Analysis of the 



Although this is interesting, for the purpose of evaluating F , which is never very great, 

 BR is small and negligible in comparison with A. The condition when v—k> may be written 



pVJ- ird 2 D 



TjC.V 



= T, 



[ft-O] 



where 77 is the number of cups, d is the diameter of the cups, D is the diameter of the cup center 

 orbit, and Tis the dynamic frictional torque of the bearing which is substantially constant for a 

 good ball bearing. 

 Then 



V n 



16T 



■qC '.v pitd-D 



Table I 

 Tests on Four Cup Anemometers at the Massachusetts Institute of Technology 



Index d/D d D F h k 



.OC2 



.031 



.604 



3-97 



•93 



