. American engineer and railroad journal . amount of power required to run the motors, with propellersattached, was calculated by the formuhc given above. The difference between these last values and the figures pre-viously obtained when running the motors light at the same Vol. LXIX. No. 5.] AND RAILROAD JOURNAL. ^43 speeds gave the net *. required for the propellers the same time the throat l< was measured for the same ratesof speed. From these data a comparison of the efficiencies ofdifferent types was readily made, A summary of the results obtained is given In the followin
. American engineer and railroad journal . amount of power required to run the motors, with propellersattached, was calculated by the formuhc given above. The difference between these last values and the figures pre-viously obtained when running the motors light at the same Vol. LXIX. No. 5.] AND RAILROAD JOURNAL. ^43 speeds gave the net *. required for the propellers the same time the throat l< was measured for the same ratesof speed. From these data a comparison of the efficiencies ofdifferent types was readily made, A summary of the results obtained is given In the followingtable: In this table K = axial thrust in kilograms, F = total area of propeller blades in square metres,and U = energy absorbed per second in metre kilograms. j ■//Jmm////////^///m /////////////,. and the velocities given refer to the centre of gyration of eachblade, or that point whose distance from the axis of revolutionis equal to the radius of gyration. TABLE I. Velocity per Sec. of the Centre of Gyration. Type 1 Type 2 Type 3—2 bladesType 3—1 blades Type 4 Type 5 A Values of —,F .e., Axial Thrust in Kilo-gram* Produced by 1Square Metre of BladeSurface. 5 m. 10 m. 15 m. 20 m ( , 61 14. SI) u Values of —,A , Power in Meter Kilo-grams per Second Re-quired to Produce 1Kilogram of AxialThrust. 5 m. 10 m. 15 ill. 20 m GO This table enables us to calculate the amount of thrust ob-tainable from propellers of different sizes by the expenditureof 1 , and to see at a glance which are the most efficientshapes. We are also able to discard certain types tested
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectrailroadengineering
