The gas turbine locomotive was a follow-up of the rather unsuccessful steam turbine design. Also known as GTELs (which was short for gas turbine-electric locomotives) the Union Pacific was the only Class I railroad to use the design in regular service operating a small fleet of 55 successfully for more than 20 years. As with steam, the petroleum version of the turbine locomotive was highly inefficient in terms of its fuel usage. However, at the time the UP employed its fleet petrol was cheap, which made the gas turbines relatively inexpensive to operate and actually quite efficient due to their phenomenal horsepower and tractive effort. As oil prices rose the UP's gas turbine locomotives became less and less efficient to the point that all were off of the roster by 1970.
The gas turbine locomotive functions quite similarly to a standard diesel-electric except instead of a traditional diesel engine a turbine is used instead (specifically a turboshaft engine which powered the on-board generator). The mechanics of diesel locomotives are rather straightforward, although it is commonly mistaken that the diesel engine itself propels the locomotive, which is not the case. While the diesel engine is the prime mover the energy it creates drives an electrical generator, which in turn drives the traction motors found within the locomotive’s trucks that actually turns the wheels (or the mounts which sit over the axles) and propels unit forward. The diesel engine itself has no connection to the actual motion of the wheels and in essence the locomotive is an electric locomotive which carries its own power source on board.
As from the Union Pacific, no other main line railroad elected to use a GTEL on the basis of fuel economics. However, in 1950 Westinghouse developed a gas turbine locomotive for testing known as the "Blue Goose." This experimental, #4000, produced 4,000 horsepower and carried a B-B-B-B wheel arrangement. It tested on Chicago & North Western, Katy, and Pennsylvania railroads but ultimately none chose to use the design (the PRR had just recently scrapped an unsuccessful steam turbine design in the late 1940s). As for the Union Pacific, because of its region of operations and hunger for powerful locomotives the gas turbine design fit quite nicely on its system. The first test model was #50, built as a partnership between General Electric and the American Locomotive Company (Alco) in 1948. While never owned by the railroad it was tested throughout 1949 on the UP system. The GTEL carried a B+B-B+B wheel arrangement and could produce a hefty 4,500 horsepower. It carried a carbody design resembling an Alco FA diesel locomotive, obviously due to that company being one of the GTEL's manufacturers.
In general turbine locomotives are more efficient than standard reciprocating steam or diesel-electric designs due to fewer moving parts thus, in theory, they are supposed to be easier to maintain. However, their significant drawback is that they require high speeds to achieve maximum efficiency, which simply wasn't practical on most railroads. In the case of the steam turbine it also was prone to a myriad of mechanical issues and the design was scrapped across every railroad which tested it after just a few years of operation. The gas turbine locomotive did not suffer from serious mechanical issues but its heavy fuel consumption caused most railroads to shy away from it. In the case of the Union Pacific it determined that its relatively straight and flat main lines would allow for the model to retain high speeds while also being able to operate it relatively cheaply.
This was because the fuel used, "Bunker C" oil (a heavy, viscus substance), was inexpensive at the time. The first order of UP's GE/Alco-built gas turbine locomotives were numbered 51-60, arrived in 1952, and carried specifications identical to the test model #50. The UP intended to use them west of Salt Lake City in conjunction with the Southern Pacific but the locomotives were so loud, due to their turbines, that most California cities outlawed them. Because of this, the GTELs were generally used between Council Bluffs, Iowa and Ogden, Utah. Union Pacific's second order of gas turbine locomotives arrived in 1954. Numbered 61-74 these models were virtually identical to the original save for that they carried much larger 24,000 fuel tenders (the original ten carried just 7,200-gallon tenders although this was later upgraded to 24,000 as well). The most significant develop occurring with the "second generation" GTELs was that Union Pacific began successfully MU'ing them (meaning the trailing units could be controlled from the lead locomotive), although only nineteen were actually coupled this way. To see a cutaway drawing of the locomotive please click here.
UP's final order of gas turbine locomotives were numbered 1-30 and were quite different from the original 25. They carried a C-C+C-C wheel arrangement and featured two, semi-permanently coupled units enabling a single unit to produce an incredible 8,500 horsepower. These final thirty GTELs were nicknamed "Big Blows" for the incredible noise they produced, even louder than the first 25 models (which was partly due to the fact that each unit included two turbines). As the 1960s waned fueling the gas turbine locomotive became an increasingly expensive proposition for Union Pacific as demand for "Bunker C" increased and oil prices rose. With cheap fuel no longer available Union Pacific slowly began to retire their legendary fleet of GTELs and all were silenced by 1970. Today, two of the gas turbines remain preserved, #18 at the Illinois Railway Museum and #26/26B at Ogden Union Station in Ogden, Utah.