Gas turbine on and off to run it only at high efficiency. The emergence of the continuously variable transmission may also alleviate the responsiveness problem. Turbines have historically been more expensive to produce than piston engines, though this is partly because piston engines have been mass-produced in huge quantities for decades, while small gas turbine engines are rarities; however, turbines are mass-produced in the closely related form of the turbocharger. The turbocharger is basically a compact and simple free shaft radial gas turbine which is driven by the piston engine's exhaust gas. The centripetal turbine wheel drives a centrifugal compressor wheel through
Gas turbine locomotive early 1970s (ETG and RTG) and were used extensively up to about 2000. SNCF (French National Railways) used a number of gas-turbine trainsets, called the Turbotrain, in non-electrified territory. These typically consisted of a power car at each end with three cars between them. Turbotrain was in use up until 2005. After retirement, 4 sets were sold for further use in Iran. In the 1940s and 1950s research was conducted, in both the US and UK, aimed at building gas turbine locomotives which could run on pulverized coal. The main problem was to avoid erosion of the turbine blades by