Some railroads are dispatching some trains based primarily on fuel economy. But not all railroads all trains. Intermodel and those railroads that are both intermodel heavy and approximate a one-speed operation figure heavily in the overall picture. Despite rising fuel costs, crew wages and interest and/or depreciation on rolling stock capital costs are still a major expense.
GP40-2 One last thing John. I do for the apologize for the first post. That's why I edited out my comments. ... Have a good evening.
One last thing John.
I do for the apologize for the first post. That's why I edited out my comments.
...
Have a good evening.
Apology accepted, no hard feelings. You have a good one. John R.
I hope this thread gets back into a useful discussion soon.
Crandell
GP40-2 Oh, I almost forgot the best part. You see John, GE Transportation in is constantly being contacted by "railfans" wanting to know every detail of the current operation. Stuff like Engineering, performance, and financial data that GE only shares with actual customers.
Oh, I almost forgot the best part.
You see John, GE Transportation in is constantly being contacted by "railfans" wanting to know every detail of the current operation. Stuff like Engineering, performance, and financial data that GE only shares with actual customers.
Well Railfans,
He did forget the best part!
The part good ol' GP40 left out is that a GE 4 stroker takes almost a minute to build enough amps to get out of its own way. By then the EMD's have said bye-bye! In other words knock those GE's out of DB running 40mph at the bottom of a dip and open them up and they will be hard pressed to run 30 near the top of the hill. Do the same with an EMD and you are still running 40 at the top.
.
BigJim Like I said in another post, HP can be expressed in many a form and to many a newbie you can BS your mechanical engineer way to stardom. Then again you can't fool all of the people all of the time.
Like I said in another post, HP can be expressed in many a form and to many a newbie you can BS your mechanical engineer way to stardom. Then again you can't fool all of the people all of the time.
What's with the attitude tonight, Jimbo. Didn't the NS supply you with enough Krispi Kremes while you hardly worked today?
GP40-2 BigJim: The net traction HP is the same at 70 mph as it is at 10 mph. The only thing changing is the rolling resistance and air resistance at 70 mph, HP for traction may not change but Tractive Effort certainly does. Never said it didn't. So your point is exactly what?
BigJim: The net traction HP is the same at 70 mph as it is at 10 mph. The only thing changing is the rolling resistance and air resistance at 70 mph, HP for traction may not change but Tractive Effort certainly does.
The net traction HP is the same at 70 mph as it is at 10 mph. The only thing changing is the rolling resistance and air resistance at 70 mph,
HP for traction may not change but Tractive Effort certainly does.
Never said it didn't.
So your point is exactly what?
I do for the apologize for the first post. That's why I edited out my comments. However, I don't agree with your presentation or the methodology in it. I'm just leaving it at that and will not comment on any further posting on this subject.
oltmannd Basic physics rule the day here. Power = force (tractive effort) x speed. Where you have constant power (diesel locomotive), as speed goes down, force goes up. Where you have constant force (steam locomotive), as speed goes down, power goes down. In frt RRing today, where there is huge emphasis on fuel economy, RRs are generally dispatching on the drag rating of the power and living with the resultant running times. Even if you had a steam locomotive with the same tonnage rating as a diesel electric AND it the specific cost for fuel was equivalent ($/ft-lb), the diesel electric would still win the contest. The lower avg HP/ton would mean fewer ft-lbs of work to get the train over the road.
Basic physics rule the day here.
Power = force (tractive effort) x speed.
Where you have constant power (diesel locomotive), as speed goes down, force goes up.
Where you have constant force (steam locomotive), as speed goes down, power goes down.
In frt RRing today, where there is huge emphasis on fuel economy, RRs are generally dispatching on the drag rating of the power and living with the resultant running times. Even if you had a steam locomotive with the same tonnage rating as a diesel electric AND it the specific cost for fuel was equivalent ($/ft-lb), the diesel electric would still win the contest. The lower avg HP/ton would mean fewer ft-lbs of work to get the train over the road.
You and I both know this. But to some people this steam vs. diesel-electric thing is a religion. Either you a a drinker of the Kool-Aid, or you are an infidel non-believer.
We are both just wasting our time trying to explain any of this.
LDPorta The graphic is just a representative graphic. John Rhodes
The graphic is just a representative graphic.
John Rhodes
What good is a "representative graphic" when it doesn't really represent the performance of an actual ES44AC, especially at high speed?
Also, the "representative graphic" for the 2-8-8-2 is based on a locomotive that has never existed.
And somehow your don't see a problem in any of this?
LDPorta At one point the Starting and Continous Tractive Effort ratings where listed for both the GE ES44AC and DC on GE's website. This is what I used, however the information appears to not be listed anymore.
At one point the Starting and Continous Tractive Effort ratings where listed for both the GE ES44AC and DC on GE's website. This is what I used, however the information appears to not be listed anymore.
You see John, GE Transportation in is constantly being contacted by "railfans" wanting to know every detail of the current operation. Stuff like Engineering, performance, and financial data that GE only shares with actual customers. Well, they got so tired of the constant phone calls and e-mails, PR decided to put a Railfan information section on Transportation's web page. The only problem was it is GE Corporate policy not to discuss performance data on current industrial products (such as the ES Series) other than with a customer. So, some "information" was put up on the ES, but nobody said it had to be accurate, actual customer test driven data.
I hope you really didn't use that stuff for a professional presentation, because that was not its intent. After a while, it was decided keeping that part of the web site was just too much work, especially since it had nothing to do with customer service, and the whole thing was pulled down.
GP40-2 ... Seems pretty shady for you to represent a GE product in your presentation, when you publicly admit you have no actual data on said product. ...
... Seems pretty shady for you to represent a GE product in your presentation, when you publicly admit you have no actual data on said product.
GP40-2: The graphic is just a representative graphic. RTC: Berkeley Simulation Software's Railroad Traffic Controller is preloaded with the GE locomotive in it and many other diesels as well. So the RTC comparison was based on industry data and not data I had to estimate.
-Don (Random stuff, mostly about trains - what else? http://blerfblog.blogspot.com/)
BigJim The net traction HP is the same at 70 mph as it is at 10 mph. The only thing changing is the rolling resistance and air resistance at 70 mph, HP for traction may not change but Tractive Effort certainly does.
beaulieu There is no reason to believe that GE's don't have the same limitations even if the exact speed at which this happens is not the same...
There is no reason to believe that GE's don't have the same limitations even if the exact speed at which this happens is not the same...
GE's use a completely different, more advanced, and much higher performance inverter system than EMD. Comparing the two is like comparing a 1932 Chevy to a 2011 BMW.
Haven't any of you guys wondered why the MBTA, an all EMD DC operation up to this point in time, specifically is getting GE based AC technology for their new high speed, high power commuter locomotives, which are a prelude to the next generation AC AMTRAK locomotives? I give you a big hint: it isn't the GE's are cheaper either (over $5 million per locomotive), it has to do with the performance of GE's electrical system at high speed.
LDPorta My ES44AC DBHP data is derived/estimated from data in an EMD Product Application Guide since I can find no source for actual DBPull or DBHP data on the GE ES44AC.... John Rhodes
My ES44AC DBHP data is derived/estimated from data in an EMD Product Application Guide since I can find no source for actual DBPull or DBHP data on the GE ES44AC....
I'm curious, since you don't have access to actual GE test data, what lead you to believe that you could use EMD data on a GE product that uses a completely different inverter system? What exactly did you use from EMD, and what was your methodology to transform EMD data into your opinion of GE product proformance?
Also, since you don't have actual test data from GE (I know they won't give it to you since it is GE's corporate policy not to discuss engineering data with non-customers), why use an ES44AC in your example? Why not use the EMD product you claim to have got the data from? Seems pretty shady for you to represent a GE product in your presentation, when you publicly admit you have no actual data on said product.
My background ?
Dual Major in Mechanical Engineering and Physics undergrad+ Masters in Mechanical Engineering, both from two Top 10 Engineering Universities. Plus, going on 33 years experience in the industry.
I am coming late to this discussion as I rarely read the Steam and Preservation board. In reading the SD70MAC shop manual it talks about operation of the locomotive at speeds where main generator (alternator) output is at maximum voltage. It states that if the motor's rotational speed increases the rotor's inductive reactance will increase reducing the current flow in the rotor and the torque of the motor. This means that at higher speeds the drawbar horsepower must fall once the inverters reach their limits and the main alternator reaches maximum voltage. There is no reason to believe that GE's don't have the same limitations even if the exact speed at which this happens is not the same. What the manual says is that once maximum high power switching speed is reached, and the Main Alternator is supplying its maximum voltage, operation of the motors at higher speeds will result in a reduction of motor torque.
GE's high-TE ES44AC -- which some railroads have acquired instead of the conventional version -- has an axle loading of 72,000 pounds and a starting TE of 200,000 pounds. Probably more significantly, its traction control software can shift TE from low-adhesion axles to high-adhesion axles, up to a per-motor limit of 36,000 pounds. So even if rail conditions won't allow it to reach the 200,000-pound TE limit, it will get closer to that limit than it would if it had the conventional per-motor limit of 30,000 pounds. Knowing next to nothing about steam locomotives, I have no idea of the probability of the 2-8-8-2 reaching its180,000-pound maximum TE (which I gather would equate to about 31.5% adhesion); however it is not unusual for the high-TE ES44ACs to reach their 200,000-pound limit (which equates to about 46% adhesion) when that level of TE is needed.
JayPotter I have two questions. . . Was EMD also the source of the ES44AC tractive-effort data, particularly for speeds below 10 mph? What are the 2-8-8-2 driving-wheel axle loadings? Thank you.
I have two questions. . .
Was EMD also the source of the ES44AC tractive-effort data, particularly for speeds below 10 mph?
What are the 2-8-8-2 driving-wheel axle loadings?
Thank you.
On the 2-8-8-2, my modern steam locomotive source said they locomotive would need to be ballasted to reach a 71,500 pound axle loading (standard 286k).
Thanks for the questions, John Rhodes
GP40-2 oltmannd: I don't have any hard data, but I did participate on drawbar HP tests of C36-7s and SD50s on Conrail's Boston Line (many moons ago!)... ... Every ES44AC I am familiar with is producing close to 4000 DBHP @ 70 mph. CSX's GEVO-16 engined AC6000s are producing 5600+ DBHP @ 70 mph.
oltmannd: I don't have any hard data, but I did participate on drawbar HP tests of C36-7s and SD50s on Conrail's Boston Line (many moons ago!)...
I don't have any hard data, but I did participate on drawbar HP tests of C36-7s and SD50s on Conrail's Boston Line (many moons ago!)...
Every ES44AC I am familiar with is producing close to 4000 DBHP @ 70 mph. CSX's GEVO-16 engined AC6000s are producing 5600+ DBHP @ 70 mph.
GP40-2:
I am interested in seeing your data. And also you haven't said what your credentials are to prove I am wrong, unintelligent or don't know what I am doing. Why don't we treat people with some civility around here.
My ES44AC DBHP data is derived/estimated from data in an EMD Product Application Guide since I can find no source for actual DBPull or DBHP data on the GE ES44AC. If you have it prove me wrong, I would be interested in seeing it. Until then I am sticking with a drawbar horsepower (not net traction HP) estimate based on real manufacturer's data and not opinions.
oltmannd I don't have any hard data, but I did participate on drawbar HP tests of C36-7s and SD50s on Conrail's Boston Line (many moons ago!) and my recollection is that the net traction HP variation with speed is almost nill. You do have to account for the rolling resistance of locomotive to get from net traction HP to drawbar HP (plus train acceleration), but that's only going to be a few percent of the total train resistance and is generally a wash from locomotive to locomotive.
I don't have any hard data, but I did participate on drawbar HP tests of C36-7s and SD50s on Conrail's Boston Line (many moons ago!) and my recollection is that the net traction HP variation with speed is almost nill. You do have to account for the rolling resistance of locomotive to get from net traction HP to drawbar HP (plus train acceleration), but that's only going to be a few percent of the total train resistance and is generally a wash from locomotive to locomotive.
One of the first things I noticed from the link, like you, was the drawbar HP for the ES44AC used as an example was off at higher speeds. Way off. There is no way an ES44AC loses 1000 HP at 70 mph. That's why I said it was nuts.
You are absolutely correct that net traction HP in a diesel-electric does not vary with speed, with the exception on an AC unit at extremely slow speeds where the unit will derate to maintain maximum adhesion.
For others reading this, the reason is simple. A Diesel-Electric Locomotive is an electric locomotive that carries its own power plant with it. The diesel engine, traction alternator, and electrical system could care less if the locomotive is going 10 mph down the tracks or 100 mph. It is generating electricity, the traction motors are converting the electricity into rotational force, and the whole thing is just going along for the ride.
The net traction HP is the same at 70 mph as it is at 10 mph. The only thing changing is the rolling resistance and air resistance at 70 mph, which for the ES44AC amounts to around 200 HP. So the drawbar HP of an ES44AC at 70 mph is only 200 HP less than it was at 10 mph, NOT 1000 hp.
Just because someone doesn't have formal training in a subject does not mean they cannot contribute anything. Read up on Michael Faraday.
Getting back to steam locomotive efficiency. From my observations this whole discussion can be distilled down to a few main points.
1. Will a steam locomotive ever approach the thermal efficiency of a diesel without a turbine-electric drive, condensing into a vaccum, water tube boiler, closed loop, overly complicated and delicate system? No.
2. Ideally, the rail line should be electrified (indirectly powered by steam). However, this is impractical and the infrastructure too costly for the transcontinental routes.
3. Efficiencies of 12-15% for a modern steam loco (probably requiring compounding) using all of Chapelon's, Porta's, Wardale's, et al improvements. Of course this is still 2-3 times lower thermal efficiency of a diesel. However, the economic advantages of using domestic sources of or what would be otherwise waste for fuel can overcome the thermal efficiency disadvantage.
4. As Porta points out, the construction & maintenance of steam locomotives require much less capital investment and precision, a huge plus for places with lower skilled labor forces and the less developed countries.
5. The high specific heat of water is both a benefit and a disadvantage. The high heat capacity of water allows large amounts of energy per unit mass flowing through the engine. Water is cheap and plentiful, requiring treatment where needed. Not to mention many of the other fluids for a substitue in the Rankine cycle are poisonous and/or corrosive to common metals.
Cheers - Joe
"If a nation expects to be ignorant and free, it expects what never was and never will be." Thomas Jefferson
oltmannd Wow. My very own thread! My comments were strictly objective about the nature of the TPC and RTC modeling tools - an area where I do have some expertise. If anyone took offense, I apologize. It was never my intent.
Wow. My very own thread!
My comments were strictly objective about the nature of the TPC and RTC modeling tools - an area where I do have some expertise. If anyone took offense, I apologize. It was never my intent.
oltmannd: I wasn't offended. I was just trying to explain my use of RTC in response to your reasonable question.
jwhitten Folks, let's ratchet down the personal attacks. These forums are here to have friendly conversation in a fun, non-confrontational environment. Okey-doke? John
Folks, let's ratchet down the personal attacks. These forums are here to have friendly conversation in a fun, non-confrontational environment.
Okey-doke?
John
My comments were strictly objective about the nature of the TPC and RTC modeling tools - an area where I do have some expertise. If anyone took offense, I apologize. It was never my intenet.
Don't knock people who don't have formal training. Thomas Edison was kicked out of school for being stupid and he became a newspaper delivery boy and telegraph operator before coming up with 1200 patented inventions.
But getting to the jist of this post, it might be worthwhile to consider external combustion instead of just "steam". In external combustion the combustion process is "continuous" and can thus be more carefully controlled. Also, doesn't water have a rather high specific heat? So maybe we should also consider a medium other than water in a closed circuit that includes a condenser.
oltmannd:
I used RTC because that is what I had access to. You are correct that other models are more focused on the TPC role as a primary. But over my several years of using RTC I would not say it produces poor TPC results when setup properly.
Can you provide this alternate Diesel DBHP graph with reference. I would be interested to see it.
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