The extinction of 4-axle units?

[Overmod]

Randy -- what parts of the AC equipment have to be large?

Remember that even the larger sizes of supercapacitor banks consist of a large number of small elements, and hence can be in enclosures of just about any shape or number, and the inductors required for that part of the AC synthesis, even at high horsepower, shouldn't have to be particularly bulky. Aside from that... IGBT sextuples for push-pull on all three phases can't possibly be that large. Control logic the size of an industrial PC would be massive overkill for AC synthesized drive of any sane complexity, even for "locomotives" with scores of individual axles to control.

Of course, it being YOU saying it, there has to be something important I'm missing. (Just don't assume that the stuff GE and EMD are currently providing are necessarily 'state-of-the-art' for high-horsepower AC drives! Tell us what you know!!!)

[Randy Stahl]

The current G.E. phase modules are about 2' by 2' . this does not include the caps. G.E. uses one module for each traction motor. I'm used to the big electrical "rooms " on dash 9 and A.C. locomotives., that space would not be available on an engine the size of a GP-40 . Doesn't Amtrak run some 4 axle A.C. locomotives ? And don't they have some really long wheelbase trucks ? Keep in mind long wheelbase is undesireable for freight locomotives.
I would like to hear more on this topic.
Randy

[broncoman]

Does anyone know if they have ever tried one bigger traction motor geared to both axles, instead of one TM per axle?

[Overmod]

Whoa there, big fellow -- the French, among others, have made something of a science out of "monomoteur" bogies... some of which even included change-of-speed gearing (alas, not selectable 'on the fly'). The single large traction motor sits up in the carbody, as sprung weight, and the connections to the axles are made via "Cardan shaft" (think driveshaft with splines and universal joints) in most of the modern approaches.

What you say about traction-motor frame sizes is true (except, of course, that you can use a longer truck wheelbase and taller wheels to get a bit more room). But you certainly aren't giving up the 'rotating truck' in favor of a rigid frame... if anything, the monomoteur trucks are considerably more flexible, have better primary and secondary suspension and guiding, etc. etc. -- oh yes, and they don't slip as readily, either, and the cooling of high-performance traction motors is ever-so-much easier when you don't need finagly little flexible ducts from the blowers down to somewhere between the sideframes. If you're obsessed with truly ridiculous detail, you can even go to hydrogen cooling as with generators and reduce much of the windage on high-speed motor armatures.

This is the motor and truck construction that gained the rail speed records for the French in the 1950s. I would be astounded to see any nose-suspended traction motor truck capable of anywhere near that range of speed.

As a side note: the diesel-hydraulics that were tried here in the early '60s used Cardan-shaft-conjugated trucks. That included the "Alco-Haulics" (DH-643s, weren't they?) which showed such good antislip behavior that...

the suggestion was made, apparently seriously, to extend the axles on the AAR type B trucks on some FAs, and put cranks and siderods on them to conjugate against wheelslip. Might have worked at low speeds, but think of the fun with equalization! No other particularly good way to do the job... with nose-suspended transverse motors filling up the truck frames, that is.

BTW, modern trucks don't exactly 'rotate' as the locomotive goes around curves -- the good ones don't have a center 'pin' and are constrained in all motion axes by struts, rubber bushings, shock absorbers, etc. Gives a better ride, less damage, and is easier to maintain to boot... and simplifies the 'bolster' design to an even more optimal geometry than that observed in a Blomberg swing-hanger truck.

Broncoman, the big point with American diesel design is that the packaging works better with underfloor truck-mounted traction motors. That's an evolutionarily-proven configuration. Trucks at each end with a big fuel tank hung between leaves everything above the frame open for motor, generator, ancillaries, cooling, etc. If you're using carbody traction motors, you need to leave motor space somewhere roughly over each truck center... and that's not real convenient for building the shortest possible locomotive with a big engine and a cab where modern locomotives have them.

[Anonymous]

I was under the impression that GE AC locomotives had a separate inverter for each axle, while EMD locomotives have a single inverter for each truck. I read an article in Extra 2200 South that proposed some interesting questions of how this will affect wear patterns of wheels and that the long term effects have yet to be determined. The article was carefull not disclose any proprietary information, but proposed that wheel slip control of individual axels would promote increasing differences in wheel diameter over time, and that group control of axels should have an opposite effect of minimizing differences in diameter over time.

If space is a problem, then EMD's single inverter per truck might make more sense for a four axle locomotive. Group control of axel speed might also be better suited to a four axel locomotive if the long term effect of minimizing differences in wheel diameter proves to be important.

I just checked "GE Locomotives" by Brian Soloman, and it mentions A GE P32AC-DM built for New York city's third rail electric ( DM = Dual Mode) as a succesor to the FL9. Unlike other Amtrack units, it is using 3 phase AC for traction power.

[Anonymous]

I think B trucks will be use only in small locomotives for yard uses. Here in Brazil the old CSX, NS, Conrail and Santa Fe B36-7 received BB+BB trucks by Vitoria a Minas RR, like its brand new dash 8 and 9. The company also use D trucks on a metric Sd45, that was called DDM45 by GM. Today we can see conrail and others USA locomotives painting running on BB+BB trucks. It´s very good to us who can´t go to USA to seen them on original trucks.

[Anonymous]

They might build some BB truck locos but time will tell.......[%-)]

[Anonymous]

QUOTE: Originally posted by Lone Byrd

They might build some BB truck locos but time will tell.......[%-)]

Yes, time wiil say. But here in Brazil we BB+BB class is growing up. EFVM bought 86 B36-7 in usa and now is buy another 80 sd45-2. All of them will run on BB+BB trucks

[Anonymous]

I suspect that the proliferation of the BB+BB in Brasil has two factors, firstly there may well be lighter rail/trackbeds down there and more importantly the locos are former standard gauge converted to either metre of 3' gauge(I forget the local gauge exactly) In this case you can either lift the loco higher or stretch rthe bogie to find room for all the equipment that fitted between the wheels on standard gauge. There may be a loading gauge restriction on raising the locos too much

Kev

[Anonymous]

Yes, the proliferation of BB+BB trucks on EFVM rr have an importante reason: the original traction motors can´t be used on meter gauge trucks. So, is it necessary to put more axles to get the same housepower of original locomotive.
EFVM have reveived visit of some US operators because the success of the innovation. The locomotive fit better them C-C trucks and has more adhesion on hills.
EFVM roadbed is very good and it uses TR68 rails.

Others rr in Brasil have imported locos from USA to, but because they are broad gauge (1,600 mm) they use de original traction motors and the same kind of trucks of original rr.

it´s neccessary to say that EFVM is the most importante rr in Brasil, and one of the world biggest iron ore carrier. It has 700 km long and run 20 pair of trains a day, with 160 or 240 vagons .

I´d like to add a photo of a Conrail or CSX on BB+BB trucks here, but I can´t do it. How can I do?

Pedrop

QUOTE: Originally posted by 45144

I suspect that the proliferation of the BB+BB in Brasil has two factors, firstly there may well be lighter rail/trackbeds down there and more importantly the locos are former standard gauge converted to either metre of 3' gauge(I forget the local gauge exactly) In this case you can either lift the loco higher or stretch rthe bogie to find room for all the equipment that fitted between the wheels on standard gauge. There may be a loading gauge restriction on raising the locos too much

Kev

[edblysard]

Pedrop,
Would like to see a photo of your ex Conrails,
We ship a bunch of older GE out to South America, I think we might be the last US rails they rolled over...
A lot of them are carry LCRX marks, and a bunch of old Conrails, still in blue...

E mail me if you get the chance..
Ed[:D]

[broncoman]

Mark,

Are SF30Cs a rebuilt U30C? I have seen that designation pop up a couple of times, and assumed this but wasn't sure.

Dave

[Anonymous]

QUOTE: Originally posted by broncoman

Mark,

Are SF30Cs a rebuilt U30C? I have seen that designation pop up a couple of times, and assumed this but wasn't sure.

Dave

[Anonymous]

Some GE demonstrators arrived here as "Super Seven" model, nubered in 3000 serie. They are rebuit U30C, that has the same large cab of Dash 8.

QUOTE: Originally posted by broncoman

Mark,

Are SF30Cs a rebuilt U30C? I have seen that designation pop up a couple of times, and assumed this but wasn't sure.

Dave

[Anonymous]

SF30C's were Santa Fe's rebuilds of U36C's. HP was dropped from 3,600 to 3,100. I believe a total of 70 were rebuilt, #'s 9500-9569. There was also an SF30B, which was rebuilt from a U23B.

[CSSHEGEWISCH]

Several responses: The SF30C is a rebuild by Santa Fe of its U36C's. They were numbered in the 9500 series on ATSF.

U30C's, C30-7's, SF30C's and C36-7's of BN, ATSF, NS and CSX ancestry have turned up on several Brazilian railroads, including ALL, MRS, EFVM and Ferronorte. EFVM is meter gauge, MRS and Ferronorte are 5'3" gauge, and I'm not sure about ALL.

I've noticed that four-axle locomotives are definitely in the minority when it comes to export designs, probably because of the need for lighter axle loads. Maybe our overseas friends can comment further about this.

[Anonymous]

All is metric gauge also.
The brazilian four axles locomotives are yard switcher or those used for short trains were the line contidion don´t accept bigger ones. EFVM has G12 model, made in US in the 50´s, but they are in a very good condition. They are uesed at yard operation only.
FCA and ALL also have a good fleet of G12 and they are used to pull trains at main line too. In this case, they use as many units as it necessary. On the Espirito Santo hill of ancient Leopoldina Railway FCA uses 7 or more G12, because the line do not accept C-C locos.

Pedro

QUOTE: Originally posted by CSSHEGEWISCH

Several responses: The SF30C is a rebuild by Santa Fe of its U36C's. They were numbered in the 9500 series on ATSF.

U30C's, C30-7's, SF30C's and C36-7's of BN, ATSF, NS and CSX ancestry have turned up on several Brazilian railroads, including ALL, MRS, EFVM and Ferronorte. EFVM is meter gauge, MRS and Ferronorte are 5'3" gauge, and I'm not sure about ALL.

I've noticed that four-axle locomotives are definitely in the minority when it comes to export designs, probably because of the need for lighter axle loads. Maybe our overseas friends can comment further about this.

[Anonymous]

Whatever happened to the ATSF using 4 axle power on its hot intermodal trains. I thought I read an article stating that the Santa Fe liked using 4 axle power better for its intermodal trains because they were more lightweight and faster.

Kraig

[Anonymous]

QUOTE: Originally posted by kraig

Whatever happened to the ATSF using 4 axle power on its hot intermodal trains. I thought I read an article stating that the Santa Fe liked using 4 axle power better for its intermodal trains because they were more lightweight and faster.

Kraig

I think it had something to do with the weight of the intermodals. Over the years they got continually heavier as intermodal business increased.

[Anonymous]

But my question is why is it becoming so extinct. When I watch all the CN trains go by the fire station here, they are 6-axle engines hauling long manifest trains. Now the Stevens Point to Green Bay train usually rates about 3 4-axle engines. So what is going on here. Most of the time I see the 4-axle units in switch service or local service. Maybe trains have just become too heavy for the 4-axle power.

Kraig

[GP40-2]

M.W. said:

"The question I have is how CSX justifies using A.C.s the way it does, in services that don't optimize the value of the A.C. transmission, which is very expensive. I wonder about TFM, too, but for all I know they like to run up their many enormous grades at 4 mph."

I think I can answer that question. Like we diiscussed in another thread, CSX has some very steep grades, but they are not as long as western grades. Even at 10 mph, Sand Patch would only take 2 hours in run 8 to reach the summit. On none time sensitive trains that exactly what they do to their ACs--load the tonnage up so they can get over the ruling grade at 8-10mph. They do this all over the system. In their view point it maximizes the use of the locomotive's power. No suprise, that's the advantage AC brings over DC. Sometimes the size of these trains can get crazy--18,000 to 20,000 tons with only 2 AC4400s!

Why they use the same AC4400's and SD70MAC on 70 mph intermodal is an interesting question. It could be that the are going for a standard fleet--all AC. This would standardize parts and service. ACs are 6-7% more efficient at high speed in converting traction HP to drawbar HP. This results in more power for high speed, or conversely if all that power is not needed, a savings in fuel for the same drawbar HP as equivelent traction HP DCs. There could be other reasons as well. Maybe because they buy so many AC, the builders are giving them some sort of volume discount.

It would be interesting if the Trains staff would interview CSX on this.

The one thing I am fairly positive about is CSX seems to have no intentions on buying new DC power. They are already testing the SD70ACe, and I hear they will more than likely place large orders for both the SD70ACe and the new AC GE Evolution.

I think some credit for CSX is in order. More than any other RR, thay have pushed the AC locomotive into see what it can really do. That's a lot more than it's stick-in-the-mud thinking neighbor, NS, has done.

[oltmannd]

GP40-2-

Here's some of those 4 axles in drag service:
http://www.railpictures.net/viewphoto.php?id=20739

Looks like GP9 in the mix, too!

With regards to your comments...

If you mix AC and DC locomotives regularly, you will never "see"what AC can do"!

CSX has often seemed to me to be " the smartest bunch of guys that can't run a railroad." They have some absolutely briliant people on their staff and some very talented people in general, but they never seem to be able to translate their good ideas down to the railhead. I suspect the purchase and use of AC power fits into this model. They probably had and have a plan with great justification for AC power, but no practical way to communicate, implement or refine the plan so that it works as intended.

On the other hand, NS is somewhat "stuck in the mud", as you put it, but they are managed such that the staff people are much more directly connected to the field supervisors and generally persevere with each new idea until it works. Some have opined that NS will "pound a square peg into a round hole."

Do you have a source for your statement that AC is 6-7% more efficient than equivalent DC at high speed? I find this really hard to believe.

Way back at the dawn of AC power, the arguement was that about 1/2 the benefit of AC would come from improved adhesion, and half from reduced motor maintenance, but neither alone would be enough.

[Anonymous]

If somebody here wants to see a picture of EFVM BB+BB ex-Conrail locomotives, please go to HLCX Export Move forum at Railroadforums.com


Pedro[:)]

[GP40-2]

The overall efficiency of AC induction motors has been discussed widely in industrial circles. Both GE and EMD specs show the increase in electrical system efficiency in the AC traction locomotives over the DC traction locomotives. The new AC Evolution and SD70ACe will have even more efficient electrical systems, thus broading the gap between DC.

If you want real world data, Al Krug has an example of a DC Dash 9 against an AC4400 on one of his sites. The Dash 9 came in at 88% efficient, while the AC4400 was 94% efficient in converting traction HP to drawbar HP in actual use.

[oltmannd]

Nah.... Those aren't real test results. Maybe 1 or 2% more efficient, but not 6 or 7%!

I'll buy that the solid state inverters are a bit more efficient than a commutator and that squirrel cage motors may have slighly lower resistance, and even the gear sets are a bit better on the ACs, but not THAT much. If it was 6-7%, even NS would be buying only AC - the fuel plus maintenance alone would pay the premium for AC.

[Anonymous]

QUOTE: Originally posted by jruppert

I was under the impression that GE AC locomotives had a separate inverter for each axle, while EMD locomotives have a single inverter for each truck. I read an article in Extra 2200 South that proposed some interesting questions of how this will affect wear patterns of wheels and that the long term effects have yet to be determined. The article was carefull not disclose any proprietary information, but proposed that wheel slip control of individual axels would promote increasing differences in wheel diameter over time, and that group control of axels should have an opposite effect of minimizing differences in diameter over time.

This is a case of someone who doesn't really understand creating a problem where a problem does not exist. From a wheel wear standpoint there is no difference between the GE and GM solutions. For the inverters to fire there must be a signal, and that signal is common to all the inverters. So if you have two inverters, six inverters, or 20,000 they are all firing at exactly the same rate. And so the synchronous speed of all six motors will be identical if you are on a GM or on a GE locomotive. The amount of creep each axle will experience will be due to the weight transfer, rail conditions, train speed and the like, and will be totally independent of whether there is a shared inverter or an independent inverter for each axle.

High horsepower four axle locomotives used to enjoy an advantage at high speed. That is because any DC motor will create a "back voltage" which increases with speed. A GP only had to overcome this for four motors, while an SD had to overcome this for six motors. Thus with a small enough load, a GP could achieve a higher speed than a same horsepower SD with an identical train. The use of AC motors negates this advantage. The AC motor always tries to reach the synchronous speed being put out by the inverters. So if you need high speed today, just use an AC.

The other change that has occurred is that air freight has taken away almost all of the "super hot" freight. Think FedEx. What the rails are concentrating on with the intermodal is the non overnight priority freight, where a lower speed is acceptable, but consistency is most important. That again means that the 4 axle locomotive loses its advantage.

[Anonymous]

We need to build more 4 axle locomotives. How about those short lines with light rail? The locomotive industry is ignorning the road switcher market and thats how railroads make money is on line customers. Give me an old GP-9 over any of the high tech locomotives anyday! They dont have computers that you need a DR to fix. U dont have to spend hours stalled in the middle of no ware trying to reset a stupid breaker or finding out a chip has burened out with make the locomotive a huge chunk of iron!

[Anonymous]

Todays high horse power locommotives are just to powerful and big! I have seen the CP use only one locomotive on a long train, if it breaks down. your done for!!

[Anonymous]

QUOTE: Originally posted by Junctionfan

The only decent 4 axle GE units are the P-42 which is designed for passenger service. GE sells nothing else from what I have seen on GE's website. I would imagine that the P-42 would be excellent roadrailer power.

Andrew -

As usual, you are WAY off base. There are several types of GE 4 axle freight units that are decent untis. They tend to have more maintenance needs then some of the EMDs, but as far as pulling power and fuel efficiency they are at least as good, if not better than their EMD counterparts. For example the Conrail B23-7s and Conrail (former Monogahela) B23-7Rs are good units. I know of one short line that replaced some of their EMD GP9/10s with B23-7s and are experiencing as much as a 25% fuel cost savings, very important in these times of high fuel prices, particularly for smaller roads that don't use enough fuel to be able to utilize hedging or bulk purchasing to mitigate the costs. The B36-7s and B40-8s aren't too bad either although they don't get as much of a fuel saving. Also, the GEs are 4-cycle turbocharged engines versus EMDs 2- cycle so in the higher horsepower (3,000 and up) there is additional power and actually less cost as the EMD turbos are much more often a maintenance issue and tend to be n issue much more often.

You might want to try some reading again, before blundering into a new area...

LC

[nanaimo73]

QUOTE: Originally posted by railroadjay

We need to build more 4 axle locomotives. How about those short lines with light rail? The locomotive industry is ignorning the road switcher market and thats how railroads make money is on line customers.

Shortlines can't afford $2+ million for a locomotive. There are a lot of GP40 and GP40-2s that can be rebuilt into a GP38-2.