Maximum Power of Railroad Diesels.

While it seems that steam locomotives reached 6,000 hp quite nicely, and straight electric locomotives have gone up to 12,000 that I know of, it seems that the industry has had trouble going past 4,500 hp on diesels with out serious problems with performance and/or reliability. The most powerful that I know of for railroad diesels, even with problems, is about 6,300 hp for a single engined locomotive. My question is: Just what is the limit for diesel locomotive power? And what are the prospects for improving on that?

Fianlly, does anyone know if there is even a market for more powerful single locomotives, given that railroads do frequently stack locomotives anyway, to spread out the power, etc?

When GE debuted the FDL-16 in the U25B, it was rated at 2,500 HP. Over the course of several decades, they continually increased the FDL's power output, as well as increasing its reliability, eventually peaking at 4,400 HP -- almost double the original rating, and much more reliable to boot.

Could the same thing happen with the GEVO? I honestly don't know the answer to that question, but it strikes me as at least being possible that 20 or 30 years from now the GEVO-12 could be putting out 6,000 HP, assuming that GE is on a continuous path of improved performance and improved reliability, the way they were with the FDL. Likewise, if my theory is correct, one could expect the GEVO-16 to be capable of 9,000 HP at some point down the road.

The wild card is whether the railroads want or need that kind of power in a single locomotive. Right now it appears that they do not, but maybe they will in 20 years...? My crystal ball is broken so I don't know the answer to that. At any rate, if the railroads don't want that much power, the engine manufacturers have little incentive to make it happen. That's the biggest difference between today and what was going on in the industry in the 1960s and 1970s -- which, I assume, is why GE and EMD worked so aggressively to increase their engines' output over the years. If the horsepower race had never happened, it's entirely possible that the FDL (and its EMD counterparts) would have peaked at 3000-ish HP.

Back in 2004 or so, when GE was testing the pre-production GEVO units, it was reported that one was being run at 120% of normal power: not something one would want to do very much, but useful in a test program! So, at least experimentally, the GEVO-12 engine has powered a locomotive of almost 5300 hp.

GE has built locomotives for both China and Brazil with the GEVO-16 engine: somewhere in the 5800/5900 hp range at the rating used in current ES44 units built for use in a country that doesn't (for the moment) want big power.

I don't know if it was actually used in a locomotive, but back in the 1980s SEMT-Pielstick advertised that their 18 cylinder PA6 engine -- rated at 7200 hp -- had completed UIC (Union Internationale des Chemins de Fer: roughly equivalent to the AAR's technical programs for European railways) certification tests: they were obviously hoping it would be used in locomotives!
---
3000 hp was the generally accepted limit for U.S. railroads at the end of the 1970s, even though engines capable of giving more than that had been introduced in the 1960s. Assume similar inertia on the part of railroad managements: we may be in for several more years of 4400 hp locomotives in North America. Sooner or later (as I have been predicting for what seems like rather a long time...) some railroad management is going to decide that fast freight (intermodal between Chicago and Los Angeles, say) will justify locomotives with more oomph. GE an otherr builders will be ready to provide such units when the demand is there.

I'd like to know where the claim of 12000 HP comes from. So far, I've found NP Northerns with 3000 HP at speed...

John_Perkowski wrote:I'd like to know where the claim of 12000 HP comes from. So far, I've found NP Northerns with 3000 HP at speed...

When I went to check my sources for 12,000 hp.... I actually found that I misquoted. While I stand by the hp figures that I cited for diesel and steam engines, the best that I could find for electric is 8,000 hp. The 12,000 was a voltage spec.

At least my original point stands - that while reliable and good performing steam locomotives could exceed 6,000 hp decades before diesels could flirt with such power, and electrics have gone siginifcantly outperformed that parameter, diesels have had trouble exceeding the 4,500 hp mark.

as for electrics the German Baureih 103 was only 20 Hp shy of 10 000 Hp almost 30 years ago

Amtrak's HH8 locomotives are about 8,000 hp on four axles, so 12,000 hp for a six-axle electric locomotive is perfectly do-able.
http://www.railway-technology.com/news/news2167.html
says that China's railways had ordered a large number of six-axle locomotives of 9.6 megawatts power: around 12,800 hp. A Wikipedia list of record-breaking locomotives (hey, if Wikipedia can compete with the Britannica, it can also compete with the Guinness Book of Records!) that I found by Googling "world's most powerful electric locomotives" seems to indicate that these Chinese locomotives are of CC configuration (so: single-unit locomotives) weighing about 330,000 pounds: about 80% of what a large U.S. six-axle diesel weighs.

If you want to see locomotives of this power in the U.S.... ask your fairy godmother to give the BNSF a few billion dollars to electrify the Santa Fe main line!

The key issue is the HP to weight ratio. Each HP brings a cost to a diesel in weight of the prime power (the engine itself).

The biggest issue about high horsepower locomotives is that if you have one engine with 10,000hp as opposed to 4 engines with 2,500 hp each, if you lose the one 10,000hp engine, you've lost 100% of your pulling power. If you lose one of the 2,500 hp engines, you've lost 25% of your pulling power. NS is still pulling coal drags with a couple SD70s followed up with a few SD40-2 High hoods for good measure. Why buy an ultra high power diesel for a lot of money when NS can just keep these old Hi-Hoods on the road as "B-units" courtesy of Juniata and buy SD70ACs as "cab units"?

The key is to make these new engines so reliable that losing one on the road is something that will almost never happen. That's how Boeing was able to build the 777 -- a very large twin-engine aircraft that in the past would have required three or four engines, both for power and for redundancy.

Horsepower is only half of the equation in locomotive performance. Tractive effort is also very important. One of the last posts talked about the HHP8 electric motors having 8,000 hp. That is fine for a high speed locomotive, pulling 12 or so coaches maximum.
In freight service, we have seen an increase in both horsepower and tractive effort. A railroad which ran 4 units sets of SD40-2s, then upgraded to 3 unit sets of SD60s. now 2 SD70MAC units. You will note that the 3 60s have about the same hp as the 4 40s. When the ac units are used, 1/3 horsepower is lost. The ac units can pull the same train, but slower. The AC6000, and SD90MAC were intended for trains where speed counts. I don't know if the absolute number of cars which can be started would differ between the AC4400/SD70MAC, vs. AC6000?SD90MAC. The AC6000/90MAC can just move them faster.
Since the first generation diesels, as power increased, so did the capabilities of the wheel slip controls, and reliability. Eventually the builders will reach the maximum adhesion factors set by the laws of physics, based on their weight for a C-C wheel arrangement unit. If GE and EMD can build a reliable, and powerful enough to replace 2 present ac traction design units, they may have to go for D-D or B-B-B-B wheel arrangements. The present units are at the practical limit for size and weight. We will have to see what the builders can do.

Allen Hazen wrote:I don't know if it was actually used in a locomotive, but back in the 1980s SEMT-Pielstick advertised that their 18 cylinder PA6 engine -- rated at 7200 hp -- had completed UIC (Union Internationale des Chemins de Fer: roughly equivalent to the AAR's technical programs for European railways) certification tests: they were obviously hoping it would be used in locomotives!

Very interesting, thank you for sharing.

Fairbanks Morse Engine makes a licensed variant of the PA6, the Colt-Pielstick PA6B. When I went to FM's ALCo school in Beloit our instructor, who had started with ALCo, remarked the Colt-Pielstick PA6B was dead ringer for the 251 albeit larger. The PA6 has an 11" bore and 13" stroke verses the 9x10.5 of our beloved 251. (For the record, the GEVO is 9.8x12.6.) Looking at the training mock-up of the Colt-Pielstick PA6B on the training floor I did wonder how they would fare squeezing one into the confines of a U.S. long hood locomotive as it is much wider than a 251.

Remember that in the day, F-M diesels had a far wider hood than their contemporaries from EMD.

Here's an end-on view of a GP-7.

Here's a 3/4 end-on view of a Trainmaster

And here I thought FM had wide hoods to keep the Athearn models prototypical.

But seriously folks, the Colt-Pielstick PA6B mock-up was a partial block with no heads installed. The widest part of the block at the top was as wide as the 251-12 with its heads installed. Would a PA6B fit under the commodious confines of an FM hood?

My source for the PA6-280 diesel engine (the SEMT (=French manufacturer) entry in the 1986 "Jane's World Railways") says the engine was 178 cm wide, as compared to the 174 cm width of the GE FDL engine. The Rushton RKC engine (British engine, produced at the time by the British GEC, a company unrelated to the U.S. GE company) was 183 cm -- six feet -- wide, and was used in hood-style locomotives (for, e.g., Australian railways).