A special thanks to skidderback for helping me with this subject and I thought anyone not familar with the steam loco would like to read this as well.
This is probably more than you’re looking for, but here’s the skinny on steam engine classification…
As far as steam engine classification goes, they were classified in general by the type of design of the locomotive, such as single expansion, compound engine, saturated steam, super-heated, rigid and articulated, with the latter sub-categorized as duplex and triplex. These engines were further classified by their wheel arrangement, in most cases, of the later engines manufactured.
If one tries to answer the questions regarding who came up with the idea of a steam engine, or the year the first was built, the point will be argued. But, in actuality, the answer is not in the 18th or 19th centuries. The first steam “engine” was conceived by and made by Heron of Alexandria. It was a simple device, consisting of a hollow sphere that rotated on an axis of pipe, that pipe supplying vapor to the sphere from a container of boiling water underneath. The sphere was fitted with two exhaust pipes that rotated the ball as would two jets do. This was more than 2,000 years ago. Just think. If the next step of putting this on wheels to perform work or even remaining stationary, the industrial revolution would have happened 1,850 years before it did. How would our world appear today?
Since we are speaking only of classification, operation and the details of how they work won’t be covered here in depth. A “saturated steam” engine, also called a “soaker,” is as its name implies, simple steam under not too high pressure. As technology increased, the “grate area” of the firebox increased, allowing for more heating area. Boiler size increased as well. It was these larger engines that became the super-heated variety. There were "feed water heaters
I haven’t read it entirely, but did note an error. A Duplex engine is not necessarily articulated, so it should not be classified as a subset of “articulated” engines. I think of the Pennsy T1 which had two engines, but which were simple steam and neither engine was articulated. Both were fixed.
You did some SERIOUS research, by golly. However, as Crandall noted, Duplexes were not ‘articulated’, they were fixed-wheelbase locos and used four cylinders for speed, not to articulate the loco around curves. If I remember correctly, only Pennsy and B&O used these locos, but–at least with the Pennsy–with quite a bit of success.
Also, you forgot one of the MAJOR ‘simple’ articulateds, BTW, the 2-8-8-4 o0000 0000oo also known generally as the Yellowstone. Over 70 were built for major US railroads (far more than the more popular 4-8-8-4 oo0000 0000oo ‘Big Boy’) and were used coast to coast very successfully. There’s also a friendly and on-going argument that the Southern Pacific 4-8-8-2 Cab-Forwards (class AC-4 and up) are ‘backward’ Yellowstones, which would make that wheel arrangement–forward or reverse–the largest series of articulateds ever used in the United States. One camp says that the 4-wheel ‘leading’ truck on the cab-forward was to support the cab and the firebox, another camp says that the 4-wheel truck was simply to guide the locomotive at speed through curves. Actually, it did both. Just as on the ‘backward’ Yellowstones, with the 4-wheel trailing truck supporting both an extended firebox, and in the case of the Missabe Yellowstones, a large all-weather cab. So either argument works.
But I like your research. It’s good to have it shared.
The T1 as well as the S1 (6-4-4-6), Q1 (4-6-4-4, 1 produced) , and Q2 (4-4-6-4, 26 produced) were all Duplexes. They had solid frames with two steam engines in the frames. I believe that by definition, a Duplex has two steam engines in a single rigid frame. (If I’m wrong, I’m sure someone will correct me…
One comment (on a very well-researched and through discussion): Locomotives became “superheated” not because of the increase in boiler and firebox size, but because the steam produced in the boiler was fed through “superheater tubes”, which doubled back through oversized boiler flues to be heated by the extremely hot air roaring through those flues from the firebox. Thus, the steam, instead of being at 212 deg. F. might be heated to double that or more, increasing the energy of the water molecules in the steam, which in turn raised the pressure of the steam, producing much more power when introduced into the cylinders. More bang for the buck, you might say.
Oh, and it was Hero of Alexandria, not Heron (a bird). Some number of centuries BC, in ancient Greece. [:)]
It might also be noted that the Whyte system of locomotive classification by wheel arrangement goes futher than just for steam locos. It also works for diesels and electrics, using alpahbetic letters for powered axles in a truck, and numbers for unpowered axles. Thus, an E-7, -8, -9 is classified as A1A-A1A, with two six-wheeled trucks with unpowered center axles, and a GG1 is a 2-C-C-2. And a DD40 is called that because it had two 4-axle trucks and produced 4,000 horsepower. And a plus sign is used to designate separately powered engines in a duplex that are linked by rod or crank, as some French steamers were.
One interesting thing about the Whyte wheel arrangement for articulated steamers–it seems some years back that TRAINS magazine (I believe) decided that instead of using dashes to designate the wheels on Articulated locomotives, that a plus sign be introduced instead. So instead of say, a 2-8-8-2 designation, it was to be a 2-8+8-2 designation. That always made me think of the designation of a Beyer-Garrett locomotive instead, where there were actually two SEPARATED locomotive running gears under one coal/boiler/water-tender arrangement (such as 4-8-2+2-8-4), instead of two closely wheelsets under one boiler as per Anatole Mallet’s original design.
I presume that idea has gone the way of a lot of ‘Revisionist’ History, am I right? Or does it still exist? I don’t seem to find it used anymore.
Good information here. But it all begins to break down, eventually.
A number of wheel arrangements (sometimes common) didn’t have names beyond a description, such as 2-6-6-2, 2-4-4-2, 2-8-2+2-8-0 (a weird, articulated duplex with a regular Mikado locomotive with a Consolidation under the tender), 0-6-6-0, 2-6-6-0, 0-6-0 (three-axled/six-drivered switcher), 0-8-0 (four-axled/eight-drivered switcher), etc. One can’t definitely tell by the Whyte system whether a locomotiave is articulated or a “duplex” (rigid-frame or articulated frame) as in an 0-4-4-0 (where I’ve noted prototypes with one fixed body frame, two articulated frames, and three articulated frames: B-B, B+B, B+0+B).
I wonder, should a two-truck Shay/Heisler/Climax be described as 0-4-4-0 or 0-4-0-0-4-0? What about their three-truck versions (0-4-4-4-0, or 0-4-0-0-4-0+0-4-0, or what)? It all gets rather confusing. Better is a system which uses numbers for idle axles and letters for powered axles, where a two-truck version is a B-B and a three-truck version is a B-B+B (where the plus sign indicates an articulation point), and that weird articulated duplex would be described as a 1-D-1+1-D-0.
And while I’m at it, the SP didn’t identify its 2-10-2s as Santa Fe (arch-competitor) types. They were officially class “F” for Freight and dubbed decapods or decks by its employees. The SP had less than a handful of inherited “real” 2-10-0 decapods for more than a few years.
Don’t worry! This is the real world: ninety-something percent of the time the rules work, the other times they don’t.
Okay, if we are all going to make corrections, this is mine,
QUOTE:
The triplexes were few in number, built by Baldwin Locomotive works, for eastern coal hauling roads, like the Erie. Cumbersome, nearly impossible to counter balance due to their complexity and as a result, twenty miles per hour was about tops. But. it could do the twenty miles per hour all day long, up hill and down, dragging 12,000 tons of coal around.
My understanding is that the great weakness of the triplexes was that they would run themselves out of steam, so running them at their top speed all day long didn’t happen. As I recall, they would some times have to stop to rebuild steam pressure, as the boilers were not adequate for the working capacity of the Locomotives cylinders.
Actually the Garrat is one of the most successful steam locomotive designs ever developed, and several of these are still in use today - mainly in Africa. One of the very big advantages of this design is the possibility of an extremely fat boiler with deep firebox but nonetheless an ashpan large enough - because no running gear could limit these factors.
David Wardale of Scotland - one of the very few steam locomotive designers existing today (and the creator of the “RED DEVIL”) - wrote the real reason that the use of steam locomotives has ended in the USA (and therefore in the entire world thereafter) was the failure of the US designers to adopt the Garrat. He explained this extensively - even with a very credible example - and I am 100% behind him.
BUT: I am very happy that all those mallets and articulateds came to life, because esthetically mostof these in my eyes are much better than ANY Garrat.
Norfolk & Western used Y class Mallets in hump and yard service as well as mainline drag freight.
Which brings me to my version of the glaring omission. WHERE IS THE N&W CLASS A??? That 2-6-6-4 was rightly referred to as The Mercedes of Steam, was a true high-speed articulated, extremely successful and outnumbered the Oversize Kid 43 - 25. Also, it could be, and was, used all over the railroad, not just in one limited location.
As for the +, it was used to denote steam with non-coupled multiple engines (Garratts) and electrics where the ‘truck’ frames were coupled and buffing forces were not taken by the carbody (making the GG-1 a 4-6+6-4.)
Last - the Mason Bogie locos were articulated, even though they only had one set of drivers. The engine frame could swivel under the boiler.
I get a kick out of that–‘Decks’. Same thing with Rio Grande and THEIR 2-10-2’s. “F’s” for freight. 81 for thousand pounds of TE. So we get F-81, which means a freight locomotive with 81,000 lbs TE, instead of Rio Grande, like SP, having to admit that their particular wheel arrangements were originally built for their arch-competitor, LOL!
During WWII, the SP would occasionally use a ‘Deck’ as a westbound helper loco out of Truckee–usually on the front end of the ruling AC–and my great-uncle Tom would tell me a story about a ‘newbie’ firing up the AC as the Deck backed toward the loco–“Hey, it’s a Santa Fe.” Evidently the engineer of the AC gave the ‘newbie’ a rather colorfully worded lecture on the difference between an ATSF $#%@&!! “Santa Fe” and an SP “Deck” all the way from Truckee to Norden, LOL!
Those several classes of SP ‘Decks’ were quite the handsome locomotives. Haul anything you wanted to put behind them if you didn’t need to get there fast–though I’ve got a clip of one cutting some pretty fast grass between Oakland and Sacramento on the Valley line. Either that, or the film’s speeded up. [}:)]
Haven’t heard any mention of the 0-6-6-0T used in logging operations either. Nor has anyone mentioned the 2-4-6-8 (Who do we appreciate) for that matter. (Sorry!)
Vulcan is not a geared loco, but like the shay and heisler and climax, its drivers are mounted on trucks with direct piston drive. might call it an 0-4-4-0, but Vulcan is the correct name.
2-4-4-2 - Little River engine, no clue on the nick for it.
I recall the Trains debacle on the trying to redo the identifying convention, I was appalled by it. I guess it waned away…quickly…that would make me think of a Garret as well on an articulated.
Click picture to enlarge