# Fast Steam Engines



## jimben (Jun 27, 2018)

I read the Pennsylvania T1 Duplex steam engines went 125 MPH with a unrecorded peak of 140 MPH. The had to be blinding speed back in 1938. What about steam engine top speed around 1900?

I also read the Union Pacific Big Boy 4-8-8-4 steam engine could produce 6500 horsepower. I believe the most powerful diesel is about 6000 horsepower, but after conversion from diesel to electric about 4000 horsepower is available at the wheels. So, steam engines made more power at the wheels? I also believe big steam engines weighs more than diesel producing more traction going up grades like in the Rocky mountains.


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## mesenteria (Oct 29, 2015)

There is a lot of well-intentioned hype over the real capabilities of steam locomotives, virtually none of it true.

The harsh reality about steam locomotives is that they have a lot of heavy reciprocating components that are impossible to balance with the forces being applied to them in three planes. One result is that they are hard to lubricate. The faster the parts move, the worse it gets. In order to achieve the horsepower needed to get 800 tons of locomotive, tender, and other trailing tonnage up beyond 79 mph, the top speed permitted in most places for passenger service, the boilers had to provide a lot of steam readily, but also HOT steam, and it was dry the way it was made hot. In other words, it needed high pressure steam that was superheated. To get things to work in those circumstances, you needed to control tribology, that being the way lubricants work in those conditions. Where the legendary super-power steamers often ran into trouble was there...piston and piston valve lubrication. For example, the N&W Class J was trialed by the Pennsy, who ran it up to just over 100 mph and promptly found they had burned one of the valves.

The various valve mechanisms used on the T1 Duplex was between Walschaerts (at least one locomotive) and Franklin poppet valves. The T1 tended to spin when the throttle was opened too suddenly, and this was a problem attributed finally to the poppet valves. The T1 also spun its front engine at high speeds when it road light for a second or two on slightly uneven rail heights, and if it spun at speeds much higher than about 80 mph there was the risk of valve gear failure (which is why they removed the Franklin on one trail version to fit it with Walschaerts.


There is an anecdotal story printed in a August 1993 issue of Trains magazine where a crew that had been slated for an F unit ride were instead directed over to the ready track where a dusty, unpretty T1 had been hostled for use. The guys were in the common nice clothes used in diesel cabs, and were less than impressed when they had to climb into the cab of the decrepit T1 and found they had to clean everything. Even the shroud between the tender and the cab was in tatters. They had to hose down the entire cab.


Long story short, they were late by nine minutes at the start of their last leg of about 31 miles. They made up those nine minutes. When they were dismounting, the yardmaster informed them that the DS wanted to see them in his office. Figuring they were in the caca, they trudged off.

The DS stated to them that, by his math, the observers had timed them taking 17 minutes to cover 27 miles and that was from a stop!! He warned them to never pull that stunt again. Then he grinned and said, "Good job, boys." On that leg, the fireman had noted that the needle on the speedometer had stopped moving beyond 120 mph.


So....where do we go from there? There are stories, and there are harsh realities that the foreman of locomotives has to deal with if he wants to keep his job. The road foreman doesn't want to be fixing track unnecessarily because of pounded rails, and you don't want derailed passenger trains that are being bounced off the rails due to excessive speeds. Time did have to be made up on occasion, but there were speed limits with federally imposed fines. The Fort Wayne division, for example, had a strict passenger speed limit. In light of all useful and available information from that time, it is highly unlikely an American-made steamer ever exceeded 120 mph, and only got there in exceptional circumstances where the locomotive was free-steaming and in good condition, as was the trackage, and where people were willing to look the other way.


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## mesenteria (Oct 29, 2015)

jimben said:


> ...
> 
> So, steam engines made more power at the wheels? I also believe big steam engines weighs more than diesel producing more traction going up grades like in the Rocky mountains.


Generally, across the various types of locomotives, the strongest pullers were the electrics. The Penny's GG1 was prodigious in its ability to get heavy trains up to speed.

Generally, steam locomotives can pull a train they can't lift, and diesels can lift trains they can't pull.

Confused? Diesels mostly have all axles driven, so whatever their weight, they can apply most of their generated tractive power to the rails. Steamers have trailer and engine trucks that support cabs and pilots. So, steamers only have limited weight to bear on the rails for tractive purposes. They'll spin more readily, but they also don't produce much horsepower at low speeds.


Steamers generate their maximum horsepower when their running gear is cycling near 4 times per second. Diesels generate horsepower at 'zero' because their diesel engines are producing it...they're running! So, a diesel can 'lift' a heavy train with its 150K lbs of tractive effort where a steamer with the same horsepower can't generate that tractive effort after 40 mph when its boiler is applying the most horsepower. That is why, if a steamer can lift its trailing tonnage and accelerate it on the grade, and if it reaches the point where the cyclic rate of steam thrust is reaching 3.5-4.5 per second, its horsepower begins to come into its own. The diesel, which had no trouble accelerating that same tonnage from 'zero', is still producing the same horsepower...no more. So diesels reach a maximum speed that, with their typical gearing, limits them to speeds less than 60 mph...ish.


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## ebtnut (Mar 9, 2017)

This is the high speed record for steam. This from Wiki: "The documented highest speed for steam was set in England. Mallard is the holder of the world speed record for steam locomotives at 126 mph (203 km/h). The record was achieved on 3 July 1938 on the slight downward grade of Stoke Bank south of Grantham on the East Coast Main Line, and the highest speed was recorded at milepost 90¼, between Little Bytham and Essendine. It broke the 1936 German (DRG Class 05) 002's record of 124.5 mph (200.4 km/h). The record attempt was carried out during the trials of a new quick-acting brake (the Westinghouse "QSA" brake).

Mallard was a very good vehicle for such an endeavour. The A4 class was designed for sustained 100+ mph (160+ km/h) running, and Mallard was one of a few of the class that were built with a double chimney and double Kylchap blastpipe, which made for improved draughting and better exhaust flow at speed. (The remainder of the class were retro-fitted in the late 1950s.) The A4's three-cylinder design made for stability at speed, and the large 6 ft 8 in (2.03 m) driving wheels meant that the maximum revolutions per minute (529.4/min at 126 mph) was within the capabilities of the technology of the day. Mallard was four months old, meaning that it was sufficiently broken-in to run freely, but not overly worn. Selected to crew the locomotive on its record attempt were driver Joseph Duddington (a man renowned within the LNER for taking calculated risks) and fireman Thomas Bray."

Mallard is preserved in a museum, and had been opearable a few years ago.


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## Lee Willis (Jan 1, 2014)

Mallard and the A4s were fast locos. Really exceptional - just about all Gresley-designed steamers were.

Many people think several American steamers could have gone faster if given the chance to make a high speed run like Gresley's Mallard did. Among locos often mentioned are the T1, and the N&W J, and Santa Fe's and Milwaukee Roads Big Hudsons. I tend to think any of the four could have done that back when they were in service, if their owners had made a real effort. 

The steam loco with the highest potential speed was a single French 2-4-1 a modified by Andre Chapelon, "The french genius of steam." He designed the standard 2-4-1 and other locos for the French railroads. Basically he hot-rodded one of his 2-4-1 into a 2-4-2 (what we would call a 4-8-4). It was a bit smaller than most American Northerns, but had over 5300 HP. I doubt it could have done 145 mph but I think it could have done 135. But, like those four American locos and their owners, he never got the chance to really try to loco out, so we will never know. 

The Coalition for Sustainable Rail (an organization I support with contributions each year) has bought the old ATSF Hudson 3463, and now that a protracted legal battle has been won over actually taking possession of it, has plans to rebuild and tweek it slightly in hopes to establish a new land speed record for steam with it. I think they have a 50/50 chance of doing it.


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## gunrunnerjohn (Nov 10, 2010)

The FEF3 was supposedly designed to run up to 120 MPH, but I don't think it got there, but they did run them over 100 MPH.


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## rogruth (Mar 6, 2012)

Where will Sustainable Rail try to set a new record?
Just finding a place could lead to more litigation.


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## Nikola (Jun 11, 2012)

I wonder what a hot-rodded steam engine could do on today's welded, concrete-tied, laser-straight heavy weight rail.


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## Fire21 (Mar 9, 2014)

mesenteria said:


> The diesel, which had no trouble accelerating that same tonnage from 'zero', is still producing the same horsepower...no more.  So diesels reach a maximum speed that, with their typical gearing, limits them to speeds less than 60 mph...ish.


I'm certainly not a diesel engine designer nor even a diesel mechanic, but in internal combustion engines, HP increases with RPM up to a point. That point depends on valve timing, cam lift and duration, fuel injection timing and probably some other factors.

As the diesel loco accelerates, the throttle is advanced and the engine speeds up. Although the RPM range for large diesels is pretty narrow (250-maybe 1200), the HP does increase from idle, which is minimum HP, to a point of maximum HP somewhere in that RPM range. To say that the engine "is still producing the same horsepower...no more" seems to me to be a false statement.

Please correct me if I'm wrong. It's happened before! Thanks. :smilie_daumenpos:


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## Magic (Jan 28, 2014)

Fire, that is true in say a truck but in a locomotive the diesel is running at a set RPM all the time.
It's the generator that produces the power not the diesel and it's the generator that is throttled up.

The diesel will go from idle to a set RPM when the generator needs it.
A very simple explanation of a complex operation.

Magic


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## gunrunnerjohn (Nov 10, 2010)

Well, the diesel is spinning the generator, so it's the diesel that is supplying the power. However, you're right about the power. For units supplying HEP, the prime mover usually runs in a fairly narrow RPM range, and it just uses more fuel when there's a bigger load. 

Think of your standby home generator, it runs at a constant speed, but it uses a lot more gas when you put a heavy electrical load on it, then the generator gets a lot harder to turn, hence more power needed to do the job.


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## Fire21 (Mar 9, 2014)

So when the engineer notches up the throttle, he's just adding fuel to get more power, and the engine is remaining at a relatively steady RPM? That doesn't seem logical to me. You can hear the engine speed up at each throttle advance. 

I realize the RPM range is narrow, therefore each notch must be a small advance in RPM. 8 notches over a mere 1000 RPM range is only about 125 RPM change per notch. I mean, at notch 8 those 16 and 20 cylinders are screaming!

Anyway, it's neither here nor there. I'll try to do some reading on diesel locos...


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## Atlanta (Apr 29, 2019)

In the years after WW II the western german DB State RR tried to build new Steam Locos for the West of River Rhine RR Linefor the TEE - Trans Europe Express from the Border of the Netherlands to the Border of the Swiss to the german RR Station of Basel Badish RR Station.
The both new constructed Locos were the Class BR 10 001 and BR 10 002 and the should run with a TEE with around 200 Km/h also around 124 mph in regularity service as long as the Electrification had been done.
Well both of the Locos never ran this high speed, it gave lot of problems all the time.
Both locos were running onto the mainline between Kassel in North Hessia and Frankfurt at the river main in south hessia, because alongside this mainline were several backshops in every bigger town with bigger RR Station. Both engines needed repairs after they ran shortly a few days of the duty. Broken Side rods, broken bearings, problems with the stoker or cylinders were the most causes for longer repairs. Both high speed engines were a big very expensive flop.


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## GNfan (Jun 3, 2016)

Also (as I understand it), old-school diesels were Direct Current; and the RPM of the traction motors varied with the voltage coming off the generator, which varied with its RPM; which was created by the RPM of the diesel engine. The faster the diesel ran, the faster the traction motors could turn.

But most modern locomotives are Alternating Current and have alternators rather than generators; and AC motors are "synchronous", which means their RPM is controlled by the frequency of the applied current. Between the alternator and the traction motors is an electrical contraption called a "variable frequency drive" (VFD) which somehow can change the frequency. I read somewhere that an MP15AC had one VFD per truck; modern locos have one for each traction motor. Out where I used to work we used VFD's the size of big filing cabinets to control the ventilation exhaust blowers.


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## Magic (Jan 28, 2014)

The throttle regulates the current flow to the traction motors not the diesel RPM.
Diesel RPM and fuel flow are regulated by a very complex circuitry which responds to the load on the 
generator or alternator. This circuitry sets the fuel flow and RPM.
The diesel RPM will vary some but not in direct relation to the throttle position.
It's more a matter of fuel flow not just RPM that is responding to the generator load. 

To get a very heavy freight train moving the throttle may be in run 5 or 6 but the diesel/generator 
will be putting out max horsepower/kilowatts with high RPM and fuel flow. 

The diesel RPM range is pretty small to keep the engine in it's max fuel efficiency and torque.

There are those here that can explain it better than I can.

Magic


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## mesenteria (Oct 29, 2015)

Fire21 said:


> I'm certainly not a diesel engine designer nor even a diesel mechanic, but in internal combustion engines, HP increases with RPM up to a point. That point depends on valve timing, cam lift and duration, fuel injection timing and probably some other factors.
> 
> As the diesel loco accelerates, the throttle is advanced and the engine speeds up. Although the RPM range for large diesels is pretty narrow (250-maybe 1200), the HP does increase from idle, which is minimum HP, to a point of maximum HP somewhere in that RPM range. To say that the engine "is still producing the same horsepower...no more" seems to me to be a false statement.
> 
> Please correct me if I'm wrong. It's happened before! Thanks. :smilie_daumenpos:



It's a reasonable question. Think of a turbo-prop, say the P-3 or a Hercules. The turbine runs at a constant RPM-ish, some little variation, but so does the prop. There are limiters on the prop so that it does not 'overspeed', and the limiter isn't fuel or a throttle stick that the pilot must keep regulating constantly. Instead, the prop's governors adjust the _pitch_. As the prop responds to increased fuel (pilot advances the throttle for take-off), the prop doesn't speed up, and the engine only somewhat. Instead, all that fuel heat wants to turn the turbines more quickly, which would in turn want to speed the prop, but the prop is strictly limited. So, the governor advances the pitch such that it takes up all that fuel/horsepower (4600 per turbine) by changing the angle at which the blades rotate, causing them to grab a ton more air. More air over the working surface of the blades, faster speed. More noise, though, and that's what happens on a diesel locomotive.


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## Fire21 (Mar 9, 2014)

Thanks guys, I'm learning here. Never knew there was so much about diesel locos that I didn't know!! :hah: me.


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## Fire21 (Mar 9, 2014)

OK, I've been reading and have a much better understanding now of how those complicated things work. Thanks to all for your explanations. Coupled with what I've read, I can better see how RPM stays relatively the same, but the engine works harder with each notch, therefore making more noise and exhaust. :thumbsup:


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