282 



AUTOGRAPHIC INSTRUMENTS USED IN THE 

 DEVELOPMENT OF FLYING-MACHINES. 



By Lawrence Hargrave. 



[Bead before the Royal Society of N.S.W., December 7, 1887.'] 



The result obtained by Machine C described in June last, 

 rendered the construction of a 48-band machine justifiable ; the 

 first one of this power met with continued disaster until the ninth 

 trial when it became a total wreck. The second 48-band machine 

 (Figs. 3 & 4) was more successful, and its work (Observations 

 F & G) is comparable with C ; A, and B, being considered 

 obsolete types. 



A small vertical plane is now attached over the after end of 

 the strut, to counteract the effect of imperfections that have a 

 tendency to make the machines turn to one side.* 



H, J, and K are three very similar observations made with a 

 square-bodied machine of large area (Fig. 5) after experimenting 

 with the wing comparing apparatus (Fig. 6). 



It was found necessary to invent a contrivance to test the 

 work done by a number of elastic bands arranged with different 

 purchases, to see if there was any great loss by friction as the 

 cord passed over 4 or 8 sheaves, and to construct a more accurate 

 curve of strains on the cord than that previously used. Fig. 1 

 shews a plan of the apparatus used and facsimiles of the diagrams 

 taken. A solid model of the strut of the 48-band machine is 

 screwed down on a table, with the india-rubbers, blocks, sheaves 

 and cord used in the actual machine : the standing part of the 

 cord, instead of being fastened to the tail end of the strut, is 

 fastened to a barrel with a winch handle ; the other end of the 

 •cord, instead of being secured to the winder is attached to a lever 

 and spring balance, a glass pen on the end of the lever draws the 

 diagram, the indicator drum being rotated by a small weight 

 that descends as the india-rubbers are stretched towards the tail 

 by turning the winch. The bands on each side of the strut are 

 observed to be equally stretched. 



It is thought that the space between the stretching and 

 •contracting curve partly represents the loss by friction of pulleys, 

 and partly a quality of the india-rubber that prevents it giving 



* Since rejected as useless. 



