The extinction of 4-axle units?

[Anonymous]

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

[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]

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.

[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.

[broncoman]

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

[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

[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 A.C. equipment takes up so much space now ..cramming all of it into a small locomotive would be difficult
Randy

[Randy Stahl]

The only limitation to making a high horsepower 4 axle locomotive is the physical size limitation of the traction motor itself. The motors simply need to be bigger, you can only fit so many windings in a D -87 motor. This is one big reason for A.C. motors< higher horsepower in a traction motor that is small enough to fit a locomotive truck.
Did you know that the traction motor leads on an A.C. motor are about half the size of a D.C. motor?
Randy

[TH&B]

4 axle units might also make a comeback if freight train speeds increase alot, maybe not tomarrow but 20 - 30 years down the road freights might need to go 120mph+ !?!

[broncoman]

So would it make sense to use slugs more as they would be accomplishing what a six axle does. It seems in another 15 years or so when you've rebuilt most gp-38s until its not viable to use the frame anymore to start using higher horsepower gp40s or gp60s with a slug to be able to use the horsepower and have usable MCS for road switching or even shortlines for that matter?

[railman]

As long as there's a branch line somewhere, the four axle unit will live on. Like the F Units that survived into the 80's.
On that note, BNSF runs it's tri-weekly run up the Monticello sub behind a GP-38 almost exclusively. An SD-40 made a guest appearance when a long ballast train made a pass, but that's been it. This line even had cabooses on a regular basis until just a few years ago, too.

[Anonymous]

NS still uses 4-axle's on many of their freights in the Atlanta area at least. We still see high-hood GP-38's and 50's all the time. They run the GP-60's on intermodal trains mostly but you never know what consist you might see. Several month's ago I saw a high-hood GP-38 running long hood first latched to a BNSF CW40-9 heading north out of Atlanta with a general merchadise run. We occasionally see the B30-7's with the high short hoods also. They've painted a rare low hood GP-59 in Southern green as well. That is a sight to behold. CSX runs a few GP-40's on local freights and at the rock quarry in Kennesaw , GA. They also run a B36-7 on the daily local north of Atlanta. I believe there are many years of service left for the 4-axles, but railroads find it more economical to run the big Dash 9's out on the road.

[Anonymous]

QUOTE: Originally posted by goat

C-Cs are just a fad, B-Bs will be back, like it was inthe 1950s !

Place a dozen B-B in pairs spaced evenly in a 200 or 300 car train, that could be the future. With automaticaly activated couplers between the units trains can be split and recoupled remotely for crossings and yarding or even multiple destinations.

Or MAYBE they will remove the axles from wheels and come up with something totaly different !?!

I don't think so. 6 axle units are too good at lugging cause they use more of their main gen. capacity and still have enough speed[:D]

[Anonymous]

C-Cs are just a fad, B-Bs will be back, like it was inthe 1950s !

Place a dozen B-B in pairs spaced evenly in a 200 or 300 car train, that could be the future. With automaticaly activated couplers between the units trains can be split and recoupled remotely for crossings and yarding or even multiple destinations.

Or MAYBE they will remove the axles from wheels and come up with something totaly different !?!

[locomutt]

QUOTE: Originally posted by drailed1999

I swear by my copies of Diesel Locomotives: The First 50 years, The Contemporary Diesel Spotters Guide ( 2nd edition ), the Field Guide To Modern Diesel Locomotives and from the other guys The Contemporary Diesel Spotters Guide ( year 2000 edition ). These are some of the best quick reference books out that I'm aware of.

I have a copy of Diesel Locomotives:The "First 50 Years",don't have the other 2 yet. Wish.
And if anybody misunderstood me,I will give up my copy;of "The Diesel Spotters Guide",
when it is pryed from my,cold dead,hands.[:)]

[Overmod]

Mook sez

quote

Will they ever go to something bigger than the 6 axel? Or have they reached their limit in length and axels?

/quote

DD40s worked fine on UP, probably wouldn't cut it on most other railroads with that long rigid truck wheelbase.

Steerable trucks work best with a 'center' axle, which a D truck doesn't have; swingout on longer trucks (i.e. "E") would be mechanically uneconomic... we won't go into what would be needed for proper bolstering and weight transfer on such a thing.

Future of anything larger than C-C units would, of course, involve span bolstering of 'conventional' truck sizes -- B-B for four axles (as on the more successful version of double-engined GEs around the time of the DD35s and DD40s) and C-C as on the Norfolk and Western turbine 2300. Allows full interchangeability of parts, underframes, etc. with regular locomotives.

Why bother with anything else? Centipede underframes were demonstrated to be less effective than separate trucks a half-century ago. Interestingly enough, America hasn't embraced a B-B-B configuration under a single carbody (instead of C-C) even though units both here and abroad have been tried.

[Anonymous]

I swear by my copies of Diesel Locomotives: The First 50 years, The Contemporary Diesel Spotters Guide ( 2nd edition ), the Field Guide To Modern Diesel Locomotives and from the other guys The Contemporary Diesel Spotters Guide ( year 2000 edition ). These are some of the best quick reference books out that I'm aware of.

[locomutt]

QUOTE: Originally posted by M.W. Hemphill

I wouldn't! It's still a good book. I have one and I still use it.

I would not give up that book,for anything,and I just got the Kalmbach book
on GP-7,9's Like I'm building 3 models of GP-9's[:)]

[locomutt]

QUOTE: Originally posted by Mookie

Will they ever go to something bigger than the 6 axel? Or have they reached their limit in length and axels?

Mook

Look at the DD-40's[:)]

[Anonymous]

QUOTE: Originally posted by Guilford350

QUOTE: Originally posted by dougal

NS uses GP60's on four intermodels around here, while they were designed for RoadRailer service I have yet to see one on a RoadRailer and I'm sure I never will.

Didn't NS use GP60's on roadrailers back in the early 90's? I thought they did.

They did, I think they still use them in that service in the Southeast.

[oltmannd]

QUOTE: Originally posted by tree68

On a philosophical note - Who uses the 4 axle units? The folks who keep traffic supplied to all the 6 axle units. The extinction of 4 axle units may well bode ill for the world of railroading.

There are enough 4 axle locomotive in existance to serve the industry for the forseeable future. What fuels new locomotive purchases for line haul service is improved fuel efficiency and a reduction in fleet size. For example, an SD70 is about 20% more fuel eff. than an SD40-2 and you can replace 4 SD40s with 3 SD70s (more or less). That generates a decent return on investment such that it's cheaper to buy new than rebuild the old.

4 axle units in light duty service, such as local or branchline work, don't burn enough fuel that saving 20% of it would amount to much. Also, it is not likely that there would be much of a replacement ratio, either.

This being the case, it is better to just maintain or rebuild in kind than purchase new. You can keep a GP28-2 going almost indefinitely. There may still be some running after we're long dead!

[Mookie]

Will they ever go to something bigger than the 6 axel? Or have they reached their limit in length and axels?

Mook

[tree68]

On a philosophical note - Who uses the 4 axle units? The folks who keep traffic supplied to all the 6 axle units. The extinction of 4 axle units may well bode ill for the world of railroading.

[ericsp]

I too am sure that 4 axle locomotives will be around for a while. However, don't think there will be any high horsepower 4 axle locomotives built in the future, unless they can get more of that horsepower to tractive effort.

[DPD1]

QUOTE: Originally posted by macguy

There are still sections on the old BC Rail right-of-way that use exclusively 4 axle units.

...this of course is because of curvature issues.

There's also a lot of shortlines that have weight restrictions on certain wood trestles and other spots on the line. So I'm sure 4 axle stuff will be around for sometime, even with the proliferation of used SDs out there. Which is good, because I've always liked the geeps. :-)

Dave
Los Angeles, CA
-Rail Radio Online-Home of the "TrainTenna" RR Monitoring Antenna-
http://eje.railfan.net/railradioonline

[Anonymous]

QUOTE: Originally posted by dougal

NS uses GP60's on four intermodels around here, while they were designed for RoadRailer service I have yet to see one on a RoadRailer and I'm sure I never will.

Didn't NS use GP60's on roadrailers back in the early 90's? I thought they did.

[edblysard]

Go to:
http://www.gmemd.com/en/locomotive/switcher/gp15d/index.htm
and take a look...
EMD 15D and 2000Ds, 4 axel road units/switchers.

No, not high horsepower, if 1500 or 2000 hp is considered a low hp, but UP has a fleet of both, leased from CEFX running all over the place down here, you see them routinly hauling 100 car freights all the time, at track speed.

Ed[:D]

[Anonymous]

EMD doesn't even list a high horsepower 4 axle road switcher to date and according to the Field Guide To Modern Diesel Locomotives, the last GE 4 axle Dash 8's were build the spring of 1992 for the Santa Fe

[Anonymous]

There are still sections on the old BC Rail right-of-way that use exclusively 4 axle units.

...this of course is because of curvature issues.