The Lift of Aeroplanes.

Progress, Volume IV, Issue 2, 1 December 1908, Page 55

The Lift of Aeroplanes.

Draw a right-angled triangle, denoting the base by A C and the verticle height by BC. The angle B A C is then the inclination of the plane to the line of flight in still air, and the height B C corresponds to the pitch of a screw. Suppose we assume BGto be one-fourth of A C, say 1 foot and 4 feet respectively ; the plane will then move the air downwards 1 foot for every 4 feet of travel. Assume the speed to be 44 feet per second; in one second therefore the air will be moved 44/4 =11 feet. V, the acceleration, therefore equals 11 feet per second. The total quantity of air moved per second is found by taking the sum of the lengths of all the leading edges of the planes. This sum multiplied by the distance moved m one second and by 0.08 and by Fwill give us the weight of air moved, and this weight multiplied by V and divided by 32 (q) will give the thrust, or lift, in pounds. If S - speed per second m feet on the line of flight, P the pitch = A CIB C and V the acceleration = S/P, and L = length of the leading edges, we may write the formula as 0.08 L S F2/32F 2 /32 = the lift in pounds. In Farman's case the speed 8 was 45 feee per second, L equaled about 96 feet — we do not know what Fwas, but assume it to be 10 feet— we get lift or thrust T=96x 45 x 10 2 y 0.08/32 = 1,080 pounds. It was actually 1,100 or thereabout.— Prof. Rankin Kennedy, in Engineering.

Aldus Manutius, a famous fifteenth century Venetian printer, had in his office a black boy, purchased from a corsair. The ait of book production was at first so little understood as to be asciibed to Satan. The suspicion that the Evil One had something to do with the new art was intensified in Venice by the presence in the office of Maimtius of his black servant. So strong was the feeling that there was grave danger of his place being wiecked by the rabble. Thereupon Aldus declared that any person not satisfied that the boy was flesh and blood could come and pinch him to make sure. The mistaken impression was thus lenioved; but befoio this time the name ' ' Printer 's Devil had been attached to the boy, and has lived ever since as the nickname of the lad in a printing office.