For those who are interested, there are two videos on Youtube showing the first two ES44AC-4, #6600 and 6601 testing along the NS line. And 6601 looks like its already had some problems.
http://www.youtube.com/watch?v=2iJD1LkBi3w
http://www.youtube.com/watch?v=oCc9eCpj--A
The difference in pulling power at higher speeds between a C+C and an A-1-A+A-1-A is the small added resistance of the gear trains and motors on two axles. As with your garden hose analogy, the flow resistance of the hose wall is greater with multiple hoses.
Maybe the rate of starting acceleration will be slightly slower overall with A-1-A; but this is insignificant with sustained speeds above 30 mph - even accelerating back to 70 mph after slowing for a 50 mph crossover. The value of the saved time must not be worth the extra cost of two motors over the life of the unit.
timz Randy StahlAt 70 MPH Both engines are putting out thier rated HP .. The A1A engine just got there first. We're agreed the C-C pulls the same as the A1A-A1A at 70 mph... and at 60 mph? And at 50, and 40, and 30?
Randy StahlAt 70 MPH Both engines are putting out thier rated HP .. The A1A engine just got there first.
agreed
After I posted the above, I recalled thinking about whether a 1-A-A+A-A-1 arrangement would serve to clean water, snow, and ice from the rail with the idle axle to improve adhesion for the powered axles? Would this pose a tracking problem with the truck? Some streetcars had a single powered axle on a truck; but they didn't go 60 mph.
An AC A-1-A locomotive with 70,000 lbs/axle and 117,000 lbs starting tractive effort at 42% adhesion has only 22,600 lbs tractive effort at 60 mph with 4,400 hp. The old formula for diesel-electric tractive effort was Hpx308/Mph as limited by adhesion. Meanwhile, drag from air resistance increases exponentially with speed in addition to journal (roller bearing) and track rolling resistances.
Crosswinds increase flange resistance. I remember seeing a C&NW train die exposed to 40 mph crosswinds on the Illinois prairie winter-bare fields and wait for additional power.
Just because you can start a train doesn't mean it can make track speed; and that is part of the reason why BNSF may be going for the less expensive A-1-A model. The heaviest train that could be started with a single unit may take six or seven locomotives to attain 60 mph with increasing train resistance. The train's weight will not pose a problem in starting with power for 60 mph, so there is no danger of stalling from slipping, only the avoidable wheel and rail damage.
timz WSOR 3801timzAt 70 mph you figure the A1A-A1A is still putting out 3800 rail horsepower but the C-C isn't? Why shouldn't it be? Transmission losses, and splitting the power 6 ways instead of 4.Why would that make the C-C less powerful than the A1A-A1A? If it were less powerful at 70 mph, then by that reasoning wouldn't it be less powerful at any speed over 20 mph?
WSOR 3801timzAt 70 mph you figure the A1A-A1A is still putting out 3800 rail horsepower but the C-C isn't? Why shouldn't it be? Transmission losses, and splitting the power 6 ways instead of 4.
timzAt 70 mph you figure the A1A-A1A is still putting out 3800 rail horsepower but the C-C isn't? Why shouldn't it be?
I'm just joing in on this thread, but I thinhk that the C-C version would have more rolling drag after a certian speed. The power is being diverted over more axels so that = more weight. The unit wouldn't have as mutch pull over a certian speed because it's still pulling itself along to. It seems that the A-1-A has less space to apply the power over so the power would = more effort to the rail. That's the way I see it.
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timz Randy StahlA C-C with 2 motors disconnected, or an A1A-A1A will accelerate fasterWill the C-C accelerate even faster if we disconnect four motors?Randy StahlAt the top end of the VOLTAGE curve the A1A-A1A should exert identical effort as the C-C. Randy Stahlthe A1A will pull harder at higher speeds as the speed increases Identical effort, but pulls harder... Let's try this: say the C-C ES44 is good for 3800 rail horsepower at 30 mph. The A1A-A1A would be about the same-- right? At 70 mph you figure the A1A-A1A is still putting out 3800 rail horsepower but the C-C isn't? Why shouldn't it be?
Randy StahlA C-C with 2 motors disconnected, or an A1A-A1A will accelerate faster
Randy StahlAt the top end of the VOLTAGE curve the A1A-A1A should exert identical effort as the C-C.
Randy Stahlthe A1A will pull harder at higher speeds as the speed increases
Let's try this: say the C-C ES44 is good for 3800 rail horsepower at 30 mph. The A1A-A1A would be about the same-- right? At 70 mph you figure the A1A-A1A is still putting out 3800 rail horsepower but the C-C isn't? Why shouldn't it be?
At 70 MPH Both engines are putting out thier rated HP .. The A1A engine just got there first.
I have experimented with motor cutouts on the AC4400 s , I discovered that if you cut out different combinations of motors the locomotive will have different characteristics. If you cutout two motors on one truck the engine will derate to prevent wheel slip. Cut them out on different trucks and it will behave differently. Three motors in any combination will derate the engine. I have cut out 5 motors on a AC4400 and observed the wheel spinning, it did slowly move though..There comes a point when adhesion is so bad that the engines will derate.
timzRandy StahlA C-C with 2 motors disconnected, or an A1A-A1A will accelerate fasterWill the C-C accelerate even faster if we disconnect four motors?
The two motors will accelerate faster. The rest of the engine (and the train) probably won't.
timzLet's try this: say the C-C ES44 is good for 3800 rail horsepower at 30 mph. The A1A-A1A would be about the same-- right? At 70 mph you figure the A1A-A1A is still putting out 3800 rail horsepower but the C-C isn't? Why shouldn't it be?
Transmission losses, and splitting the power 6 ways instead of 4.
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A C-C with 2 motors disconnected, or an A1A-A1A will accelerate faster, the C-C has the avantage over the A1A-A1A at lower speeds. At the top end of the VOLTAGE curve the A1A-A1A should exert identical effort as the C-C. Starting TE is higher when there's more driving wheels contacting the rail , the C-C is the higher .
The A1A A1A cannot be placed on the same trains as the C-C engines as they will have difficulty starting the train . Once the train is moving above 10-12 mph the A1A will begin to show its stuff.
To summarize , the C-C has the advantage starting trains and slowly accelerating to 10-12 mph. the A1A will pull harder at higher speeds as the speed increases and the voltage curve rises . In addition with less motor load on the Diesel the LR will not regulate as soon as it would on a 6 motor engine.
Randy StahlFewer motors on a constant KW system equals faster acceleration does it not using you example?
I think you suggested a C-C with two motors disconnected would load faster than the stock C-C, but you never said it would sustain a harder pull at any speed-- right? So when accelerating a train it might reach its lower tractive effort ceiling quicker than the C-C, but 30 seconds after starting the C-C would be at least matching the A1A-A1A's TE and would never be at a disadvantage thereafter?
Those numbers sound pretty close . My point is that your not going to put that slug set on your fastest trains , the ones with the highest HP per ton . Fewer motors on a constant KW system equals faster acceleration does it not using you example?
AC locomotives are still effectively constant kilowatt machines. The Phase modules are parellel with the DC link.
On many slug sets , the slug booster drops out at around 10-12 mph , I know the ones we had on CN did. We used them with GP-38s.
Okay, GP40 running light compared to GP40-plus-slug running light, acceleration 0-70 mph on the level or upgrade-- GP40 without slug will win.
GP40 with 2500 trailing tons on 1% upgrade will likely level off at 0 mph; with the slug and the same train it will do something better than that-- maybe 12 mph?
You tell me , I gave you your power (locomotive) , you tell me how its going to get used . You have a GP-40 slug set , how are you going to use it?
Look at things form my perspective you have a fleet 315 cummins with a 3.33 rear and a 9 speed tranny set for 65 MPH max yes it will get the load there however it will tuck its tail between its legs at every hill it hits. Now you take a 600 HP cat give it a 18 speed and a set of 3.73 rears it will climb like a scalded dog and pull like a clysdale. This is what the BNSF is going for with the 4 motored AC unit I think going for both. Remember this that there are reports of AC units breaking the Pinion shafts yet it took til the next service before they found it because the TM did not come apart since there are no windings that came apart.
Randy StahlFast or slow ?
Just figured it out, it would still be 3000hp. Probably not a speedster with the power over 8 axles.
Too much thinking for me right now, just got off work, but i do know that intermodal trains supposedly used four motor power because they could get up to speed faster. I guess with the horsepower ratings these days its less of an issue, but I recall original GP40s apparently had trouble with the higher hp per axle.
On the flip side, units such as the SD7 and thru the SD38s has a relatively low horsepower rating per axle, and were better at low speed lugging than actually trying to make time on the road. This is why you see them on mining roads and such. Somebody like Randy would certainly be better informed on this than I am, but I have read a lot and it seems to make sense.
A conventional C-C locomotive has the ability to disconnect 2 traction motors. Called traction motor cutouts. Maximum HP on conventional DC engines is reduced on account of overloading the 4 remaining motors. I have experimented with SD-40 and C-30s overriding the parellel resisitors in the feedback panel (PF module) and the acceleration was much faster. It would be possible to overload the remaining 4 motors, not to mention the wheels had a tendency to spin, when they do spin there is a danger of destroying the motor.
On AC engines there is NO reduction on maximum HP . 4400 horsepower period, regardless of the number of traction motors.
Quick quiz: Mother slug combo .. GP-40 Mother , D-78 TMs. 4 axle slug D-78 TMs . Whats the horsepower of this setup? Fast or slow ??
Randy StahlFaster throttle response and faster loading. Less LR activity = higher speeds.
Ok, so it's still got 3 axels per truck but one of them is unpowered.
bubbajustin Forgive me, what does A1A version of a locomotive mean? So what ever that is there putting a GEVO engine in it hugh?
Forgive me, what does A1A version of a locomotive mean? So what ever that is there putting a GEVO engine in it hugh?
A1A translates to a three-axle truck, traction motors on the outside axles, center axle is unpowered.
1/3 less motor load and the EGU will have less activity on the LR . The load regulator will balance much later. Faster throttle response and faster loading. Less LR activity = higher speeds.
If we disconnect one motor on each truck of a conventional C-C and run it as an A1A-A1A, will it reach its top speed any faster than it did before? If so, why?
timz Randy StahlTop speed should be about the same but they will get there a little faster. Apparently this is one of those notions that will never, ever die out.
Randy StahlTop speed should be about the same but they will get there a little faster.
Well , I only have 23 years on locomotives in mechanical departments , perhaps you can enlighten me .
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