Steam & Excursion > largest steam engines in the US

Compiled from steamlocomotive.com

I find it interesting why the Big Boy is said to be the largest steam engine when these stats show otherwise.

Wheel Arrangement: 2-6-6-6 Allegheny (Chesapeake & Ohio)
Length: 125' - 8"
Drivers: 67" dia.
Weight on Drivers: 504,010 lbs
Locomotive Weight: 775,330 lbs
Tender Weight: 431,710 lbs
Locomotive & Tender Weight: 1,207,040 lbs
Grate Area: 135 sq ft
Cylinders: (4) 22.5" dia. x 33" stroke
Boiler Pressure: 260 psi
Tractive Effort: 110,200 lbs
Water: 25,000 gallons
Coal: 25 tons


Wheel Arrangement: 4-8-8-4 Big Boy (Union Pacific)
Length: 132’-10”
Drivers: 68" dia.
Weight on Drivers: 545,200 lbs (second class)
Locomotive Weight: 772,250 lbs
Tender Weight: 436,500 lbs
Locomotive & Tender Weight: 1,208,750 lbs
Grate Area: 150 sq ft
Cylinders: (4) 23.75" dia. x 32" stroke
Boiler Pressure: 300 psi
Tractive Effort: 135,000 lbs

Wheel Arrangement: 2-8-8-4 Yellowstone (Duluth, Missabe & Iron Range)
Length: 125’-0”
Drivers: 63" dia.
Weight on Drivers: 564,974 lbs (M-4)
Locomotive Weight: 699,700 lbs
Tender Weight: 438,335 lbs
Locomotive & Tender Weight: 1,138,035 lbs
Grate Area: 125 sq ft
Cylinders: (4) 26" dia. x 32" stroke
Boiler Pressure: 240 psi
Tractive Effort: 140,000 lbs

Wheel Arrangement: 2-6-6-4 (Norfolk and Western)
Length: 121' - 9 1/4"
Drivers: 70" dia
Weight on Drivers: 432,350 lbs.
Locomotive Weight: 573,000 lbs.
Tender Weight: 378,600 lbs. (loaded)
Locomotive & Tender Weight: 951,600 lbs
Grate Area: 122 sq. ft.
Cylinders: (4) 24" (dia) x 30" (stroke)
Boiler Pressure: 300 psi
Tractive Effort: 114,000 lbs
Maximum HP: 6,300 @ 45 mph Tender Capacity:
Water: 22,000 gals.
Coal: 30 tons

Wheel Arrangement: 2-8-8-2 Y6b class (Norfolk & Western)
Length: 114' - 10 1/2"
Drivers: 58" dia.
Weight on Drivers: 522,850 lbs
Locomotive Weight: 582,900 lbs
Tender Weight: 378,600 lbs
Locomotive & Tender Weight: 961,500 lbs
Cylinders: 25" x 32" (HP)
39" x 32" (LP)
Boiler Pressure: 300 psi
Tractive Effort: 152,206 lbs (s)
126,838 lbs (c) lbs
Water: 22,000 gals.
Coal: 30 tons

Define largest. By the stats you posted it is the longest and has the heaviest overall weight.

You do have a point as out of these the big boys are the heaviest. "Largest" has different meanings, but I like to look at how much weight is on the drivers and the tractive effort.
I do wonder why the big boy pistons were not larger in diameter to create more power. Or would that require a larger boiler and/or firebox?

The C&O 2-6-6-6 outweighs the big boy.

frosty Wrote:

> Compiled from steamlocomotive.com
>
> I find it interesting why the Big Boy is said to
> be the largest steam engine when these stats show
> otherwise.

The page where Wes Barris lays all this out is http://www.steamlocomotive.com/misc/largest.shtml

It includes a paragraph with the heading "But I Thought the Big Boy was the Largest!"

tomstp Wrote:
-------------------------------------------------------
> The C&O 2-6-6-6 outweighs the big boy.

Entirely right...and they had room for growth (higher boiler pressure= higher t.e.), given their veryf high factor of adhesion.
UP was justifiably proud of the 4000 class as they combined power with some degree of speed for a freight locomotive. Those
DM&IR Yellowstones were monster machines, but with 63" drivers, were still a drag engine.

Tom

Since there is so much dreaming going on in these forums, picture all of those monsters lined up side by side in a huge yard like Collinwood once was. All in steam.....Now there's a dream and we would all not care which one is "biggest."

Wes Barris has to rely on information from others for some of the stats on his site, so the quality and accuracy of the different pieces is extremely variable. Let the reader beware!! For example:

1. PRR S1 7200 DBHP - This figure has never been documented AFAIK. 1,200 tons at 100 MPH doesn't require anywhere near this amount of DBHP. It's closer to 4,000 DBHP, which the S1 could certainly manage.

2. PRR S2 - The reading should be shaft HP not IHP. The S2 didn't have any cylinders, so cylinder HP/IHP is not applicable.

3. PRR T1 - 6,110 DBHP is actually locomotive DBHP measured at the rear of the loco on the Altoona test plant, not at the rear of the tender. Further, IHP is always measured in the cylinders without consideration for the tender, locomotive mechanical and rolling resistance, and air resistance.

4. SP GS4 - There was an article in the June 1977 issue of Trains regarding 4449's performance. 5,500 is more likely IHP not DBHP. Bill Withuhn explains this in some detail (pg25).

5. N&W J - 6000 IHP?? No record of IHP has been found at this point. N&W didn't bother with this figure very much because DBHP (at the rear of the tender) is what moved the goods.

Most Powerful locomotive

1. C&O H8 - 7,500 DBHP at 40 mph. Actually this is a peak reading of 7,498 at 46 mph. See Gene Huddleston's book, The Allegheny, Lima's Finest, page 204 for the graph. Sustained DBHP is about 6,600 DBHP, more than enough to put the H8 in first place. Peak values are pretty meaningless because of extenuating circumstances encountered during the test.

2. N&W A - The 6,800 IHP at 38 MPH sounds like it's from Trains, Nov 1991. This figure is incorrect. No such value was ever recorded for the A, and the estimate in Trains was based on several errors of fact. Simply not true, and N&W made no such claim.

3. N&W Y6b - The 5,600 DBHP figure is operating in compound, not simple, and not with booster. That is the Y6/Y6a/Y6b's capability in normal service, any time. The so-called booster was used at about 10-15 mph for additional TE. Simple operation was sustainable only to about 10 mph at the most. See the March/April 2006 issue of NWHS magazine The Arrow for a description of Y6 operation and DBHP.

Caveat lector!!!

I know what this is going to take. Its going to take a single, male railfan to hit one of those multi-state lotteries ... then get caught up in this debate (or mabye the other way 'round).

Would anyone disagree that a budgeet of $50 million over five years could get a Yellowstone, a Big Boy and an Allegheny restored *and* operated in a head-to-head performance test?

* JB *

My guess is that the three Space Shuttle main engines, dimensionally smaller than the biggest steam locomotives, and weighing much much less, have the highest power to weight ratio of any steam engine that ever existed.

Might have something to do with UP's PR department. They were pretty open about their power and a lot of media hype was generated about the "Big Boy" being the largest, biggest, etc.., etc... Can't say if C&O ever tried to do that.

lurchdel Wrote:
-------------------------------------------------------
> My guess is that the three Space Shuttle main
> engines, dimensionally smaller than the biggest
> steam locomotives, and weighing much much less,
> have the highest power to weight ratio of any
> steam engine that ever existed.


http://www.boeing.com/defense-space/space/propul/SSME.html
From the "incredible facts" page (via link at bottom from link above):

- Even though Rocketdyne's SSME weighs one-seventh as much as a locomotive engine, its high-pressure fuel pump alone delivers as much horsepower as 28 locomotives, while its high-pressure oxidizer pump delivers the equivalent horsepower for 11 more.

* * *

Still, with the temperature in the cumbustion chamber reaching 6000+ deg F, a rearward facing engine added to the head of the consist would tend to incinerate trailing equipment. This tendency would limit the Block II S.S.M.E.'s suitability in railroad service.

* JB *

djansson Wrote:
-------------------------------------------------------
> Can't say if C&O ever tried to do that.

The H8's did appear in some publications. IIRC, some were commissioned by the C&O, others by Lima. Another factor: C&O used their H8's in drag coal service, with about half of the 60 modified for passenger work.

* Jb *

UP stated that the challenger was the largest operating steam engine in the world at the same time N&W 2-6-6-4 was operating. I think the N&W engine is larger.

about the 2-6-6-4
Locomotive Weight: 573,000 lbs.
Tender Weight: 378,600 lbs. (loaded)
Locomotive & Tender Weight: 951,600 lbs
Tractive Effort: 114,000 lbs

and from http://www.uprr.com/aboutup/excurs/up3985.shtml
we have for the challenger:
Engine Weight: 627,900 lbs
Tender Weight: 446,000 lbs
Total weight: 1,073,900 lbs
Tractive Effort: 97,350 lbs

So the challenger weighs more, but the 2-6-6-4 has more tractive effort

Regarding locomotive weights, I believe it needs to be remembered that these are all "official" weights, if I'm not mistaken generally determined with approximately 2/3 glass of water in boiler. These weights were important because locomotive crews were paid, in part, upon the basis of weight on drivers.

The J.W. Hunt Co. of New York served as contracted inspectors of Union Pacific locomotive construction, at least for Alco work. They determined the official weight in concert with Alco. These weights were utilized in railroad pay scale work.

I'm not so sure the locos didn't all weigh just a little more than the railroads said they did.

Piston size on Big Boy was based upon obtaining best proportions necessary to maintain speed with tonnage trains. The railroad was far less interested in what a 4000 would start than it was with speed over the road considering the "design tonnage." Big cylinders equal high starting TE, but smaller cylinders equate to horsepower at speed. UP, working with Alco, determined what they wanted in the sense of overall performance.

By the way, all Big Boys were delivered with train steam heating equipment, as were all 4-6-6-4's. Even UP's 4-12-2's were so equipped from new!

John

This is v-e-r-y interesting. And valuable inforamtion! However, I would love to have any one of these Locomotives in my backyard! Or see and film any one of them roar-en' down the track! My favorite of all I have ever seen, is the Union Pacific "Big Boy", 4006.....VERNON

Trains printed a decent article on same subject few years back. Anyone recall specific issue for our colleague here? Anyway, good article. Mirrored much of above conversation.

Keep your Crown Sheet wet.

A few years ago, when I visited the Lake Superior Museum of Transportation in Duluth, I could push a button and the drivers of a DM & IR Yellowstone would turn! In addition to this locomotive, Yellowstones are also preserved in Two Harbors & Proctor.

Dave

How about LARGEST in terms of number of cylinders and drive wheels ??

The "MATT SHAY" on the ERIE Railroad was a monstrous '2-8-8-8-2' and SIX cylinders.

So that's SIX cylinders and 24 drive wheels !!

What say thou ??

KRK