24 NOTES ON FLYINGtMACHINES. 



Fig. 5 is the best card of the six from which Fig. 4 was 

 constructed. 



To arrive at the interpretation of these diagrams with an 

 accuracy corresponding to the roughness of the whole experiment, 

 the arc the wing moved in (90°) and the length of the diagram 

 were divided into eight parts (Fig. 6), the angles the plane of the 

 wing made with the direction of the thrust were plotted at their 

 seven respective positions ; the thrust pressures from the diagrams 

 (Fig. 4) were set off, half-size for convenience, on these angular 

 lines ; and the right-angled triangles of forces completed : then 

 the sum of the hypothenuses was multiplied by the distance in 

 feet traversed by the centre of the wing during one-eighth of its 

 down or up stroke, that is 0*96 feet, and this multiplied by 20 for 

 the revolutions per minute, and then by 2 for the other wing, 

 gives 3338 as the foot-pounds of power per minute expended on 

 the handle. The same process was carried out with the thrust 

 pressures and lost powers, giving 920 foot-pounds per minute or 

 27 per cent., as useful work done. The right hand side of the 

 diagrams (Figs. 4 and 5) corresponds with the position of the wings 

 represented in (Figs. 1, 2, 3). 



Turning to D. K. Clark's tables to check the accuracy of the 

 observations, we find Mr. Smeaton gives the ordinary power of a 

 labourer to be 3762 foot-pounds per minute. Mr. John Walker 

 says the power of a man turning a handle is 3080 foot-pounds per 

 minute. Mr. Glynn says the power of a man at a crane handle is 

 3300 foot-pounds per minute. Mr. G. B. Bruce says the power 

 of a man at a pile-driver, presumably winding up the monkey, is 

 4320 foot-pounds per minute. Mr. Joshua Field has some tabulated 

 observations, amongst which is one shewing that a tall Irishman 

 with extreme labour exerted a force at a crane handle of 21,427 

 foot-pounds per minute for 2*83 minutes ; whilst yet another tall 

 Irishman at the same job did 27,562 foot-pounds per minute for 

 2*2 minutes. It is therefore thought, that 920 foot-pounds per 

 minute fairly represents the amount of thrust the machine is 

 capable of, and that the diagrams delineate its distribution. 



As to what effect this thrust would have if the machine were 

 on a good stretch of permanent way or clean ice, there is nothing 

 to draw a comparison from but experiments connected with the 

 resistance of trains. According to D. K. Clark the fractional 

 resistance per ton of engine, tender and train for speeds of 5, 10, 

 15, 20, 30, 40, 50, 60 miles per hour are 12-2, 13, 14, 15-5, 20, 

 26, 34, 43 lbs ; these are, let it be understood, with an average 

 side wind, so that all the front ends of the carriages add to the 

 resistance. Taking this machine to weigh one-tenth of a ton, the 

 continuous thrust of 3*07 lbs would keep it going at a speed 

 exceeding 40 miles per hour. 



