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What is the Definition of SUPERPOWER? What year(s) first introduced?

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What is the Definition of SUPERPOWER? What year(s) first introduced?
Posted by JC UPTON on Saturday, December 19, 2020 6:59 PM

I have seen some very knowledgeable posts concerning steam engines. 

Many of them talk about "SUPERPOWER".  While I have a vague understanding of the term, I thought it might be useful to define:

1) The boiler conditions & size;  2) the Piston sizes;  3) the driver sizes;  4) the tractive effort; 5) the time frame of introduction; & 6) any other criteria that separate Superpower from the earlier locomotives.

If one were to apply the term to diesel-electric locomotives, what other types of questions might arise...?

 

Any thoughts?

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(In the shadow of the Huey P Long bridge)

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Posted by Backshop on Saturday, December 19, 2020 7:47 PM

Lima started using the term in the mid 1920's.  They had 4-wheel trailing trucks to help support a firebox large enough to produce enough steam for high speed operation.  Remember, this was the era of drag freights.

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Posted by Overmod on Saturday, December 19, 2020 7:54 PM

[quote user="JC UPTON"]"SUPERPOWER" -- while I have a vague understanding of the term, I thought it might be useful to define:

1) The boiler conditions & size;  2) the Piston sizes;  3) the driver sizes;  4) the tractive effort; 5) the time frame of introduction; & 6) any other criteria that separate Superpower from the earlier locomotives.

Of these, only 1 and 5 really apply.  Super-Power really originated with Lima, in 1925, with the A-1 design that evolved out of the NYC Mikado #8000 design.  The point is to have a combination of boiler capacity and running gear that can make full horsepower at higher speed, with a critical part of this involving evaporation and another critical part involving superheat.  Since more superheat involves more flues replacing tubes in the convection section, the design requires more radiant heating surface in the firebox and combustion chamber -- which, with better circulation via syphons and arch tubes, and the heavier construction entirely behind the last driver pair, leads to the use of two-axle trucks (or bigger) for appropriate weight distribution and guiding.

The locomotive itself ahead of the rear tubesheet is not that different from a good Mikado design, and the weight on drivers, the 'swept volume' in the cylinders, and other details may not be very different.  Something of a blind alley comes with large increases in boiler pressure, as this makes operation at lower speed with desired limited or short cutoff extremely peaky (i.e. more slip-prone) especially with more of the overall locomotive weight off the drivers compared to a Mike, and boiler servicing and repair costs go up disproportionally when pressures higher than about the 265psi NYC settled on having in the Niagaras are used.

There are also advantages in having a larger radiant section in that emission by burning high-carbon fuel (which is a luminous flame, something not easily appreciated by someone who has not actually experienced what a working steam locomotive develops) and uptake by black internal surfaces both scale as the fourth power of temperature.  So at high draft, a considerable amount of the effective steam generation shifts from the tubes to the radiant surfaces -- remember, this takes away some of the drawback of extra superheater elements in larger tubes.  

The principal purpose of the additional superheat is really to cut down on two kinds of condensation that sap power during expansion -- it is NOT to increase the power of the steam to do work on the piston.  You can easily have 'too much' superheat, which has a dramatic effect on the lubrication of parts in the steam space, particularly the valves and the portion of the piston and valve rod inside the cylinder as the piston and valve respectively move to front dead center (FDC).

A good Super-Power design also generally features limited cutoff, which means you can't keep admission open for longer than a percentage of the stroke.  Some designs (the PRR Decapod I1s being a notorious example, had extreme limited cutoff at 50%, so short that special slot ports had to be provided to assure starting steam.  While more than this is needed for best flexibility, the idea is still to run with the shortest possible cutoff to use steam most effectively... but you should have noticed by now that the power of the engine is determined entirely by the steam working in the cylinders, not how that steam is generated.  In consequence (if we ignore some of the superheat-related reduction in thermal losses) right up to the point you run out of additional steam-generation capability, a Mikado may produce just the same horsepower and TE as a Berk with much more weight and firebox capability -- it depends on adhesive weight on drivers, stroke and driver diameter, cylinder dimensions, and valve-gear characteristics.  This is simple external-combustion physics: steam is steam once in the cylinders.  What Super-Power assures is enough of it to get good drawbar pull even when the engine is at much higher cyclic rpm for the same driver and cylinder dimensions.

Later evolution in firebox design led to Lima designs requiring a three-axle truck to spread the weight accordingly, even on eight-coupled designs.  It could be, and has been, argued that this was a little too far for the benefit gained from it, and that better use of the Rankine cycle (for example, combustion-air preheat, better feedwater-heat recovery not just from the exhaust steam but the combustion gas as well (commonly known as 'economizing') and better circulation of water in the steam-generation spaces, for example) could produce the same effect as heavy construction slung off the back of the locomotive.

It does not make as much sense to apply either the term or the underlying idea to diesel locomotives, at least not diesel-electric locomotives, as much is different about how they work efficiently.  There, you are limited by traction-motor heating at the slow end, and by motor physics and back EMF on the high end, and in the middle you're limited by the constant horsepower your prime mover develops.  Increasing the size of that prime mover may come with drawbacks -- consider the nominal power increase of the SD45 over the SD40, in terms of the additional fuel consumed by it.  So "more" is not necessarily "better".

If we are to look at Super-Power diesel as being more working horsepower in a single unit, though, we might start with the Baldwin Essl locomotive of the late 1930s, which used modular 408-engined 'gensets' to produce a design hp of 6000 in a single articulated underframe chassis (which subsequently became the basis for the much lower horsepower Centipede prototype).  Other contenders might be the 'double diesels' pioneered by EMD (as B units!) and used on several Western roads, or perhaps the approach taken by CGW which at one point had a "passenger locomotive" (road number 116) composed of two FP7 cabs with steam generators and no less than five F7 boosters.  The criterion, though, needs to be achievement of the sort of operation the steam Super-Power facilitated, not just having more starting TE or more motors in a given carbody.

In my opinion, most of the current generation of 4400hp diesel-electrics 'count' by that definition, even though many of them retained DC traction-motor drive and much of their current use under PSR is restricted to sometimes extreme low speed.

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Posted by timz on Sunday, December 20, 2020 11:53 AM

JC UPTON
Many of them talk about "SUPERPOWER"

The term has no meaning now, and it was never intended to have any specific meaning. It was just Lima's marketing in 1925, trying to interest RRs in 2-8-4s and suchlike. The word caught on with railfans, who have used it ever since to describe big engines, of any sort (except maybe electric).

Lima claimed that RRs would be better off hauling tonnage trains with 2-8-4s rather than 2-8-2s or 2-10-2s -- a train with a given tonnage could get over the road faster. That's all Lima meant by Superpower -- better speed, due to more power, allegedly with the same tonnage. Nothing to do with cylinder size or driver diameter or anything specific.

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Posted by Overmod on Sunday, December 20, 2020 12:34 PM

timz
Nothing to do with cylinder size or driver diameter or anything specific.

Will Woodard would, I think, disagree with you on some of the important points distinguishing the A 1 and later approaches, and so would the designers of the Allegheny who so rejoiced when their horsepower curves came back 'better' than the original one for the N&W A (and who shoehorned heavy efficiency-making piping into the design to the extent they had to lie about the weight to the unions...)  I can say for a fact you'd have gotten some volubility out of Livio Dante Porta...

Super-Power has nothing whatsoever to do with "big" engines -- there are aspects of the improvements in the GELSA metre-gauge locomotives, for example, and in the Norfolk Southern vest-pocket Berkshires.  It does have to do with improvements that make better horsepower at speed -- and at least one of those does, in fact, involve cylinders, albeit dimensions: the idea that even with the increased nominal augment found in taking stroke up to 34", reducing piston and rod dimensions to keep the desired swept volume, and better applicability of long-lap, long-travel valve action, could produce faster and better locomotives.

It could be equally argued that the late-Forties enhancements Townsend and Lima were touting were 'marketing' rather than actual thermodynamic and performance enhancements -- for example, the combination of double-Belpaire with better defined radiant circulation that meant holding driver diameter to 76" or below; the use of improved Franklin type C valve gear of a number of types of drive; the implementation of Snyder preheaters and (presumably, eventually reliable) combined Turbo-Inspirators rather than heavy combinations of auxiliaries doing the same things -- but it would be hard to say that the combination of those elements didn't define a particular Lima philosophy.  And that is what Super-Power means to steam designers, perhaps as distinct from railfans.

Something we could also bring up would be the ways that Woodard and Lima in fact missed the boat.  If you look at the T&P 2-10-4s as built, and then compare them to the same locomotives as rebuilt in the '30s, you will see the stark difference between drag-freight efficiency and true horsepower at speed.  And it is not a large amount of detail change that produces this result ... but, please note, with a Baldwin Disc main and not something pioneered by Lima.

Woodard likewise had a decidedly pre-Eksergian idea of what a true high-speed locomotive ought to be, and while it might have been interesting to see his design for a 4-4-4 built for one of the early high-speed trains, I don't think it would have been more successful than, say, the Lord and Lady Baltimore were.  So this is not coherent genius at work, but rather the application of certain principles in significant ways, and we can identify (and not with overly selective hindsight) which of those constituted radical and lasting changes to road-locomotive design, 'not invented elsewhere'.

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Posted by Backshop on Sunday, December 20, 2020 3:45 PM

I'm just throwing this out there because I don't want to start another thread on the subject (we've had too many already).  This sorta concerns Super Power.  Maybe the reason the PRR T1 wasn't a success was that the people designing it didn't know what they were doing?  Think about it...the Pennsy hadn't designed a running steam locomotive in close to 20 years-the M1. Many of the engineers involved in that, at least the senior ones, were probably retired.  Baldwin was subjectively behind Lima and Alco in cutting edge designs.  Also, with their continual financial problems, they probably couldn't pay enough to keep any up-and-coming engineer from jumping ship.  So, you had two companies that were the largest in their fields, but both of which had fallen behind in the times, trying to design a cutting-edge locomotive.  Ain't gonna happen.  I expect to be flamed...

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Posted by Overmod on Sunday, December 20, 2020 4:44 PM

Backshop
I'm just throwing this out there because I don't want to start another thread on the subject (we've had too many already).  This sorta concerns Super Power.  Maybe the reason the PRR T1 wasn't a success was that the people designing it didn't know what they were doing?  Think about it...the Pennsy hadn't designed a running steam locomotive in close to 20 years-the M1. Many of the engineers involved in that, at least the senior ones, were probably retired.  Baldwin was subjectively behind Lima and Alco in cutting edge designs.  Also, with their continual financial problems, they probably couldn't pay enough to keep any up-and-coming engineer from jumping ship.  So, you had two companies that were the largest in their fields, but both of which had fallen behind in the times, trying to design a cutting-edge locomotive.  Ain't gonna happen.  I expect to be flamed...

No flame here, but I don't see incompetence, certainly not on the scale involving Baldwin and the ACL R-1 design.  Part of the problem was with the folks at PRR being just a little, shall we say, overtrusting in what they needed in a high-speed design.  Baldwin did try to tell them not to bet the farm on OC Franklin gear, and to design the firebox for 4-8-4 capability rather than assume 'perfect passenger gas coal' with the full economy in steam mass flow per dbhp that was supposedly coming from the duplex arrangement (before we start castigating PRR remember that Kiefer with the C1a made just the same estimation, involving the kind of accurate conventional valve gear and valves that Baldwin would likely have recommended).  PRR had meanwhile spent what may have been an ungodly amount with Baldwin in particular but also Alco and Lima underwriting fundamental development on the S1 passenger engine -- a very different and objectively "better" thing than the B&O and ATSF designs and the wacko '5/4 M1' project that became the Q1, but that swallowed down what might have been over $3.2 million gold dollars in 'research and development' as well as construction by the time PRR did what they'd do later with the BCR coal-turbine scam and said 'build us a product, not the know how to make them for  competitors'

That Baldwin was having fun with the lighter T1 and its specs (880 tons sustained at 100mph) can perhaps be seen in the talk Vauclain gave on the design at the conference in Atlantic City in 1942.  One point you won't see is that the stroke would have been shorter than 26" if Johnson et al. had had their 'druthers -- the dimension was fixed by the minimum web in the cast driver center between the axle and a roller main pin that would 'live' -- under stresses from an Atlantic-size running gear with lightweight rods!  (And at that, the main rod bearing point on that pin was ground eccentric to decrease the reciprocating-mass component even further!!).  The cavalier disregard that, say, this might cause the engine to stall with its 'design weight' train even with 300psi pressure, given really overly precise short cutoff, does not seem to have fazed either the Baldwin team or the PRR motive-power engineers.

Mind you, it's not like Baldwin was ignorant of the colossal propensity of a double Atlantic with 3200-odd ihp per engine and clean valve events to run away on a grand scale when one of four wheels lost adhesion.  The problem was they brute-forced it with ridiculously high FA, and then squeezed it even higher when slipping became something of an endemic characteristic of T1s.  One can clearly see the cost-effective fixes to this, even then... but by the time an organized fix-the-bugs effort has been conducted (in 1948) there was increasingly no point in any steam, let alone complicated-to-drive steam, in any kind of fast service that remained profitable.  Any little window in 1947 would have been squelched by the reintroduction of the V1 with streamlining and the Bowes drive, a true 140mph engine with no augment at all... 

Somewhere in here, in my paranoid estimation, is where the seeds of the great T1 as hopeless dog conspiracy got started.  Here's PRR desperate to dieselize but saddled with equipment trusts barely a couple of years old on a huge number of engines that a large number of engineers couldn't drive effectively, and for which only paralyzingly small alternative uses or users could be found.  How to get rid of this enormous liability expediently?  Why, make it obvious to bankers that the locomotive was a hopeless, slipping, filthy, unfixable failure ... and get them to handle the writing-off, resale not getting PRR out of paying off the trust on the sold engines.

Even so, many of the things were kept around far later than any prospect of practical use, where it more or less promptly revealed itself that modern alloy construction in locomotives was often a Very Bad Idea (a variant of this being what killed the A-2-A Berks on the NYC side).

It should be remembered, returning to the C1a, that the duplex was the anticipated postwar passenger engine as of April 1945 ... not E7s, certainly not a 75"-drivered midsize 4-8-4.  How quickly the Niagara demonstrated its 'sweet spots' can be seen in the following no more than months; what PRR might have developed using N&W knowledge on an 80"-drivered 4-8-4 ... or the follow-on Westinghouse turbine with the two-speed planetary drive ... instead of gang-producing passenger duplexes is perhaps also a matter of months (but practically, PRR was still worshiping the Lindbergh Engine in principle, and I suspect the Niagara wouldn't have been enough to dissuade them from it...

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Posted by Paul Milenkovic on Sunday, December 20, 2020 10:20 PM

Anyway, and as far as I can tell, superpower generically refers to putting 4-wheel trailing trucks on steam locomotives starting, I guess, in the mid 1920s, and Superpower specifically is a brand name from Lima of their Will Woodard-designed locomotives starting with their 2-8-4 Berkshire type.

ALCo (Upstate New York) and Baldwin (Philadelphia-based) were the big builders and Lima was the upstart from, Lima, Ohio that got its start building Shay geared locomotives and was trying to break into the big locomotive market.

The first Superpower product was the A1 2-8-4 Berkshire, where the formula included a lot of features, many new, some exotic and others catching on.  These include the 4-wheel trailing truck to accomodate a large firebox, and many of the the 4-wheeled types that followed -- 4-6-4 Hudson, and 4-8-4 Northern were small-s superpower.  Other features included a booster engine driving one axle of the trailing truck to use the larger boiler capacity for this steam-hungry long-cutoff geared steam engine, a truncated frame where the trailing truck carried the tractive effort to the tender, a largish ashpan that moved with this "articulated" trailing truck, and outside steam pipe from the dome running above the boiler, which I guess was to be higher up and get drier steam, a large superheater, and that 60% limited cutoff for steam economy on heavy pulls at the expense of more wheel slip along with the long cutoff steam-heavy booster that was to mitigate that on starting.

The 4-wheel trailing truck and the bigger grate and superheater were perhaps the only innovations to catch on, with the "articulated trailing truck" and floating ashpan being replaced by a more conventional arrangement, the outside steam pipe not going anywhere outside Soviet Russia or China, the booster being viewed skeptically on a cost-of-maintenance/benefit basis, and the 60% limited cutoff being regarded as an engine-slipping gimmick? 

The famous Nickle Plate Road Berkshires, I believe, did away with the booster, the limited cutoff, the articulated trailing truck and floating ashpan along with the outside steam pipe?

Lima's capital S Superpower also gave rise to the Texas and Pacific 2-10-4 Texas type, which didn't work out in service because it had some kind of resonance in its balancing or spring rigging that restricted its top speed.  And then there was the 2-6-6-6 Allegheny that was overweight, underdrivered and underutilized with respect to its record-setting high horsepower were it allowed to operate at higher speed.

Lima was going to come out with a 4-8-6 low-drivered Ohio type, a rather large number of non-driving wheels for a freight locomotive, I suppose with that Double Belpaire firebox arrangement -- flat on top and bottom to maximum tube sheet area, but dieselization did that plan in.

And we had a discussion somewhere about the Pennsy M1 Mountain type has holding its own for boiler capacity with its largish combustion chamber, even if limited to a 2-wheel trailing truck, along with the NYC Mohawks holding their own with the same wheel arrangement, where the Pennsy may have done better with an uprated M1 for their Next Big Passenger Engine instead of how the T1 turned out?

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 Sunday, December 20, 2020 10:25 PM

Overmod, this V1 your keep talking about, what would have been the Whyte classification, and Bowes drive or no Bowes drive, how would it get power to the wheels?  With the Big Gear and quill drive to the inner pairs of drivers carried by siderods to the outer pairs?  By Cardan shafts like on the KM "America Lok" diesel hydraulics?

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 Monday, December 21, 2020 7:15 AM

The V1 wheel arrangement was a bit weird: it used articulated cast underframes like a contemporary electric or the Baldwin Essl locomotive, but arranged strangely and unidirectionally, with the Q2-derived boiler's firebox between the sets of drive axles, a bit Meyer-like, over a bearer truck.

PRR used a weird (and not very helpful) Whyte designation of 4-8-4-8 for this: a better way to typify it might be 4-8-0+4-8-0 but you still need to be looking at the chassis for that to make full sense.  It used two 4000hp steam turbines, each driving four axles in the adjacent underframe via Cardan shaft -- these were relatively low wheels and I don't remember if flexible connections or 'flexible gears' were used in the drive as designed originally.  The boiler faced backward over the rear frame, with the cab space at the backhead and the coal bunker ahead of that (as 'stolen' by Baldwin for the C&O M-1 layout; there is some amusing discussion in the surviving motive-power records at the Hagley regarding the 'secret' Baldwin project to 'scoop' PRR on making a large passenger turbine).  Water -- and for 8000hp from atmospheric-exhausting turbines it would be a lot -- was from a separate water tender: strangely there didn't seem to be any real effort to use multiple such tanks even though production of the original V1 prototype was abandoned after the war primarily on water-rate considerations.

I did not see any indication in the surviving technical documentation of any attempt to put a planetary transmission between the turbines and final drives in the original, slthough Westinghouse went to the trouble of patenting a two-speed version for a PRR S2-style locomotive, recognizing the issues with slip, tip losses etc. at low rotational speed.  This is something that the Bowes drive would definitively fix, along with turbine overspeed at higher road mph -- reading a bit between the lines this is where the fancy "passenger" shroud design patent for this chassis configuration in 1947, inexplicable otherwise, comes in.

It is at around this point that PRR jumps the shark with this, though, by crayonista-style bumping the anticipated shp from 8000 to 9000 in 'future steam locomotive' publications.  It was and is obvious that the water rate of such a locomotive would dramatically limit its range just as its boiler chemistry made track pans undesirable (and dieselization made expansion of their use unthinkable)  And the Chessie-style monster luxury consists and rocket-fast peak speeds that would utilize the 9000hp did not materialize in the late '40s, in part because of the ICC order mandating better ATC for speeds 80-over in the wake of the Naperville wreck.

The design jumps, as common sense might predict, to the N&W, where the first grand mistake was made: the idea that individual-axle electric drive avoided a number of mechanical issues and allowed all-axle drive.  Then came the siren call of higher-pressure boiler with chain-grate firing (see the M2 Automatic), and Baldwin's fateful flirtation with Westinghouse motors in diesel-style trucks, as on the experimental rectifier for the PRR electrification.  Up to some point between 1950 and 1952 N&W was still working on the cast-under frame chassis, but were then pitched the idea of a single long frame on span-bolstered commodity trimounts… and it was off to the races with only 4500hp for all that length and all that complexity, just as diesels started to give second-generation power of 4800 divisible horsepower on the same trucks and GE woke up to the promise of immensely more horsepower out of the Cooper-Bessemer bottom end...

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Posted by wjstix on Friday, January 8, 2021 1:56 PM

In the "drag freight" era, the first decade or two of the 20th century, steam engines were not very large and freight engines needed small drivers to help them pull long trains - kinda like a truck using a low gear going uphill. Railroads found they could use like a 2-10-2 instead of two 2-6-0s doubleheaded on a long mainline freight...but the 2-10-2 might only have 50-some inch drivers so could only go around 20 MPH.

With development of the large firebox made possible by the four-wheel trailing trucks, engines could be built much larger and with more power. This meant you could now build an engine like a 2-10-4 instead of a 2-10-2, but with 10-15" larger drivers. This meant the new engine could still haul a long train like the old one, but at much higher speeds than possible before with low-drivered engines.

Stix
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Posted by timz on Saturday, January 9, 2021 11:22 AM

Paul Milenkovic
60% limited cutoff for steam economy on heavy pulls at the expense of more wheel slip

Lima and PRR said limited cutoff gave a smoother torque curve. Why do you think they were wrong?

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Posted by Erik_Mag on Saturday, January 9, 2021 9:39 PM

Backshop

Lima started using the term in the mid 1920's.

GE, Westinghouse and others were promoting tying together the electric power utilities in the Northeast to make a "Superpower" system ca 1921. This was in response to a post WW1 fuel shortage, the grid would allow generation by larger and more efficient power plants.

I suspect Lima picked that up for marketing their locomotive design philosophy.

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Posted by Overmod on Sunday, January 10, 2021 11:52 PM

Paul Milenkovic
Overmod, this V1 you keep talking about, what would have been the Whyte classification...

Steins liked to call it a 4-8-4-8 (which always bothered me) and an 'effective' Whyte representation can get into semantics.  Perhaps the easiest way to visualize what the chassis resembled externally is to take a Baldwin Centipede chassis apart at the center articulation and turn the 'back half' around so the two pieces are connected elephant-style.

Although the pirated design for the C&O M-1 came about a decade later than the V1, we can use those locomotives for comparison as they had somewhat similar ... as you might expect from a 'Concordeski' secret design crib ... arrangement.

Each of the two chassis had its own Westinghouse turbine, of about 4000shp, located longitudinally.  The coal bunker was in the nose; the modified Q2 boiler faced backward with the firebox over the second unit's four-wheel 'lead' truck, with the cab at the backhead so conventional stoker arrangement could be used.  All water was carried in a separate 'water tender', which on the design approved for production was not 'bidirectional'.  There was no trailing truck.

... Bowes drive or no Bowes drive, how would it get power to the wheels?  With the Big Gear and quill drive to the inner pairs of drivers carried by siderods to the outer pairs?  By Cardan shafts like on the KM "Amerika-Lok" diesel hydraulics?

More like the second.  As far as I know there was no clutch on the original to allow the turbines to be spooled to warm them, and I have not been able to find the reversing arrangement.  The drive shows as Cardan shafts to right-angle gearboxes; I believe the wheels were a comparatively low 40".

The great point of the Bowes drive was that it constituted an electrical under/overdrive with no contact even with considerable axial displacement between the turbine output and the driven shaft.  This meant that unlike a clutch the turbine could be sped to a reasonable tip speed/slip percentage even at low road speed.  I have not run comparisons on whether torque multiplication in a Voith-style torque converter might have been more efficient, but I doubt in the late '40s anyone could produce a torque converter that would serve to connect 4000hp reliably to mechanical drive to jointed "wartime"-maintained trackage.  

PRR later 'vaporwared' (a somewhat apt term!) the revised V1 design up to 9000hp, which might have involved a revised boiler design; the water rate even with a B&W or Lamont boiler would have been ridiculous for a single unit with atmospheric exhaust, on the order of about 100 miles between water stops with the water-tender design originally specified.

The interesting thing about the 'revised' V1 with Bowes was that it had no fixed high-speed limit other than that of the primary Bowes winding, which turned slower as the final-drive ratio indicated.  That made any T1-capable speed possible without any augment at all, at higher nominal efficiency, and this made it very briefly exciting as a passenger engine for the huge luxury trains that the Chessie was to be the advent of.  (There is in fact a design study for streamlining that can only be for the V1 chassis, dated some time in 1947...) 

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Posted by Juniatha on Saturday, March 6, 2021 3:31 AM

timz

Quote "Lima and PRR said limited cutoff gave a smoother torque curve. Why do you think they were wrong?"

They weren't - it's correct! Around 50 % you get the smallest jumps in a circular t.e. diagram of a two-cylinder engine, and it could and should be accompanied with a minimum of lead intake at that stage of running (this automatically means you have to provide for a variable advance because you want a larger lead at increasing speed.

I was given the opportunity to make some small tests myself when I visited (German) locomotives in Poland in 1990 / 91 / 92 (93). At Wolsztyn two crews let me drive their engine. I had coaxed them by doing some firing first - they liked that for obvious reasons, I didn't care because it got me what I wanted to get. So on several tours, I mostly drove some 52s (PKP Ty-2/42) and the one 42 (Ty-3). Generally we had stopper trains that called at every station - so lots of opportunity to start away. Only once I was so lucky as to be on the footplate when a 52 had to step in for an Ol49 Prairie on a semi-fast out of Poznan on the mainline and we had to accelerate quickly and go full speed all the way. The engine had plenty of play in bearings, but she ran straight ahead, no nosing, only the coal wandered forward on the fire - but she did the job without complaint!

Usually, I started a train at ~65% and as soon as the engine turned wheels I linked in to 50 .. 45 % and opened up wider. No engine ever slipped (although there was one incident that had an alarming moment to it - later!). With the 42 that was in quite good mechanical condition, I once even linked in to 40 % and opened up fully, keeping the large lever tightly gripped in expectation of a possible hefty slip - after the first "hushshh" she leaned in and I felt a slight pull back, there came the first loud beat "WHOOM!!" and then continued "Whoom! -- Whoom! - Whoom! Whoom! Whoom whom whom .." - no slip, just a strong start! The driver suspected at once what I had done, one glimpse on the reverser screw and he turned at me with a peculiar smile, but said nothing, just when I liked up further, the fireman cracked the door open and with a "Frau starke Lokführer! (Woman hard driver!)" he placed shovel after shovel into the bright fire.

That one incident: I was on a 52 that was a little bit her own, asked the driver if he would let me ... "Na tak!" (well, yes!) he made an inviting move with a strange glimpse at his fireman who returned a silent smile. I was warned - jet I thought: he had started the train before with no noticeable trouble - so what was it about? The "Go!" signal came and I opened the lever across - I wanted, that is: the lever went to 1/2 way open lightly without resistance then stopped at a rock-hard point - no more move! Now I didn't want to give them reason to say "There! this is a man's work - women can't do it!" So in my mind I quickly ran through possible reasons and what to do, but came to no grips except he had done it - so I should do it, too. I pulled back the large lever and opened with a vengeance, banged it against that midways stop, and one more time tightly gripped I decidedly banged it to the left, thought: 'now you open because I want you too!' - and it did, I overcame the spot and the throttle uplifted, but now it wanted to pop open fully and pulled the lever and with it me fully to the left, but since I had gripped it tight I pulled it back 1/3 - one huge "BWOOMM!!" but I just got along without a slip, I quickly linked up to 45 % then she settled to a decent start and everything was back to normal. The driver nodded, spoke to me smiling, I didn't understand his Polish words but I got his appraisal. He let me drive all the rest of the trip and I learned with the right 'bang!' it wasn't too hard to open up.

What had happened? My idea was, the Wagner saturated steam throttles have a small governing valve that you open with the lever. To that, the main valve follows as soon as pressure builds up in the valve chamber (to the amount you have opened up), the throttle can thus be opened quite easily with but some smooth resistance that gives you a feeling of what happens. With this one throttle, the lead valve was obviously stuck tight in the main valve, so you had to crack the large valve open by hand, which was possible only by allowing a first amount of steam to squeeze past to build up some pressure in the valve so then you could open it further. This was the opposite of the usual wacky slack generally present everywhere in these engines.

Long time since ...

https://www.youtube.com/watch?v=b-FUH84F_po

https://www.youtube.com/watch?v=Ay9WnXW6ycg

Sade - Hang on to your love (and other)

Juniatha

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