SD90AC

[Anonymous]

What's up with this locomotive? Why is there so little information about it on the internet, and how come SD70ACe got all the credit for its new looks when it's almost identical to the older SD90AC?

[Anonymous]

oops I didn't realize it's another name for SD90MAC-H


but still the second question still stands: the design of ACe is nothing new, how come everybody is talking about Ace as if it is a new design, is it because MAC-H is less known in railfan circles?

[chad thomas]

I assume you mean SD90MAC. The 90 macs were delivered with 4300hp 2 stroke (710 I think) prime movers and were made to have the 710 changed out and the new 6000hp 4 strokes put in when they were ready. I don't think they were tier2 emmisions compliant and probably are no longer available (at least here). They also were not that successfull as I belive they have a lot of vibration related problems. I think UP and CP
were the only roads to buy them.
The SD70ACe is tier2 compliant successor of the SD70Ms, the modern day SD40-2.

[chad thomas]

I might add that when the tier2 emission laws went into effect, the non compliant models were droped from the cataloges and are no longer available.

[Anonymous]

not the regular sd90mac, that one had a more tradition 90's design, SD90MAC-H and sd90MAC-H 2, these looked like modern ACe

[chad thomas]

Well, you probably don't hear much about them cause they didn't make that many. I didn't realize the similaritys till you brought it up. I just don't see any CP units here in southern California.

[Anonymous]

Actually UP used these more than CP did. I think CP only had few while UP had the rest of them (up to about 40-something were made total)



It is even possible that you saw UP versions but thought you were seeing ACe's, I sure would confuse them

[chad thomas]

My info shows UP had 64 SD90MACs. I don't know how many CP bought.

The problem with these units is there is too much horsepower to put to the rail at lower speeds making them ill suited to heavy drag service. They are good for high speed intermodial service though and they can do 80mph where most other models trip the overspeed around 73-74mph. They were the model of choice on the ultra hot UPS trains when they were running.

[chad thomas]

Check out this excerpt from Al Krugs website:

Those Superpower units.
If you haven't been paying attention you might think that the new 6000 HP single unit locos are destined for heavy haul service. True they are all heavy 6 axle units. But that is because the weight is needed to put that 6,000 HP to the rail without slipping. A 6,000 Hp unit that weighs 420,000 lbs and can attain a 43% adhesion factor has an adhesion of 180,600 lbs. The 6,000 Hp diesel engine can deliver that 180,600 lbs of Tractive Effort at a speed of 13 mph. Below that speed you cannot use full throttle on these locos because they will slip. That was for an astounding adhesion factor of 43%. What if they cannot maintain that extreme level of adhesion? What if they "only" get 36%? 36% of 420,000 lbs is 151,200 lbs of TE. The 6000 hp diesel can deliver that TE at 15 mph so the loco cannot operate below 15 mph in full throttle without slipping. At an adhesion factor of 30% the lowest full throttle speed is 18 mph. If the rail is wet or frosty can these modern marvels maintain even a 30% adhesion factor? My experience with 4400 Hp units is a definite no. The C44s often have trouble maintaining 22% adhesion with bad rail conditions. If a 6,000 Hp unit gets down to 22% adhesion it can only operate at full throttle above 24 mph! Thus if you want these behemoths to reliably move your trains over the hills in all kinds of weather you had better dispatch them with trains light enough that they can maintain 24 mph or greater on your steepest hills. That means they are only useful for trains such as intermodals which get a high Hp to tonnage ratio. When it is frosty they won't work on heavy freights or coal or grain trains which routinely pull up the hills at 10-12mph.

The railroad I work for uses 12,000 Hp on their coal trains through here and we go up the hills at about 12-13 mph. Note that you can replace the 12,000 Hp of 3 SD70MACs, or the 12,000 Hp of 4 SD40-2s, with the 12,000 Hp of just two SD90s. You have the same Hp so you should go up the hills at the same 12-13 mph. But it will be awfully iffy. That is because the minimum speed these 6,000 Hp units can operate at full throttle is 13 mph even with an adhesion factor of 43%. If anything causes the train speed to fall below 13 mph even momentarily, you will never regain the lost speed. The train might be temporarily slowed for various reasons. Perhaps the SD90s temporarily lost that 43% adhesion factor and slipped or reduced Hp to prevent slipping. Perhaps a wind came up and increased train restance. At 12 mph the 6,000 Hp locos cannot operate in full throttle even if they regain that 43% factor of adhesion. They will slip. Operating at reduced throttle the locos are not producing the 12,000 Hp this train needs to travel up the hill at 13 mph. So the train will never accelerate back up to 13 mph where it could again operate at full throttle. Four SD40s or 3 SD70MACs would have no difficulty re-accellerating the train back up to 13 mph. That is because they are not operating at the limit of their adhesion as the SD90s are. The 4 SD40s have 12,000 Hp just like the two SD90s but the SD40s have a total weight of 1,680,000 lbs and even at a 30% factor of adhesion can operate in full throttle down to 9mph! The 3 SD70MACs weigh 1,260,000 lbs and with only a 30% factor adhesion they can operate at full throttle down to 11.9 mph. If they achieve a 36% factor of adhesion they can operate at full throttle down to 9.9 mph. So either the SD40s or the SD70s have enough reserve adhesion they can operate at full throttle after being temporarily slowed. That allows them to accellerate the train back up to the 13 mph.

Thus on an equal total Hp basis these high Hp units are not equal to their lower Hp cousins when used in heavy haul service. And heaven help you (more like helpers help you) if the factor of adhesion on these brutes ever falls below 36% because you won't have enough adhesion to pull that 15,000 ton train up that 1% grade, period. You had better hope that it does not rain, frost, or snow.

Keep the high Hp units in high speed freight service where they do the most good. You are trading 8 axles of weight on two 3000 HP GP40s or 12 axles of weight on two SD40s for the 6 axles of the new units and you have 25-50% less Hp-wasting weight with the two high Hp units. Remember that TE decreases as speed increases, so as long as they keep the Hp per ton ratio of the trains high enough to maintain high speeds then the TE will be low enough that these high Hp single units won't slip. But try to use them in low speed drag service and they will slip as noted in the coal train discussion above. The slower the train goes up a hill the closer these high powered 6,000 Hp wonders perform like the good old 3,000 Hp SD40.

[icmr]

The 4,300hp engine is a SD9043mac. The SD70ace also looks like the SD80MAC!!!!



ICMR

Happy Railroading.[swg][swg]

[Anonymous]

QUOTE: Originally posted by chad thomas

My info shows UP had 64 SD90MACs. I don't know how many CP bought.

The problem with these units is there is too much horsepower to put to the rail at lower speeds making them ill suited to heavy drag service. They are good for high speed intermodial service though and they can do 80mph where most other models trip the overspeed around 73-74mph. They were the model of choice on the ultra hot UPS trains when they were running.

you are right, I've checked, UP had 64 MAC-H's and CP had 4 of them. 68 were made in total.

[Anonymous]

By the way, I've heard a rumour that EMD is planing to make a big brother to SD70ACe and call it SD90ACe with some 6300hp? Is that true?


edit: here is where I got that rumour:

"Following the 70 series will be the 90 series SD90ACe which uses the 6,304 HP V16265H
twin turbo engine and the secretive SD89AC which uses a 4,580 HP V12265H"

Quote from a google search result, can't open the page because the site is down, can't even open the catched version.

[chad thomas]

Interesting info electro. I wonder when they will break into the 3 digit designator, SD100MAC or SD100ACe or something like that.

[Anonymous]

QUOTE: Originally posted by chad thomas

Interesting info electro. I wonder when they will break into the 3 digit designator, SD100MAC or SD100ACe or something like that.

Well it could be just misinformation, but then it could be something from some press conference that only the author of the text bothered to report.

[chad thomas]

I'm not knocking your info. It sounds quite plausable to me.

[trainboyH16-44]

QUOTE: Originally posted by electro-ortcele

Actually UP used these more than CP did. I think CP only had few while UP had the rest of them (up to about 40-something were made total)



It is even possible that you saw UP versions but thought you were seeing ACe's, I sure would confuse them

CP had 4.
TRainboy

[Anonymous]

QUOTE: Originally posted by chad thomas

I'm not knocking your info. It sounds quite plausable to me.

I know you are not, I'm the one who is a bit skeptical due to lack of information anywhere else.

[videomaker]

Great pic trainboy,we only see these locos on thru coal and container trains in Tx,so they're far and few between..I havent seen the Katy heritage unit here yet ! Its only been here once since it was put in service..Katy was a major player in Tx before the merger too..Most all UP traffic where I live is directional running and at night. Until they increase the amount of traffic I dont get to see too many trains,I have to work ! Videomaker

[Anonymous]

QUOTE: Originally posted by videomaker

Great pic trainboy,we only see these locos on thru coal and container trains in Tx,so they're far and few between..I havent seen the Katy heritage unit here yet ! Its only been here once since it was put in service..Katy was a major player in Tx before the merger too..Most all UP traffic where I live is directional running and at night. Until they increase the amount of traffic I dont get to see too many trains,I have to work ! Videomaker

not that it matters, but trainboy quoted "my" picture [:D]

[Leon Silverman]

If EMD wants to sell locomotives with over 6000 hp, if would make sense to reissue the DD40AX chassis with the eight wheel trucks. These engines were rated at 6600 HP but had DC traction motors.

[DPD1]

I think another issue they've had with the big power, is the fact that having so much hp tied into just one unit, doesn't really allow for much flexibility. If one unit is down, you're in a lot more trouble with that much hp. Traditionally, if you look back in history, the mega hp units never really have been popular. But they seem to keep on trying them anyway. I would be very surprised if they come out with this rumored new unit, but you never know.

I've been tricked by the UP 90s with the new nose too... Saw one the other day and thought it was an ACE.

Dave
-DPD Productions - Featuring the TrainTenna LP Gain RR Scanner Antenna-
http://eje.railfan.net/dpdp/

[CSXrules4eva]

Well I guess if EMD were to come out with a unit like the SD100AC or something like that, I would imagine that it would have close to 7,000hp or maybe 8,000hp who knows. It seems to me as if the railroads need to think about rail technology in strengthing the steel or finding different ways of welding it. In this way the rail would be able to hold extra weight, and it would also be able to handle the extra horsepower.

[Anonymous]

if you have enough wheels/axles you can put as much weight in the locomotive as you like. And with enough weight you could put as much hp as your engine can make.

But I doubt it is possible to put more than 6000hp through standard C-C wheel arangements unless you make some kind of sticker wheels :)