Spoke and Disc Wheels 



117 



which follows the disks were made of a thick and firm cardboard — 

 called "beaver board". 



Seven light cast iron pulleys were mounted on a line shaft some 

 twenty feet long. The shaft was driven by the variable speed motor 

 used in the wheel experiment. One of the pulleys was 30x4.5 inches, 

 four were 24x4, one was 20x4, and one 16x4 inches, all having six 

 spokes. The spokes were elliptical, thin and almost flat, a form designed 

 to minimize air resistance. Notwithstanding this fact, the power re- 

 quired to drive the shaft was noticeably lessened when the spokes were 

 covered v/ith beaver board disks. 



Table II gives the power required to drive the shaft at speeds be- 

 tween COO and 800 r.p.m., when all the pulleys were open, spokes or 



R.P.M 



2000 



1500 



1000 



500 



500 



1000 1500 2000 ^)^JJS 



Fig. 1. Results of experiments to determine the power recjuired to drive disk and 

 spoke wheels and pulleys. D, power curve for disk wheel ; S, for spoke wheel ; C, for 

 pulleys with spokes covered ; O, for pulleys with spokes open. 



arms exposed — and when all were closed by means of card board disks, 

 spokes enclosed. A plot of some of the results gives the curves and C 

 of figure 1, the former for open pulleys, the latter for closed pulleys. 



The results tabulated are for two cases only — all pulleys open, all 

 closed. Observations were made by measuring the driving power re- 

 quired for all the speeds tabulated — first with all the pulleys closed, 

 then with one open, then two open, and so on to the last series, when all 

 the pulleys were open; that is, all the disks had been removed. The 

 driving power increased slightly every time a pair of the protecting 

 disks was removed. 



Inspection of table II and curves O and C shows the web pulley 

 at moderate speeds has little advantage over the spoke pulley of the 

 type used. But at the higher speeds the difference is a matter worth 



