An electric motor supplied with a speed control voltage from a control 12 is connected to a flywheel 1 and drives the slide of a press through a clutch. A tachometer generator 24 coupled to the flywheel supplies to a speed meter 28 by way of a potentiometer 30 and relay contacts 32 a voltage indicative of the speed of the flywheel. Contacts 32 are open when the clutch is not energised and potentiometer 30 modifies the voltage supplied to the meter 28 to cause the meter to indicate a pre-set normal running speed of the press even though the flywheel is running at a speed higher than the said normal running speed. A second potentiometer 22 and relay contacts 20 which are closed when the clutch is not energised modifies the speed control voltage in such a way as to cause the flywheel to be driven at a higher than normal speed when the clutch is not energised but to be driven at its normal speed when the clutch is energised and the contacts 22 are opened. The meter 28 thus indicates normal running speed both during the over speed period when the clutch is de-energised and also when the speed falls as soon as the clutch is energised.