General Motors Electro-Motive Division GP series
The General Motors GP (General Purpose) series of locomotives are four axled locomotives were built by EMD in America and GMDD in Canada. It was originally intended as a flexible design that easily lent itself to a variety of different purposes and uses. They were offered alongside the SD-series of 6-axle units and the SC/SW-series of switcher locomotives.
- GP7 - 1949-1954
The GP7 family (featuring the cabless GP7 booster) was meant as a more versatile, rough-and-tumble package than the carbody-styled F7 family. Powered by the EMD 16-cylinder 567B engine, GP7's were rated at 1500hp.
- GP9 - 1954-1963
The GP9 family was the road-switcher version of the F9 family. There were virtually no internal or external differences from the prior model, the only major difference being an improvement of the 567C engine to 1750hp.
- GP20 - 1959-1962
Much as the GP7 and GP9 before, the GP18 and GP20 were offered as a pairing, with the GP20 and it's 2000hp 16-cylinder 567D2 being offered as the premium model of the two. Although the GP18 only put out 50 more horsepower (1800hp from a 16-cylinder 567C1 engine) than the GP9, because it was equipped with a turbo-supercharger it was a lot more fuel efficient and was able to efficiently operate at far higher altitudes. Visually similar to the previous models, the major spotting difference between the two is the paired radiator fans (36" and 48") at the back of the long hood of the GP20, and only one (48") on later GP18's (and later GP9's which were still offered at this time).
- GP30 - 1961-1963
The GP30 signified yet another minor step in the evolution of EMD's 4-axle locomotive designs, if only mechanically. Originally to be named the GP22 (due to its 2250hp), it's 16-cylinder 567D3 was now housed in a filtered and pressurized carbody, which allowed for a cleaner, and better, working environment. It also featured a single radiator bank mounted at the back of the carbody, rather than the smaller banks fore and aft.
Visually, the GP30 was very different than anything else that came out of the EMD catalogues. The roofline of the center of the cab and carbody blended into each other, with a pair of bulges that flanked the one dynamic brake fan (if so equipped). The cab itself did not blend with the center of the cab, each rounded with a step in between.
- GP35 - 1963-1966
The GP35 would prove to be the evolutionary end for the venerable 567 design, which traced it's life all the way back to Winton's pioneering 201A design of 1936. It would also feature many firsts of EMD's later designs, mainly the availablity of a lower-horsepower, roots blower equipped version (the 16V-567D-equipped 1800hp GP28) as well as the change to the modern, angular carbody design that EMD used until the end of GP60 production.
The GP35 was powered by a 16-cylinder 567D3A putting out 2500hp.
- GP40 - 1965-1971
The GP40 was the first EMD 4-axle family to use the then newly-developed 645 platform. It was available in 16-cylinder roots blower-equipped (GP38, 16V-645E, 2000hp) and 12-cylinder turbocharged (GP39, 12V-645E3, 2300hp) as well as the 3000hp base model. Towards the end of production, EMD offered an AC-transmission option on all of the models, with the notation "DC" being added to the model name for generator-equipped units and "AC" added to alternator-equipped units.
- GP40-2 - 1972-1986
The GP40-2 family was nothing if visually disappointing when it was announced. Virtually identical to its predecessor units outside, it nevertheless presented a huge step in the evolution of locomotive design at EMD. Some of the improvements included: -New truck design that improved adheasion -Modularized and solid-state control circuitry that was easily replaced if a part failed, and was more robust than previous designs -Bolted battery box covers that wouldn't come loose -Longer rear traction motor duct that was more effective at cooling the rear traction motors -Long-range dynamic braking -Improved design central air intake filters and radiator screens
Despite all these changes, the writing was on the wall - the railroads were running longer and heavier trains, and the GP40-2's stablemate, the SD40-2, outsold it 4-1.
- GP50 - 1980-1985
With the GP50 family EMD quietly retired the Dash-2 moniker that they thought up 8 years previous, but other than that there wasn't much in terms of improvements over the GP40-2. Sure, radar-equipped wheelslip control, and there was another 500hp available - at least until the failures began to roll in. It seemed that the venerable 645 design simply couldn't be pushed to the 3500hp required of the GP50 design, and many railroads responded by derating their GP50's to 3000hp and either going back to purchasing GP40-2's or by not buying EMD products at all. Although EMD later sorted out the issues with the 645F3 and pushed the design to 3600hp in 1984, but it was too late, and GE by this point had taken the position as the largest-selling locomotive manufacturer in North America.
Much as before, the GP50 was available in a 12-cylinder version, the GP49 (2800hp), but for the first time a roots blower-equipped model wasn't catalogued.
- GP60 - 1985-1994
Realizing that the GP50 was not going to win back market share, the EMD rushed the development of its replacement powerplant, and in 1985 announced the GP60. Almost identical in appearance and performance, it's major advantage was use of the 3800hp 16-cylinder 710G3, its greatly improved reliability and its reduced fuel consumption. It also brought EMD kicking and screaming into the computer age: each unit was equipped with a host of microprocessors which did everything from monitor wheel slip and engine speed to making sure that the headlights weren't burnt out. While it did win back some orders for EMD but it was obvious that there was to be no upgrade past the GP60, and in late 1994 it was quietly removed from the catalogue.
Once again a 12-cylinder variation was available (GP59, 3000hp) and while it did better than the GP49 it still only sold about 36 units.