12 Watt Mini me Mill

[CmeBREW]

Hello Friends,

      Thought I would share this Micro-generating 3' diameter PVC mill I finally finished. It was my very first tiny alternator I made 2 years ago when I was just beginning to learn about RE.  The link is here, but now I know a heck of a whole lot more!

http://www.fieldlines.com/story/2007/1/14/21729/9348

Some of you might remember it.  After making it and testing with my big drill and seeing the low power (due to the very Tiny magnets) it made, I got discouraged with it and put it in my closet until now.

Now I know that it is not so bad of output actually for a first (single phase) alternator, so I made 6 pvc blades for it quickly and epoxied the rotor on.

I sanded the 5/8" shaft some with sandpaper and put 20min epoxy on and carefully pushed the treated plywood rotor on. Then I tip the whole mill over while the epoxy is setting to prevent epoxy from running down into the bearing. After it sets, I then fill in and seal any tiny cracks by putting super glue on the other side as the photo shows. Don't forget to SEAL THE WOOD in the 5/8" hole with epoxy or super glue and let it dry BEFORE you epoxy the rotor to the steel shaft. If you don't seal the wood first, a lot of the epoxy will soak into the plywood and decrease the strength of the final adhesion. For these Mini mills, I believe epoxy will hold fine and for a long time since they are SPEED orinated and little torque. I have already done previous experiments. I actually had to DRILL the last wooden rotor off- since the hammer would not even break it off!









The Yaw axis is very simple. Just a long 3/8" bolt and grease inbetween a couple of washers. I use a lockwasher inbetween two nuts to keep it locked in for easy turning.

The bolt that hangs down goes into a hole I drilled in the main post- and then use 4 wood screws to hold that small piece of 2x4 down into the main post.

I know it is not much. But today was decently windy and it has been very consistent averaging about 2-4 watts (3 watt aver) into my 6 volt golf cart batterys about 80 percent of the time in a very horrible and stop and go turbulant location only 7' off the ground.  What is great about this homemade alternator is it has NO cogging and mega easy starts with the low-friction bearings. (I thinned the grease in them with a few drips of 80weigh gear oil- He-He)

Yes, In about 12 hours it is doing about 30 Watt hours--which isn't exactly chicken feed for a small RE-system.  If you made 3 or 4 of these little decoration mills, it would be quite good for a small system on a sunless, gloomy day I can tell you! (Perhaps good for residential areas)

The location is bad and the cut-in is TOO HIGH for a 12v system. It does up to 12watts into a 12v battery, but probably 80 percent of the time it is below the cut-in point and doing nothing into the 12v battery.

This whole thing is really just an experiment for me to get 'a feel' for a small mill as to how it does in a very turbulant, low location with 6 blades.

The reason is I am currently making a MUCH better 3' "Yard decoration" mill that will should do twice the power and the alternator will be half the size.  Also, the blades are invisible Lexan plastic.  It has to have 6 blades for the "Dutch windmill" look to it.  This new Mini-mill will be for 12v batteries with a lower cut-in.

Anyway, I am glad I finally finished Mini-me-Mill, and am very excited about the new and improved version coming SOON!

-Any comments or questions welcome.

Typo fixed. TW

[CmeBREW]

Goof:

"The location and the cut-in is too low for a 12v battery system."

Meant to say:  The location is bad and the cut-in is TOO HIGH for a 12v system.  And I might add that the 6 blades slows it down quite  a bit, but there is absolutely NO noise coming from it even in big wind gusts. Strange actually-- but me like that!

[ghurd]

Pretty cool!

What is the 12V cut-in?

Any plan to tinker for 12V?

Maybe a 120:24V 1A transformer... or something...

G-

[wooferhound]

I keep thinking that I want to make a Stepper Motor Farm over here, I have more than 10 great steppers from many different printers. A stepper motor is just flea power but if there are enough fleas, then you will have a whole dog.

[CmeBREW]

Thanks Ghurd,

Yeah, this is just temporary for now. This one will go back into the closet forever when the improved purdy (Downwind)version is done. The new version is a lot different anyway. (Probably the only thing similar is it will be 3' diam)

Something I failed to mention is I had to break this alternator back apart 2 years ago and separate the mag rotors alittle further because they were so close to the stator that one of the rotors began to hit the stator at a point.  What a pain in the neck that was!! (the rotors were EPOXIED on)

Thats a lesson for anyone trying this method. You got only one chance to get it right or instant headaches.  Have a decent 1/16" mag to stator gap- don't just use a piece of paper.  The new version has much bigger magnets (1"diam. 1/4" thick) so I can have a safe gap and still get decent power. (8/6  3-phase / 20ga wire)

Nevertheless, when I had to separate them, it made the alternator even weaker and now the 12v cut-in is somewhere around 400rpm just like Ameteks.

I am aware of how fast a 3 blade 3 footer normally goes. (well over 1000rpm easy)

But I am trying something different.  Something that is slower and quieter (lower TSR), that will be more consistent in a high turbulance location like on a roof or on a 10' pole as a Yard decoration.  (Difficult to explain until you see it)

These 6 pvc (6"diam pipe) blades are obviously very slow. They have somewhat blunt edges.

I am sure if I were to put this Mini mill up higher and had 3 high speed wood blades on it , it would do MUCH better, probably over 20 watts in big gusts--but very noisy.  But that is not what I am trying to do right now.  I am trying to make a small controlled, quiet mill that most 'normal persons' will not even know it generates a little electric.  The New version is exactly like the axial mills, just much smaller, thin, and with no cover like the one shown above.    We'll see.

I doubt I will mess with experiementing with a small tranformer or capacitors see if it works better for 12v batts.  This first one was just a good learning experience.

Now comes the FUN.  

[tecker]

rrrrrough

[lglagasse]

Nice Job CMEBREW:

What was the diameter of the PVC Pipe that you made your blades from? They look cool.

Is there a way to charge 6 v bats, then transfer to a bank of 12 volt Bats without blowing up the 6 volt bank.

Nice Work.

lglagasse

[CmeBREW]

Thats a good idea Woof!  You need to start getting your neihbors USE to the fact that you are a "Windmill Nut" by putting up numerous 'Decoration mills' even if they don't generate any electric. (No wires temporarily-hehe)

You could be like that lady on "Twister" with all the metal 'noise maker things' in her yard, except your thing is little windmills.  After a year or so when the neihbors are Use to your little windmill farm, THEN you can hook up the wires hidden in the pipe. (I am trying 2" pvc pipe with 1.5 pipe inside it as a mill post)

Just have to furl or something to control the noise in big gusts.

Those stepper motors would be perfect for 'Decoration mills' -use 4" diam pipe blades (6), around 2' diam. - (I wish I had now)

It sure seems that 6 blades does better than 3 in a very turbulant low location. It just turns slower but more consistent.

[CmeBREW]

Those blades were from 6" diam pipe. But I wish I had used 4" since it is thinner walled.  The trailing edges on my blades are blunt (squared off) and thick (3/8") and no doubt cause a lot of drag.  

Even though this little mill is temporary, for now I just hook the two wires to each 6 volt battery one at a time, even though they are still hooked up in series for 12 volts. Then later I switch BOTH wires to the other 6v batt.

I wear safety glasses when I switch it, but if someone had to do it, you can always wire up something AWAY from the batts to do it easier and safer.  I monitor the voltage on each battery to keep them even.  

[ghurd]

Before it gets relegated to the closet, cut the blades down to 26~28".  See what happens.  Maybe take 3 blades off?

It just needs the RPM.  It doesn't need the swept area.

I don't think it will make enough noise to notice.

Can't wait to see the next little one.

I am working on one for a HF garden tower, about 25" dia.  Been too cold to touch metal.

Epoxy troubles.  Nice to hear I am not alone.

G-

[CmeBREW]

Good idea Ghurd- I was planning on doing that:

Today was windy again, and I tested it with only 3 blades (Simply took off 3 of the pvc blades and re-balanced), and Wow,  it SUCKED!!

80 percent of the time, it was still under the 12v cut-in.  Many times it completely stopped, often stayed stopped, slowly was turning (even in decent enough low wind), and took a long, long time to 'take off' again to decent a speed. And it did not stay at a decent speed long.  

It was strange, but the 3-blade speed was not much faster than the 6 blade.  The pvc blades must be so slow, that even the 3 blade couldn't even fly out of control. It never even made any noise. The max power of the 3-blade was only 12watts just like the 6-blade!  It makes no sense. It was balanced fine.

In this particular choppy, stop and go turbulant low location, 6 blades were probably 10 TIMES better! (into 6v batt/ around half speed cut-in;around 200rpm)   I am sold on 6 blades down low, or on roofs, with small mills. The difference was like night and day.

I doubt 3 blades would have put 5 stinkin little Watthours in the batts all day long at this bad location.  

After watching it for hours, I couldn't take it no more--so I put the other 3 pvc blades back on (total of 6 again), and it took right off and started putting a very consistent 3 watts average into the 6v battery.

I also believe I will put 5 blades on the bigger 5 foot windmill in the background.  

I am very glad I did these tests. It is very interesting for my new (turbulant area) mini-mill projects.

I hope to get 2-4 times the consistent power with my new 12v version.

I hear that Tomorrow we might get close to Hurricane 1 winds. (71mph+)

I'm going to see what this little baby can REALLY do in this turbulant location into a 6v battery!  -Burn baby, burn!

[ghurd]

That ruined my morning.

How well do those bearings spin free?

Lot of grease drag?

I need to check the weather more often.  Frightening wind.

G-

[CmeBREW]

Ha- Sorry to ruin your morning Glurd.

Yes, the bearings start-up turning MEGA easy.  I thinned them with a few drips of oil for that reason.  The problem is choppy, stop and go turbulance on only 3 blades.

3 blades was almost worthless at this low location.  The back of my house is only about 12ft away from the mill.  The difference with the 6 blades was almost unbelievable.  I always suspected this, but now I am thoroughly convinced.

But the drag on these blades is still too much.  In approx a messy 30mph big gust, the mill STILL did not make any noise and stayed in control with no furling. At this moment, it did do 2 amps into the 6.5v batts. (13w)

Strange thing is, with only 3 blades (and hooked for 12v) it only does this same power in such a big gust. Weird.

 I was standing right beside it.  The mostly blunt leading and esp. trailing edges need a LOT more rounding over and leveling off. I will do that next.

As is, I suppose the blades are like 'air braking' from the trailing edge drag.

The really giant winds are coming in a few minutes and tonight.  I just tied down my solar panels and 5' windmill with rope.  Tornados are always possible-- I hate that since I live on a slab.

I changed my mind though, I am going to tie down "Mini-mill" too.  I sorta like it- so I don't want to burn it out for no reason in a 70mph+ gail.

I hate this severe of weather.  -Take shelter!

[CmeBREW]

Well I was too late to tie down 'Mini mill' on the testing pole.  The first thuderstorm hit real quick and the rain downpoured while I watched the Mini-mill from my window. I thought it would destroy but it didn't.  Probably a 50-60mph gust only showed 3 amps (21 watts), but the mill was controlled and quite.  It hung around 2 amps most of the first storm.

There is NO furling with this mill. I don't understand why it didn't fly out of control and destroy!.  I went out in this tropical storm wind right behind the mill and it is totally controlled and quiet!  Winds are extremely strong. It makes no sense- it turns Mega easy.  I wonder if the tip of some of the blades aren't reversing angle somehow during max gust.  I love the fact it is silent, but I don't want to sacrifice half the power in common winds either.  There is no way it is stall, because this is the WIMPIEST little alternator possible.

I will just leave it running tonight in the hurricane 1 thunderstorm winds. It might blow my truck away and the roof off, but this mill will still be putting away 4-12 watts in the morning!!  

[ghurd]

There is a chance the tips are going negative with big wind.

Mine make a buzzing sound when it happens.  I think the green thin-wall PVC blades may flutter.

Almost have to take a few digital pics to see how the tips are, or if the pipe is bending back enough.

Some CRAZY winds!  If I had one flying today, I'd bring it in the house.  LOL

Grid is debating if it wants to stay on.

G-

[CmeBREW]

This is quite the big mystery!   I now doubt that thick pvc pipe could be twisting in reverse angle.  I only thought that because I thought the little alternator is very "Wimpy and weak" and couldn't possibly hold back this rotor AT ALL in a hurricane wind with no furling- right??  Now I am not so sure.  

I just remembered after writing the above comments, that I didn't electric tape a few of my coil solder joints inside the alternator, and that there is actually a slight chance there could be a shorting of a few coils on the inside of the sheet metal cover. That would explain A LOT.    

So I went out and tied down the little mill with rope in the mega winds rather than risk burning it out in this tropical storm winds all night.

Or there is a slight chance I hooked a coil up wrong- even though I remember being extremely careful and checking increasing voltage on each coil two years ago.

I will take the altenator apart tomorrow and re-check each coil to make SURE things are right and not shorting a coil causing less power and magnetic drag.

Because something is not Kosher here!  

[CmeBREW]

Today I took it apart- and NO short anywhere and all coils were correct. As I twirled it by hand each coil's voltage went up .4vac    

- I also did this testing both directions. (was same)

So the whole problem is thus my 'not so good' pvc blades.  Must be more drag than I thought. I trimmed down the blunt trailing edge much more today with my router, and put the mill back up, but it seems the same or maybe alittle better.  My blade making skills obviously need more work.

It still is very consistent- and far better than 3-blades in a turbulant location.  

I am still missing the best rpm range quite a bit with this alternator with those slow 6 blades. (even at only 6v batt)

Hopefully, my next one will be better with a low 200rpm cut-in and better blades made from 4" diam pipe.  It was still very strange the way those blades could 'Air brake' so well in a hurricane without making any noise!    

-Thanks.

[ghurd]

If it was anybody else, I'd say cut them down to... about 28"?

But that's what I do (try again).

G-

[CmeBREW]

Thanks Ghurd,,, heck of a hurricane like night, huh?  Our electric went out all night, I had to go sleep at my parents house beside mine (they have a WOOD burner stove!), and even some siding and flashing blew off my their house. This weather is going nuts.

Yes, I am going to try to make a very high solidity clear Lexan set of 3 oval blades about 30" diam with the new alternator I am making now.  I'm also making another 3' diam 6 blade rotor to try on the same alternator to see which works best.

I got a chance to trim down (the wide part of) the 6 pvc blades and round over the leading edge better on the Mini-mill above.

It made a good difference.  It looks to be doing twice the power as before since I can now hook it to 12v batteries (instead of just 6v batts)  and it goes much faster now.  On a windy day/night it is now doing a lot of 10Watts-24 Watts and sometimes can go up to 30watts in a very big gust, and yet I can barely start to hear it make very little noise standing beside it.  With no furling, I like that.  I bet it is going over 1000rpm now which isn't too bad for this quick project of learning. I recall testing it 2 years ago with a fast drill and it did about 30Watts at around 1000rpm.  For such tiny neo-magnets, that is really quite good I think.

Wish I had waited to post about this, because now I would call it a '25Watt Mini-me Mill' which is a little less humiliating.

It will be interesting to see your small mill project too.