When diesels first began to replace steam back in the 40s and 50s railroads had to get used to locomotives of much lower horsepower than the steam engines they were replacing…the early diesels had 1200 to 1500 hp…and they had to be run in consists of three or four to replace one large steam locomotive.
Why was it not possible to build larger more powerful diesels from the outset? Was a 3000 hp diesel not possible in the 40s and 50s…and it took 30 years…until the late 60s to finally build one that is reliable?
Steam fans like to sneer at diesels on that account-- but why would that have to be a disadvantage? If somebody had made a 6000-hp single-unit diesel in 1950, would RRs have flocked to buy it? Even if it worked?
I assume it’s true a 3000-hp diesel would have been a challenge in 1950-- but as long as nobody needed much more than 6000 hp total in one diesel consist, why would the RRs care that they couldn’t buy 3000 hp in one unit?
The limitiations can be many. technology back then wouldn’t have supported a lot of what we have now. For example, maybe they might have developed a 4000hp engine back then, but would there be a generator or traction motors that could handle it? Even when the fairly modern units such as GP40s came to be, the horsepower was a lot for only four motors. A locomotive is a machine that has to have everything matched up to work properly. Even today, 6000hp in one unit has been a problem and generally not favored. The idea behind diesels from the FT onward was that you could put several together and get the job done efficiently, in the case of steam the diesel was more efficient even with four units as opposed to one.
In a word, yes. The horsepower for the FT was originally limited 1350 hp by the electrical equipment. With upgrades in wire insulation they could get 1500 hp out of the engine’ Todays 16 cylinder 710 engine can be thought of as a bored and stroked 567 with the same bore spacing as in the various sizes of Chevy small block all with the same bore spacing.In the time between 1938 and 1985 there have been many improvements in materials and lube oils that allow the engine to run faster at a heaver load. The main bearings on both 567 and 645 are identical, that is the part numbers for your 567A have been replaced with the latest 645 numbers. In its time the 567A was maxed out on horsepower with a reasonable expectation of a long service life. The 567D4,first cousin to the D3’s used in GP35’s were used as peaking generators running at 900 rpm and at 2800HP (2000KW) with a shorter power assy. life and problems particularly with port framing and port clipping. These units with 645 pa’s with laser hardend liners will last forever at the same rating.
Traction generators were/are pretty much limited to 2500HP, the 8500HP UP Big Blow used four traction alternators geared to the output of the turbine. Traction alternators, which allowed for greater than 2500HP, were not practical until the development of the high current silicon rectifier in the early 1960’s.
DC traction motor technology has advanced since the time of the first diesel locomotives. One of the most important improvements was the use of kapton for electrical insulation allowing for higher maximum winding temperatures. As an example, 8 GE-750 motors were required to produce 5500 HP in the Little Joes of the late 1940’s, where only 6 GE-750 motors were needed to produce 5400 HP in a design from 1969.
AC traction motors are a relatively recent development for US locomotive use (first work in the US for transit sized motors was in the late 1960’s). These mainly became practical after the development of the Gate Turn-Off Thyristor (GTO), and became even more practical with the development of the IGBT. The GTO is slightly more efficient than the IGBT, but the IGBT is much simpler to drive.
The early diesel engines were not anywhere near being up for the task of producing 6000 HP from a single locomotive. The Alco PA was one of the first locomotives to produce 2000 HP from a single engine and it had a lot of reliability problems. Fairbanks-Morse had engines capable of putting out 2400 HP in the early 1950’s but reliability wasn’t there until later in the decade (i.e. Trainmaster).
Another thing to consider is that EMD(and Alco, etc.) marketed their early units as “modular” locomotives (although they didn’t use that term back then). When an EMD rep. called on a RR’s chief mechanical officer he wasn’t trying to sell single unit FT’s to replace a 4-8-4s or mallets, he was offering A-B-A or A-B-B-A sets which many RR’s thought of as a single locomotive (the numbering scheme on may RR’s F’s and other cab units reflected this where a three unit set of F’s would have been numbered 101A,101B,101C rather than 101-103). So it was not a case of replacing 4000HP with 1350HP.
I believe some locomotives had AC alternators (or Dynamo, if you prefer), and had it converted to DC for the motors. I know as early as the GP38s there was an experimental AC model. Its not a brand new technology to railroads, but one thats been perfected for use in modern engines.
All machines improve over time. We learn why the machine fail and come up with solutions to keep the failure from recurring. We learn how to make the maching work more efficently. We learn how to construct the machine at a lower cost…and so it goes.
EMD had an over forty year run replacing four units with three as power improvements were possible. What are the limits? A number of factors such as weight, length, cost, operating practice (are two smaller units more versatile), track restrictions, and a variety of other factors.
EMD began offering AC main generators in 1965 along with the introduction of its 645-series prime mover. The AC is rectified to DC by diodes immediately after generation, and the control and power circuits are DC. This method continues as the standard today for EMD and GE for DC-drive locomotives. Alco offered it also, beginning with (I think) the C630.
The GP38AC was not experimental, but offered as an option to the GP38DC. The AC main generator cost more to purchase but was less expensive to maintain.
Alco actually beat EMD to the punch with the C630, “The Joneses already have one”. When the 645 engine was introduced, the GP40, SD40, SDP40 and SD45 were equipped with main alternators and rectifiers. The GP38, SD38 and the two switcher models used main generators. Main generators had reached their size limit with the GP/SD35 and the C628 so the use of main alternators had become a necessity.
EMD equipped F9A 462 with a main alternator as a testbed about two or three years prior to the introduction of the 645 line.
Thanks for confirming the C630 date. I wasn’t sure.
Interestingly, when I worked in a locomotive shop, it was always “main generator” whether it was A.C. or D.C. You looked in the EMD 190 parts catalog, the AR10 alternator was a “main generator.” But now I see that some in the industry are starting to call it a main alternator – VMV and EMD both use that on their websites now. Ugh.
EMD was often not the first out the factory door with an innovation, because they had the market share, thus could test more thoroughly, whereas the competitor had to be first out because they desperately needed market share. In other words, he without the market share has to take bigger gambles. This is consistently the case throughout the heavy capital goods industries.
It was that way when I was in Mechanical, too. Sometimes, EMD would refer to it as the “Traction Alternator” - which I liked. Sometimes we just referred to it by it’s model. You’d just call it the “AR10” or “D32”. There was no confusion.
I have forgotten some of the EMD colloquialisms over the years, but just happened on a VRE engine (not locomotive) rebuild spec. They actually used the term “ice cream box” for the lube oil strainer housing and “Michiana tank” for the lube oil filter housing. (was there a company called Michiana who was a supplier to EMD once upon a time?) Actually, VRE is just looking for a “PACO”
You are bringing back not so fond memories of black grease that never washed off, skinned knuckles, a scar I have in my head from creasing it on the bottom of an F7 electrical cabinet door when I sat up to reach for a megger, and a 4th finger that 20 years later is still not quite right after an SD40 door slammed shut on it.
Well, you have to think. In the 1800’s people didn’t have microwaves. The tecnology just wasn’t there. Still though some railroad’s, not the N&W, were ready to get rid of the old steamers as soon as the right diesels were created. Remember that diesels were being built in the 30’s, thay just wern’t high enough horsepwoer for road freight service. Finally when EMD came out with the FT locomotive the railroads had never seen anything like it before. Kind of like what the Right Bro’s. would do if thay saw an A380. Early diesels were big machines, compare this to a cell phone of the 70’s to todays Razor phone, the prime movers were bigger but still didn’t have as mutch horsepower. Today’s GEVOS are smaller than the 657 prime movers, I think that’s what thay are called, whatever’s in a dash 9, but produce the same horsepower. The bottom line is that the tecnolagy just wasn’t there.
It is more appropriate now to call them Alternators, or at least AC generators. On SD70M-2s and SD70ACe locomotives EMD has removed the Rectifier Assy, not just from inside the case of the generator, but even from the same compartment of the locomotive. It is now in with the switch gear.