I saw a chart somewhere that showed how long it takes a train of a given weight to accelerate from zero to 40mph. It took a relatively long time (and distance!) to get that many tons moving from a stop.
I'm not an engineer but it seems to me that a disproportionate amount of fuel must be used in that initial effort to get from zero to 40 and once you're rolling along at 40mph with low friction steel on steel you're primarily only fighting wind resistance (and grades, where applicable). Is this the case? Does anyone have a sense of how lopsided that fuel usage is? For example, over a 100 mile haul from a stop does 10% of the fuel usage come in the first two miles? 20%?
RailRoader608I saw a chart somewhere that showed how long it takes a train of a given weight to accelerate from zero to 40mph. It took a relatively long time (and distance!) to get that many tons moving from a stop. I'm not an engineer but it seems to me that a disproportionate amount of fuel must be used in that initial effort to get from zero to 40 and once you're rolling along at 40mph with low friction steel on steel you're primarily only fighting wind resistance (and grades, where applicable). Is this the case? Does anyone have a sense of how lopsided that fuel usage is? For example, over a 100 mile haul from a stop does 10% of the fuel usage come in the first two miles? 20%?
Fuel usage is directly correlated to the territory upon which the train is operated. Climbing a grade uses more fuel than descending a grade - even lines that are nominally level have grades.
The manufacturers in their specs for a locomotive 'generally' have a spec for fuel consumption under load for each notch of the throttle. I don't know what those figures are except that Notch 8 uses more fuel than does Notch 1. Fuel consumption over a route will depend mostly on how much time the locomotive(s) spend in Notch 8.
For the most part oprating practices in Class 1 railroading today dictate that locomotives be loaded to maximum tonnage for the territory in which they operate. Maximum tonnage is dictated by the 'ruling grade' on a territory. Each territory will have different ruling grade depending upon the origin and desitnation of a run. On CSX Chicago to Willard the ruling grade is 0.3%; from Willard to New Castle it is 1%; New Castle to Cumberland is near 2% - each track segment has its own topography.
Never too old to have a happy childhood!
RailRoader608over a 100 mile haul from a stop does 10% of the fuel usage come in the first two miles?
If you decide what sort of train you want to simulate you can do a fair job of estimating its fuel consumption. Say, two 4400 hp locomotives and a hundred 143-ton cars. At full power it can do maybe 45 mph on the level, consuming 9-10 gallons per mile.
Offhand guess: consumption in the first two miles will be less than 60 gallons. (Won't have reached 45 mph by then, of course.)
RailRoader608 I saw a chart somewhere that showed how long it takes a train of a given weight to accelerate from zero to 40mph. It took a relatively long time (and distance!) to get that many tons moving from a stop. I'm not an engineer but it seems to me that a disproportionate amount of fuel must be used in that initial effort to get from zero to 40 and once you're rolling along at 40mph with low friction steel on steel you're primarily only fighting wind resistance (and grades, where applicable). Is this the case? Does anyone have a sense of how lopsided that fuel usage is? For example, over a 100 mile haul from a stop does 10% of the fuel usage come in the first two miles? 20%?
Aircraft manufacturers, e.g. Boeing, Airbus, Cessna, etc. have engineering curves for each model of airplane that they build. They show the fuel burn rate for each power setting. So, with the throttle wide-open for takeoff, the fuel burn rate is much higher than that for cruise, descent, etc.
Presumably the locomotive manufacturers have similar engineering curves, although I have not been able to find them.
I was a Certified Flight Instructor and Instrument Flight Instructor for many years. As I remember it, at 75 percent power a Cessna 182 Skylane burned 13.5 gallons an hour, but throttled back to 55 percent power, its fuel consumption rate dropped to less than 10 gallons an hour.
timz RailRoader608 over a 100 mile haul from a stop does 10% of the fuel usage come in the first two miles? I'm guessing less than that, if it's 100 level miles. If you decide what sort of train you want to simulate you can do a fair job of estimating its fuel consumption. Say, two 4400 hp locomotives and a hundred 143-ton cars. At full power it can do maybe 45 mph on the level, consuming 9-10 gallons per mile. Offhand guess: consumption in the first two miles will be less than 60 gallons. (Won't have reached 45 mph by then, of course.)
RailRoader608 over a 100 mile haul from a stop does 10% of the fuel usage come in the first two miles?
I'm guessing less than that, if it's 100 level miles.
Where will you find 100 level miles? The load meter finds grades that the eye can't see.
i read (long ago) that friction of a railcar is 7 lbs/ton (i think it's better today)
if a loco can provide a force of 14 lb/ton, then there is 7 lb/ton that accellerates the train.
from F=ma (and converting lb-force to mass, slugs), accelleration is 0.1 ft/s^2 (7lbf / (2000 lbs / 32.2)). 40 mph = 58.7 ft/s. And it will take 8.7 min to accellerate to 40 mph.
it takes 2.6 hr = (2.5 hours + 8.7/2 minutes) to travel 100 mile (ignoring slowing down).
approx 0.1 hour out of the 2.6 hours is required to accelerate at twice the power to maintain speed.
hence 5.6% of extra effort is required to accellerate train to speed over the course of 100 mile trip at 40 mph
are my calculations correct (handling mass in english units)?
greg - Philadelphia & Reading / Reading
old thread ... has some Gal/Hr charts in it from Jeff.
http://cs.trains.com/trn/f/741/t/209895.aspx
Burn rates, on level ground gallons per hour.
Notch C44AC SD70ACE
8 210 187
7 171 164
6 140 133
5 109 86
4 79 64
3 53 47
2 27 23
1 12 12
Idle 3 3
DB2 4 4
DB4 6 6
DB6 8 9
DB8 13 14
Jeff
JPS1I was a Certified Flight Instructor and Instrument Flight Instructor for many years. As I remember it, at 75 percent power a Cessna 182 Skylane burned 13.5 gallons an hour, but throttled back to 55 percent power, its fuel consumption rate dropped to less than 10 gallons an hour.
isn't the question comparable to: what is the fuel consumption to reach 10,000 agl vs maintaining 10,000 agl
gregc JPS1 I was a Certified Flight Instructor and Instrument Flight Instructor for many years. As I remember it, at 75 percent power a Cessna 182 Skylane burned 13.5 gallons an hour, but throttled back to 55 percent power, its fuel consumption rate dropped to less than 10 gallons an hour.
gregcisn't the question comparable to: what is the fuel consumption to reach 10,000 agl vs maintaining 10,000 agl
Not exactly, unless you specifically (no pun intended) incorporate both the figures for rate-of-climb and airspeed fuel burns into the example.
Part of accelerating a train is the irreducible amount of work in getting it up to a given road speed. More fuel would be required to 'get it there faster' and this is complicated by the dereferenced method a locomotive with, say, a Woodward governor controls the rate of train acceleration, which may result in modally higher fuel consumption for only marginal gain in speed-at-distance.
I am not certain that either the top speed of aircraft or ships, vs. cruise, is properly applicable to diesel-electric freight-train speed discussion, as those two are severely drag-limited at the higher speed ranges. The USS Intrepid requires only 250hp to run at 4 knots, but a godawful couple of hundred thousand at top declassified speed ... most of which is in the last few achieved knots.
BaltACDWhere will you find 100 level miles?
None of us knows much about a train's rolling resistance, but good a guess as any--
A hundred 143-ton cars, two 4400 hp diesels, level track: the first two miles will take 6+ minutes and they'll be doing 30 mph at that point. The first 15 miles will take 25+ minutes and they'll be up to 45 mph there, still full power, burning 9 to 10 gallons per mile. So how many gallons did they burn in the first two miles? Likely 40 or just under.
OvermodI am not certain that either the top speed of aircraft or ships, vs. cruise, is properly applicable to diesel-electric freight-train speed discussion, as those two are severely drag-limited at the higher speed ranges.
not sure why you're bringing up a ship in water.
like a plane, drag is proportional to the square of velocity. But i wasn't comparing the energy for a plane to reach cruising speed, I was comparing the recoverable energy used to attain altitude. A plane can convert that potential energy into kinetic (velocity) as it decends.
OvermodPart of accelerating a train is the irreducible amount of work in getting it up to a given road speed. More fuel would be required to 'get it there faster'
what do you mean by irreducible? ("not able to be reduced or simplified")
of course more fuel to accelerate faster, but over less time.
yes, energy used to overcome drag is non-recoverable
but because friction is small for trains, the momentum of a train, like altitude in a plane can be used to maintain speed for quite some time once power is cut.
i didn't factor the energy not required to maintain the speed of the train near the end of it's 100 mile trip. But i didn't think that was the OPs question.
timz BaltACD Where will you find 100 level miles? If you like some other profile better, go ahead and do the calculation for it. None of us knows much about a train's rolling resistance, but good a guess as any-- A hundred 143-ton cars, two 4400 hp diesels, level track: the first two miles will take 6+ minutes and they'll be doing 30 mph at that point. The first 15 miles will take 25+ minutes and they'll be up to 45 mph there, still full power, burning 9 to 10 gallons per mile. So how many gallons did they burn in the first two miles? Likely 40 or just under.
BaltACD Where will you find 100 level miles?
If you like some other profile better, go ahead and do the calculation for it.
Just stating the reality of railroads - there is very little level track - the grades involved are not mountains - a foot over a 1/4 mile here, 6 inches over 100 yards there - and that is where the CE's laying out the line did their best to engineer grades out of the line. In other territories where the lines were laid by companies without money - they are laid on top of the ground with undulating 1/2 and one percent grades.
Engineers calculations are great in theory - The real world operates on steel wheel on steel rail hauling tonnage on the lines that exist with all the elevation changes that exist.
Back in the days when Dash-8's were the prime road power for CSX and there was a systemwide restriction of 40 MPH on coal trains, I was working on the Atlanta Division at the time. The terrain around Atlanta is undulating - in fact most of the terrain of the state of Georgia, except along the Atlantic Coast, is undulating. Division Management appealed to System Management that the 40 MPH restriction was causing excessive fuel consumption, not saving it as the restriction was intended. Finally they were able to get System to consent to a test of nominally identical trains - two dash-8's and 90 loads of coal from Tilford Yard to Waycross, one observing the 40 MPH max speed and the other observing 50 MPH max speed. Tale of the tape - the 50 MPH train used 150 gallons less per unit than did the 40 MPH train. The 40 MPH train had to brake on the descending side of hills to not exceed 40 MPH and the train did not retain the momentum of the train to climb the next ascending grade and train had to use maximum throttle longer to climb the grade - time after time after time. The loss of kinetic energy with reduced speeds can and does have bad effects on fuel economy - when it comes to moving tonnage you have to utilize all the forms of energy that are available - kinetic and locomotive.
Thereafter Special Instructions allowed coal trains 50 MPH from Tilford to Waycross until that system operating regiem was changed and 50 MPH was allowed for all coal trains on the system.
BaltACDThe real world operates on steel wheel on steel rail hauling tonnage on the lines that exist
timz BaltACD The real world operates on steel wheel on steel rail hauling tonnage on the lines that exist Then feel free to answer his question for a 100-mile line that exists.
BaltACD The real world operates on steel wheel on steel rail hauling tonnage on the lines that exist
Then feel free to answer his question for a 100-mile line that exists.
To my knowledge there is no 100 mile level streach of railroad anywhere in the country, so there is no answer withing those constraints. Isn't it funny how lakes, rivers, creeks, streams - anywhere water flow creates changing elevations on the ground they move through or exist in.
I am a retired RAILROADER, not a engineer - I don't do engineering calculations.
BaltACDTale of the tape - the 50 MPH train used 150 gallons less per unit than did the 40 MPH train. The 40 MPH train had to brake on the descending side of hills to not exceed 40 MPH and the train did not retain the momentum of the train to climb the next ascending grade and train had to use maximum throttle longer to climb the grade - time after time after time. The loss of kinetic energy with reduced speeds can and does have bad effects on fuel economy - when it comes to moving tonnage you have to utilize all the forms of energy that are available - kinetic and locomotive.
kinetic and potential energy
doesn't this show that it's not how flat, but the absolute difference in altutude between the starting and end locations?
any extra energy (fuel) required to go up a slight grade is recovered (less/no fuel consumption) on the downhill side. (of course using brakes defeats and benefits). (and yes, there is extra loss at higher speed that is not equivalent to the lowerb loss at slower speeds).
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