384 



L. HAR GRAVE. 



Fig. 2 b. 



scale drawing shows two views of the 

 first one I have made ; it was designed 

 to flap the four wings 120° for each 

 explosion. Numerous errors in the 

 strength and proportion of its various 

 parts cannot be altered without begin- 

 ning anew. The sketch shows the wing 

 arc had to be reduced to 90° to suit the 

 exhaust ports and compression space ; 

 it also shows how the main cranks and 

 spring cranks are arranged so that the 

 curve of the torque produced by the 

 spring tension, shall, when plotted on the theoretical 

 indicator diagram, fall about midway between the explosion 

 and compression lines. 



This is the cycle of events. The wings are moved several 

 times by hand to charge the crank chamber with mixture, 

 which flows on through the external pipe and inlet valve 

 to the compression space and cylinder. The hands are 

 then withdrawn from the wings, and the springs at once 

 flap the wings and in addition compress the cylinder full of 

 mixture into the compression space, and also recharge the 

 crank chamber. Contact is made, the compressed mixture 

 explodes driving down the piston, flapping the wings, stor- 

 ing power in the springs for the up stroke, and compressing 

 the mixture in the crank chamber. This is all, and it is 

 repeated till there is a miss-fire or the effects of bad work- 

 manship stop the engine. 



The small working model (Fig. 3) shows an adaptation 

 of means to ends, and is thought to be more significant 

 and convincing than the tabulated results of an elaborate 

 whirling machine would be at this particular juncture. You 

 nave seen here aeroplanes with absolutely no extensions fore 

 and aft of their canvas, that maintain automatic stability 



