Steam limits

quote:

what limits the top speed of a steam engine.

Only the size of the pair on the man in the right hand seat!

Other than the condition of the track (plus curves, grades and location of signals), limiting factors are boiler capacity, driver diameter, counterbalancing, main rod/piston thrust, and side rods. Maybe the valve stem and its valve in the steam chest if they move back and forth too fast. Exceed maximum safe speed and something will give way.

Generally, steam locomotives designed for high speeds have tall (big) drivers and 4-wheel pilot trucks to guide them through curves. Their frames and equalizing systems [allow drivers and trucks to move up and down and side to side] must be up to the task, too.

Nickel Plate Berkshires excelled in fast freight service with 2-wheel pilot trucks.

A rough estimate is 10 mph for every inch of driving wheel diameter.

Shays and other geared locomotives are different because their cylinders drive a telescoping shaft that turns the wheels via gears, not rods. Shays sound as though they are going 100 mph as soon as they exceed walking speed. The best place to hear that is Cass Scenic Railroad. Past the enginehouse, when a Shay begins to push a train upgrade, the engineer widens the throttle and the exhaust from 3 cylinders erupts into a roar.

Exhausts on Heislers and Climaxes are a bit slower because each has only two cylinders turning a driveshaft centered below the boiler.

I suppose a geared locomotive, pushed beyond its limits (15 mph - 20 mph), would suffer a failure in the drive train.

Anecdotal stories say that the PRR T-1's went in excess of their Barco speedometers limit of 120 MPH frequently.
Out the west of Crestline OH.

quote:

Originally posted by ChooChooDennis:
Anecdotal stories say that the PRR T-1's went in excess of their Barco speedometers limit of 120 MPH frequently.
Out the west of Crestline OH.

Actually documented by the late Vernon L. Smith, when he was working for Franklyn Rwy Supply and had to ride the T-1s between Ohio and Chicago. I have seen his notebooks, which his son, Charles, still has.

What limits the maximum RPM of the engine in your car? How fast can you spin it before it throws a rod?

Same thing with a steam locomotive. How fast can the machinery rotate and still stay together.

....or the engineer loses his/her nerve!

Also documented are instances of Milwaukee F7 Hudsons straight-lining the graphs on their 120 MPH speed recorders for several miles on end. C. H. Bilty, the Milwaukee chief mechanical honcho at the time, estimated the actual top speed at 125 MPH.

N&W's Class J 4-8-4 610, with its 70" drivers, was documented as attaining a speed of 111 MPH by PRR supervisors who rode and ran it during its tests between Fort Wayne and Chicago. Although it is certain that other 4-8-4s ran faster than that, there is no other known DOCUMENTATION of a 4-8-4 running that fast. In other words, if anybody ever did, they never bragged about it . . .

EdKing

Yes, I had heard about those notebooks. I am glad to hear they still exist. I hope they have been published or will be!

Top speed of J. Neils #5 at IRM was about 15mph. At that speed, it feels like you've reached escape velocity!

Once had a ground man riding the rear footboards dump the air on me during a move. When I asked him why, he said "You were going too fast!"

I replied, "This is a Shay! It doesn't have a too fast!"

Rusty

quote:

A rough estimate is 10 mph for every inch of driving wheel diameter.

The rule of thumb is 1 MPH per inch of driving wheel diameter.

That being said, I'm pretty sure Rich has mentioned having his favorite 69"-drivered Berkshire near the 79 MPH passenger limit a few times ('93 Akron to Pittsburgh if memory serves), so it really is a rule of thumb and not an absolute maximum.

quote:

Originally posted by ReadingFan:

A rough estimate is 10 mph for every inch of driving wheel diameter.

Ummm . . .

so a locomotive with 80-inch drivers could go 800mph?

Call me skeptical


Just to add on to what others have said, RPM is more of an indicator of top speed than MPH. Check the RPM on all the rod engine examples given, and the top speed will correlate to somewhere around 525-550 RPM. Above that, the forces associated with all those flailing rods tend to result in airborne pieces of steel.

844 has 80 inch and goes faster than 80 more like 100 mph.

Also with the shays in the race you saw the engineer raise the throttle to the roof so was there a governer on it or did the boiler run out of steam for any more speed. If you have the pentrex video on the steam celebration at Sacramento Ca it is on that video. 0 to 18 mph must have been about 1 second.

I have heard that a good rule of thumb was driver diameter +10. But that theory obviously is not a good measure as in the case of the J's and the FEF's definetly bested 90mph many times.

quote:

the engineer raise the throttle to the roof so was there a governer on it or did the boiler run out of steam

1) No, there was/is no governor, the throttle was wide open at that point.

2) Why would you think it would "run out of steam"? There was also a Fireman on duty to maintain working steam pressure during those "drag races".

L&N's "Big Emma" 2-8-4's, with 69" drivers, were once clocked by a trailing dynamometer car at 92 mph on an empty hopper train. This was shortly after the Lima Emmas arrived, in 1949. A test crew was evaluating the Lima, which was added to the 2 Emmas on a s.b. mt hopper move, for return to whatever terminal, maybe Corbin. The fellow in the dyno car decided to cut in the recorder, and got " 90-92 mph ". I would suspect that the 4 passenger Emmas, all Baldwins, prob got the "Flamingo" goin that fast, too, during WWII, when they ran Cincy - Corbin. A retired NKP hogger once told me the fastest he had seen aboard a 700 in regular freight service was 76 mph, tho I would bet some of them got going even faster occasionally. I believe 3-figure speeds for the N&W J's in Eastern VA are pretty well documented. TRAINS' DPM wrote late in the steam era that a ride to Norfolk would reveal that "you will be propelled at speeds such as you have never before moved on rails."

quote:

The faster the pistons go back and forth the more steam you need and the faster you have to get the steam in and out of the cylinders.

To be a little more clear on this subject, "more steam" is NOT necessarily the answer. Of course "the faster you have to get the steam in and out og the cylinders" is definately the key in maintaining/increasing horsepower for acceleration.

Thus enters the Engineer's PROPER use of the power reverse! At full throttle, the key is to maintain the absolute HIGHEST STEAM TEMPERATURE at the valves, as produced by the superheaters. Shortening the valve cut off, reduces steam flow/volume through the superheaters, so that the steam gains high heat instead of simply "rushing through the superheater units".

The "volume of steam", or "steam pressure" is actually NOT what propels a steam engine. The energy is from the HEAT of the steam, which expands in the cylinders. The higher the boiler pressure, the higher the heat of the steam. When the steam passes through the superheater units, the steam is heated even more, i.e. SUPER HEATED, to temps exceeding 700 degrees F.

If the Engineer does NOT have the valve cutoff set correctly, the steam temp will actually DROP, reducing HP and increase fuel and water consumption.

Jack is right on the money with his comments about the setting of the cutoff. That is absolutely critical to the proper handling of a steam locomotive at high speed.

When entering these discussions of speed, you must remember that when you get to REALLY high speeds (over 80 mph) the cutoff is set VERY short. The steam admission port is only open for a very small percentage of the piston stroke, on the order of 20% or even slightly less. However, the throttle is likely wide open in this scenario, providing a wonderful draft for the fire and very high superheat temperatures. A good fireman can easily supply enough steam to take the locomotive to "rod-throwing" speeds...IF the engineer has the cutoff set right.

A steam locomotive is much more likely to be run out of steam on a long, hard pull on a grade at 30-40 mph than it is at 80+ mph. If the engineer sets the cutoff too long in this scenario, the engine is actually using more steam at 40 mph than it is at 80 mph. It's not using it efficiently, but it is using it nonetheless. I could run the 765 out of steam at 30 mph if I wanted to, by leaving the reverse down in the corner at full cutoff and running the throttle wide open. Of course, if I did that, I would likely be banned from the cab forever and hung in effigy by the entire cadre of firemen!

I once fired the 765 in this exact scenario. We had about 30 freight cars and the engineer was running the engine hard. (It was not one of our regular guys at the throttle.) At 30 mph I had the water pump almost wide open, crowding the fire as much as I could and was slowly losing ground on both the water and the steam. When pressure slowly dropped to 210, I knew something was wrong. I finally realized that the engineer had the throttle wide open and the power reverse still full down in the corner. The railfans would have loved it because the 765 was making a deafening racket. It was without a doubt the worst I have ever seen the 765 run. When I realized what was going on, I went over to the right side of the cab, reached in front of the engineer and placed the reverse lever where it belonged. The engine immediately quieted down a little and began to accelerate. I had a brief discussion with the engineer about what the definition of a "hard pull" was and then went back to my seat on the left side. I had already gained back 15 pounds of steam and all was right with the world again.

Just to take this discussion into the asterisk category on things that affect steam loco speed and efficiency, check out the work of Andre Chapelon and Kyost Kylala, which resulted in the Kylchap locomotive exhaust system. This system made the air draw through the firebed more even and reduced back pressure.

ChipR

The 1" of diameter = 1 MPH rule of thumb does give you a good idea of the connection between the size of the driver and the speed an engine can go - but like all "rules of thumb" it's not meant to be precise, just a general estimate.

One big limiting factor on speed is the track and ballast. A train going 100 MPH can pick up ballast stones and fling them around in it's wake, potentially not just endangering people and objects near the track, but could even hit the engine and train itself.

quote:

Originally posted by ChipR:
Just to take this discussion into the asterisk category on things that affect steam loco speed and efficiency, check out the work of Andre Chapelon and Kyost Kylala, which resulted in the Kylchap locomotive exhaust system. This system made the air draw through the firebed more even and reduced back pressure.

ChipR

Well if those are anything like the Lempor Exhaust Nozzles, it may be fine those "small" steam locomotives in Europe, but sure didn't work worth a darn on a REAL steam locomotive like UP 3985!

HW,

Just as soon as I win the mega-bucks, I'll pay to try one on 3985. :>

ChipR

quote:

Originally posted by ChipR:
HW,

Just as soon as I win the mega-bucks, I'll pay to try one on 3985. :>

ChipR

Apparently you are not aware that the UP already tried the Lempor exhaust nozzel on 3985. It didn't work, and went into the scrap steel dumpster! The 3985 was returned to her proper Alco/UP nozzle design.

Is this what your are referring to?

http://www.railpictures.net/viewphoto.php?id=196014

quote:

Is this what your are referring to?

That is EXACTLY the crap I was referring to! Thanks for posting a photo of the Lempor exhaust modification on 3985.

Is that the master mechanics nozzle talked about in the UP steam book?

quote:

Originally posted by ironlake2:
Is that the master mechanics nozzle talked about in the UP steam book?

If you are referring to the above posted photo, then NO! The photo is of the Lempor modification. The original Alco/UP oil fired nozzle design is NOT the "Master Mechanics" design either. The "Master Mechanics Front End" design is primarily for coal burners anyway.

What is used now on 3985 since it was converted to oil?

Hot Water,

Sorry, no, I was not talking about the Lampor, I was talking about the Kylechap. The Kylechap exhaust system is quite a bit different from the Lampor.

Perhaps you are correct that it won't work in our large locos. However, please note that the LNER "Mallard" had a double Kylechap when it set the world speed record for steam locos and that the recently built A1 Tornado has one.

ChipR

quote:

Originally posted by ironlake2:
What is used now on 3985 since it was converted to oil?

The same exhaust nozzle arrangement she always had. See William Kratville's book, "THE CHALLENGER LOCOMOTIVES", pages 78 & 79. The firebox was converted to oil burning, including modifying air inlet arrangements, not the exhaust nozzles.

quote:

Originally posted by Hot Water:
That is EXACTLY the crap I was referring to! Thanks for posting a photo of the Lempor exhaust modification on 3985.

Your welcome.

quote:

Originally posted by Edward King:
Also documented are instances of Milwaukee F7 Hudsons straight-lining the graphs on their 120 MPH speed recorders for several miles on end. C. H. Bilty, the Milwaukee chief mechanical honcho at the time, estimated the actual top speed at 125 MPH.

N&W's Class J 4-8-4 610, with its 70" drivers, was documented as attaining a speed of 111 MPH by PRR supervisors who rode and ran it during its tests between Fort Wayne and Chicago. Although it is certain that other 4-8-4s ran faster than that, there is no other known DOCUMENTATION of a 4-8-4 running that fast. In other words, if anybody ever did, they never bragged about it . . .

EdKing

Ed,
I'm sorry but I can't remember what the name of this video was but I saw it around the time the 611 had just finished her rebuild for the first time.They had her on a 5 mile straight stretch somewhere in North Carolina.They said they got her up to 126 Point something.

I later talked to a retired N&W engineer that had run a J every day .He said that he had no doubt the J could run that fast but said back then after you pegged the speedometer you couldn't be sure how fast you were going.He went on to say that now that they have radar that he wasn't surprised that they got her to 126 MPH.

I remember the video because I live about 25 miles from the Va Museum of Transportation where the J and 1218 are and at the time the J being under steam again was as exciting to the folks in the Roanoke Valley as John Glenn circling the earth.I do remember that the Video was made by NS corporation and showed it in Birmingham being rebuilt.

David

The only videos I remember at the time was this one put out by NS....




And this one not sure by whom....

Chris I don't know who had the video but it showed the 611 thru all the stages of the rebuild and as the engineers were trying to get used to running her.There were several old guys in the cab .

I assume they were retirees who had fired and run steam(Most of those guys are gone now).This video was about an hour long.Being from The Roanoke area and into trains not to mention that a lot of my friends and relatives worked at the east end shops that 126 MPH stuck in my mind.

I thought wow thats fast.It wasn't till I joined this forum that I found out the Little Hiawatha regularly hit the century mark on it's runs

David

Hi David,

Hmmm that would be a great video to see. I'm gonna have to keep digging. And if that is the case 126mph is darn fast for a 70" drivered Northern.

David, I don't mean to disparage your post data, but that 126 mph, esp on a just-overhauled loco that had not run in years, is pretty hard to believe. On the PRR tests in which 610 got up to 111 mph, the machinery speed was some incredible figure ( which, of course, I can't now recall ), so 126 mph from 70" drivers is really difficult to imagine, even with the J's cross- and counter-balancing. Can any of you confirm the 126 figure? BTW, that is almost exactly the usually-recognized "official" fastest steam timing ever, by the British "Mallard."

Elsewhere in this thread, someone mentioned the ballast gravel as being a factor in super high speed running. TRAINS ran a piece yrs ago in which the author - DPM? - described a ride on the diesel-powered Hiawatha from the Twin Cities to Chicago. Several times the author mentioned the gravel hitting the underside of the car, with speeds in the 90's, north of Milwaukee, in the vicinity of the Wisconsin Dells.

126MPH? I'd say possible...but not likely. Especially with a freshly
shopped loco, as pointed out. There's only one way to find out. Yup,
fix up 611, and send her to the Northeast corredor with the dyno car,
and let her rip! FWIW, the Brits may have been fast, but the fastest
steam in the universe is on our side of the pond!

The 126 stuck out in my mind.I'm certain that was the figure they gave.They showed a shot of the stretch of track and said it set a record for for this engine but didn't show the record run so was it just hype maybe.I now remember I saw the video during one of our monthly safety meetings when I was at the power company.

These meetings lasted anywhere from an hour to all day and after most of the safety discussions were out of the way a more impromptu meeting took place.
I remember 2 representatives from NS were there to discuss procedure for situations where wire was down across NS track ie:where to get the track number and contact info for their dispatch center so I assume they brought the video.

This was very exciting to us not just for those that were into trains.Back when I was a little kid the Virginia museum of Transportation was little more than a park by the Roanoke river we played on the J and the other engines most of which were busted up and rusted up diesels .

The only building at the museum was a set of bathrooms.The only other display beside the trains was a Titan Missile which sits outside the present Museum building today.The flood of '85 made them realize they needed a different location.

We all new they were the most powerful 4-8-4's ever built and built solely at the east end shops.One of my friends dad was a supervisor in the boiler shop.Another was a supervisor in the car shops.I had friends who were engineers and car makers .The 3 Biggest employers in the Roanoke Valley at the time were N&W,GE, and Appalachian Power in that order.So as you can see we all here in Roanoke thought the J was the biggest and the best.

One thing you have to remember in favor of the record claim is the J had pressure feed lubrication so even being tight from a rebuild she was a little different from a lot of steam engines of her day

I will say this about the 611 .If you got the privilege to see her under steam and hear that steam boat whistle of hers it's something you'll never forget.
It's sad that she's back to being a jungle gym for little kids to play on again.

David

quote:

Originally posted by John Craft:

quote:

around the time the 611 had just finished her rebuild for the first time.They had her on a 5 mile straight stretch somewhere in North Carolina.They said they got her up to 126 Point something.

quote:

126 mph, esp on a just-overhauled loco that had not run in years, is pretty hard to believe. On the PRR tests in which 610 got up to 111 mph, the machinery speed was some incredible figure ( which, of course, I can't now recall ), so 126 mph from 70" drivers is really difficult to imagine, even with the J's cross- and counter-balancing. Can any of you confirm the 126 figure?

No, because it didn't happen. I photographed 611 on that move, and 65mph was about as fast as I can remember it going. I have a vague recollection of hearing about some 70+ running between Crewe and Norfolk in the 80s, but I never personally witnessed 611 top 70, though I paced it at 65mph more than once.

I can't think of any Southern or N&W line that's rated for higher than 79mph (ATS would be required). A train operating at 126mph would definitely get the attention of the FRA, and not in a good way. There are stories of CPR 2839 exceeding 79mph, but I don't recall ever hearing one about 611.

The RPM figure you refer to was 540RPM (drivers worn to 68 1/2"). At 126mph, that would be 618RPM.

Finally, getting 611 to 126+ on a 'five mile straight stretch' is rather unlikely - physics gets in the way. Getting 'Mallard' up to 126 required 10 miles of running downhill:

http://en.wikipedia.org/wiki/L...lass_A4_4468_Mallard

quote:

Mallard, with six coaches plus a dynamometer car in tow, topped Stoke Summit at 75 mph and began to accelerate downhill. The speeds at the end of each mile from the summit were recorded at:
87½
96½
104
107
111½
116
119
122½
124¼
and finally 125 mph. The speed recorded by instruments in the dynamometer car reached a momentary maximum of 126 mph.

At 126mph, 'Mallard''s running gear (80" drivers) would be making 529RPM.

Anyone who says 611 was operated at 126mph during the excursion era is, to put it politely, overflowing with bovine-manufactured petunia fertilizer.

ASME on 611

Interesting reading on page four.

"Under test conditions, the “J” propelled a 15-car, 1015-ton passenger train at 110 mph on level tangent track. Performance in regular service was equally impressive, with speeds on straight sections of track reported to approach 100 mph."

"A unique side-rod-and-driver counter-balancing design, in conjunction with stiffened centering of the leading and trailing trucks, permitted speeds in excess of 100 mph with drivers only 70 inches in diameter, performance unequaled by other steam locomotives. According to vibration calculations, the balancing theoretically would have allowed speeds of up to 140 mph without the rail damage that could have occurred with conventional designs."

A circa 1959 Trains magazine article spoke of 100MPH running of 611 on the final steam powered N&W passenger excursion run.