shaft drove a three-bladed screw propeller that was in diameter. They suffered from severe cavitation at speed. The single semi-balanced rudder was chosen to reduce high speed resistance. It had an area of only and was moved by a weak steam-driven servomotor. On trials, the turning circle was measured at at . In service it took 25–30 seconds to turn the rudder to its maximum 32° at speed and the ship's turning circle was approximately double that demonstrated on trials. The ships were so unhandy that the captain of the Volta cautioned in his log that "great care was needed when operating in company with the battleship Strasbourg, because the latter ship was far more maneuverable." The Mogador-class ships were designed for a speed of , but this was comfortably exceeded on trials when Mogador achieved a top speed of from for one hour. This was at "Washington" standard displacement so her earlier performance of with at a load displacement of was even more impressive. At normal displacement they carried only of oil, but carried of oil at normal load and at deep load. Endurance was estimated during their trials at at a speed of using the cruise turbines and at a speed of with the main turbines. This was never attained during service because the consumption by the auxiliary machinery was underestimated. Arguably the greatest weakness of these ships lay in their inability to generate sufficient electric current to power the multitude of auxiliary motors on which their advanced machinery and complex gun mountings were dependent. Their DC electrical supply was only 115 V, whereas larger cruisers with power-operated turrets had a 230 V system. Electrical power was generated by two Alsthom turbo-generators rated at only 120 kW with two small diesel generators rated at 44/52 kW for use when the ship was alongside. The latter provided only for the ship's minimum lighting and electricity needs, and fires had to be lit in at least one of the boilers in order to train the turrets or elevate the guns for practice or maintenance. Many of the auxiliary motors themselves were also seriously underpowered, particularly the servomotors for the gun mountings (which were slow to train and elevate) and for the rudder which contributed to the ship's poor maneuverability. In technological terms Mogador and Volta were ships with the armament of a light cruiser in the hull of a destroyer;