Please note that I meant no antagonism, and I offer my sincere apologies if my comments came across as condescending.
Paul MilenkovicI offered that the typical consist had 1) "enough HP to make the schedule", which by definition, is a minimum amount of HP, and 2) extra axles so the train is not able to not move with a unit cutout. If you are dispatching units with this minimum amount of HP, by definition, you are below minimum HP if a unit cuts out, and you will still move, but you won't make your schedule.
Only certain products must arrive at a certain scheduled time, including priority intermodal trains, passenger trains, and perishable trains. These trains need to accelerate quick, and have more HP than they need, due to the extra redundant units.
All others can incur a bit of delay, such as having a unit fail. There is no certain hour that the train must arrive. This is cheaper than adding units, which are in very short supply. (Note Balt's comments above.)
NorthWest In agreement. I was trying to explain to Paul that trains with extra power are the exception, only the hotshot intermodal trains and specials, as well as passenger trains.
In agreement. I was trying to explain to Paul that trains with extra power are the exception, only the hotshot intermodal trains and specials, as well as passenger trains.
Many people attempt to "explain to Paul" around here.
I offered that the typical consist had 1) "enough HP to make the schedule", which by definition, is a minimum amount of HP, and 2) extra axles so the train is not able to not move with a unit cutout. If you are dispatching units with this minimum amount of HP, by definition, you are below minimum HP if a unit cuts out, and you will still move, but you won't make your schedule.
If the consist had both the minimum HP and no extra traction axles, by definition, that train would not be able to move if a unit cut out, and there would be no advantage to running 3 vs 2 vs 1 unit if that were possible.
For my troubles I get scolded with a "No!", exclamation point included.
If GM "killed the electric car", what am I doing standing next to an EV-1, a half a block from the WSOR tracks?
As surprising as it seems - the 4400 HP GE AC locomotives have been earning their keep since at least October 1994 - after 20 years it is about time for the next quantum leap in locomotive technology. Unfortunately Tier 4 compliance doesn't count as a leap in technology, just advancement of technology to remain in business.
Never too old to have a happy childhood!
NorthWest Paul MilenkovicSo what you are saying is that current freight operations practice (exceptions to be noted) is to 1) dispatch enough HP to keep the schedule and 2) dispatch enough tractive axles to not strand the train with a unit failure? No! Most trains operate with the minimum horsepower possible, because this is far cheaper, and locomotives are in short supply. 6000HP locomotives failed for a variety of reasons, lack of redundancy being only one. Inflexibility was a bigger problem. blade, the ES6000CW doesn't exist...
Paul MilenkovicSo what you are saying is that current freight operations practice (exceptions to be noted) is to 1) dispatch enough HP to keep the schedule and 2) dispatch enough tractive axles to not strand the train with a unit failure?
No! Most trains operate with the minimum horsepower possible, because this is far cheaper, and locomotives are in short supply. 6000HP locomotives failed for a variety of reasons, lack of redundancy being only one. Inflexibility was a bigger problem.
blade, the ES6000CW doesn't exist...
GE never built an ES6000CW but the ES58AC units built for Brazil are pretty much exactly what such a unit would be.
"I Often Dream of Trains"-From the Album of the Same Name by Robyn Hitchcock
With the exception of Premier trains - other trains are designed to be run at max tonnage for the ruling grade in the route of the train, unless there are designated helper districts.
It is not unusual for a train to be rated for 11600 on the ruling grade and to have a train of 11590. There is a lot of praying that takes place while the train is on the ruling grade,
Like the NS, my carrier has rules on how much power can be on the head end of a train - Unit trains are allowed the tonnage of 2 AC's + Dash8. Routine manifest trains are allowed the tonnage for 3 Dash8's. There are also rules limiting rear end helper power and rules that require cutting the 'rear end' helper into the body of the train.
Technically, diesels are all the original "Hybrid's". I worked at Lockheed when they were mimicking locomotive technology to use in buses, box trucks, and semi's. Unfortunately, there isn't likely any use for adding batteries to modify current technology since there just isn't any room for them under the current chassis. In order to get enough batteries to make full use of the technology, a loco would need to drag around a battery car, kinda like an axillary water tender to a steam loco.
Most of the "Hybrid" cars on the road these days really aren't Hybrid's in the original sense of the word. Only cars like Chevy's Volt are Hybrid's by the original definition. An engine running as only a generator with no mechanical connection to the drive components. It's like people making up new uses for the word "Ozone". The chemical makeup of Ozone is O4 and is only created by nature events like lightning. Smog is not Ozone and definitely is not O4.
For manifest trains and unit trains of bulk goods, maintaining track speed is not always necessary, and the money saved by just adhering to the tonnage profile beats the payoff amount for speed. Coal doesn't need to be moving at a continuous 50MPH, it just needs to get over the hills.
It is at least that way on my class one railroad. That is especially true for the hotter Intermodals. Lower class trains will often run according to the tonnage profile. That is why some will only run with two units on an intermodal. These are mostly double stacks with no UPS or FedEX traffic on board. The hot UPS and FedEX trains rank three units and yes that third is just for backup and to keep the train on time. I think BNSF uses four units but then they not only want to keep their hot trains on time, they want them to run track speed wherever they are at!
Here on the NS, General Freight trains and Unit trains will also run per the tonnage profile. The one thing you have to be careful though is having too many powered axles up front. On NS, we can only run three six axle 4400 HP AC units on the headend. Any more than that and we could possibly rip a draw head completely out of the end of a car on a hard uphill pull. And we can only have two shoving on the rear. You may sometimes see a train moving with more than three or four units on the headend but they are definitely not all online. At least if the engineer wants to keep from being taken out of service!
EMD#1 Reason being when you run a train with two 6,000 hp units and one goes down you will more than likely stall. Most trains are capable of being pulled by two 4,400 hp units. The third is added to help maintain schedule and to be a backup in case one of the other units goes down during the trip.
Reason being when you run a train with two 6,000 hp units and one goes down you will more than likely stall. Most trains are capable of being pulled by two 4,400 hp units. The third is added to help maintain schedule and to be a backup in case one of the other units goes down during the trip.
So what you are saying is that current freight operations practice (exceptions to be noted) is to 1) dispatch enough HP to keep the schedule and 2) dispatch enough tractive axles to not strand the train with a unit failure? And this explains the popularity of the 4400 HP unit? And why 6000 HP units have a market in places using single locomotive units (China?).
I asked some while ago on another thread why Amtrak dispatches multiple units on many trains, even if they are under 12 cars -- is this a case of "the train has to move if a unit goes out"?
I suppose the trade is that you don't dispatch any more HP than you have to because that costs fuel, but you are dispatching extra axles as "backup" -- that costs fuel too, but maybe not as much as going over-HP?
Good note on the HEP. With this, I suspect that they have removed that HEP generator, and put in a static inverter. Does anyone know?
I'm going to assume that the above proposal is basically a genset suburban locomotive. I seriously doubt that the second engine could come on line fast enough to provide additional acceleration, especially with the frequent stops involved in suburban service. It would be safer to assume that the second engine will come on line to provide the additional horsepower for heavier rush hour trains, not unlike freight gensets on a local turn.
WM7471Is it time for the locomotive manufacturers to come up with a new more powerful locomotive?
As an alternative to the somewhat horse-beating discussion of freight locomotives -- consider the recent decision by Metrolinx to use two Cummins QSK-60s (instead of a single QSK-95) in a single MP36 carbody. The peak hp of this arrangement may be as high as 5400 (depending on how the HEP arrangement is made) and this raises some interesting implications for how the higher horsepower will be used in operations.
It is at least possible that one of the engines will only come 'off idle' at higher speeds, to provide the higher horsepower needed for continued high acceleration rate at high road speeds, rather than trying to use all the available power for starting heavier trains.
JayPotterThere is an August 2012 55-page AAR research report titled "Comprehensive Evaluation of the Structural Durability of Railroad Coupler Assemblies".
AAR-TTCI R-1002, if I am not mistaken, and you can order it from this form..
efftenxrfe This is not going to be a defining answer about.... Couplers, and knuckles, (specifically the designed weakest link of freight cars) which had designed stress levels. The common knuckle could pull against 240,000 lbs of train resistance, (resistance...If your baby weighs 8 pounds, until you lift with more than 8 pounds energy, the babe won't lift from the cradle, or the crib... Those numbers are from the early 80's. So am I. The E knuckle could pull against...330,000 pounds? Metallurgy matters? Sure does.
This is not going to be a defining answer about....
Couplers, and knuckles, (specifically the designed weakest link of freight cars) which had designed stress levels.
The common knuckle could pull against 240,000 lbs of train resistance, (resistance...If your baby weighs 8 pounds, until you lift with more than 8 pounds energy, the babe won't lift from the cradle, or the crib...
Those numbers are from the early 80's. So am I.
The E knuckle could pull against...330,000 pounds?
Metallurgy matters?
Sure does.
Close enough.... Those might be close to the yield strength, but the ultimate strength is higher. Problem with operating between yield and ultimate it you get into the fatigue life of the steel. RRs typically DO operate above the yield strength of knuckles, but it's game of chance... Most of the time a knuckle fails, it's note how much of the break is "old" i.e. rusty. Too bad there's not a knuckle fatigue life indicator...
Maybe we could create one from train consist data?
-Don (Random stuff, mostly about trains - what else? http://blerfblog.blogspot.com/)
GP40-2 JayPotterThe reference to locomotive consist weights of between 800 and 1200 tonnes for "every freight train worth mentioning" seems somewhat high to me. On CSXT, the most common consist for tonnage trains, two AC-traction units, has a total weight of about 392 tonnes.
JayPotterThe reference to locomotive consist weights of between 800 and 1200 tonnes for "every freight train worth mentioning" seems somewhat high to me. On CSXT, the most common consist for tonnage trains, two AC-traction units, has a total weight of about 392 tonnes.
There was the Gandy Dancer Festival west of Madison, WI, which is mainly folk and bluegrass music down by the WSOR railroad tracks. We were running model trains in the old train station, Lions Club had a "train" of wheel barrows behind a garden tractor with steam locomotive sound effects to give rides to the children, and the WSOR was sending trains right through the middle of this. I would leave the room from supervising the model trains to (gently) scold people to stay back from the tracks to varying effect. Wish there was a way to coordinate with the WSOR that they wouldn't be conducting switching operations on a Saturday in the middle of that huge crowd of people, where for a railroad themed-event the real train constitutes an "attractive nuisance" or get the Gandy Dancer event moved away from the tracks without taking away they railroad-themed ambience.
Here is the consist that I saw the WSOR crew switching with: 2 SD40-2's and 1 GP-38 (it had the two stacks so it was the 16-cyl non-turbo version -- WSOR also has B-B's with the fat turbo stack that I figure are more rare GP-39s).
Let me see, 16 axles, over 500 tons, 8000 HP burbled by pulling one tank car. This is the kind of switching consist used on a model railroad because we keep "collecting" locomotives and need some use for them on our layout?
Since the current locomotives have the horsepower and tractive effort to exceed the strength of the strongest knuckles and couplers currently manufactured - increasing the power and tractive effort of yet to be designed locomotives will be in large part dependent upon increased strength in the coupling systems of cars and locomotives, that also have yet to be designed and manufactured.
Jay is 100% correct. If anybody doubts him, watch and learn:
watch?v=FLOguuLnhH0
Juniatha:
Wheel slip occurs when the force exceeds the coefficient of friction, and as far as I know the steel rails and steel wheels are pretty much the same composition, whether in Europe or North America. In fact NA has the advantage since the generally higher axle loadings allows higher tractive force. The higher horsepower in Europe does allow faster speeds and acceleration, of critical importance when mixing in with fast frequent passenger trains. I would guess wheel slip is rare except when starting from a stop.
Rightly or wrongly, the more usual operating philosophy in North America accepts that a freight train on the maximum grade will not maintain speed; the primary criteria being that it can reach the summit, and start again if stopped. When crawling uphill at slow speeds that higher horsepower would overpower the grip of the wheels. Microprocessors now limit the power so wheels are just starting to slip, and continue to do so for many kilometres on some famous grades.
Many North American railroads have used "slugs" for specific services, especially in yards or humps. They take advantage of the fact that there is too much horsepower (even at our lower numbers!) to be used by one diesel locomotive at slow speeds. They take the surplus and feed it to what is in reality a pure electric locomotive. The extra weight and powered axles of the slug allow the surplus horsepower to be used effectively and move heavier trains, admittedly at slower speeds.
John
WM7471 My thought would be for a locomotive that would be able to replace AC 4400s on a 2 for 3 basis, just like the 4400s did to the 3000 Hp SD40-2s. Tier 4 compliant 7000+ Hp with a single power plant.
My thought would be for a locomotive that would be able to replace AC 4400s on a 2 for 3 basis, just like the 4400s did to the 3000 Hp SD40-2s.
Tier 4 compliant
7000+ Hp with a single power plant.
(Highlighting mine.)
A significant cause of the downfall of 6000 HP locomotives was flexibility, and the 7000 HP locomotive loses much of it. Many trains that I have observed operate in a 2x1 DPU configuration. You'd need a 7000 HP locomotive and a 4400 HP locomotive to operate the same train, otherwise power would be unused. As a whole, less standardization, a primary goal of railroads. Also, if that 7000 HP locomotive fails, (and it will happen, especially with a single prime mover) you've lost two thirds of the power on the train, instead of a third.
4400 HP locomotives are the best for American railroads right now. The horsepower race is over, and the emissions race and AC traction have been the bigger deal since the failure of the 6000HP locomotives.
I'm sorry but you cannot compare European railways to the US, simply put they're chalk and cheese when it comes to similarities. Sure they use steel wheels on steel rails but the fundamentals of each system are widly different.
Those high HP electrics can't start a train the same size as an equivalent diesel loco from the US because they weigh so little (in the order of 60t difference) but where that HP comes into play is keeping up train speed. Short frequent freights is how Euope operates, not with the long heavy freights American has a network designed to deal with.
Diesels are formidable starters – but going at start-away speed all day makes traffic move slow and keeps line sections occupied longer than they should in view maximizing daily tonnage passed .
Add the weight the US diesels have to a European electric and you'll get pretty close to the same starting TE (well maybe the same as a 4-axle unit) but they'll still have a higher balance speed. Electric has it's merits but comparing Europe with the US? Wrong way of going about it.
ML
You may say "Oh , there she goes again!" - yet , here I go again with my voting for electrification :
CSSHEGEWISCH
quote : The three groups listed cover almost every conceivable service requirement and the various manufacturers have them covered quite nicely. There doesn't seem to be any need for a super-size locomotive at this time.
I don’t think so , they only cover service requirements in multitudes , no single unit covers but the easiest of demands . That means for every freight train worth mentioning you have to assemble diesel units easily amounting to 800 .. 1000 .. 1200 tonnes combined – a sizeable fraction of total train load and a way to compose power needed nowhere but in the US deemed acceptably economic . So , technically , although it’s correct no doubt the RRs didn’t appreciate it , there *would be* scope for larger power units .
BaltACD
quote : The limiting factor in locomotives is wheel slip control - all the horsepower in the world does no good if you are just spinning your wheels.
If that was so how do you explain synchronous electrics like the European standard Taurus class developing 6400 kW on but four axles *and* but 2/3 of axle load as used by US diesels ?
D. Carleton
quote : Three Dash 8-40Cs were more efficient than four SD40-2s and Two AC4400s are more efficient than three Dash 8s and so on.
Exactly that’s the point ! And one unit is more economic than two units . Why did European railways go a long way to eliminate double traction – not to speak of ponderous mass multiple unit traction ? True , conditions of train masses differ substantially from those in the US , still electric traction should not be banned from thought , even if economies can be a trap for technical development . In my view dieselization the way it happened on American RRs was a fatal short term modernization in the long term having turned into a dead-end road with relatively low power ceilings as mentioned by users in this thread and – let me add – very high motive power unproductive mass .
Cx 500
quote : I suspect that modern technology has reached the limit of what can be achieved with the current rail-wheel interface.
See electric traction , for example before mentioned Taurus family synchronous electrics
http://www.jmpet.de/taurus.htm
having arrived at over 100 hp [metric] per t [metric] of unit mass and compare with typical contemporary diesel 15 – 20 hp / t . Diesels are formidable starters – but going at start-away speed all day makes traffic move slow and keeps line sections occupied longer than they should in view maximizing daily tonnage passed .
Regards
Juniatha
My poor switchpoints and curve rails....especially in the terminals that have to handle the darned things....
I think you will find that the sweet spot for horsepower has increased in lockstep with improvements in wheel slip control. The modern AC locomotives have a factor of adhesion that is considerably higher than first generation units such as the GP9, so the extra power does translate into extra tractive effort. Wheel slip on heavy grades with the higher horsepower units arriving in the 60s (2400-3000hp) was found to be a problem by several railroads. Lots of R&D over the following years went into improving the issue.
I suspect that modern technology has reached the limit of what can be achieved with the current rail-wheel interface. This can be solved in model railway field by such expedients as traction tires; that's not an option for the real thing!
Greater horsepower will still be desirable when speed is the primary objective, primarily in passenger applications, and the railroad is willing to pay the extra fuel costs for that higher speed.
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