their initial ultrasonic NDT tester 'the death ray' because of how its use revealed so many serious defects that had gone blissfully unrealized.  Steam can be intolerant of negligence, tireless in finding weak points in structure, and deadly without warning.  It is not some buggy whip or telegraph technology from the obsolescent past for cosplayers to have fun with. But that may not be evident until a Gettysburg or a Mentor.

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Posted by Flintlock76 on Tuesday, March 23, 2021 9:07 AM

Juni, that sounds a lot like what happened here in the US in a number of places, that is, just do enough maintanance on the steamer to keep it alive until the diesel replacement showed up, and maybe not even enough!

I'd think the motivation level of the steam shop guys wasn't too high either knowing their jobs were coming to an end.

 

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Posted by Juniatha on Tuesday, March 23, 2021 12:41 AM

Sara,

back in the first years after the 150 years celebration the steam shed in the regular depot at Nürnberg (not Nooriambeerge or the like, guys) was nice: the steam engines I saw at the age of ten were bright and clean and this made my picture of what the engines should look like; when I later saw S8 films of how they were at the end of regular steam times it was almost a shock to me: so run down, generally needing and all covered in soot and dirt, leaky, oily and rusty all at the same time, with dents and primitive makeshift repairs, even front number plates leaning, not horizontal - and the crews that worked on them like fresh from the garbage collection and chimney service, not even the faces were clean! Also, if you listened to a 44 class three cylinder engine start out with a freight and all you heard was whoom-fffham-thhh-wo-wowoo ... and with steam coming from you don't believe everywhere. Or the 012 Pacifics from Hamburg on the Westerland line: some with a leftside 'spinnaker' of steam as big as the exhaust above the chimney (from steam pipe forking left outside / inside cylinder) ... it was sickening sometimes, I got up and left to go out!

=J=

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Posted by Sara T on Tuesday, March 2, 2021 8:15 AM

>>Well, one of your sisters didn't, and the shop forces at Nuremberg worked carefully to put her back as intended... <<

 

Oh, yes, you are correct, Sina (002)! I didn't feel it because she sits in a house dead.  But I should of course have known from the museum. Sabine (001) was scrapped. Believe it or not I haven't been in the DB Museum at Nürnberg. Nor have I been at the steam shed they had or have (?) in Nürnberg. It does not interest me, it is all dead and cold.

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Posted by Flintlock76 on Monday, March 1, 2021 3:23 PM

Overmod
 After the criminal liability of scrapping PRR 6100 I think this ranked second...

To say nothing of the PRR's scrapping of the S1 and ALL the T1's.

I mean really, the over-the-top Art Deco styling should have saved the S1 at least!

Well you know what they say:

"Don't cry because it's over, smile because it happened!"

https://www.youtube.com/watch?v=f-0-Ex6LH2g  

 

 

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Posted by Overmod on Monday, March 1, 2021 11:15 AM

Sara T
Noone came, none was rescued, we all went to the torch.

Well, one of your sisters didn't, and the shop forces at Nuremberg worked carefully to put her back as intended... 

I DO still think some version of the cab-forward firing could have been made to work.  Whether that would be compatible with highest-speed running... I will not say.

Personally I'm still aghast Nelson Blount, who thought enough to preserve a runnable Schools-class 4-4-0, didn't save one of the 05s.  Scrapping them was (and is) like scrapping GG1s... better not imagined if you can avoid it!

One of the great collective American crimes was letting the Roosen motor locomotive we 'stole' be expediently scrapped for the Korean War.  Yes, I know we tried to send it back and nobody wanted it; I know there was never enough expressed interest in it here... but that was an important experiment in locomotive history, one difficult and perhaps impossible to re-create effectively today.  After the criminal liability of scrapping PRR 6100 I think this ranked second...

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Posted by Sara T on Monday, March 1, 2021 9:56 AM

Overmod,

I, 05003, was never involved in these hasty runs. Before WWII I was in a ... I was .. hm .. you know .. not quite disposed, so to say.

In 1945 when I was at last put right, the times were horrifying and I did only run some 500 km then was shelved aside around Hamburg.

Then a British railway officer discovered me and ordered me to be put in running order. Then followed my best time - but circumstances were not for me. It only lasted two years and I was shelved aside again. 

Then came the Bundesbahn years, all three of us were overhauled at Maffei in Munich, but our boiler pressure was lowered to the usual 16 kp/cm² - much too low for us with the small cylinders! We were weakened, it hurt! That again only lasted a few years and DB lost interest and we were shelved for final this time. 

Noone came, none was rescued, we all went to the torch.

That was our rather dismal life.

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Posted by Overmod on Friday, February 26, 2021 7:09 AM

Juniatha
With the 05 no proper frequency phenomenon was to my knowledge experienced. if I estimate lower proper frequencies of the 05 relative to that of the shorter 01-10 as around 260 rpm, then the upper one would be around 520 rpm - relative to 225 km/h and thus still out of the way at 200 - 215 .. 217 km/h.

Students at the University of Stuttgart did a SIMPACK simulation of the class 05 (discussed in SIMPACK News in June 2009) that supports this.  They found the onset of 'hunting instability' did not occur below 260km/h (and the kinematic oscillation was interesting at that speed, reaching a resonant peak at around 8s but becoming self-limiting at slightly reduced amplitude -- I am looking for a version of the graph I can reference here).

Interestingly, they identified a running instability in the tender around 225km/h, but reasoned (correctly, I think) that its coupling to the locomotive would keep any effect suppressed below 260km/h when the other effect developed.

 

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Posted by Juniatha on Friday, February 26, 2021 12:11 AM

Ehr-hm, hi!


One more word on the three-cylinder engine:
I am no supporter of that engine when arranged as a compound. As a three-cylinder simple with 3 x 120° it alright and has its place and purpose. Still, that engine is not without some critical points in itself that have hardly been taken care of in regular steam times - for one: although the cylinders are significantly smaller than those of a comparable two-cylinder engine, frame demands are not easier but just different, loads are hardly diminished - why? because of the degree of cranking which provides a more counteracting work of the cylinders and since the frames are between the outside cylinders contortion of the frames is an important thing to take care of and look at from different angles. In that direction also go aspects of counterbalancing and cross balancing.

Side remark: I do not think this 'Eastern European' evaluation on the 05 was correct. Mind that A Wolff was one of the few engineers who took care looking into those matters, also the 05 were such 'long legged', if I may say so, engines that a typical proper frequency must if anything have been at lower, not higher rpm than with the smaller 01-10 / 03-10 three-cylinder engines of the same type of engine layout. For the 01-10, I know they had a peak of proper frequencies (a locomotive is not ideally stiff and therefore develops more than just one proper frequency) around 105 (worn engine) - 110 km/h - that relates to 279 - 292 rpm - way lower than the 05 ran at 200 km/h: 462 rpm. The smaller cylinders in the larger engine also contributed to keeping proper frequency at a rather low level. Indirect prove of this thesis came with the 18 201 that had larger cylinders than even the 01-10: 520 x 660 vs 500 x 660 mm. What made the situation worse was that the frames were lighter than those of both the 05 and the 01-10 since they stemmed from the original 61 002 a 4-6-6 three-cylinder tank engine of 390 x 660 mm cylinders. The rebuilt Pacific did develop a phenomenon of proper frequencies around 182 km/h that grew scary and demanded the cutting of the high-speed test. With the 05 no proper frequency phenomenon was to my knowledge experienced. If I estimate lower proper frequencies of the 05 relative to that of the shorter 01-10 as around 260 rpm, then the upper one would be around 520 rpm - relating to 225 km/h and thus still out of the way at 200 - 215 .. 217 km/h. From that point of view, the 05 had plenty of margin to surpass 200 km/h significantly.

I believe the point was as always with DR: you want to reach goals - but you never surpass them excessively. The goal originally was 150 km/h, quickly raised to 160 km/h the speed of the 'Flying' series railcars, finally raised to 175 km/h where it stayed. That speed had been fixed during the stage of collecting builder's proposals, long before the 'down fall' run of Mallard till hard against fatal destruction of the inner drive. No joke: destruction was already in progress: that was a typical British 'Sir Francis Drake' effort, or say it with Shakespear: it was to be or not to be! The Germans would be hard pressed to agree to such a risky all-out action. Also, mind that the reichsverkehrs-minister Julius Dorpmüller had accompanied the test run in the measuring car and his protection was above any wishes to allow a little 'piercing the unknown'. Still, the amount of 3400 ihp noted for 05 002 at the record run was way out of capacity for Mallard, whatever hard-driven, and given the importance of wind resistance at that speed range, this alone clearly indicates the 05 as the faster engine in the end.

Final recognition of what would happen in an all-out effort and what speed could be attained we could only learn if we took the engine out of the museum, undertake a complete revision, possibly equip her with DB given oil firing and have a go on modern high-speed track. As enlightening it would be, needless to mention this is as sure never to happen! Rests my remark that Mallard would not have come anywhere near to the 200 km/h mark without the help of the negative incline, not to mention slower acceleration might have caused unsustainable conditions to have developed already while at slower speeds than attainable by power output reached.

And now I haven't even mentioned the crocked curve of tractive effort development in a compound three-cylindder engine - and that applies to both the 3 x 120° and the 90 / 135° variation, only at differing work points.

Now, that could create extra and higher value proper frequencies!

Look at it from any viewpoint: the best of the compounds remains the four-cylinder type and in that the one with LP cylinders inside.

Juniatha

 

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Posted by Overmod on Friday, January 15, 2021 11:06 PM

M636C
It is possible that the track in question was particularly well aligned and the temperature range was conducive to optimum performance.

It is also possible that the Eastern European analysis was wrong about the critical speed or the prospective intensity of the resonance in question.  My real concern is only that the power involved in critical resonance at the speeds in question is dramatically greater as you get into this high speed range, and the consequences less easy to 'damp out' by closing the throttle, or centering the reverse, or applying the brakes in time to avoid difficulties.

There are a number of accounts where engineers encounter severe 'rough riding' in a particular speed range -- ISTR the 6000-series Garratts have one around 50-55mph, might be give or take a few mph, and engineers learn to 'ride it out' if going faster and then 'ride it down' to get out of the critical range.  At much higher force or rapidly-amplifying resonance, riding it out might not be possible or prudent to engage in.

I have little question that the 05 design was capable of well over 125mph but I continue to find it strange that no attempt to reach even Gresley's acknowledged top speed was at least undertaken.  Perhaps the contemporary 'rail emphasis' was indeed on Diesels, and the magic 'double metric ton' was enough to establish credentials for steam.

It is my opinion that the documented complaints of 'hard riding at 135mph' for T1s, if genuine, are the result of a resonant effect.  This is one of the specific things that the multiphysics modeling (and perhaps later testing) of replica 5550 is intended to develop.

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Posted by M636C on Friday, January 15, 2021 4:14 PM

The critical high-speed consideration, in my opinion, is emergence of resonance at critical frequencies, which is a far more significant concern than 'how fast the steam can run the engine' or other relatively naive consideration.  I found it particularly interesting that an Eastern European design team identified one such likely harmonic in the class 05 design at right around the equivalent of 122.5mph, without noting that this might have been an emergent reason no German run to 'outdo Mallard' was undertaken. (Overmod)

I'm not sure how significant this is, but an interview with a crew member on 05 002 on the day of the record run included the remark that, unlike previous runs, "everything was was working perfectly" and the locomotive was running more smoothly than usual, and this continued as the speed increased. As everything was going so well, they just let the speed increase until they passed 200km/h and then shut off, slowed down and stopped to do a running check.

It is possible that the track in question was particularly well aligned and the temperature range was conducive to optimum perforformance.

Peter

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Posted by M636C on Friday, January 15, 2021 4:00 PM

Paul Milenkovic

Bill Withhun's recent postumously published book suggests that the problem with Baldwin 60000 was the watertube firebox.  Withhun himself counted many more washout plugs than a conventional locomotive, suggesting that even the mandated-to-be-at-least monthly washout and scale removal would be costly in labor hours.

 

As well as the figures noted in my post above Brasher quotes:

The equivalent evaporation pounds of water per pound of coal for the boiler was 7.9% less and for the boiler and superheater 10.5% less for locomotive 60 000 than for locomotives of the 3800 class.

This suggests that the water tube firebox is significantly inferior to a conventional staybolted firebox (which is not unexpected) but indicates the relative efficiency of the compound cylinders was even better than was observed from the test results given the poorer performance of the firebox.

Peter

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Posted by Overmod on Friday, January 15, 2021 10:23 AM

Paul Milenkovic
I suppose the reason for the 90-deg 135-deg arrangement of a 3-cylinder compound is that it works better than the more even-torque 120-deg spacing when the HP and LP are not perfectly balanced?

Think of the steam flow, too.

I had always thought the reason for the 90-degree quartering of the outside mains was to give the best 'continuous' thrust on the outer pair... as with conventional 2-cylinder DA.  The HP 'four pulses per revolution' is phased to fill in the 'low spots' in the resulting torque curve... 

As far as I've modeled it, a similar phasing arrangement ought to work if IP injection is in use to 'normalize' all three cylinder contributions.  Remember that unless you have a Leader-style engine, a typical three-cylinder locomotive is NOT augment-balanced; the outer cranks are only at 240 degrees to each other -- not as in a Swiss drive where the 120-degree throws are inherently balanced.  This is complicated, again in a way I haven't bothered to calculate, so I don't know how slightly, if the center cylinder is angled to clear the forward driver axle and the crank throw and counterweights are slightly rotated to keep the effective phasing at 120 degrees.

I've always been a proponent of balanced four-cylinder drive, even if it does mean smaller cylinders.  Note how many of the balanced compounds put the four cylinders 'abreast' as Juniatha indicated, even when the leading driver axle has to be 'cranked' for inside-main clearance.  The problem there is that it becomes complicated to provide and maintain roller bearings (of '30s construction and tribology) in a cranked axle of appropriate geometry and strength.

The use of proper Deem conjugation on a more-or-less conventional duplex (with the engines each quartered with zero overbalance, and the two engines detent-phased at 135 degrees) still represents an attractive proposition.  It is not as easy to implement Voyce Glaze's balancing (although there is less piston thrust in the vertical plane to compensate, there is less potential to shift overbalance to the other drivers -- which is another reason to use zero overbalance) but the fixed phasing provides a better torque curve at very short cutoff -- an important issue even on a conjugated duplex -- and active predictive suspension can do a better job of controlling both vertical travel and effective momentum damping (in addition to magnetorheological damping).

The critical high-speed consideration, in my opinion, is emergence of resonance at critical frequencies, which is a far more significant concern than 'how fast the steam can run the engine' or other relatively naive consideration.  I found it particularly interesting that an Eastern European design team identified one such likely harmonic in the class 05 design at right around the equivalent of 122.5mph, without noting that this might have been an emergent reason no German run to 'outdo Mallard' was undertaken. 

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Posted by Paul Milenkovic on Friday, January 15, 2021 9:45 AM

I just "hit" me.

I suppose the reason for the 90-deg 135-deg arrangement of a 3-cylinder compound is that it works better than the more even-torque 120-deg spacing when the HP and LP are not perfectly balanced?

If GM "killed the electric car", what am I doing standing next to an EV-1, a half a block from the WSOR tracks?
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Posted by Paul Milenkovic on Friday, January 15, 2021 9:34 AM

Bill Withhun's recent postumously published book suggests that the problem with Baldwin 60000 was the watertube firebox.  Withhun himself counted many more washout plugs than a conventional locomotive, suggesting that even the mandated-to-be-at-least monthly washout and scale removal would be costly in labor hours.

If GM "killed the electric car", what am I doing standing next to an EV-1, a half a block from the WSOR tracks?
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Posted by Overmod on Thursday, January 14, 2021 10:17 PM

Overmod
Since Juniatha is back -- she mentioned to me that the LP arrangement on 160 A1 was actually a 5-cylinder compound with the final LP stage divided into 2 cylinders primarily for clearance and packaging reasons.

Something got worse than babbly-babbled in that sentence.  But she subsequently explained how the thing is actually constructed, so there is no lasting harm.

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Posted by M636C on Thursday, January 14, 2021 9:44 PM
I believe Baldwin 60000 was a Smith compound, at a higher HP pressure facilitated by the watertube firebox.  It is my naive observation that several approaches to the idea were tried with various expansion ratios from about 2.3 to 2.7 -- the basic 1:2 with all cylinders equal apparently "leaving some money on the table" with respect to using the expansive energy fully. (Overmod)
 
I agree that 60000 is a Smith Compound, but I was thinking of locomotives more contemporary with the Midland Compounds or Smith's own single conversion.
In his Steam Locomotives of the Reading, Wiswesser provides rather confusing details of the class P6 Camelback Atlantics. He first indicates that the four units, 300 to 303, built by the P&R in 1909 to 1911 were three cylinder compounds with cranks set at 120 degrees. However, it seems that they had second thoughts during the build, and 301 and 302 were completed as two cylinder simples, all four using saturated steam,
300 had three cylinders 19"x24" and 303 had three at 18.5"x24" while the two simples had 22"x26" cylinders. The compounds were converted to simple by 1918 and all four were superheated in 1924.
Apparently there was one 3 cylinder simple, class P5 number 344 with three cylinders 19"x24", so the same as the compound 300. It had piston vavles driven by Walschearts gear (outside) and Joy gear (inside). It too became a two cylinder in 1917.
O.S, Nock indicates that Smith Compounds had the low pressure cylinders 90 dehrees apart with the high pressure at 135 degrees to the other two. Was this the case with 60 000?
But the topic of the thread concerns the use of compounds in the USA.
It should be remembered that in France, coal was relatively expensive and crews were rewardedby additional payment for saving fuel. They were also paid additional amounts for making up lost time.
In this environment, the forces that directed Chapelon's work can be seen more clearly. His locomotives were built for economy, but with the ability to provide additional power when required to make up time, even if being "thrashed" by other standards. 
In the USA, fuel and water economy were not taken as seriously.
Baldwin 60 000 was tested by the ATSF in normal service against four of their standard 3800 series 2-10-2s in March and April 1927, outlined in Santa Fe Locomotive Development by Brasher..
60 000 did the work in 11.5% less time than the 3800
60 000 hauled, on average 3.5% greater loads.
60 000 used, on average 24.5% less coal per 1000 ton miles.
60 000 used on average 27% less water per 1000 ton miles.
In France, that would have assured 60 000 of a rosy future. In the USA, this was regarded much less important than the penalty imposed by the more complex mechanism.
 
In these condtions, 160A1 would not have even been tested...
 
There were two inside HP cylinders, working on 90 ° set cranks of #4 coupled axle, then there were four LP cylinders which were altogether arranged as a three cylinder machine: two outside cyls at 120 °, then two smaller inside LP cyls at 180 ° to each other and 120 ° to the outside LP cyls. The two inside LP cyls were together giving the same piston thrust as one outside LP cyl.-(Juniatha)

I recommend checking out Chapelon's own drawings of 160A1 in Capenter's translation of La Locomotive a Vapeur .  For a start, there are only 12 fire tubes in the boiler, the remainder being flues with Houlet elements in the approximately one third of the flues devoted to high pressure steam, and conventional Schmidt elements in the two thirds of the flues devoted to intermediate pressure steam. This of course requires three separate superheater headers, the high pressure at the top in the usual place, and one further each side for the intermediate steam. The smokebox is forced into a triangular shape, visible in side on photos just behind the smoke deflectors.

As Juniatha has indicated, the inside low pressure cylinders are at 180 degrees to eachother and 120 degrees from the outside low pressure cylinders. This allows the two inside cylinders to provide an even turning moment with the two outside LP cylinders.

However, this is similar to the Gresley arrangement of three simple cylinders and requires a conjugating gear to derive the action of the inside poppet valves from the outside Walchearts gear driving the outside LP poppet valves. Fortunately, the Henschel design was used rather than Gresley's.

Of course the locomotive is driven on the second, third and fourth axles with two sets of Walschearts gear driven by separate return cranks on the third axle.

What could possibly go wrong?

Peter

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Posted by SD70Dude on Thursday, January 14, 2021 1:42 AM

Great to have you back, I'm really enjoying reading this thread, keep it up!

Greetings from Alberta

-an Articulate Malcontent

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Posted by Juniatha on Wednesday, January 13, 2021 10:03 PM

To Quote Overmod:

"Since Juniatha is back -- she mentioned to me that the LP arrangement on 160 A1 was actually a 5-cylinder compound with the final LP stage divided into 2 cylinders primarily for clearance and packaging reasons."

Something got overly babbly-babbled here (no insult intended).

I didn't say (write) that.

There were two inside HP cylinders, working on 90 ° set cranks of #4 coupled axle, then there were four LP cylinders which were altogether arranged as a three cylinder machine: two outside cyls at 120 °, then two smaller inside LP cyls at 180 ° to each other and 120 ° to the outside LP cyls. The two inside LP cyls were together giving the same piston thrust as one outside LP cyl.

I had myself also experimented - in theory - with divided inside cyls on what was otherwise a three cyl simple - just to balance the inner drive. However, while this brings about a very balanced inner drive it leaves the outside drives now even less balanced. My idea back then was to balance out the outer drives each individually rather than seek an overall self-balaning in an engine where the outer cranks are some 80 ins apart - thus inevitably a major degree of self-balaning would only result in a twisting motion of the overall engine - non desired by me. What stayed was the less sturdy coupled axle with those counteracting cranks, making a long centre interconnecting lever. If used in a common axle drive, the outer cylinder will subject this axle to distortions by mass forces at speed - undesireable! If used as a first coupled axle drive the lesser stiff axe against a single throw axle in a three cyl engine is also less than desireable with flange / rail contact lateral forces.

Thus in the end I dismissed the type and threw away the double throw design.

On the 160.A.1 it would have been difficult to arrange the LP cyls like a four cyl engine and all with the same dxs dimensions because of general restrictions to cyls inside the frame - while on the outside possible volume would been lost. It was André Chapelon's major aim to give the twelve coupled engine an ample amount of cylinder volume to work on economic cut off rates up-hill at low speed. This he achieved by this rather unconventional design concept - and the six cylinder engine had a 3/4 rythm of exhaust beats. You may ask why not use but one instead of two smaller cylinders inside: well, that - to my view - was just due to the very short connecting rods on this inside drive to the second coupled axle: with two cyls arranged at 180 ° the piston force each was smaller and the drive was balanced. 

In general my suggestion would be never to use more cyls than can be arranged in one group aside each other, thus banning staggered arrangements in general. 

This may in a certain instance involve even fife cylinders side by sides - 

but that is another story ..

Juniatha

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Posted by Overmod on Tuesday, January 12, 2021 7:35 AM

M636C
Were Smith compounds ever used in the USA?

I believe Baldwin 60000 was a Smith compound, at a higher HP pressure facilitated by the watertube firebox.  It is my naive observation that several approaches to the idea were tried with various expansion ratios from about 2.3 to 2.7 -- the basic 1:2 with all cylinders equal apparently "leaving some money on the table" with respect to using the expansive energy fully.

 In light of the absence of resuperheat on long expansion of LP causing pressure drop in the latter part of the stroke, this may be less applicable, as in many 3- and 4-cylinder designs.  Again, subject to balance issues, some IP modulation may substitute both for reheat and fiddly adjustment of 2 separate sets of valve gear in getting equivalent thrust over equivalent stroke in all 3 cylinders of a Smith compound.

Since Juniatha is back -- she mentioned to me that the LP arrangement on 160 A1 was actually a 5-cylinder compound with the final LP stage divided into 2 cylinders primarily for clearance and packaging reasons.  She will be a reasonable authority to comment on the 152A.

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Posted by M636C on Tuesday, January 12, 2021 1:29 AM

Personally, I think this discussion can be likened to the mediaeval theological discussion about the number of angels that could dance on the head of a pin.

However, Overmod's contributuion:

 I do not have a fabrication diagram to show you, but think of a Trick valve made like two piston valves with internal passages arranged in series, made of stamped or formed metal for light weight.  (If I remember correctly the infamous 152P design had these and they show up in the longitudinal section drawings)

https://i2.wp.com/www.advanced-steam.org/wp-content/uploads/2017/05/JD-letter-image-1.jpg?ssl=1

at least caused me to look up the rest of the 152P. It appears as the last folding plate in Carpenter's translation of Chapelon's La Locomotive a Vapeur, plate XIII. This appears to be the same drawing as linked above, just the whole of the locomotive. I note that the centre cylinder drives the third axle while the outside cylinders drive the second. This meant that the second axle had to be joggled to clear the connecting rod, a feature common in Alco three cylinder simples.

But Chapelon had prepared an earlier 2-10-4 design, which I guess we can call the 152A since it preceded nationalisation. The "P" code was used for SNCF standard designs.

This was an enlargement of 160A1 complete with all six cylinders. (What could possibly go wrong?) Looking at this, I noticed that the low pressure cylinders were not all the same size. The LP cylinders are arranged in a line at the front, but the inside LP cylinders are the same diameter as the HP cylinders (ie, the biggest size that will fit between the frames. So I checked 160A1 and it was the same. Not only were they the same diameter but they were the same stroke. So clearly, since the outside LP cylinders were much larger in diameter, there must have been considerable variation in the tractive effort depending on cylinder position during  any rotation cycle.

So when did Chapelon abandon six cylinders?

Clearly when rebuilding the 241-101 as 242 A1....

Now to some extent his hand was forced - 241-101 was a three cylinder simple and converting it to a Smith Compound made sense. Chapelon still inceased the weight by about twenty tonnes (which was the original coupled axleload).

Looking at the drawing linked by Overmod reminded me of something.

On page 21 of O.S. Nock's The Midland Compounds on page 21 there is a cross section of MR 2631 showing a single piston valve under the centre HP cylinder. The outside LP cylinders used slide valves. The layout from January 1902 still worked in the 1940s. 240 Midland Compounds were built over 30 years, the most successful compounds in Britain.

Maybe one of those might have succeeded in the USA? Were Smith compounds ever used in the USA? I think Reading had some three cylinder compounds at one time.

Peter

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Posted by CSSHEGEWISCH on Monday, January 11, 2021 10:10 AM

I'm not a steam fan by any stretch but it's always good to see the return of a knowledgable contributor.

The daily commute is part of everyday life but I get two rides a day out of it. Paul
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Posted by selector on Sunday, January 10, 2021 11:45 PM

Thumbs Up Glad to see you posting again.

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Posted by Overmod on Sunday, January 10, 2021 11:20 PM

Paul Milenkovic
I second that sentiment.

I third it.

 

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Posted by Paul Milenkovic on Sunday, January 10, 2021 8:56 PM

Flintlock76

Look who's back!!!  

Christmas came a little late, but it came just the same!

Welcome back Juniatha!  You were sorely missed!  

 

I second that sentiment.

If GM "killed the electric car", what am I doing standing next to an EV-1, a half a block from the WSOR tracks?
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Posted by Flintlock76 on Sunday, January 10, 2021 5:20 PM

Look who's back!!!  

Christmas came a little late, but it came just the same!

Welcome back Juniatha!  You were sorely missed!  

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