The extinction of 4-axle units?

[gabe]

Mookie's GP/SD question reminds me of a question that I have been pondering for some time. Are 4-axle locomotives becoming extinct? I know the GP-60 sold some, but did it sell a lot and is there a successor planned? Does GE even make a 4-axle unit?

Is there any advantage of having a 4-axle unit on a well maintained main line with no sharp-radius curves?

It seems to me as though the 4-axle unit is becoming extinct outside of yard work, can someone tell me how accurate my assessment is?

Thanks,
Gabe

[Overmod]

See the thread I just posted over there in Mookie's "Why?" thread...

The advantage of the four-axle unit is that it has fewer axles, and less associated cost (e.g., 4 traction motors instead of 6 to stock and maintain, less mass in the truck frames, etc.)

There is still an advantage in very-high-speed service to having two-axle power trucks, in part because the mass of the required sideframes can be less for a given set of guiding characteristics (and the additional mass required for steerable outer axles adds up too). Theoretically a two-axle truck is a bit easier to cross-equalize.

Aside from that, there's a clear advantage geometrically in going to a three-axle steerable truck (such as HTCR-II or FlexiFloat) -- on a main line with transition spirals and "no sharp-radius curves" the effective rigid wheelbase of such a truck is zero. Much more difficult to make this work with a two-axle truck that has a pivot to the carbody. Bolster design, secondary suspension, etc. generally better. Also better weight distribution on the axles during acceleration or braking...

Not much call for power per axle above what existing, stocked designs of TM are putting out. That severely limits the 'viability' of high-horsepower 4-motor units... and about the only place it would pay to build such units 'new' would be in very fast intermodal, or passenger, service.

I think the real point is that the four-motor unit market is quite nicely supplied by the used-equipment market... both with respect to anticipated needs and to a source of low-cost parts for 'new' locomotives (cf. the Green Goat). Seems that the 'minimum' power for RoadRailers is a six-motor unit, and for other mainline trains either a pair or triple of six-motor units. "Road slugs" might benefit from two-axle trucks, to save weight or length, but... see above; nobody buys slugs new and keeps their job for long!

[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.

[locomutt]

Please correct me if I'm wrong(which I probably am), weren't 6 axles developed
to cut down on wear on lighter trackage?To distribute the weight more evenly?

[locomutt]

Thank You,Mark:
I wish our public library had more info on things like this,
and know other places to go to online,to get this info.

[Anonymous]

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.

[locomutt]

QUOTE: Originally posted by M.W. Hemphill

Locomutt: Actually, practically everything I've ever said on locomotives in this forum can be found in things quite accessible to you: the various Kalmbach diesel spotters books (I would get them all, and read them all, and they're cheap at flea markets), and the four-part series "The Diesel Locomotive from D to L" by Vernon Smith, which appeared in Trains in 1980 (again, easy to find used copies at flea markets or on line). There's little that's changed in 24 years in the diesel business since Smith typed that wonderful series.

Thanks Mark,
Maybe I can retire my 1st edition of The Diesel Spotters Guide.[:)]

[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.

[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

[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]

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.

[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

[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.

[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.

[Mookie]

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

Mook

[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!

[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.

[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[:)]

[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[:)]

[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.

[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.

[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.[:)]

[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 !?!

[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]

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.

[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.

[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?

[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+ !?!

[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

[Randy Stahl]

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