Why does Amtrak run with 2 locomotives?

|
Want to post a reply to this topic?
Login or register for an acount to join our online community today!

Why does Amtrak run with 2 locomotives?

  • I live in Chicago, and see many Amtrak long distance trains (California Zephyr, Southwest Chief, Empire Builder) running with 2 Genesis locos and ussually about 6-10 cars.

    Now let me get this straight - A Genesis has 4,000 HP, correct? Ok, so assuming that a freight train locomotive has 4000-4400 HP, the car/loco ratio for freight trains is a LOT higher than for Amtrak, not to mention I'm assuming freight cars are heavier...

    I know Amtrak trains go faster, but seriously, not that much faster than freights.

    So why the 2 locos?
    Replies to this thread are ordered from "oldest to newest".   To reverse this order, click here.
    To learn about more about sorting options, visit our FAQ page.
  • Not sure about this but it since it has to do with the weight, ruling grade and desired speed, I thought this comparison might help.

    Cal Zephyr:  2-3 Genesis locs (8000-12,000 hp?)  10 cars @ 74 tons per Superliner = 740 tons. + engine weight (122 tons X 2-3 = 244 - 366 t) = 988 - 1106 tons. 4 sleepers X 35 passengers = 70; 5 coaches at 90 per car = 450; total = 520, top speed 110 mph?

    ICE 3 on DB:  16 traction motors under the 8 car train, 12,000 hp,  409 tons carrying a maximum of 390 passengers at speeds up to 187 mph.

     

  • Locomotive failure, schedule demands, and its Amtrak...

  • Sawtooth500
    I live in Chicago, and see many Amtrak long distance trains (California Zephyr, Southwest Chief, Empire Builder) running with 2 Genesis locos and ussually about 6-10 cars.

    Now let me get this straight - A Genesis has 4,000 HP, correct? Ok, so assuming that a freight train locomotive has 4000-4400 HP, the car/loco ratio for freight trains is a LOT higher than for Amtrak, not to mention I'm assuming freight cars are heavier...

    I know Amtrak trains go faster, but seriously, not that much faster than freights.

    So why the 2 locos?

    The Empire Builder is pulled by two locomotives from Chicago to Spokane, where the train is split into Portland and Seattle sections.  One locomotive is used to power the Portland section, whilst the other powers the Seattle section. 

    The Texas Eagle, which never has more than seven cars and usually runs with six, does nicely with one locomotive.  I believe the same number of cars make up the City of New Orleans, which also gets just one locomotive.

    Whether the trains gets one or two locomotives is probably a function of the number and weight of the cars, the grades that must be mastered, the speeds that must be maintained, as well as other operating conditions.  Hopefully one of our engineers can enlighten us on why some of the long distance trains get two locomotives whilst others get just one.

  • Don't forget that as much as 700hp. is diverted to providing hotel power to the train. Then you have situations like on the climb out of the Colorado River basin to the top at Yampai Summit, over 100 miles of near steady 1.4%  which all but the hottest freights climb at 25 - 30 mph. and Amtrak climbs at 70 mph. And then consider on a route like that if you lose a Diesel you have no AC in the summer and no heat in the winter if you have only one locomotive.
  • Still, most of that stuff doesn't make sense to me....

    Cal Zephyr: 2-3 Genesis locs (8000-12,000 hp?) 10 cars @ 74 tons per Superliner = 740 tons. + engine weight (122 tons X 2-3 = 244 - 366 t) = 988 - 1106 tons. 4 sleepers X 35 passengers = 70; 5 coaches at 90 per car = 450; total = 520, top speed 110 mph?


    First off, to the best of my knowledge except on the Northeast Corridor, the max operating speed for most Amtrak as limited by tracks is 80 mph (or 79, if you insist). I do believe that certain trains, such as the Southwest Chief, do hit 90 at times because some of the track they run on is Class 5 track. I was talking with an Amtrak engineer once and I asked him the locomotive question, he didn't know the definite answer, but he did say that sometimes the Southwest Chief will operate on one engine, it just take a while to get to 90 on one engine, but you'll still get there. I don't believe the California Zephyr goes any faster than 80.

    Locomotive failure, schedule demands, and its Amtrak...


    Regarding locomotive failure, wouldn't it be cheaper just to have better maintenance than it would be two run another locomotive? Not to mention all the money you'd save for new routes if they didn't have to buy new locomotives... And regarding schedule demands, well if only 1 loco was scheduled and they had another free one, wouldn't this make the schedule more flexible? Scheduling 2 locos puts more strain on the schedule, not less....

    The Empire Builder is pulled by two locomotives from Chicago to Spokane, where the train is split into Portland and Seattle sections. One locomotive is used to power the Portland section, whilst the other powers the Seattle section.


    Now that kind of makes sense, if they are going to be spilling the train, but wouldn't it be cheaper just to store a locomotive in Spokane instead of running it every time to Chicago and back?

    Don't forget that as much as 700hp. is diverted to providing hotel power to the train. Then you have situations like on the climb out of the Colorado River basin to the top at Yampai Summit, over 100 miles of near steady 1.4% which all but the hottest freights climb at 25 - 30 mph. and Amtrak climbs at 70 mph. And then consider on a route like that if you lose a Diesel you have no AC in the summer and no heat in the winter if you have only one locomotive.


    Don't all passenger locomotives have head end units which provide the electric power for the train? And those units are separate from the prime mover, correct? I know that if you look through the back door of a genesis loco you see a second, smaller diesel in the back room. Also, regarding speeds through the mountains, if a helper loco is truly needed to maintain speed on a grade, wouldn't a helper district make much more sense than running the locomotive the whole distance to and from Chicago?

    FYI I'm not trying to offend anyone for the posts and thank you very much for giving feedback, I'm just playing devil's advocate here, and I'm trying to find the correct answer!
  •  From what I have heard and read, the Head End Power(HEP) for Hotel power, is only adequate for a maximum of eight cars. A locomotive will be capable of handeling more than eight cars, but the HEP isn't. If there are (or possibly will?) more than eight cars, there will be 2 locomotives.

    Doug

    May your flanges always stay BETWEEN the rails

  • challenger3980

     From what I have heard and read, the Head End Power(HEP) for Hotel power, is only adequate for a maximum of eight cars. A locomotive will be capable of handeling more than eight cars, but the HEP isn't. If there are (or possibly will?) more than eight cars, there will be 2 locomotives.

    Doug

    That makes sense if you need two HEP units for 9 and more cars... but now the business man in me asks... wouldn't it not make more sense for Amtrak to simply upgrade the HEP unit to output more power? I'm sure that upgrading the HEP in the long run would cost a lot less than operating a second diesel on 2 thousand mile trips just for a second HEP...
  • challenger3980

     From what I have heard and read, the Head End Power(HEP) for Hotel power, is only adequate for a maximum of eight cars. A locomotive will be capable of handeling more than eight cars, but the HEP isn't. If there are (or possibly will?) more than eight cars, there will be 2 locomotives.

    Doug

     

    I don't know whether or not that is true, but it fits with a recent experience.  We rode the Blue Ridge Special from Spencer, NC to Asheville, NC about 3 weeks ago.  It had 3 Amtrak engines pulling 25 cars.

    Of course, it also had to pull those cars up a pretty steep grade through the Pisgah National Forrest.

    Dave

    Lackawanna Route of the Phoebe Snow

  • Keep in mind that speed restriction abound in the Northest Corridor.  90 mph over Metro North Railroad tracks, grade crossings between New London CT and Westerly RI, and all the 100 year old Draw Bridges. 

    In the Northeast Corridor, operating under electric power from Boston to Washington, the Acela is powered with two 6,000 hp power cars, one on each end, total 12,000 hp, runs at speeds up to 150 mph.

    Regional service in The Corridor, also electric powered, is hauled at speeds up to 125 mph by AEM-7 (7,000 hp) or HHP-8 (8,000 hp). They can be double headed depending on train length.

    Shorter trains running off The Corridor, such as the Springfield Shuttle or the Vermonter, are powered by one Genisis locomotive (Amtrak calls them AMD-103 as they are geared for 103 mph). The P40 is 4,000 hp and the P-42 is 4,200 hp.  You are talking nearly new GE locomotives.  After the early "bugs" were worked out, depenable operation is the norm.

    Don U. TCA 73-5735

  • Here's how it works. Start with the schedule, complete with stops. Figure out how much HP you need to get the train over the road on that schedule plus some padding for service reliability. You can do this by trial and error with actual operation or by simulation. For most Amtrak trains, you'll wind up in the 6-8 HP/ton range. Now, take a typical Amtrak train of 10 cars or so at 70 tons each plus a locomotive or two at 135 tons each. That's about 1000 tons. One P42 = 4.2 HP/ton (closer to 3.5 HP/ton with HEP accounted for). Not enough. Two P42s = 8.4 HP/ton (7.5 HP/ton with HEP). Bingo! Two P42s are needed. Could you run the train with one P42? Most likely, yes, you'd get there, but, you'd be late at destination more often (maybe even all the time). There is one added wrinkle. The TE at minimum continuous speed for a P42 is about 36,000#. The max ruling grade for one P42 with a 1000 ton train would be 1.8%. That would be OK from trains in the east that don't go over the Alleghenies. like the Florida trains, the Crescent and the City of New Orleans, but not for most of the western trains, so two are needed to keep from stalling. In fact, two P42s on the SW Chief would be cutting it kind of close for Raton, so three are a safe bet.

    -Don (Random stuff, mostly about trains - what else? http://blerfblog.blogspot.com/

  • Sawtooth500
    I know Amtrak trains go faster, but seriously, not that much faster than freights.
    Maybe more than you think. A typical Amtrak train needs to be able to run long stretches at track speed. A typical manifest freight train operating at 1.0 HP/ton or so will only hit track speed on long level or downhill portions of the route. Average freight train speed (all kinds, including unit trains and intermodal) is only in the mid 20s. Average Amtrak train speed is about 50 mph.

    -Don (Random stuff, mostly about trains - what else? http://blerfblog.blogspot.com/

  • Sawtooth500
    Still, most of that stuff doesn't make sense to me....

    Cal Zephyr: 2-3 Genesis locs (8000-12,000 hp?) 10 cars @ 74 tons per Superliner = 740 tons. + engine weight (122 tons X 2-3 = 244 - 366 t) = 988 - 1106 tons. 4 sleepers X 35 passengers = 70; 5 coaches at 90 per car = 450; total = 520, top speed 110 mph?


    First off, to the best of my knowledge except on the Northeast Corridor, the max operating speed for most Amtrak as limited by tracks is 80 mph (or 79, if you insist). I do believe that certain trains, such as the Southwest Chief, do hit 90 at times because some of the track they run on is Class 5 track. I was talking with an Amtrak engineer once and I asked him the locomotive question, he didn't know the definite answer, but he did say that sometimes the Southwest Chief will operate on one engine, it just take a while to get to 90 on one engine, but you'll still get there. I don't believe the California Zephyr goes any faster than 80.

    Locomotive failure, schedule demands, and its Amtrak...


    Regarding locomotive failure, wouldn't it be cheaper just to have better maintenance than it would be two run another locomotive? Not to mention all the money you'd save for new routes if they didn't have to buy new locomotives... And regarding schedule demands, well if only 1 loco was scheduled and they had another free one, wouldn't this make the schedule more flexible? Scheduling 2 locos puts more strain on the schedule, not less....

    The Empire Builder is pulled by two locomotives from Chicago to Spokane, where the train is split into Portland and Seattle sections. One locomotive is used to power the Portland section, whilst the other powers the Seattle section.


    Now that kind of makes sense, if they are going to be spilling the train, but wouldn't it be cheaper just to store a locomotive in Spokane instead of running it every time to Chicago and back?

    Don't forget that as much as 700hp. is diverted to providing hotel power to the train. Then you have situations like on the climb out of the Colorado River basin to the top at Yampai Summit, over 100 miles of near steady 1.4% which all but the hottest freights climb at 25 - 30 mph. and Amtrak climbs at 70 mph. And then consider on a route like that if you lose a Diesel you have no AC in the summer and no heat in the winter if you have only one locomotive.


    Don't all passenger locomotives have head end units which provide the electric power for the train? And those units are separate from the prime mover, correct? I know that if you look through the back door of a genesis loco you see a second, smaller diesel in the back room. Also, regarding speeds through the mountains, if a helper loco is truly needed to maintain speed on a grade, wouldn't a helper district make much more sense than running the locomotive the whole distance to and from Chicago?

    FYI I'm not trying to offend anyone for the posts and thank you very much for giving feedback, I'm just playing devil's advocate here, and I'm trying to find the correct answer!

     

     There are two primary methods for providing hotel power to a passenger train. the first is to draw it off of the locomotive's main alternator(which O.C does mean less power is available for the traction motors) and IINM this is the method most if not all of Amtrak's diesel fleet uses. The second method is to have an auxiliary diesel electric genset on the locomotive (or in some cases in a head end generator car). This is very common on commuter railroads. My understanding is that an HEP genset can save significant amounts of fuel in services where the train starts and stops frequently i.e commuter service..

    "I Often Dream of Trains"-From the Album of the Same Name by Robyn Hitchcock

  • Sawtooth500

    That makes sense if you need two HEP units for 9 and more cars... but now the business man in me asks... wouldn't it not make more sense for Amtrak to simply upgrade the HEP unit to output more power? I'm sure that upgrading the HEP in the long run would cost a lot less than operating a second diesel on 2 thousand mile trips just for a second HEP...

     

    No additional locomotives for HEP, only one locomotive can supply the HEP otherwise they would have to be synchronized (which is difficult on a locomotive with its variable power demands). But if the locomotive supplying HEP dies you have to have another that can be cut in.


  • Sawtooth500
    Still, most of that stuff doesn't make sense to me....

    Cal Zephyr: 2-3 Genesis locs (8000-12,000 hp?) 10 cars @ 74 tons per Superliner = 740 tons. + engine weight (122 tons X 2-3 = 244 - 366 t) = 988 - 1106 tons. 4 sleepers X 35 passengers = 70; 5 coaches at 90 per car = 450; total = 520, top speed 110 mph?


    First off, to the best of my knowledge except on the Northeast Corridor, the max operating speed for most Amtrak as limited by tracks is 80 mph (or 79, if you insist). I do believe that certain trains, such as the Southwest Chief, do hit 90 at times because some of the track they run on is Class 5 track. I was talking with an Amtrak engineer once and I asked him the locomotive question, he didn't know the definite answer, but he did say that sometimes the Southwest Chief will operate on one engine, it just take a while to get to 90 on one engine, but you'll still get there. I don't believe the California Zephyr goes any faster than 80.

    Amtrak has fuel saving instructions in place and locomotive assignments are a function of a combination of things:  fuel consumption, power requirements, HEP eliability, grades and train weight.  One item not mentioned is the fact that the P42's are much lighter than freight locomotives of the same horsepower rating and are therefore, a little more slippery with a poorer factor of adhesion.  The fact that the locomotives are geared for passenger speed reduces the power output at the rail in terms of acceleration, i.e, these engines are built for speed, not lugging ability and as such are much more sensitive to train weight.

    Locomotive failure, schedule demands, and its Amtrak...


    Regarding locomotive failure, wouldn't it be cheaper just to have better maintenance than it would be two run another locomotive? Not to mention all the money you'd save for new routes if they didn't have to buy new locomotives... And regarding schedule demands, well if only 1 loco was scheduled and they had another free one, wouldn't this make the schedule more flexible? Scheduling 2 locos puts more strain on the schedule, not less....
    Locomotive maintenance is an issue on all railroads, and as it goes, Amtrak does a pretty respectable job of maintaining what can be considered an elderly fleet.  The schedule is what it is, and the power assigned is based upon many factors, both permanent and temporary, schedule being just one part of the equation.
    The Empire Builder is pulled by two locomotives from Chicago to Spokane, where the train is split into Portland and Seattle sections. One locomotive is used to power the Portland section, whilst the other powers the Seattle section.


    Now that kind of makes sense, if they are going to be spilling the train, but wouldn't it be cheaper just to store a locomotive in Spokane instead of running it every time to Chicago and back?
    The Builder contends with one of the toughest grades in Montana and two units are needed to power the train on that grade and maintain that nasty old schedule.  Remember, HEP reduces the second unit's traction output considerably, more than the 700 hp quoted elsewhere.
    Don't forget that as much as 700hp. is diverted to providing hotel power to the train. Then you have situations like on the climb out of the Colorado River basin to the top at Yampai Summit, over 100 miles of near steady 1.4% which all but the hottest freights climb at 25 - 30 mph. and Amtrak climbs at 70 mph. And then consider on a route like that if you lose a Diesel you have no AC in the summer and no heat in the winter if you have only one locomotive.


    Don't all passenger locomotives have head end units which provide the electric power for the train? And those units are separate from the prime mover, correct? I know that if you look through the back door of a genesis loco you see a second, smaller diesel in the back room. Also, regarding speeds through the mountains, if a helper loco is truly needed to maintain speed on a grade, wouldn't a helper district make much more sense than running the locomotive the whole distance to and from Chicago?
    Head end power as provided by an Amtrak P42 reduces the horsepower available for traction by considerably more than the 700 hp quoted above.  What you see in the back is in fact the air compressor and its components and a small generator which develops HEP off the prime mover.  There is no auxiliary diesl engine on a P42.
    FYI I'm not trying to offend anyone for the posts and thank you very much for giving feedback, I'm just playing devil's advocate here, and I'm trying to find the correct answer!

    Serving Los Gatos and The Santa Cruz Mountains with the Legendary Colors of the Espee. "Your train, your train....It's MY train!" Papa Boule to Labische in "The Train"