Western Railroad Discussion > SD90MAC Problems

With all the trouble surronding the MAC's (excessive vibration, reliability with the H-engine, etc), what is going to become of the engines UP has on the property? Will GM pick up the tab to get them up to par? Will UP ask for a refund and exchange the units for some others? Will UP just not buy anymore?

If there are any engineers out there, what do you think of the 90MAC? Does the H-MAC load better than the 43? (Four stroke higher HP compared to lower HP two stroke). Do they really get down and lug or is all the hype overblown?

Grant

The 90mac-H and 9043's are basically junk when compared to the AC44's. For a comparison the 6000 hp H 90macs have the same tonnage rating on the Moffat in Colorado as the AC4400's. The 9043's tend to slip badly below 10mph, however they are a little better than they we're a couple years ago (upgraded software). The AC44s rattle quite a bit but these things are pullers and highly reliable. The 9043's cause a lot of problems this is partly due to poor electronics. The horror stories from the 9043's are endless, they were banned as leader or remote linked units for quite sometime on the Moffat. As a railfan those 9043/90H's lok great, as railroader give me a AC44 every time.

JC76

jc76 wrote:
>
> The 90mac-H and 9043's are basically junk when compared to the
> AC44's.
Hmmm, that seems to be quite the opposite of the reports over the past few years on trainorders. Reports from the past claimed that the 9043 were quite reliable and that the engineers liked them. Reports on the AC4400s were that they were great until you have wet rail then they slip like crazy. I believe each loco has its own niche and service. But that's my just my take.

Bryan

The Mac 90s may perform well in some services, some guys like than on freight trains where grades are not involved. But a commonly heard phrase on the Moffat is Oh NO! we have a Mac90 today.

As for the AC44 on wet rail, a year and a half ago we had 4500 tons on a MDVRO in the rain, with two SP AC44s. By the time we reached Rocky we were at 5 mph. When we got to the wind break on the big ten we were down to 0.1-1 mph but they kept pulling and didn't tear the train apart, another time on pushers out of tabernash we had a AC44 convertable and we reached in incrediable 180,000 ils of tractive effort.

I will give EMD credit on creature comforts, but when it comes to pullin' the GE's win in my book, time and time again.

A buddy of mine had a coal load on the Greely Sub (1.4%) with Three ACs the lead unit was a 9043 when they hit the flange oiler in the middle of the curve the engine freaked and dropped it's load and stalled the train once the computer caught up they cntinued there crawl at 13mph. A freind of this same friend works on the Utah Rwy where they tend to get alot of UP 9043s on coal trains. He said they have tons of problems with these machines, including one instance while climbing Solider Summit where the computers all went dark and all three 90s shut down...figure out that one. The AC44 on the other hand has gotten a good reputation in Mountains of Colorado, other than the stupid desks shaking....but like Brian said every unit has its good and bad.

JC76

I believe GE has a superior AC locomotive both in terms of pulling power and reliability, as expressed in the above posts. EMD has the advantage of quiet and comfort--unless you happen to be on rough track. The EMD's will bruise kidneys on jointed rail or rough frogs. Engineers seem to favor the GE AC's by about 100 to 1, both on grade territory and on the flatland.

Regarding the H-MAC's, their low-end tractive effort is limited by roughly the same electronic load program/traction control system as their 9043 cousins; they produce no higher effort at low speeds.

Having said all that, I still don't believe the EMD AC's are inherently flawed. Much can be accomplished through electronics modifications these days, so perhaps the bugs can yet be worked out. As far as reliability, the early GE AC's had their share of road failures too, but the EMD's have had more to date.

It's not just AC power. On BNSF, KC-West the DASH-9's we've been using for the last few years converted a lot of "EMD Forever" hogheads, myself included. Even when we got the new SD-75's in both versions, they could not compare with the GE's ride, pull or reliability. The EMD's are now refered to as "bell ringers". If you get an alarm bell, just look for the EMD in the consist.

Sounds like EMD should have just kept making SD40-2s...
Most railroaders I have talked to said they were/are very reliable.
Even back in the late 70's, the GE dash 7's were better luggers than
the EMD's. Sounds like this trend is still the case...

jc76 wrote:
>
> The 9043's tend to slip badly below 10mph,


I am curious how many railroaders mistake the deliberate "earthquake mode" that the units operate in below 10 mph as a fault of the unit, when its actually a deisred outcome?

I always hear of complaints about low speed operations, while never hearing of a crew's acknowledgement of the as-intended earthquake mode.

earthquake mode? I don't know what that means, but I do know, as has been discussed before, the sd-90's, for whatever reason, simply do not get enough power/traction to the wheels at low speeds. I have never seen them put out more than 100 000 pounds of tractive effort sustained for any length of time. You go back, and you're ge will be putting out 140-150 000. I've never had a problem with a ge on wet rail. I work in bc canada in the mountains, practically in a rainforest. I think they do give up some tonnage in wet/snow, but they don't really slip and I've never seen any stall. The emd's, on the other hand, will put out lower and lower tractive effort on a heavy lift or on wet rail until they stall. Again, great cabs and usually a good ride but give me a rattling ge for pulling anytime. BTW, the H engine "true" MAC-90's I don't think were meant for low speed heavy pulling as their tonnage rating is the same as an AC44 or even a 90-43. They were meant for high speed pulling...they put out more than twice as much tractive effort at 60 mph than an SD 40. Only an sd-40 will never shut down the consist because of a computer. Again, we think it's just software glitches in the mac's, however these problems have been around for a while now and there's been little improvement
s

Its a mode that engages at slow speed, where the software causes the unit to bounce agressively as it finds the exact amount of bite to apply to the rails. Its sort of the same max adhesion concept behind Super Series, but only more agressive. The earthquake mode will allow an SD80/SD90/SD9043 to actually increase speed when it kicks in below 10 mph. See CTC Board magazine article on CR SD80MACs for more info.

Its probably a case where the lack of familiarity to the shake caused crews to complain such that the units were shopped to have the software changed to a different or lesser version, which stops the bounce but also is responsible for the lack of tractive effort on units that you see today.

Forgot to mention thats why EMD came out with the I-cab, too. It is a necessary requirement on all units with the earthquake software. The I-cab came out in 1994 and tested on a CR SD60M, but was really designed to mate up with the H-platform (SD80 and above) currently under development. The H-platform models came starting in 1995, and all have the I-cab.

yea, that's what i thought you meant about the earthquake mode. Our ge's do do that...bounce and rattle hard at low speed getting grip...its not much different than the usuall rattling ride, unless i'm getting used to it...we climb 25 miles up 1.0 % grade with 3 ge's trains from 15 to 17000 tons...11 mph with the ge's, little less in winter, steady. The sd90's under the same conditions just do not put out the same tractive effort. We assume the computer cuts the power to the wheels when they slip. the ge's do the same thing by cutting power when the wheel slips but it seems to be able to put the power back while the sd's just keep reducing...they fight to keep tractive effort at around 90-100 000 pounds like i say while the ge is loading 140-150 or more. the sd's still bounce and shake under heavy starting loads... again, i don't know if its just software(i doubt it) or what but I would like to see the bugs ironed out because I'd much rather ride in one than a ge unless I've got a heavy train to go uphill.

CX-99 wrote:
>
> [Earthquake is]... a mode that engages at slow speed, where the >software
> causes the unit to bounce agressively as it finds the exact
> amount of bite to apply to the rails....
> Its probably a case where the lack of familiarity to the shake
> caused crews to complain such that the units were shopped to
> have the software changed to a different or lesser version,
> which stops the bounce but also is responsible for the lack of
> tractive effort on units that you see today.

Thanks for defining the term. I know what you are talking about, but I'd never heard it called that. I don't profess to know anything about the design process or what the designers intended, but I'll try to give some impressions based on real world GE vs. EMD AC operating experience.

It has been my beleif that MAC-90's lack of low speed tractive effort is caused by TE reduction on account of a detected wheel ship. The problem, in my opinion, is that the 90's tend to rise to maximum effort rather quickly instead of easing into it gradually like the GE's do. I'll explain.

After recovering from a low speed wheel slip, (which causes a software induced tractive effort reduction in all AC locomotives), GE's ease back into TE a little at a time until maximum effort vs. rail adhesion limit is found. In the same situation, EMD's attempt to resume maximum TE all at once, which triggers another wheel slip and cooresponding back off of tractive effort. This pattern continues to repeat until the EMD's software concludes that the condition is a constant wheel slip, which reduces TE further and causes it to stay reduced. It's much like applying too much accerelator pedal on an icy road in a automobile.

The tendancy I've described of EMD's to default to attempting maximum tractive effort during slow speed/high tonnage pulls is evident in all other modes of operation and throttle settings as well. CX-99 mentioned something about when the earthquake mode KICKS IN below 10 mph, and I think inadvertently revealed the root of mac-90 problems in the process. I'll explain further.

It appears to me that most of the software functions on the EMD mac-90 are either "off" or "on" depending on the situation, instead of more seamless incremental steps and values like the GE's are. I can best describe this as being like an on-off light switch vs. a dimmer switch. When controling things like tractive effort in a paticular throttle notch, the choice between nothing or full on is not the best way to do things.

As I said earlier, I don't pretend to know about locomotive design or electronics. My thoughts are based only on operating experiences and a limited general knowledge of locomotives. If I've overlooked something, please let me know...and sorry about being so long winded.