I just recently helped a gentleman put together a system with similar requirements. He
had several novel ideas and used only hand tools except for an electric saw and drill. He
took the rear axle from a front wheel drive 1982 Chevy Citation and cut it in half with a
hack saw. He said it was easy and only took a few minutes. He kept the emergency brake
cables intact for later use. He then mounted one half of the axle to a 20 ft. X 2 inch length
of thin wall tubing (from a recycle center at about $6.00), using three U bolts made from
all-thread as his yaw bearing. Next he made a rotating table out of scrap 5/8 inch
particle board flooring material salvaged with permission from a job site. He cut his
table to a rectangle 1 ft. wide and 3 ft. long, reinforcing the underside at both ends and
both sides with 1 1/2 X 1 1/2 X 1/8 inch scrap angle iron salvaged from an old bed
frame, also cut with a hack saw and drilled for bolting to the table. Next he mounted the
table to his yaw hub, centered at one ft. from one end for use as a downwind machine.
He used two 2 1/2 ft. 2 x 6's then glued and screwed them together with wood screws.
He centered these on his rotating table, stood them width wise up so he would have
enough room to keep the other hub over the table with only 1 inch of the hub and the bolts
protruding over the edge. Again he mounted the other half axle with hub to the table using
some more of his drilled angle iron and all-thread clamps, 3 inches from each end and
again in the center.
When he got this far he decided to call on me, as he drives by our place most every day and sees our machines flopping around in the wind.. We introduced ourselves and exchanged some pleasantries he then asked me " is there something I need to know before I make my blades". We had a long discussion of the pros and cons of several different approaches, He had read the "LeJay Manual" so he had some sense of wind. He decided on a two blade rotor for simplicity and reliability. His alternator was from a Volkswagon Jeta. This generator has a rating of 14 volts / 40-100 amps beginning at 2,000 r.p.m..
The bolts in the hub were removed and replaced with longer ones to accommodate the gear up drive and rotor blade assy. Then sprockets were removed from two 27 inch ten speed rear bicycle wheels, of course they were a match. He used two large sprockets aligned and of the same size on the hub, drilled them appropriately and separated with two washers of proper bolt size. Again with two sprockets of the proper size for a 9:1 ratio or near to it, he drilled and mated to the alternator these sprockets with three small bolts to the original pulley in a similar manner. What he did was use a jackshaft. On the brake hub he used two sprockets of 30 teeth attached by chain to a jackshaft With two of ten teeth. Again on the other end of the jackshaft two sprockets of 36 teeth. Now Finally on the alternator two sprockets of 12 teeth. This is not an unusual configuration for a homemade wind generator. In each stage there is a ratio of 3:1, 3 x 3 = 9:1 . A gear ratio 9:1 allows the machine grater ease of starting in low wind regimes.
Never use gear boxes on small generators, they cost too *&%$#@ much! The reason that the sprockets were separated with washers, was to make room for two chains (redundant reliability). He used the original mounting bracket attached and aligned to the underside of the table to attach and adjust his alternator. This approach works very well as less force against the bearings are required than if belts are used. Whenever you use chains on any machinery, watch out! Fingers can now be sewn back on but it hurts a little.
Offered by Jay.
A gear system would last longer. The only thing is a gear system needs to be kept running in oil. This may be a problem after the pole shift. Oil seals leak especially if axles are turn with one side down. Availability of Oil will be scarce. Also, I believe the gear ratios of a rear end axle (if this is what you would use) to be not as high as can be obtained from a car tire perimeter driving an alternators modified pulley. One could use the alternator belt under tension around a wheel rim as a big drive pulley. This would work as long as the belt is long enough to go around both pulleys.
Offered by Mike.