jeaton01
I believe the train engines were steam turbines, Don.
Actually ships were the first to use turbines over pistons, and that change was about 1910-1920. However, the naval steam turbines needed significant (read heavy) reduction gear to get to the low RPM needed at the shafts of ships.
The reciprocating driving arms for train locomotives was highly mature. It also defined how periodic maintenance was done, too. The "final drive" on steam locomotives was all on the outboard side of the driving wheels. To have gone to shaft-driven wheels, the axle, and all the needed differentials would have to be between the wheels. A realitively inaccessible area. Also one subject to a lot of heat.
So, until electric final drive motors wer introduced, there was no reason to change from the single expansion piston used. (There were experiements to double-expansion pistons, but they just added complexity for little gain.)
UP's gas turbine locos just drove a generator, which gave them electric power to pass to the trucks. They were supremely loud, and not terribly fuel efficient, for the horsepower delivered to the generator. Now, they had fewer parts than the V-12 and V-18 diesels. But the diesels idled better, were more familiar to the maintenance sheds & crews.
Getting an aviation-weight/efficient turbine would wait for Whittle (and his competitor over at Heinkle) in 1938. And, even then, they did not have enough practical knowledge, acquired from use, to know just how much horsepower the power turbine could actually generate. So, the early turbines just had inefficient compressor sections.