Heavier locomotives move more tonnage, pretty simple. In the weight range that we're talking with these units the fuel consumption isn't even worth mentioning as is barely affected in the slightest.
ML
Heavier locomotive means more pulling power. Modern freight locomotives produce enough torque in their electric motors to spin their wheels without moving unless they are heavy. Normal SD70ACe locomotives had a reputation for being a bit slippery, especially in wet weather. The Heavy version does not have that problem.
AC locomotives are limited by their adhesion, their ability to grip the rail. Adding weight increases the adhesion.
So adding few tons to a locomotive in the form of a big block of concrete adds what to the tractive effort and at what cost? Is the small amount of additional tractive effort worth the cost of a few tons of concrete?
caldreamer So adding few tons to a locomotive in the form of a big block of concrete adds what to the tractive effort and at what cost? Is the small amount of additional tractive effort worth the cost of a few tons of concrete?
A few tons of concrete costs almost nothing when compared to the 2 million plus cost of a new locomotive. If we are talking about the amount of extra fuel needed to move the extra couple of tons look at it this way. A coal train weights in around 18000 tons, do you think a few extra tons is really going to make a difference?
An "expensive model collector"
Yes.
CSX has been doing this with a large portion of their AC fleet for the last decade or so. They have done a great deal of testing and found that the increased tractive effort offers some significant improvements in train performance, particularly in coal drag service in mountainous territory.
"I Often Dream of Trains"-From the Album of the Same Name by Robyn Hitchcock
NorthWest AC locomotives are limited by their adhesion, their ability to grip the rail. Adding weight increases the adhesion.
You have the right idea, just some clarification on terms.
Adhesion is how well the wheel "sticks" to the rail. It's expressed as the ratio of tractive force/locomotive weight - usually as a %. An AC locomotive might have 35% adhesion. How much tractive force (tractive effort) it can generate depends on it's weight. The heavier, the harder it can pull.
-Don (Random stuff, mostly about trains - what else? http://blerfblog.blogspot.com/)
To add a bit more: Compare the added weight to the overall mass of a loaded train; the additional fuel burn could be measured with sensitive equipment, but is substantially exceeded by the money advantages of being able to use more of the 'available' power of the AC traction motors, and perhaps by the real-world reduction in slipping/microslipping provided by better adhesion.
CSX has essentially standardised on 432,000lbs as the weight of their modern road power since the AC4400s (#475 iirc and full scale orders of heavy CW44AHs starting with the 500s) and NS has also since been buying it's ES44ACs and SD70ACes at the same 432klbs weight. In this case also the weight is not concrete as it doesn't have as much density as steel does, with the new built locomotives the weight is added in the form of thicker frame steel and other bits and pieces, in the case of the CSX AC44s that got weight added it was added in the form of extra steel welded into whatever space they could find. CSX also ballasted up it's SD70MACs (seen by a raised walkway along the right hand side and plates added along the face of the left hand side walkway) before it also got heavy SD70MAC-T1s.
It's quite clear that any fuel usage loses are more than made up for by tonnage increases.
Thanks, Don. I was struggling to find the best words to explain it!
Fairbanks-Morse was the only builder to make use of concrete as ballast in locomotives.
I would still like to kno wwhat the starting continupous tractive efforts are for the SD70Ah and ES44AH's.
200,000-216,000lbs depending on rail conditions.
GDRMCo 200,000-216,000lbs depending on rail conditions.
An ES44AC or SD70ACe that has been ballasted to 432,000lbs and is also equiped with the High Tractive Effort software can only produce a maximum of 200,000lbs tractive effort. This is a software limitation. These units could produce more than 200,000lbs tractive effort but there is concern for wheel and rail damage.
While UP's SD70AH and C45AH's are equiped with extra ballast bringing the units in the 427,000-428,000lb range they lack the High Tractive Effort software. In this case these units will only produce slightly more tractive effort than the standard weight SD70ACe's and C45ACCTE's on the UP roster. To reach the 200,000lb maximum tractive effort these locomotives would have to have both the additional ballast and HTE software. The CSX specification takes things a few steps further, requiring not only the additonal ballast and HTE software but rail conditioners and steerable/radial trucks.
AC traction locomotives are not the only ones to benefit from additional ballast, DC traction units also benefit. The whole heavy, high tractive effort locomotive program on CSX was inspired by a similar effort of the Western Maryland RR which had a pair of new SD40's ballasted to 420,000lbs in an effort to increase tractive effort/adhesion. This is why CSX chose to have its fleet of ES44DC's ballasted to 432,000lbs. In years past Burlington Northern had ordered SD40-2's weighing 425,000lbs and Chicago & North Western C40-8's weighting 420,000lbs, among others.
Bryan Jones
What happened to the 36K software then?
Since a cubic yard of concrete costs around $80 and can weigh up to 4000 lbs then I would definitely say an $80 "investment" in more tractive effort from a multi-million dollar locomotive is "worth it".
My first read of this thread just happened, and a statement in July of this year said that FM was the only user of concrete ballast.
Well, SP bought about 200 GP9's, in the 1950's, that had a circular, about 4 feet in diameter, steel cylinder about 3, maybe more, feet high. It lived in the short hood of the engs without steam generators.
The cylinders were full of concrete...
oltmannd NorthWest AC locomotives are limited by their adhesion, their ability to grip the rail. Adding weight increases the adhesion. You have the right idea, just some clarification on terms. Adhesion is how well the wheel "sticks" to the rail. It's expressed as the ratio of tractive force/locomotive weight - usually as a %. An AC locomotive might have 35% adhesion. How much tractive force (tractive effort) it can generate depends on it's weight. The heavier, the harder it can pull.
in some of the original tests with the SD60MACs on Monument Hill adhesion levels as high as 45% were experienced.
A few extra tons on one locomotive is more efficant than running an extra locomotive
I think the front around the cab would be a better place to add metal. Construction companies sometimes use large 1" or so thick steel plates to cover holes in streets when they are working on utilities. One of them that is 8'x10' weighs several tons.
Modeling the "Fargo Area Rapid Transit" in O scale 3 rail.
thank you :)
When CSX used Dash-8's as their standard coal power, the normal size train was 90 cars.
When the AC's became the standard coal power, the normal train sized increased to 100 cars.
With the Heavy AC's being the standard coal power, the normal train size has become 110 cars.
Each increase in train size has permitted 1000 net tons of additional freight to be moved per train. The revenues from additional tonnage per train mount up.
Never too old to have a happy childhood!
Bryan Jones GDRMCo 200,000-216,000lbs depending on rail conditions. An ES44AC or SD70ACe that has been ballasted to 432,000lbs and is also equiped with the High Tractive Effort software can only produce a maximum of 200,000lbs tractive effort. This is a software limitation. These units could produce more than 200,000lbs tractive effort but there is concern for wheel and rail damage. While UP's SD70AH and C45AH's are equiped with extra ballast bringing the units in the 427,000-428,000lb range they lack the High Tractive Effort software. In this case these units will only produce slightly more tractive effort than the standard weight SD70ACe's and C45ACCTE's on the UP roster. To reach the 200,000lb maximum tractive effort these locomotives would have to have both the additional ballast and HTE software. The CSX specification takes things a few steps further, requiring not only the additonal ballast and HTE software but rail conditioners and steerable/radial trucks. AC traction locomotives are not the only ones to benefit from additional ballast, DC traction units also benefit. The whole heavy, high tractive effort locomotive program on CSX was inspired by a similar effort of the Western Maryland RR which had a pair of new SD40's ballasted to 420,000lbs in an effort to increase tractive effort/adhesion. This is why CSX chose to have its fleet of ES44DC's ballasted to 432,000lbs. In years past Burlington Northern had ordered SD40-2's weighing 425,000lbs and Chicago & North Western C40-8's weighting 420,000lbs, among others. Bryan Jones
The heavier weight provides maximum speed on the maximum grade with maximum tonnage. Its purpose is to speed up heavy trains on slow heavy gradient territories.
the real question is what is the point in building any SD70? These are pathetic slippery, painfully noisy droning engines with a solid cab and bouncy make you vomit engines with the isolated cab. Adhesion is a joke, verifiable only in perfect lab conditions. The reality is that they slip and spin and lose speed and stall because the computer won't let a whiskered hogger apply sand at the right time. Then there's the obnoxious loud bell warning that the lights will turn off soon followed by the stupid bell ringing warning that the lights actually will turn off now just to make sure you don't get that desperate safety nap.
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