ATSF 2-8-10-2

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ATSF 2-8-10-2
Posted by ShroomZed on Wednesday, December 25, 2019 5:55 PM

I've been reading Worley's Iron Horses of the Santa Fe Trail; and I came across a proposed design I previously had no idea about; a simple articulated 2-8-10-2 thought of in December 1930, probably spurred on by the success of the Madame Queen one year before. 

Dimensions are simply astounding. 27 & 30 X 34" cylinders, 275 PSI boiler, 69-inch drivers, enormous grate area of 175 sq. ft, average driver axle load of 70,000 lbs, tractive effort of 170,000 lbf, total heating area of 8348 sq ft, coal consumption of 142 lbs per square ft, max boiler diameter of 115 inches, a total engine weight of 730,000 lbs, and a total length (loco and tender) of 140' 2 7/8" overall. 

If this locomotive was constructed, it would be known as one of the largest steam locomotives ever built. Are any of you aware of this design and what do you think of how it would have got on? 

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Posted by ATSFGuy on Wednesday, December 25, 2019 7:59 PM

I've seen a regular 2-10-4 "Texas" and a 2-8-2 "Mikado".

But I've never seen a real life scale or model of a 2-8-10-2.

 

However if such a locomotive existed:

1. It would be extremely large and a huge nightmare for shopcrews when it came to servicing, but very cool to have in HO Scale!

2. It would look like a Texan and Mikado combined together

3. I'm not sure where or what part of the system these locomotives would have been assigned to on the Santa Fe.

 

My best guess is Santa Fe would have tried it out for maybe a year to get a feel for it, see how it preformed, and what it was pulling abilities were like. Since this locomotive looks more experimential to me it could've be used for a year or two, then disposed of somewhere. Anyone knows more info about this configuration, please explain.

Did Santa Fe like Massive Articulated Steamers?

 

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Posted by Flintlock76 on Wednesday, December 25, 2019 8:50 PM

As a rule Santa Fe stayed away from articulated steam locomotives.  During WW2 they aquired some Y3 2-8-8-2's from the Norfolk and Western to handle the crush of wartime traffic, but that was a special case.  Santa Fe didn't like the extra maintanance and shop times articulateds called for, so typically they went for the most powerful coventional locomotives avaiable.  

I believe they tried a 2-10-10-2 around the time of the First World war, but that one turned out to be a flop. I think it was turned into two 2-10-2's.

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Posted by ShroomZed on Wednesday, December 25, 2019 9:13 PM

The ATSF constructed a variety of truly bizarre mallets during the early period of American articulation, ranging from high-drivered passenger-oriented 4-4-6-2s, to 2-6-6-2s with jointed boilers of a few different types that worked as well as you think they would, to enormous 2-10-10-2s that were split within a couple years of construction. The most conventional and the least unsucessful were a couple 2-8-8-2s built in 1909, but even these were split up within a few years. 

All of these designs had extremely long and complicated boilers that were split into a conventional boiler and early feedwater-heaters and reheaters. The 2-10-10-2 engines were so long they had to be run backwards with sloping tenders for ease of visibility. 

I think they were all gone by the mid twenties, and the failures of these designs lead the ATSF to never return to articulation apart from some borrowed N&W Y classes during WW2. Interestingly the ATSF were impressed with the boilers on the Y class and planned to use them to rebuild the 3751 class yet again, but dieselization put an end to this and they were returned to the N&W. 

It's somewhat ironic the ATSF is most known for it's large, no-nonsense simple engines of later years when for much of it's history, the ATSF was one of the more willing to try risque and innovative engineering practices, including sticking to rigid-frame compounding far longer than any other major road. 

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Posted by Overmod on Thursday, December 26, 2019 3:54 AM

Was this in the 'Iron Horses that Didn't Make The Trail' section?  I thought I had read my copy of that book fairly carefully and this thing would have stood out as catnip for me in a great number of respects... and the design is almost early enough to make it into Wiener's Articulated Locomotives.

It makes as much sense as any 'size increased' Super-Power would.  The 69" wheel and 34" stroke would likely not have happily coexisted as built but would rapidly have been rebalanced along the lines of the T&P improvements in the mid-Thirties; the 275psi is suspiciously low for ATSF planning and I suspect you might see it increases in order to rebush/sleeve the cylinders to get the piston mass down as in the AMC designs (retaining the long stroke).

This being a coal burner would give away where ATSF was planning to use these, as oil firing would have been established for large mainline designs (and in my opinion with particular value for a firebox and presumably chamber of these heroic proportions).  Depression-era traffic reductions are probably associated with this project's demise; it is interesting to consider if Baldwin would 'crib' Alco's design for high-speed articulated stability (which N&W had, and documented, several years early in the A class design) and go to 74" to match the upsizing in the 5001 class... now THAT would have been a wartime engine to watch!

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Posted by ShroomZed on Thursday, December 26, 2019 9:05 AM

Overmod

Was this in the 'Iron Horses that Didn't Make The Trail' section?  I thought I had read my copy of that book fairly carefully and this thing would have stood out as catnip for me in a great number of respects... and the design is almost early enough to make it into Wiener's Articulated Locomotives.

Yes. There is a diagram and small table addressing it on page 377 with all the dimensions I described. 

Overmod

it is interesting to consider if Baldwin would 'crib' Alco's design for high-speed articulated stability (which N&W had, and documented, several years early in the A class design) and go to 74" to match the upsizing in the 5001 class... now THAT would have been a wartime engine to watch!

Indeed. The thing I'd worry about then though is that the firebox would have to be incredibly shallow to rest upon 74" drivers. 

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Posted by SD70Dude on Thursday, December 26, 2019 12:56 PM

This must have been intended as a low-speed drag or pusher engine, the boiler likely could not have kept up with the cylinders' demand for steam once you got up to 15-20 mph.  The same problem was found on the Triplexes and the 2-10-10-2's

Greetings from Alberta

-an Articulate Malcontent

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Posted by Overmod on Friday, December 27, 2019 10:39 AM

ShroomZed
Indeed. The thing I'd worry about then though is that the firebox would have to be incredibly shallow to rest upon 74" drivers.

Ah, but not so!  Remember that the lift is only 1/2 the diameter increase, so the grate is lifted only a maximum of 2.5".  You can calculate the decrease in available radiant uptake area by multiplying this by the perimeter obtained from the actual dimensions of the enormous grate.

This is several years before the first of the Challenger designs with their obligate shallow grate and firebox arrangements, but I think there is nothing particularly novel about either the theory or the practice of providing an extended grate or chamber above the drivers at its forward end.  Same consideration applies to either using a 4-wheel trailer (as in Challengers) to get a larger firebox, or a Delta-style trailer as in the first iteration of the N&W Y7 design (since weight-bearing, weight distribution and effective chassis steering are less critical in a Challenger design than they are for the deep-firebox equivalent).

You would ASSUREDLY benefit from a Cunningham-circulator manifold in the water legs, and perhaps jet-pump flow to the necks of whatever syphons or circulators were provided in the cavernous maw to give better short-TOF radiant uptake.  Likewise from Snyder primary-air preheater arrangements using some of the exhaust steam.

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Posted by Overmod on Friday, December 27, 2019 10:59 AM

SD70Dude

This must have been intended as a low-speed drag or pusher engine, the boiler likely could not have kept up with the cylinders' demand for steam once you got up to 15-20 mph.  The same problem was found on the Triplexes and the 2-10-10-2's.

You have not recognized the very significant difference between the ATSF 'Super-Power' design and the earlier examples you cite.

Now, according to Brashear, even if there had been no 'Super-Power' combination out of Woodard, ATSF had thoroughly learned the important lesson from the 2-10-10-2s: effective use of very large radiant area for steam generation, rather than treating the firebox as a hot-gas generator for a convection section.  They also understood by no later than 1923 the relative value of very high pressure in achieving high early cutoff.  The Triplexes were not really 'underdrafted' (which is the common reason given for their 'too many legs and not enough steam'; half the exhaust going to the 'scape-pipe on the tender without even producing available 'feedwater heat') but their boiler couldn't make enough steam even at reasonable cutoff to make any kind of cyclic speed at small driver dimensions.  Henderson shared the ATSF small-firebox fetish, even when the truth was staring him in the face: we see him sanguinely providing more and more motor-tender capability in quads and quints ... without providing more actual fire at fourth-power uptake to pay for it all.  Riveted-construction Jacobs-Shupert fireboxes only compounded (no pun intended) the agony.

This locomotive is explicitly a simple articulated, and determining its suitability is really little more involved than figuring the necessary steam mass flow to get, say, a good Texas type and a good late-era Mikado, say a GN O class, up to speed with load.  69" drivers are part of the key here; think of them in part for the same reason Golsdorf did, decreasing the cyclic rpm that wastes steam mass, and allowing lower machinery speed, exhaust throttling loss, compression problems, etc.

Had this been a pusher design, it would have involved lower drivers and a boiler pushed out to the limits of shop loading gage.  Even so, a 63" wheel proved perfectly balanceable by the mid-Thirties ... once the importance of lightweight rods and angled/dynamic balancing was better understood.  I might add that a 175' grate on a short-distance pusher engine is overkill ... it is most certainly not on a higher-speed engine perhaps intended to take a train 'intact' delivered to it by, say, one of the pathetic original-build 3751 class and run it straight over Raton without need to tinker with either helpers or snappers...

It is really not this design per se, but what the people who rebuilt the 3751 class would have done with the design in a comparable timeframe (1938 to 1941).  Refit it with disc mains (or better) and perhaps do as they did: higher boiler pressure, sleeved cylinders but larger valves, light rods for the expected thrust, etc.  Sensible to retrofit cast engine beds, at which point quite a few other changes might be 'within the realm of contemplation' -- name me the first class of successful Berk with 69" drivers and better lead-truck design that comes to your mind, for example...

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