Okay, here are a few that I am aware of:
Monon 4-10-4
Central Railroad of New Jersey 4-6-6-4
Great Northern 2-8-8-4 with 69-inch drivers
Great Northern 2-6-6-4 with 73-inch drivers
Great Northern 4-6-6-4 with 73-inch drivers
Union Pacific FEF-4 4-8-4 with vestibule cab
Union Pacific 4884-3 with 4-10-2 33,000 gallon tender
CSSHEGEWISCHThe list might be a long one since I'm sure that there were any number of high-performance steam designs on the drawing board that were never pursued because of the advent of diesels.
Actually the list is not 'all that long' because a couple of fairly dramatic limits were hit right at the end of the Golden Age that were problems on 'high performance'.
The Pennsylvania hit a big one in designing the Q2 wartime engines, and the V1 turbine that would have used its boiler just a bit more effectively. It needs to be remembered that, unlike large 'gas engines', a Rankine-cycle powerplant requires a separate working fluid, and in a locomotive that working fluid is lost to exhaust on any practical high-horsepower design (condensing requiring too much surface area, let alone construction and maintenance cost, to be used). Keep in mind that every gallon or pound of this water needs to be chemically treated with caustic materials, ideally kept deoxidized, etc. and the salts and solids in the water or its treatment can't be allowed to carry over in the steam. Meanwhile ... look at what Q2 horsepower implies in lb/hr even of 300psi steam, let alone if you run partway at some reduced pressure. That translating into lb/hr of feedwater, through a complex system that taps or bleeds off still more mass flow to administer itself. All of which, on the Pennsylvania at least, would have to be carried along as you went, in some enormous tender made even more colossal by the amount of fuel necessary to turn that water into the required mass flow of steam.
In short, the V1 (which was already technically limited by its bunker capacity), with the largest practical water capacity it could carry or have arranged for it, had an anticipated range of no more than about 130 miles between mandatory water stops. Doubtful that you could provide turbine-grade feedwater, let alone pH 11 feedwater, out of track pans for any length of time, let alone today. For another view of the magnitude of the treatment issue, look at many of the pictures of PRR J1s and ATSF 5011 class on the Sandusky ore service in the mid-Fifties -- see all that white stuff? That's just the boiler treatment from leaks and blowdowns...
Then we have the emergent problem with mainpin integrity in locomotives with lightweight (low-augment) rods that develop high horsepower at speed. Chapelon's comment on what he concluded was massive transverse bending in Timken lightweight rods is probably important to remember in this context. Watch the utterly crippling road failure rate go up, up, up.
Well, I hear you cry, we can get around that with motor locomotives, like those Roosen worked on in Germany (one of which came here, along with the V2 and other tech wonders, perceived as strategic war booty) and the B&O W1 which got much further along than I think most people recognize. These were a better fit with American practice than, say, one of the Sentinel "mainline" engines (which strike me as being just a bit dotty in the way the Fell locomotive was dotty) and yes, the W-1 in particular would have been a grand thing to see -- if only Emerson had lived a couple of years longer, and Willard hadn't had the example of the EAs to show him where B&O's future clearly was.
Interesting, perhaps, that the whole anticipated revolution in steam-powered 'lightweight motor trains' failed to thrive: I for one would have found a PRR E8 Atlantic designed with the example of a Milwaukee A 'in view' to be a highly interesting thing (and fully capable of actually achieving or beating that old-wives'-tale "127mph" claim for an earlier PRR 4-4-2). That was still the era, even in the Depression, that effective streamliners got so much patronage that they needed to get bigger, longer, and larger to the point of 'postwar' streamliners, Dieseliner service, etc. which was just the thing a Niagara could do well (and a C&NW locomotive, virtually a clone of the Milwaukee F-7, almost not at all) at the appropriate scale.
CSSHEGEWISCH The list might be a long one since I'm sure that there were any number of high-performance steam designs on the drawing board that were never pursued because of the advent of diesels.
The list might be a long one since I'm sure that there were any number of high-performance steam designs on the drawing board that were never pursued because of the advent of diesels.
I think not. I DO agree there's a list, but I don't see it being long.
Draftsmen need to get paid (just ask them). To be paid, they need to be putting money in the bank for the company. "High-performance steam designs" that are "never built" (see topic title) do not do that. If they are not built, they cannot be sold. For a profit.
So steam locomotive designers and builders had to walk a tight line between productive drawings and speculative drawings. The latter MIGHT provide some profit at a future time; the former will do that sooner.
Consider, also, the above quoted phrase: "...never pursued because of the advent of diesels." That implies an economic threat for steam locomotive production. That's not exactly the right time to be assigning a (paid) team of draftsmen to draw up bigger oars for the lifeboat.
Ed
PS: I DO like examining advanced steam locomotive design.
I for one would like to have a LV expert 'in the know' tell me specifically what that little four auxiliary axles in the prospective 4-4-6-4 diagram were to go to. I'm betting semipermanent water tender, thinking about anticipated water rate ... but I don't know.
The New York Central C1a deserves far more attention than it typically gets as the 'unworkable duplex version of the Niagara'. I have covered some of this in other posts, including the reason why the proposed 64T tender would work for this locomotive but not as much for the Niagara 'alternative'. (Incidentally, this is likely to be far easier to be a 'new build' than a Niagara would be, due to the relatively large number of common dimensions with a PRR T1...)
While you're discussing 'atomic bombs', we might remember the Alco A-100, which proceeded to the point Howard Fogg could do a fairly detailed sketch of one. Highly interesting by comparison with weird alternative schemes like Lyle Borst and his students ginned up...
... and elsewhere with Fogg, we have what may be the only surviving view of an FEF-4, which (somewhat astoundingly for any outfit except UP) was to be fitted with a quatrefoil stack arrangement similar in operation to the one on the PRR S2. How this was actually arranged internally and proportioned is unknown to me ... but I'd certainly like to see the data!
Not quite 'unbuilt' but in this category nonetheless are the two Union Pacific prewar steam turbine-electrics (of ~2500hp apiece, but usually run as a 'pair locomotive') after the bugs in them were worked out on GN during WWII service. These were high-performance locomotives that had the signal disadvantage of being obligate oil-fired but even more complex and expensive than an equivalent in diesel horsepower ... and having materials in their turbines that had value for GE 'elsewhere' in that era. I believe they were scrapped to further the war effort - had they not been, we might have seen the design elements contribute meaningfully to at least early postwar development. Alas! the only surviving 'documentation' of how the GN and GE people worked on these locomotives is in the fast-disappearing memories of those who did. Wartime secrecy was not helpful, either.
In reading various books and articles, there are numerous references to steam locomotives contemplated by various railroads that were never built for one reason or another.
For instance, in the Spring 2019 Classic Trains there is an excellent article about Big Boys running on the Los Angeles & Salt Lake between Ogden and Milford UT for 9 months in 1943. They apparently performed so well, pulling 5,600-ton trains at 60-65 mph, that the UP was drawing up plans for a 4884-3 class 4025-4029 that would have been oil-fired and had 33,000 gallon tenders on a 4-10-2 wheelbase (with the single-axle truck on the rear helping to guide the tender on reverse moves).
These units were never built due to use of the two atomic bombs shortening the war.
Are there other contemplated-but-never-built locomotives that you’d like to share with the Forum?
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