Hi folks - this invites anyone who wants to discuss the above topic . So here you have a thread of your own and you no longer have to take refuge within the N&W steam development thread .
Have fun
= J =
Uh-oh, diseasels, out of my league.
Wayne, Juniatha,
Mark Twain's suggestion from Innocents Abroad: Gatling guns at 10 paces....
- Erik
A bit of background - the locomotive rating in question was the 1350HP for the EMD FT - with the disagreement involving whether that was gross HP akin to the old SAE gross for US autos or net, that is HP available to the traction generator/alternator after subtracting power for the auxiliaries. My understanding is that US locomotives are rated by net power available to the traction generator/alternator.
The old SAE gross was a bit of a laughingstock n the automotive world, where the actual power available was nowhere near the rated power, which was measured with all accessory drives removed and minimal exhaust restriction. Things improved a bit in recent years, though a dyno test of a Dodge Ram pick-up with a V-10 rated at 300HP only delivered ~230HP at the rear wheels. The same test showed a Dodge Cummins delivering 165HP at the rear wheels with an engine rated for 160HP. A further aside, Hugh McInnes in his book on turbochargers noted rear wheel dyno HP was rarely less than 96% of the engine only dyno reading for manual transmissions.
There's an additional gotcha when discussing electric transmissions. The throttle on the diesel engines set the governor RPM, but the load imposed on the engine is set by the traction generator/alternator. In order to keep the prime mover from stalling on a hot day on Sherman Summit (think low air density), the induction system must assure that sufficient air gets into the cylinders to ensure that the fuel will be completely burned. On a normally aspirated 4 cycle engine or a Roots blower equipped 2 cycle engine, that means there is enough air available at standard temperature and pressure to produce well above the rated power of the engine. The rated power is not based on maximum possible torque at a given RPM, but on the maximum power output consistent with acceptable engine lifetime.
As for transmission efficiency, GE was showing geared traction motor peak efficiency of ~92% in the late 1920's, megawatt sized DC generators were likely to be around 92-94%, so efficiency at the operating sweet spot was comfortably above 80%.
Final note, the K-M's bought by the SP and D&RGW were rated at 4,000HP by the manufacturer, but would have been considered ~3,600HP locomotives by US standards.
EMD always rates their locomotives on "traction HP", which is shaft HP into the generator for traction. In practice, you calculate it by measuring the "net traction HP" - which is the V x A / 743 out of the main gen and dividing by the main gen efficiency.
You measure it at AAR std conditions, which is std atmospheric pressure ath 1000 ft elevation and 60 deg F air temp and 60 deg F fuel temp. These stds might have been slightly different in 1939... Sometimes RRs had their own stds, and EMDs stds might have been different, too. But, not much different.
One other thing to note. The governor will regulate std volume of fuel at full speed, full load. So, if fuel is cold, the locomotive will make more than rated HP, if hot, less.
-Don (Random stuff, mostly about trains - what else? http://blerfblog.blogspot.com/)
Firstly, I should point out that while in British usage, "motor" and "engine" are interchangeable, in the United States usage, the word motor tends to be restricted to very small internal combustion engines although all sizes of electric motors are called that. My 645E blower type book is described as an "Engine Maintenance Manual" and uses "engine" throughout.
Should she agree, Juniatha might wish to alter "motor" to "engine" in the thread title.
EMD had a specific formula for calculating the difference between gross and net engine power. I can't find my copy of the description, but off the top of my head, an unloaded air compressor absorbed 100 HP and one AC motor driven radiator fan absorbed 33 HP. This would account for most of the difference in a GP18 where the 16-567C has a gross rating of 1950 HP and a net rating of 1800 HP.
My 645E book included a page called "Locomotive Major Component Evolution" which gave interesting basic details for most major models:
For the FT, the 16-567 engine was shown as 1350 HP at 800 rpm.
The D8 generator was shown as 950 kW and 1800 Amps
The D7 traction motor was shown as 260 kW and 700 Amps
For the SD45-2, the 20-645E3 engine was shown as 3600 HP at 900 rpm
The AR10B4 alternator was shown as 2563 kW and 4200 Amps
The D77B traction motor was shown as 359 kW and 1050 Amps.
The calculation of the net power on the FT would be different because it used mechanically driven radiator fans but one assumes that the basics were the same. The ratings of the generator and traction motors are consistent with 1350 HP input to the generator.
M636C
@ M636C
>> Juniatha might wish to alter "motor" to "engine" in the thread title. <<
No , I won’t .
To make this clear once and for all :
I will *not* change , modify or adapt my language , my wordings or my spelling in any way to neither of your overweening requests , arrogant teachings or pretentious corrections . If you have problems reading my texts that’s *your* problem , not mine .
I seriously ask you to stop nitpicking at my postings . It is known by now that you don’t like them so just quit reading them ! That’s all . Full stop .
Bye now .
---------------------------
Add : On motors :
A Rat Motors :
this bowtie also packs a 1,000 hp supercharged 485 ci motor under the hood.
http://autoholics.com/2011/05/10/1-000-HP-Fifth-Gen-Camaro-Rat-Rod-531028
some rat motors
http://www.popularhotrodding.com/tech/1201phr_15_hottest_crate_motors/viewall.html
534 Blown Altered Motor on Dyno
http://www.youtube.com/watch?v=c_GNUfmVa6o
How the big Chevy motors of yesteryear got their nicknames
http://answers.yahoo.com/question/index?qid=20071231084952AATrpRt
427 Rat Motor
http://www.youtube.com/watch?v=aKFIWWYqspg
Bad Rat Pro Street Motor
http://www.youtube.com/watch?v=q55FqNICZpc
Rat Motor Uncorked
http://www.youtube.com/watch?v=760VbyaNAZ8
Sounds like a Rat Motor to me
http://www.youtube.com/watch?v=DlY3cWaYgKQ
71 Chevelle 1100 hp 632 firing up
http://www.youtube.com/watch?v=1L3XI1nPels
The baddest Camaro in the country at Cassill Motors
http://www.youtube.com/watch?v=-Vk9zo5_5_k
SLP ZL 575 Camaro tested by MotorWeek TV
http://www.youtube.com/watch?v=XERWgDVpmB4
B Mouse Motors :
World’s first blown 440 Small Block ..
http://www.youtube.com/watch?v=rAnK-uXl9Fk
Typically, by strict interpretation an "engine" is a machine that generates its own power, i.e. "internal combustion engine", "external combustion engine", and so forth.
A motor uses energy derived from another source, i.e. an electric motor.
But when you come right down to it it really doesn't matter a damn what it's called, what matters is that you know what it does. People use the terms "engine" and "motor" interchangeably and the world doesn't stop when they do.
Lets just end this and use the term "Prime Mover"!
NorthWest Lets just end this and use the term "Prime Mover"!
That's fine. But after ending it let's get back to the REAL topic of discussion, which includes how the output-shaft power from an EMD engine is rated, and by extension, how far the observed DBHP drops due to calculated or actual losses in the drivetrain. Particularly at different ranges of road speed corresponding to different modes of operation of the electrical drive.
Not to add fuel to the fire of this already contentious thread but it really should be on the Locomotives forum.....
"I Often Dream of Trains"-From the Album of the Same Name by Robyn Hitchcock
carnej1 Not to add fuel to the fire of this already contentious thread but it really should be on the Locomotives forum.....
1. This thread is far from contentious. It is a serious technical discussion where at least one person with railroad motive-power work experience has weighed in.
2. This thread was in response to a claim by Juniatha during a steam locomotive discussion that the pioneering EMD FT mainline freight locomotive rated at 1350 HP was only good for about 900 HP "at the wheels" and that the FT needed a large number of locomotive units to equal the horsepower of a mainline steam locomotive of the day. A multi-unit FT had vastly more tractive effort than most single-headed steam locomotive consists, with the possible exception of a specially ballasted Norfolk and Western Y-class, but the low HP, even with four units, probably resulted in climbing "ruling grades" at a crawl.
I expressed the view that I remembered that the EMD (and other US Diesel locomotive mfr) rating of HP is at the generator after taking into account accessory loads (exciters, cooling fans, air pump) but before taking into account the efficiency of the electric drive, and that 900 HP seemed low, even after taking into account losses in the electric drive.
3. How Diesel locomotives are rated are an important part of the comparison between Diesels and steam and understanding the engineering trades during the Transition Era where the railroads replaced steam with DIesels.
4. The First Generation Diesels that persuaded the railroads to scrap steam are eclipsed by modern Diesels and maybe the performance comparison with late-day steam was a closer thing than many realize -- maybe railroad CME's were also looking to trends to where they thought Diesels would improve in the future in making the decision to Dieselize -- this is of historical importance in understanding why the curtain came down on steam, when it did.
5. I think that any and all of the participants here can shrug off the criticism that this thread "is on the wrong forum." But often times we get model railroad questions over here, often model railroad questions from new forum members and people new to the model-train and full-scale train enthusiasm hobbies. I wish people would take the trouble to be a little bit more gentle in steering people back the MR forum, maybe something along the lines of "Good question. Maybe try the Model Railroad forum because the folks over there may know a better answer." I have seen some "you are posting this on the wrong forum, pal" posts that may not be engendering good feelings in newcomers.
6. The forum divisions are in some ways artificial. The intent of the gracious and generous people at Kalmbach publishing is to spread out the commenting so new topics don't get pushed down the list before people get a chance to comment -- the Railroads forum is one where it is hard to keep a thread active for that reason. But Diesel discussions are not exclusive of Steam and Preservation as the First Generation Diesels are pretty much in the domain of preservation, apart from some Geeps and ALCos soldiering on some short lines.
If GM "killed the electric car", what am I doing standing next to an EV-1, a half a block from the WSOR tracks?
Paul ,
while I was not intending to participate in this discussion , you correctly mentioned it’s [edit:] origin . My intention was to invite those who already had started this discussion in a thread definitely dedicated to a different topic to continue it in a thread of their own , explicitly put up for that – to make transition easier is why I kept it to the same forum . I agree with your pointing out importance and meaning of diesel power rating in relation to steam at the time of transition .
My net 900 hp rating may look a bit low in the light of recent contributions –I never claimed I had documents , I wrote it was what my late father had told me – and that may well have been of *practical experience* – be it , the diesels original 'full throttle' settings had to be somewhat eased as it had turned out factory setting had been a bit optimistic in view of longevity in rough railroad daily service – be it , he referred to a less than optimum point of working , yet vital to train running , such as freight train or passenger train scheduled maintained line speed , not crawling up a grade ( you know that diesel motor characteristics do not smoothly conform with generator characteristics over all the power and rpm field , so you have an optimum overall point of working ) – be it , he referred to other , then frequent enough , incidents that led to compromising a diesel unit's actual working output in everyday service and in everyday so-so condition and maintenance . Even today , ever so often on US RRs a diesel is kept running although it’s badly wanting and may already spout flames for serious malfunctions , bet you this was the case more often in the early years – clearly , such engines could not be expected to run full nominal output . All in all , I have no guarantee his 900 hp net output referred to your 1350 hp gross input to generator , more likely what he referred to was what these diesels could *actually* and on *average* condition be expected to perform in daily traffic - disregarding shiny-new factory specs . Unfortunately , I was quite young at that time and didn't ask scrutinizing detailed specifications , while today I can't ask again because it's over ten years now he passed away from this world .
Personally , I tend to doubt anything not strictly related to the motor's needs had been deducted , not even DIN standards ask for that . So for deduction I can believe water pump ( for diesel motor cooling water circulation ) , maybe air fan for radiators , high pressure diesel pumps , lube oil pump - but not air pump for braking , air fans for generator and traction motors or any other non diesel motor related auxiliaries .
Case of DB diesels : when the 216 class diesel-hydraulics , nominally 1900 DIN crank shaft PS ( = 0.98632 hp) proved incapable to replace 03 light Pacifics or 23 light 2-6-2 ( of nominally 2000 / 1800 cylinder PS ) , a stronger 2500 DIN crank shaft PS version was developed , 218 class ; this series was equipped with extra generator for electric heating . To the logic of deducting anything auxiliary and counting but net hp to main generator , these engines should have been rated some 1900 or even 1800 PS again and it would have been clear from the beginning at least in winter there would be no advance with these over the former series equipped with boiler for steam train heating . Yet , as I mentioned , such auxiliaries not needed for the diesel motor itself were by rule not deducted for nominal engine output , DB pointing out that in summer when most heavy passenger traffic was up , power taken off for electric heating was then available for traction . As it turned out , the Pacifics still were hard to beat and as I was told by friends who had witnessed these change of traction days it was only by severe neglect of the steamers that the practically new diesels could finally meet steam schedules no worse than worn out and run down Pacifics did only month before their - in cases dearly anticipated - withdrawal . That was why DB asked for and finally had a version turned out equipped with an additional ~ 1000 PS gas turbine booster , 210 class , meant to power both or alternatively train heating generator and / or traction gear input . That ~ 3000 PS combination looked fine on paper but in practice went the way of much special tech equipment with railroads / railways : they don't want to take special care and in the end it's all just uprooted and the engines run without it . It was this sort of meandering diesel power development that gave an extra lease of life to the oil-fired three cylinder Pacifics , 012 class , since it clearly remained impossible to replace these engines by diesels on a one-to-one basis and in 1972 when diesel finally replaced Pacifics on the Hamburg & northwards runs , schedules had to be lengthened and then maximum loads cut to suit 215 / 218 class performance .
Aug 28th - Addenda : The earlier 2 x 1100 PS V12 motor diesel-hydraulics V200 ( later 220 ) class proved troublesome when introduced with epidemics of gear failures when but nearly extended . As Dipl. Ing. Duering wrote in his book on standard Pacifics , Hannover shed helped themselves by assigning the V200 nominally intended for heavier trains with their eight powered wheels and high starting t.e. to trains of but around 300 t and all heavier trains to their remaining 01 class Pacifics . On the North - South mainline , oil-fired 01.10 ( later 012 ) class Pacifics then still based at Bebra taking over a train more often than not had to try and make up time lost by a V200 , Duering wrote . Also , Mr Fleming , then responsible for motive power stock of the Hanover region resisted acquisition of more V200 engines due to their unsolved problems and unreliable service and pointed out he still had sufficient numbers of "fully serviceable" 01 class Pacifics available which could well secure express service for the next foreseeable future until - quote - " to directly change over to electrification without interim diesel traction " . When V200 were allocated to southern engine sheds , such as Lindau to replace the venerable old Bavarian S 3/6 compound Pacifics and a specially geared version appeared on the steeply graded Schwarzwald line , dieselization ran into a fiasco and had to be halted until a substantially strengthened version V200-1 ( 221 ) class had been developed which then bumped both S 3/6 from Munich - Lindau relation , the Allgau line , and P10 class three cylinder Mikados from the Schwarzwald line . It were those 2700 PS engines that finally were to send the last , completely worn out survivors of 012 class onto the storage track below the pebbles at Rheine shed . Rheine ( and Emden ) shed as the selected final steam shed had always lived on 'consuming' engines , partly at stupendous rates during the years of 1968 .. 71 , and then asking for replacement . Clearly , things had to come to an end pretty rapidly when there was no more supply of steam locomotives becoming surplus at other sheds . At that time it had been no big thing to replace an ex 3000 continuous cylinder PS Pacific ( output as rated from actual performance in traffic , above nominal rating ) by then perhaps worth scarcely ~ 2000 PS and limited by special order to 75 mph ( 120 km/h ) due to excessive wear and fatigue in chassis and bogie related components . Passenger train service performance level on the limited speed Emsland line was never anywhere near what had been asked of the engines when *fully* extended on the Westerland line Hamburg to the North or earlier in their career on the Rennbahn ( 'race track' ) Osnabrueck - Bremen - Hamburg . Yet , I think it may not originally have been planned to lay aside the 012 in May 1975 when freight traffic still continued with steam 042 and 043 classes until September 1977 ; it seems it was unexpected rate of wearing out of the 012 Paciics that finally demanding interim diesel passenger traction to be introduced to what by then must have been a hopelessly slapdash steam shed ( another notorious one was said to have been Hagen-Eckesey where they not only 'succeeded' in thoroughly ruining the 03.10 Pacifics to the extend no other shed wanted the reboilered roller bearing engines when Hagen got electrified , they also managed to do the same to E19 electrics later on ) However the 220 class engines only played a transient role on the Emsland line and soon were superseded by other power ; some ended up sold to an Italian rail company where they got 'consumed' pretty progressively to be sent to the torches .
Note : two , let alone more than two , engines on one train was strictly off-limits in Europe , not just DB , considered inefficient for excessive locomotive mass , first expenditure , maintenance costs , number of involved parts and components , inconvenience of joining and separating the locomotives , overall length of joined power etc ..
Well , now I leave this thread to those who have substantial knowledge of the specifications of diesels by EMD / ALCO / Baldwin / Fairbanks-Morse .. and – hopefully – will be able to post a few documents of that time in question . So ..
Gentlemen , start your diesels !
Juniatha
Juniatha,
If the D8 generator on an FT could put out 950kW as related by M636C, then with a traction motor efficiency of 90%, the FT should have been able to deliver 1140 dbhp at the optimum speed. The 950 kW figure equates to a generator efficiency of 94.3%, which is believable for that size of machine. This would also imply a peak efficiency of around 85% for the electric transmission - which is about the same as the Voith transmission used on the Espee/Rio Grande K-M's.
A lower DBHP figure for an FT may be due to the prime mover being de-rated by lowering rpm's for the governor settings, or by backing off a bit on the excitation of the battery winding on the D8 generator. The latter is what sets the loading on the prime mover - very much the opposite of a constant speed prop on an aircraft, where the rotational speed is controlled by the prop, but torque is controlled by the engine.
As for Rat Motors and elephants - the horsepower rating for the L88 and the street hemi had little to do with reality. The published horsepower rating for the L88 was given at 2,000 rpm below the torque peak and the street hemi's published power output was well less than what the dyno measured.
erikem If the D8 generator on an FT could put out 950kW as related by M636C, then with a traction motor efficiency of 90%, the FT should have been able to deliver 1140 dbhp at the optimum speed. The 950 kW figure equates to a generator efficiency of 94.3%, which is believable for that size of machine. This would also imply a peak efficiency of around 85% for the electric transmission - which is about the same as the Voith transmission used on the Espee/Rio Grande K-M's. - Erik
McCall's book gives DBHP for a bunch of SFe locomotives, presumably measured with their dynamometer car:
At 35-40 mph,
5000 dbhp for four FTs
5400 dbhp for four F3s
5800 dbhp for three PA/Bs
But it doesn't give any timings-- what speed the engines could actually do with X tons on grade Y. One wonders whether they could live up to those powers, and if they could, for how many years.
I clocked five near-new SD40-2s at 40.4 mph on continuous 1.4% with 85 empty gons, about 2550 American tons. With the returning loads seven SD40-2s did 27 mph on 1.0%; we don't know how close to 263,000 lb the cars grossed, but even if they were only 125 tons apiece...
Paul Milenkovic carnej1 Not to add fuel to the fire of this already contentious thread but it really should be on the Locomotives forum..... 1. This thread is far from contentious. It is a serious technical discussion where at least one person with railroad motive-power work experience has weighed in. 2. This thread was in response to a claim by Juniatha during a steam locomotive discussion that the pioneering EMD FT mainline freight locomotive rated at 1350 HP was only good for about 900 HP "at the wheels" and that the FT needed a large number of locomotive units to equal the horsepower of a mainline steam locomotive of the day. A multi-unit FT had vastly more tractive effort than most single-headed steam locomotive consists, with the possible exception of a specially ballasted Norfolk and Western Y-class, but the low HP, even with four units, probably resulted in climbing "ruling grades" at a crawl. I expressed the view that I remembered that the EMD (and other US Diesel locomotive mfr) rating of HP is at the generator after taking into account accessory loads (exciters, cooling fans, air pump) but before taking into account the efficiency of the electric drive, and that 900 HP seemed low, even after taking into account losses in the electric drive. 3. How Diesel locomotives are rated are an important part of the comparison between Diesels and steam and understanding the engineering trades during the Transition Era where the railroads replaced steam with DIesels. 4. The First Generation Diesels that persuaded the railroads to scrap steam are eclipsed by modern Diesels and maybe the performance comparison with late-day steam was a closer thing than many realize -- maybe railroad CME's were also looking to trends to where they thought Diesels would improve in the future in making the decision to Dieselize -- this is of historical importance in understanding why the curtain came down on steam, when it did. 5. I think that any and all of the participants here can shrug off the criticism that this thread "is on the wrong forum." But often times we get model railroad questions over here, often model railroad questions from new forum members and people new to the model-train and full-scale train enthusiasm hobbies. I wish people would take the trouble to be a little bit more gentle in steering people back the MR forum, maybe something along the lines of "Good question. Maybe try the Model Railroad forum because the folks over there may know a better answer." I have seen some "you are posting this on the wrong forum, pal" posts that may not be engendering good feelings in newcomers. 6. The forum divisions are in some ways artificial. The intent of the gracious and generous people at Kalmbach publishing is to spread out the commenting so new topics don't get pushed down the list before people get a chance to comment -- the Railroads forum is one where it is hard to keep a thread active for that reason. But Diesel discussions are not exclusive of Steam and Preservation as the First Generation Diesels are pretty much in the domain of preservation, apart from some Geeps and ALCos soldiering on some short lines.
Speaking to point #5 -whenever I have replied to anyone who has posted a Model Railroad specific question on the "Trains Magazine" forums I have always phrased my reply with something to the effect of "You would probably get a better answer to your question if...", in other words, I was trying to be helpful, so we are in agreement..
My response above was aimed at giving more people with an interest in Diesel engine technology a chance to be involved in the discussion; I was not attempting to dictate what can and cannot be discussed on this forum..
BTW, a somewhat heated discussion/debate of the correct usage of the word "motor" would qualify as contentious in my book....
timz McCall's book gives DBHP for a bunch of SFe locomotives, presumably measured with their dynamometer car: At 35-40 mph, 5000 dbhp for four FTs 5400 dbhp for four F3s 5800 dbhp for three PA/Bs But it doesn't give any timings-- what speed the engines could actually do with X tons on grade Y. One wonders whether they could live up to those powers, and if they could, for how many years. I clocked five near-new SD40-2s at 40.4 mph on continuous 1.4% with 85 empty gons, about 2550 American tons. With the returning loads seven SD40-2s did 27 mph on 1.0%; we don't know how close to 263,000 lb the cars grossed, but even if they were only 125 tons apiece...
McCall gives much more useful data than just those bare numbers....
On pages 176 and 177 drawbar horsepower and tractive effort is tabulated for a variety of diesel locomotives from the period of the book at speeds from 5mph to 105 mph (as applicable), but these are compared with the seven major steam types operated by Santa Fe at that period from Pacifics to 2-10-4s I think Timz concerns about speed are relieved by comparing the power at a given speed with that of the equivalent steam type.
The FT type in particular developed more power at any given speed than both classes of 2-10-4 up to 35 mph but even above that speed, the most powerful steam locomotive was only about 200 HP ahead. The other interesting point was that three separate four unit FT sets were tested, 100, 106 (the first with low speed freight gearing) and 164, a set equipped for passenger service complete with steam generators. While the first high geared set 100LABC registered 5000 DBHP, so 1250 DBHP per unit, 106 LABC reached 5040 DBHP, so 1260 DBHP per unit and 164LABC got to 5100 DBHP or 1275 DBHP per unit. I would suggest that 164 was developing more than 1350 HP into the generator per unit on these trials. Although, as I said earlier, heat and altitude would reduce these ratings, as might wear and tear, when new and in good condition these FTs were good for well over 1200HP at the rail by any measure. The very first Passenger F3s were good for more than 1350 DBHP when new, being basically just an improved FT with upgraded versions of the same equipment throughout. So, in general, the tabulated figures from instrumented trials show every FT tested as producing 33% more than 900 hp at the drawbar, and I would be surprised if they ever fell to 900 HP in normal service. On the other hand, the early E units with 201A engines only produced about 70% of their rated 1800 HP per unit at the drawbar, and we must assume that their input to the generator was less than 900HP per engine.
M636C Passenger F3s were good for more than 1350 DBHP when new
M636C I think the 950 kW was a nominal rating, rather than the output with the engine producing 1350 HP. Since EMD still quote the FT rating as 1350 HP and equated it to the rating of the SD45-2 of 3600 HP, we must assume that the rating conditions were regarded as the same, since the purpose of the "evolution" card was to show the relative power development over time, in this case 1940 to 1972. Certainly the rating of locomotives in the 1950s and 1960s by EMD referred to a "guaranteed input power to the generator" of at least the quoted 3600 HP for the SD45 under the temperature and atmospheric pressure conditions defined as the reference conditions. While the FT had quite different auxiliaries, with mechanically driven radiator fans, so you can't calculate on only one running for rating conditions since they presumably all ran at all times with air flow controlled by louvres.. So even assuming 90% efficiency of both generator and motors, so 81% to the rail still gives just under 1100 HP at the rail under reference conditions. However this power would be reduced on a very hot day (above say 100 F) and also at a higher altitude, so it is possible that say a Santa Fe FT on Cajon Pass in summer might produce as little as 900 HP at rail in those conditions.
M636C,
I spent a bit of time going through old issues of the "GE Review" to get a sense of generator efficiency. GE claimed that the 2MW M-G sets built for the original Milw electrification were good for ~92% efficiency from 100 - 150% of continuous rated load. This was for efficiency from the motor terminals to generator terminals. With this in mind, a 94% efficiency for the D8 traction generator seems reasonable. Assuming 91% efficiency for the traction motor (this includes gear losses) would give 1150 HP at the rail for 1350 HP delivered to the traction motor (85.5% transmission efficiency).
The measurements of 5,000+ HP for a four unit FT imply that the engine was actually delivering more than 1350 HP to the generator. This would indicate that the 1350HP was a nominal rating as well.
A possible explanation for the 900 HP at the rail would assume that the reading was taken at max speed for the motor gearing. The generator may have reached max output voltage, limiting the power that could be delivered to the traction motors - for a given terminal voltage, the current that can be delivered to a series motor is inversely proportional to the speed, and thus power would be inversely proportional to speed.
Ok, one thing to know here as well, the Hp = V x A /743 isn't how the EMD book show it. They do the equation like this Hp = V x A / 700. I do not know why EMD does it this way but they do. One question though, I thought that 746 was the number that should be used, instead of 743 in the above example, except EMD doesn't?
.
BigJimWhy wasn't this "Diesel" thread posted to the "Locomotives" forum instead of the "Steam" forum?
See the OP's own explanation (posted Aug 27, 2013).
Very well , thanks , Prof O. !
You know, if you folks wanted the real skinny on what has power and what doesnt, why not take a look at history instead of books. One thing many folks dont know is "experience wrote the book, not the other way around".
If you want to compare an EMD to steam, do so in the real world by 'example'. Because no matter how you take your HP readings, or what formula you use, what really counted was what loco really pulled what compared to another, out there on the rails. Rarely, did the loco match the expected desires. Sometimes better, sometimes worse. So do you really want to use those figures? No!
There are many records available that list what each loco for a certain railroad can/did do. Railroads use these to this very day! THAT, my friends is the end all be all of whats what in the HP department.
You have to know that yesteryears rating of power is certainly different than todays ways of doing it. Also, even though those ideas, formulas, stats, came from the best minds of that day, todays figures, formulas, and tests are certainly more accurate.
Example - I bet alot of you would be shamefully suprised to know that the often listed Berkshire having 3500 hp at the drawbar is actually closer to 5000hp. Another reason why you will see a Berkshire outpull even todays modern 4400hp AC locos. Loco vs loco, same track, same train, same engineer. But if you read the spec books, youd never know it. And youd lose the bet! - End example.
Lastly - yes, the engine or motor in a diesel electric is called the 'prime mover'. Always has been since day one. If you were talking about a unit with HEP, and called it a motor.... which one are you talking about???? The prime mover or the auxillary diesel unit?? It does make a difference. No need to change well established railroad terms for your own personal gain, or what the public thinks is politically correct.
Not to mention you confuse the bejeebers out of folks who do know what they are talking about. (Exceptions understandably made for newbies who havent learned the terms yet. We all start somewhere)
Cheers!
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