If you're driving your car of flying an airplane, you wouldn't keep the thing at max throttle for extended periods of time since it's really hard on the engine. Taken to railroading, do you try to stay out of run 8 for extended periods of time or is it ok to crank it there and leave it there?
Notch 8 unless you get the train above maximum authorized speed for the track.
Diesel locomotives are designed to be operated in the 8th notch for hours and hours.
While I have no idea of the specifics, each throttle position operates the Prime Mover within a relatively narrow RPM range. I suspect, with different fuel mapping, the prime movers could put out more HP at higher RPM's. The manufacturers settings on the fuel mapping are a function of both prime mover reliability and fuel economy; as a result the prime mover is not mechanically stressed to it's maximum limits even when operated at Notch 8 for continuous periods.
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A locomotive is different than a car or airplane. The power rating of the diesel engine is rated for extended operation at full rated power. EMD's V20 was successfully run at 4200 hp in the SD45X, while all other SD45 were only 3600hp. Similarly the V20-710G used in the SD80MAC was test run at 5500hp. successfully, the only issue is the wear rate of the components. Railroading is a numbers based business. Is the extra work that can be done with the locomotive running at a higher horsepower rating enough to offset the higher fuel consumption and faster component wear? If yes, uprated the diesel engine, if not, then don't uprate it. Note this assumes that the alternator and traction motors can handle the greater power. Three Santa Fe SD75Ms were experimentally rated at 4500hp, as Santa Fe intended to use them on transcontinental Intermodal trains where horsepower is beneficial. What happened was that fuel used per horsepower produced dropped, and components wore out at a faster rate. Now that was not unexpected, but the savings from needing slightly fewer locomotives in the pool did not offset the rise in fuel consumption and shorter overhaul interval. And remember a locomotive in the shop for an overhaul isn't making money pulling a train.
Yeah it definitely makes sense that diesels would be throttled so that notch 8 is basically a max continuous power but not max max power, because max max really isn't economical for the RR and, unlike say in an aircraft, there is no reason to really need "more power" on the RR because at worst you'll just stall the train, which in the grand scheme of things is not that big of a deal. Compare that to a jet airplane in a windshear situation, if you don't get those engines to crank out juice you're gonna hit the ground, not good. That's why when I flew jets the only time we were ever to go full throttle was in windshear as we'd overtemp the engines and essentially break them, but for those critical seconds you'd get the power you need.
It depends on what you are pulling. All engines have ammeters. I could run an engine in Run 8 all day by itself, and she would purr right along. Now if I am climbing a mountain pass with a heavy train and I throw her into run 8 for even 30 minutes, I could destroy the engine. There are warning labels, which say things like "Do not exceed X amount of amps for more 15 minutes" or something similiar. So you have to watch your gauges also.
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coborn35 It depends on what you are pulling. All engines have ammeters. I could run an engine in Run 8 all day by itself, and she would purr right along. Now if I am climbing a mountain pass with a heavy train and I throw her into run 8 for even 30 minutes, I could destroy the engine. There are warning labels, which say things like "Do not exceed X amount of amps for more 15 minutes" or something similiar. So you have to watch your gauges also.
Can you provide some more detail about why going up a mountain in run 8 is different than going across level ground in run 8?
The difference is not so much in the engine as the electrical system. Traction motors will overheat very quickly when they are receiving full power but are turning at the lower speeds involved in going uphill.
As long as you stay within the maximum continuous amperage rating for the locomotive you can run it up hill 24 hours a day until the fuel tank runs dry, refill the tank and run it until that tank runs dry. The parts that can get damaged from 'over exerting' the locomotive are the electrical parts...run too many amps through the traction motors for too long and the heat generated will destroy the traction motor.
All DC locomotives have what is termed a 'Short Time Rating'. There is a maximum continuous amperage rating....for the sake of argument I'll set that value at 1000 amps. The electrical system can cool itself and prevent damage to the electrical components as long as the 1000 amp value is not exceeded....the locomotive can run continuously at 1000 amps or less. If the movement gets to a situation where the electrical draw is 1100 amps, the short time rating plate will state that at 1100 amps the locomotive can operate 1 hour. At 1200 amps it can operate 15 minutes at 1300 amps it can operate 5 minutes, (note-the values and times I have shown are for demonstration purposes ONLY) Each make and model of locomotive has it's own short time rating.
The prime mover can operate at Notch 8 max power forever, as long as the electrical draw on the system stays within the Continuous Rating value.
Locomotives have a data element listed on their specifications 'Minimum Continuous Speed'. That is the speed at which, with the prime mover in the 8th notch and producing maximum power, the electrical draw from the generator/alternator will equal the maximum continuous amperage allowed. This speed, depending upon the make, model and gearing of a locomotive can vary from 7 to 12 MPH for freight units and may be as high as 25 MPH for passenger geared units.
BaltACD As long as you stay within the maximum continuous amperage rating for the locomotive you can run it up hill 24 hours a day until the fuel tank runs dry, refill the tank and run it until that tank runs dry. The parts that can get damaged from 'over exerting' the locomotive are the electrical parts...run too many amps through the traction motors for too long and the heat generated will destroy the traction motor. All DC locomotives have what is termed a 'Short Time Rating'. There is a maximum continuous amperage rating....for the sake of argument I'll set that value at 1000 amps. The electrical system can cool itself and prevent damage to the electrical components as long as the 1000 amp value is not exceeded....the locomotive can run continuously at 1000 amps or less. If the movement gets to a situation where the electrical draw is 1100 amps, the short time rating plate will state that at 1100 amps the locomotive can operate 1 hour. At 1200 amps it can operate 15 minutes at 1300 amps it can operate 5 minutes, (note-the values and times I have shown are for demonstration purposes ONLY) Each make and model of locomotive has it's own short time rating. The prime mover can operate at Notch 8 max power forever, as long as the electrical draw on the system stays within the Continuous Rating value. Locomotives have a data element listed on their specifications 'Minimum Continuous Speed'. That is the speed at which, with the prime mover in the 8th notch and producing maximum power, the electrical draw from the generator/alternator will equal the maximum continuous amperage allowed. This speed, depending upon the make, model and gearing of a locomotive can vary from 7 to 12 MPH for freight units and may be as high as 25 MPH for passenger geared units. coborn35: It depends on what you are pulling. All engines have ammeters. I could run an engine in Run 8 all day by itself, and she would purr right along. Now if I am climbing a mountain pass with a heavy train and I throw her into run 8 for even 30 minutes, I could destroy the engine. There are warning labels, which say things like "Do not exceed X amount of amps for more 15 minutes" or something similiar. So you have to watch your gauges also.
coborn35: It depends on what you are pulling. All engines have ammeters. I could run an engine in Run 8 all day by itself, and she would purr right along. Now if I am climbing a mountain pass with a heavy train and I throw her into run 8 for even 30 minutes, I could destroy the engine. There are warning labels, which say things like "Do not exceed X amount of amps for more 15 minutes" or something similiar. So you have to watch your gauges also.
Thats what I was trying to say, you just articulated it better lol.
coborn35 BaltACD: As long as you stay within the maximum continuous amperage rating for the locomotive you can run it up hill 24 hours a day until the fuel tank runs dry, refill the tank and run it until that tank runs dry. The parts that can get damaged from 'over exerting' the locomotive are the electrical parts...run too many amps through the traction motors for too long and the heat generated will destroy the traction motor. All DC locomotives have what is termed a 'Short Time Rating'. There is a maximum continuous amperage rating....for the sake of argument I'll set that value at 1000 amps. The electrical system can cool itself and prevent damage to the electrical components as long as the 1000 amp value is not exceeded....the locomotive can run continuously at 1000 amps or less. If the movement gets to a situation where the electrical draw is 1100 amps, the short time rating plate will state that at 1100 amps the locomotive can operate 1 hour. At 1200 amps it can operate 15 minutes at 1300 amps it can operate 5 minutes, (note-the values and times I have shown are for demonstration purposes ONLY) Each make and model of locomotive has it's own short time rating. The prime mover can operate at Notch 8 max power forever, as long as the electrical draw on the system stays within the Continuous Rating value. Locomotives have a data element listed on their specifications 'Minimum Continuous Speed'. That is the speed at which, with the prime mover in the 8th notch and producing maximum power, the electrical draw from the generator/alternator will equal the maximum continuous amperage allowed. This speed, depending upon the make, model and gearing of a locomotive can vary from 7 to 12 MPH for freight units and may be as high as 25 MPH for passenger geared units. coborn35: It depends on what you are pulling. All engines have ammeters. I could run an engine in Run 8 all day by itself, and she would purr right along. Now if I am climbing a mountain pass with a heavy train and I throw her into run 8 for even 30 minutes, I could destroy the engine. There are warning labels, which say things like "Do not exceed X amount of amps for more 15 minutes" or something similiar. So you have to watch your gauges also. Thats what I was trying to say, you just articulated it better lol.
BaltACD: As long as you stay within the maximum continuous amperage rating for the locomotive you can run it up hill 24 hours a day until the fuel tank runs dry, refill the tank and run it until that tank runs dry. The parts that can get damaged from 'over exerting' the locomotive are the electrical parts...run too many amps through the traction motors for too long and the heat generated will destroy the traction motor. All DC locomotives have what is termed a 'Short Time Rating'. There is a maximum continuous amperage rating....for the sake of argument I'll set that value at 1000 amps. The electrical system can cool itself and prevent damage to the electrical components as long as the 1000 amp value is not exceeded....the locomotive can run continuously at 1000 amps or less. If the movement gets to a situation where the electrical draw is 1100 amps, the short time rating plate will state that at 1100 amps the locomotive can operate 1 hour. At 1200 amps it can operate 15 minutes at 1300 amps it can operate 5 minutes, (note-the values and times I have shown are for demonstration purposes ONLY) Each make and model of locomotive has it's own short time rating. The prime mover can operate at Notch 8 max power forever, as long as the electrical draw on the system stays within the Continuous Rating value. Locomotives have a data element listed on their specifications 'Minimum Continuous Speed'. That is the speed at which, with the prime mover in the 8th notch and producing maximum power, the electrical draw from the generator/alternator will equal the maximum continuous amperage allowed. This speed, depending upon the make, model and gearing of a locomotive can vary from 7 to 12 MPH for freight units and may be as high as 25 MPH for passenger geared units. coborn35: It depends on what you are pulling. All engines have ammeters. I could run an engine in Run 8 all day by itself, and she would purr right along. Now if I am climbing a mountain pass with a heavy train and I throw her into run 8 for even 30 minutes, I could destroy the engine. There are warning labels, which say things like "Do not exceed X amount of amps for more 15 minutes" or something similiar. So you have to watch your gauges also.
Now that's the case for DC locomotives, AC ones you can run in notch 8 at 5 mph all day, correct?
Sawtooth500 If you're driving your car of flying an airplane, you wouldn't keep the thing at max throttle for extended periods of time since it's really hard on the engine. Taken to railroading, do you try to stay out of run 8 for extended periods of time or is it ok to crank it there and leave it there?
Notch 8 all day long. The diesel engine and it's support systems (cooling, lubrication, etc) are designed, build and rated to do just that. You could design a locomotive diesel engine to have a "short time" higher maximum power output, but it would do little for train operation, carry a penalty for the engine life and be hard to manage.
-Don (Random stuff, mostly about trains - what else? http://blerfblog.blogspot.com/)
The thing to remember is that the diesel engine at a given rpm is putting out a (relatively) fixed amount of horsepower. The locomotive tries to apply that fixed horsepower over a wide speed range. If you do the mathematics, tractive effort in pounds times speed in mph, divided by 375, is rail horsepower. Low speed, high TE, and vice versa. The electrical system provides that power coupling. Volts times amps divided by 746 is electrical horsepower. Let's ignore efficiency for simplicity, ok? Low speed, high amps to get the high TE, high speed, high volts to get the rpm. How low you can go and how high you can go are determined by the electrical corner point characteristics of the generator. These are plotted graphically in a volt-amp curve; the "upper corner point" is where it maxes out in volts, and that determines the top speed to which horsepower can be carried. Obviously, you want that to be higher than the geared top speed. (There are notorious cases of locos that couldn't, the Alco RSD-4 being probably the best known; the DL-640/C-424 avoided it -barely - by doing a lot of traction motor field shunting. Some switchers couldn't because they almost never were run that fast. But, I digress).
At the other end of the volt-amp characteristic, if you put the throttle in notch 8 at standstill, assuming the wheels didn't slip, the generator would go into current limit. The DC motors would not be happy unless the train accelerated quickly (even then you'd be at risk of raising commutator bars); AC motors can handle it ok. Generator current limit was generally above the generator's continuous current limit, and quite a bit above the TM continuous rating. That's what allowed the short time operation others have described quite nicely. The "minimum continuous speed" quoted above was, by design, almost always the lowest speed at which the traction motors were operated at or below their continuous current rating.
I probably rambled on longer than you wanted to read, but I hope this helps.
Dave
Thanks for your clarifications on this matter.
It seams like to me that we have so many newbies that have not actually read Trains Magazine in the last several years.
The Diesel-electric locomotive is not only about Rudy.....
You are directing electric power to electric motors....governed by a dashboard-display.
Horsepower has been well expressed vs. TE....
Tractive Effort required for the train in tonnage-ratings determines the ability for the prime-mover to work for.
Don't count on DC power that is rated for 9.8-miles-per-hour to load a traction motor for more than 15-minutes.
AC power will hold 20,020-metric tons at dead still on Crawford Hill for four-hours @ 1.8%-grade with no problems & start like they just coupled-up.
If your running a desktop display that has a acceleration gauge, you would know how fast or slow you will change in the next mile per minute.
Overspeeding prime-movers are a very co$tly waste & don't help a road at all.
With a DC Traction Motors as long as you do not exceed the amperage short time ratings or the maximum authorized speed you can keep them in notch 8 all day long. If you start pulling excessive amperage and get into the short time ratings you will have to reduce the throttle to keep from burning up the traction motors. If that means you end up stalling, then you'll either have to double the hill or if possible use assistance from another train's power to make it over the grade. Timetables list the maximum amount of tonnage each type of engine can handle over a certain line segment. Trains are built with this in mind so as not to exceed the limit of the train's available power. Out on the road the crew will have to determine if an en-route pickup will exceed the tonnage ratings of the locomotives.
On the NS, road trains are generally assigned with 4000 HP six-axle locomotives. Depending on the train and its size, that means either 2 or 3 head-end units. Before departing from a terminal one of the first questions I ask a conductor is how long the train is in feet and how heavy the train is in tons. Yesterday I ran train 213, a hot intermodal train assigned with an ES40DC and two 9-40CW locomotives equalling 12,000 total available HP. The train was appx. 4,200 feet and around 4,000 tons. This meant that I had a 3 HP/Ton ratio which equated to a very good trip allowing me to climb a 17 mile 1.5 % grade in run 8 at 50 MPH. Much of the rest of the trip I was able to run the train the maximum authorized speed of 60 MPH. Had the train been an 8,000 ton train equipped with only 2 units the trip would have been a much different story and that same grade would have been in run (notch) 8 at 11 MPH and would have seemed like an eternity to conquer!
When you have to add a pusher like that does the power cut off the train or just hookup?
I'm having trouble believing this.An induction motor is, in effect a dead short, except for the effect of the counter emf produced by it's rotation. You can easily see this effect on the start up of a motor where there is a surge of current( called "in rush"), and as the motor gains speed the amperage reduces to that required to maintain rotation. Without rotation the motor is a dead short and would melt down in a hurry. So is it an induction motor? Is it squirrel cage or wound rotor?
tdmidget AC power will hold 20,020-metric tons at dead still on Crawford Hill for four-hours @ 1.8%-grade with no problems & start like they just coupled-up. I'm having trouble believing this.An induction motor is, in effect a dead short, except for the effect of the counter emf produced by it's rotation. You can easily see this effect on the start up of a motor where there is a surge of current( called "in rush"), and as the motor gains speed the amperage reduces to that required to maintain rotation. Without rotation the motor is a dead short and would melt down in a hurry. So is it an induction motor? Is it squirrel cage or wound rotor?
In fact, an induction motor is not a dead short. The windings are an inductor (coil) and - when used with alternating current - have inductive reactance that counters the flow of current. Inductive reactance is proportional to the frequency applied to the motor, XL=2piFL. This is what allows the locomotive to apply full power to a stalled motor - the motor, with an AC voltage applied, will not allow too much current to flow since the inductive reactance is resisting it. The inductive reactance can be considerably more than the simple resistance of the windings.
In contrast, although a DC locomotive also has inductive reactance in the windings of the traction motor, it is a moot point since the "Frequency" of the voltage applied to it is 0 - it's direct current. That means that the only limitation to the current on a stalled DC traction motor is just the resistance of the winding, which is very low. Since the resistance is low, it allows a lot of current to flow - more than enough to thermally destroy the motor given enough time. The counter-emf generated by the rotating motor increases enough at some point that the current drops below the maximum value that the motor can take continously. Above this would be the minimum speed at which the locomotive can operate at max power continously.
Hope that helps -
James
Sounds good but just get yourself a squirrel cage motor, immobilize the rotor, put the power to it and watch the magic smoke escape. Why would it be different in a locomotive?
I can see however that a traction motor would be cooled by a separate blower while a garden variety motor has it's fan on the rotor shaft. But it is hard to believe that it would make that much difference.
I agree that if you take an off the shelf AC motor it will burn up under locked rotor conditions. They are not designed or intended for that type of application. However, an AC traction motor can be (and is) designed to live under locked rotor conditions just like a locomotive. For that matter, a DC motor can also be designed to live under continuous locked rotor conditions, but it would be so large and heavy it would be impractical to use on a locomotive. The inductance of the windings combined with cooling allows the AC traction motor to be designed so that it can take full load, locked rotor abuse and live to tell about it, yet be small enough to fit under the locomotive. The DC motor doesn't have the advantage of inductive reactance to help limit locked rotor amperage, so it would have to have massive windings to provide sufficient resistance to stall current and dissipate heat under those conditions - way too massive to fit under a diesel locomotive.
It's a matter of using the characteristics of the motor to help design it properly for the intended service. The inductance of an AC motor allows it to be designed to do something that would be impractical for a DC motor. The proof is in the pudding, as they say...
- James
It is a rare thing these days to have help from another train because most of the time the dispatcher will just have you either double the hill or cut off part of the train and set it out on a side track to be picked up later by another train. Most of the time when this sort of thing happens it is due to a locomotive failure in the consist and not due to over-loading the train at the initial terminal. However, if another train is called to assist, then they will cut away from their own train to come rescue yours. This could be either lending one of their engines to be added to the head-end or pushing it from the rear.
On NS, to keep from braking knuckles we are limited to 24 powered axles on the head-end unless it is a unit train equipped with high-strength knuckles, then you can have up to 32. High adhesion 6 axle locomotives such as 9-40CWs or SD70s are actually considered as 8 axle units. High adhesion AC traction locomotives such as an ES44AC or SD70Ace are considered as 9 axle units. This is compared to the traditional SD40-2 that is rated as a true 6 axle engine.
Also a motor off the shelf is operated at a fixed frequency and voltage. The computer can vary things like frequency and voltage as needed in an AC traction motor.
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