J2 BULLETIN 173, U. S. NATIONAL MUSEUM 



located just behind the wind wheel, which tends to throw the wheel 

 out of the wind as the wind pressure increases, and a weighted lever 

 so connected to the hinged rudder vane and the wheel bracket that it 

 opposes the action of the safety vane. The resulting action of the 

 governor is to turn the wheel away from the direct force of the wind 

 as the wind velocity increases and to turn it back as the wind 

 decreases. 



PRAIRIE WINDMILL 



U.S.N.M. no, 309688; model; made in the Museum; not illustrated. 



The model represents a horizontal paddle-wheel windmill of the 

 type used to some extent on the prairies of the United States. The 

 model shows the windmill set up to pump water to an irrigation flume. 

 The axle of the wind wheel is mounted on bearings supported on the 

 top of a board fence that encloses the lower part of the paddle wheel. 



Paddle-wheel windmills differ from the sail-wheel mills in that the 

 paddles move in the direction of the wdnd rather than across the 

 wind, and it is necessary to make the paddle-wheel feathering or 

 shield part of it so as to prevent the wind from striking the paddles 

 that are moving in the direction opposite to that of the wind. The 

 axis of the paddle-wheel type may be either horizontal or vertical. 

 The use of the horizontal type is limited by the fact that it operates 

 only when the wind is in the direction nearly perpendicular to the 

 axis of the wheel. 



VERTICAL WINDMILL, 1879 



U.S.N.M. no. 309690 ; original patent model ; transferred Irom the United States 

 Patent OflBce; not illustrated. 



This model was submitted with the application for the patent issued 

 to W. A. Wheeler, July 1, 1879, no. 217053. 



A vertical-axis paddle-wheel windmill in which the wheel consists 

 of an upper and a lower horizontal rim between which are many 

 vertical, narrow, wooden-slat sails. The slats are pivoted in the rims 

 and are connected to a centrifugal ball governor, which regulates 

 the speed of the mill by changing the angle of the slats. A hand lever 

 connected to the collar of the governor permits the operator to stop 

 the wheel by turning the slats so far that they present a continuous 

 closed cylindrical surface to the wind. Stationary guide vanes direct 

 the wind to the sails of the wheel. 



Vertical paddle-wheel windmills have a slightly wider application 

 than the horizontal ones. They can be built to receive the wind from 

 all directions and are comparatively easy to regulate and govern. 

 They have been built in sizes from 4 to 24 feet in diameter and are 

 usually placed on low buildings. Many have been used successfully 

 for grinding wheat. 



