52 LAWRENCE HARGRAVE. 



ON A COMPRESSED-AIR FLYING-MACHINE. 

 By Lawrence Hargrave. 



[With Three Diagrams.] 



[Read before the Royal Society, N.S.W., June 4,1890.~] 



Considerable satisfaction is felt in recording a material advance 

 since August 1889, in the development of the detail of flying- 

 machines, and in the direct proof by experiment that yet another 

 form of apparatus flies with ease. The principle embodied in this 

 experiment is that of Borelli, published in 1680, and it doubtless 

 has had many staunch advocates in later times ; but the writer 

 maintains that this is the first practical demonstration that a 

 machine can, and does fly by the simple flapping of wings ; the 

 feathering, tilting, twisting, trochoiding, or whatever it be called, 

 being solely effected by torsional stress on the wing arm. 



The combination of Borelli's views with the results of work 

 recorded in your proceedings has swept away such a mass of tackle 

 from the machine that its construction becomes a ridiculously 

 simple matter. The engine of the model of course retains its 

 position as the most important part, and by continuous effort the 

 number of pieces and the difficulties of construction have been so 

 reduced that it is possible to make them by the gross at a cost that 

 cannot exceed five shillings each. Eor instance the cylinder, usually 

 the most expensive portion of an engine can be produced with the 

 ease and celerity of a jam-tin. The importance of this cheapness 

 of manufacture may be realized w T hen we consider that there must 

 be many young mechanics who would willingly work at this branch 

 of engineering, but for the difficulty of procuring or making a 

 light and powerful motor ; such objection cannot now be made as 

 herewith you have drawings showing the relative dimensions of a 

 proved successful machine, and it surely will not be a laborious 

 job to make others of greater range and power. 



As to the efficiency or rather the absence of it in this engine, 

 let us take the centre of effort of the wings at two feei from the 

 fulcrum ; their total area is 1*5 square feet, and supposing from 

 the indicator diagram that as many as forty double vibrations 

 were made in twenty seconds, it is clear that a little over 300 

 foot-pounds is all the flapping power used to drive a machine 

 weighing 2 '53 pounds a distance of 368 feet horizontally in a dead 

 calm. Regarding the theoretical foot-pounds of work in the 144*6 

 cubic inches of air at 230Ibs pressure. Mr. Arthur Pollock of 

 the Physical Laboratory at the University has ascertained for the 



