This unit was the last Geep that EMD built, I believe around 12-1993. My question is why did they discontinue the 4-axle GP series? Is it because of the HTCR trucks that EMD made for the SDs that might enable them to run on track radius that were the domain of the 4-axle units? Does it have to do with horsepower numbers coming up and exceeding the capability of 4-axle units re: adhesion?
I always thought the GP60 stood out due to the large dynamic brake housing (phase II looks rather boxy).
If railroads expressed an interest, would EMD bring the 4-axle Geep back?
you answered your own questions with the questions you asked…
steerable trucks, too much power/not enough axles. everything seems to move in heavy unit trains anymore and there aren’t many rickety branch lines around these days.
Check the thread index – this was exhaustively discussed on at least two prior occasions, with good answers.
Plenty of ‘rickety branch lines’ (and other customers for 4-axle power) around – but also, plenty of war-weary 4-axle power from previous generations that gets the job done just fine at an appropriately deep-discounted price. EMD even tried their own ‘factory-rebuild’ program in the early '90s to get in on the “used” equipment market that all-new power wouldn’t likely penetrate… and even THAT was ‘too expensive’.
Railroads willing to pay for a 4-axle “Geep” could easily get one – a modified F59 design from EMD, or something from a builder like Alstom with an EMD engine and more modern trucks (cf NJT P42AC). Not much point in today’s operating world, though…
I’m sure EMD would build it if someone with the money wanted some. It would just have to be a worth while amount. Not often that a business says no when someone waves money at them.
Didn’t GE do a rebuild program too? I seem to remember some funny looking B23-7 rebuilds.
The Super-7 series was designed as a rebuild similar to the BL20-2. Aside from a few demonstrators, only a handful were built for Monongahela and Roberval & Saguenay and a fair number were sold to NdeM as kits to be assembled in Mexico.
Yeah that’s what I was talking about, thanks CSS I didn’t remember what they were called. These rebuilds sounded like a good idea, did they just cost more then people thought was worth?
The problem of horsepower overpowering 4 axle units goes back to the original GP40s. Before then locomotives didn’t always produce enough power for 6 axles. SD7 and SD9s, even SD38s had relatively little horsepower per axle, which is why they were usually geared low and used more as a specialty engine, notably hump units for the SD38. As Overmod said, the older units get the job done for anything that still needs 4 axles, such as branch lines. One wonders how the New York Central would have coped in modern times, they only ordered 4 axle power!
Hey, that reminds me of a question I thought of a week or so ago… EMD produced the GP20 and the SD24 at the same time. The GP20 had 2000hp, while the SD24 had 2400hp, which was unmatched in a four-axle until the GP35 (2500hp) came along. Why didn’t the GP20 and GP30 have higher horsepower? Did any railroad experiment with uprating a GP20? I know Alaska uprated their GP30 to 2500hp, but many railroads went the other way, derating their GP35s to 2250hp.
I think the differential in horsepower 'tween the GP20 and SD24 was because of traction motors. Both were equipped with D47s, and I’ve been told that 500 HP per axle was it’s limit, so that puts the GP20 400 HP below the SD24. Remember that EMD knowing this, was hesitant to even offer the GP20. At 250 HP over a GP9, EMD did not believe the HP increase was worth the price of adding a turbocharger. The first SD24 (EMD order#5579) was built in July of '58, while the first production GP20s went to the Western Pacific in November of '59, only after seeing that the turbocharged GP9s of Union Pacific were successful. RPM ratings in the different versions of the 567 were also a major reason the HP went up. Almost all of EMDs model evolutions came with a prime mover that operated at a higher RPM than its predicessor, upgraded traction motors, and ugraded main generators. A plateau was inevitably reached, and then a new upgrated line of 645 engined models came out in 1966. Same basic thing occured 19 years later with the GP50/SD50 series.
As far as why some upgrade while others downgraded, that’s a whole other topic. Some derated for fuel economy. Mopac deturbocharged their GP35s to ease maint. costs. SP had SD45s running around with 3600, 3400, and 3200 HP ratings.
Another issue here may be simply the weight of the GP60 locomotive exceeding the load capacity of the track. I seem to recall reading that the Santa Fe GP60 never filled its fuel tanks due to the weight limitation. Discussion elsewhere in this forum mention 80 tons as the maximum limit for 4-wheel Freight Cars.
By comparison, The PRR SD45 weighed 389,000. If this weight was carried on a 4-axle locomotive, the axle weight would exceed the 80,000 lb axle limit that only PRR and C&O imposed on their steam engines.
And if I remember correctly the weight of a locomotve has a direct and important effect on it’s tractive effort and how much it can pull and lug over grades. So then the question becomes “Are B-B units vaiable with todays technology?” I would say yes, but you have to move away from the traditional belief in heavier more horsepower units. I was always told there were certain things B-B units were better at. Yes they are preferred on branchlines because they are easier on the track. But I was also taught that they were better at expidited trains, things that need to move fast. Intermodel, perisables etc. But not on bulk things like coal and grain.
So, it would seem the GP40 was the best for weight, horsepower could be an arguement as to weather the GP50/60 was a major or minor improvement. So I would suggest a concentration on efficency. A 12 cylinder version of the SD70ace’s engine could probably put out 3200hp, add in all the new traction control and fuel use monitoring systems, ballast it to at least GP40 weight and you would have an awesome fuel miser that could be a great little hostler.
The reason that the Santa Fe did not fill the tanks on the GP60M was the fact that the wide cab made the unit to heavy with full tanks. Santa Fe orginally wanted cowled units like the F45 and they were to heavy in the design study. EMD said we can make them but they will have titatuim bodys on them. That alone made them cost prohibative. Santa Fe was very happy with the 60M and then the 60B that came along next. Yes there will always be a need for a 4 axle light weight locomotive. Sooner or later someone will come up with the next branchline locomotive.
Hindsight is always 20/20, but lookin’ back it’s still a bit fuzzy [}:)][#dots] Seriously though, the GP50s and 60s made sense to the way of thinking at the time – higher horsepower, better electronics – and the railroads that bought those engines seemed to concur, until design limitations began to present themselves, anyway. But even the GP40s were known to be “slippery”, which was likely a driving force behind EMD’s development of wheelslip controls.
With current technology, a GP40 equivalent would seem to be an excellent model offering, however, the market seems to want increasing numbers of GP38 equivalents – rebuilds! These (and the original GP38s and -2s) seem to have displaced most of the traditional switcher models in railroad yards and local service, though both higher- and lower-horsepower models also seem to be used interchangeably. And there are still plenty of potential GP38s out there, especially with all the GP50s that are nearing the end of their original useful lives. I’m curious as to what will happen to GP60s when their time comes: Will they trade their 710s for 645s, or just be reworked as GP…58s? Time will tell.
BTW, if I’m not mistaken, the current SD70 models already have 12 cylinders, don’t they? And producing 4300 hp? So going with an 8 (!)-cylinder engine would probably produce right around 3000hp, and with all that modern technology… WHOA! Now all they’d need to do is put it on HT-B trucks… [:o)]
It’s starting to happen with the GP50’s but I wouldn’t be too surprised if the various GP40/50/60’s and B23/30-7’s also begin providing underframes for Railpower, MPI and NRE for their new locomotives; gen-sets, Green Goats, MP20-3’s, etc.