My small axial flux turbine

[klsmurf]

Hi All,

Waiting on parts, so I've got time to download photos and do some documenting. Don't know how much interest there will be, but here it goes.
A little background to start. I have been a member here for a couple of years and always wanted to build an axial flux turbine. Like bow-ties, wind turbines are cool! I can't justify building a 10' at this time, mainly because of tower costs.

Like many on this board, I'm a tinkerer and a recycler. I had an opportunity last fall to acquire a box of hard drives in a labor barter deal, perfect! Wire from a couple motors along with various hardware bits I had, I've got the start of a small turbine.I've read the books, practically read the whole board, but you have to have lab time. That's why we tinker!

State of the art testing facility:


My magnet rotors were 2 saw blades on each side though well aware of the problems.The blades happen to have a sixteen pole layout with good spacing.


The wire I had available in quantity was #24 and #21 AWG. I wound a test coil of each.


 Since I haven't played with magnets and coils since high school physics, I started with a few basic observations. I stacked various heights of magnets on each rotor and watched the voltage change. I also did the paper clip test on all variations. It stuck on all of them of coarse, but you could tell the strength by feel.

Up to this point, I had know idea what kind of power was possible. I took the voltage reading from the #21 wire and calculated that I could make a 3 phase, 12 coil stator that would work for a 4-5' prop. I compared my test coil to my CAD mock up and saw plenty of room to wind 2 in hand. I wound one of those coils and tested.


During this time of test, I knew there was all kinds of flux leakage. In fact, the third layer of magnets on each rotor didn't contribute much, it all seemed to leak out the back. I made a trip to the local recyclers a found some .25" plate and had some 7.5" discs cut.


More to follow.....                                         Kevin

[gww]

I always love to see projects in pictures. Can't wait for more.
gww

[klsmurf]

Hi All,
From the last picture I posted, you can see some hardware attached. The discs I got were just that, blank discs. Getting them to what I needed is a whole other story. I don't own a mill so I'll just say grinder, files, an antiquated drill press and a whole lot of measuring and marking.

Checking alignment:


After some cleaning, painting, and marking I got the magnets relocated to their new homes.


I could now return to coil testing. From the new data I determined that I would need 74 turns for 14 volts wired in star. That was down from 86 needed with the saw blade rotors. Quite the difference giving me lots of room. ( I'm considering winding another stator down the road with single strand #16 AWG, it would be close) For now, I'll finish out this one with what I got and hope I got enough wire.
I didn't:
http://www.fieldlines.com/index.php/topic,147767.0.html


Having sorted that, it was time for some molds and templates. My magnet and coil thickness didn't work for any common dimensional building material, so having a good choice of scrap and doing some sanding, I got things made up.



Wiring the stator was pretty straight forward. I did however take the liberty of planing for, and will, bring the star point out. I twisted, crimped, soldered and shrink wrapped the connections. They shouldn't be any problem. I know because after double checking  I found a flipped coil. Damn!



The wire I used was reclaimed so I wanted to make sure all the coils were good to go. I rigged up a test for resistance and all coils were fine. I did the phases also once everything was soldered together.



This is where I'm at present. The vinlyester should be here this coming week so I may do some pouring next weekend. Thanks for looking. I'll keep you posted.
Kevin

[gww]

This is fun and you are providing lots of info.  Can't wait to see it done and hopfully working well.
gww

[dave ames]

Thanks for the closer look Kevin. It's coming together very nicely.

Your pics point out another possible advantage to a higher magnetic pole count in a smaller build that I may have been missing...that is the real estate gains made in the center of the stator by the larger number of smaller diameter coils..that space is at a real premium in a small diameter axial machine. Well done!

Looking forward to the next installment

It's all good fun!
Cheers, dave

[klsmurf]

Hey Dave

Thanks for the comments. Space is definitely at a premium with a small axial. I played around with a few magnet configurations and counts. Double stacks, 3 pieces to form a wedge, but this visually appealed to me. Any advantage to this configuration is purely accidental.

Kevin

[klsmurf]

Hi all

I will make this an abbreviated update as I lost one earlier during a preview.
Got both mag rotors and the stator poured over the weekend. Poured the stator first and had issues.  I evidently didn't have my mold secured on one side and lost resin.  I ended up with a pocket/void and some bubbles.


Some surgery and a strategic re-pour and it is good to go.


The magnet rotors came out better. There are a few surface voids but all the magnets are covered.


Everything lined up well and testing the phase voltage showed no problems.



I'll do some more readings in the next couple of evenings and post some specs and numbers for anyone interested. 

Kevin   

[gww]

Can't wait.
gww

[Southbuck]

Ive been a member for years, totally lost interest in this site when a know it all ruined the fun of building small mills.

This brings me back, something small but interesting.

Keep posting your work.

Doug

[klsmurf]

Hi all

I haven't had much of a chance to do any work on the alternator this week.  Results of some basic electrical test below.  I also went back through my notes and organized them .  Excuse the mix of imperial and metric.

GEOMETRY:
16 pole/12 coil         3Phase Star

MAGNETS/POLES:
HHD magnet halves stacked 3 high                          Front rotor------9.6mm  magnet height
                                                                                 Back rotor------9.8mm
*effective magnet surface area      1/2" x 3/4" (12.7 x 19.05mm)

COILS:
#21 AWG   2-in-hand    74 turns each                            outside---- ~1 1/2" x 1 3/8"  (38.1 x 34.93mm)
 46 grams      ave. 0.176 ohms                                     * inside----- 1/2" x 3/4" (12.7 x 19.05mm)

ROTORS:
7.5" x 1/4" (190.5 x 6.35mm)            Front----66.7oz. (1887g)   magnets and vinyl included
Air Gap   15.4mm                               Back-----73 oz. (2070g)      magnets, vinyl and bushing

STATOR:
9" o.d. x 4.5" i.d. (228.6 x 114.3)   9.5" o.d. at terminals         35oz. (992g)   
ave. thickness-----~7/16" (11.2mm)
Phase resistance             A.    0.705 ohms    B.    0.703 ohms    C.    0.698 ohms

TESTING:
RPM                     O.C. VOLTS                                       RPM         LOADED AMPS (13.8 V regulated bank)
236                         12.0                                     281           cut-in                                       
279                         14.0                                     300           0.24
297                         15.0                                     350           1.71
350                         17.84                            *Didn't want to push my little power supply,
496                         25.56                            driving the ametek, driving the alternator.
700                         36.18
414                         12.0        Wired Delta

[Larsmartinxt]

Good job!
Makes me want to build one

It would be neat to see the load on the powersupply in your notes as well. Then you can calculate the efficiency of your generator at cut-in.

[klsmurf]

I had thought about it previously, but when doing the testing, completely forgot about writing it down. I remember it really jumped up the amps from 300 to 350 rpm. It's only a 30 volt/ 5 amp supply.

Kevin

[klsmurf]

Hi all

Lars' post got me thinking last night.  I didn't write down any of the PS numbers, but I did video some of it. I went through the video and was able to find 2 data points.

In order to find the efficiency of the alternator, I will need to know the ametek efficiency, right?

Thanks Kevin

[Larsmartinxt]

Yeah. but you can do a rough estimation by subtracting the power draw unloaded/before cut-in.

Lars

[dave ames]

Great stuff here Kevin 

Always amazed with what can be done using mostly hand tools and a big pile of reclaimed goodies

Time for some blades!

Cheers, dave

PS- curious if you have a special meter for low ohm measurements or perhaps you measured the wire length beforehand? I can never trust anything below 2 ohm or so with my cheap DMM.  fun stuff!

[klsmurf]

Hi all

Time for an update.  It's getting closer to flying and I'm anxious, but work keeps getting in the way!

Hey there Dave,

PS- curious if you have a special meter for low ohm measurements or perhaps you measured the wire length beforehand? I can never trust anything below 2 ohm or so with my cheap DMM.  fun stuff!

No special meter, I just use the voltage drop method and do the math.  There's a picture up the thread of a set of coils in series with a 12V light.
 

Always amazed with what can be done using mostly hand tools and a big pile of reclaimed goodies

If you like re-used parts, take a look at my "YT-WAMATH" in the following picture.  I couldn't salvage the trolling motor, but parts is parts.
"Yaw Tube- With Adjustable Mount And Tail Hinge"


I've used this for over a year playing around with my DC motor mills.  Works like a treat.  Has survived a 60+ mph storm and 35 mph consistent winds.

Looks like it should work, just needs some blades and I have a little electrical work getting rectifiers and a kill switch hooked up.



Tail offset from shaft line



I haven't even begun to look at blades for this yet.  It's come together a lot faster than I anticipated.  We're in the summer lull for wind.  Maybe I'll try to pull a fast one on Mr. Murphy and not put it up.   Nah!

Kevin

[klsmurf]

Hi all

Finally had a couple of afternoons here where the wind has gotten above 8 mph.  After my last post, I searched around my shop and found my first wooden set of blades.  I carved these not long after I joined the forum.  These were for no specific mill, just to learn lay out and such. Don't remember any of the specifics, but they were made from a 2x4, 5.5 feet long (diameter) with a twist and a small amount of taper.

Hooking up the electrics


I tilted the tower up and the mill yawed into the wind. Went inside and flipped the switch and it started spinning right away.  The wind was around  5mph so it all looked fine.  A few hours later it went to 8mph, then 10 and no cut in, not good.  As I figured, the blades are just too long.

I took 3 inches off each blade (5 ft. dia. now), added a little more taper and fine tuned the airfoil.  Tried them again, but still nothing at 10mph.  Couldn't realistically cut any more off these, so plan B.

I had also on hand a 2 blader made from a 2x6.  It was 5 feet long so I gave it a try.



WooHoo!  It makes power.  Cut in was a bit higher than the bench test.  290 rpm as compared to 280.  It ran well the rest of the afternoon.  Winds were 10-12 mph with gusts to 15.  It hit 100 watts at some point.
That was yesterday, today the wind started earlier than normal and built to 10 mph by noon.  When I came back from errands at 3pm the wind was gusting and since I haven't set my furling properly yet, I shut it down.
Here are the numbers I have recorded over a 24hr. period.
Ave. high wind speed                    13.7 mph
High gust speed                            17.7 mph
Amps max                                      10.64
Watts max                                     151.8
Ah       8.04                Wh               110.9
The fun continues.

[gww]

I am still enjoying your build prossess.  I like how you lay it all out and explain things.  I will be putting up some of my turbines soon but have not figured out my internet connection yet, so I may miss a chance to talk in pictures.  I thank you for doing so.
gww

[klsmurf]

Hey there gww

Thanks for tagging along!  I appreciate the kind words.  My hope is that this thread helps some folks that are just starting out.  The amount of information I have gleaned from this forum is tremendous, just trying to add some.

Kevin

[gww]

I took a bunch of microwaves apart and used a chrysler front bering.  I eventually replaced the microwave magnets with neo's which caused numorous new issues.  I got advice here the whole way.  Its ok? 

I did build two hugh piggot 8 footers.  Having plans was much better. 

Through out your post I didn't see you asking many questions.  It was more show and tell.  Something for me to copy.  Thanks for taking the time.
gww

[dave ames]

I agree with gww...your project checks off all the boxes and gives another nice resource for folks looking to do something along the same lines.

Well done!

It's all good fun.
Cheers, dave


...and a somewhat off topic PM sent.

[klsmurf]

Thanks again guys. 

Dave,  PM returned.

gww, 

Feel free to use this however you want. That's why I put it here.  I have questions sometimes, but was taught early on to try to find the answers out yourself.  I think you learn more from mistakes than someone telling you what to do. 
It's not that I don't trust anyone; it's just that I don't trust anyone! 

Kevin

[gww]

If you learn more from mistakes, I am going to be really really smart some day.
Cheers
gww

[klsmurf]

   Good one.

[windy]

klsmurf,

Nice looking build!
 I have just one observation that I would like to comment on.
 In looking at your "YT-WAMATH", I would be concerned about the two bolts holding the generator to the mast. With any kind of vibrations those bolts could wear into the tube and work themselves loose.
 I would put a steel plate between the bolts and the tube so you would increase the holding surface area.  I would also drill dimples into the plate so the bolts tighten against them. Also, add two nuts on the bolts to be used as jam nuts.
 Another thing I would do is, put a safety bolt through the end of the tube to keep the assembly from falling off if something does come loose.
 As others will agree. when dealing with wind, if you allow something that can go wrong, it probably will.

windy

[klsmurf]

Hi Windy
Great suggestions and thanks!

 I will be taking the mill down this weekend to check all the workings, so I will integrate them.  This is the first time I've used 2 blades and the vibrations are definitely more than 3 blades. 

Kevin

[klsmurf]

Hi All
It has been a couple of months, so it's time for an update.  I flew the 2 blade set-up for a few days then took it down.  I knew the rear bearing was on the way out so I replaced both.  I made a cover for the shaft and bearing assembly.  If you are a regular reader of the forum, you know I've been working on blades.

I've had some quarter-sawn cedar set aside, so I decided to make the blades angle using wedges.  This allows me to make a no twist or taper blade using the wood to its strength.  It also lets me do all the rough sawing with my table saw.  The drawback is that the wedges have to be very accurate in all dimensions; otherwise tracking will be difficult to adjust.  I made a set with a Clark-y profile and am working on a set with the GOE 222.  I had the blades on the alternator to balance them and the weather was going to cooperate, so I decided to test them primed only.



I moved my tail adjustment to the shallowest angle and increased the alternator yaw offset another ½”.  Better safe than sorry. I'm glad I did, as the next couple of days we saw good wind for around here.

A snippet of the first few hours of wind


The chart below was compiled during the time span above.  Tallied from 3 separate meters, with very few data points spread far apart, compiled by a human.  Take them with a grain of salt. 


After watching the mill for a couple days, I will be making adjustments.  I believe it's furling too early so I'm going to increase the tail angle first.  I hope it also holds the mill truer to the actual wind at lower speeds.


Thanks for looking.  Comments welcome.  Still having fun.
 

[klsmurf]

Hi all

Time for an update as sad as it may be.  Those of us in the US, that live in the "tornado alley" know full well the power of the wind.  I'm on the Illinois/Indiana border and my condolences go out to those who suffered loses this last weekend!


I was hoping to report on how well the blades have been working.  How I got the tracking in lower wind figured out.  Production numbers.  All these are moot at this point because:



I will be making another stator at some point in the future.  Failures are but learning experiences.

Kevin

[Bruce S]

First time EVER I was out and was asked to take cover , though have been in more than one "Nature proving who's boss" events on this globe & St Louis didn't even take a hit. Though power loss at home was evident and one of my 6 panels "My test unit" was found 20 feet from where I'd left it for the day ( Murphy lives two houses down). Nothing broken, just a real world reminder to anchor stuff.

Mill: Ouch!!  Looks like a over-heat event of some magnitude  .
What if any number do you have before THAT happened?
Hopefully you will be able to salvage for a new one soon.
Best of Luck
Bruce S 

[kitestrings]

Sorry to hear/see this.  Got to be disappointing, and we put so much effort, energy, care into them.

How did the rest of it hold up?  You had a pretty substantial tower, so I assume that stood it all...but the blades, tail did eveything else survive structurally.

I had a blade hit a tower once, from a position seemly to far to ever happen.  It wasn't pretty.

Hope you rebound with something better.  Glad you shared.  ~ks

[SparWeb]

Yeah, it's an opportunity to do it better next time right?


right?


Who am I kidding.  It's a bummer.


But I still hope you can get it back up in the air. 
And vote #2 for some results, even those before the burn-out.  Ya nevver know!

[klsmurf]

Hi All,

It is sad and disappointing even though it is a hobby mill and I don't need the power.  It was my first.  Now I have another first. 

This wind event struck me as odd; more like a hurricane in that it started days before and remained the day after it left.  I was in my shop when the burn-out first happened.  The building shook twice within 5 seconds.  It was like the concussion wave of a blast!  I looked at my meter and it read average speed 31mph and latest gust of 45mph.  It had been between 24-30mph average all morning with gusts to 40.  The mill was putting out between 150-180 watts furled with peeks to 220.

I looked at the mill and it was spinning, but the anemometer cups weren't.  I came back in and checked my turnigy meter and it read peak watts of 284 and it was only registering a little over 100 watts.  I new then it had burnt out a phase. (pretty evident which one in the picture above)

I later checked the local rural airport's records and they showed gusts to 58 about the same time and the funny thing is their anemometer readings went off line soon after.  Mine didn't start working till later in the evening after this.

The 2 days preceding this, the mill made 2.6KwH and 3.2KwH.  The tower is fine and for the most part the mill also.  My tail boom is 2 piece pipe in pipe for length adjustment. The outer piece is EMT and is slightly bent.

Things I will be considering/changing in the future.
1. Full 90 degree furling  (only 80 now)
2. Using new wire ( I did visually and electrically check it but...)
3. Less aggressive furling setting ( It's hard for me to be conservative on anything  )

[tecker]

I wouldn't make too many changes but a larger inner hole . Just bring down the star connection and add pickup coil in the phases of some awg 32 . To flip to delta