The water circulation is by centrifugal pump, which is mounted at the lower end of the vertical shaft. The water is pumped through brass pipes to the lower end of the cylinder water jackets and leaves the upper end of the jackets just above the exhaust valves. The lubricating system is one of the main features of the engines, being designed to work with the motor at any angle. The oil is carried in the sump, from where it is taken by the oil circulating pump through a strainer and forced through a header, extending the full length of the crank-case, and distributed to the main bearings. From the main bearings it is forced through the hollow crank-shaft to the connecting rod big ends and then through tubes on the rods to wrist-pins and pistons. Another lead takes oil from the main header to the cam-shaft bearings. The oil forced out of the ends of the cam-shaft bearings fills pockets under the cams and in the cam rocker levers. The excess flows back through pipes and through the train of gears to the crank-case. A strainer is fitted at each end of the crank-case, through which the oil is drawn by separate pumps and returned to the sump. Either one of these pumps is large enough to take care of all of the return oil, so that the operation is perfect whether the motor is inclined up or down. No splash is used in the crank-case, the system being a full force feed. An oil level indicator is provided, showing the amount of oil in the sump at all times. The oil pressure in these motors is carried at ten pounds, a relief valve being fitted to hold the pressure constant.
Fig. 240.—Power, Torque and Efficiency Curves of Wisconsin Aviation Motor.
Ignition is by two Bosch magnetos, each on a separate set of plugs fired simultaneously on opposite sides of the cylinders. Should one magneto fail, the other would still run the engine at only a slight loss in power. The Zenith double carburetor is used, three cylinders being supplied by each carburetor. This insures a higher volumetric efficiency, which means more power, as there is no overlapping of inlet valves whatever by this arrangement. All parts of these motors are very accessible. The water and oil pumps, carburetors, magnetos, oil strainer or other parts can be removed without disturbing other parts. The lower crank-case can be removed for inspection or adjustment of bearings, as the crank-shaft and bearing caps are carried by the upper half. The motor supporting lugs are also part of the upper crank-case.
Fig. 241.—Timing Diagram, Wisconsin Aviation Engine.
The six-cylinder motor, without carburetors or magnetos, weighs 547 pounds. With carburetor and magnetos, the weight is 600 pounds. The weight of cooling water in the motor is 38 pounds. The sump will carry 4 gallons of oil, or about 28 pounds. A radiator can be furnished suitable for the motor, weighing 50 pounds. This radiator will hold 3 gallons of water or about 25 pounds. The motor will drive a two-blade, 8 feet diameter by 6.25 feet pitch Paragon propeller 1400 revolutions per minute, developing 148 horse-power. The weight of this propeller is 42 pounds. This makes a total weight of motor, complete with propeller, radiator filled with water, but without lubricating oil, 755 pounds, or about 5.1 pounds per horse-power for complete power plant. The fuel consumption is .5 pound per horse-power per hour. The lubricating oil consumption is .0175 pound per horse-power per hour, or a total of 2.6 pounds per hour at 1400 revolutions per minute. This would make the weight of fuel and oil, per hour’s run at full power at 1400 revolutions per minute, 76.6 pounds.