UP 4-12-2 - The formulas
Tractive Effort x speed/375 = Indicated HP
and
Drawbar Pull x Speed/375 = Drawbar HP
aren't estimates. They are mathematical relationships. TE and DB Pull may be estimates, but the formulas are accurate if the input variables are accurate. If this isn't the case I'd like to see an example. I've been working with locomotive performance for over 40 years, and I've never seen a case there these two relationships were proved incorrect.
Also, what kind of horsepower are you referring to, indicated or drawbar.? With steam locos, using the word horsepower without an adjective doesn't mean much. Kratville refers to 5,400 maximum cylinder HP for the 3900s (p127) which is the same as indicated HP, so he's specific as far as type of HP. The estimate I gave earlier of about 4,700 DBHP at 40 mph also showed 5,500 IHP at the same speed. That's one of the reasons I felt OK in posting it because it tied into Kratville's figure.
The formulas might be correct, but I think someone above was taking starting tractive effort and attempting to convert it to maximum horsepower, which you cannot do. Also, in the real world, and as you indicated in your comments regarding indicated horsepower at the cylinders versus drawbar horsepower, there are other variables and losses that come into play. If the engine wasn't being fired correctly, or wasn't working flat out at the maximum output, you get misleading data.
I agree--without having the actual tractive effort curve value for a given speed, you cannot calculate drawbar horsepower correctly.
I sold both volumes of the 4-12-2 books by Kratville and Bush, so I no longer have those curves for that engine--but at 37 mph, tractive effort has fallen off considerably from the peak.
I don't believe Kratville gives the tractive effort curve of a Challenger--at least not in my 1980 edition of his book.
John
Y6B in compound mode:
152206 pounds TE X say 5 mph divided by 375 = 2094 horsepower
Just sounds a bit low to me. Is it correct? Maybe, but I honestly have no idea.
I'm well out of my depth, but I always understood HP as being a force moving, but also sustaining, the mass at a given speed. Tractive effort is more related to torque applied somewhere along the drivetrain, say at the axles, or a driveshaft. Low speeds are where the torque comes into play, but it falls off rapidly as a HP curve climbs, and that would necessarily mean a steam locomotive develops its useful HP at speeds, often in excess of 40 mph. So, I wouldn't expect a Y to be producing much more than 1500-2000 hp below 6-8 mph.
-Crandell
UP 4-12-2 Y6B in compound mode: 152206 pounds TE X say 5 mph divided by 375 = 2094 horsepower Just sounds a bit low to me.
Just sounds a bit low to me.
"Horsepower" doesn't have any independent existence-- the force-times-speed-div-by-375 formula defines it. You measure force and calculate horsepower.
A Y6b if held in simple operation at 5 mph will develop about 155,000 lbs drawbar pull based on curves developed from road tests. At this, reading, about 2,070 DBHP is being developed. So your figure is about right. However, the DBHP curve rapidly increased to 3,200 at 10 mph, 5,200 at 20 mph and a max of 5,500 at 25 mph. These latter figures are in compound operation.
In compound operation at 5 mph, the Y6b (and the improved Y5/Y6's) developed about 130,000 lbs DB pull, or 1,700 DBHP
This is diverging from the point, but I am amazed at this comparatively small engine. If current HO models are accurately rendered, it was much smaller an engine than an H-8 or a Yellowstone, for example, but it out-performed them in terms of brute traction at start-up.
feltonhillTractive Effort x speed/375 = Indicated HP
-Don (Random stuff, mostly about trains - what else? http://blerfblog.blogspot.com/)
oltmanndfeltonhillTractive Effort x speed/375 = Indicated HP A bit off topic, but wouldn't the indicated HP be calculated from the PV diagram traced out by a cylinder indicator?
Tractive Effort X speed/375 would be a measure of drawbar HP, provided that tractive effort is measured at some drawbar. Indicated HP is indeed defined as the "fatness" of the cylinder indicator curve. Indicated HP is always greater than drawbar HP because of the friction losses in the cylinders, valves, valve gear, rod bearings, wheel bearings, and even the aerodynamic drag of the locomotive.
The indicated HP is some measure of the thermodynamic efficiency of the engine, that is the efficiency of turning steam at the operating pressure and superheat temperature into mechanical work at the piston faces. Indicated HP does not take into account the efficiency of combustion or the efficiency of heat transfer in turning coal into steam, and it does not take into account the mechanical friction losses downstream of the piston faces.
If GM "killed the electric car", what am I doing standing next to an EV-1, a half a block from the WSOR tracks?
selectorThis is diverging from the point, but I am amazed at this comparatively small engine. If current HO models are accurately rendered, it was much smaller an engine than an H-8 or a Yellowstone, for example, but it out-performed them in terms of brute traction at start-up. -Crandell
With the 2-8-8-4s, one could make an argument that the DM&IR did not utilize them to their fullest extent (e.g. lugging around ore trains at relatively slow speed) while the B&O did (not only in coal service, but full use in high speed general merchandise trains and high speed express service). The 2-8-8-4 was the perfect locomotive for the B&O's high speed main lines, while the DM&IR might have been better served with a version of the Y6b.
TE x Speed/375 is not a measure of DBHP. It's a measure of Indicated or cylinder HP. Tractive effort is not measured at the drawbar. Drawbar pull is measured at the rear of the tender. This is where the dynamometer car is located during road tests. Therefore, DBHP is calculated from tractive effort/force less the machinery resistance of the locomotive minus the rolling resistance of the locomotive and tender minus the air resistance of the locomotive. IHP is measured by indicator diagrams taken from measurements at the cylinders and converted to IHP by use of a planimeter.
This agrees in large part with earlier posts.
This is a interesting topic.I have always said despite what these new locomotives claim for horsepower and tractive effort they can still not do what the steam locomotives could do with a single engine.You could pick any locomotive out there and there is no way you are going to pull 140 cars at 30 or 40mph with a single modern day locomotive no matter what the claims.
I was told by someone once that a steam locomotive has unlimited horsepower.As long as you could produce enough steam you would basically have a locomotive that could keep pulling harder and harder as long as you could keep up with the steam supply or until the wheels started slipping.Many engineers and locomotive designers claimed the Allegeheny could produce a unheard of amount of horsepower if there was someway possible to keep the massive amount of steam going to the cylinders.Of course they never tried this expierment as you would have to have probably double the amount of fire and double the amount of water to keep the steam at the boiler maxium pressure,going full throttle,with maxium load.I can only assume you would burn through all your fuel and water in a very short time if you were going to try this(much like a truck driver trying to go up a steep hill at 75 mph with a full load).
The only disadvantage the steam locomotives had is their huge drive wheels.It was like starting a car in high gear.Diesels have small drivers so their HP and TE if very impressive.They call pull very heavy trains at low speeds.Steam locomotives with their high wheels are better at higher speeds as the sheer size of their wheels covers alot of ground with just a few strokes of the piston.Had the big boy locomotives had 36" wheels I can only imagine it would have at least 10,000 horsepower or more.
feltonhill TE x Speed/375 is not a measure of DBHP. It's a measure of Indicated or cylinder HP. Tractive effort is not measured at the drawbar. Drawbar pull is measured at the rear of the tender. This is where the dynamometer car is located during road tests. Therefore, DBHP is calculated from tractive effort/force less the machinery resistance of the locomotive minus the rolling resistance of the locomotive and tender minus the air resistance of the locomotive. IHP is measured by indicator diagrams taken from measurements at the cylinders and converted to IHP by use of a planimeter. This agrees in large part with earlier posts.
TE x Speed/375 is not a measure of indicated HP either. The HP determined from the indicator diagram is the work applied to the cylinder faces, and that gets diminished by the friction of the cylinders, crossheads, connecting rods, and wheel bearings before it gets to the wheel surfaces.
oltmannd feltonhillTractive Effort x speed/375 = Indicated HP A bit off topic, but wouldn't the indicated HP be calculated from the PV diagram traced out by a cylinder indicator?
Thomas 9011This is a interesting topic.I have always said despite what these new locomotives claim for horsepower and tractive effort they can still not do what the steam locomotives could do with a single engine.You could pick any locomotive out there and there is no way you are going to pull 140 cars at 30 or 40mph with a single modern day locomotive no matter what the claims. I was told by someone once that a steam locomotive has unlimited horsepower.As long as you could produce enough steam you would basically have a locomotive that could keep pulling harder and harder as long as you could keep up with the steam supply or until the wheels started slipping.Many engineers and locomotive designers claimed the Allegeheny could produce a unheard of amount of horsepower if there was someway possible to keep the massive amount of steam going to the cylinders.Of course they never tried this expierment as you would have to have probably double the amount of fire and double the amount of water to keep the steam at the boiler maxium pressure,going full throttle,with maxium load.I can only assume you would burn through all your fuel and water in a very short time if you were going to try this(much like a truck driver trying to go up a steep hill at 75 mph with a full load). The only disadvantage the steam locomotives had is their huge drive wheels.It was like starting a car in high gear.Diesels have small drivers so their HP and TE if very impressive.They call pull very heavy trains at low speeds.Steam locomotives with their high wheels are better at higher speeds as the sheer size of their wheels covers alot of ground with just a few strokes of the piston.Had the big boy locomotives had 36" wheels I can only imagine it would have at least 10,000 horsepower or more.
What????
samfp1943Here is a video of the 1218 in Apr 87. What is amazing is the size of the passenger train (I'm guessing; about 20 or so cars), Maybe some one can get a better count. Anyway there is a segment of the 1218 slipping on Christianburg Hill near Arthur,Va. Slipped 3 times in starting that train on the grade...Anyone provide what percentage that grade is? Thanks!
Here is a video of the 1218 in Apr 87. What is amazing is the size of the passenger train (I'm guessing; about 20 or so cars), Maybe some one can get a better count. Anyway there is a segment of the 1218 slipping on Christianburg Hill near Arthur,Va. Slipped 3 times in starting that train on the grade...Anyone provide what percentage that grade is? Thanks!
Here's something I found on google videos: The 2101 climbing the B&O's infamous 17 Mile Grade with an excursion train. That grade is an operational nightmare, climbing straight up the Allegheny Front on a maximum 2.69% grade. Video is not the best quality, but still impressive.
http://video.google.com/videoplay?docid=-2497140354363120108#
In attempting to understand locomotive data from 60 years or more ago (19 years before I was born), one of the very common issues is that it seems the railroads were too busy running their business to go back and do tests on the "improved" versions of their finest locomotive models.
Though UP did indeed perform all kinds of tests on their 4-12-2's and 4-6-6-4's as the years passed, for whatever reason, it appears we do not have any records of either improved tractive effort curves or improved horsepower curves available to us today (at least none that I'm aware of).
Also, in the case of N&W, at least Y6B #2197 received some additional improvements for a test against diesels (some of which may have been applied to other engines), and claims of 170,000 pounds starting tractive effort have been made. Yet at the same time, the "official" or "reported" starting tractive effort of 152,206 appears to have not ever been revised. Various books and websites I've read all seem to question the 170,000 pound figure for the "Improved" Y6B.
I wish we had more information than what apparently survives.
Unfortunately, for some roads (like Rio Grande) the officials at the top tried consciously to get rid of everything that had anything to do with steam power. So surviving records are extremely limited, and this makes it difficult even to produce an accurate model of their steam (without excessive scaling from photographs). I've been told but cannot confirm that what few drawings do remain in the Denver Public Library can end up costing $100 or more per page for them to dig them out and copy.
While checking my archives I remembered there was quite a bit of information recorded on the performance of the Allegheny 2-6-6-6's.Some of the biggest and most powerfull locomotives ever constructed.According to the book "The Allegheny Lima's finest by Eugene huddleston,1984"....
Allegheny #1608 estalished a all time drawbar horsepower record of 7,498hp with 14,075 tons at a speed of 46 miles per hour.Official records site 160 cars plus caboose and dynameter care with 14,075 tons.
In another test the 1608 climbed a .7% grade with 160 loads weighing 14,083 tons at a speed of 13 1/2 miles per hour.It soon accelerated to approx. 24mph and maintained this speed to the top of the grade .2% most of the way.
In 1951 they conducted tests with a new type of exhaust nozzle.They tested the Allegheny at a dead stop at the foot of a .30% grade first with 145 cars(12,284 tons) a second with 146 cars(11,620 tons)and a third with 153 cars(12,301 tons)and each time they had no difficulty starting the train up the grade.They maintained a average speed of 18 to 20 mph up the grade.
On the Virginian railroad the H-8's hauled 13,500 tons on a .20% grade on a regular basis.
We can debate friction vs roller bearings,factors of adhesion,horsepower and tractive effort,but all we really need to do is put a locomotive on a train of a certain weight and see if I can pull it.We know you can get a the correct weight of a railcar by weighing it on a scale.No matter what way you look at it a 14,000 ton train yesterday would still be 14,000 ton train today.My argument that there is no way a single modern day locomotive could pull anything close to what one of these massive steam locomotives used to despite what the horsepower and tractive effort claims to be.I know from my days as a conductor for the Union pacific there is no way in hell you can pull a 14,000 ton train up any sort of grade with a single locomotive.I doubt you could even pull a 14,000 ton train at all even on a flat grade.
While I will concede that no single unit can match the performance of a single Challenger, the miracle of multiple unit control will allow enough units to be combined as a single locomotive to equal or exceed the performance of said Challenger, Big Boy, Allegheny, EM-1, Y-6b, etc. And unlike those steam locomotives, a multiple-unit diesel locomotive can be taken apart and put back together at a different rating to match the train to which it is assigned.
CSSHEGEWISCHWhile I will concede that no single unit can match the performance of a single Challenger...
While I will concede that no single unit can match the performance of a single Challenger...
You do bring up good point about the MU ability of diesel-electrics. If it was possible for the railroads to MU steam engines under one crew, the development of the steam locomotive would have stopped with the 4-8-2 Mountain locomotive. A pair of good 4-8-2s will out perform any single large articulated ever made.
GP40-2CSSHEGEWISCH While I will concede that no single unit can match the performance of a single Challenger... Then my friend, you have no idea what a single AC6000 is capable of at speed. You do bring up good point about the MU ability of diesel-electrics. If it was possible for the railroads to MU steam engines under one crew, the development of the steam locomotive would have stopped with the 4-8-2 Mountain locomotive. A pair of good 4-8-2s will out perform any single large articulated ever made.
CSSHEGEWISCH While I will concede that no single unit can match the performance of a single Challenger...
What?
I'm not perfect, and certainly misunderstood one poster on this thread--but to say two 4-8-2's would outperform any single large articulated ever made?
Sorry, I don't think so.
Which one 4-8-2 was capable of 85000 pounds starting tractive effort???? That's what you need to match or beat the performance of a Y-6B.
How about a 4-8-2 at 88000 pounds starting tractive effort? That's what you need to match the performance of Virginian's A-E class 2-10-10-2, which had a starting tractive effort of 176,600 pounds, and which had a nice, long, healthy service career, lasting into the 1950's.
The Union Pacific Big Boy and other large articulateds actually got over 6000 horsepower to the drawbar (over 7000 for the 2-6-6-6). How many 4-8-2's produced 3500 horsepower?--Oh, and by the way--they still had two crews to one crew for the large articulated.
Please don't try to tell me that twice as much manpower is more efficient than that large articulated.
Over on steamlocomotive.com, they have the NYC Mohawk ranked as the best 4-8-2 ever built. Though it could run 80 mph, the highest tractive effort version produced a puny (compared to articulateds) 60617 pounds of starting tractive effort. Your'e going to need three of them to narrowly exceed Virginian's 2-10-10-2 in a slugfest from a standing stop.
UP, we seem to have slipped on some terms, and hence your confusion (I think it's yours...forgive me if not...). GP said that, as long as we agree that we could MU either diesels or steamers, then two Mountain-types could out-perform a single articulated of any kind. Two of them, not one.
To back up, the person before GP said that the diesels have an advantage in terms of their configuration as a hauling unit. Steamers less so. If....IF...we were to group in like ways, MU'd diesels and MU'd steamers, GP says that there would hardly have been the need to develop any single articulated because two Mountains, if MU'd as diesels were, would have been the defining requirement in steam.
I hope I have accurately reflected GP's thoughts.
Ok, Crandell, I misread the part about mu'd as diesels, ie, only one crew. Sorry.
However, the argument still doesn't totally work for me, because the big articulated offers some efficiencies that you just don't get with multiple smaller steam engines.
selectorUP, we seem to have slipped on some terms, and hence your confusion (I think it's yours...forgive me if not...). GP said that, as long as we agree that we could MU either diesels or steamers, then two Mountain-types could out-perform a single articulated of any kind. Two of them, not one. To back up, the person before GP said that the diesels have an advantage in terms of their configuration as a hauling unit. Steamers less so. If....IF...we were to group in like ways, MU'd diesels and MU'd steamers, GP says that there would hardly have been the need to develop any single articulated because two Mountains, if MU'd as diesels were, would have been the defining requirement in steam. I hope I have accurately reflected GP's thoughts. -Crandell
The most modern 4-8-2s, built in the late steam era, were 4000 HP machines, capable of nearly 70,000 lbs TE, and 100 mph speeds.
MU two of them and you have an 8000 HP, 140,000 lbs TE lash up that is still capable of moving tonnage at 100 MPH. You might find a low speed articulated that can produce more than 140,000 lbs starting TE, but it isn't going to produce 8000 HP at speed, and it surely isn't going run at 100 mph.
This Baldwin R1d, built in 1941 for the B&M is a good example. With a 495 sq.ft. firebox area, 2000 sq.ft. Superheater, and a total heating surface of 6,500 sq.ft., it was a serious, no-fooling-around high HP speed machine.
There really is not a single individual diesel locomotive being bought in any quantity today that is really the equal of a Challenger. The equivalent power and/or tractive effort would take two or more units. But that is probably more of virtue for diesel power than a liability, because it allow better matching of the power to the job at hand.
But that doesn't detract in any way from the sheer beauty and enjoyment of seeing a well-desigend and well-maintained and well-operated steam locomotive hauling a heavy modern freight train of a type undreamed when the locomotive was built over well-maintained and well-despatched track. The UP and its employees can be very very proud of their continuation of mainline steam heritage operations.
And the skill of the CSX T-1 engineer in recovering from the slips is also to be applauded/
There really is not a single individual diesel locomotive being bought in any quantity today that is really the equal of a Challenger.
.
One advantage that a pair of 4-8-2's would have over a single articulated is that they would have 2 fireboxes, 2 large grate areas, 2 throat sheets, 2 shorter sets of flue tubes - albeit maybe almost the same total length, and 2 stacks for exhaust - though a few articulateds had those too, as I recall. As such, I believe that the pair of 4-8-2's would have a much higher total fuel / coal consumption rate and easier drafting than the single articulated - hence it follows that they would be able to produce more power than it.
And if we view a Challenger through modern lenses - isn't its driving wheel arrangement really similar to a a C-C diesel - only it's technically a 2-C+C-2 instead ? And on the PRR they called that wheel arrangement a GG1 - which in their prime I'd like to see matched against said Challenger, the pair of Mountains, or any other modern C-C diesel unit . . . Would the PRR have classified a Challenger as a 'GG2' ?
- Paul North.
A 'heavy' = 420,000 lb. = 210 tons or so C-C with 70,000 lb. axles loads at only a 33 % coefficient of friction = 3.0 factor of adhesion will produce that 140,000 lbs. of tractive effort that's cited above for the Challenger - at the 40 % which is sometimes cited for the AC-drive locomotives it would be 168,000 lbs., which I believe would top all of the steamers.
HorsePower is different - the production diesels appear to be practically limited to about 4,400 HP, since most of the 6,000 HP units appear to have been retired, so the big steam locomotives would be able to top that figure - but only a few could reach over the 6,000 HP threshold. And since above a certain speed usually in the 15 to 20 MPH range the TE starts to drop in inverse proportion to the speed due to the HP being limited - which doesn't happen quite as much or in the same way for steamers - a steam engine might be able to produce more TE than the diesel at the same and higher speeds, which would mean that the steam locomotive is also a higher HP machine at those faster speeds.
So in terms of sheer lugging power, the AC unit would win. But at speed, it would be a closer contest, probably depending on the specific train resistance and grade, and speed range.
All probably very true, fellas, and I sure appreciate the way all of you ran with this for me.
I will say this, though...if there had been a crowd witnessing a contest from a full stop, with two equal consists, one pulled by a single AC4400 or whatever, and one pulled by #3985, I wonder which would eliciit the stronger cheering section.
Ok, fine, some modern diesels might roughly match the performance of a single Challenger, or exceed it at slower speeds--but they will not provide the sheer drama provided by that Challenger.
Sorry, I've spent many nights, and Saturday and Sunday afternoons at Horseshoe Curve or at ALTO Tower during the 1980's. I still can and will forever be able to see Conrail's ex-EL SD45-2 helper engines in my mind's eye (including "Satan's Engine" 6666), but diesels are just plain boring when compared to steam, whether real or in model form. My sons could give two hoots about diesels, but put an MTH Challenger in front of them with the sound, lights, and smoke, and they both (even the one who no longer plays much with trains at all) are captivated.
There simply is no other machine that offers the same visual and sensory impact of working steam power.
On that we agree. From an aesthetic standpoint, I'd trade about 10,000 diesels for another Challenger.
UP 4-12-2 [snip] Sorry, I've spent many nights, and Saturday and Sunday afternoons at Horseshoe Curve or at ALTO Tower during the 1980's. I still can and will forever be able to see Conrail's ex-EL SD45-2 helper engines in my mind's eye . . . [snip]
Then you might enjoy the following little video - not mine, I just found it elsewhere on the 'Net about 2 weeks ago - supposedly from 1991 of a minor derailment on the Curve, and the sounds of the rear helpers throttling back to come to a stop at the western calk of the mountain there - it's about 5-1/2 minutes long, and well worth viewing and listening - takes me right back as if I was there. It's notable as an actual recorded instance when railfans were able to notify a train crew of a problem - read the caption notes for the full story. The rear helpers - SD40-2's 6387 and 6384 if I read and identify them right - go by from 1:10 to 1:20, and have come to a stop by 2:30. The derailed car goes by at about from 0:17 to 0:22:
http://www.youtube.com/watch?v=MwwVsRlS2eU
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