Good Evening American Railfans, (although I believe that it is still afternoon where you are).
I am a British railway enthusiast, but one with an interest in the railways of Continental Europe as well. I frequently look at, and occasionally contribute to, a German forum similar to this one.
Today, one of the German readers posed the question “which is the largest U.S. built diesel locomotive ever built, and does anyone make a model of it?”
I do not know the answer to this question, but have no doubt that someone ‘over there’ does!
I look forward to your responses, which I shall pass on to the German gentleman who posed the question.
The biggest diesel ever built in terms of horsepower (6600 hp), weight (247 tons) and length (98 feet) was DDA40X Centennial. The biggest in terms of pulling power is SD90MAC/AC6000 - both around 890 kN (200000 lb) of starting tractive effort (DDA40X was around 600 kN - 135000 lb)
I would have to agree on the EMD DD40AX for being the largest single unit locomotive but what about F-units? Some railroads considered an A-B-B-A lashup one locomotive. Such a lashup would be about 215’ long and would weigh roughly 470 tons (940,000 lbs.)
I believe there were Bunker C fuel oil gas turbines, bulit by General Electric in the 1950s and used up to around 1969 when they were replaced by DDA40X Centennials. These gas turbines were rated between 4500, 8500 and 10000 horsepower.
well,it’s the DD40AX there is only one left. I was talking to somebody in Folkston last monday and he said that the DD40AX got hit by a garbage truck so it is in the shops but I think that was a SD70 that got hit
This is probably cheating, but the Pennsylvania Railroad had permanently coupled (drawbar, not couplers), 2-unit sets of Baldwin “Centipedes.” They were considered one “locomotive”. They were about 92’ long per unit, roughly 185’ or so for the pair, and were 2-D+D-2 each. They had four 1500 HP engines for a total as-built of 6000 hp. They were later derated to 5000 HP and consigned to helper service. Built around 1947, retired about 1962-1963. Models are available in both HO and O gage. Now how about a pair of these beasts in 1/32 G-scale…
IIRC KCS had 6000 or 8000hp “locomotives” that were Erie-built sets.
Many early railroads tried this approach (using letters to denote the units in a single ‘locomotive’, e.g. Santa Fe practice). It wasn’t long before motive power people saw the relative pointlessness of leaving some units of a ‘locomotive’ idle while one was being repaired – or of letting the ‘rest’ of the locomotive roam far from the shop by the time the one was fixed. So much easier just to take building blocks and make a consist…
Baldwin had a single-unit 6000hp prototype in the late Forties, slated to use modular V-8 engine-generator sets in racks, over an undercarriage similar to that used on the Centipedes. Rather interesting alternative to a 4-unit F3 set… although I can’t conceive of it working right without much more sophisticated wheelslip control than was available then…
I wonder if the “6000”, had it ever got all eight engines, would have been heavier than a DDA40X? Those frame castings wouldn’t be light! The frame was used on one of Seaboard’s Centipedes when even Baldwin realised that nobody wanted it. It wasn’t as long as a “Centennial”, of course, which is a major criterion of “Biggest”.
I’m almost certain you’d be right. Centennials only had eight axles, Centipedes 12, with substantially greater frame strength as well as weight. I’ve been trying for many years to find out exactly what the weight of one of the engine modules was – I honestly can’t say whether four gensets equals one big 645 with traction generator…
Of course, for many services you still need more than eight traction motors – what I would expect from the ‘modular’ would be two semipermanently-coupled units a la Pennsylvania, with the desired number of gensets in each carbody. Note that this would still be fewer traction motors than 3 C-C locomotives, albeit with better cooling arrangements possible. Presumably it would be practical to start up and shut down the relatively small engines as needed to ‘trim’ the amount of available power for fuel conservation – I proposed something similar (with modular gas-turbine generators) in the early '70s.
By the way – there is a picture in Clessie Cummins’ book of a “Zephyr” carbody with multiple gensets installed. I have never seen an organized discussion of this, or how it worked in practice. There’s a certain bean-counting appeal to using only the amount of engine needed hour by hour to run the train effectively…
The GE gas turbines used on the UP were just that – not diesels. The DDA40X is it, and yes there are a number of models of it. They straighten model track almost as well as the real one straightens real track.
The Centipede was a fascinating idea… always an interesting engineering choice: do you use a number of smaller modular units to do a certain job, or one (or a few – e.g. the EMD E units with two) bigger ones. As overmod says, there is a certain bean-counting appeal to the modular idea, but there were some rather sticky control problems… which are all solvable, but…
Thank you, gentlemen, for the information. These DDA40Xs sound pretty impressive beasties. I shall pass this on in my best German to the enquirer as this seems to answer his query. I am assuming that he means biggest in terms of a single unit, rather than two/three units permanently or semi-permanently joined together.
Can anyone say which manufactures offer, or have offered, models of these things?
I think it was also available in brass, but had a price tag proportional to the prototype (it made my heart skip a beat, but I didn’t have a job at the time I asked). You have to search e-bay or estate sales to find one now. The Athern model is a DD40. The major difference would be that the DD40, if it was every built, would have had a standard EMD cab and the DD40AX had a verson of the wide cab. These are for HO scale, I can’t tell you about other scales.
There are 11 DD40AXs in museums,10 in the USA and one in Mexico.The UP keeps one in thier historic collection,and uses it occasionally when they are short of power.I am pretty sure the Bachmann DD40AX is out of production.
Apart from the “Silver Charger” with the single 12-567, the previous units were twin engined, 1800 HP, mechanically basically similar to ATSF 1A and 1B, and effectively E units, without idler axles (since thy didn’t need steam generators). These were each coupled to a B unit with a 16-201A of 1200HP.
I’m not sure what multiple generators you are talking about, unless you are including the hotel power sets that were fitted in some Zephyrs?
