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 aroun
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.
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 .
= J =
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</
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”!
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…
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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.
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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.
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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.
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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 unders
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 ,
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.
- Erik
Erik,
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 genera
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…
[quote user=“Paul Milenkovic”]
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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.
-
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.
-
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.
-
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 Dieseli
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 earl
That’s the question-- were F3s really “good” for 90% of their 1500 hp rating, at the drawbar? Were PAs really “good” for 96% of their rating, even when new? What were they “good” for at age 1 year, or 3, or 10? Could three PAs ever take 800 tons up 2.2% at 36 mph, as that 5800 dbhp claim implies?
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 efficienc