WINDMILLS 



303 



FIG. 205 RECONSTRUCTED 

 TURBINE 



shop-made mills. They may 

 be classified by the form of 

 the wheel and the method of 

 governing. 



1. Sectional wheel with centrif- 



ugal governor and independ- 

 ent rudder (Fig. 206). 



2. The solid-wheel mill with side- 



vane governor and inde- 

 pendent rudder (Fig. 207). 



3. Solid wheel with single rud- 



der. Regulation depends upon 

 the fact that the wheel tends 

 to go in the direction it 

 turns. To aid in governing, 

 the rudder is often placed 

 outside of the center line of 

 wheel shaft (Fig. 208). 



4. Solid or sectional wheel with no rudder back of tower, the pres- 



sure of the wind being depended upon to keep the mill square 

 with the direction of the wind. Regulation is accomplished with 

 a centrifugal governor (Fig. 209). 



425. The use of the windmill. The windmill receives 

 its power from the kinetic energy of the moving atmos- 

 phere. Since this is supplied without cost, the power 

 furnished by a windmill must be very cheap, the entire 

 cost being that of interest on the cost of plant, deprecia- 

 tion and maintenance. Where power is wanted in small 

 units the windmill is a very desirable motor, provided 



1. The nature of the work is such as to permit of a suspension 



during a calm, as pumping water and grinding feed. 



2. Some form of power storage may be used. 



426. Wind wheels. T. O. Perry built a frame on the end 

 of a sweep which revolved in an enclosed room in such 

 a manner that he could fasten different wheels on it with- 

 out making any change in the mechanism. By this means 



