Sa 
MURPHY: POWER OF A TWELVE FOOT ‘‘POWER” WINDMILL. 199 
tion in (23) we get the relation between total horse power (useful 
and useless) and wind velocity for one strip. The relation between 
v and c for the curve AK is given in equation (10) namely v—=.2Re. 
Substituting this value in (23) we have 
; 0,00169A'!cos@ (1-+-(.2R)?—.2Rcotp) ® War 
(HE 4 ; (.2R)%3 (24) 
550 [r1-+(C.2R)*]4 
Fig. 6 shows one fan of this mill divided into four strips. The 
ig. 6. 
values of b, R, v, A anda for each strip are given in table I. 
i Vv ; : 
Since tan a and v=z.2Rc, tan a==.2R, that is a is constant 
Cc 
for any strip for all values of c. 
‘ i ‘ /c-a ‘ 
For one of the constant load curves as CR, v V maa see equation 
‘ ) 
a : 
~, hence a must decrease asc increases. 
hei 
[c-a 
(Cuchi Gyan hints) V5 
) 
Cc 
From (21) it is seen that as a decreases P,, decreases, and conse- 
quently the power of the mill. 
Ry eashen a 
b RK V A coin 
647 
.8o1 27 i HC .483 47°—30' 
1.062 Shi) WG 1Oe2 41 —45 
1.312 4.5 “gc Vel 7 34 ae 
1.503 5.5 Deore T.441 4 53 
Substituting for A! and R the different values shown in table I 
and for cosf its value, and multiplying by 18, the number of fans, 
we have for the total horse power of this 12 foot mill 
