Like the cam shaft, the crank is bored out from end to end with a propeller flange applied on a taper at one end of the shaft. A bearing is provided between each throw with an additional thrust bearing at the forward end of the shaft which may be arranged to take either the thrust or the pull of the propeller. Lubricating oil is applied to all the bearings under a pressure of twenty pounds per square inch, this pressure being maintained by a gear pump attached directly to the end of the cam shaft. The oil is transferred from the pump to the bearings through passages cast in the base, no piping being used. Oil enters the hollow crank shaft at the main bearings and is conducted through the arms to the connecting rod bearings. The oil flying from the crank shaft falls into the oil sump at the bottom of the case where it is cooled before being used again. A second gear pump in tandem with the first takes the oil from the sump and forces it through a filter into the tank. [Illustration: Fig. 43. Crank Shaft of Sturtevant Motor. ] [Illustration: Fig. 42. Crank Case of Sturtevant Motor. ] This system enables the use of a more efficient filter than with the suction type and eliminates any danger of its becoming clogged and stopping the oil supply, since, in the event of such an occurrence the pump would furnish sufficient pressure to burst the filter. However, the filter is particularly accessible and may be instantly removed for cleaning without disturbing the oil. The tank regularly fitted to the motor holds sufficient oil for three hours’ use. If the engine is required to operate for a longer time without opportunity for replenishing the oil supply, a larger tank can be used. As no oil is allowed to accumulate in the base with this system of lubrication, the motor can be operated continuously at an angle. Water circulation is maintained by a centrifugal pump of large capacity, the impeller of which is mounted directly on an extension of the crank shaft, eliminating the usual bearings and its grease cup. The ignition is provided by a high-tension Mea magneto, its special construction permitting the motor to be started under a retarded spark avoiding the danger of back kick from the propeller. The cylinder and all exposed parts are rendered absolutely weather-proof by means of a heavy coat of nickel plating. (54) The Rotating Cylinder Motor.