Fig. 2 can be traced onto a piece of cardboard or thin metal to be used as a template.
The trailing edge should be about 1/16th inch thick. One-half the thickness of all layout lines should be visible when you're finished. If you take off too much or nick it with the chisel, the holes can be filled with epoxy body filler or wood dough and sanded smooth.
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FOR THOSE MAKING KIT BLADES: All you have to do is plane a bit off the upwind side to the line of the leading edge, and about 1/16th inch thick for the trailing edge, or as thin as you dare. Keep the upwind face flat from edge to edge. Don't get fancy and invent a special airfoil on the spur of the moment, remember NASA uses a computer and birds have taken 50 million years. The layout lines should all be visible when you're through. Trim 1-1/2 inch off the root ends so they fit together at the center on the hub.
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After the pitch and foil are sanded and painted, protect the leading edge with a strip of stainless steel tape (available from Napa Auto Supply) held on with nonferrous tacks or staples about 5/16th inch long. Thin copper flashing works well also. Glue the flashing with formica adhesive. The metal tape is to keep dust and weather from raising the wood grain, which would spoil the airfoil
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Measure the tapes all the same length (about 3 feet) and the same distance from the hub. Stick them to the flat side first and fold them over the leading edge and onto the back side by slicking them lengthwise, folding about 1/8th inch at a time with a piece of smooth wood To prevent wrinkles, slick from the middle towards the ends. With a gun, put 5/16 staples about 1 inch apart along the edges to hold the edges down and prevent wrinkles when the blades flex.
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The next step is mounting the blades on the hub. Lay out a 9 ft. diameter circle on the floor with chalk. Still using the same radius (4-1/2 feet), mark off six equal radius length points around the perimeter. lt should come out even. If it didn't, you muffed it, so lay it out again. Pythagoreas or Aristotle claimed it was geometric proof of the order of the universe that the arc of a circle will subdivide into six equal parts using the radius as one unit of measure, (but lately it seems to have become a matter of opinion). When it comes out even, erase every other point and you will have three equally-spaced points around the circumference. Lay the blade tip centerline on those points, up-windside down.
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The hub is made of a triangular piece of 3/4th inch plywood and a triangular piece of 18 or 20-gauge galvanized tin.
Drill a 1- 1/8th inch diameter hole in the center of the tin. A sharp cold chisel on a hard surface does an acceptable job but ragged edges should be filed.
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Slide this piece of tin under the blades at the hub and line up the hole on the center of the 9 ft. circle. Place the 3/4 inch plywood triangle on the top (downwind) of the blade root ends, and line it up with the tin on the bottom. Hold it in place with your knee and drill five holes (3/16 inch dia.) in each root end through all sandwich pieces (mind the floor!) and bolt them solid with 3-1/2 inch #10 RH (Round Head) machine screws. Stainless are best, if unavailable use more or heavier bolts, 1/4 inch maybe. Measure to be sure they are equally spread, then line up a pulley flange on the upwind side shaft hole and drill 5/16+ holes through the tin & all for the 3 flange bolts (B-11). Drill a one or 1-1/8th inch hole for the shaft to go through. Run wood sealer or penetrating epoxy into all these holes until they are good and soaked, otherwise the bolts may work loose with changes in temperature and humidity.
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Next, whip up some kind of pulley mount, depending on what kind of pulley you use. I'm sold on aluminum "V" belts because they are cheap and handy almost everywhere. Some people like cog belts or chain drive, I think they're too much hassle, noisey, heavy, and too expensive. I've used iron pulleys but they rust and the corrosion chews up the belt. Wood might be good if the surface is hardened with Polyethylene Glycol, or some of those chemicals used for turning thin wooden bowls. Don't use epoxy because it makes the belt crack. If the wood shrinks across the grain, theĘpulley will get out of round and make the blade vibrate from the uneven beltĘtension. Another advantage to the aluminum pulleys is that the spokes are usually identical between sizes from a given manufacturer, so they can be interchanged in a second to try out the best ratio for your alternator, so cut your pulley mount to fit the spokes. A spacer block should be placed between the rear hub board and the pulley mount so there will be some clearance between the blades and the alternator.
I get my pulleys and belts from W. W. Grainger Supply Co. in the yellow pages or at www.grainger.com. They have a good catalog for that kind of stuff. Generally, the belt sizes are; For 8 inch pulley, 3/8 X 35 inch diameter "V" belt; for 10 inch, 3/8 X 41 inch outside diameter "V" belt; for 12 inch, 3/8 X 48 inch O.D. "V" belt. But set it up and measure to be sure.
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The pulley mount and spacer block should be screwed to the rear hub board and NOT GLUED to it, so that it can be tapped into center alignment once the blade and belt are mounted. If the pulley is off center slightly it will cause uneven tension on the fan belt and the blade will appear to be vibrating even though it's well-balanced. To center it, loosen the bearing and flange bolts then tap the pulley with the heel of your hand until the belt tension is equal throughout a complete revolution. Then tighten down the flange bolts and the pulley mount screws. Moveing the bearing too far in this adjustment may push the blade out of balance.
Seal it all and paint with floor enamel or topside paint. A primer coat wouldn't hurt either, but don't put a latex topcoat over an oil base primer or sealer because the latex will crack, oil on latex primer is ok though.
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The blade must be assembled with bearing, flanges, pulley, bolts, paint, and the leading edges covered before balancing. If it's put on afterwards, it'll affect the balance. Suspend the blade from the balancing qadget shown in Fig. 4.
It's made from
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a 5 inch piece of 3/4 inch copper pipe "L" wall, ("M" wall is thinner)
- 2 metal discs 25/32 inches in diameter with a small hole in the center of each (a penny will work, but fill the hole when you're through because it's illegal to deface them). Be sure the hole is centered.
- a short piece of straw or 1/8 inch plastic tube. Split the straw or tube down one side so it can be removed and trimmed easily to adjust the height of the disc.
- a piece of braided string.
One disc is soldered just inside the end of the 3/4 inch copper pipe (yes, it ll fit). Don't remove the burr left by the pipe cutter and it'll be a better job. You do have to remove the burr on the other end to slide the disc in. String the whole gadget together on a wire or a piece of braided cord, twist cord works-but you grow old waiting for it to unwind after the blade is hung. Tie a knot on the inside and a loop on the other end. Insert about 4 inches into the front (upwind) side bearing. It should just fit with a few taps, but if it doesn't, scrape the tube with a pocket knife. The end with the soldered disc should go in first and the upper end should be driven in until it's just a little more than halfway through . Don't let the tube touch the wood inside, it may push one of the bearings off-center and cause the axle to be other than 90 degrees to the plane of the blade (which is not cool). Maybe remove the bearing with the tube through it when it's about right and wrap the end of the tube with tape so it will plug fit into the shaft hole and tend to center the bearings more accurately . Eyeball the other bearing straight too. If the tube is inserted too far, it will not be sensitive enough, not far enough and it will never balance. about 2/3 of the way through the wood parts should be about right.
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Hang the loop from a wire or something in an area big enough to move freely around the blade when it's hung. Look at the top disc, Trim the straw so that it's about flush with the top edge of the rear bearing. If the disc touches one side, you know the other side is too heavy. So, take a few lead sinkers, battery plates, musket balls or something, and put them in a tin jar lid on the stove and heat them up. They'll melt into a nice round flat weight to use as a counterbalance to get the blade level. Pop it out of the lid and hammer the edge round to make it more aerodynamic. Punch two holes in it and start a one-inch wood screw in each hole. Then set -the weight with the screws on the plywood back and. shift it around carefully, until the top disc is centered and not touching anything. Then screw the weight in place. Viola! It's balanced. The government used to balance airplane propellers sort of like that before WW 2.
ADJUSTING FOR THE FIRST RUN
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When sliding the blade onto the shaft, loosen the carriage bolts (part B-6) temporarily so that both bearings will line up more nearly along the same axis. The shaft is a piece of galvanized water pipe and there may be small fluctuations in diameter from batch to batch so if the lock cams on the bearings slide all the way around and won't grip against the pipe, a small piece of shim can be fabricated from a strip of tin. Don't use aluminum shim because it's malability makes it wear loose and the bearings will wear out faster. Roll the shim and insert it between the bearing assembly and the shaft. A better fitting shaft can be made from 7/8 inch diameter round cold roll, bar-stock. I don't use that because it corrodes, is heavy, cost more & is less available. Both cams should be rotated the opposite direction the blade turns and tapped lightly to wedge them snug. Then tighten the set screw and give the cams and flanges two coats of rust inhibitor paint. Make a hub cap out of a light weight tin, stainless, or aluminum salad bowl. Measure the bowls' diameter & scribe a circle on the hub plate. Use 3 evenly spaced sheetmetal screws through the rim.
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SET THE DRIVE BELT loose, about 3/4 inch play, with plenty of belt grip, (available at auto supply or heating and air Conditioning stores). It seems common sense to set it tight, but with the belt stiff and new, it will cause so much friction that the machine will need about 20 -30 mph wind to work, and it won't generate according to the graph. Also the bearings might be stiff, so leave it up for a day or two before allowing yourself to be claimed by suspicions. A slipping drive belt causes the ammeter needle to stop consistantly at a given amperage even though the wind gusts are much higher. Snug the belt up a little, apply some belt dressing, & check the Troubleshooting chart. If the ammeter needle jumps from zero to 5 or 10 amps: the angle of the mercury switch is too steep. Lower the machine or climb up there and loosen the nut that holds the mercury switch clamp, and tip the switch into a slightly more horizontal position. When it's properly adjusted, the needle will climb from zero without a sudden jump start. If the switch is adjusted past its optimum, the needle will show a dip to the discharge side of zero before it starts to charge. It should never show a discharge.
Collecting windspeed data for site selection
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Be sure you have a site with enough average daily windspeed to charge your system. If you know there's enough wind, like the trees are twisted and hedged down to look like bushes with the branches leaning to the downwind side, no topsoil, etc., just check for turbulence and skip the windspeed estimation unless there's a lush undergrowth of annuals and fleshy weeds, which may indicate any strong winds are seasonal. If you want to be technically accurate, get a recording anemometer (source), they cost between $120 and $500. The following procedure requires keeping track but dosen't cost anything, so read it and then decide how accurate you want to be.
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Get a kite and fly it around in a likely looking spot. If the kite dips and flops around, it's a sign of turbulence and should be avoided. Find a spot with nice steady pull so the kite's flying quietly at the same height you'd put the wind generator. The higher the better, but towers cost money and tall trees for a masthead mount will have to be available nearby because they don't transport easily. See that it has a clean shot and smooth terrain from whatever direction the storms come from, no cliffs or trees and ideally 30 feet above and / or 300 feet downwind from any obstacles. But use the kite and get a feel for what the wind does. Then put up some poles (bamboo, Eucalyptus, 2x4's, or pipe) with one-inch-wide plastic streamers three feet long, cut from a plastic garbage sack and tied to the pole about every four feet. Stick the poles up in the general vicinity, say thirty feet apart, and guy them with plastic bailing twine or something.
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During storms (which is where the real amp. hrs. lurk), watch the streamers for the same behavior and find a nice, even breeze. Because of the way the jet stream works, some approximation of a "storm" comes along on the average of once every 2 weeks. Put up a cotton flag in the best spot, about two feet by three feet, like a post office flag or dish towel or flour sack cut open and trimmed to that size. Commercial flags sometimes use lightweight materials so they fly in lower winds, so stick with cotton & hope it doen't get wet. Watch the top edge of the flag and when it's straight out, the wind speed is 15 mph+. When it's down about 30 degrees from level, that's about 10 mph, and that is minimum charging speed. Leave some slack in the rope that holds up the flag so it will stand out from the pole far enough to clear the pole's turbulence for better accuracy. There is also a windspeed scale developed by the English Navy called the Force Beaufort Scale which will work for us too.
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Then get a calendar that has boxes for every day and mark on it an estimated number of hours per day that the wind was blowing at 10 mph or more. Care and perseverance here will help for accuracy. Mark the days when you forgot too, so they don't figure in the tally. Do this for at least a couple of weeks, and more like a couple of months. What you'll get is a list of estimations between 10 and 15 MPH, (using the flag methoed) most useable daily wind falls in this range, That is, if it's less, we can't use it. More is rare, mark those days somehow too.
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To confirm your figures, get hold of the U.S. Weather Bureau. Get a record of what the wind was doing at the nearest weather station during this time and a years average for daily wind. Then extrapolate your site's wind energy potential for the year like this: The windspeed at the station and the windspeed at your site are connected like a ratio. So whatever you got on that day will be in perportion to what wind was blowing at the station, so long as they've got the same terrain or are within 30 miles or so. Figure up how many hours it was blowing say 12 MPH, check the Windspeed-Power Chart and expect a charge of about 5 amps for as many hours as you added up on your calendar. Mountains in hot areas tend to create thermal updrafts which may be usable, but will not show up on Coast Guard records and they indicate a different wind pattern for cold weather.
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Once you know how much wind energy is available at your site, there are two ways to calculate how much it will run. We got the adding-on way and we got the chopping-off way. The chopping-off way is hardest because you have to be cold-hearted and mathematically precise. I only include it so nobody's temperament gets slighted (heh). Make a list of your appliances' watt-hour ratings, then multiply by the number of hours each one is to be used. To this total, add estimated line losses, (you want it to be 10% or less depending on the size of wire you buy. Heavy wire costs more but it might save money in the long run by reducing the size of the battery bank which will wear out before the wires do. See Wire Sizes), and storage retrieval losses (about 30% loss from lead acid batteries.) This is the demand figure you start with in estimating what size wind generator you need. If a system with this capacity costs more than you can afford, go back and start chopping off toasters, electric element heaters of all kinds, compressor refrigerators, Jacuzzies and well pump motors. (Direct water pump windmills do a better job than electric ones with all the power conversion losses.) When supply and demand are in balance, you puts your money down and takes your chances. Naturally, The adding-on way is best for people who arn't posessed by a lot of appliances in the first place. First, put up as big a wind generator as you can either afford or stand to have around (They make about as much noise as an exposed tree in the same wind, except they have a rhythmical sound, or a car (non-streamlined) traveling at 30-40 mph., minus noise of engine & tires). Get one or two used car batteries and start adding on utilities. Start with florescent lights and stereo which are all the same voltage as the wind generator system, for example 12 volt DC. If there's enough capacity for this, add on a washing machine and an inverter to run the 110 VAC washing machine motor. Match the inverter for output because the bigger the inverters are, the more juice they use, so don't get one bigger than you need. Still have more juice than you can use? Put on a vacuum cleaner, electric toothbrush, electric fish comb, etc.
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Design your storage system around the longest stretch of calm days that your site survey turned up. I used one 100 Amp hour battery in my first system, but there were voltage spikes when the wind gusted, bigger banks or line volt regulators will prevent that. If batteries charge fast and run down fast, add more batteries. If they charge fast and run down slow, add more appliances. If they charge slow and run down fast, dump some appliances. If they charge slow and run down slow, that's as far as it goes.
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The best way to insure your wind machines' continued to service is: Don't think energy dependence or independence is anything absolute or it will crunch you. To set doom and eternity riding on the back of technology is foolish. Why trade dependance on a technological monster for dependance on a technological elf? What I really mean is: laugh & stay loose, diversify, invest, plant early, have kids, you already knew it.
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If you use a 12-volt car battery, don't let the voltage get below about 10 volts. Mount a volt meter right next to your light switch and test it whenever it feels appropriate. Used car batteries are sometimes available from wrecking yards for about $15 to $18 dollars guaranteed to work, but not for as long as new ones.
Deep Cycle batteries are a better choice, but they are more expensive. They can be run down to 3 or 4 volts without too much harm. Used ones are available from golf cart maintenance companies and paraplegic supplies (electric wheel chairs), possibly also from electric fork lift maintenance companies. They are usually returned when they are eight months old and exchanged. The used ones may be good for several years and cost very little, but they may also fail quickly in exotic ways. Get the opinion of the dealer.
If they contain lead/zinc they will last longer but their charge will be slowly tapering off. If they contain lead/antimony they can take repeated quick-charges, (if you expect frequent hurricanes), but fail suddenly. The choice is: bang or whimper. A better battery is nickle-iron, they last 50 years but are big & expensive.
A large new set of Deep Cycle, lead-acid could cost more than $1,000 at 1980 prices, God knows what they'll cost by the time you read this, but I don't advise you to throw your money around like that. A little care will keep you from having to replace them as soon as the warranty runs out.
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To make them last:
- Keep them dry, out of the rain and dew, preferably indoors, but a large box will do, or under the house.
- Ventilate the enclosure: they let off hydrogen and oxygen which will blow up convincingly if ignited. So don't let the gases accumulate and don't smoke around the batteries.
- Don't set the batteries on the ground even if it's dry, make a rick platform of 2x4 lumber so there'll be ventilation underneath also.
- Don't let them freeze. They keep themselves warm while being used, but they won't always be in use. Water freezes before electrolite. When the temperature falls, the charge will too, when the temperature rises, the charge will too.
- This is a trick to double or triple the life of your batteries by removing the sulphur that builds up between the plates, (But it won't work on a dead one).
- Dump the electrolite out into a plastic tub, not metal.
- Let it drain well and save the electrolite.
- Fill the batteries back up with fresh water, rinse and drain.
- Fill them with diesel or kerosene and leave it to soak overnight.
- Drain the kerosene out good and pour the electrolite back in.
- Put a charge on it.
- Keep the batteries full.
- Keep the tops clean.
- Don't wear good clothes, spilled acid is invisible till a hole appears.
Bill Cornelius 1981
If you got this copy off the web:
You owe me $10
or you have to do something good worth $10.
WS Cornelius Enterprises, POBox 57, Albion CA 95410
email: billcor@mcn.org
