IRB Souther Engineer Interesting points. I just wanted to comment that I recently talked to a 3rd generation railroader, now working as a CSX conductor. I asked him about slugs, and his response was, "They're good...until they get over 30 mph, then they're just dead weight."
Interesting points. I just wanted to comment that I recently talked to a 3rd generation railroader, now working as a CSX conductor. I asked him about slugs, and his response was, "They're good...until they get over 30 mph, then they're just dead weight."
That is absolutely correct for a diesel. The diesel looses TE linerally to 30 MPH so all the available HP can go to just the loco's traction motors. However with an electric motor the power available can be much higher HP. Even presentl 4 axel passenger motors can provide 8000 HP. So a heavier 6 axel motor could easily provide the power to a road slug that would not exceed the weight / TE limit. Some extra weight in the motor would probably be needed for slug control??
A single 8000 HP electric motor probably could not be able to overcome TE / weight limitations ?? Al Krug any comments ?
blue streak 1 8. one solution would be for electric motors to be joined with a road slug for weight limited TE starting trains?
8. one solution would be for electric motors to be joined with a road slug for weight limited TE starting trains?
BaltACD brings up very important points. I would add the need for constant speeds of all traffic over any certain track in Europe is very important..
I would like to give a very hypothetical example of what is needed. i WILL USE as a base a 4400 HP locos and motors with no slow orders and 70 - 80 MPH tracks. I will leave the actual number calculations to others as I am out of town and do not have the figures handy. Will ignore wind and rolling resistance -----
1. On a completely flat track (the closest example would be the FEC ) say 1 loco can start and move a train of "X" tonnage 20 MPH with a tractive effort of "Y".
2. Add a second locomotive and the max speed will be approximately 40 MPH with the same "X" tonnage.. Additionally acceleration will be quicker with "2Y" tractive effort above the weight /t tractive effort limit.
3. Add a third loco and now tractive effort is "3Y" for quicker acceleration above the drawbar limits of the locos and first few cars. Now the max speed is approximately 60 MPH.
4. So do I want to run the train at 20MPH with one loco for "3Z" minutes or 3 locos at "Z" minutes? With many trains over a route it will take about the same number of locos, reduced crew costs, about the same number of HP hours with some more fuel useage. It will increase car availability, less train waiting in siding on single track lines with sidings, make customers happier with faster delivery times.
5. With a 3 loco consist the failure of one loco will not stop a 1 loco train or slow a 2 loco train to 20 MPH.
6. Electric loco motors fit the same set of operating sets.
7. 2 motors would not accelerate as fast until they equaled 3 diesel locos tractive effort at ( ? ) speed. But electric motors can provide much higher HP that can be used at higher speeds to give more TE.
9. The running of very many intermodal trains over a route might (?) change the equation for diesel Vs Electric. If an intermodal route was all 70 MPH maybe the reduction of # of motors might (?) tip towards electrification as HP / weight ratios are very high on intermodals.
Hello BaltACD;
In terms of power outpout each of the 2 Motors shown can develop 5600 Kwor 7560 'European' Hp (there is a very slight difference between 'European' and 'Marecican' Horsepower, wich is less than 3%).
In terms of territory and grades, these trains (3 per day in 'peak' coal season) travel some 200 miles betewen a deep water port and a power plant. At the beginning of each 'loaded' trip, each train, carrying about 2000 nmetric tons, has to overcame, in the first 20 miles of so, grades in the vicinity of 2%. The rest of the trip is fairly easy with only short streches of 1 to 1,5% in short segments. Only near the end, in order to access the power plant by means of a dedicated branch, tough grades (2%) are found again, together with right curves. In the 'plains' (I've seen it more than once) soemtimes only one engine is used. However, these locomotibes, despite all the huge horspower avaukabkl, have a 'general tendance' of poor appliance of all its installed horsepower in an efficient manner due to lack of enough adhesive weight (something that seems to plague electric engines), and even with a bunch of technical 'aids' (microprossessor controls), that cannot be overcome, hence the 'reduced' load (each car carries 90 metric tons of coal). Curiously or not, when all the line was electrified, the total load of this trains was reduced from 2280 metric tons to 1980 (prior to electrification the grade from the port was 'assaulted' by 3 3300 Hp diesels in MU), wich shows one of the biggest advantages of diesels - an adequate weight that translates in 'better' tractive effort.
In terms of electrification of freight main lines in the US, one of the biggest obstacles, besides the 'better ratio of tractive effort' for diesels, is the fact of having to spend a huge initial sum of money in a fixed plant asset (a lot of catenary, power substations every 30 to 60 miles, considering a 'modern' 1X25 or 2X25 AC system) , wich will be quite 'heavy' to maintain in teh future, making such investment justifiable only in busy corridors with a good traffic density (40 to 50 trains per day or better). That's maybe why it's not such an interresting investment for freight railroads, since contemporary diesles preform a good job.
In terms of traction, there were in the past (FL9s, British Rail Class 73) god examples of perfectly operational 'electrodiesels' and today teher are also some 'dual mode) (ALP45DPs, Frech 'BIBi Railcars) that can work ubder the wires and without it. The main problem, I think, is cost, because such units are far more expensive than a straight diesel, and besides that, such designs were developed with passenger services in mind, not freight.
Several factors of EUdifferences
1. Electric motors provide much higher HP & Tractive Effort (TE) than a diesel would. That is needed to provide the HP to go up grades at passenger speeds (60 - 70 ) MPH. Because of this higher TE requirement freights are shorter so not to pull the draft gear apart. Power requirements IMHO lean the locos toward electric moors.
2. In the US most freight RRs sacrifice speed to go up and down grades as the diesel HP is the same and 'TE increases as the loco slows down. For any grade there is a balance speed where TE = train load. ( with certain conditions ). There is a certain speed & lower ( different for each model loco and track conditions) where the TE would overcome the friction of the traction motor wheels so at that speed and lower TE is limited to a fixed number and the HP of the loco has to be reduced with a probable train stall.
3. I am sure others can give more reasons
I know about the 'lack of catenary' subject. Also the situation of a 'diesel being an electric locomotive with its own power source' is something that I know. Yet, and about the double track isseu, I've seen photos of double stack trains 'under the wires' (in 'Trains') in the vicibity of Philadelphia. I just think the big issue is the fact of electrification being a very expensive asset to maintain and install(all the poles, wire & substations), maning it quite a dificult investment to be justified to be profitable
Mario -
I have no idea of the grades involved in the territory of your video...but 2 electric motors (6000 to 8000 HP each?) on 22 cars (unless I miscounted) does not fit the US freight business model with either electric or diesel electric locomotives.
The standard bulk commodity train (coal, ore, grain etc.) has become between 90 & 130 cars loaded to the allowable 286K pounds per car (ie. trains of 12500 to 18500 gross tons) hauled by 2 or 3 Diesel-electric AC traction engines that are rated in the 4000 HP range.
The vast majority of the mileage of the US freight rail system was never built with electrification in mind.
Some rail economists attribute the investment in electrification of parts of the MILW's West Coast extension as being contributory to the company's bankruptcy (prime cause was the West Coast extension itself, regardless of motive power). The Great Northern removed their electrification when it became proved that diesel-electrics could operate through the electrified territory with equal speed and greater efficiency as no engine change would be required on either end of the electrified territory.
When Amtrak became the owner of the NEC, it effectively forced ConRail to remove most through freight traffic from the Amtrak owned trackage which was electrified; thus ConRail scrapped their electric freight engines as they could not be productively used.
The US carriers are currently responding to a governmental mandate for Positive Train Control - a mandate that is being conservatively estimated to cost $19 Billion for the routes specified (which are most of the major traffic corridors). Were these higher traffic corridors to be electrified my personal estimate of the cost would be three to four times the cost of PTC, or more; with what level of economic return?
Never too old to have a happy childhood!
Mario, the biggest reason that American freights don't use electric traction is that most of the trackage in the US lacks a necessary ingredient - catenary. If a diesel reaches the end of an electrified section, in either direction, it just keeps going. If a juice motor reaches the end of catenary it has to be traded off for something else. What else? A diesel, of course.
Secondarily, American railroads removed the catenary they did have so they could run higher loads - specifically, high double stacks.
I like the idea of catenary, but the American diesel loco is actually an electric loco that carries its powerplant with it. Back when, David P. Morgan (long-time Trains editor) described dieselization as "Electrification without wires."
Chuck
Everytime I see an american freight train in video, I wonder why not considering electric traction as a traction mode, such as this ... (warning the grade crossing bell is quite annoying)
watch?v=coK1beOIA
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