On Monday we worked on the new 17' machine. We'd finished the stator a week before - Monday we made magnet rotors. Again - this machine has 18" diameter rotors, each with 16 1.5" x 3" x 3/4" thick N40 grade magnets. The stator has 12 coils, each wound with 59 turns using two strands of #14 gage wire. It's going to be a 48V 17' diameter machine which will be grid tied with a small battery bank and an Outback inverter. The fellow who's getting this one bought an 11' machine from us a couple years ago (made with volvo brake rotors) and it's been grid tied for a while - he's doing reasonably well with it I think, averaging about 4KWH/day from it.
George fabricated the main frame for the alternator. This machine is basically identical to Shawns 17' machine except for slight changes in the stator.
I had the magnet rotors made with a hole slightly too small to fit over the back of the hub. We had to turn the hub diameter down slightly on the back side. We also needed to drill out the holes where the studs were to 5/8" to fit the 5/8" threaded rod.
It's not all about wind power up here... yesterday Rich took the steel strings off his base and put on new gut strings! It sounds great....
Lee came up yesterday to build parts for his tower. He got a 10' machine from us a couple years ago. Hopefully it will be installed in a month or so - he's got a very windy site a bit north of here at about 9000'. Before it goes up we plan to rebuild his machine with larger magnets and a lower resistance stator. (Volvo Farmer... we should do this to yours too before it goes up!)
One of the finished magnet rotors. On this machine I welded up stainless steel bands - just a touch smaller than the rotors. We heated them up and shrank the onto steel rotors, and then poured in a thick mixture of vinyl ester - ATH - and chopped fiberglass. Hopefully these magnets won't ever move. I've never had problems with magnets coming out except when a stator fails and they rub the stator. We had to put a band around my 20' machines rotors - and I've had magnets come loose in my 17' machine. I'm hopeful that the stainless steel band will add some insurance.
We decided to put the alternator together yesterday just to test its cutin speed. The back rotor fits behind the wheel hub.
Some of Lee's tower parts. His tower will be 42' high (including the stub). He's building it with 12 gage 6" tubing - the tower top and couplers are made from sched. 40 6" steel pipe which fits nicely over the tubing. We got all the parts done yesterday with the exception of the pivot (we ran out of gas for the welder). It should be a pretty easy tower to assemble
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You'd never have thought that assembling an alternator could be such great fun!
Too bad there's not a nice wind turbine on my tower for this picture! We took Shawns wind turbine down. After opening the airgap last week it's been working very well - it runs just slightly slower than my old 17' machine but it's definitely not stalling anymore. As its setup it furls right around 2KW output - he could add some weight to the tail and get a bit more in higher winds but I'm pleased with it as is. We disassembled it in preparation to put my 20' machine back up soon.
A brand new set of 20' diameter blades showed up right before dark! These ones are nice - there are no scarfs in these ones, Scotty managed to find enough 10' lumber to make them. These blades (like the old ones) are 8" wide at the tips, 17" wide at the root and 3.5" thick (the thickness of a 2x4 because that's what they're made from).
We got the alternator together. 80 rpm gets us 50VDC after the rectifiers - it's about perfect I think. The airgap is right at 7/8" and the stator is 5/8" thick - so we have nice clearance on both sides of the stator. This should be a lot like Shawns (the speed at cutin is about the same) but I expect itll run a bit slower in higher winds. If it tends to stall we'll add resistance to the line. I figure Shawns alternator to be about 50% efficient at 3KW output - this one should be about the same at a bit over 4KW.
Monday hopefully we'll get the 20' machine back on line. Next trip to town I'll get more gas for the welder and we'll finish the new 17' machine and start work on two more 17' machines - one for a neighbor here in the canyon, and another one for a fellow in Wyoming who's also going to be grid tied. That one will live on an extreme wind site - I'm very curious to see how it'll hold up.
