My question is why? I read that they are supposted to be used on the Transcon but wouldn't 4 axle engines do the same? And what would the trucks look like?
There are some interesting discusssions going on about this on some other web forums and the best explanation I've read on why BNSF isn't ordering ES44BAC's(BES44AC?)) is that a LOT of money and development time would have to go into creating such a locomotive and it would very likely cost just as much as one of these ES44AC-4s. In addition the hypothetical BB would need to have the same "souped up" cooling system as a 6 axle EVO(for emissions Tier compliance) and shoehorning all of this into a B40 series frame (which IINM is already pretty long for a roadswitcher) would be tricky, although some have speculated about a hypothetical freight version of the "GEVOSIS"(Evolution series, Gevo powered, Monocoque bodied passenger loco GE is trying to market)..
If what I've read is correct BNSF is getting a unit priced about the same as an ES44DC(with similiar train handling capabilities). They will be somewhat lighter than a standard Evolution series(with corresponding reduction in fuel consumption) and have somewhat lower maintenance costs (2 less traction motors and inverters, ect)..I do wonder about cost/performance figures of a lashup of 3 ES44AC-4s versus 2 standard, six motor ES44ACs (or how best to deploy 12 AC powered Axles)?
"I Often Dream of Trains"-From the Album of the Same Name by Robyn Hitchcock
A V-12 engined GEVO would be too heavy for B-B trucks, with any reasonable sized fuel tank. The Dash-8-40BW had to have smaller fuel tanks and rode like a Sherman tank. a GEVO version with a more sophisticated cooling system, and a stronger cab, would be much worse. I don't think the 12-cylinder EVO diesel is much lighter than the 7FDL-16.
We are forgetting one thing about AC traction motors THEY DO NOT have a SHORT TIME RATING. You can load them to full power right out of the gate and if they can grip the rail they will pull. Plus one AC motor is worth 1.5 DC's so in a way BNSF is getting the pulling power of a DC44GEVO anyway but saving the cost of 2 invertors and 2 traction motors worth of Maintance. BTW it was the GP60M that had to have the Smaller fuel tank 3200 gallons instead of 4000 gallons when the wide cab was put on it and rode rougher than a Rubberblocked suspension truck going across Arkansas on I-40 EMPTY that and they could only give them 2900 gallons of fuel in the tank MAX to keep within axle loading.
Mentioning about a 4 alxe engine with a GEVO engine in it, I had saw a GE presentation on the internet and they show on one of the powerpoint slides that they were developing a engine that you could fit into older GE's like the Dash 7's. And I know they tried 4 axle AC motors before so could they do it again?
edbentonWe are forgetting one thing about AC traction motors THEY DO NOT have a SHORT TIME RATING. You can load them to full power right out of the gate and if they can grip the rail they will pull. Plus one AC motor is worth 1.5 DC's so in a way BNSF is getting the pulling power of a DC44GEVO anyway but saving the cost of 2 invertors and 2 traction motors worth of Maintance. BTW it was the GP60M that had to have the Smaller fuel tank 3200 gallons instead of 4000 gallons when the wide cab was put on it and rode rougher than a Rubberblocked suspension truck going across Arkansas on I-40 EMPTY that and they could only give them 2900 gallons of fuel in the tank MAX to keep within axle loading.
My problem with the design is that I question how much trouble the ES44C4 will have producing a factor of adhesion of 42.8%, compared to a ES44DC producing a factor of 28.5%. That is what each locomotive has to achieve to produce 120,000 lbs. of TE, with a locomotive weight of 210 tons. And if an inverter or traction motor goes down on the C4 you stall. And both locomotives are at 70,000 lbs on axle so there isn't much room to lower the need factor of adhesion by raising locomotive weight.
GMS-AUIt will just have more power available for speed
Seems foolish to take away 2 powered axles. Must be forgetting about snow, ice, wet leaves, etc.
Maybe just get ES44ACs, and have the computer cut out the 2 center axles above a certain speed.
At least there should be room to put the center traction motors back in when the experiment fails...
Mike WSOR engineer | HO scale since 1988 | Visit our club www.WCGandyDancers.com
beaulieu A V-12 engined GEVO would be too heavy for B-B trucks, with any reasonable sized fuel tank. The Dash-8-40BW had to have smaller fuel tanks and rode like a Sherman tank. a GEVO version with a more sophisticated cooling system, and a stronger cab, would be much worse. I don't think the 12-cylinder EVO diesel is much lighter than the 7FDL-16.
The above is not strictly true in that GE has designed and is trying to market a 4 axle (and 4 motor)passenger locomotive using the GEVO-12. This is confirmed in a recent book about the Evolutiion series. The "Gevosis" (my own nickname) would use a new Monocoque carbody rather than being built on a roadswitcher frame. However, It still seems putting that machinery and electrical system onto a Dash 8 B size frame might not be practical..
BNSF_GP60M My question is why? I read that they are supposted to be used on the Transcon but wouldn't 4 axle engines do the same?
My question is why? I read that they are supposted to be used on the Transcon but wouldn't 4 axle engines do the same?
It would do exactly what a 4 axle AC or 6 axle DC locomotive would do.
The advantage a four axle would have would be less weight and one less pair of wheels to maintain.
But, you'd have to do some fancy engineering in order to figure out how to shoe-horn in 5000 gallons of fuel and keep the axle loadings down to a managable level. And, BNSF is already set to maintain the new locomotives. They won't need one additional spare part or have any training to do.
The kicker here is GE could sell BNSF an A-1-A for the same price as a 6 axle DC and it will the same job and, being AC, will cost less to maintain. And then can sell them to them right now with almost no risk to BNSF. A good deal for BNSF!
-Don (Random stuff, mostly about trains - what else? http://blerfblog.blogspot.com/)
oltmanndGE could sell BNSF an A-1-A for the same price as a 6 axle DC and it will the same job and, being AC, will cost less to maintain.
An ES44DC costs what-- 20%? 25%? less than a C-C ES44AC? Can an A1A-A1A match that discount by deleting two motors and two inverters?
timz oltmanndGE could sell BNSF an A-1-A for the same price as a 6 axle DC and it will the same job and, being AC, will cost less to maintain. So why does anyone want ES44DCs? An ES44DC costs what-- 20%? 25%? less than a C-C ES44AC? Can an A1A-A1A match that discount by deleting two motors and two inverters?
What locomotive give a better performance EMD or GE?
That's the theory! (apparently, it's practice on BNSF, now)
timz GMS-AUIt will just have more power available for speedCan anyone explain why it should?
Timz,
An A1A (4 motors/4 drive axles & 2 unpowered "coaster" axles) will have more power per axle giving a higher top speed, as does any B-B (two 2 axle trucks with one electric motor per axle = 4 motors) loco over any C-C (two 3 axle...= 6 motors) given the same engine power.
This is because a given diesel prime mover puts out a certain amount of maximum horsepower for which it is rated. For example an SD40-2 is rated at 3000hp max. The ES44AC & DC puts out 4400 hp max (hence the name "44").
At rated horsepower, the generator, which is directly driven off the prime mover, makes its maximum amount of electric current (amps). Just for example, say that it is 1000 amps. 1000 / 4(motors) = 250 amps of torque applied per motor/axle. 1000 / 6 = 167 amps per axle. More torque means more power to push the train faster.
The tradeoff is that if you have a very heavy train or steep grade to climb, and are going slowly or just starting out, getting all that torque to the rail without the drive wheels slipping is difficult or impossible. Having 2 extra axles worth of drive wheels allows you to spread out the work load.
But if the train is lighter, like the intermodals BNSF has these A1A's in mind for, you don't need the extra traction of 6 drive axles with motors. 4 drivers and two "coaster" axles will do the slow work fine and then have that extra torque available as the train speeds up to keep adding more power and hence more speed.
They could just delete the "coaster" axles, but that would require a whole new design, and the whole point of this "experiment" is to save money, not spend more. Also, if the experiment flops, they could reconfigure these locos back to ES44AC standard C-C configuration relatively cheaply.
As far as ES44AC's vs. ES44DC's, I have read that the former cost as much as $1 million more than the latter. Buying cheaper DC locos would seem a logical way for BNSF to go for this job (as NS has always done until recently), but BNSF very well may have a long term vision of getting out of the DC business and it's maintenance problems altogether. AC seems to be the wave of the future, initial cost and weight being it's major drawbacks set against far better reliability, ease of use, and traction.
I'd like to hear what the more experienced feel about this.
nody Timz, An A1A (4 motors/4 drive axles & 2 unpowered "coaster" axles) will have more power per axle giving a higher top speed, as does any B-B (two 2 axle trucks with one electric motor per axle = 4 motors) loco over any C-C (two 3 axle...= 6 motors) given the same engine power.
Ah...The more conventional term for an unpowered axle on a diesel locomotive is "idler" axle, not "coaster" axle.
I stand corrected.
So do we know when these units are supposed to hit the road?
nodytimz GMS-AUIt will just have more power available for speedCan anyone explain why it should? Timz, An A1A (4 motors/4 drive axles & 2 unpowered "coaster" axles) will have more power per axle giving a higher top speed, as does any B-B (two 2 axle trucks with one electric motor per axle = 4 motors) loco over any C-C (two 3 axle...= 6 motors) given the same engine power. This is because a given diesel prime mover puts out a certain amount of maximum horsepower for which it is rated. For example an SD40-2 is rated at 3000hp max. The ES44AC & DC puts out 4400 hp max (hence the name "44"). At rated horsepower, the generator, which is directly driven off the prime mover, makes its maximum amount of electric current (amps). Just for example, say that it is 1000 amps. 1000 / 4(motors) = 250 amps of torque applied per motor/axle. 1000 / 6 = 167 amps per axle. More torque means more power to push the train faster. The tradeoff is that if you have a very heavy train or steep grade to climb, and are going slowly or just starting out, getting all that torque to the rail without the drive wheels slipping is difficult or impossible. Having 2 extra axles worth of drive wheels allows you to spread out the work load. But if the train is lighter, like the intermodals BNSF has these A1A's in mind for, you don't need the extra traction of 6 drive axles with motors. 4 drivers and two "coaster" axles will do the slow work fine and then have that extra torque available as the train speeds up to keep adding more power and hence more speed. They could just delete the "coaster" axles, but that would require a whole new design, and the whole point of this "experiment" is to save money, not spend more. Also, if the experiment flops, they could reconfigure these locos back to ES44AC standard C-C configuration relatively cheaply. As far as ES44AC's vs. ES44DC's, I have read that the former cost as much as $1 million more than the latter. Buying cheaper DC locos would seem a logical way for BNSF to go for this job (as NS has always done until recently), but BNSF very well may have a long term vision of getting out of the DC business and it's maintenance problems altogether. AC seems to be the wave of the future, initial cost and weight being it's major drawbacks set against far better reliability, ease of use, and traction. I'd like to hear what the more experienced feel about this.
Power = Force * velocity
The faster a train is intended to move, the more power it has to have for a slower moving train of the same weight. Or, a light, fast train may need the same power as a slow, heavy train. Let us compare two theoretical trains running on the same route. One is a slow moving manifest, the other is a light, fast intermodal. Assume that the manifest weighs 1.5 times the intermodal.
Pm=Fm*Vm; Pi=Fi*Vi
If the consists for both trains have the same amount of power, Pm=Pi. Since the manifest weighs more, it will take more force to move it. This means that the locomotives on the manifest must have a higher frictional force than the locomotives on the intermodal. This can be achieved by heavier locomotives, more locomotives, or a high coefficients of friction.
Because the locomotives on the intermodal do not have to use as much force to move the train, they can put more of their power into higher speeds. Since Pm=Pi, then Fm*Vm=Fi*Vi. Fm=1.5Fi. Now, 1.5Fi*Vm=Fi*Vi, or Vi=1.5Vm. This allows the lighter train to go faster with the same power as the heavier train. This has nothing to do with axles.
The reason why SP/SSW and ATSF bought four axle locomotives for intermodal trains is that in the above example, the locomotives on the intermodal need to have 2/3 the frictional force between the locomotives and the rails as the locomotives on the manifest. Why waste locomotive weight and extra components that are not needed? You can put 4 six axle locomotives on the manifest and 4 four axle locomotives of the same HP on the intermodal. There are less components (things that will break) on the four axle locomotives, and the railroad is not paying to haul the extra weight around. So, they bought four axle locomotives.
I have been told the reason why all road locomotives are now six axles is so that they do not have the headache of two road fleets, the horrible ride of the high horsepower four axle locomotives, and because the weight was getting to be too much for four axles.
Apparently, BNSF has decided the two fleet penalty is worth the better performance. Others have commented about re-engineering the locomotives and the weight issues, which is probably the reason why BNSF is buying A1A-A1A instead of B-B.
"No soup for you!" - Yev Kassem (from Seinfeld)
It all comes down to this:
Given the HP/ton you need to keep your commercial schedules, How slow will you go up the ruling grade on the route?
First, find the minimum continuous full HP speed for each locomotive type you're considering based on the max of adhesion, traction motor thermal limit, or generator current output. (Typically, for AC locomotives, it will be adhesion based and for DC units it will be TM themal limit)
Let's say for the AC unit you are considering, it's 8 mph for the 6 axle version and 12 mph for the A1A-A1A version. For the DC 6 axle unit your are considering, it's also 12 mph.
If the calculated balance speed on the ruling grade is above 12 mph, you don't need to waste your money on the six axle AC locomotive. The A1A version (or the 6 axle DC) will work just fine.
(to find the approx. balance speed, just use 20#/ton/%grade for train resistance and power = force x speed)
My thoughts on why this is hapeening is as follows; GE is offering this locomotive as a replacement for DC motored six-axle locomotives to overcome the higher first cost of the six-axle AC motored locomotive, if they can increase production of the AC motors and inverters enough it will lower the per unit cost enough that the railroads will just purchase the standard AC motored six-axle and the A1A version will have just been a transitional unit to ease the conversion to a full AC motored fleet.
beaulieu My thoughts on why this is hapeening is as follows; GE is offering this locomotive as a replacement for DC motored six-axle locomotives to overcome the higher first cost of the six-axle AC motored locomotive, if they can increase production of the AC motors and inverters enough it will lower the per unit cost enough that the railroads will just purchase the standard AC motored six-axle and the A1A version will have just been a transitional unit to ease the conversion to a full AC motored fleet.
It does seem to me, though, like this was a customer (BNSF) driven development. GE had no mention of this in earlier marketing material for the Evolution series...I can't see them exiting the DC traction market altogether, there are a number of applications where it is desirable...
What I heard around here - about 6 months ago - was that this was a GE initiative. If they can sell it, they can pull their DC six axle from the catalog. Makes the whole production process simpler and cheaper. They'd really be building only one locomotive model in two variations.
On the "selling it" side, about 1/3 the overall cost of maintaining a DC locomotive is the traction motors. If the inverter + AC motor is much more reliable, there's quite a bit of annual savings to offset a modest increase in purchase price. I'm sure GE came well armed when they pitched it to BNSF. I'm sure they've pitched it to all the roads.
The only risk I can think of is that the A1A unit will have higher avg current thru each inverter - will that effect their life or cause failures?
Don, you've made four posts on this subject; you've said basically the same thing each time; and everything that you've said seems reasonable to me.
JayPotter Don, you've made four posts on this subject; you've said basically the same thing each time; and everything that you've said seems reasonable to me.
That's because I like repeating myself, by saying the same thing over a few of times and then repeating myself.
Does this mean traction motors with 1200 HP each for the A-1-A vs motors with 750 HP?? Also will they build larger inverters so each motor is powered by a separate inverter as is now done???? . Any one have the specs of the various AC motors that are used on all AC locomotives? I know they go at least up to 2000HP for the AMTRAK electrics.
nodyAn A1A (4 motors/4 drive axles & 2 unpowered "coaster" axles) will have more power per axle giving a higher top speed, as does any B-B (two 2 axle trucks with one electric motor per axle = 4 motors) loco over any C-C (two 3 axle...= 6 motors) given the same engine power.
nodyJust for example, say that it is 1000 amps. 1000 / 4(motors) = 250 amps of torque applied per motor/axle. 1000 / 6 = 167 amps per axle. More torque means more power to push the train faster.
I remember GE telling me that their inverters were good for 1000HP each. That was back in 1993. 4400 HP over 4 motors would be 1100HP/motor, so I guess they've found an extra 10% somewhere over the past 15 years. Doesn't sound unreasonable to me...
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