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  • Help with tractive effort/horsepower

  • General discussion about locomotives, rolling stock, and equipment
General discussion about locomotives, rolling stock, and equipment

Moderator: John_Perkowski

 #259769  by Jay Potter
 
I wouldn't say that the other traction motors remain at "full power". I'd say that the reduction of power to one motor does not automatically cause a reduction in power to the other motors. For example, if a GE AC unit pulling upgrade encounters grease, the wheels on its number one axle will lose adhesion; and whatever power level is going to that traction motor will be reduced in an effort to regain adhesion. When the wheels on number two axle reach the grease, the power to that traction motor will be reduced, but only in the amount that is necessary to compensate for its wheels' loss of adhesion due to whatever grease still remains on the rail. The power reduction to number two axle should be less than the power reduction to number one axle had been because the passage of the first set of wheels will have conditioned the rail to some extent. This progression will continue, axle by axle, with the traction motor on each successive axle needing less of a power reduction than the preceding traction motor had needed. In other words, if you consider the aggregate power reduction for all six motors, there will be less of a reduction with single-axle control than there would have been if each axle had not been independently controlled.

 #259790  by UPRR engineer
 
YUR back peddling now, you said no loss of power to the other traction motors, and coming up with crazy stuff like..."less than the power reduction to number one axle had been because the passage of the first set of wheels will have conditioned the rail to some extent." Pure speculation is what all that is, im pretty sure it doesnt work like that, im gonna check it out for you to be sure. You have no idea what its like to stall out, let alone hit a greaser with a heavy train. I do the things you read about, i keep giving you the benefit of doubt. Being a locomotive engineer who see first hand how GE's handle wheel slip, i think your wrong. Like i tell my girlfriend when we argue, stay on topic, dont bounce around from wheel slip, greaser caused wheel slip, AC vs. DC, GE vs. EMD. So what is it you want me check out for you? When one wheel slips does power get reduced to the other traction motors? Im not a walking engine manual, but i do get to see this stuff work first hand. Im gonna watch closely what happens when a wheel slips dude, and let you know how it goes.

Besides your 2nd hand CSX handout, wheres your information coming from dude? What is it you do for work? Not much in your profile there buddy. Kinda like to know your not a Frosty Cream employee.

Good talk going on here.

 #259860  by Jay Potter
 
Thanks, I'll be interested in what you find out first-hand.

With regard to your series of questions about me. . .

My CSXT "handout" came directly from CSXT.

The rest of my "information" came from having attended various CSXT AC-traction testing sessions that were conducted in the Allegheny Mountains of West Virginia, which is where I live, during the past seven years and discussing those tests with the CSXT, EMD, and GE representatives who participated in them. In other words--and I suppose that this is what you're most interested in learning--the technical information contained in my posts has not come from railfan magazines or elsewhere on the Internet; and I didn't just make it up. It's come directly from either the railroad or the two manufacturers.

If, as I gather, you believe that there's something inadequate about being a "Frosty Cream" employee, I don't agree. West Virginia has far fewer "good" jobs than do most parts of the country; and we have a great many good people who are underemployed. I'm more fortunate than most. I'm an attorney. I also have an engineering degree from the Naval Academy. Perhaps we can cut a deal? I'll think well of you and treat you with respect because you run a locomotive if you'll think well of me and treat me with respect because I ran a gunboat in Viet Nam.

 #259883  by RailBus63
 
Play nice, guys, and maybe we'll take you both to the Frosty Cream - double-dip cones for everyone! :P

In all seriousness, great discussion from both sides - I've learned a great deal more about this new technology, what it is supposed to do, and what actually is happening out in the real-world environment of heavy-duty U.S. railroading.

JD

 #259901  by JohnR
 
Hi Jay,

Could not what UPRR engineer is saying that he observes in his experience be caused by a cascade wheel slip condition? It seems conceivable that when the first wheel slips on a truck that the load is transferred to the remaining non-slipping wheels. These wheels, which are probably already running at their adhesion limit, cannot maintain their adhesion with this additional load and then they too begin to slip. This slipping of all of the wheels could occur within such a short time interval that without the aid of monitoring equipment providing a simultaneous time trace of the power and/or slipping conditions of each wheelset the apparent result to a human observer is that power is reduced to all of the wheels at the same time.

I know that in theory GE's implementation of "single-axle control" in their AC locomotives is supposed to be better than the approach that EMD took in their AC locomotives with control only on the wheelsets of the whole truck, but in practice is that really the case? CSX has AC locomtoives from both GE and EMD. Do they consider one technical solution superior to the other?

Thanks.

JohnR

 #259930  by Jay Potter
 
John, I can't give good answers to either of your questions. I do agree that the adhesion corrections can occur too quickly for a person to differentiate among the various things that the adhesion-management system is doing at any given time. The people who do the CSXT testing have a good idea of what's happening--sometimes enough to make adjustments during the tests--but many conclusions aren't reached until after all the test data has been compiled and analyzed more thoroughly by the manufacturer.

I think, in the scenario that you outlined, that the trailing non-slipping wheels might not necessarily be on the verge, so to speak, of slipping. This is because GE's latest adhesion-management software provides for increased power to be directed to those wheels. Each traction motor on a conventional AC4400CW is limited to producing 30,000 pounds of tractive effort; however the advanced software increases that limit to 36,000 pounds. So when an axle begins to slip and current to its motor is reduced, the system determines which other axles are least likely to slip and directs increased current to them. And if rail conditions enable a given motor to produce 36,000 pounds of tractive effort, the system can direct to the motor enough current to produce that tractive effort. Based on this, I believe that slippage of one axle doesn't necessarily mean that torque to other axles cannot be substantially increased.

CSXT hasn't taken a position as to whether single-axle control or per-truck control is superior. However the fact that its last two orders (which were for DC-traction units anyway) went to GE isn't an indication that it won't be placing future orders with EMD. As recently as last month, CSXT was testing SD70ACes with advanced adhesion-management software. Perhaps the most realistic way to look at the locomotive-acquisition process is to view traction-control as only one of a number of factors that CSXT would consider before deciding which locomotive model to order.

 #260150  by UPRR engineer
 
Thanks Jay, one more question here buddy. Whats a guy with a engineering degree from the Naval Academy who fought in Nam, turned attorney, doing on various CSXT AC-traction testing sessions?

Worked last night there Jay, all i dogcaught was double stacks that were powered up. Second train i brought in had a brand new GE on the point, all i was able to observe/test was the adhesion with the dynamic brakes. Came in super hot to stop out front of the depot, 30 mph about a half a mile from where i wanted to stop i rapped her out trying to get that awful axle hop. I couldnt get the reaction from the motor that i was wanting, slide the wheels a bit, too many motors, but i did notice on the traction motor screen, at about the time i was expecting the locomotive to shutter as i tossed the anchor out, ALL the dynamic effort left that number one axle all the way to the depot and more effort was transferred to the other five axles..........." Damn that dude named Jay" :-D Soooo theres one test, on fairly flat track, with high horse power and a light train. Hopefully the next one will have some weight to it, shouldnt be too long, see what happens when the other axles slide a bit, see how it handles that.

 #260239  by Jay Potter
 
The only things that I do at the testing are to watch, listen. and ask questions every now and then. I contribute absolutely nothing, except maybe to show the people who are doing the work that someone outside the industry thinks that their work is really important. What they're basically doing is figuring out how to move more tonnage without increasing horsepower. That's not the kind of thing that's going to make headline news anywhere; but, in my view at least, it's significantly more important than a lot of work that a lot of people outside the industry are doing. I recall years ago when either UPS or FedEx went on strike, I think around Christmas. The news was filled with stories about how many people were being inconvenienced and how bad that was for the country. Eventually some business commentator--and I wish I recall who he was--made a comparison to the railroads. He admitted that a whole lot of people really were being inconvenienced by the shipping company strike. But he contrasted that with what would happen if Union Pacific stopped operating for even a short period of time. It wouldn't be a matter of personal inconvenience; it would be a matter of entire industries shutting down. All in all, I think that railroads are pretty generally underappreciated. So if EMD or GE thinks that it's figured out a way for CSXT to move more tonnage, I think that's something worth watching.

 #260255  by UPRR engineer
 
Thanks Jay, one more question here buddy. Whats a guy with a engineering degree from the Naval Academy who fought in Nam, turned attorney, doing on various CSXT AC-traction testing sessions?

 #260292  by Jay Potter
 
That's the question that I just tried to answer. I don't do anything out there except pay attention to what the people with genuine expertise are doing. The people watch what the locomotives are doing; I watch what the people are doing; and if I pay close enough attention to the people, I end up learning something about the locomotives.

 #260376  by GOLDEN-ARM
 
To point out another simple fact about "high-adhesion" locos. When you are down to single digit speeds,(although this may occur at any speed) at full throttle operation, there are occasions where a wheelset, or multiple wheelsets will lose adhesion, with the rail. The new locos will let that "spinning" wheel accelerate slightly, at a controlled rate of speed, until it is able to gain adhesion again. This is known as "wheel creep", and the loco continues to produce full power to the wheelsets that have maintained adhesion. The wheelset(s) that are not adhering to the rail, are spinning, several mph faster than the other wheels, that are still pulling. This produces a loud "ringing" sound, similar to that of a wet finger, run around the rim of a crystal glass. Where applicable, the loco will sand automatically, and as the "slipping" wheelset regains adhesion, full power is restored to that particular set. At no time did the other wheelsets lose power. In older systems, when one wheelset slipped, the loco would compensate, by dropping, or severely reducing the load, then gradually restoring power, to the wheels. Problem was (is) that each time you lost power, loco slowed even more, power was applied, wheels slipped again, and this was repeated until train stalled, due to loss of traction. The new, "high adhesion" locos will now pull to a stall, but with full power being applied to all wheels, unless a set is "creeping". As traction motor heat builds up, though, some locos will reduce power, by about a third, in an attempt to allow motors to cool. Sometimes, this results in a stall, due to reduced tractive effort. Same situation though, as full (reduced) power will be available to a complete stall, without slippage. (creeping notwithstanding) Those manuals that were refered to earlier, while handy for mechanics, don't really come into play, out here in the very real world, of pulling trains over mountains. We will sand, modulate the independant, and PRAY, in an attempt to make the summit. Not much use in some mechanical manual out here. Hope this helps a little........ :-D

 #260409  by byte
 
Has EMD ever showed any interest in making an all-axle wheelslip control system, rather than the two-truck version they have now? I can't say I know too much about the extreme inner workings of locomotives, but it doesn't seem like it would be a big deal to engineer and produce. (Correct me if I'm wrong, but wouldn't the potential changes made be only in the software and circuitry of the electrical system of the locomotive? In other words, nothing mechanical structural.)

 #260434  by Jay Potter
 
I don't know what design changes would be necessary if EMD were to adopt a version of single-axle control; but I expect that the changes would center around the cabinet behind the cab on the locomotives' left side. This contains the "inverters" (two on EMDs and six on GEs). On both DC- and AC-traction units, the locomotive's alternator produces AC current that is internally rectified to DC current. On a DC-traction unit, that current is transmitted directly to the traction motors. On an AC-traction unit, the current is transmitted to the inverters, which convert that DC current to AC current; and the AC current is then transmitted to the traction motors.

I also don't know what sort of consideration EMD has given to adopting single-axle control. However I can say that I've spoken to a number of EMD representatives; and none of them have ever given me any indication that they considered their one-inverter-per-truck design to be inferior to GE's one-inverter-per-axle design. Although the enhancements that GE has been making to its single-axle control system are interesting to me, I don't know enough about any of this to have a personal opinion as to which manufacturer has the better system.

 #260555  by Nelson Bay
 
[quote="UPRR engineer"]So your positive, from what you've read or heard..... full power remains to all the other traction motors? No reduction of tractive effort except to the one that slipped? You might be right, ill bring that screen up next time and let you know. But it sure doesnt feel like it, and the tractive effort bar/meter on the main menu screen says other wise to what you claim. Ill find out in the real world and let you know.

Jay,

You're correct about the GE single axle slip control- isn't it possible UPRR engineer, who's "been there", is also correct regarding power reduction to all motors in certain situations? What happens during a simultaneous all axle slip situation on these units? I'm not referrring to the wheel creep allowance. System voltage would rise dramatically during a simultaneous slip. On older locomotives power would be dropped to all motors when the voltage reached a predetermined level. Is there overvoltage protection on these units?

Regarding your riding during tests and contributing nothing- sounds like a job I could handle. Does it pay well? Are they hiring?

 #260634  by UPRR engineer
 
Im not asking what you did while on the power there Jay. How/Why, did you set foot on a CSX locomotive test? I havent taken my divorce lawyer along with me on any trips?