Randy StahlTop speed should be about the same but they will get there a little faster.
With 1/3 less motor load these guys should be some hot rods ! I'm certain that they do have limits so as not to overload the 4 remaining motors. Top speed should be about the same but they will get there a little faster.
They should ride a hair better. Less unsprung weight. The E units rode well because they had swing hanger trucks which gave a very cushy lateral ride. Frt locomotives are sprung to maximize adhesion, at the expense of ride quality, to some degree.
If I were BNSF, I would still insist on a ride quality test prior to accepting the first unit, just to make sure that theory translates into practice!
-Don (Random stuff, mostly about trains - what else? http://blerfblog.blogspot.com/)
timz nodyI've just finished reading AA Krug's website explaining the relationships between TE, HP, etc,A good plan-- I've never seen a better explanation online. What part of it baffled you? By the way-- tell us about the AA 707 pic (or 720 or whatever it is).
nodyI've just finished reading AA Krug's website explaining the relationships between TE, HP, etc,
By the way-- tell us about the AA 707 pic (or 720 or whatever it is).
Krug was not baffling; it's just keeping the formulas straight in my head, when never having used any of this info practically. If I sat down with a pad of paper and a pencil and ran through a half dozen exercises, it would probably stick a little better. Then without using it again it would be fuzzy in a few days. Some people are blessed with easy comprehension; I've always had to work for mine.
The avatar is a 707-123. I down loaded the photo off airliners.net, (search 707-100 at LAX airport if you want to look at the original) so you can have me arrested for copyright violation I guess. .
This is the first generation U.S. jet airliner. The Pratt & Whitney JT3 turboJETs (not the later turboFANS) were the civilian version of the P&W J57, found on the original B52's, KC135's, as well as Century Series fighters F100, F102, etc.
It is the volumous black smoke, similar to a Big Boy in full grunt, that makes the picture so entertaining and interesting; especially to train buffs who might like such things, I thought, which is why I used it.
Ironically, like a Big Boy, this airplane too was "steam powered" in a manner of speaking. Early jet engine metallurgy only permitted maximum operating temperatures of about 400 deg C (verses 900+ in today's engines). During takeoff, distilled water would be injected into the "hot section" of the 4 engines, both cooling the turbine blades and increasing the mass outflow out the tail pipe, thus increasing thrust (and smoke!)
I often wonder if we could still breath if we hadn't cleaned up our "planes, trains, and automobiles"?
I have a question. Sounds good in principle but I wonder how the riding qualities will be. Only actual use will demostrate how they ride. E - units were famous for their riding qualities. The larger AC motors on the two outside axels and none in the middle is a "very interesting" question as used to be said on the laugh in program.
carnej1 It does seem like the ES44AC-4s might be a good solution for the type of fast freight, trancontinental service that BNSF is purchasing them for. But I would think as far as supplanting the ES44DC in GE's catalog I doubt that all current DC Evolution operators would be satisfied. Particularly what about NS? They seem to be going toward AC units for Coal service but their preferred power for most other line haul applications is the ES40DC and I don't know that an A-1-A unit(even with the AC motors)would be an acceptable substitute...
It does seem like the ES44AC-4s might be a good solution for the type of fast freight, trancontinental service that BNSF is purchasing them for. But I would think as far as supplanting the ES44DC in GE's catalog I doubt that all current DC Evolution operators would be satisfied. Particularly what about NS? They seem to be going toward AC units for Coal service but their preferred power for most other line haul applications is the ES40DC and I don't know that an A-1-A unit(even with the AC motors)would be an acceptable substitute...
For NS as for all the others it comes back to ROI. If GE could sell the ES44AC for say $100k more than the ES44DC. The ES44DC would be deader than a Dodo. At this point GE can't do that, it is more like $700k.
"I Often Dream of Trains"-From the Album of the Same Name by Robyn Hitchcock
Let's see if we can get this discussion back on a better footing.
Most likely GE went to BNSF with a proposal to eliminate the DC motored six-axle fleet from future purchases. GE would have made a presentation with facts and figures showing that these ES44C4 locomotives could do the job that a ES44DC could do, and BNSF Mechanical Department people looked at the numbers and found them plausible, and there must be a future ROI benefit if it works out, most likely fewer types of parts needed to be stocked. It is agreed that 25 locomotives will conduct the test, most likely if the test fails the locomotives can be converted to standard ES44ACs. Perhaps the extra wiring needed will be installed but not connected, so only inverters and traction motors need to be installed, and software changed. Another thought is with the increase in number of AC motored locomotives sold, the cost may come down enough that the real result will be an ES44AC fleet without the A1A variant, at a price similar to the current ES44DC.
One question I have is about the difference in Back EMF in these 4-motored AC locomotives versus a 6-motored DC locomotive, at a given power level and a speed above the minimum continuous speed. Would the Back EMF from the 4 AC motors against the Traction Alternator be lower than that produced by the 6 DC motors. Also might the electrical transition be simpler. Can somebody refresh my memory on the effects of parallel circuitry and the relationship of Volts and Amps. I know Ohm's Law, what I am wondering about is the effect of 4 circuits in parallel versus 6 circuits.
ericsp Oltmannd, when I wrote about the extra weight, I was referring to four axle versus six axle locomotives (i.e. GP40-2 versus SD40-2). Unless you are reply to, "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." There I was referring to where it has been stated that locomotives are getting too heavy for four axles.
Oltmannd, when I wrote about the extra weight, I was referring to four axle versus six axle locomotives (i.e. GP40-2 versus SD40-2). Unless you are reply to, "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." There I was referring to where it has been stated that locomotives are getting too heavy for four axles.
I agree! Sorry for the confusion...
nodytimz 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.So it will pull even better if the locomotive has one traction motor on each truck? And better still with one traction motor per locomotive? Theoretically yes, but the rub would be that you'd need a much bigger motor and inverter to take the full output of the gererator all by itself, and then you'd have to be able to apply all that torque to one set of wheels, which in reality would be spinning on the rails as if they were greased. Where your idea would work is if the train were already going fast, so wheel slippage wouldn't be an issue, but then another loco would have to get it rolling first...kinda defeats the purpose. Of course tradoffs have to be made. As the guys above have stated, it is figured out mathematically how much traction and power are needed for a given job. They don't just start attaching locos to the front of a train (or middle or rear) til they run out of spare power. And it stands to reason that a 7000 ton unit going through mountains will need more power and traction than Amtrak from Baltimore to Orlando, yet Amtrak will be a much faster train. Notice that the fast passeger (read light weight) locos are B-B.
timz 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.So it will pull even better if the locomotive has one traction motor on each truck? And better still with one traction motor per locomotive?
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.
Theoretically yes, but the rub would be that you'd need a much bigger motor and inverter to take the full output of the gererator all by itself, and then you'd have to be able to apply all that torque to one set of wheels, which in reality would be spinning on the rails as if they were greased.
Where your idea would work is if the train were already going fast, so wheel slippage wouldn't be an issue, but then another loco would have to get it rolling first...kinda defeats the purpose. Of course tradoffs have to be made.
As the guys above have stated, it is figured out mathematically how much traction and power are needed for a given job. They don't just start attaching locos to the front of a train (or middle or rear) til they run out of spare power.
And it stands to reason that a 7000 ton unit going through mountains will need more power and traction than Amtrak from Baltimore to Orlando, yet Amtrak will be a much faster train.
Notice that the fast passeger (read light weight) locos are B-B.
No, it would not. Fewer axles does NOT allow a locomotive to run faster.
Bold added by me.
"No soup for you!" - Yev Kassem (from Seinfeld)
Timz
Well then you have succeeded as I have indeed repeatedly tried to think through and explain what I've read about, but of course have no practical experience in. The concept I put forth is my paraphrasing of what I have read and what appears to be logical to me, but I may in fact be wrong. Or perhaps the concept is right but I explained it inadequately.
One really doesn't know a subject until one can clearly explain it to a layman, one devoid an assumed base of knowledge. Then again, a layman can only understand the surface of a subject without his own deeper study.
Obviously I and a lot of others are not quite there yet. Then of course when non-physicists try to discuss physics on a practical application level, they are really just discussing the "shadow" the physics cast, so to speak.
I've just finished reading AA Krug's website explaining the relationships between TE, HP, etc, among other subjects, and while fascinating and well written for the layman such as myself, it is the kind of stuff that even for an educated guy I find hard to hold onto. One moment you think you understand what he is saying and the next you don't. And back and forth you go.
nodyYour endless questions smack of baiting.
nodyIf you're a bonfide RR professional, then ...
timz timzSo it will pull even better if the locomotive has one traction motor on each truck? And better still with one traction motor per locomotive?nodyTheoretically yes, but... You think an ES44 with one big traction motor will "theoretically" outpull a conventional C-C ES44 at, say, 60 mph? Do you think the conventional ES44 is good for 3700-3800 rail horsepower at 60 mph? And a one-motor unit would do... how much better than that?nodyNotice that the fast passeger (read light weight) locos are B-B.And they would pull better at their top speeds if they cut out three motors?
timzSo it will pull even better if the locomotive has one traction motor on each truck? And better still with one traction motor per locomotive?
nodyTheoretically yes, but...
nodyNotice that the fast passeger (read light weight) locos are B-B.
Timz,
I only replied to your first question becasue no one else did and I though you couldn't make sense of what that previous poster implied.
Now I get the feeling you are trying to show us all how dumb we are, and how smart you are. Your endless questions smack of baiting. Maybe I'm misunderstanding you?
If you're a bonfide RR professional, then we'll all happily defer to your knowledge and thank you for sharing it with us. As for the rest of us, well we're just "foamers" and in my case a "junior foamer."
ericsp nody 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. 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.
nody 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.
timz GMS-AUIt will just have more power available for speedCan anyone explain why it should?
GMS-AUIt will just have more power available for speed
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.
The losses from carrying around a couple motor's extra mass along with their frictional forces are really miniscule compared to the overall work performed. There's no other difference!
These are for Merchandise and Intermodal trains,not unit trains. BNSF segregates their fleet that way.
Rodney if you read the orginal post these 25 are going to be restricted to INTERMODAL units because they are going to be missing 2 TM's therefore would not have th TE of a normal GEVOAC44 and could not handle the coal trains. Look for a 200 noumber or somthing to let the power desk plus a note in the computers NOT TO PUT THEM ON A COAL TRAIN.
Hears the thing about es44ac's they are and will be used more in coal service a a1a truck would be slipery as oposed to the standard 6 axle engine, with the 6 axle engine I get 9 rated power axles if 2 traction motors are gone I would have 5 rated power axles yes the cost of 2 traction motors are gone but it is not cost effective for the tractive effort.
Rodney
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...
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.
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.
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.
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?
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.
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...
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)
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