NOTES ON FLYING-MACHINES. 



25 



Bicycles also show a racing speed of about 20 miles per hour, 

 but no record has been seen of what power produces this effect, 

 although a very simple apparatus could be made to record the 

 strain on the treadle at every point of its revolution. 



As no tabular statement of the resistances of flat surfaces 

 moving horizontally and set at a sharp angle to the direction of 

 motion were available, though doubtless such have been computed, 

 it was thought a few independent observations would throw some 

 light on this subject. A whirling machine of simple construction 

 was therefore made, capable of moving a plane of one square foot 

 area at various speeds and angles, with an indicator for recording 

 at once on the same diagram, the lifting power and horizontal 

 resistance. The radius of the circle the centre of the plane moved 

 in was 6 feet 2 J inches, and the speed was determined by counting 

 the revolutions made during one minute of each observation. 



Four sets of observations were made with the plane at angles 

 •of 5°, 10°, 15°, 20°, 25° with the horizon, the first of each set had 

 the full driving power on the whirling machine ; the second, third 

 and fourth had the speed reduced by taking off successively weights 

 of 16, 34 and 52 pounds from the full driving weight. 



The scale of the diagrams was carefully determined by a balance 

 in the form of a cross, which was clamped to the arm carrying the 

 indicator and plane, so that weights in the pans on the horizontal 

 beam of the balance, either lifted or displaced horizontally the 

 centre of the plane. 



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