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WINDMILL CONSTRUCTION AND GENERATING POWER
DESCRIPTION: THIS BOOK DESCRIBES HOW TO BUILD POWER
GENERATING WINDMILLS. IT HAS A LIST OF CURRENT
SUPPLIERS. IT WAS ORIGINALLY PUBLISHED IN 1910. WE
HAVE ADDED AN UPDATE CHAPTER THAT DISCUSSES MODERN
WINDMILLS AND SUPPLIERS.
A PRACTICAL WORKING WINDMILL
To complete the series of small windmills suitable for amateur workmanship, a really practical machine, capable of "power" production on a moderate scale, remains to be described. It is thought that a mill of 10-feet diameter, while probably taxing to the fullest the constructive ability of any average reader, might well be attempted by a serious worker with happy results. In this instance, while preserving the general principle of simplicity, completeness has been aimed at, and castings and forgings are adopted throughout without hesitation. This certainly involves some pattern-making, which, however, should be within the scope of any one able to carry out the necessary machining of the castings. Some readers may be willing-and able to reduce this part of the labor by adopting makeshift details, but it should be remembered that such a method is hardly more advisable than it would be in the case of building any other motor-say a steam engine for power production.
The rating for a 10-foot windmill would be about 1/4 H.P., which probably appears small for the amount of work involved and the material employed. It is, however, a conservative estimate, and is based on the standard 16- mile breeze, which holds good for something like 8 hours per day on two-thirds of the days in the year. Manufacturers probably rate a mill of this size much higher, and as long as no wind velocity is stated, they may claim to be correct. All practical modern windmills however, are constructed with automatic gear so that with any given velocity of wind a maximum output is obtained, and any increase in the wind is more or less counteracted by the action of the automatic gear. It follows therefore that if our 10-foot mill is set to produce say 1/2 H.P., it can only do this with a wind of much higher velocity than 16 miles per hour, which is also much more rare. Nevertheless, it will be quite within the maker's power to get as much as this and more out of his machine, if he so desires and the wind is there. It will be merely a question of altering the controlling weight, but will also involve very much heavier stresses on the machine. This point must be borne in mind.
A general elevation is given in FIG. 48, to a scale of 1/4 inch to the foot.
The tower is built up of four 3 inches X 3 inches vertical members, 12 feet high, each placed at the corners of a square, with 4-inch space between each pair of uprights. These uprights are well braced by struts, also of 3 X 3 timber, starting below the circle of vanes, one strut on each side, and each bolted to two uprights, as shown. The lower ends of struts are lodged into two horizontal diagonals, which are halved over each other at their crossing so as to lie level. The lower ends of uprights with a little shaping will also fit alongside these diagonals and must be securely bolted to them with 1/2 inch bolts. Bolts or straps must also secure the diagonals to the feet of struts. Four 3/4 inch bolts not less than 3 feet long must be carried down at the four ends of the horizontal members, into pockets of rough concrete of 2 or 3 cubic feet each.
The holes above the concrete must be then very firmly filled in and rammed, and if the ground is soft or yielding, a greater depth and more concrete must be employed. It is perhaps needless to insist on the importance of having all this timber, but- especially that in contact with the ground, thoroughly well tarred, or better still, properly creosoted, and all bolts should be galvanized. Large thick washers under the nuts of the 3/4 inch bolts are required.
A more detailed side elevation of the head, tail, and part of the arms is given in FIG. 49, to a scale of 3/4 inch to the foot. This shows the movable head casting A carried on the bearing casting B. Both these are detailed still further, to a scale of 1 1/2 inches to the foot in FIGS. 50 to 54, and require little explanation. The stem of A is of course turned to ride easily in the bored hole in B, and is fitted with brass bushes for axle and for vertical shaft. The casting B is securely bolted to the tops of the 3 X 3 uprights with 1/2 inch bolts, care being taken to get it truly upright and central with the timbers.
TABLE OF CONTENTS:
1. WINDMILL EVOLUTION
2. A MODEL WORKING WINDMILL
3. A SMALL AMERICAN TYPE WINDMILL
4. A SMALL WORKING WINDMILL
5. A PRACTICAL WORKING WINDMILL
6. PRODUCTION OF ELECTRICITY BY WIND-POWER
7. MODERN WINDMILLS