I don't mean who runs the longest trains-- I mean, who demands the highest tractive effort from one unit, in their everyday operations?
GE says the ES44AC is supposed to be good for 166000 lb continuous TE-- which, if true, means maybe 7000 trailing tons on 1%, or 3000 on Cranberry-- and for all I know the latter might be the answer to the question. Does CSX try to run 12000-ton coal trains up there with four ACs?
The question has to do with the new BNSF order for A1A-A1A ES44ACs. Trying to account for it, people have theorised that a four-motor AC can equal a six-axle DC in all-out tonnage-lugging, despite having 2/3 the weight on drivers. In other words, they think the ACs are good for something like 38% adhesion day in and day out, not just on test. Wondering whether that's realistic, we next ask: does any US RR regularly demand that from their ACs?
If rail conditions on Cranberry Grade were ideal, four recently serviced CSXT high-tractive-effort ES44ACs would probably not stall with a 12,000-ton train; however normally their maximum train size is 11,600 tons. And if, in order to keep a train moving, it was necessary for the helper consist (which moves on rail conditioned by the passage of the train) to reach 46% adhesion, CSXT and GE would expect it to reach that adhesion level.
2900 tons per unit on Cranberry is going to be hard to beat, if such trains are everyday occurrences. Anybody know if such trains do show up there regularly? When they do show up, what's their success rate, and how much does it depend on the weather?
JayPotterCSXT and GE would expect it to reach that [46%] adhesion level.
timzBy "expect", you mean they consider the chances of it doing so to be... 99%? 95%? 90%?
The concept of predicting that a unit will produce a certain percent of adhesion a certain percent of the time was applied by EMD to its SD70MACs, SD80MACs, and SD90MACs; however it's not an approach that CSXT takes. If an eastbound drag to be dispatched out of Grafton is within the tonnage ratings of its head-end consist plus the helper consist that will later assist it, it will be dispatched. Otherwise it won't be dispatched until adjustments in tonnage or power are made.
Grafton routinely dispatches eastbound drags of somewhat less than 11,000 tons; and if the two head-end units are high-tractive-effort GEs (i.e. class CW44AH or ES44AH) the tonnage can reach 11,600.
Trains within their tonnage ratings do stall on Cranberry Grade; and this can be caused by one or more of a variety of reasons. One of the units could develop a sanding problem. Several of the units could be low on fuel. Snow on the ground could be so deep that brake riggings drag through it; or there could be enough accumulation on top of the coal to cause a significant increase in train tonnage. Contamination from wayside flange lubricators could be present at a location where the head-end consist will reach it at the same time that the helper consist reaches contamination at another location.
Whenever a train does stall on Cranberry Grade, CSXT determines the cause of the stall and takes whatever reasonable corrective action it can. In other words, the company doesn't begin to be concerned about stalls when a certain percent of trains are stalling. Its objective is to have no trains stall on Cranberry Grade.
I'm not sure if my last posting answered the question that was asked.
If the question was how frequently do the high-tractive-effort GEs on Cranberry Grade produce tractive effort equivalent to 46% adhesion, the answer is very seldom. This is because even if rail conditions allow that level of TE to be produced, it is not normally necessary to keep the train moving.
Production of that level of TE most often occurs on the helper consist when something causes a reduction in the TE being produced by the head-end consist. When this happens and the head-end TE decreases, there is a corresponding increase in the helper-consist TE. If, in order to keep the train moving, it's necessary for each of the helper units to reach and maintain 200,000 pounds of TE, they should do that
Timz,
Weight on Drivers is not how to measure 'Continuous TE' - Weight on drivers will give you a ball park figure for starting(breaking friction). Remember, there are 6 traction motors sucking up all of the juice. If you only have 4 traction motors, the output will be split only 4 ways. In theory, I suspect you could only have a single large traction motor(if you could fit it). When I worked for a railroad, we normally assigned 1.5 hp/trailing ton on our merchandise trains. 3 GP40's pulling 6,000 tons or 3 SD45's pulling 6,000 tons made little difference(other than the SD45's rode a lot better). Since we were running at 60 mph, the 750 hp/axle GP40's actually pulled better than the 600 hp/axle SD45's. The SD45's had the advantage of more 'dig' when starting a train. But with that much hp, the GP40's could move a train out of the yard just fine. In the case of what BNSF wants to do, it makes sense on paper. To hedge their bets, it is being done to only 25 engines and I suspect they will be able to convert them to standard GEVO's if the experiment does not work out.
Now, your example of running a heavy coal train up a mountian grade is just not what BNSF wants to do. A typical coal train has maybe 1 hp/trailing ton on the level. A BNSF transcon intermodal train may have 3-5 hp/trailing ton. BN/ATSF have experimented before, and I suspect this will not be the end of new ideas.
Jim
Modeling BNSF and Milwaukee Road in SW Wisconsin
jrbernierIn the case of what BNSF wants to do, it makes sense on paper.
jrbernier Timz, Weight on Drivers is not how to measure 'Continuous TE' - Weight on drivers will give you a ball park figure for starting(breaking friction). Remember, there are 6 traction motors sucking up all of the juice. If you only have 4 traction motors, the output will be split only 4 ways. In theory, I suspect you could only have a single large traction motor(if you could fit it). When I worked for a railroad, we normally assigned 1.5 hp/trailing ton on our merchandise trains. 3 GP40's pulling 6,000 tons or 3 SD45's pulling 6,000 tons made little difference(other than the SD45's rode a lot better). Since we were running at 60 mph, the 750 hp/axle GP40's actually pulled better than the 600 hp/axle SD45's. The SD45's had the advantage of more 'dig' when starting a train. But with that much hp, the GP40's could move a train out of the yard just fine. In the case of what BNSF wants to do, it makes sense on paper. To hedge their bets, it is being done to only 25 engines and I suspect they will be able to convert them to standard GEVO's if the experiment does not work out. Now, your example of running a heavy coal train up a mountian grade is just not what BNSF wants to do. A typical coal train has maybe 1 hp/trailing ton on the level. A BNSF transcon intermodal train may have 3-5 hp/trailing ton. BN/ATSF have experimented before, and I suspect this will not be the end of new ideas. Jim
Sounds like Jim is pretty much saying what I originally replied to you on the other A1A thread. Jim strikes me as a guy who knows what he's talking about, so I'm not sure I get what your disagreement with me is about?
nody
I have seen some informed speculation on other forums that the ES44AC-4s will have about the same per unit cost as the ES44DC units BNSF previously bought for the same type of service..
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nodySounds like Jim is pretty much saying what I originally replied to you on the other A1A thread.
jrbernierSince we were running at 60 mph, the 750 hp/axle GP40's actually pulled better than the 600 hp/axle SD45's.
CSX Rules for powering trains limit the number of powered axles that can be on the head end of the train to 24 axles. When calculating the number of axles, an AC engine of any variety is to be counted as 9.
The load applied to any engine is a function of the territory in which it operates. In some territories an engine may be rated for 2500 tons.....the same engine in another territory may be rated for 20,000 tons. Loading is also a function of how fast one expects the trains to move, the faster you expect to crest a grade the less tonnage that the engine can handle on the grade.
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I would say BNSF's powder river coal basion. With long heavy coal trains grinding out of there with anything from SD70MACS's to today's ES44AC's on the point I'd think that theay would load em' pretty heavy.
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bubbajustinI would say BNSF's powder river coal
We routinely send 12000 ton trains over a 1.3% ish grade with 3 AC's either SD9043MAC;s or C44/45AC's. It is also not uncommon to assign 1 SD70 to a 6000 ton stack train on level track as a single unit. On the UP we assign locomotives to a train based on their total powered axle count which is based on their continuous tractive effort. I.E. any GE AC i sconsitered to have 12.1 powered axles for 121,000 Lbs of tractive effort. This is true for the C44AC's to the C60AC's. I'm not really sure where they get the actual numbers. When we do a drag test a SD9043MAC can drag a GE around by the nose but a GE has real trouble going the opposite way. though the EMD's are rated at 11.6 TPA. not really sure if this answers your questions.
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