Why has GE never had to build a 20 cylinder prime mover to achieve higher horespower, but EMD has had to build two (SD45 and SD80MAC) to do so? Even now, GE gets more HP out of a 12 cylinder GEVO than EMD does with a 16 cylinder 70ACe. What does GE know that EMD doesn’t?
It isn’t just a matter of the number of cylinders;
The 20 cylinder 710 is more powerful than the 16 cylinder FDL or the 12 cylinder GEVO, however.
The two sixteen cylinder engines, the GE HDL and the EMD 265H were both rated at the same 6000 HP. The experimental EMD 12-265H was the same power as the 12 cylinder GEVO. EMD chose for good reasons to sell the 16-710 instead, not least because that’s what the customers wanted.
EMD have an experimental 12 cylinder four stroke engine and it is expected that this will develop 4500 HP.
In export locomotives, an Alco 12-251 developed 2000 HP and was a competitor with the 16-645E, and had the advantage of generally lower fuel consumption, but the EMD outsold the Alco (except in India, where the ALCO could be built locally).
It is true that the 20-645E3 was necessary to match the 3600 HP of the FDL16, but the GE engine was not more successful than the EMD. At the time many more 3000 HP locomotives were built than 3600 HP.
The 20-710G3 was more powerful than any GE engine of the time but only sold a few examples.
In general, EMD engines last longer than GE engines. In time the cast crankcase of the GE FDL cracks and requires replacement, after ten to twenty years depending on the duty cycle. EMD 645 engines have lasted more than 40 years and many are still in service. These older engines might not be as economical or emissions friendly, but they still work.
M636C
A lot has to do with cylinder bore, stroke, and RPM of the engine.
Although GE never built a 20 cylinder version of the Cooper Bessemer derived FDL engine (the engine line used in their road locomotives until the advent of the HDL (used in the AC6000CW) and its evolved cousin the GEVO engine), they did build an 18 cylinder HDL test engine. this was supposed to be rated at around 7,000 HP (though I imagine it’s North American locomotive rating would have been about 6,750 HP).
The new EMD 12 cylinder Tier IV compliant engine will probably have a rating of 4400-4500 HP in locomotive service so it will be comparable to the GEVO.
Offhand guess: the 12-cyl GEVO has more displacement than the 16-cyl 710.
The 710 displaces 11.6 litres/cyl vs 15.67 for the GEVO. Doing the math reveals that the total displacement of the EMD is 185.6 litres vs. 188 litres for the GEVO.
Stated design criteria for the GEVO indicates that the 12 cyl was designed for the same output as a 16 cyl. FDL.
At the time of its’ creation, the 20-645 was a technological tour de force.
BTW, the current 16-710 can produce 4500-4600 hp into the generator.
CPM500
Most of the GEs run 150 RPM faster (1050 RPM) than the 900 RPM EMDs also.
Randy
I though that 2 strokes of any kind (diesel, gas) run higher rpms than 4 strokes.
VGN Jess
The Crossley HST, a two stroke V-8 with exhaust pulse pressure charging, best known as the original engine for the Irish CIE Class A and the British Rail Metrovick Class 28, ran at 625 rpm. These were replaced by EMD 12-645E engines in the Irish locomotives. The big marine diesels from Sulzer and MAN B&W turn at about 120 rpm.
The MTU 4000 runs at 1800 rpm and other four strokes run at 2100 rpm.
It is more difficult to design a two stroke to run at a high rpm than a four stroke which of course has a full induction stroke to fill the cylinder.
M636C
General question - since the two engines have similar displacements, but the 710 has twice as many power strokes (at the same RPM) as the GEVO, why isn’t the 710 considerably more powerful ?
Presumably the effective stroke length of a two-stroke diesel is less than on a four-stroke, due to the ports in the cylinder wall being uncovered for part of the stroke ?
The 710 is more comparable to the later models of GE’s FDL engine (used in the C44 series locomotives in 16 cylinder form) than it is to the GEVO, which;as other posters have pointed out) is a larger displacement engine which runs at higher RPM’s.
Gentlemen,
Unmentioned is the realization that no other builder developed a V-20. Unmentioned is the fact that bunches of V-20s, when involved in “rebuild” programs were “lobotomized” and became V-16’s. Unmentioned is that the 645 and 710 marine app. V-20’s haven’t the RR app. V-20’s problem, last time I asked, anyway.
The problem was the supports in the cranckcase and the bearings for the crankshaft that they held and the guidance and restriction against weird wiggling crankshaft contortions, did not prevent.
A tug boat hull, and an SD45 at 70 mph,…this does leave room to ponder…
Also…let’s grant that the cylinder size is about 75 percent 'tween the 2-cycle and 4-cycle, and that the engines operate at max. governed RPM, between 935 and 1050 revolutions a minute.
Question: Pertaining to locomotive’s diesel engines, with more power strokes a minute and cylinder size not greatly variant, 2-cycles…vs 4-cycles???
Too many variables?..
Most of the v-20 SD45s I’m aware of had their power output dropped on initial rebuild(SP units in particular), but no Cylinders were removed. They were still pure V-20s. Also, EMD is the only Manufacturer of Locomotives that has done V-20s (that I’m aware of) but they are not the only manufacturers of V-20 Diesel engines. So I’m not sure what your point is there. In recent years they’ve been rebuilt to SD40 specs with V-16s, but that has less to do with the unreliability of the V-20 645 and it’s crankshaft and more to do with not needing the 600 extra HP while burning the extra fuel. They needed 3000HP V-16 645. None of the V-20 710 SD80s have been modified that I’m aware of. They are still full power 5000HP 20 cylinder units.
There are quite a lot of 20 cylinder MTU 4000 engines in locomotives in Australia and New Zealand. Many large catamarans have four Ruston 20RK270 engines, derived from the old English Electric RKC locomotive engine with the bore increased from 254mm to 270mm. These could have been fitted in a locomotive (a large locomotive admittedly) but there wasn’t much call for a single engined 10 000 HP locomotive around the year 2000… Some British locomotives, class 37/9 were fitted with 2500 HP inline six cylinder engines of this type.
The problem with the 20-645E3 was torsional vibration. The long crankshaft twisted, rather than bounced about. This is always a problem with long crankshafts and is hard to fix since the diameter is fixed since you want to use the same bearings, connecting rods and crankcase components. The 20-645E3 had a torsional damper which was designed to absorb these vibrations before they built up enough to cause problems. The torsional damper did not work as well as expected. Apparently EMD regarded the damper as private intellectual property and it was not able to be taken apart for maintenance. I saw correspondence from the Danish State Railways where they took
There’s probably a limit to how much a harmonic balancer out on the end of the crank can accomplish – it will certainly help damp out some critical-speed ‘torsional vibration’ buildup, but having progressively less damping effect on the torsion of each main farther away from it…
What would be interesting to see is a statistical analysis or graph showing the frequency of breaks vs. each main bearing location: is there a ‘preferred location’ for breakage relative to where the damper is located?
My own opinion is that there were indeed two factors here: the ‘inadequate’ bracing of the mains, and the inadequate torsional harmonic damping. I would expect any lateral flex of the crank to couple with harmonic torque fluctuation, perhaps at nodes corresponding to one or more main-bearing locations, and the combination of torsion and lateral bending at such a location would (in my opinion) greatly augment the likelihood of either a crank breakage or generation of stress raisers in the crank structure predisposing it to early failure. That would explain (again, to me) why strengthening the crankcase internals might have caused a great decrease in the incidence of broken cranks, as efftenxrfe indicated.
I’m sure at some point the technical reasons for the crank breakage problem on the early V16 244s was discussed here – my understanding is that this was a torsional issue related to firing order. Can anyone
The issue with torsional vibrations reminds me of a paper on the www.enginehistory.org website, “The Liberty Engine and Torsional Vibration” by Robret J. Raymond. The designers had for some reason picked a 45 degree bank angle for a V-12, with the result that the Liberty Engine became infamous for breaking crankshafts. Resolving that issue is what kick-started the study of piston engine torsional vibrations in the US.
The V16 244’s were presumably 45 degree Vee’s as was the 251’s (correct for 16 cyl engines), so bank angle can’t be blamed for crank breakage.
The 20-645E3 engine’s crankshaft probably had a lot of vibrational nodes in its operating range, which also makes me wonder how much benefit a harmonic balancer would have on that engine. Your comment about crankcase stiffness (or lack thereof) coupling with the crankshaft seems plausible.
GM made some 24 cylinder diesels for the USN during WW2 with a one-piece crankshaft. One of these engines was at the Diesel Engineering School at Cornell in the latter part of WW2 and my dad said the crankshaft broke about the time he was there. What impressed me was the cost of replacing the crankshaft, tough I don’t remember enough of the details to say it was broken by torsional vibrations.
- Erik
The information about the V-20s crankshaft torsion situations, convinces me that the job title of (locomotive) Engineer, I’m one, was not accurate; locomotive driver…not an engineer…
Driving forward, another V-20 quirk…I don’t know if it’s related.
A graveyard, or shipping point, of defective locomotive parts behind the Roseville Diesel Shop, seemed to sprout as if they were spring weeds, cylinder liners, called, I recall, power assemblies, this in the early 70’s. I mean it looked like a college fraternity after a monumental “kegger.”
A Foreman said that the cylinder near the upper limit of its piston’s travel “scored” the liner and went far, unproven, but close to causing engine shut downs.
Scored: scraping, irregular grinding,
What was happening with these engines?
The power assemblies for the SD45s are the same as the power assemblies for the SD40s, SD40T-2s and SD45T-2s/ All 645E3 I can’t really answer your actual question, just wondering if you meant to say that only assemblies out of the 45s were back there. SP did have a reputation of riding em hard and putting em away wet. as it were. I feel like every video I have that talks about Donner or trains up to Oregon has some segment discussing a train with like 5 units on front one of which is failing. And it could have been any of those models. Of course most of those videos are from the late 80s/early 90s after GRIP II.
YoHo 1975, to apply a bandage to my wounded remarks, over years walking that route, there were usually a few liners stored there.
What I’m talkin’ 'bout is a sudden increase to over a dozen assemblies stashed on the scrap metal lot. This might help: This happened within months of the initial order of SD45T-2s arriving from La Grange. It also seemed to me that a lot of them were in the shop on repair tracks (differing from periodic inspection tracks) and that there were a lot waiting to get in the shop.
It’s plausible to guess that any 645E3 liner fit any 645E engine, smallest to biggest?
You used a phrase that I could not understand, so please help this city boy who developed allergies to any place not-city, help me understand, what may has well have been written in Sanskrit, what in this world (I’ve no reference to the meaning) does “put them away wet” mean. Does it mean wash the locomotive and let it drip-dry on a maintenance track. As a hostler, I did that in the late 60’s.
BTW, We, SP, has had on heavy grade territories, tonnage limits and, later, max number of “operative” locomotive axles limits on the head-end of trains: 24 axles on non-unit trains, 30 on unit-trains, 8 on the rear end…I wanted to write “behind the caboose.”
5 units on the head end of a Mountain train (Donner), not likely that all were pulling, 'cause of rules and physics, not always mechanical or electrical ptoblems…