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Chadron State College, 2011
A couple weeks ago we taught a workshop at Chadron State College in Nebraska ~ 6 days long.
Nice shop to work in... we had about 14 students. It was me, DanF, George, and Scotty as instructors. They had more tools than we knew what to do with ... although it is a slightly sad state of affairs I think. Here in the US, technical schools seem to be 'downsizing' this sort of stuff. Most of the tools there there pre 1970 (which was fine with me actually). We had a nice mig welder, plasma cutter, milling machine, lathes... way more toys than we needed to build a couple wind turbines.
Pictured above Lisa if fitting magnets to the rotors for the 12' turbine. (it is basically identical to the turbine pictured here at the start)
Hate to make Lisa the 'star' but sometimes it seems the girls work the hardest. Pictured above she's carving blades for the same machine.
It's controversial... I still love linseed oil as a finish for blades though. Cheap, easy... and it looks nice.
Fitting blades to the steel hubs for the 12' turbine.
The 12' turbine is for a 24 volt battery. We wound the stator with 38 turns per coil, using 4 strands of AWG 15 gauge wire. There are 12 coils in the stator so that's something like 96 little wires that needed to be cut, stripped, connected and soldered.
It's always good to have problems at workshops I guess, and prove that they can be solved. We made the stator mold from nice particle board... and lately my favorite mold release has been Crisco. Didn't work... the mold and the stator became one. With hours of soaking the mold in water, scraping with chisels, and drawknives, and a power planer... we finally found a stator inside the mold!~ it was a real PITA. At least we never hit copper with cutting tools....
Pictured above Robert and Mark start assembling the alternator while other folks are chipping particle board away from the stator.
Arghh.... I'll never try to do it that way again!!!!
But some things are looking good.... they did a bang up job of cutting magnet rotors out of 3/8" steel with the torch!
While some are assembling the alternator, others are still chipping away at the stator..., some are carving blades, and others are finishing metal work, which came out really nice!
All the animals were very curious about our activities.
George was lucky to survive this one.
Finally we got a stator to put with the wind turbine.
Finished alternator for the 12' turbine. The goal for cutin was 25 Volts DC at 125 rpm... we were happy when we got 126 rpm. We also built a 10' turbine... and it became clear to me on Thurs night (4th day out of 6) that some work would start drying up... and George might not have much to do in the metal work area... and all the blades were almost carved. At the bar that night we designed a new machine and decided to see if we could maybe get a 3rd machine built in the two days left.
So they started next morning (Friday) to carve the blades. It's a 2 blader... 1 meter diameter, the blade is carved from a 1 meter length of 2x4 and designed to run at TSR7. We layed out 10 stations on each blade so it's a fairly graceful looking thing.
The yaw bearing is made from 12" of 1.25" sched 40 pipe. The bearings will be the same hub we use for 10' turbines (off a 1000 pound trailer axle). Except on this machine the hub is stationary (bolts to the steel doughnut pictured above), and the spindle goes in backwards, and the single magnet rotor is welded to the end of the spindle (which we cut off to be a bit shorter). To furl, the machine will tilt upwards.
George and Chris seem amused by the project anyhow....
At the end of the day Friday we all took a field trip to check out Chris's power system... 2500 Watts of PV with a ARE 110 (12 foot diameter) turbine on a 120' tower, which is off grid and powers his new yurt. Pretty nice system... the batteries and all the electronics for the system are under ground near the foot of the tower in a concrete 'bunker' (septic tank).
There's the Yurt! It's not quite finished yet but close, the power system works... and we spent one night there.
Pictured above is the 10' turbine finished.
There is the little 1 meter turbine coming together on the last day, next to the 10' turbine.
I really did not expect to get the 1 meter machine done, start to finish, in two days. We cast the stator really hot on Saturday (I wanted it out of the mold in 1 hour and it was). Pictured above is the stator, 10" in diameter with 3 coils in it. Each coil has 150 turns of AWG 16 wire in it, and the three coils are wired in star (WYE).
Above is the little machine without the stator installed.
At about 2:30 on the last day we managed to get the big alternator (12' turbine) bolted up to my volvo for some testing. We've done this before... the results were about the same. It works fine.
There is the tiny turbine finished... we quickly sort of checked voltage/rpm but Im not convinced the numbers were right. Looks like it starts charging 12V at about 800 rpm which is too fast.... but later tests suggested maybe it works better. A few more windings int eh coils anyhow - maybe slightly lighter gauge wire might help though. the blades on this are just under 1" wide at the tips and 1/8" thick. It's very tiny....
So we made a stand for it, stuck some big magnets to the bottom of the stand and stuck it to my car for testing. And we ran it up and down the road.... There was a softball game going on right behind us, I hope we didn't distract the teams too much.
Pictured above is the whole group.
Once we got home we did it again for more data. It works pretty well! As it is now, it cuts in before 10mph best I can tell, and is producing about 250 Watts around 30mph, at which point it tips up (it is gravity that it has to overcome before it tips up). There are two small magnets in the furling stop setup in repulsion, so once it tips up power drops off to about 130 watts output, when the wind slows it tips back down again. It's hardly sorted out but it works OK and it was loads of fun!