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THE S-ROTOR AEROTURBINE

Aeroturbine (air-turbine) is a term that is used here to define the entire unit that converts the kinetic energy of the wind into the mechanical energy of a rotating body. The aeroturbine described here is multi-tiered (three S-rotors stacked vertically in tiers) with each S-rotor oriented 60° out-of-phase with the others (see Fig. 6-1).

The stacking arrangement resulted from an invertigation into how the machine could be enlarged (to intercept more wind) without sacrificing integral strength. The out-of-phase orientation (of the tiers) resulted from a close look at a problem which plagues a single-tier, or basic, S-rotor; if the wind momentarily; died, the S-rotor might come to rest in several positions (relative to the wind's direction) where it would not restart easily (under load) as the wind came back up.

These positions are expressed by the gaps (indicated by arrows) in the torque curve for the simple (or single-tier) S-rotor (see Fig. 6-2) ; three S-rotors stacked 60 out-of-phase eliminated these gaps (or positions).

This chapter will describe three different models of S-rotor Aeroturbine----Model A, Model B, and Model C.

Model A is the aeroturbine that was described in Mother Earth News #26; it uses 55-gallon drum halves for wings (we shall refer to them as impellers).

Model B differs from Model A in that it has a skeleton-type structure (within it) to provide the strength and rigidity that the 55-gallon drums give to the completed Model A aeroturbine. It was made this way in order that lighter, modified impellers might, as they were developed, be used instead of 55- gallon drums.

Where Model A would require complete disassembly to incorporate the new impellers and some additional bracing, Model B would allow the exchange while it was still in an upright, operating mode, without disassembly and without further bracing.

Model C is the same as Model B except that it may be mounted as illustrated in Fig. 6-11; Model A and Model B require the support assembly illustrated in Fig. 6-10.

FIG. 6-3

These three models have their similarities and their differences; within the sections (listed below) their similarities will be discussed within the text (or under Design Notes) whereas their differences will be clearly indicated within each section under the listing of Model A, Model B, or Model C.

This is to avoid confusion; once you have decided which model best suits your situation, you will be able to quickly reference through each of these sections and find what information is required to complete the construction of any one model.

The essential parts of a three-tier, S-rotor aeroturbine are:

These are, as well, the alphabetical listings of the sections within this chapter. Section G -Decisions- will aid in making the final decision and provide cost analysis. Section H will outline balancing methods for the aeroturbine while Section J will discuss spoilers for high windspeeds.

SECTION A----END CAPS

Design Notes:

The end caps serve several functions; they provide (1) increased performance of the aeroturbine by preventing spillover (and loss) of wind captured by the impellers, (2) an easy means of securing the impellers to the aeroturbine assembly, (3) an accurate means of orienting the impellers 60 out-of-phase, and {4) an accurate means of locating the center of the aeroturbine (which aids in balancing the entire assembly).

The diameter of the circular end caps is dependent on the size of impeller used; for 55- gallon drum halves, this diameter is 48" (Fig. 6-3 describes the correct positioning for 55-gallon drum half-type impellers).

Two 48" diameter circles can be cut from one 4'x8' sheet of plywood (2 sheets are required as 4 end caps are used). The thickness should be at least 3/8" (1/2" is recommended); however, don't exceed 1/2" unless you want an unnecss^arily heavy aeroturbine.

A 48" diameter plywood circle, 1/2" thick, weighs 20 lbs and with 4 of them, that's 80 lbs. Add that to the 17 lbs per drum-half (with 6 impellers, that makes 102 lbs) and you'll have a 182 lb aeroturbine, minimum!

Plywood circles are available in various diameters but I recommend that you cut your own from 4'x8' sheets. Why? To make a 48" circle on the sheet you have to rotate a pencil-string combination around a centerpoint (located 2' from one end of the sheet and midway between the sides, as in Fig. 6-4). The accuracy of the final cut is not too important but having that centerpoint is! Store-bought, ready made, plywood circles are not only more expensive but they don't have that centerpoint, and accurately locating it is a job!

Drawing, Marking, and Cutting the End Caps

Don't be tempted to first complete one end cap and then use it as a template for making the others. Because of inaccuracies in drilling and the problem of accumulated error, this is not advisable unless you are fully aware of the implications.

(1) accurately locate the center of the 4'x 8' sheet (see Fig. 6-4) along its length (points B) and across its width (points A); then find points C. Connect these points as shown in straight lines dark enuff to see clearly.

Where they cross at the centermost point is point D ; the centers of the two circles are at points E. Drive a tack or a small nail in at points E and point D. Mark all letters within the circles (as shown in Fig. 6-4) on the plywood sheet.

(2) make up a pencil-and-string apparatus (as in Fig. 6-5) and loop the end of the string over the nail (or tack) head at point E. Wrap the other end of the string around the pencil as close to the lead point as possible and allow it to slip until its taut and adjusted to exactly 2 feet (24"); then tie it, checking to be sure it doesn't change as you knot it (get it right as you will use it repeatedly).

Get the string taut, keep the pencil perpendicular to the sheet, watch the nail end (to see that the string loop slips easily around the nail or tack) and swing the pencil around. Get the line dark the first time (use a soft lead) and sharpen the pencil for each circle. Do both circles on both sheets.

(3) to help orient each tier of impellers 60 out-of-phase with the others, the line connecting points F must be formed. Slip the loop of the string off the nail/tack at point E and put it over the nail/tack at point D.

You can swing a complete circle (lightly) or just stretch it to where it intercepts the perimeter of the circles (as in Fig. 6-4); that point ( F) will be 60 from the A/D line. Mark the point clearly and draw a straight line from that point (F) thru the center (E) and to the edge on the other side.

Do this for the other circle; the plywood sheet should appear exactly like the illustration (Fig. 6-4). Do this as well for the other sheet (and its two circles).

(4) cut the circles using a hole saw, jig saw, or saber saw. In a pinch, a hacksaw blade wrapped at one end (for a handle) will work; it is admittedly slow, a bit dangerous, and tedious, but a greater teacher of patience!

(5) once all 4 end caps are cut out, you have one more line to draw; this will be a reflection of the 60 line that you've drawn on the front (FT). At points F, extend a line across the thickness of the end cap to a point on the other side. Then, with a straight edge, connect these two points in a line on the back side of the end caps.

(6) a centerhole (at E) must be drilled in all 4 of the end caps; the size of this hole depends on two things: the size and the type of rotor shaft (these are discussed in Section D of this chapter). Both of these factors depend on which aeroturbine { of the following three) that you decide to build; procedures for making the end caps used on each are as follows:

Model A -

the size of the hole at the centerpoint of the end caps ( points E) will have an I. D. (inside diameter) equal to the rotor shaft O.D. (outside diameter) used. The rotor shaft should just fit ( snugly) through the end cap. Take the time to insure this happens; the quality and precision of the work here will save a quantity of work when it comes time to balance the aeroturbine. A good procedure is:

Model B -

same procedure as Model A

FIG. 6-5

Model C

- the hole for the outermost end caps (and at the centerpoint) should be twice the diameter of rotor shaft used. The two innermost end caps will be drilled to fit the bearings that are recessed into them. Use the procedure for Model A to drill the pilot holes and final, sized holes; do not drill these holes, however, until the holes for the skeletal members are located and drilled (see Section E in this chapterand the procedure description, for Model Ct in that section).

Arranging the End Caps

Arrangement of the end caps is necessary for final aeroturbine assembly; if the end caps are properly positioned, the tiers will be 60 out-of-phase and the impeller positions will be easily marked on the end caps. It's advisable to use some kind of numbering system here; most of the parts should be interchangable but a lot has to be accounted forhand drill inaccuracies, work interruptions, accumulated error, material variations, etc. so play it safe and don't try to keep it all in your head.

(7) arrange the end caps so that the sides with the three lines (and all the letter markings) are facing you (as in Fig. 6-6a); make sure you have them all exactly as in the drawing.

(8) now, grab the one in back (farthest from you) and pivot it around until it looks like Fig. 6-6b. Now mark them 1,2,3, and 4 as shown. Anytime that you have to 'arrange' the end caps, they should appear like they do in Fig. 6-6b.

Aligning the End Caps

Alignment of the end caps correctly positions them for final assembly. This will serve two purposes:

(9) rotate the arranged end caps (Fig. 6-6b) until they are aligned; they then should appear exactly like Fig. 6-6c.

(10) the end caps should be protected from weather; they may be stained or coated with some type of wood sealer and/or painted; a quart of (oil-base) paint and a gallon of thinner mixed together makes a good sealer. Insure that all identification marks are still visible if the end caps are coated before final assembly.

SECTION B-----IMPELLERS

Design Notes:

Impeller is a word that 1 will use to define the wings, drum-halves, or whatever name might be used to describe the sections of the aeroturbine that actually capture the wind's energy. In this book, I will describe 55-gallon drum halves; this, however, is not the only type of impeller that can be used, nor is it the best. At the time I began designing my first aeroturbine (a Model A), the steel drum-halves were chosen because of their availability and their strength and rigidity. I was very unhappy with their weight but, at the time, the other factors won out.

Since that time I have completed the construction of an S-rotor aeroturbine that permits an easy exchange of impellers (a Model B); the design of this new aeroturbine is different from the first in that it employs a skeletal member (or inner framework) which provides the strength /rigidity that the drum-halves would have provided in the first aeroturbine.

Any device that aims to provide the best extraction of the energy in the wind must provide the best ratio of lift to drag. Lift in an S-rotor aeroturbine is determined primarily by the type of impeller ( shape, aerodynamic curve, etc.) while drag is determined (primarily) by the weight. To improve performance, therefore, the lift can be increased or the drag reduced { or both may occur). The new impellers (that we will install in our newest unit -- a Model B) will reduce drag (because they are lighter) and increase the lift (because they have a better curve and shape).

They do not, however, necessarily provide the overall rigidity and strength that the aeroturbine needs (1) to keep from 'twisting' (from top to bottom) and, (2) to stay together in extremely rough weather. Strength is needed for this, and is provided for, by use of the skeletal frame; water pipe and floor-mounting, pipe flanges are used to separate the end caps and hold the aeroturbine assembly together (whether the impellers are in place, or removed).

Note:

Both kinds of aeroturbine are presented. The Model A requires the rigid impeller and it is non-skeletal; Model B and Model C are both skeletal and employ a removable impeller. I recommend the Model B to experimenter and non-experimenter alike. Why? The Model B may cost more than the Model A (it uses more parts) but it is more flexible and will be more efficient (if lighter wings are eventually used). While both the Model B and Model C offer this advantage over the Model A, Model B is less expensive and far less difficult to construct, balance, and erect than the Model C.

We are continuing work on the lighter, more aerodynamic impeller for use in the Model B. Its construction, for the experimenter, will allow use of materials other than heavy steel (as in the drum halves). As this will certainly improve the aeroturbine's efficiency, realize that you don't have to complete the aeroturbine (or even start building it) first; spend the time getting materials----batteries, control system parts, etc. and determine the site, build a tower, etc.

If you decide to build the Model A, or to use the drum-halves for impellers (until the information on these lighter impellers arrives) in the Model B or Model C, here's the procedure:

Selecting the Drums:

It is important to find three (3) 55-gallon drums that are identical: same height , width, and weight.

(1) weigh and measure the drums before you buy (or use them). If they have junk in them (dirt, oil, etc.), remove it so the weighing is accurate. If some have tops and others don't, this will throw off the weighing, so account for it. If they are all the same color, markings, etc., weighing may not be necessary but take the height measurement anyway; you'll need it later. Be sure to write it down!

(2) the drums can be without ends; these will be removed anyway. If the drums are badly dented or bent, don't accept them (I've never seen one not dented but I'm referring to a whole side being crushed in!). They can be lightly rusted, but plan to use a wire brush, sandpaper, or steel wool on them because it is advisable to paint them (after they're cut), and they must be quite clean before painting.

Marking the Drums:

The drums must be split lengthwise into two, equal sections (and the top and bottom, if any, removed); this is most easily done with an acetylene torch. If you don't have a torch (or a friend that does) have the drums cut at a shop. If you get them cleaned and marked before you take them in, you'll save money (because the shopman's time is your money) and you'll get a better job done.

Remember, the final product will be rotating, and unequal impellers means an unbalanced aeroturbine. It's a tough job to balance a completed S-rotor aeroturbine, so the balancing should be done by preliminary, and very careful, workmanship during construction.

(3) all drums have one seam and that's where the initial cut will be. The other line (for the other cut) must be drawn on the opposite side of the drum; to locate its position, I used a piece of string { about 35" long), measuring first one way, and then the other around the circumference (as shown in Fig. 6-7). Take your time and get it right; if the drum has dents, avoid them, or the measurements may be off). Do this at first one end of the drum, and then the other (I even did it at the midpoint of the drum); mark these clearly { pencil or nail scratch).

(4) use a yardstick (a 55-gallon drum is only 35"-36" long) and make sure it's straight (check it ! look along its edge to make sure it's not warped) and line up with the two (or three) marks you've made, connecting them with a pencil line, or a nail scratch, or whatever's visible. If you scratch the metal (and not just the paint), it can probably be seen as it is being torched, but if you've used pencil or chalk marks, you have to do better. If the torchman can't see the line clearly (the torch's flame will burn off pencil or chalk marks), he's going to get off and-----bing----you've got unequal impellers.

(5) a standard procedure for "set-up" (getting something ready to torch) is to make 'notches' (or indentations) with a centerpunch (and hammer) about every 1/2" along the line to be cut. One tap from the hammer will penetrate the steel and that's good enuff (you don't have to drive it all the way through!). You won't have to do that on the side of the drum with the seam because the torchman can see that, but be sure to tell him he must cut it right on the seam!

Also, let him know what you are doing and what it's for (you might offer to share the plans with him, and get the drums cut free!). The important tiling is all the time you spend in "setting-up" isn't going to be worth very much if he's sloppy, or can't cut a straight line. The cut drum-halves will have rough edges-----that's normal. Grinding them smooth is tedious work but don't bother with it unless you're worried about getting cut (while handling them); they can be covered with tape to avoid this.

Incidently, jig saws can be fitted with metal-cutting blades and, I suppose, used to cut the drums if torching is out of the question (too expensive, or not available); judging by the thickness of the metal, it'll dull the blades pretty fast.

(6) one important thing to do before cutting the drums is to mark the two sections (to be formed by the cut) of each drum in such a way as to insure any drum-half can be re-united with its original mate and that both will be oriented in-the same way (top and bottom). I used different numbers for each drum, written near one end, halfway between the two cutting lines (to insure the torch didn't burn them off).

Cutting the Drums

(7) if you're cutting the drums yourself, set each drum (in turn) between blocks (or whatever); they are under tension, so they will 'pop' apart at the end of the cut (on one side). They won't pop very much, assuredly, but if ya aren't expecting it, it might startle you (and you might proceed to burn the sleeve off your shirt, or the arm inside!).

(8) wirebrush or sandpaper the drum-halves (after they've cooled) and paint them first chance you get (or you'll have some more rust to scrape off). If you have to paint over your identification marks, immediately re-mark them!

Final Preparation:

(9) one remaining job is to get the drum-halves ready for mounting on the end caps; this requires six (6) L-brackets per drum-half for the Model A and, if used, four (4) for Model B and Model C (see Fig. 6-8a).

(10) drill 2 holes (for each L-bracket) in the drum half; use the bracket for a guide. I secured my brackets withpop-rivets but bolts may be used instead. In several cases, I used small, metal washers to 'shim-up' the L-bracket wherever the drum's metal lip might have caused the unshimmed bracket to 'lean in' to the drum at an angle (see Fig. 6-8b). The brackets may be made from 2" by 1/2" flat-stock (scrounging around or behind a metal-supply store or talking to a shopman might get you some surplus metal so you can make them yourself; mine were * store-bot').

Woodscrews may be used to secure the L-brackets (and drum-halves) to the end caps; if you're using an end cap that's 1/2" or thinner you might have to use small bolts. Don't drill any holes, however, until final assembly is in process; after the drum-halves are positioned ( according to Fig. 6-3), a pencil can be used to mark the holes (using the L-brackets as guides) and the end cap removed for drilling or for making a starter hole (for screws).

(11) it might be easier to mark the positions for the impellers (on the end caps) before assembly; study the drawing of final alignment and positioning (Fig. 6-6a,b,c, and 6-9) and then mark these positions on the end cap. This will be necessary because the drum-halves (when used) will have spread apart after cutting (they were under tension, remember?) and they will have to be compressed a bit before they are completely bolted/screwed down. I did this by first bolting/screwing down the innermost L-bracket (on the side of the drum closest to the center of the aeroturbine) and then, I sat on the outermost portion of the drum-half, got it to align with the mark { where it should be) and then bolted/screwed it down; of course, I 'sat' on the aeroturbine when it was on its side. As well, this was a Model B; the procedure might be a little bit more difficult for a Model A, rigid impeller < without a skeletal frame).

Note: If you have a hard time compressing the drum half and getting it on the mark, then forget it; bolt/screw it down the way it is. It's not going to interfere with the efficiency of the aeroturbine that much, but if you can't get them all at the proper mark, the aeroturbine will be out of balance. So . . . compress and get all of them at their respective marks (compressed) or make new marks (uncompressed) and bolt them down where they are,all the same.

SECTION C-----BEARINGS

Design Notes: The bearings used in the S-rotor aeroturbine should meet the following criteria:

Two types of loading are imposed on the rotor shaft and, hence, the bearings. The first is radial loading (forces acting perpendicular to the shaft) and this comes from the (1) wind itself, trying to turn the aeroturbine and (2) tension imposed by (and at) the gear train (where the generator hooks up to the aeroturbine). The second type of loading is axial (forces acting parallel and along the shaft); because the aeroburbine turns about a vertical shaft, this force is gravitational, or that produced by the weight of the aeroturbine itself.

The bearings should be sealed if they are to withstand exposure to the elements.

The bearings should be flange mounting; this is simply a housing for the bearing that permits bolting of the housing (and, thus, its bearing) to a flat surface (like wood).

The bearings should be eccentric locking; setscrew locking is okay, but the collar that is locked to the rotor shaft is secured much more evenly by the eccentric method.

Lubricated for life-type bearings, in my opinion, are not as good as the type you lubricate yourself. The top bearing is not going to be that easy to get to, but the difficulty will depend on what kind of aeroturbine support assembly you decide to build. We are presently using Browning FB-250 bearings.

If we were going to continue using impellers that are 55-gallon, drum-halves (and not replace them with lighter impellers), we would have to use an FB-900 (or its equivalent) on the bottom. The reason? Our present aeroturbine weighs 250 lbs. and that's quite a load for a ball bearing (like the FB-250); replacement of the impellers, however, with lighter ones will bring the weight of the aeroturbine down to 160 lbs. and the FB-250's might take that (and we can take their cost $7.00 per bearing).

The FB-900's are timken taper-roller bearings but, while they are real beefy, they cost $25.00 apiece. If you are going to build the Model A aeroturbine, you'll need at least one (for the bottom); the top bearing can be on FB-250.

There are, of course, many other manufactured bearings that meet the requirements; they may be less expensive than Brownings are. If you are into some experimenting along this line, try the bearings found in the rear-axles of junk cars especially Fords and Chevys. Mounting them may be a problem, but experimenters generally thrive on that kind of challenge.

How and where the bearings mount depends on what kind of model you are building. Again, when you have made this decision, you will mount them as follows:

Model A

- the bearings here are mounted on the wood crosspiece of the support assembly and 2 will be required. One must be equivalent to a Browning FB-900 and it will mount on the lower crosspiece; the other will be a Browning FB-250 (or equivalent) and it will mount on the upper crossmember. Refer to Section F support assembly for the mounting of these bearings.

Model B

- same as Model A (above), except that the lower bearing may be the same as the one used at the top (an FB-250), if lighter impellers are used.

Note: A Browning FB-250 (or equivalent) should be able to handle the load but it's almost borderline (as to the weight it will take); our present unit has not been operating long enough to accurately say that it will take this stress for any extended period of time. There is no doubt, though, that the FB-900 can last a long time.

Model C

- the bearings here must attach to the end caps but 4 are required all together. Two will be housed in flange blocks and bolted to the outermost (top and bottom) end caps. A Browning FB-250 (or equivalent) is recommended for the upper end and a Browning FB-900 for the lower (see note under Model B above). The other two bearings must be mounted to the other end caps (innermost) but they must be recessed into the holes in these end caps so that they do not interfere with the mounting of the skeletal-member flanges.

Note: I am not recommending the Model C unit to the inexperienced or the unskilled. Section D rotor shaft will reveal some of the problems I encountered in the construction of this model, one of which is the installation of bearings in the unit.

SECTION D ROTOR SHAFT

Design Notes:

The rotor shaft is the axle (and pivot) of the aeroturbine; depending on which model you use, it can be a "live-axle" or "dead-axle" type.

Model A:

This aeroturbine uses a 'live-axle' type rotor shaft and the term means just that the axle is alive, or moving and rotating as part of the aeroturbine; the rotor shaft is locked to it. The bearings for this kind of rotor shaft must be mounted in a framework (see Fig. 6-10) which is held in place, or upright, by guy wires.

FIG.6-10

Model B:

Same as Model A (above)

Model C:

This aeroturbine uses a 'dead-axle' type rotor shaft and, here the rotor shaft does not move; rather, the aeroturbine rotates (or moves) about it (the rotor shaft is pre-vented from moving). The bearings, in this arrangement, are mounted on each end cap of the aeroturbine. This reduces the need for a frame and allows attachment of the guy wires directly to the top end of the rotor shaft (to hold it upright, as in Fig. 6-11).

My own experience with both of these arrangements leads me to vote emphatically in favor of the live-axle (Model A & Model B) arrangement. As this is the only essential difference between the Model B & Model C, this is a vote against the Model C. The only simple thing about the Model C aeroturbine is the way it looks. Unfortunately, it seemed rather simple to build at the time I wrote my first article (which was published in Mother Earth News, issue #26) on the S-rotor aeroturbine and, as Model C was easier to draw than the support assembly required for the Model A or Model B, it was the one depicted in the drawing for the article. That was Nov. of 1973, and to date, it has caused us considerable grief. Why? Let me count the ways!

There are more objections to this model, but they are more situational; if I had a better-equipped shop, I might be able to minimize the accumulated error that pipe flanges, warpage, etc., seem to add to all the above listed problems. I am intrigued by the possibility of this type of mounting but I must admit that the energy is not there to further work out these problems at this time. If any of you decide to tackle it, I'd like to hear the results. Good luck.

The Rotor Shaft

The rotor shaft can be constructed in a number of ways. The simplest way is to use a long section of round bar stock (cold-rolled steel, see Fig. 12-A). This costs about $1.25 per foot and it comes in 12' lengths. As the minimum length of the rotor shaft required is 10* (the aeroturbines described here are 9' long), I recommend buying a full 12' long piece. Why? It's easier to work with, gives you clearance for the gear train, and it's nearly the same cost as a 10' section (since you not only pay for the length, but also for having it cut).

Another way to make the rotor shaft (see Fig. 12-B) is to buy a long section of pipe (which is only 6S?/ft.) and insert two smaller sections of round bar stock in each end (for the bearings). I tried this first, incidently, and don't recommend it. The pipe has to be seamless (you can't use water pipe), so that the round stock and pipe rotate concentrically.

Even with seamless pipe, the round stock goes in too easily and the 'slop' has to be "shimmed-up. " As well, the biggest problem is securing the round stock inside the pipe without changing the O.D. of the pipe {or it will not clear the holes in the end caps). Besides, by the time you add up the lengths of pipe and round stock required, the all-round stock shaft is only $3.50 more; the problems and extra time weren't worth the "savings" of the pipe/round stock rotor shaft; our newest rig runs only round stock.

Securing the Rotor Shaft

Again, once you've decided on the model of aeroturbine to build, you will use one of the following procedures:

Model A

-as the rotor shaft must be secured to the aeroturbine in this model, a method of doing this is required. One that is particularly strong is a short-nipple and flange (water pipe, 4-hole floor-mounting type) assembly (see Fig. 6-13); two will be required, one for each end.

(1) obtain a 5" nipple (water-pipe type) with an I.D. equal to the rotor shaft O.D, (so it fits over the shaft).

(2) cut this in half (only one end will then be threaded); this will form the nipple for each end of the aeroturbine.

(3) drill both nipples in two places and tap (thread) the hole for a standard-size setscrew.

(4) insert the 4 setscrews.

(5) screw each nipple-half to the same size flange and see that they fit the rotor shaft, making sure the setscrews aren't causing interference.

After the aeroturbine is completely assembled, and the rotor shaft is inserted through all the end caps, continue with the procedure as follows:

(6) slide the nipple/flange assembly onto the rotor shaft at each end (flange toward the end cap); slide it until the flange is securely resting against the end cap. Using a pencil (with the flange holes for a guide, mark the location of the 4 bolt holes on the end cap.

(7) mark each end cap and nipple/flange assembly so that it will be replaced on the same end (of the aeroturbine ^ and precisely as it was marked. Remove the nipple/flange

assembly.

(8) using a drill guide and a bit the same size as the bolt that will just fit through the flange's bolt holes, drill out these holes (at each end).

(9) remount the flange/nipple assembly, line up the notches, and bolt it to the end cap; do the same for the other end.

(10) at the end of the aeroturbine designated as the bottom, the shaft should stick out twice as much as it does at the other end (upper); if you have a 12' shaft, then the lower end will be sticking out 2' and the upper 1'. If you are using an 11' shaft, it will stick out 15" on the lower, 9" on the upper. You need more at the lower end because you have a gear (or two) to install; but you need at least 9" at the upper end. Incidentally, you are measuring these distances from the end cap, and not from the end of the nipple/flange assembly.

(11) once the rotor shaft is positioned, tighten down the two setscrews on each nipple/flange assembly.

Model B

- securing the rotor shaft to the aeroturbine here is the same as in Model A except that steps 6, 7, and 8 are not required. As this model uses a skeletal member, the holes will have already been drilled in the end caps. This was necessary to installing the skeletal member (see Section E - skeletal members - and Fig. 6-14). Steps 9-10-11 apply.

Model C

- the rotor shaft in this model does not lock to the aeroturbine but the flange mounting block for the bearings will. Try to get one that has the same hole pattern as the skeletal member flanges have (see Fig. 15).

SECTION E-----SKELETAL MEMBERS

Design Notes:

The skeletal member was introduced in our 2nd aeroturbine design (described as Model B) to provide: (1) easy exchange of impellers while the aeroturbine was upright and (2) strength and rigidity in the aeroturbine so that a lighter, less-rigid impeller could be used. The skeletal member is nothing more than sections of water pipe with floor-mounting pipe flanges at each end (see Figs. 6-9 and 6-16); these fixed-length sections then 'space' the end caps apart, a distance equal to the height of the impellers.

As the flanges (4-hole type) are bolted to the end caps, this provides a rigid skeleton which can be balanced and raised to (or lowered from) its operating stance with or without the 6 impellers attached; when 55-gallon drum-halves are used as impellers, their removal from the aeroturbine eliminates much of the manpower otherwise required to raise, lower, or move it because it's 102 lbs, lighter!

The length of the pipe sections (with flanges attached) used in the skeletal member is determined solely by the height of impellers used; if a steel drum-half is the desired (or selected) impeller, the overall length of pipe/flange section (from flange bottom to flange bottom) will be the height of drum half this will be 35"-36" (depending on the drums used).

The pipe length itself will be less than this height as the flanges do not allow the pipe threads to screw in all the way (see Fig. 6-16). Most hardware stores that sell pipe will cut it to the desired length and thread both ends; sometimes the flanges will screw on quite a way and sometimes they will not you might check them.

Constructing the Skeletal Members:

(1) the best procedure is to determine the height of your drum halves (all 6 should be the same), and have one pipe section cut that length minus one inch (1"); then have it threaded at both ends and screw a flange on at each end. If it's still too_ long after tightening them down (more than 1/2"), have them cut a little more off at one end and try again. Remember, it's better to have it a little long than to have it short; if it's short, you won't be able to get the impeller between the end caps. Once you get a good section length, cut the others; check them, too.

(2) mark the flanges and pipe used for one section in such a way as to insure you don't swap ends putting them together after you've pulled them apart. As well, use a different number or color so that you don't exchange flanges with the other pipe sections.

The size of pipe and flanges used in the S-rotor depend on the size of rotor shaft O.D. and the model built. With both of these decisions made, you will use one of the following procedures:

Model A

- does not use a skeletal member.

Model B

- the pipe and flanges used in the skeletal member will have an I.D. equal to the rotor shaft O.D. (i.e., a 1" rotor shaft will use 1" pipe and flanges). Make sure the flanges are a 4-hole, floor-mounting type. You will need three (3) sections of pipe and six (6) flanges.

Before these can be mounted:

(1) the pipe sections must be cut to the proper length (see preceeding text this section).

(2) the end cap center holes must be drilled (see Model B procedure in Section A - End Caps).

(3) the end caps must be arranged and aligned according to Figures 6-6A, -6B, and -6C .

(4) now, insert the rotor shaft through the end caps, installing the skeletal members as you go; the flanges should be on each pipe section and the whole assembly tightened down to the impeller height.

(5) line the floor flanges up with the crosslines (D-A and C-C, see Fig. 6-4) so the bolt holes in the flanges are centered on these lines.

(6) run a pencil around inside each of the 4 holes in the flanges on one side of the end cap only; once the holes are drilled, the flange on the other side should line up also.

(7) notch the flanges with their respective end caps and disassemble the end caps, skeletal members and rotor shaft; make sure you keep the skeletal sections in their respective positions (per tier, and as you marked them).

(8) lay each of the end caps flat as you drill out these holes. It is imperative that you use a drill guide to get a hole which is absolutely perpendicular to the end cap, select a bit that will make the holes slightly larger than the size of bolt which will just fit through the flange holes. Do all the end caps (but don't do them more than one at a time).

(9) reassemble the aeroturbine's end caps, rotor shaft, and skeletal members and match the flanges up with the holes and their marks. (Everything's carefully marked, right?)

(10) once the end caps are properly aligned, slip bolts through the innermost end caps; the bolts must be long enough to fit through the flanges on each side and, of course, the thickness of end cap. Tighten these bolts evenly (as you would when putting on a tire tightening them progressively tighter as you go around, or across).

(11) insert the nipple/flange assembly on each end of the aeroturbine and put bolts through the flanges on each side of these outer end caps.

(12) position the rotor shaft (measured as indicated in Section D) before tightening the set-screws in the nipple/flange assemblies.

Model C

- the pipe sections used in this model will have an I. D. which is twice the O. D. of rotor shaft used; i.e., a 1" rotor shaft should use a 2" pipe (and flange) for the skeletal member.

a) before you drill even the pilot hole (for the center-hole), use a compass to draw a circle that has a diameter equal to the distance between opposite bolt holes in the floor flanges to be used (center to center). Where the circle intersects the crosslines (D-A and C-C see Fig. 6-4), you will drill a hole large enough for a bolt that fits the flange holes. Use a drill guide.

b) drill the center-holes in the end caps. The outermost end cap holes will be drilled the same size as the pipe used (which is about twice the size of rotor shaft). The inner end cap center-holes will be drilled to fit the bearings used; remember that these bearings must recess in the end cap and not interfere in any way with the floor flanges.

c) if the outer bearings (and their flange blocks) have been carefully selected, their mounting holes will be the same as those of the floor flanges used in the skeletal members (See Fig. 6-15).

d) mount the flanges to their respective end caps. Insert the rotor shaft through the inner bearings and then add the skeletal member's pipe sections.

e) arrange the end caps (Figs. 6-6A and -B) and align them (Figs. 6-6C and 6-9).

f) install the impellers, checking to insure you use drum-half mates and that they're both oriented the same way; step #11 in Section B Impellers gives procedure.

SECTION F----SUPPORT ASSEMBLY

Design Notes:

The support assembly holds the aeroturbine in its operating mode (upright). It consists of two parts: the lower and the upper support.

The lower support assembly for the aeroturbine must:

Supporting the aeroturbine fully is more critical; three (3) forces will tend to topple the aeroturbine: wind, weight, and centrifugal force (if the aeroturbine is unbalanced). Obviously, all can generally be accounted for at any one location, aeroturbine, etc. Suggesting a means of insuring adequate aeroturbine support for all locations and situations is a bit difficult to do; an effective design for hurricane country is a bit like overkill (and overspend) for an area which does not experience such maelstroms.

All models of S-rotor aeroturbine require an upper support assembly. Model A and Model B use a frame-and-guy wire upper support (See Fig. 6-10) while Model C may use only guy wires (see Fig. 6-11); remember, however, that a Model C is not recommended.

Installation Site

The S-rotor aeroturbine may be mounted (1) near the ground, (2) on a roof, or (3) atop a tower.

The ground installation is probably the easiest to construct but undoubtedly is the most difficult to properly locate. The people who have aeroturbines (like props) on tall towers don't put them there for the challenge or the thrill in climbing to such heights; they are simply using the towers as a vehicle to get the wind machine (a) clear of surrounding trees, buildings, etc., and the turbulence, or low wind conditions, they create, and (b) to intercept wind of a higher velocity (relative to that found at ground level) and thus, generate more power (see data sheet 1 chapter 7 on wind and height).

At ground level (or above it), the S-rotor aeroturbine does have an advantage over the prop-type aeroturbine; it can operate in this turbulent area without experiencing extreme vibration hazards. Both will suffer from the low wind, so if a ground installation is the only choice, know where your wind comes from (its most frequent direction) and avoid getting it close to obstructions which lie in that direction.

Make an all-out effort (the old college try) to have the lowermost portion of the aeroturbine (bottom end cap) at least six feet (61) above highest ground (Fig. 6-10 shows 2' but it's a basic drawing -- right?) Get it higher than 6' if you can afford (or find) the wood or metal for the framing and support the higher, the better.

FIG.6-17

Fig. 6-17 and Fig. 6-18 show one way to build the bottom support so that the aeroturbine can be inserted into its frame horizontally and swung up into a vertical position; this will insure a safe raising (if the support is firmly guyed down) because it will be difficult for the aeroturbine to topple to the side (because of its 2 pivot points). As well, the upper support assembly (and the aeroturbine) is prevented (by the lower support assembly construction) from further travel after it reaches a vertical attitude; it won't just keep going, falling to the side opposite from where it started. Bolts may be quickly slid through holes in both the upper and lower support assembly to hold the aeroturbine in place once it is upright (see Figs. 6-17 and 6-18).

FIG.6.18

The lower support assembly is, as indicated, also guyed down; this serves to keep it from slipping (or tipping) as the aeroturbine is raised (or lowered). As well, it makes the entire assembly more rigid which will help dampen any vibration experienced in first tests, or in high winds. It is not impossible that vibration in the support assembly (in a heavy gust) could cause the aeroturbine to do likewise; if the aeroturbine is close to its upper operating RPM's, the resulting oscillations could be disastrous.

A rooftop installation is a good second to a tower and certainly better than a ground installation. A lower support assembly similar to the one used for the ground installation will work; it may have to be slightly modified, of course, for a sloping roof or for straddling a roof's peak.

The lower support assembly should be secured, as with the ground installation, by guy wires; they may eliminate the need for actually securing the assembly (with bolts, screws, etc.) to the roof. Wherever it is finally located (on the roof) check the roof support or you may end up having the entire assembly join you in bed some windy evening.

A tower installation would, as aforementioned, be the best situation but, unfortunately, it will be the most difficult. I haven't done this myself but I have figured out the way I'd do it when I find a tower (see Fig. 6-19). Raising the aeroturbine to the top of the tower would be the biggest problem and securing the thing into its support assembly a close second. I wouldn't raise it as a complete assembly but would assemble it up there. Here's where a Model B wins out over a Model A; the removable impellers would greatly improve the situation.

The Upper Support Assembly

The type of upper support assembly used with the aeroturbine depends on the model used. Once determined, its discussion/construction is as follows:

Model A

- the upper support assembly here will be part of the lower support assembly; it is best described as a framework of metal or wood in which the aeroturbine rotates. The bearings for the aeroturbine are secured to its upper and lower crossmembers.

(1) the top crossmember will be longer than the lower crossmember by twice the width of the vertical frame members (see Fig. 6-20); it will rest atop these vertical members whereas the bottom crossmember rests between them.

(2) the lower crossmember must be at least 4-1/2' long; the aeroturbine is 4' wide and you should allow at least 3" of gap between it and the vertical crossmembers on both sides.

(3) once the two crossmembers are cut to their proper lengths, accurately locate their center points; do this for their length and their width (see Fig. 6-21).

(4) center the bolt holes in the bearing's flange block over the lines you've drawn to find each of the crossmember's centerpoint. Then mark (with a pencil) these bolt hole positions on the crossmembers. Remove the flange blocks.

(5) using a drill guide and a drill bit larger than the bolt that will just slide through the flange block's bolt holes, drill out the 4 holes in each crossmember.

(6) Now drill out the center-point of each crossmember; make the hole at least 2 times the diameter of rotor shaft used.

(7) mount the flange blocks to their respective crossmembers to insure they fit; then, remove them for safekeeping.

Construct the rest of the frame assembly; the layout of Fig. 6-20 will assure a rigid structure. If you've had experience in building (i. e., are a structural engineer) then you'll understand what has to be supported and how; there are many possible variations. If you don't have the experience, stick with the outline (in Fig. 6-20) as this provides the essential support criteria; the frame should be rigid entirely of itself. The guy wires will add to this rigidity but don't expect them to replace the frame. If you cut corners here, you'll pay for it in worry some night when the wind is really howlingl

(8) the upper and lower crossmembers should be secured to the vertical frame member with two wood screws (the ones with hex heads) on each side.

Finish making and guying the lower frame assembly, and when all is in readiness, proceed as follows:

(9) slide the upper bearing onto the shaft at the top of the aeroturbine; face it so that it may be mounted to the upper crossmember (underneath), but don't lock it to the shaft yet.

(10) lift the aeroturbine over the frame assembly (which is horizontal) and slide the lower end of the rotor shaft through the center-hole in the lower cross-member until the upper end of the rotor shaft clears the upper crossmember; then put the upper end of the rotor into the center-hole for the upper crossmember.

(11) slip the upper bearing along the rotor shaft until it rests against the crossmember; align the bolt holes in the bearing flange block with those in the crossmember and slip the bolts through. Put on washers, lockwashers and nuts; then, tighten them.

(12) the lower bearing mounts under the lower crossmember; slide the bearing onto the lower end of the rotor shaft until it rests against the crossmember, align the bolt holes and slip the bolts through. Put on washers, lock washers, and nuts; then, tighten them.

(13) slide the rotor shaft until its upper end rests flush (and not sticking above) the top of the upper crossmember.

Now, lock both setscrews (or tighten the eccentric on the bearing) into the rotor shaft. As well, tighten the setscrews (or eccentrics) on the lower bearing. The shaft should now only rotate and not travel up or down!

(14) slide the aeroturbine until it's centered between top and bottom cross-members in the frame assembly; you may have to loosen the setscrews in the nipple/flange assemblies (that lock the shaft to the aeroturbine) to do this.

The aeroturbine can now be raised. The transmission (sprocket/chain, pulley/V-belt, or gear/gear belt) can now be installed, as well as the generating equipment.

Model B

this aeroturbine model uses the same support assembly as Model A (above); begin procedure with #1 (under Model A, above); all other steps are as above, in Model A.

Model C

there is no 'upper' support assembly for this model, except that given by the rotor shaft and guy wires. Although it is possible (and recommended) for a frame assembly like that used for Model A or Model B to be used here. If it isn't used, the guy wires should be affixed to a flange/nipple assembly at the uppermost end of the rotor shaft. The lower end of the rotor shaft should be secured into the lower support assembly but with the ability to be pivoted as the aeroturbine is raised to a vertical, from a horizontal, position.

SECTION G FINAL DECISIONS

As the bearings and rotor shaft for the S-rotor aeroturbine are the most expensive (or least available as scavenged material), it is probably best to start with these two when making decisions. If you acquire the bearings first, the rotor shaft will have to be selected to fit them.

It is recommended to use at least a 1-inch (O.D., outside diameter) rotor shaft for Model A and Model B; Model C should use at least a 1 1/2-inch shaft (and bearings).

Selection of the model of aeroturbine to build is the major decision; as previously indicated, I recommend the Model B. It is not unlikely that we will eventually develop an impeller that is strong enuff to replace the 55-gallon drums required for the Model A but still lighter than the steel drums; this would eliminate the weight of the skeletal member (even though it accounts for only 20-30 lbs. of the aeroturbine's weight). To date, though, the Model B offers the best versatility: changeover to lighter impellers without disassembly of the aeroturbine.

In each section, specific information pertaining to the model selected is listed under the headings bearing the model number. Do not, however, fail to read the text in those sections as it contains information on all models, necessary for the completion of any one of them.

The parts of the aeroturbine end caps, impellers, bearings, flanges (water pipe, floor-mounting type), nipples (water pipe), 3' pipe sections, round stock (for the rotor shaft), woodscrews, 2 x 4's, bolts, guy wire, turnbuckles, setscrews, etc. will depend on the model built, the size of rotor shaft, bearings, etc., and the type of impeller used. Once you have decided on the model to build, you should read through the sections, make further decisions, and compile the list of parts you'll need to acquire.

Let's do an example.

It is difficult to draw up a parts list for the aeroturbines because we have 3, and some other possible variations within each.

Supposing a 1" round stock rod was selected for the aeroturbine, 1" bearings were purchased, and this is a Model B, a parts list might be:

A. End Caps

B. Impellers

D. Rotor Shaft

E. Skeletal Members

F. Support Assembly

SECTION H-----BALANCING

As aforementioned, the easiest (and best) way to balance the S-rotor aeroturbine is by careful, preliminary workmanship in the preparation of the essential parts and actual construction of the final assembly. I cannot emphasize this enough . The S-rotor aeroturbine might not, therefore, require any balancing (whereas a propeller-type will, no matter how carefully constructed) because it will rotate quite slowly (compared to the prop-type). Do not, however, delude yourself into thinking it won't need to be well balanced; there is quite a bit of weight to the S-rotor aeroturbine and it doesn't need much imbalance to begin the vibrations that are the 'death throes' of any type of aeroturbine!

No matter how careful the workmanship, slight imbalances are possible, so at least the balance should be checked. (See Fig. 6-22.) The completed S-rotor aeroturbine should be laid on its side with the projecting rotor shaft at each end resting in the bearings (which are attached to the upper and lower crossmembers) which, in turn, are resting on some kind of support (which allows the aeroturbine to 'clear' the floor and spin freely).

Once the aeroturbine is mounted in this fashion, it should be given a slight 'push' to start it spinning. Wherever it stops, in some way mark it (at its lowest point) so that, after you 'spin' it again, you'll know if it does (or does not) stop in the same place again. If it doesn't, mark the second place it stopped, and spin it again. If it misses both marks, you have a well-balanced aeroturbine.

Most will not be so lucky; the aeroturbine will probably stop at the same point (on the second spin) as it did on the first spin. The next thing to determine is how badly is it out of balance ?

Watch the S-rotor as it spins, especially as it begins to slow down and before it reverses itself. If it starts slowing down and speeding up, then stops, reverses itself for a full revolution, and stops, reverses itself for 3/4 of a revolution, it's pretty far out of balance. A slight imbalance will cause very little reversal (and only a quarter of a revolution, or so, if it does reverse).

Whether unbalanced only slightly or greatly, correcting the imbalance can be done in two ways:

The second is a far better method than (he first; you still don't know how much weight to add nor do you know if more than one point is out of balance. So, use some clothespins and attach them to one of the innermost end caps on the high side of the aeroturbine (see Fig. 6-23). Spin the unit. If it comes to rest on the old mark, it's not enough weight (add more).

FIG. 6-23

If it comes to rest with the clothespins on the bottom, it's too much weight (remove some). If it comes to rest at a new place not the old mark and not at the clothespins shift some of the clothespins to the side to compensate. It would appear to be far more complicated than it really is if I tried to tell you how to shift the pins or how many to add; just experiment you'll get the knack if you pay attention to the result of whatever you do.

You want to get it to the point where it doesn't stop in any particular position with the least amount of clothespins attached. After all, they will have to be replaced with an equivalent amount of weight at the same spot they're located now. The weight can be just about anything as long as it can be screwed, glued, or otherwise securely fastened.

Once you've carried out the additions or subtraction of materials to balance the aeroturbine, recheck the balance. This will suffice for the time being. If you find, in preliminary tests of of the aeroturbine's operations, that it wobbles or shakes violently at low windspeeds, set up the procedure again for static balancing (Fig. 6-22) and recheck the balance.

SECTION J: - SPOILERS

It may be necessary, in some locations, to provide a means of protecting the aeroturbine against high rotational speeds resulting from strong wind conditions. The various means available for aeroturbine control are covered elsewhere - but the subject of this section will focus on spoilers.

Even our latest aeroturbine does not employ a spoiler (although it is protected by electrical braking see Aeroturbine Control, Chapter 4) and, as also indicated, we would not be able to test any of the possible spoilers for the S-rotor aeroturbine, for we lack (in our location) both the frequent high winds and the extremely high winds of some areas (hurricane country).

However, this is not to say that we have not given serious thought to spoilers for the S-rotor aeroturbine; for those who are inclined to experimentation, we offer this information.

(1) As indicated in Section A of this chapter, if it were not for the end caps, the aeroturbine would 'spill' a large amount of the wind it captures; this, then, is one way in which the aeroturbine's efficiency may be spoiled.

Fig. 6-24 illustrates one way the end caps might be 'opened' up under high-speed conditions; a sliding flap could be held closed by a spring for normal operating RPM's but (if properly adjusted) would stretch with increased centrifugal force on the flap (as the RPM's went higher than desired) allowing wind to spill through the slot.

(2) As the S-rotor aeroturbine is essentially an 'impulse-turbine,' its efficiency could be spoiled by misalignment of the impellers; Fig. 6-25 indicates one way this might be intentionally accomplished at high RPM's (in high wind). The innermost edge of each of the impellers might be attached to a spring (as shown) and tensioned to allow the impeller's outward movement under high wind, high-RPM conditions.

(3) If a portion of the impellers were to open under high-wind conditions, this would certainly spoil the efficiency of the aeroturbine; Fig. 6-26 shows one way this might be accomplished. In this arrangement, some means of limiting the distance the flap can travel (when it opens) is recommended. Adverse wind conditions and the specific location of the flap itself (in the impeller) might keep it from closing when the windspeed falls below the w indspeed required to activate it, or damage the flap if it flaps back and forth when activated,

If you decide to experiment with spoiling for the S-rotor aeroturbine, please contact us if you develop anything simple and effective; via the newsletters we send out, it would reach a lot of folks.

IMPELLERS

Okay - now you can see what we are doing in this area. But maybe you have been patiently awaiting impeller curve information your skeletal S-rotor frame is just sitting there, waiting for its impellers. Well, if you won't use the 55 gallon drum halves, then try a lighter material and temporarily shape it semi-cylindrically.

The most important change you can affect (in replacing drum halves with higher performance impellers) will be one of decreased weight; in the lift/drag ratio, weight helps determine lift and shaping affects drag (these associations, incidently, were expressed in the reverse in the book sorry!). I might have to eat these words at some later date but it rings valid (with my intuition and experience to date) to say: Reducing the S-rotor aeroturbine weight will provide the most notable increase in power from it) whereas re-shaping the impellers will only squeeze out a few more watts.

We're not convinced that this is true (or we wouldn't be testing re-shaped impellers) but we're realists,too. Many of the models we will test have been tested before (we do not believe they were tested under exacting conditions); this does not mean, however, that we believe we will achieve phenomenally different results. And for the ones that we will test (that we believe we are the first to test), we just don't know. So little appears known about the parameters of an S-rotor; a friend's recent computer analysis was unable, when provided with everything known about the S-rotor, to put forth the design for an optimum impeller curvature or spacing. So it's back to the GGM (guess-and-golly method).

One alternative to aluminum (for the impellers) is sheet steel; I honestly don't know how thin they make it, but you'll want the thinnest (and yet still somewhat rigid) that you can find. It will weigh more than its aluminum counterpart but it will be cheaper, easier to work with, very strong, and weigh far less than 55-gallon drum material.

While most sheet-metal working shops have a bender which will uniformly contour an impeller to the desired radii (or diameter) inserts or ribs of the type illustrated in Fig. 1 can be fashioned and the sheet metal bent over them to give the desired shape. These ribs should be used whichever way you do it; they will prevent the centrifugal forces (exerted on the impeller at high rotational speeds) from severely distorting the shape of the impeller and thereby damaging it, or adversely affecting its performance.

One advantage in not having the impellers contoured (by a bender) is that they may be later reshaped into another curve (which may be found more efficient) by merely substituting the present rib with one similarly fashioned. Stay versatile it saves time and money!

In addition to testing the impeller shapes marked A thru D, we will (for each of these curves) vary (1) line offset, (2) impeller depth, and (3) impeller overlap. New curves and further testing will be generated from an analysis of the test results.

FIG. 2

Still another alternative to the sheet metal, aluminum, or drum halves is cloth. Generally this material will be stretched over some kind of framework as it will not have intrinsic, self-support properties; it may then, be doped, resined, fiberglassed, or otherwise treated to give the complete frame-cloth assembly both rigidity and weather-protection. Wood, metal or aluminum can be used for framework. Our newest S-rotor (see the MAXI-ROTOR section) will use corrugated aluminum impellers over which we will stretch cloth.

One final point on impellers: We have had some feedback on securing them to the end plates and the consensus seems to be that the screws pull out and the bolts sheer off. We haven't had any problems with our aluminum job, but then it doesn't experience the forces a steel-drummed S-rotor will. So don't get chincy on those lock washers and bolts, or screws. Make them large, strong, and get them tight (check them once in a while, too). Don't be afraid to use more of them. And install a keeper (like that shown in Fig. 1); it will take up some of the strain caused by centrifugal forces and prevent impeller deformation at high RPM's.

THE VAW:

Some notes on Orienting, Governors, and Support Assembly VAW Orienting

Vertical axis windplants do not require wind-direction orientation; they are omni-directional; this may be thought of as being oriented into the wind irrespective of the specific wind direction. However, if a venturi shroud (or wind focuser) is used with the wind machine, a tail may be required to keep it properly oriented.

VAW Governor

A good governor mechanism for a vertical axis machine is not an easy thing to come by, at least not for the S-rotor type windplant. A centrifugal unit coupled with the impellers or blades will help somewhat but there is really no direction to orient them in which they won't be affected by wind action . With the Savonius type, this represents a genuine problem; many designs have been offered but none tested to a satisfactory or publishable state. Here the Venturi shroud might come in handy in itself, however, as a windblock.

One truly intriguing idea, other than those offered in Wind and Windspinners, is to have the impellers fold in on themselves and create a cylinder of sorts. Manual shut-down represents more of a problem because you can't side-face the machine into the wind. A trip lever might allow full activation of a normally activated centrifugal governor but I'd work with separate units one for automatic and one for manual; if one fails, you've still got the other.

VAW Support Assembly

The VAW's tend, because of their lower efficiencies, to be physically larger than the horizontal counterparts. There will be an optical illusion as well; the HAW blades (if of the high-speed type) appear very thin but many people do not realize that at operating speeds these blades are moving so fast so as to appear, to the wind, to be a large circular wall. The VAW, on the other hand, will generally expose a lot of frontal area (unless it's a Darrieus type); a 1500 watt prop-type windplant may only have a 14 foot diameter blade but an equivalent power Savonius rotor would be 18 feet tall and about 8 feet in diameter. The point (before we forget it all together) is that the support assembly for the VAW will be much more involved than the HAW.

Becuz of their need for support at both the top and bottom of the main shaft, VAW units are difficult to mount as high as the comparable-powered HAW. Fig. 7-1 illustrates the way it can be done on a conventional tower but we've lately come to the conclusion that it's better to "tailor" the tower to the machine than vice versa.

Given the versatility of the octahedron-segment tower, we designed one to fit our newly-designed 18-ft by 8-ft Maxi-rotor (see Fig. 7-2). By building the rotor inside the tower, it's easy to reach all of the main shaft bearings and to otherwise service the rotor. A real bonus is that the top of the tower can still be used for a conventional HAW. I'm sure that there are other answers to the problem of how to get the VAW "up there", so use the ole noggin.

HAW and VAW Generators

There are some essential differences in the generator requirements for the HAW and VAW; this could be best expressed as a difference in the operating position of the generator itself and perhaps the normal operating speed. Let's take 'em one at a time.

The HAW will usually employ a generator which has its shaft also horizontal; this will allow a more efficient and easier transfer of power from the aeroturbine to the generator (if the shaft is not outright one in the same between the two). The VAW will also want the generator shaft

to be parallel to the aeroturbine shaft, so it'll be mounted vertically, with its shaft perpendicular to the ground. Not hard and fast with either, though. I've seen some HAW's using a car axle to transfer the power to a vertical shaft so that the generator can be mounted at the base of the tower (beware of leaking oil). And some VAW drive shafts are coupled to a 90 gearbox so the generator can be mounted horizontally.

I don't necessarily recommend either, . . but because there are very few generators designed for vertical mounting,a 90 gearbox is quite understandable and probably necessary. If you want to mount a generator or alternator vertically and it's designed to be ( or is normally mounted) horizontal, understand that you might burn out its bearings and otherwise damage it. Know what you are doing.

Any type of aeroturbine (whether a VAW or a HAW) will rotate over a range of RPM. The bottom end will be zero (unless you've perfected a perpetual motion machine) and there's a design RPM beyond which damage or destruction is a certainty. Somewhere in between these two is the normal "operating" range and this will be on the lower end, the cut-in speed (where the wind-plant begins charging) and on the upper end, the cut-out speed (where the governor activates to limit generator output). If you averaged the operating ranges of all the different types of HAW,

and then did it for the VAW, you'd probably find a higher value for the HAW than the VAW. So, generally speaking, the VAW will require a lower-speed generator than the equivalent HAW. I reckon that's the same as when MAW SAW PAW RAW in the DRAW and figured it was against the LAW. If gears are used (instead of direct-drive), this won't necessarily be true,but the whole idea is to use the minimum gear ratio (or no gears at all) and employ a slower speed generator.

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