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 use a mechanical transmission to deliver the power output of gas turbines to the wheels. Owing to the difference in their speeds, this is technically challenging and so a mechanical transmission did not appear until ten years after the first electric transmissions. The first gas turbine-mechanical locomotive in the world, Class 040-GA-1 of 1,000 hp was built by Renault in 1952 and had a Pescara free-piston engine as a gas generator. It was followed by two further locomotives, Class 060-GA-1 of 2,400 hp in 1959–61. The Pescara gas generator in 040-GA-1 consisted of a horizontal, single cylinder, two-stroke diesel engine