Railway Preservation News

Steam Speed Myths
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Author:  Alexander D. Mitchell IV [ Thu Aug 27, 2015 8:22 am ]
Post subject:  Re: Steam Speed Myths

Over on the Steam Railroading forum at TrainOrders, a few old heads are sharing similar legends on a thread about UP 844/3985 that doesn't, for once, descend into unilateral condemnation of the current UP steam program personnel......

Best/most "authoritative": UP's Bob Krieger claiming "I was the pilot engineer on 8444 when they went to Torrington WY for a centennial celebration and the mechanical department was operating the loco. We did a 38 second mile through the hole below Archer Hill leaving town."
That works out to 94.7368 mph, according to another poster there..........

Author:  kemcclure [ Thu Aug 27, 2015 9:39 am ]
Post subject:  Re: Steam Speed Myths

Robby Peartree wrote:
There are a couple of people with pictures of GCR 4960 doing 70 mph in the yard at the Grand Canyon.

Robby Peartree

Sounds like a dual-range speedometer to me. :-) They can make for neat pictures in that at low speeds they read 1/10 of the scale, ie; reading 10 is actually 1 mph, 20=2 mph, etc. At about 8 mph they switch back automatically to full-scale. So you can get photos of it reading "70" mph, but reality is 7 mph.

They are really handy for those instances where you need to maintain a slow, steady speed, like shoving humps and loading trains at those places that can load while the train is in motion.


Author:  Kelly Anderson [ Thu Aug 27, 2015 10:27 am ]
Post subject:  Re: Steam Speed Myths

Ted wrote:
Kelly Anderson wrote:
Since an N&W J with 70" drivers was clocked at 110 on a run while on loan to the PRR (unless that is a myth as well), I have no doubt that many of the 80" and higher drivered engines exceeded 100 MPH frequently, given the clear and smooth track to do so.

It requires more than just tall drivers to get over 100 mph. Balancing is the key. N&W was able to do that by restricting lateral movement of the drivers, which limited its ability to negotiate curves.

It also requires powerful boilers able to produce the horsepower needed to make the speed and a free flowing steam circuit that doesn't choke the power.

On the J, it is the lateral motion of the lead and trailing trucks that is stiff and limits its ability for negotiating tight curves. This due to the design decision to limit the amount of reciprocating balance, reducing vertical dynamic augment at the cost of increased longitudinal DA, causing the engine to be more prone to nosing left and right when going down the track.

But all that is off the track. My point was if the J can attain 110 MPH, then she is turning over at 528 RPM. and an 80" drivered engine would only be turning over at 462 RPM at the same speed, and with a longer wheelbase would be able to absorb greater errors in counterbalancing. In addition, engines such as the PRR E2 and T1 only had 26" piston stroke vs. the J's stroke of 32" so the piston speed at a given track speed would only be 71% of the N&W engine, which is huge.

Author:  Alexander D. Mitchell IV [ Thu Aug 27, 2015 10:33 am ]
Post subject:  Re: Steam Speed Myths

A long time ago, an engineering friend of mine calculated (in his head) the 528 RPM figure for the 70"-drivered N&W J at its (alleged) 110-mph, and then ran the numbers for what LNER A4 4468's 80-inch drivers would be at 126 mph.

As I recall, it was 529.4 rpm. Anyone wanna check his maths?

Author:  Alan Walker [ Thu Aug 27, 2015 11:50 am ]
Post subject:  Re: Steam Speed Myths

Alexander D. Mitchell IV wrote:
Anyone for 96-inch drivers? Bristol & Exeter broad-gauge 4-2-4 of 1853-54, recorded as doing 81.8 mph downgrade not long after construction.


Eight footers were not all that uncommon in the early days of British steam in their day. As I recall, there were two or three classes that used eight foot single axle drivers.

Author:  Ron Travis [ Thu Aug 27, 2015 1:25 pm ]
Post subject:  Re: Steam Speed Myths

I see no reason to conclude that this is a myth:

PLANT SYSTEM locomotive #111 recorded a famous speed record for the U.S Post Office in 1901. Without reviewing all my notes again, I am somewhat going by memory, but the record was claimed to be 120 mph, and verified to be 108 mph. Here is a photo of sister engine #110:

https://en.wikipedia.org/wiki/Plant_Sys ... o._110.jpg

Here is a link to the details. The image can be dragged to view all:

https://news.google.com/newspapers?id=2 ... %2C1051223

Author:  Overmod [ Thu Aug 27, 2015 1:45 pm ]
Post subject:  Re: Steam Speed Myths

There is much, much more to how fast a locomotive can operate effectively than its driver diameter or boiler capacity. No one so far has mentioned either vertical or lateral stability, where onset of dangerous resonant oscillation can occur in no more than a 2-3 mph increase. There are other considerations 'known to those skilled in the art' -- and all of them need to be satisfied for the locomotive to reach high speed, let alone be safely operated there.

Ross Rowland, among others, has some interesting stories of 'how fast' he has seen locomotives go. I had thought the peak speeds on NJT during some of the 614 excursions had been fully established, verified both with radar and from video analysis. I would note that a great many of the 4-8-4 locomotives could reach over 100 mph, but not get anywhere near 110.

ATSF 3463 has 84" drivers and a comparatively short stroke, and is clearly good for speeds of over 100 mph ... but not that much more than 100 mph, perhaps in the 110 peak range. Several late classes of ATSF 4-8-4s were likely to have been good for comparatively much more speed -- they had much better valves and passages, for example, and had the Wagner bypass valves to make power transitions, as well as slowing down from high speed, much less of an adventure. Even so, I think speeds much above, say, 115 mph are unlikely ... but perhaps we shall see when 2926 et al. are ready...

The S2 turbine was gear-ratio limited to not much more than 85 mph, if the PRR TE-speed graph I obtained from the Hagley is extrapolated to the point of maximum sustained steam generation. As noted, changing the effective gear ratio would have allowed a higher speed. But an actual inspection of the gearing arrangements involved will quickly show this NOT to be a trivial exercise, and a higher ratio would cause even worse starting problems -- not due to a lack of torque but longer duration of the steam 'slip' through the turbine and around the tips of the blades while its rotational speed is low.

The "record" for the S1 is almost certainly a fabrication, traceable to Arnold Haas (who is somewhat infamous for inflated speed claims elsewhere, particularly regarding NYC). The actual number is 142 mph (supposedly on the Trail Blazer in the latter half of the Forties). A moment's reflection will reveal that this is an English equivalent of a 'round number' in metric ... which of course PRR wouldn't use, but a railfan of German descent would. (It's also unlikely that the ride in the Trail Blazer cars would have been anything but wild at that speed, if we can believe a different story, about T1 high speed with PRR business cars riding much too roughly behind...)

As I have noted, the one place a duplex has undeniable advantage in high-speed running is at rotational speeds over 520 rpm or so. Alfred Bruce took the trouble to note personal experience with MILW A class (Atlantic with 84" drivers and low frontal area) at 128 mph; the T1, with arguably more capable valve gear and outside-bearing lead truck, could be run in the same range. It remains to be seen whether a T1 would physically reach that speed and be stable there; one should not believe 'speedometer' readings, though, as the Jones-Motrola speedometers only read up to 100 mph and I suspect will internally 'peg' not too much faster than that.

If I remember correctly, one of the CB&Q Hudsons was reliably clocked at 112.5 mph, which is on the ragged edge of what I would expect it to produce. I don't think there is even a remote chance of the Atlantic previously referred to coming anywhere near 125 mph -- there's no way to make the necessary steam, and the rotary valve system was not, to my knowledge, optimized for flow at high cyclic speeds, no matter how economically it may have metered steam at normal operating speeds. At least one PRR Atlantic (80" drivers and probably a better boiler) was tested with this valve system, and someone here might be able to locate the actual test results and cards.

The locomotive that, to me, is clearly the most capable of reaching extreme steam speed would be the late version of the PRR V1 turbine, with mechanical drive (through the Bowes drive) to multiple quill-drive axles. The Bowes drive would have permitted a higher gear ratio to be practically used for starting, the high-speed slip issues with duplexes would not be present, and there are no 'hard' issues in the suspension that could not be addressed with better springing, snubbing, and damping ... in my opinion. The actual achievable horsepower out of this locomotive was boiler-limited (it used a slightly-modified Q2 boiler, almost certainly capable of providing steam for 8000 turbine HP at the turbines' more effective degree of compounding) and, even though the water rate would have been as hellacious as you'd expect 8000 steam HP to involve, it would still produce the needed power at speed to reach well over 130 mph. (Whether PRR, or anyone else, needed a high-horsepower locomotive that would run at those speeds, in the 1940s or indeed ever, is another discussion entirely!)

Personally, I have always wondered whether that locomotive design we see in some shots of Loewy's office in New York was intended to be buildable ... and what kind of speed it would have produced. :-}

Author:  Overmod [ Thu Aug 27, 2015 2:25 pm ]
Post subject:  Re: Steam Speed Myths

One other peripheral point: High driving wheels were often used for a purpose other than keeping machinery speeds low for high speed. A good example provided to me was Gölsdorf's famous Austrian 2-6-4 class. Another interesting one was that 'fastest locomotive in the world' design for Atlantic City Railroad 1027, which required high drivers because of hard limits on how quickly Vauclain compounding could extract energy from supplied steam. (It might be interesting to compare the 1904 'record' run made with a P&R Atlantic not too different from the one pictured, which supposedly reached a peak speed of "115 mph"...


These slide valves could have a large number of "D" passages arranged like the strips in a magnetic chuck, so a comparatively small movement of the valve would control a large port area with very quick effective unshrouding on admission, and large volume-handling capability for exhaust. It would also be possible (on an engine this size) to use riding cutoff to give very effective timing control without reducing port openings (as a radial gear would do) - although I don't know whether the P&R locomotive in question used that.

It is certain that any high-speed exploits of locomotives in this period would require extremely good control over timing, clear exhaust passage and low back pressure, and a careful balance between too much steam demand (which would lead to priming before it reached anything like the boiler grate limit) and too much expansion (which would lead to excessive nucleate condensation and probably water in the cylinders).

I must confess that I have always thought the Plant System 'record' of 120 mph (and the 'verified' 108 mph) to be something of an old woves' tale. If you compare the Plant System locomotive, and the trackwork it ran over, with the equivalent on a high-speed railroad running 4-6-0s like LS&MS, even a bravura performance in locomotive handling under the threat of 'losing the mail contract' (presumably with trailing load limited to that which the Postal Department would accept as 'carrying the mail' or what would keep the engine steady, whichever is less) seems unlikely to produce those speeds. Remember this is a 4-6-0 without proper cross-balancing, and no radial buffer ... imagine the motion experienced at the cab.

Author:  p51 [ Thu Aug 27, 2015 2:27 pm ]
Post subject:  Re: Steam Speed Myths

There will always be claims of 'insane' speeds with steam
The British A4 Pacific, "Mallard" made what is generally considered the world's record speed for any manned locomotive, steam-propelled, on rails....
But, hold on!
A German streamlined 4-6-4 made just shy of 125 on level track before the British attempt. Unlike Mallard, the engine was just fine after its run. There are those to consider Germany as the holder of the steam speed record as Mallard made her record run on a substantial downgrade (and rattled herself apart to a degree, so much so she had to be removed from the train at the next station, something the RR was ready for and required a completed shopping afterward). There are stories that another German locomotive went way beyond Mallard's speed on the famous run, but like all other claims, it's never been documented well enough to be considered proven.
A French engineer was riding with the MILW through rural Wisconsin and noted speeds that astounded him. He was told by the crews that in the flatlands, they regularly exceeded 125.
Management of American RRs routinely gave a 'nod and wink' to crews who busted speed limits, to meet schedules, just as long as no accident occurred. I think it's reasonable to assume that any of the examples cited so far could have broken Mallard's record, were it not for:
1. Fear of getting in trouble with management for breaking the rules
2. No concrete support for said speeds
I've always wondered why no American RR made an official attempt at the British record. There were several locomotives and routes where such an attempt could have been made.

Author:  Overmod [ Thu Aug 27, 2015 2:54 pm ]
Post subject:  Re: Steam Speed Myths

"There are those to consider Germany as the holder of the steam speed record as Mallard made her record run on a substantial downgrade (and rattled herself apart to a degree, so much so she had to be removed from the train at the next station, something the RR was ready for and required a completed shopping afterward)"

In all fairness to Mallard, the damage during the 'record run' is nowhere near as serious as this makes out. The design of the bearing in the inside main-rod big end was insufficient (and known at the time to be inadequate) and the inertial whip in the conjugation levers driving the inside valve led to excessive load on that bearing. The engine was taken off the train more for safety reasons than 'failure' (and in fact, if I remember correctly, it ran to the shop under its own steam) and a comparatively simple redesign of the big end 'solved' the problem. (Note that Gresley himself accepted that the "126 mph" figure was a hydraulic artifact and only used 125 mph as the 'record' achievement).

The test of the German locomotive was stopped at the magic 200 kph, and it is indeed interesting to speculate whether one of the class 05s could have been run to a speed higher than Mallard's. Remember that the class 05 boiler had some built-in insufficiencies, and the firebox arrangements in particular were pathetic by American design standards, and it might be observed that in all the ensuing year between Mallard's run and the outbreak of the War there was no faster German test (and I strongly believe that if there were, propaganda would have trumpeted it!)

The 'not documented, not done' railfan standard regarding the legitimacy of high-speed steam operation does lead me to wonder something. Could timed or measured observations of very high speed be current in the 'photo trading' community, but be relatively unknown to outsiders?

Author:  Dave Stephenson [ Thu Aug 27, 2015 3:13 pm ]
Post subject:  Re: Steam Speed Myths

The speeds made by N&W 610 on PRR are not myths. Using information from N&WHS Archives files, we can identify three high speed runs:

12/7/44 - 110 mph, train 71, The Admiral, westbound Crestline-Chicago, 15 cars
12/8/44 - 111 mph, train 57, Liberty Limited, westbound Crestline-Chicago, 11 cars
12/8/44 - 109 mph, train 28, Broadway Limited, eastbound Chicago-Crestline, 13 cars

The details of these tests were covered in the PRRT&HS magazine, The Keystone, and NWHS magazine, The Arrow.

Author:  p51 [ Thu Aug 27, 2015 6:17 pm ]
Post subject:  Re: Steam Speed Myths

Does anyone have a clue what the documented (not anecdotal) fastest steam locomotive run was in the US?

Author:  Overmod [ Thu Aug 27, 2015 7:31 pm ]
Post subject:  Re: Steam Speed Myths

I have a strong suspicion that the answer to this will vary depending on what "documentation" is considered sufficient.

Author:  Les Beckman [ Thu Aug 27, 2015 7:47 pm ]
Post subject:  Re: Steam Speed Myths

The Milwaukee Road had a sign on a main line curve between Chicago and Milwaukee that read "SLOW TO 90"! Not sure when that particular sign was installed, nor whether it was meant for the modern 4-4-2's or the Milwaukee's 4-6-4 Baltics. I recall seeing a photo of the sign, but have never heard of documentation as to the operation of the CMStP&P steamers on this segment of the railroad. Was the sign a myth?


Author:  CREEPING DEATH [ Thu Aug 27, 2015 8:02 pm ]
Post subject:  Re: Steam Speed Myths

Les Beckman wrote:
The Milwaukee Road had a sign on a main line curve between Chicago and Milwaukee that read "SLOW TO 90"! Not sure when that particular sign was installed, nor whether it was meant for the modern 4-4-2's or the Milwaukee's 4-6-4 Baltics. I recall seeing a photo of the sign, but have never heard of documentation as to the operation of the CMStP&P steamers on this segment of the railroad. Was the sign a myth?


I understand it was, REDUCE TO 90 - but I may be wrong.


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