Steam & Excursion > Fastest steam Locomotive: Take 2.

I missed the earlier thread on ‘fastest steam locomotive’. This had a lot of fun anecdotes, though little hard data. Further, the locos I believe have by far the best claim to “fastest ever’- the MILW F7s and As - got little mention! In part it’s a definition thing. The usual one is ‘what holds the speed record?’ and here as far as hard data goes, the fastest are LNER Mallard and the German O5 at ca. 125mph. I will go on to argue this is near the limit of the possible. My definition would be ‘what regularly ran fastest in daily service?’ This, as far as I can tell is a two horse race between the MILW types, scheduled to run at 100mph over long distances four times a day. You can’t average 81 mph from Sparta to Portage, uphill start and slow through Tunnel City without then reaching 100mph quickly and staying there whenever possible. Speed often flat lined at 100mph south of Milwaukee from around Lake to Forest Glen. There is nothing else approaching this anywhere in the world with steam.

So what made the MILW types the fastest? Nothing to do with design really, I say, They basically just represent 1930s best US practice though the 84” drivers will reduce piston speeds and maintenance costs a bit. An NYC Hudson was slipped up to 164mph, so no problems with the robustness of US motions at speed. Rather, high speed is really about two things, HP/ton and help from gravity. An NYC Hudson could run a nine car Hiawatha (similar weight to the loco) at 100mph most of the way from Toledo to Elkhart. But fewer, heavier, lower HP/ton trains made more sense. PSR? Plus ça change.

To estimate HP/ton needed, we need to know the ball park for locomotive and coach resistances. For US types, the train as a whole needs 3.5-4 HP/ton to maintain 100 mph on the level. The lighter trains in Europe need more.  So to maintain 100mph, a Hiawatha of 825 tons total, needs about 3200 cylinder HP on the level; a 1470 total tons T1 hauled Trailblazer about 5400. It would take forever to accelerate to 100mph at these powers, so you need to add 1000HP to these figures and indeed the AAR concluded in 1938 that you needed 6500HP to run 1000 ton trains at 100mph.
  
 It is well recorded that both T1s and Niagaras could achieve 6500+ cylinder HP. This is their extreme limit. Beware. These figures are far from what you can expect in normal service (coal consumption, boiler maintenance costs etc). The NYC said that ‘above average’ service operation for a Niagara was 4000HP.  Short term higher peaks are possible.  Analysis of Hiawatha running shows the F7s would develop about 4000 IHP when accelerating, then back to ‘comfort zone’ 3000-3500HP once up to 100mph. On one recorded run, an F7 ran briefly up to 113 mph. This needed about 5000HP, also needed for the reported 5 miles at 120 mph. But these should be viewed as short term stunts rather than daily capability. Other latter day 4-6-4s should show similar behavior. The best 4-8-4s would give around 4000HP in normal hard work, high 4000s for peak efforts and nearly 6000 if showing off.

Gravity helps – about 5.3HP/ton at 100mph on a 1% gradient, half that on 0.5% or at 50mph. This makes high speeds a whole lot easier.  On a 1% downgrade, just take off the brakes and you’ll get to 100mph. The ATSF had long steep and quite straight gradients west of ABQ, where the problem is I suspect not getting to high speed but going too fast! On the gentle gradients west of the Missouri  to the Rockies  found on the UP and ATSF, a UP 4-8-4 worked a 1000 ton  AAR test train to 100mph going east working at 5500HP, but couldn’t make 100 mph uphill. Mallard had a 0.5% downgrade.

The PRR west of Crestline is straight and pretty flat, enough shallow gradients to help a T1 Trailblazer up to 100mph. 69 miles at 100mph for a T1 is quite realistic. 120mph requires nearly 6HP/ton and could only be achieved with a lightweight train, e.g. down the 0.25% from Bucyrus to Upper Sandusky.  Claims that T1s ran in excess of 130 mph on this line are fantasies. Resistance at even 130mph is of the order of 7HP/ton, so a light train grossing 1100 tons would need 7700 cylinder HP. You could get about 1.7 HP/ton benefit from gravity on the stretch above, but this would still leave you needing 5800HP - add in another 1000hp to get fast acceleration, and you are way beyond reason. This kind of logic precludes 130 mph+ for any steam train on relatively shallow gradients.

So, how fast you go depends on HP/ton, and gradient; and of course if scheduled, an infrastructure and signalling upgraded to suit 

Hope this analysis is of interest. Any further data much appreciated.
 

Yeah, the mileage needed to accelerate the train --
that's another of the things fans don't consider.
That's why the story of the N&W 4-8-4
doing 110 mph is unlikely.

West from milepost 542, SFe has 16 miles
of straight track averaging 1.1% down.
Wonder how dangerous a record attempt
there would be. (No sharp curves before the start --
they could be doing at least 80 when they start
down the straightaway.)



Edited 1 time(s). Last edit at 05/20/22 15:44 by timz.

Except for the fact that J #610 was used on the Pennsy for tests, and the 110 - 111 MPH was repeated not once but three times with trains of 11 to 15 cars and documented all three times.

Show the documentation.

timz Wrote:
-------------------------------------------------------
> Show the documentation.

I seem to remember that Ed King has such "documentation", and has published in his book about the N&W J Class locomotives. Also "Feltenhill" has such "documentation" from the PRR Historical & Technical Society.

From Steamlocomotives.com

Rhodes and Stephenson described in detail the conclusions drawn by the Pennsylvania Railroad after running the 610 at the point of a month of revenue trains between Crestline, Ohio and Chicago, Ill from 5 December 1944 and 3 January 1945. The first big surprise for the Pennsy was how readily the J ran for dozens of miles at speeds over 90 mph (145 kph). Three runs pulling between 11 and 15 cars each hit speeds of 110-111 mph (177-.179 kph).
Other PRR impressions: The J rode more smoothly than any of the PRR's locomotives save the unique S1 6-4-4-6. Relatively low drivers meant less slipping on starts and higher acceleration. Its larger grate allowed it to steamed better, even on poor coal, than the T1. Together with large valves and long travel, the engine's design made it possible "to maintain a uniform steam pressure at high speed."
 

Didn't the Santa Fe have stretches where the passenger speed limit in the steam days was 100? Remember the famous "reduce speed to 90" restriction for some curve? I thought the 2900's and 3460 class Hudsons regularly ran 100. Anyone else remember?

East of LaJunta CO comes to mind.

SFe timetables allowed several steam classes
to do 100. But someone pointed out that many?
most? of them lacked ATS, so officially they
weren't supposed to exceed 79.99 mph, after 1950
or whenever the deadline was. (No mention of that
in the timetable.)



Edited 1 time(s). Last edit at 05/20/22 18:16 by timz.

I read somewhere that an SP GS4, could take a 2200 ton passenger train and accelerate it to 60 MPH in one mile  

That's true, long as they're on a steep enough descent. 1.5%, maybe.

Santa Fe had a 110 mph speed limit in the San Joaquin valley. Not sure if it applied to steam. 

As I recall, timetable limit on the Valley Div was never more than 95.

Kind of off the subject but applicable, used to be fun in teaching classes where vehicle drives were involved and people
would got all goo goo eyed over the fact that the horsepower required for speed wasn't all that high. I would then procede
to discuss the implications of the equal sign! How long did you say you wanted to allow for acceleration?

Out

Santa Fe didn't have speed limits until after the War. Even the ICC made note of this in an accident report at Gallup, 1943

 https://planeandtrainwrecks.com/Document?db=DOT-RAILROAD&query=(select+2677) 

What Santa Fe did have is restrictions on its locomotives, the maximum being 100 mph for certain Diesels, 4-6-4s, and 4-4-2s.

Eventually (1945, '46 ?) ATSF established 100 mph as the maximum operating speed, reduced to 90 mph in 1958.

The ICC ruling of speeds imposed by signaling was proposed in 1946 and made final in 1947, with a 5 year grace period.

Thanks to all for this interest shown. To timz, the N&W J could make 110 mph at Upper Sandusky passing Bucyrus at 70 mph ( don't know what the actual; limit was) on 5000-5500 HP, well within its compass, though it's obviously not an ideal high speeds machine with 70" drivers.
And, simply by dint of taking off the brakes in Kingman, and a few puffs to the top of the Downgrade, I reckon  3463+1000 tons would be up to 130mph by Yucca, and if it stayed on the curves thereafter (!) might exceed 135mph before Topock. Not advisable.

Hell, that ain't nuthin.  I remember taking 1522 and our support cars from St. Louis Union station out to the Museum of Transportation one time, 16 miles, in six minutes.  Backing up.

Frisco1522 Wrote:
-------------------------------------------------------
> Hell, that ain't nuthin.  I remember taking 1522
> and our support cars from St. Louis Union station
> out to the Museum of Transportation one time, 16
> miles, in six minutes.  Backing up.

...with the gear in the corner...

Klondyke Wrote:
-----------------------
> the N&W J could make 110 mph at Upper Sandusky
> passing Bucyrus at 70 mph 

You must be assuming 5000+ dbhp from the
engine at 90-100 mph. N&W only claimed
3300 dbhp at 90 and 2900 at 100, for the
engine as built.

Bucyrus to Upper Sandusky is 16.8 miles,
so acceleration from 70 to 110 in that
distance would require 2000 hp average
just to overcome inertia, on top of whatever
is needed to pull the train.

Yup, it's that darn equals sign, once you pull the train down the level, then what.

Out