314 FARM MOTORS 



rod is put in place to drop a plumb bob from the center 

 of the top of the tower to the intersection of cords 

 stretched diagonally from the corners of the tower at 



FIG. 211 RAISING A TOWER 



the base. If the plumb bob does not fall on this inter- 

 section, either the braces do not have equal tension or 

 the anchor posts are not level. 



435. Economic considerations of windmills. Many 

 manufacturers claim much more power than the wind- 

 mills really develop. This erroneous claim is probably 

 due to the fact that early experimenters worked with 

 small wheels and figured the power of larger ones from 

 the law of cubes, which does not seem to hold true in 

 actual practice. It is wrong to say that a good 12- 

 foot steel mill will furnish I H.P. in a 2O-mile wind and 

 that a good 1 6-foot mill will furnish 1.5 H.P. 



The economic value of a windmill depends upon its 

 first cost, its cost of repairs, and its power. The com- 

 petition in manufacture at present is so great that often 

 the initial cost is kept down at the expense of the other 

 two. 



A mill should have as few moving parts as possible. 

 The power of a mill is so small that if there is much to 

 retard its action there will be very little power left 

 for use. 



