284 AUTOGRAPHIC INSTRUMENTS USED IN FLYING-MACHINES. 



India-rubber had then to be interposed between the weight and the 

 winder, so that when the winder was in readiness to be released 

 by the starting-bolt, the weight was just clear of the ground. 



Diagram 2 shews the benefit derived from cutting off the 

 membrane of the wing near the wing socket. 



Diagram 3 shews the effect of altering the length of the 

 connecting rod. 



The pencil of the pendulum chronograph is adjusted so that it 

 is just clear of the paper on the indicator drum when the bob is 

 hanging vertically ; a number of timed trials determine the mean 

 period of the oscillations. 



By connecting the chronograph and putting on the wing of C, 

 which is identical with that used on the 48-band machine in 

 Observations F & G, it is found that the crank shaft turns once 

 in "57 seconds, lOEbs. on the 5 inch winder being thought to be a 

 fair average of the strain on the actual machine, this gives 11*6 

 miles per hour as a mean speed for the two successful nights 

 of the 48-band machine (Observations F & G). 



Diagram 4 shews the effect of altering the proportions but not 

 the area of the wing — ■ 



A is 9-22 ins. x 9-22 ins. 

 B 7 x 12-5 



-° 55 ' 55 X X -° ° 55 



C „ 5 „ x 17-5 „ 

 and obviously C produces the most thrust. 



Diagram 5 shews the effect of moving the midrib to the forward 

 edge of the wing, bringing the torsional stress on the midrib into 

 play, and a very marked improvement is perceptible. 



Comparing the time of the revolution of the crank-shaft with 

 the midrib on the forward edge of the wing, that is *66 seconds, 

 with the time of revolution of the old-fashioned wing, that is 

 •57 seconds, we find that the long and narrow wing with square 

 tip offers most resistance, produces more thrust and flaps slower, 

 shewing that the tip is the most effective part of the wing, and 

 may be said to do nearly all the work. 



As to the amount of thrust produced by the wing, it may be 

 mentioned that when the wing is at half-stroke, it takes about 

 8 ozs. to draw the pencil as high up the diagram as the maximum 

 pressure shewn in Diag. 2, the weight of course being hung where 

 the indicator cord is attached to the midrib. 



Observation L in the table of comparison was made with 

 48-band machine No. 5. It is thought that if we compare this 

 observation with the mean of H, J, and K, the 63-3 per cent, 

 extra weight is cheaply carried the 34*3 percent, greater distance 

 by the expenditure of 128 per cent, more energy, when it is 

 considered that the area is only increased 7*7 per cent. The two 

 perspective sketches with table attached together with what 



