Colorado Melons

I’ve been getting asked a lot of questions about the Wind Turbine lately. Friends, neighbors and readers in general are wondering what’s been up with it. Since I’ve formed the blades, next next step will be fiberglassing them before they get mounted to the hub and the hold-up is with that fiberglass work.

My intent was to get the garage insulated, sheetrocked, painted and heated this Winter, but due to my transportation issues, I’ve been unable to finish it.  While I’m not opposed to laying some paint on a firewall in mid-20 degree temps, I’m not about to take any chances with the blades of a rotating wind-driven PMG not curing properly.

I’m still as excited to see it completed as when I started it and after getting the blades on, all that will need to be done is wiring up the rectifier & such and then mounting the machine on a tower.

I appreciate the questions & all the interest and I look forward to posting more progress with it when the appropriate time comes.

Stay tooned.

Having written about beginning the blades in a previous post, I was able to get back to them today and continued roughing-in the front faces of the remaining two. You can think of the taper I’m making as the blade’s “angle of attack” to the wind, in much the same way that an airplane has to change its wings angle of attack to climb.

Although there are probably many different way to do this, you can see that cut slots in the board after laying out my leading and trailing edge lines. The slots connecting the two lines that will form the face.

 

Yes, my saw handle is duct taped together. It cracked when we were using  the saw to completely renovate the Malaga NJ home – during the removal of a beam for a load-bearing wall and the resultant weight redistribution. I could just pick up another handle at a hardware mega mart, but it was my father’s before I got it and although it hangs on the wall, it gets put into service on occasion. Maybe someday I’ll glue the handle back together and paint a pretty picture on the blade and leave it to hang…. and maybe not

After cutting the slots the arbitrary 1″ apart as marked, all that’s left to do was to knock out the kerfs between the slots with a sharp wood chisel, contemplate the universe, and reflect:

and then sand:

For the backs we can use some of the aerodynamic general rules of thumb that tell us, for efficiency’s sake, the thickest part of an airfoil should be 1/3 of the way back from the leading edge. This means that since the blade is 3″ wide at the tip, the thickest part of the airfoil will be 1″ from the leading edge. Making another mark @ the 30″ radius where the blade is 6″ wide, the airfoil will be 2″ back from the leading edge, and so on down the blade…

We also know that for strength’s sake, an airfoil should generally be at least 1/8 as thick as it is wide, but since this was already figured-in when we previously laid out & cut the root-to-tip taper on this side of the blade, we’re just about ready to shape the rear side and then ‘glass each blade.

Alas, I stopped working on these to get to the boys’ basketball practice a little early, giving me some time to watch them. The next game isn’t until 12/5. The blades will be right where I left them, but the boys keep growing and I’m going to cherish every minute of the gift that they are while I can.

I started shaping the wind turbine blades yesterday, after having this project systematically knocked down the “things to be done” list. There are only so many hours in a day and we need to be intentional on how we spend those hours, the hours turning into days, weeks, years, a lifetime and a legacy.

Thanks to the  medium of the Internet and blogging, you can tell at a glance when was the  last time I did something on this, but I had to look back to find out I haven’t touched it much since June of this year. Those hours I just wrote of quickly turned into months.

Having some successful experience cutting large and small props for my hovercraft some years ago, I originally started cutting these blades to shape immediately after confirming the alternator did, indeed, generate useful alternating current. But then I set out to find a quicker, easier way than the last time to make them a reality.  I wanted a more effortless way to remove everything that didn’t look like blades from the blocks of wood, “roughing them in” if you will, the correct shape being finalized with the rotary sander. The hunt was on for a wood-cutting bandsaw that could handle 8″ tall material.

I won’t say here that I was diligent in my search, enjoyably working through the outage projects at work, laying hardwood floor in the house, etc; but five months later, I look back through the realization that if I had started cutting these out by hand back then, I would’ve been done by now. Ever been there? Maybe with saving, investing or from some other seemingly unrelated position in life?  It all ties together. So I started.

Thanks in no small part to the Wright Brothers, we can now take it as a simple fact that the back surface of our blades will need to have larger surface areas than the fronts to create low pressure areas behind, helping them to “pull” through the oncoming wind, increasing unit efficiency.

The fronts then, should be flat but tapered from “leading end” to “trailing edge” into the wind; the backs a functional airfoil tapering to a thin, but not fragile, tip. And since this machine will be safely anchored to my backyard, I’m going to use some simple design generalities and a few accepted aerodynamic structural “rules of thumb”. No need to worry about “accelation vs. cruise”, “climb rate”, or any of the multitudinous other considers otherwise taken into account when designing propellers as long as : the tips don’t go supersonic (mine ~60mph @ cut-in, calc here), they hold together in high winds, and are relatively efficient. Other efficiencies could be better made in the machine itself (and will be on the next), rather than spending more resources on a lesser gain here. “Think: ROI”.

Going by hand, you can see how far I got with the roughing-in last night:

• I’ve tapered the backs of the 3 blades (where the airfoil will be) from the “root” (part closest to hub) to “tip” (farthest from hub)
• Marked out “kerf marks” on all three fronts (the flat side) and cut one to check my “leading edge” to “trailing edge” taper.

I still have much more to do and will be happy to share the particulars of the design and “what’s coming & why” with anyone interested, but parts came in for the ‘58 and I’m going to run out and pick them up while the boys are in school.

More on this soon…

I know I’m jumping ahead with the construction details here, but I’ve been working on a few things and just haven’t taken the time to post what’s been going on. 

It’s 10:30AM and I got home from working my first of four night-shifts about three hours ago. The machine was far enough along the other day that I couldn’t even go into the house when I got home. I went straight to the shop to get it to where you see in the picture.

IT WORKS!
The shutter speed was slow enough to catch the motion but really makes it look like the alternator is spinning faster than it is. You can just about make out my other hand spinning it at the top while Leigh took the photo and I doubt I’ve got it going any faster than 60-80RPM. If I had a tach I’d know for sure, but I wound it shooting for 48V 3PH @ 140RPM (1.4kW) and don’t think I’ll have any problem making that.

I’ve got some room in the air-gap between the stator and the rotors to dial it in yet, but since I’m going back to work tonight I’m gonna hit the hay.

WAHOO! :-D

To see these posts in the same order as the build (from start to current), click the ‘wind turbine’ link on the right.

With the frame of the wind turbine done, it’s time to make the tail boom.

This is the beginning of the tail bearing which will hang on the pivot that is already welded to the back of the yaw bearing. It is made from 1-1/4″ sched 40; is the same length as the pivot (9″); and will be notched halfway-up to fit over the pivot bracket and to allow for a ‘positive stop’ to prevent the tail from swinging into the blades when the machine furls.

Continue Reading »

I had decided in the beginning of this project to save the metalwork for close to last because I knew it would be no big deal to bang-out in a couple of days. Now that I’ve made all the other pieces, it’s time to fabricate the frame of the machine so I can assemble it.

The stator bracket is cut from a piece of 1/4″ plate. The outer diameter is 15″ and the inner circle is 4″. The spokes are 1-1/2″ wide at the top, 2″ wide at the base, and 120 degrees apart. One 1/2″ hole for mounting the stator is on each spoke 13-3/4″ from the center. In the center of the bracket is a 1-1/4″ hole for the wheel spindle.

While I could’ve had something custom machined, I chose to go with standard parts for easy parts replacement & maintenance (bearings, etc). Therefore the spindle is a standard 1000 lb trailer axle piece that I got from Northern Tool. The assembled machine won’t weigh half that and larger ones are available for the next (upsized) machine should this one work well here.

When you get it where you like it, weld it.

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I decided to finsh some details on the stator while I was kicking around the shop today.

The biggest concern when drilling the bolt holes through the stator was to not hit any of the copper coils or internal leads with the drill bit. You can see with the solid green that it could get difficult, but I was successful drilling the three 1/2″ holes 120 degrees apart for the mounting bracket hardward.

The generator terminals will eventually need to get connected to the line so I installed stainless terminal end lugs. The stainless will hold up to weather with no problem, but the main reason for using it is that it’s non-magnetic and I didn’t want them interfering with generation since these will be be in an area between the rotors.

You can see how each phase of the generator output is attached in the photo above and, on the flip side (below) how the line will connect to the opposite side of each lug. It should be an easy matter to hook it up when the time comes.