nfotis beaulieu So here is a typical mixed manifest train on the Soo Line with the count and weight as it departed LaCrescent, MN yesterday after making a pickup and setout; Train 270 (St. Paul to Kansas City) 97 loads 79 emptys 14,587 tons That yields a TPOB of 84.3, on the BNSF that train would be allowed to run at 60 mph. The train had 2 SD60s and a SD40-2 for 10,600hp or 0.72hp per ton. Let's see: 97+79 = 176 wagons (or 'brake sets', if you prefer) 14587 / 176 = 82.9 - how do you get the TPOB of 84.3? You did discount some inoperative wagons? Also, I would like to note that 0.72 hp/ton is too low for European standards. We would typically have ten times that amount on electrified lines which carry passenger traffic (and we could have grades as steep as 2.6% in routes like the Gotthard in Switzerland). The very low cost of electricity compared to diesel permits such fast freight trains in European rails. Cheers, N.F.
beaulieu So here is a typical mixed manifest train on the Soo Line with the count and weight as it departed LaCrescent, MN yesterday after making a pickup and setout; Train 270 (St. Paul to Kansas City) 97 loads 79 emptys 14,587 tons That yields a TPOB of 84.3, on the BNSF that train would be allowed to run at 60 mph. The train had 2 SD60s and a SD40-2 for 10,600hp or 0.72hp per ton.
So here is a typical mixed manifest train on the Soo Line with the count and weight as it departed LaCrescent, MN yesterday after making a pickup and setout;
Train 270 (St. Paul to Kansas City)
97 loads
79 emptys
14,587 tons
That yields a TPOB of 84.3, on the BNSF that train would be allowed to run at 60 mph.
The train had 2 SD60s and a SD40-2 for 10,600hp or 0.72hp per ton.
Let's see:
97+79 = 176 wagons (or 'brake sets', if you prefer)
14587 / 176 = 82.9 - how do you get the TPOB of 84.3?
You did discount some inoperative wagons?
Also, I would like to note that 0.72 hp/ton is too low for European standards.
We would typically have ten times that amount on electrified lines which carry passenger traffic (and we could have grades as steep as 2.6% in routes like the Gotthard in Switzerland).
The very low cost of electricity compared to diesel permits such fast freight trains in European rails.
Cheers,
N.F.
Thus the differences between US and Europe and their operating philosophies.
Europe - #1 Passenger #2 Freight (to the extent it doesn't affect passenger)
USA - #1 Freight - #2 Passenger (to the extent it doesn't affect freight)
The European rail route structure was seriously damaged during WW II and needed to be rebuilt from the subgrade up after the War. A rebuilding that was undertaken with primarily public funding and used state of the art technologies as they became available during the after war years. Petroleum is a scarce commodity in Europe and must be imported at relatively high costs (witness the evolution of car maker products in Europe vs US products of the same age). Since the European railroads needed to be totally rebuilt, the incremental costs associated with electrification vs. imported petroleum made electrification the economical way to go.
The US rail route strucure sustained no damages from WW II, other than to be heavily used with minimum investments into maintaining and improving the rplant. At the conclusion of the War the US was left with a well worn physical plant and worn out motive power that had exceeded it's economic life and was in need of immediate replacement. Both physical plant and motive power enhancements would have to be undertaken with private investment funds by carriers that existed in a highly over regulated financial world. Rules that were designed to limit the carriers abilties to return a profit on the investment, as the carriers were still viewed as the 'Robber Barons' from the first part of the 20th Century. In the immediate after War years the US was awash in cheap petroleum, thus the decisions were made that the diesel-electric locomotive was the more economical choice than the additional investments that would be required to electrify large route segments of the US (in fact the Great Northern, Milwaukee Road and Virginian (after being merged into Norfolk Western) removed their electrified territories in favor of the through operation of diesel-electrics.
The public investments in the US during the after War period went into improving the highway system of the country, in direct competition to the privately financed railroads - is it any wonder the US railroads had trouble attracting investment at affordable rates? The inability to attract affordable investment after the War was the cause of the financial collapse of many carriers in the late 60's & early 70's and what brought about the Staggers Act of 1980 that released the US railroads from their financial prison.
The present day operations of railroads in Europe and the US are vastly different due to their vastly differenty post War financial histories.
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beaulieu So here is a typical mixed manifest train on the Soo Line with the count and weight as it departed LaCrescent, MN yesterday after making a pickup and setout; Train 270 (St. Paul to Kansas City) 97 loads 79 emptys 14,587 tons That yields a TPOB of 84.3, on the BNSF that train would be allowed to run at 60 mph. The train had 2 SD60s and a SD40-2 for 10,600hp or 0.72hp per ton. JB
JB
Using a little calculator I built a while back, looks like this train would balance out at roughly 41 mph on the level with no wind and would be good for a ruling grade ~0.75%. It could get to 60 mph on a 0.18% down grade.
-Don (Random stuff, mostly about trains - what else? http://blerfblog.blogspot.com/)
Ironeagle2006 Doing my Math and figuring out the Physics in my head that Engineer maybe had a top end of around 45-50 MPH before he flat out ran out of TE on the Engines. Any Curvature or Slight Grade up and he was going to be on his KNEES. But then again when CNW first broke into the Powder River Basin UP would move the 15K ton trains with only one SD60M on the point.
Doing my Math and figuring out the Physics in my head that Engineer maybe had a top end of around 45-50 MPH before he flat out ran out of TE on the Engines. Any Curvature or Slight Grade up and he was going to be on his KNEES. But then again when CNW first broke into the Powder River Basin UP would move the 15K ton trains with only one SD60M on the point.
Very little railroad mileage is truly level - watching the load meter on a tonnage train will tell you where the grades are that your eyes can't see - and there are a lot more of them than you realize.
With that loading - being allowed to run 60 MPH and being able to run 60 MPH with the power listed are two different realities.
nfotis Hello, if I understand correctly, TPOB means tonnes per wagon brake rig?
Hello,
if I understand correctly, TPOB means tonnes per wagon brake rig?
Almost, once in a while a train will have to move a car with inoperative brakes, so the acronym means Tons Per Operating Brake.
I mean, you have two bogies, each with its own brakes. You seem to say that these two bogies must carry no more than 100 tonnes (total wagon weight?) if the loaded train is permitted to operate at 60 mph (nearly 100 km/h).
Each two bogie freight car has a single brake cylinder located near the middle of the freight car that applies the braking force to the brake shoes via beams and levers, so all normal freight cars have one brake system and are counted as one. Articulated Piggyback Flatcars and 5 section Doublestack Well Cars are different. US freight cars carry heavier weights than those in Europe, many freight cars have a loaded weight of 134 tons, but the majority of freight cars built in the last 10 years have a loaded weight of 143 tons. So it will take a fair number of empty freight cars to get the average down.
This is reasonable, we in Europe have similar constraints but expressed in metric tonnes/axle usually (typical situation): - run at 20 tonnes/axle load: 120 km/h (75 mph) - run at 22.5 tonnes/axle load: 100 km/h (62 mph) So, a 4-axle wagon could run on a flat or rising route at up to 62 mph loaded at 90 metric tonnes (= 99 tons) total weight. That is practically equivalent between us, don't you think? The speed limit on down grade does have to do with the combination of grade and kinetic energy, and it must include: track curvature and thermal capacity of air brakes. As per the NTSB report mentioned above, the dynamic braking must not figure in this calculation - the air brakes must be enough for fully stopping the train. Now, what happens when you have empty wagons in your train? Does their braking force enter the calculation? I suspect that the numbers you quoted above are *average* numbers for the whole consist. N.F.
This is reasonable, we in Europe have similar constraints but expressed in metric tonnes/axle usually (typical situation):
- run at 20 tonnes/axle load: 120 km/h (75 mph)
- run at 22.5 tonnes/axle load: 100 km/h (62 mph)
So, a 4-axle wagon could run on a flat or rising route at up to 62 mph loaded at 90 metric tonnes (= 99 tons) total weight. That is practically equivalent between us, don't you think?
The speed limit on down grade does have to do with the combination of grade and kinetic energy, and it must include: track curvature and thermal capacity of air brakes. As per the NTSB report mentioned above, the dynamic braking must not figure in this calculation - the air brakes must be enough for fully stopping the train.
Now, what happens when you have empty wagons in your train? Does their braking force enter the calculation? I suspect that the numbers you quoted above are *average* numbers for the whole consist.
nfotis You are right in that kinetic energy is related to the square of speed. But then you seem to forget that brake force is not proportional to speed, either. And I have not mentioned ECP brakes. Note that going down a mountain is not so much about managing kinetic energy, but rather you manage gravitational potential energy (= height difference). According to the train handling applied, this potential energy will get converted to heat (via braking), electricity (regenerative rheostatic braking) or kinetic energy.
You are right in that kinetic energy is related to the square of speed. But then you seem to forget that brake force is not proportional to speed, either. And I have not mentioned ECP brakes. Note that going down a mountain is not so much about managing kinetic energy, but rather you manage gravitational potential energy (= height difference). According to the train handling applied, this potential energy will get converted to heat (via braking), electricity (regenerative rheostatic braking) or kinetic energy.
BNSF's System Special Instructions says that trains having a weight of less than 100 Tons per Operative Brakes allowed to operating at a speed of 60 mph, any train having a weight of 100 Tons per Operative Brake or more is limited to a top speed of 45 mph. Of course speeds can also be limited due to Hazmat cars, or curves, or grades, or turnouts, or other speed restrictions.
Here is the restriction for Cajon Pass on the North Track (the easier grade), without helpers
Speed limit if train weight does not exceed 6500 tons and 95 TPOB 30mph
Speed limit if train weight exceeds 6500 tons or 95 TPOB 20mph
Train not permitted to operate if it exceeds 14,000 tons
With helpers
Speed limit if train does not exceed 6500 tons and 135 TPOB 30 mph
Speed limit if train does exceed 6500 tons but less than 12,000 tons and not more than 135 TPOB 25mph
Speed limit if train exceeds 12,000 tons but does not exceed 135 TPOB 20mph
Train must not operate if it exceeds 16,000 tons or exceeds 135 TPOB
Also, dynamic (and rheostatic) braking in locomotives becomes more powerful all the time, to the point that it may damage the couplers when being in multiple traction, so you have to limit this. Of course, even in a slow train you can bleed the air or do repeat brake applications in a way that zeroes the braking capability. Going slowly might give you some time to recharge the air brakes (maybe) while dynamic brakes try to keep the train under control. The UIC railways have graduated air brakes, which behave differently (you can apply X braking power, then Cheers, N.F.
Also, dynamic (and rheostatic) braking in locomotives becomes more powerful all the time, to the point that it may damage the couplers when being in multiple traction, so you have to limit this.
Of course, even in a slow train you can bleed the air or do repeat brake applications in a way that zeroes the braking capability. Going slowly might give you some time to recharge the air brakes (maybe) while dynamic brakes try to keep the train under control.
The UIC railways have graduated air brakes, which behave differently (you can apply X braking power, then
cat992c Are these being made in Muncie???
Are these being made in Muncie???
Well, first I didn't say you would use these more powerful locomotives for going downgrade
(if I left such an impression, apologies - English is not my native language)
Second, I did not speak about moving heavy trains at 100+ mph. Rather, I suggested e.g. going from 20mph to 40mph upgrade, in order to have more homogeneous train speeds.
The UIC railways have graduated air brakes, which behave differently (you can apply X braking power, then raise it to Y and later return to X without the need to release brakes fully for recharging air - the price for this is slower reaction in very long trains).
Witness the Malmbanan in Sweden, where 8500 metric tonnes iron ore trains go downgrade from Kiruna to Narvik with a single two-section IORE electric locomotive, at some really nasty grades.
Braking power is fully discussed in this NTSB derailment report
http://www.ntsb.gov/doclib/reports/2002/RAR0202.pdf
nfotis @beaulieu: Really, I do not understand this argument about stopping/braking trains. After all, braking power rises symmetrically with the number of wagons. N.F.
@beaulieu:
Really, I do not understand this argument about stopping/braking trains.
After all, braking power rises symmetrically with the number of wagons.
Double the cars you double the braking power, double the speed you need to quadruple the braking power. Take a loaded coal train from 40 to 60 mph, the stopping distance will about double. North American freight cars when loaded are about 60% heavier on the same number of axles, compared to European freight wagons. While I believe North America freight have more braking power, they don't have 60% more.
Any citation please?
The percentage looks extremely high to me for conventional single-track operation, and it could probably attained while 'ganging' groups of trains (three eastbounds in a row, three westbounds after that, etc.)
Note that accelerating/decelerating a heavy freight train for entering/leaving a siding means much less capacity compared to a steady parade of dedicated tracks for each.
To tell the truth, whatever improvements are done on the mainline, if you yards are plugged and without capacity to accept/deliver trains you will be severely limited in throughput.
A single track main line with an adequate number of sidings can run 80% of the traffic of a two track main line.
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I put forth the argument that horsepower is needed if you want a fluid railroad.
With the same number of locomotives you can get higher productivity. Obviously, if you have a single-tracked railway with sidings, this advantage will be lost.
efftenxrfe Pete1950 directs this correctly. Consider loadmeters show amperage representing one or two moter's draw from the engine/generater. Consider that at starting a train, amperage may get to 1250 (or more). 6-moters at 1250 amps. Horsepower is 740 or-so watts. Watts are volts times amperes. Locomotive generaters max out at about 900 volts, though 600 volts is the advertised rate. So, solve for 6 moters at 1200 amp's using 600 (or so) volts and look at the HP required to produce 1200 amps, based on 740 watts a horsepower. Ed Wheelighan explained this to me in '1981 from EMD to the SP Engine Service Training Center during fuel-saving directives.
Pete1950 directs this correctly. Consider loadmeters show amperage representing one or two moter's draw from the engine/generater. Consider that at starting a train, amperage may get to 1250 (or more).
6-moters at 1250 amps.
Horsepower is 740 or-so watts.
Watts are volts times amperes.
Locomotive generaters max out at about 900 volts, though 600 volts is the advertised rate.
So, solve for 6 moters at 1200 amp's using 600 (or so) volts and look at the HP required to produce 1200 amps, based on 740 watts a horsepower.
Ed Wheelighan explained this to me in '1981 from EMD to the SP Engine Service Training Center during fuel-saving directives.
nfotis Well, tractive effort is depending on weight on driver wheels (and adhesion factor), not horsepower per se. If you can, compare tractive effort curves from the same locomotive platform but with different horsepower. You will note that, up to the 'critical speed' (which is weight-limited) the performance is the same, but the curve that falls slowly (and which is horsepower-dependent) is moved to the right. F=m*a is the whole story after the critical speed. And 'horsepower talks' if you are not doing a coal drag but you want to have a fluid railroad, since you can keep the same speed with fewer locomotives (you can have two 6000hp locomotives instead of three 4300hp ones). Obviously, European electrics are different beasts, but I would like to see the incoming Amtrak 6.4MW boxes pulling fast freights as an experiment. For USA locomotives, the practical limit is either a 20-cylinder 710G motor (around 5500hp) or a pair of medium speed diesels like the Caterpillar C175 or the MTU R4000 with automatic start-stop for better fuel economy (you keep only the one diesel for switching or idling). Cheers, N.F.
Well, tractive effort is depending on weight on driver wheels (and adhesion factor), not horsepower per se.
If you can, compare tractive effort curves from the same locomotive platform but with different horsepower. You will note that, up to the 'critical speed' (which is weight-limited) the performance is the same, but the curve that falls slowly (and which is horsepower-dependent) is moved to the right.
F=m*a is the whole story after the critical speed.
And 'horsepower talks' if you are not doing a coal drag but you want to have a fluid railroad, since you can keep the same speed with fewer locomotives (you can have two 6000hp locomotives instead of three 4300hp ones). Obviously, European electrics are different beasts, but I would like to see the incoming Amtrak 6.4MW boxes pulling fast freights as an experiment.
For USA locomotives, the practical limit is either a 20-cylinder 710G motor (around 5500hp) or a pair of medium speed diesels like the Caterpillar C175 or the MTU R4000 with automatic start-stop for better fuel economy (you keep only the one diesel for switching or idling).
No matter the Horsepower or Megawatts
Wheel slip control is the name of the game to move freight.
Well, as you noted, this was an exceptional case which involved a locomotive that ceased production in 2001 according to http://en.wikipedia.org/wiki/GE_AC6000CW
European electric locomotives like the TRAXX (the light sister of the ALP-46) or the Vectron (small sister of ACS-64) are in production today, with power to the rails ranging from 5.2 to 6.4 MW
(note that the diesel prime mover ratings lose 15-20% when these apply to the rails, so the difference is even more pronounced).
At any rate, I hope that I made my point about the limits of power per axle: the current state of the art is nearly 2.000/axle.
The mechanical dept. folks at CSX would disagree with you about that..they were satisfied enough with the performance of their AC6000CW fleet to rebuild them with newer 16 cylinder GEVO engines with the same HP rating.
So although the North American industry as a whole didn't not find 6,000 HP diesels to be cost effectice there is that significant exception..
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Well, if Europe is not a fair comparison, what about China?
http://en.wikipedia.org/wiki/Daqin_Railway
In this route, they are handling 20.000 metric tonnes coal trains with locomotives like this one:
http://en.wikipedia.org/wiki/China_Railways_HXD1
And you can see these lowly locomotives in action:
http://www.youtube.com/watch?v=AoLxOJM0z9A
And to give an additional data point, the 4-axle Siemens Vectron in their 6.4 MW configuration can pull a 1600 metric tonnes train at up to 120 km/h, or a 550 tonnes passenger train at 200 km/h
(conversion to imperial units is left as an exercise to the reader )
When speaking about diesel locomotives pulling freight trains at rather grades, typically it is preferable to use the smallest possible prime mover for going over the hump, as the fuel consumption is directly proportional to horsepower. The higher speed does not gain enough time for balancing the higher fuel consumption, as I have found from my simulations.
nfotis For this reason, modern electric locomotives like the Bombardier TRAXX have a 'tractive effort limiter' in software. If my memory serves me correctly, when working in double-heading, such locomotives limit automagically the coupler effort to 250 kN each (total 500 kN in double heading), in order to avoid breaking the anemic UIC screw couplers in mountain routes (grades up to 2.8% - in Alpine routes, so you need all the horsepower you can get, if you want to keep the railroad fluid). Of course, after the 'critical speed' you give it all the power you can get. Cheers, N.F.
For this reason, modern electric locomotives like the Bombardier TRAXX have a 'tractive effort limiter' in software.
If my memory serves me correctly, when working in double-heading, such locomotives limit automagically the coupler effort to 250 kN each (total 500 kN in double heading), in order to avoid breaking the anemic UIC screw couplers in mountain routes (grades up to 2.8% - in Alpine routes, so you need all the horsepower you can get, if you want to keep the railroad fluid).
Of course, after the 'critical speed' you give it all the power you can get.
Europe isn't handling 6500 foot 20000 Ton trains on 1 & 2 percent grades.
The CSX limit is 2 6 axle AC + 1 dash-8 DC for max tonnage unit trains. Max tonnage mixed freight trains is 3 Dash-8's.
TE of 3 AC's exceeds the published knuckle strength of the high tensile knuckles used in unit train service; additionally with the high degree of curvature that is in the CSX mountain routes excessive power on the head end makes stringlining a real possibility.
N.F. !!!!
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I just started my blog site...more stuff to come...
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I am wondering if railroads could get away with 2x 4000/4400 HP AC locomotives and a 6 axle AC slug between them instead of 3 4400 AC locomotives in low speed coal service?
They could use 3x 3000HP AC locomotives, if such a beast were available, but it would be more fuel efficient to use 2 AC locomotives and an AC slug if that would provide sufficient HP when combined with the 18 powered AC axles.
The high power to the motor is great if you are looking for lots of speed. Will that locomotive generate 200,000 lbs of 'continuous' tractive effort? Remember, we are dealing with a self contained power supply in a diesel electric. And as mentioned, 43-50% adhesion is the practical limit right now - adding HP will add little except cost - unless you are looking for super acceleration. This is not the AAR 'Nationals' drag race!
Jim
Modeling BNSF and Milwaukee Road in SW Wisconsin
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