Free Electric Power Windmill

Free

Electric Power Here the 10-ft, impeller described below has been mounted for belt drive. Note position of jackshaft on the baseboard.

Y

OUR vacation cottage or outlying farm buildings can be lighted by electricity even though you may be far from a power line. The wind will gladly do this job for you—if you know how to harness it. The unit described will turn the trick for you with little manual effort and even less monetary expense. Most people think of gales and hurricanes when the wind is mentioned as a source of power. Nothing could be more misleading, because there is vast energy even from a gentle breeze. Anyone with ordinary mechanical skill can build this machine. And cutting the impeller blades will teach you more practical aerodynamics than you could dig out of an armful of books. (If the term "impeller" confuses you, a propeller driven by the wind becomes an impeller.) Without digging too deeply into theory, it is well to know a little about the giant which we are about to harness. It is seldom realized that the force which the wind exerts is composed of two distinct parts: a pressure and a suction. Thus a sailboat which seems to be pushed along by the wind is actually deriving most of its pro-

pulsion from the suction on the lee side of the sail. A roof in the path of a gale is lifted up, not pushed down. Consequently, the blades of the impeller must be so shaped that this suction force can aid them in turning. For the baseboard get a piece of oak or similar hardwood, 5-1/2 in wide, 50 in long and 1-1/4 in thick. Draw a centerline on the wide face of the board and do your layout from this guide. From a point 9 in. from the head and down to the end of the board the sides are tapered down to a final width of 1-1/2 in. Drill a 3/4-in hole 26 in. from the tapered end and saw a 1/2-in slot to meet this hole. This slot is for the tail vane. For 'the generator cradle a piece of wood 6 in. long and 1-1/4 in thick is fastened to the full end width of the baseboard. Shape the cradle to match contour of generator used. The tail vane is a piece of exterior-grade plywood 30 in. long, 20 in. wide and 1/2 in. thick with the leading edge rounded and the trailing edge notched as shown. The commutator (or collector rings) used to connect the swinging generator with feed wires is essential [continued on next page]

Free Electric Power for proper operation. To make it, get a piece of 2-in. brass pipe 3 in. long, a piece of wood with 2-in.-square and 4 in. long, and an 18 in. length of 1 in. galvanized iron pipe threaded at one end. Trim the wooden block into a cylinder that fits snugly into the brass pipe. Drill a 1-1/4-in. hole lengthwise through this cylinder true to the centerline. Soap the threaded end of the galvanized pipe and drive it through the hole in the wood until it extends far enough in the floor flange. To engage the two insulated collector rings, cut two 1/2-in. sections from the brass pipe and connect these to encompass the wooden cylinder. Fill the space with Plastic Wood and trim flush. Drill holes through each brass ring and the galvanized pipe to take the insulated wires from the generator. Solder the ends of these wires in the brass holes and file the outside surface smooth. The brush holder is fastened to the edge of the 1-1/4-in. galvanized floor flange. This floor flange is the top end of the 1-1/4-in. galvanized pipe which serves as the mast. Its upper surface should be ground smooth to ease the generator's swing into the wind. The auto generator, available at any auto graveyard, should preferably be one from any of the large, older cars, since its output capabilities will be higher and its price lower. The jackshaft assembly and its strap iron supports are now made. A bronze bearing is soldered into each end of a 7-1/2-in. length of 3/4-in. brass pipe. Align the bearings with the shaft before soldering. The brass pipe acts as an oil reservoir and a small hole is drilled so that it may be filled. The hub plate to hold the three blades is an 11-in. circle of 1-3/4-in. exterior-grade plywood, or maple. Center it accurately on the end of the jackshaft and fasten securely with a flange and stove bolts. Cut a vee for a belt into the hub plate edge. Adjust the height of the jackshaft above the base to take a standard automobile fan belt connecting hub plate and generator pulley. The impeller of this generator is ten feet in diameter and has three blades. It will make about 200 revolutions per minute in an eightmile-per-hour wind. To assemble the impeller, obtain three pieces of straight, knot-free, well-seasoned wood, each 60 in. long, 6 in. wide and 1-1/4 in. thick. Lay them on the bench side by side, with grain running away from you and mark the top of each piece "face" and bottom "back." Draw a squared line across each board at six-inch intervals and mark each line with its distance from the preceding line, as 6 in.,

12 in. and so on. To make your task easier, cut cardboard templates corresponding to degrees of slope that will fit the finished blades at the proper points. " Cut the face of the blade first. This is a flat surface but of continuously changing angle with respect to the original face of the board. The trailing edge is always 1/16 in. thick. The sloping face intersects the top of the board up to the 30 in. line and new leading edge is cut along this distance. To cut the blades clamp the hub of the blade flat to your bench with the tip extending straight out. Stand to the right of the blade and draw a sharp drawknife toward you until the approximate contours are reached. Fasten the three blades to the hub plate with carriage bolts using three for each blade. For the impeller to run without vibration it must be carefully balanced and the jackshaft (if it runs true and free) can be used as a balancing rig. Remove small shavings from the heavy blade until the impeller comes to rest at a different point each time it is given a light spin. With the entire wind-electric generator assembled, including the impeller, find the center of balance of the baseboard and attach the 1-in. floor flange above the commutator at this point. Center of balance is that point about which the entire unit balances itself fore and aft. To protect all wooden parts against weather, soak generously with linseed oil or coat with outdoor paint. The 1-1/4-in. pipe should be well braced. If guy wires are used, make sure that they do not hinder the rotating blades. Mount the generator in place by slipping the 18-in. length of 1 in. pipe below the commutator into the mast. Brushes will then make contact with rings of the commutator. The feed wires to the unit are attached to the two- spring brass brushes with the wiring exactly like that in your car. The cutout (to disconnect the generator from the battery when it is not charging) is the standard automobile type and may be left mounted on the generator or may be placed near the battery. You will also need an ammeter and a protective fuse. Mount them on a plywood panel 6x8 in. A small six or eight-volt radio panel bulb will show at a glance when the generator is charging. If you use a six-volt generator a standard automobile storage battery will be enough to store juice during calm periods. For higher voltage systems several units of auto batteries may be connected in series. [END]