Improved Polycarb Mill

[CmeBREW]

HI Guys,

     Recently, during a big 60mph wind storm, I had thought the bearings finally went bye, bye on my small experimental Polycarbonate (high solidity) 32" diameter "Toy" (DownWind) Windmill here:

http://www.fieldlines.com/story/2009/3/24/2384/94659

Yesterday, I took it down and realized that what actually happened was the 'thrust washer' inside the treadmill motor had ground away and the die-cast flywheel was now hitting the motor housing and thus preventing it from turning. I was glad it could be saved. I also was very surprised the brushes inside were not that worn down after the last 3 years of terrible abuse I have been putting this motor thru. (no furling system in mega-winds) I'm surprised the bearings are still working too.

So I made it where the Flywheel couldn't hit the motor housing, and decided to cut up the 3 round Polycarbonate (3/16" thick) blades into 6 thinner, faster, and larger diameter blades.

Earlier this year I had emailed fellow smart member GHURD and he had told me that 6 thinner, faster blades (instead of 3 big round blades) would make more power.  Now, after changing this mill to 6 thin blades, I just wanted to report that he was correct.

(Even though the blades are still just FLAT and inferior to nicely made Super-fast Aerofoil blades-- this New and Improved "Toy" mill is doing probably twice as good as the previous big round blades)  

Now the over-all Diameter is a larger 43" which can gather a little more power from the wind.  I needed 6 blades to get over the bad cogging of the treadmill motor, and due to the High turbulant location.

Below is the close-up of the 6 blades. Very simple really. I just used a 1/4" NUT under one of the screws to lift each blade to a decent angle. (Sorry I don't know the exact angle. My guess is around 12 degrees??)

Since these blades go somewhat faster now (compared to previous method), I can just leave it hooked up to my 12v 'System' batts-- which is somewhat easier -- because the old slower (3 round blades) mill I would have to hook up to each 6v golf cart battery and switch it back and forth every week or so, to keep the two Batts even.

Also, it is very nice these 6 blades do not make any noise (like the last) even in big wind gusts with no furling.

Anyway, even though this is more of a experimental 'Toy' mill, my original desire was to make a 'Less noticable' mill above one's roof, and it certainly is less noticable. It still reflects some light as it turns for the birdies.  I think it is sorta cool and wanted to share these improved results-- even though it has to be said that super-fast Aerofoil blades would probably go twice as fast as these 6 flat blades and thus make more power. It is a trade-off, 'Looks' for Power I guess.

-Sorry I can't make Videos right now.

Thanks.

[ghurd]

Only a 43" diameter toy?

That's a big motor for a "toy" too!

What If... the blades were buffed with 440 grit?  Stop the glare?

And I think the power would go up considerably with a bit of airfoil-like shaping.

Polish up the angles a bit and the whole thing may disappear pretty well?

I never did get any of that material to try.

G-

[CmeBREW]

Thanks Ghurd-

Yeah, I quess I had a few different things on my mind when I used the word 'Toy'.

I just meant the Watthours compared to a 8 or 10Ft hawt high in the air.

The glare is desired to me.  The reflection is not TOO bad actually (for humans), but good enough for birds to still see when the blades are spinning fast.

You were right (as usual), and like you said, I still do need to carv an aerofoil shape at least on the outter 6 inches and it should really go. Right now they just have a quick bevel on all four edges including the tip. I will do that in a week or so. I would then have to fine sand things back up with wet and dry sandpaper. (400g and then 600g)

This Poly is real tough stuff. Couldn't break or crack it with a hammer over the edge of my bench. And never could bend the stuff evenly with my 1000f heat gun. It can take a lot of heat but won't bend the whole length evenly over a mold. Maybe in a special oven?? I don't know.

Fun to try though.  I'm hoping to break 100 watts with this puppy in a big wind.

Thanks.

[taylorp035]

I have been trying to bend polycarbonate lately for a windshield on a small single person car, and I have come to the conclusion that you must be very, very careful not to heat it too much as to cause bubbles, and an oven would do much better than a heat gun.  I even tried heating a large sheet of aluminum to then heat the plastic, but no luck.

You could also build blades out of carbon fiber, if you want it to have a serious toy that can withstand a F5 tornado, but the tower would need some reinforcing.  Hmm.... Maybe some carbon fiber sandwich material would work better, with the balsa core...

Anyways, good luck hitting 100 watts with your 43" windmill, as that is my next goal with my 48" treadmill motor.

Keep us posted!!!!

[taylorp035]

Also, what are your stats on your motor, like the cut-in rpm, or the rpm/volt and power ratings (amps and watts/hp  and voltage).

Mine are 16.9 amps to 150 volts and 2.5 hp at 27-30 rpm/volt.

[ghurd]

Guessing you had a bit of wind in the last couple days.

Anything to report?

G-

[CmeBREW]

Thanks TaylorP035,

Yeah, that is some tough stuff. The type of Polycarb I used is called "Macrolon" which was extra left-over pieces from a factory that makes 'Machine and Tractor Safety Guards'.

Recently, we got some strong winds (about 10-25mph max gusts) all day and night, and I was watching the Ammeter a few times, and it did 40 watts in about a 25mph gust (best guess).  So I expect it would do 80watts as is, in a giant wind gust (say 40mph) above my turbulant roof-- and when I shape the blade tips better, around 100Watts.  So about what I expected.

Over this recent windy day and night, my best quess is it did about 200 Watt hours into my 12v batts.  Not too bad for my small system.  I probably only use around 300 Watt hours per day anyway.

On such strong windy days and nights I usually will shut my 5' Hawt down (electrically--by shorting) since the (3) blades make too much wirling noise during the biggest gusts and it is too harsh on the tilt back furling system the way it is now.

So it is sorta nice to have this as a little back-up during these Strong windy nights-- since it makes no noise whatsoever.  I also, leave my small 2x3 Vawt running and it did around 100Wh on this recent windy day, which helps out a bit too.  Unless there is mega giant winds like above 40mph, then I tie it down if possible since it don't have a top bearing.

Yes, It is still very satisfiing and fun to get what Power I can from all my small mills running at the same time in these terrible turbulant locations.

The treadmill motor I have is only 5amps. It is that common 260vdc 5100rpm motor many here started out with.  The 12v cut-in is about the same as your nice Treadmill motor -- about 390rpm I suppose.  Yours will do more max power in big winds with those big amps.  That is a nice Treadmill motor you got there for that price.

A 4' diameter mill should be perfect for that motor especially if you can get it up in the air a bit where it is consistent flowing.  The power from mine is always going up and down, on and off, in the turbulance.  But I'm afraid to upset thy neihbors going any higher. They have't reported me yet! And hey, they aren't so perfect either-- I see they just got 4 goats and a bunch of chickens in their little shed. (and they don't have a 'farm'! They better not wake me up too early, or I'm going to put up a 12 footer)

-Thanks again.

[CmeBREW]

Ha-- you posted right before I did. Didn't see it till just now!

Yeah, pretty good winds as you know, since you're about 2 hours down wind from me. Like that.

The report is above-- you read my mind Ghurd right when I was typing it! That was a Bit Freaky. Ha      

-- I will shape the blades better soon (I was impatient again) as you said. I always seem to do that.   -Thanks