124 



KNOWLEDGE & SCIENTIFIC NEWS. 



I June, 1905. 



flap. The top sprocket of second motion can be raised 

 or lowered for altering the limiting positions jai the 

 wings (i.e., the position of the arc). The lower end 

 of the connecting rod actuates the inner ends of the 

 levers for wagging the wings by a simple device of two 

 oscillating roller-carrying links attached to the cross 

 head, whose pin is constrained by vertical guides. 



To the brackets, seen below the wings, are attached 

 " pectoral cords " of elastic. These store up energy 

 on the up stroke, and so obviate too violent alternations 

 of load on the driving mechanism. 



The motor is a nominal 3 to 3^ h.p. petrol cycle- 

 engine. 



The wings are at present arranged to flap 100 times 

 a minute, which is, of course, considerably less than 



powerful sweep of the wings. The spring balance 

 reading is here obviously fallacious so far as register- 

 ing the lift goes, because the rope is pulling the machine 

 back. However, at the rough tests so far made, the 

 balance shows a diminution of reading of 80 and 160 

 lbs. at the down stroke when the machine springs up- 

 wards but also forwards. 



.\t the preliminary trial already made the wings de- 

 scribed a diminished angle to that of the No. i model. 



It should be noted that with this angle and 100 flaps 

 per minute the wings appear capable of evoking a 

 resistance of about 100 lbs. each, and the machine is 

 raised about two feet at each stroke. It is difficult at 

 present to form a correct idea of the position of centre 

 of pressure, but we think that it goes through an arc of 



Fig- 3 



proportionately corresponding to the increased area 

 and h.p. But increased area does not imply propor- 

 tionajly increased resistance. 



The machine has been suspended from a tree bough, 

 and the wings flapped under power. The results are 

 very promising. .At each down stroke the whole 

 machine, apart from the carriage, weighing 232 lbs., 

 is lifted up bfjdily into the air and forwards. It rises 

 about two feet each stroke. It looks just like a gigan- 

 tic bird trying to fly under similar conditions. At the 

 down strokes the suspending rope leaves the vertical 

 and becomes markedly inclined. The pull on the rope 

 then pulls the machine back, so that even if it be 

 capable of flight it cannot fly under these conditions. 

 At the down stroke it seems that, if the rope were then 

 severed, the machine would travel up and away with the 



2.25 feet on the down stroke. 



In the model, which is susceptible of considerable 

 lightening, we have nearly 33 square inches per lb. 



There arc grounds for believing that a feathered wing 

 made of a number of units can exert a greater resist- 

 ance than a simple wing; such as that of the insect or 

 bat type, or the various simple mechanical wings which 

 have been hitherto used in wing flapping machines. 

 There are experimental grounds for believing that re- 

 sistance is more dependent on periphery of an aeroplane 

 than on its superficial extent. 



Furthermore, the primary feathers must certainly 

 act as a series of stepped aeroplanes, each acting on 

 air from a different level which has no/ had a downward 

 velocity imparted to it by having had to sustain the 

 weight of a previously acting supporting surface. 



