10' Challenge OK Windmill History
Introduced into the Challenge line of windmills about 1885, the OK was the first solid wheel mill produced by the Challenge firm of Batavia, Illinois.  Governed throughout the use of a side vane mounted on a stem attached to a hollow wrought iron mast, the mill was sold widely during the last years of the 19th Century and the early years of this century.  Substantial numbers have survived to the present day.
The Challenge Windmill & Feed Mill Company in presenting the new OK Mill about 1885, noted that it did so in recognizing a trend in the trade "drifting toward cheaper pumping wind mills" and that the firm had "at last decided to put on the market a Solid Wheel Mill" which it already had been making for some time for another party.  The OK remained available from the company until about 1914 after which time it was phased out of production.  In governing, the OK is pushed out of increasing winds through the action of a wooden side vane parallel with the wind wheel. As the wheel turns away from increasing winds, the governor linkage at the head of the mill causes a weighted governor lever near the base of the mill to rise.  With decreasing wind velocities, the weight on the lever pulls the wheel back into a  position more squarely facing the direction of the wind. The sensitivity of the governor is regulated by adjusting the position of the weight on the  governor lever.
OK windmills were manufactured in either regular or long stroke patterns with 10', 12', 13', 14', 16', and 18' diameters.  Two different vane patterns were used.  The earlier style has a curve trailing edge whereas in later years a swallow tail design was employed.  The wheel of the mill is composed of sections of wooden blades nailed to curved wooden rims.  Both the wheel and the vane are painted white with green trim, with the wooden arms painted red or light blue, giving the whole mill a pleasing appearance. The inscription the vane is stenciled in black.
One of the striking features of the OK is its hollow wrought iron mast, which is supported below  the platform of the tower on a bed plate.  The entire mill on its mast rotates on this bed plate in order to face the wind, placing the weight of the mill within the tower instead of on its top. This hollow mast extending above and below the platform is one of the most prominent identifying characteristics of the mill.
A variation of the OK manufactured by the Challenge firm from the early 1890's through the outbreak of WWI was the Daisy OK.  This mill was almost identical to the original OK with the exception of the fact that the corner posts of the tower extended above the platform to a cast iron tower cap on which the head of the mill rests.  The design eliminated the use of the long wrought iron mast used on the regular pattern OK.  The vane of the Daisy OK bears the black stenciled inscription, "Daisy C.W.M.& F.M. Co. Batavia, Ill." and the letters OK appear prominently on the side vane.  The Daisy was manufactured in both regular and long stroke patterns in the same sizes as the original OK mill.
Although OK mills were marketed across all of the Great Plains and Midwest, they are probably most commonly seen today in western Nebraska, where they were exceedingly common at the turn of the century.

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