NA, TOWER, AND SAILS Whea building windmills, always overestimate the strength of the wind and the forces involved. It pays to be safe. “This platform problem is 50 acute that there is a good case to be Technological Self-sufficiency, wobin Clacka faler and Faber UK 1976 ASB 0-571-11057-6 pp 138-141 WIND POWER made for building a tower and not using a mast. ‘Che top platform then adds strength to the tower, and another half-way up as well will help even more. The best design 1 know is for a 26-foot hig tower built by the New Alchemy Institute-East on Cape Cad and fully described in the Journal of the New Alchemists, No. 2. The basic structure is made from 8 lengths of 4. x 2 timber each 26 fect Jong (all timber must be treated with wood preservative}. The 2 platforms arc fixed to the tower by nailing down into short lengths of 4 x 2 bolted to the main uprights (with eye bolts, on the centre platform, to provide a fixing for the guy wires). The NAT wires run inside the tower but anchoring thers outside would in my view provide a better hold. ‘I'he tower is tapered to a shape given by making the top platform an octagon 28 inches across and the centre one 2 circle of 43 inches diameter, 'I'he main uprights are fixed at the bottom with large bolts to 8 bits of telegraph pole 6 Zeet long driven deep into the ground, The top half of the tower is braced with 16 4o-inch lengths of 1 x 3, and the bottom half with 16 sfsinch lengths, Such a tower (this one was designed for a r8-foot diameter sail machine) will give pretty good service. Bits of wood attached up the lec side will make a safe ladder, and some more pieces mounted all round about 3 fect from the top will give an easy toc-hold for working on the machine. If you want even more strength (and who doesn’t!) the price of a third platform will be miniscule and help cut of all proportion to its cost. By the time you've finished, such a tower is going to cost £100 or more, but a metal, commezcially- available model to do the same job will add up to 3 or 4 times as much when you've finished paying for transport and impozt duty and all the other extras people can -nanage to think up. Build your own, Sails and propellers There are two nice things about windmill sails. Kirst, they're easy to make, which means they're also casy to replace, Socond, they’tl never be as strong 2s the rest of your machine. That's an advantage because in 2 gale the sail is likely to gct ripped up first, and oxce that’s happened, of course, the wind machine will stop rurning and no more harm can come to it. A rigid propeller, by contrzst, can goon and on turning ina gale untit the whole machine disintegrates. The sailwing idea has been recently developed by a team of WIND POWER scientists at Princeton University who were struck by the efficiency of a glider. wing, with its blunt, rounded leading edge, The New Alchemy Institme has adapted the idea to make an 18-foot diameter water-pumping mill which works pretty well, even in a very low wind speed. The Princeton idea led to a 25-foot diameter machine, designed to produce 7 kW in a 9 metre per second wind, ‘The leading edge of the NAT sail is a 14-inch diameter steel television mast, while the trailing edge is made from a taut wire or aylon cord. As a result, the shape of tue sail changes with windspeed, to take up the most efficient zerodynamic shape. The sail itself, made from cotton or, detier, dacron {as in boat sails), slips over the steel and nylon cord frame like a sock, The drawing on page 147 shows the essentials. The steel masts are fixed with U- bolts toa r-inch thick triangle of plywood, which serves as the hub, cach side of the triangle measuring 30 inches. The rest is apparent from the diagram. Note the door aprings fitted to give an auto- matic governing device for high winds, These have two positions, one for use in storm conditions. The NAI design has, howcver, come through gale force winds in the normal spring position, I would recommend an additional governing device (sce next section), so I think you could dispense with the storm position for the springs — not a very praccieal idea, in any case, for they involve climbing the tower in a high wind to make the adjustment. ‘This unit has been tried and tested, and if you get into problems write to Marcus Sherman, c/o New Alchemy Institute-ast, Box 32, Cape Cod, Massachusetts, for advice. The NAI machine was for water pumping, so the hub was connected to a crank shaft used to power the pump. Our machine will be an acrogencrator, so We will use a diffcrent system (see below), But it’s worth pointing out how the main disadvantage of sails for clectricity gcacration. The rotor will revolve relatively slowly, and will be far too slow to turn a car elternctor at the right speed. Even with propellers, you need to gear up by about ro to 1. For a sail machine of this type, you will need to gear up 20 or even 25 to 1. But, even allowing for the frictions that introduces, you'll still make more efficient use of slight winds than would a propeller machine. Cutout and Stitching Pattern for Sails ~— ee i cotton or éacron sail fits over Stade frame ltke sock “U" bolts on hub qcornars over mast position nylon cord iscraw hook |}pscrew heok for normal position sh Ty" 10" tubular steel television mast 16" oor spring "x40" spruce dowel boom SAIL-WING DETAILS iad An Advanced Sail-Wing for Water-Pumping Windmills crane siin=T The development of siege windills at New AL chemy was tae by Manzus Sherman, The prototype ‘eat water pumping Wind whieh he had bul Soushern finn 1972 toa tigation Mis inde rill in Moduta ied cloths, bambo sts, tek pole Cote log and um vecne whee (1) tn 1979 Mareus bute similar indmil here un Cape Cod em Posing lath ile ro wich al en ee 9 spring ‘paritd selfeathering mechanism (2), Wehare come Glued co develop che sx-ving windowing i for aquaculture ckeuation and inigeion, and bave four ito be, for our purposes, a wottable and adaptable “Theva pare of dhe sall-wlyg wind the sil blade, whieh consist usualy ofa fabric sutace st ported nya rigid mast, We have used Dacron (Fas Esl serial hecaute of ies strengeh and cyabily Figure tilisrees how che al alipped ono the amit lke a sock and attached tothe movable boom, The boom Keeps the il ar Yer allows i co apt 0 cages the ind. One is ila ee Sra pe and leacheing root ae Mestad, crasKsnaer wits Te sire HEbPRERNE RANE Figure 2 Adame ening Ato Tee Jsma of tbe Nw Alcbemits co cae FE6 me Se a0) Figo Sipe sting Tea one si of de igure 2 shows later version of the suibwing. An cextersion shaft holds the blades furthet from the ‘over. The sll i ited with card ason asail boar, and the tip bracket hasa feathering mechanism, Figuce ? shows how stabilizing cables may be pusitioned prevent flexing of the blades. CRASH ART ye 3 Seabangcabes omeknme ving "The siting indo wih ued foe ci culating aterm the mina i 1974 song fol couse tna theench ete piston pups Snulaneoisy. Egress how the te pumps sere connec ya sivel to the pomp rad The cast iran pumps were expensive, The palo boves on cach wet abit fom pli pois Ui. 3) (3) The daublepumpe vere uadenshed tor he srcngth a he wind weve ated one ease inter ahiger capaci, re compact daphtagm pump which coud be pce low gewod ig 8) (1) Figte shows the bacresice om cach ego he snd owe, was fet prude to stegien the Uwe In urer tv adequate seppere vo te a “Sona! welght of te entlahat, extension, cles and ber hardvate tat ee adeeb Go the -rankshait bearings used in the carly windnulls were adequate fo the lighter (ype of blades, bur cequiced periodic Lubrcation on the Page 25 H N 7 Fig 4 Sai-sng witli hetezee and teu heavier models. Grease ftings are easily pluced in sich beating clamp (Fig. 7). Dating nae starry: peril lasting several days, altiough there Was ao pumpi lond on the windmit, the extended period of high speed turcing eauted the bearing surfaces to wear tticough on dhe lever Made ean Missal balance the weight on each end ofthe crankshaft (6 asingan equal Furees un the bearings "The design forthe latent windmill moving inte the real of a heavy duty, longasting machine. Mer- sil Hall has constructed an experimental sal-wing ‘windril with several new fearuees, The major change is that. Cor the ise eime, the hades face the wind, Prrcionely all of our aait-wings have tailed down ‘wind, 4 cll, narrow vail tracks the blades inte the ind. The main shaft, which lea teerinch Aigmecer, runs in sealed bearings, Fitted to the end of the shaft 1 plate on whieh a pin is Fixed, offact ftom the shaft itr pone 2 eonvert rotary mation of the shaft ince cranking motion required fur the vertical twee] ‘af the pump rod, the sallvlogs ate spring feathered it the Buse uad centifegally feathered at zhe Sp, The results of these most een innovations wall he iscusse ater a season's opcesting experienc. experi pecking befor pion pump, Fine 6 Seeing vind ei dephrogn pap Page 26 oe Josrsoh of te Nes Atcbentias ie \Wintnt heanng towing ve Fangs on canbapt ale 1. Shesma, Sus 1978." Wind io nda” He onal of The Se Alcs 2)" 187 Op 2, Sherman, Moteur 1974. "A Hater Pamping Wide ‘TeetWorke” The Jonrmal of The New Mchemsty (2 Tar. 1. Mosel No. 350 Shall Wall Cate on Cinder ito ell Supply Co under, Wats $18.50, cna, 4. Lang sapactybambopoaod dahrage purge. Rdkon {Cpe 450 indi Park Rc Neve Rao, Pantchus - tont $00 C1973), ~ Parte Barnhart ‘When you've made your sails or propeller you have to fix it to something which will rotate in a bearing which can be anchored to the mast, The best thing is the complete reur axle and differential of a serap car, which can now be obtained very cheaply from a junk yard (sce next sectian), But assuming [or the moment you've done that, you must now batunce the rotor, This is important: if you don’t balance the thing, the vibrations and the uneven weight will certainly be enough to shake the whole contraption loose, Your rotor, electrical equipment and probably your tower will crash to the ground, So balance you must. ‘Any good engineer will tell you you rust balance dynamically that is, when the thing is revolving fast. You can’t ~ it needs com- plicated equipment. So you have to balance statically, which means first setting the thing up with the rotor in a vertical plane and spinning the rotor hard by hand a few times, Watch the point at which it settles to rest. Jf i's always the same point, you are un~ balanced, and you'll have to weight the lighter anus. With a propeller you do this by cutting out an oval shape of metal and serewing it to the lighter blade with the screw offset from the centre, Find the right point by trial and error to serew in, which syill give you rough balancing. ‘Then twist the metal oval round on its sctew to give you fine bulancing, Then tighten the screw, To balance a sail, use your common sense; some pieces of lead flashing cut into thin strips and twisted round the metal strap at the tip of the wing might be good — but make sure they're firmly fastened or they'll come off in 2 high wind. ‘WIND POWER Transmission and governors The problem of how to transmit power ftom a rotating sail or propeller to 2 device for producing electricity can be soived in two ways. You can build a shaft which will turn pulley wheels linked by 2 belt to an alternator, That will take you into buying and fitting bearings and pillow blocks from small mail order firms, or finding the right junk pieces in the right place. Jim Sencenbaugh has built a pretty successful soo-watt aerogenerator in this way and for $15 he'll send you a complete set of plans. They'll take you thtough not only all the mechanical problems, but round the electrical circuit (see below) as well. Even if you don’t intend copying someone else's plans exactly, it's not @ bad idea to get them because they contain many hints which you might otherwise spend much time puzzling over (address: 673 Chimalus Drive, Palo Alto, California 14308). "a Rhe second way of doing it, which I reckon is much easier, is to buy 2 complete rear axle and differential from a junk car dump. If you don’t know much about what happens inside a car, now is the time to find out; the information will not only help you make the windmill, but it'll be very handy leter on if you're still running a car. The beauty of this scheme is that it is cheap ~ and that you can usc a wheel hub to solve your main bearing problem, Leave one hub on, and bolt a plywood plate on which the propeller is mounted to it, You then have to mount the entire axle and differential on a r-inch piece of matine plywood, or a steel plate which is even better, This is the platform which will carry all the gubbins at the top of the machine - notably the axle, the alternators and some electronics. ‘Your second bearing problem is how to mount this platform on top of the tower. It must rotate freely so that the propellet or sail can always face the wind, The expensive way of solving this is to buy, as the New Alchemy Institute did for their sail mill, a steel turntable, For the record, theirs was a model no. Mg-1214 series 1,000 Econotrak bearing (-inch inside diamcter) from Rotek Inc., 220 West Main Strect, Ravenna, Ohio 44266, and it cost them about $129. It's undoubtedly a splendid device but you can do the same thing with snother wheel bub. Ideally, I would buy a serap tractor hub and axle. Disconnoct it from the differential and bolt the differential housing to a platform near the top of the tower. The Bannmatinn far sing VITA £ meter wintest1 Cleotpiv Fover Generation an sem leg \ sem rim rom mh Ast, newrator tinje7n waits automob ite - trangricsion reer axle | ¢ In lou goat 1 to 3 kil ‘biocksd fan pulley belt \ alternator le vane differential DIFFERENTIAL MOUNTING.