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.

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.

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…

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

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

The notch should allow somewhere between 120 - 160 degrees of tail swing; any less than that and the tail may not fold enough to allow the blades to get out of direct wind. Any more than that and the tail could potentially pitch itself into the rotating blades in the highest winds.

It’s much easier to work on the bench and transfer my marks than it is to try to measure and mark-up the end of a pipe, so I drew a circle the same diameter as the pipe and disected it to find 135 degrees.

Then I stood the pipe on the circle and transferred my marks.

Since I’m going to reuse the scrap that comes out of this notch, I didn’t want to use the torch to cut it. A bandsaw would work nicely here, but I don’t have one and I don’t mind a little workout. ;-)

This is what the notched piece should look like from the bottom.

I need to flatten the scrap piece enough so that its inside diameter will fit over the outside diameter of the tail bearing (the piece with the notch).

Slip the bearing over the pivot and insert a 1-1/4″ x 1/4″ plug in the top – to be welded to the bearing.

The bearing also needs to be turned complete counter clockwise to stop against the notch. This will be the normal (unfurled) position. Tack weld the scrap that we flattened as a reinforcement should the tail come slamming down out of the furled position back to normal.

The tail boom is fabricated from a 5′ x1″ sched40 pipe w/ one end fish-mouthed to fit the tail bearing.

Since the pivot is already at an angle to the yaw bearing / tower, if I make the angle between the tail boom and the tail pivot 90, the boom will actually point downward, kind of limp, and nobody wants that flying high in their back yard… so I’m making it a 110 degree angle and it should point up a little.

It’s a quick but effective fishmouth from the chopsaw and will be a nice fit with a little help from the hand grinder.

Looking down from the top, you can see that I also didn’t point the tail straight back. Remembering that the generator will be offset to one side of the tower by 5″: The force of the wind pusing against the offset generator/blade assembly is going to try to continually swing the whole machine around the tower. To counteract that force, I’m offsetting the tail a few degrees out of parallel with the wind direction.

Side View

Here, in the furled position, you can see I’ve added a lower gusset to support the tail and a ’stop’ that will hit the yaw bearing to prevent the tail from contacting the blades.

It furls up nicely and gravity should have no problem bringing it back to ‘normal’ when the wind subsides.

Back to ‘normal’.

I’ve added a verticle 1″ x 1/4″ x 34″ piece of flat 9″ from the back to attach the tail ‘feathers’ to the boom