1,190,635. Clutches, preventing shocks in; shaft couplings. PRVNI BRNENSKA STROJIRNA, ZAVODY KLEMENTA GOTTWALDA, NARODNI PODNIK. 24 Aug., 1967, No. 39033/67. Headings F2C and F2 U. In turning gear for slowly turning the rotor of a large steam or gas turbine while it cools after shut down, the hub of a clutch member 4 is connected to a shaft 1 by a torsionally resilient coupling wherein feather keys 2 in the shaft 1 engage slots 3 in the hub which are substantially wider circumferentially than the keys, a leaf spring 5 urging the hub angularly relative to the shaft to hold the keys 2 against one side of the slots 3 when the coupling is unloaded. The clutch is situated between the turning gear and the rotor and may be a magnetically engaged positive clutch as shown, or a free-wheel clutch. The turbine rotor is allowed to come to rest, and is then restarted by a turning motor having a flywheel in its drive train, the motor and flywheel being run up to speed, with the clutch engaged, in the time taken to take up the lost motion in the coupling.