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Step 3Shortening the Length of the Blades for a Safer, More Portable Device:
Even in mild wind conditions, the Air-X blades spin quite fast -so fast the wicked "hiss" they generate actually makes my skin crawl. The thin, sharp, dense blades could easily kill anyone who gets in their way. You would NOT want to use these blades on a yard ornament. I painted the blade tips fluorescent orange and used fluorescent orange guy-lines to brace and support the mast. The generator blades are now well out of harm's way, with adequate, visible rigging in between.
In an effort to make the wind generator safer, more manageable -and portable, I carefully examined, and then sawed 4 inches off the ends of the blades (to a new over-all length of 18-3/16 inches long) and, after adding the parabolic nose, have yet to detect a change in the performance characteristics of the highly engineerd blades, except in the furling. The generator actually needs to be re-mounted on a thicker block of varnished wood, with the axis of the generator offset to a new position of about 2-5/8" from the axis/pivot of the hinge (but this has not been tested yet). A wind speed of 9-10 mph will now put a pressure of about 1.37 pounds on the spinning blades, initiating the furling process, and keeping the DC voltage at a manageable level.
Later... in an effort to make the wind generator even more safer, even more manageable -and even more portable, I sawed off another 5-1/16 inches off the ends of the blades (to a new over-all length of 12-1/2 inches long). And the generator still flywheels in 5 mph (2.24 m/s) winds, generates a charging current at 7 mph (3.13 m/s). But, now, the unit doesn't furl until 12 mph (5.36 m/s) winds, producing up to 40 Volts. As the spring in the spring hinge is not designed to be tampered with, to a weaker tension, the generator actually needs to be re-mounted on a thicker block of varnished wood, with the axis of the generator offset to a new position of about 3-3/4" from the axis/pivot of the hinge (but this has not been tested yet). A wind speed of 9-10 mph (4.02 - 4.47 m/s) will now put a pressure of about .67 pounds on the spinning blades, initiating the furling process. Also, with the shortened blades, a 24 Volt (instead of a 12 Volt) system may be desirable, and appropriate, for some applications.
But instead of fashioning new wooden generator mounting blocks, a quicker (if not elegant) way to initiate furling, to a lower wind speed, is simply to attach and stretch a simple rubber band, from the right-rear of the generator, to add .5 - 1.5 pounds of tension, coax the blades off their 90 degree (perpendicular) to the wind orientation, to advance the furling process, keeping the DC voltage to a manageable level. After all, once the blades tilt past 90 degrees, all it only takes about 1 pound of wind pressure to force (and hold) the blades into a 0 degree (edge-on) position, fully furled, which is the same regardless of the blade lengths. I enjoy designing and building aesthetic things, but there is no denying that the world is really held together with scotch tape and bailing wire.
But, ultimately, I decided that full battery charging voltage, in low wind speeds, was most important and ordered a new set of blades (over-all length of 22-3/16 inches). And a triangular-shaped case is being built to house the blades, hub, and shaft arbor -as one unit.
The spinning blades of a wind generator produce about as much pressure as a solid disk, of the same diameter. That explains why reducing the length of the blades will always require some sort of loosening of the spring tension (or leveraging) of the side-furling device: To change that simplified frontal "circle" into a more controllable ellipse, as viewed from the front, whenever the wind threshold is reached.
Some quick math indicates that the improvised generator, with full-length blades, without furling, could possibly generate 70VDC, 100 watts, @ 32mph (14.31 m/s) and spinning at 2,150rpm, which the Air-X blades, on a special Air-X hub, are fully capable of. But such voltage is beyond the ability to harness into any practical, portable capacity -not to mention designing a truly portable tower that could stand up to such a wind, with a generator that does not furl.
To complicate matters, many wind generators are marketed, posting their maximum watt rating -in almost gale-force winds, and novice owners mistakenly purchase high-current 12 Volt appliances, with the expectation their wind generator will always be able to power them. A good rule of thumb is 15% of advertised wattage equals the average wattage you'll probably get, in actual field conditions. Reputable dealers may advertise the maximum wattage in their headlines, to, understandably, catch your attention, but will also post a chart of actual watts, for given wind conditions.
In an effort to make the wind generator safer, more manageable -and portable, I carefully examined, and then sawed 4 inches off the ends of the blades (to a new over-all length of 18-3/16 inches long) and, after adding the parabolic nose, have yet to detect a change in the performance characteristics of the highly engineerd blades, except in the furling. The generator actually needs to be re-mounted on a thicker block of varnished wood, with the axis of the generator offset to a new position of about 2-5/8" from the axis/pivot of the hinge (but this has not been tested yet). A wind speed of 9-10 mph will now put a pressure of about 1.37 pounds on the spinning blades, initiating the furling process, and keeping the DC voltage at a manageable level.
Later... in an effort to make the wind generator even more safer, even more manageable -and even more portable, I sawed off another 5-1/16 inches off the ends of the blades (to a new over-all length of 12-1/2 inches long). And the generator still flywheels in 5 mph (2.24 m/s) winds, generates a charging current at 7 mph (3.13 m/s). But, now, the unit doesn't furl until 12 mph (5.36 m/s) winds, producing up to 40 Volts. As the spring in the spring hinge is not designed to be tampered with, to a weaker tension, the generator actually needs to be re-mounted on a thicker block of varnished wood, with the axis of the generator offset to a new position of about 3-3/4" from the axis/pivot of the hinge (but this has not been tested yet). A wind speed of 9-10 mph (4.02 - 4.47 m/s) will now put a pressure of about .67 pounds on the spinning blades, initiating the furling process. Also, with the shortened blades, a 24 Volt (instead of a 12 Volt) system may be desirable, and appropriate, for some applications.
But instead of fashioning new wooden generator mounting blocks, a quicker (if not elegant) way to initiate furling, to a lower wind speed, is simply to attach and stretch a simple rubber band, from the right-rear of the generator, to add .5 - 1.5 pounds of tension, coax the blades off their 90 degree (perpendicular) to the wind orientation, to advance the furling process, keeping the DC voltage to a manageable level. After all, once the blades tilt past 90 degrees, all it only takes about 1 pound of wind pressure to force (and hold) the blades into a 0 degree (edge-on) position, fully furled, which is the same regardless of the blade lengths. I enjoy designing and building aesthetic things, but there is no denying that the world is really held together with scotch tape and bailing wire.
But, ultimately, I decided that full battery charging voltage, in low wind speeds, was most important and ordered a new set of blades (over-all length of 22-3/16 inches). And a triangular-shaped case is being built to house the blades, hub, and shaft arbor -as one unit.
The spinning blades of a wind generator produce about as much pressure as a solid disk, of the same diameter. That explains why reducing the length of the blades will always require some sort of loosening of the spring tension (or leveraging) of the side-furling device: To change that simplified frontal "circle" into a more controllable ellipse, as viewed from the front, whenever the wind threshold is reached.
Some quick math indicates that the improvised generator, with full-length blades, without furling, could possibly generate 70VDC, 100 watts, @ 32mph (14.31 m/s) and spinning at 2,150rpm, which the Air-X blades, on a special Air-X hub, are fully capable of. But such voltage is beyond the ability to harness into any practical, portable capacity -not to mention designing a truly portable tower that could stand up to such a wind, with a generator that does not furl.
To complicate matters, many wind generators are marketed, posting their maximum watt rating -in almost gale-force winds, and novice owners mistakenly purchase high-current 12 Volt appliances, with the expectation their wind generator will always be able to power them. A good rule of thumb is 15% of advertised wattage equals the average wattage you'll probably get, in actual field conditions. Reputable dealers may advertise the maximum wattage in their headlines, to, understandably, catch your attention, but will also post a chart of actual watts, for given wind conditions.
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