• GP50

  • Discussion of Electro-Motive locomotive products and technology, past and present. Official web site can be found here: http://www.emdiesels.com/.
Discussion of Electro-Motive locomotive products and technology, past and present. Official web site can be found here: http://www.emdiesels.com/.

Moderator: GOLDEN-ARM

  by ricebrianrice
There is a high nose Norfolk Southern GP-50 here in Binghamton. What a screwy looking unit.

Anyways, what is a GP50? What are the differences say to a GP-40, etc.

  by westr
The GP50 is a 3,500 horsepower model, vs 3,000 horsepower for the GP40/GP40-2. They both use 16 cylinder 645 engines and the GP40-2 was still in production at the same time as the GP50. The external differences are subtle: the main one is that the radiator grilles are taller on the GP50 than the GP40-2. The exhaust/dynamic brake area is also a bit different, though the exhaust stack is hard to see and not all have dynamic brakes. There may also be some differences in the hood door layout. Earlier GP40-2s from the 1970s have other differences like different fans, grilles and blower duct.
  by ricebrianrice
How is the extra 500 hp created.
  by v8interceptor
ricebrianrice wrote:How is the extra 500 hp created.
The extra 500 HP was achieved by changing fuel rack and engine settings(higher compression, higher RPM's, ect.)...the EMD 50 series had reliability problems as a result trying to squeeze the extra HP out of the 645 engine. It's no different than with automobiles where the same basic engine can be tuned up to produce more power in a sports model...
The only complaints I ever had about a 50 Series loco, was the faulty Super-Series electronics package. The ground radar never seemed to work, and although those extra horses might have looked good on the Blue Card, the "seat of the pants" told you, you were in a sub-par 40 Series instead. They do make spectacular rail grinders, though........... :P
  by Allen Hazen
"Spectacular rail grinders"
That's a line that will keep me smiling for a while! (Maybe they could be used usefully for that purpose if you also had a REAL SD-40 to tow the 50 series backwards? (Grin!))
Let's say it, all together now: "Synchronous Wheel Slip"......... :-D OR, you could just put that 50 anywhere in the consist, run 'em up to 8, and set a minimum. Super Series will do the rest!!! :P (Lorams' got nothin' on Super Series)
  by ricebrianrice
So it sounds like they were not a very popular engine.


What is "Super Series"?
  by QuietGuy
The GP50 was a slight improvement over the GP-40 & SD-40 because of the slip control. Also the horsepower of the 645 engine was increased due to several minor improvements to various components of the engine (fuel injectors, rods, heads, etc). However the 710 engine was in the final test stages and ready to be released, so the SD-60 & GP-60 were ready to take its place. The 710 brought the locomotive to the 4000 Hp class. Later versions are 4300 Hp standard and 4500 HP for some designs, but the 4500 HP are the limit for that crankcase design. I am talking about the 16 cylinder version. The 20 cylinder 645 put out 4000 Hp, but the first batch released had crankcase problems and early failures.
These were fixed but the damage was done - no railroads wanted them anymore. The 20cylinder 645's went into the SD-45 locomotives. The funny thing is that the 20-645 became a workhorse of the Marine industry and Power industry - they wanted the higher Hp and those engines have proved to be very reliable.

Because of the 20-645 problems no railroads wanted the 20-710 engines except for the batch sent to Conrail in the SD-80's. Those have also proven that the 20-710 is a reliable engine with 5000 Hp.
  by Allen Hazen
When you say "4500 HP are the limit for that [viz, 16 cyl, 710 engine] crankcase design," is there a particular limiting factor? My recollection (from a "Railfan and Railroad" series of articles on the SD-45 some years ago) is that one of the things done to make the 20-645 a reliable engine was to increase the area of the welds holding the crankshaft supports to the floor of the crank case: suggesting that one major problem had been the lateral movement (vibration) of the crankshaft being more than the structure could support.
  by QuietGuy
In the EMD experimental test cells the 16-710 engine was run up to 6,000 Hp but that was just to see what it could do. The CN (I think) had the 4,500 Hp engines and as I remember after 6 years of running they all started to breakdown and needed to have the major overhall. CN wasn't happy that they needed the rebuild so soon, but as it turns out it was predicted as the time that this would occur and there was some wording in the guarantee that the rebuilds would be required after xxx number of Megawatts of power generated. Several engine structural parts started to have fatigue failure type cracks as was predicted. CN used those locomotives to the maximum and their operating conditions of long runs at high power got the maximum they could out of those. The 20-710 is used to generate 5,000 Hp more comfortably lower Hp per cylinder keeps the stresses down.

You are right about the 20-645 failures - the problem was fixed by not just larger, but different welds on the crankcase. These failures never occurred again on the marine and industrial power uses of the 20-645 and many of those engines are still generating power in good form. They never had those types of failures on the 20-710 but the reputation of the 20-645 prevented the RR from wanting them, until Conrail tried them. Modern computer stress analysis with more powerful computers has pretty much eliminated those types of stress failures from occurring nowdays. The only problems come when the welds aren't made to the specifications or with poor techiques - then those pesky fatigue failures pop up again.
  by Allen Hazen
Thanks for the reply! "Fatigue failure type cracks" seem to be a recurrent culprit for mechanical disasters: cf. the De Havilland "Comet" airliner. As a non-engineer, my image of mechanical engineering is that most of the time it is concerned with the grossly observable properties of materials-- how stifdf are they, how hot can you heat them before they lose their strength-- but obviously the subtler properties of metals -- how do their structures change, at a molecular level, with long-term repeated stress -- are also relevant!

I take it the CN locomotives you refer to are the SD-75: CN bought them in 1996, and in 2002 there was an announcement of a major deal between CN and EMD (or whatever the London and La Grange company was called in 2002) for the rebuilding of all their 710-engined locomotives (SD-60, SD-70, SD-75): six years.

The SD-75 was apparently only ordered by CN and Santa Fe. It seems to be "officially" rated at 4300 hp, but I remember mention being made of a 4500 hp rating when they were on order. ... The current SD70-2/SD70ace is apparently rated at 4300 hp. Did this involve further refinement of the engine design, or is the (roughly) 4% reduction from 4500 to 4300 enough to give a major improvement in engine life?
  by QuietGuy
Fatigue failures are an art that many people have received PhD's by the varied aspects of their occurance. However, as it turns out for steel, if stresses are kept below certain levels, the failures will not occur, or will not occur within a reasonable time frame, like say 35 years of service. This does not occur for aluminum, brass, some other metals or composites - lower stresses increase time to failure, but fatigue failure will always eventually occur for those materials. All I know is that we did everything we could to reduce stress and/or cycles to reduce the oportunity for fatigue failure cracks to expand. The elimination of fatigue failures is pretty much an art and a lot of investigationaly work and experience. The international marine standards took experience and created rules for allowable stresses in various parts of an engine and ship, by following those rules, you will be able to have your marine component approved for use in the sea and the vessel will be insurable.

As for the SD-75 engines, there were several variations in the models sold (EMD - Every Model Different). I do know that some of the engine components for which I had design responsibility failed due to fatigue. When we gathered all the information about the locomotives, the power the engines generated in five years on the 4500 Hp engines was what a 4300 Hp engine would be expected to make in ten years. This is to say that the railroads were using these locomotives about as efficiently as could be done, short of running them at full power 24/7 for several years. While the RR was unhappy about the premature wearing of the engines, the engines gave them the power (and low failure rates) that was contracted in the sale, except the the time occurred sooned than expected because the locomotives had been used so effectively that they needed maximum power. At 4300 Hp those failures did not occur, even after more than ten years or equivalent amounts of power generated.

Most failure rates (failures vs time in service) for a part are U-shaped, i.e. there is a relatively high rate for parts with little service time (called infant failures - say only a few days or weeks in service), then there are few failures for one to five years of service, finally there are many failures at the end of useful service life, say after five years. The maintenance instructions would call for replacement of parts before the failure rates would increase depending on service life. We found out for those SD-75s that the parts that were failing were at the end of service life based on the amount of power generated, not calendar time.

There are many factors which can contribute to early failure, if the technician building the part was having a bad day and did not assemble and fabricate everything perfectly, it could break quickly. For many things we are never able to determine exactly what constitutes a perfectly (or even acceptably) fabricated part, we just tweaked things until the failure rates dropped to a long enough time duration. This experience would translate into higher prices for our parts, but they lasted longer than the competition.

One railroad Director of Locomotive Maintenance spent a lot of time screaming at us (EMD) about the poor service our parts were giving his locomotives. We had them shipped to our plant to inspect them to see what the problems were - THEY WEREN'T OUR PARTS!! We told him to buy our parts and his failure rates would go away - he was so upset that we wouldn't tell him why those other parts were failing (we did know - they were cheaper) that he swore he would never buy ours again - big deal he wasn't buying ours anyway.
  by Allen Hazen
Quiet Guy--
Thanks! (Now, if you and Preston Cook could co-author a book on EMD...)
  by tomjohn
Isn't (didn't) up rr have(ing) some GPM 50's rebuilt for branch line/yard service ,also how many ?