VAWT + treadmill motor

[taylorp035]

After about 5 months of operation, I have convinced myself that I will never get any decent amount of power out of it at 12v.  I think to date, I would estimate my power output at about 1 Wh or 3600 joules.....

So it is time to reconsider the design.  My plan is to make a VAWT with a 1 meter height and diameter.  Two blade, savonius, with airfoil shaped blades. 
At first, I plan on makeing this a 1.2 volt machine, not a 12v, so my cut in will be at roughly 45 rpm, which is much more manageable.  Cut in wind speed would be approximately 7 mph for charging instead of 18 mph for my current windmill.

The blades will be made of many 1" wooden slats that are about 1/4" thick.  I will at first charge my 2500mah Nimh cells to see if it works.  If it does, then I am planning on buying some 9 Ah nimh C-cells.
I found some that were about 5.30 Wh / $  , which is an amazing deal in my mind as they were only about 3 Wh/ $   two months ago.  The batteries would only cost me about $22, which isn't that bad.
If I wanted to, I could scaled it up to any multiple of 9 Ah.  With a 9ah pack, I could run my laptop for a whole day or my tv for a few hours and feel that I have actually done something significant.

My only concern is that the treadmill bearings will not like the vertical position, especially with a 10-20 lb blade on top of it.

Peak power would be about 25 watts at 10 m/s, about 5 watts at about 6 m/s.  The motor is good for 16 amps continuous, so I think I will be fine on that front.  I have yet to get any rpm to power graphs, which I hope to do somehow.

Any criticism would be nice.  Construction date would be no earlier than this weekend.  I don't think I set my goals to high

[TomW]

taylor;

Zubbly (RIP) and I were kicking around an idea long ago where we considered using a conversion as both bearings on a VAWT. One on the top and one on the bottom.

Some advantages of doing this:

The bearing and support are the alternator.

Several options for wiring it for different voltages and / or power output.

That won't cure the basic problems of a simple VAWT but I toss out the idea for you to consider to counter your bearing concerns.

Even high end induction motors do not really have any provision for thrust loads so your concern may be very valid with the low end motors.

If your motor has bushings it will be pretty useless under long term  thrust loading.

Good Luck with it!

Tom

[REdiculous]

♋..that gets my vote for a blade profile. It should start on its own like a Sav. but sail like a Dar. too if I'm not mistaken. Attack angle should be somewhat adjustable I'm guessing. I was thinking about using 3 blades, 5' tall w/ a 5' diameter on my treadmill motor. Then I found another use for it..push trailer..but I was tempted.

I know there are bearings out there that would work. Maybe even a bike wheel hub?..I never bothered learning the sizes of the axles, just know 'em as rear/front..but I guess there's a thicker one now (or there always was?). Maybe you could leave the rim on and add a skateboard wheel to the motor..simple gearing.

I might have to try making a vawt just for the heck of it here soon..I like to play with my toys until they don't work anyway, so if it's doomed from the start it's that much cooler. Parts are parts as long as I don't break too many. The only spare wheel I have is a front but maybe that and an old motor might give me something / show me what the worst-case scenario is w/ the wheel idea.

I guess I missed your old one, how big was it?..5 months is a good long while..cool! Have a good one.

[taylorp035]

My current windmill is a normal 50" windmill.  Peak out put was 173 watts, but a 20 mph breeze was good for 3 amps @ 12v.  I was finding that I could only make power about once every 2 weeks or 1 a month because my terrible location.

I was thinking that I could put the motor on top and use a pointed steel rod to support the bottom of the windmill ( I have done this before and it works very good ). 

As for extra bearings, I think I only have regular ball bearings, no thrust bearings.

The one issue is that it would be harder for me to mount a vawt on top of my pvc pipe, especially if the motor was on top.  In theory, I could use a belt to have the motor on the bottom, but I don't think I have any that are suitable.

Maybe I could support the downward end of the motor shaft with my steel pointed shaft....  Then the load would be sent through the shaft, instead of the nonexistent thrust bearings.  This would solve all of my problems

[jlt]

I see that you are having a hard time making any power with you treadmill motor.  The solution is to make  one from scratch .Like a dans 7ft axial . and get it up on a tall tower so it will make some power. Or even a 4ft piggot style. If you can get them spinning they will put out some power even in low winds. wawt turbines make good yard ornaments,but very few put any power: 

[electrondady1]

taylorp035,
i've been following your posts.
 i know your clever.
i think in this case you might be trying to put too many ideas into one project.
that is to say, a savonius to charge these low voltage batteries plus a lift based design with multiple vertical profiles (that could take a bit of design time.)
i have no knowledge of tread mill motors ,but if you can get the charging voltage you want at 45 rpm you should be all right even with a pure drag savonius.

i like three bladed drag mills.
 you get more torque pulses per rev.
for about ten bucks you can buy a used 45 gallon plastic barrel
and cut it up any way you like .

what dia. is the shaft of your motor?
i suggest you obtain a coupling long enough to tie  the motor to a shaft that is the  same length as your vertical vanes.
tie the top of the vanes to that.
on that coupling, weld support brackets (angle iron)that can take the weight of your mill and  channel the thrust into the shaft.
if i recall correctly ,you have been using a 4" dia plastic pipe for your windmill
i'd strap the motor to that vertically and use another slightly shorter right beside it to take the weight of your mill.
tie both support pipes together to stiffen them up.

vertical axis design  is evolving quickly now.
















 

[Norm]

  Maybe I could support the downward end of the motor shaft with my steel pointed shaft....  Then the load would be sent through the shaft, instead of the nonexistent thrust bearings.  This would solve all of my problems

Yes you could...on mine the other end of the shaft has a place to screw a small bolt then a dent
in the end of the bolt and a small steel ball and some oil or grease ought to do the trick.

[taylorp035]

Here are my calculations and a visualization of what I want to do.

(BIG PIC WARNING)
http://i39.tinypic.com/2czeh03.jpg

smaller version here






I am almost think that a 4" board would be too narrow.

[REdiculous]

Here's what I was thinking of doing...

Code: [Select]

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But then I was thinking of a Lenz2 style rotor. I think that would decrease the load on the bearings tho..having them like I imagined. Otherwise all that weight is _up there_ getting pushed on and I think that might translate to some serious forces at the shaft, at least compared to the way I was thinking. Have a good one...I can't wait to see what you come up with.

[taylorp035]

I looked at the lenz2 style, and I was worried about the start up.  I have built a mini cardboard savonius before, and it would start up in winds that didn't even exist.  Unfortunately it fell off a 10 ft step ladder and broke.

I doubt the lenz2 style would reduce the loads, and I also think that it would be harder to build a permanent one.  I once made one out of some toys that pitched the blades depending on where it was during the rotation...

[electrondady1]

ok,!
that's known as a benesh profile.
there has been a lot of scientific study done on them
 they are supposed to be a good design.
there might be an exact ratio required between the width and the depth of that curvature.

glad you posted the drawing i had something totally different from your previous description.

good luck!

[taylorp035]

I tore apart the old windmill today and did a mini test on a 10ah, 1.2v pack to see what kind of amperages I would get.

I found that the motor was good for about .3 amps at ~60 rpm and about 3 amps @ 200 rpm.  This is much lower than what I expected

I also decided that I could get away with a smaller diameter for higher speeds and the tsr will be closer to 1-1.2 since there will not be much load on it.

I did a test to see if my construction method of using 1/4" thick by 1" wide  vertical strips would work, and it seems that it will be easy to build.

Tomorrow I plan on making an official motor output vs. rpm graph on excel.  I found out today that 4 of my nimh cells read 0.04v   

[REdiculous]

I looked at the lenz2 style, and I was worried about the start up.

It has drag and lift from what I understand. The drag side helps w/ startup and the lift helps w/ speed and power.

that's known as a benesh profile.

yeah..I tested that once w/ great results compared to the classic s-vawt. No shaft, a 1" air gap and a 1" overlap at the gap seemed to produce the best results for me...the overlap really seemed to help funnel the wind to the other side. I notice the sketch has negative overlap which is why I mention it.

Another thing I thought was interesting...that profile seems to work pretty well backwards too. Instead of having the curved part in the wind I also tried it with the flatter part out and it seemed to spin about the same.

No offense, but it doesn't seem worth it for a few watts into a 1.2v pack...the motor can put out way more than that. To each their own.

[GoVertical]

Greetings, I saw a video on YouTube where a two blade could stall in some wind condistions, mite consider a three fin design.  Think about adding a 3 to 1 drive pulley for increased RPM's. Direct drive are slow. How to see some pics of finished project. Best of luck and cheers.

[REdiculous]

A double 3:1 would probably be even better if you can manage it. Maybe there's a better ratio for yours but..

That's how I've got my treadmill motor geared to my bike and it spins the rear wheel up to 750rpm. 300rpm at the rotor/wheel = 2700rpm at the motor.

This is where I think big blades (3x 5') would help and the Lenz2 style seems the best option for a higher power level. Weight vs bearings was my concern but since someone posted that trick (support the other end of the shaft..duh), weight might not be a huge issue.

I just know there's no way I'd bother w/ less than 20w...it's a waste of a good motor, imo. For a couple hundred bucks you could probably have that motor on a bike and be cruising down the street instead of charging 1.2v batteries....just sayin'... 

[taylorp035]

No offense, but it doesn't seem worth it for a few watts into a 1.2v pack...the motor can put out way more than that. To each their own. Smiley

I know, a 12v system would put out way more power, but hitting 12v was difficult and super rare.  1.2v would be possible 50% of the time, so I could make more power.  Plus, I don't need the power, I am just playing around.

Another thing I thought was interesting...that profile seems to work pretty well backwards too. Instead of having the curved part in the wind I also tried it with the flatter part out and it seemed to spin about the same.

Very interesting.

Greetings, I saw a video on YouTube where a two blade could stall in some wind conditions, mite consider a three fin design.

I have been seriously considering this myself.  I already have the holes for a 3 blade, and the start up was a concern of mine.

[taylorp035]

I just know there's no way I'd bother w/ less than 20w...it's a waste of a good motor, imo

I fully understand.  Anyone other than me would decide to build a 12v system, but my goals + batteries + lack of charge controller are pointing me towards a low powered, high Ah system that runs more consistently.

I could make a really large vawt, but I think I will start out small for now.  Maybe in 2-3 months I will do a geared system ( I need a pulley of some sort... ) and then I will hit 12v.

[REdiculous]

It just hurts a little to see a good motor do a lot of not-much, I guess. I'm glad I didn't pursue the vawt idea I had originally...my  treadmill "motorcycle" is way cooler, imo.

When it comes time to go big and gear it..pulleys usually suck...my double reduction w/ chains loses 40w but it never slips (and is very tight to handle 1kw). It was a pain to get the chains lined up tho..so maybe a toothed belt would be better. Have a good one!

[taylorp035]

It was a pain to get the chains lined up tho..so maybe a toothed belt would be better. Have a good one!

I have used toothed timing belt before on my robots and they work really well.  Of course they are expensive, unless I could find a used one.
I have also made wooden gears, once a set of 2:1 and once a set of 8:1.  Unfortunately, I don't have access to the CNC router anymore.

This morning I did some real output tests.  I then put the crude numbers into excel and found the exponential equation of the best fit line.
The numbers I got confirmed that charging at 1.2v is VERY inefficient, but a cut in speed of 6 mph is still very enticing. 
My test numbers that I got may be off by a good bit b/c I was doing estimated rpm from a second hand on a clock.  I did 60,120,180, and 240 rpm.  Amps were 0,.6,1.8, and 2.8 respectively.



Here are my new calculations.  The changes are:
3 blades
1.2 tsr instead of 0.8 (the power output is small compared to the energy in the wind)
.4 meter radius instead of .5 m

large version here:
http://i39.tinypic.com/8ydiqa.jpg

[REdiculous]

I have used toothed timing belt before on my robots and they work really well.  Of course they are expensive, unless I could find a used one.
I have also made wooden gears, once a set of 2:1 and once a set of 8:1.  Unfortunately, I don't have access to the CNC router anymore.

Cool..sounds like you've got that stuff nailed then. I've been tempted to make wooden gears before but I've always wanted to do it by hand and I've just never taken the time...it seems I get frustrated and find a better solution. I think CNC is cheating..I wish I could cheat.

Gonna get pics of the progress at some point? later

[taylorp035]

Gonna get pics of the progress at some point?

   Progress, I am not sure what that means.....   

Yeah, I will make sure to take pictures.  The power just went out for about 1/2 hr, so maybe it's time to start building.

I am wondering if I could make the diameter even smaller for higher rpms.  If I do .25 m radius, it would increase the rpm by a factor of 1.6 from a radius of .4m, and a factor of 2 from .5 radius.
I am going to go and twist the motor by hand and reconsider making the radius smaller.

[Bruce S]

Gonna get pics of the progress at some point?

   Progress, I am not sure what that means.....   

Yeah, I will make sure to take pictures.  The power just went out for about 1/2 hr, so maybe it's time to start building.

I am wondering if I could make the diameter even smaller for higher rpms.  If I do .25 m radius, it would increase the rpm by a factor of 1.6 from a radius of .4m, and a factor of 2 from .5 radius.
I am going to go and twist the motor by hand and reconsider making the radius smaller.

Been following this thread with great interest, especially when you decided to switch from 12V to 1.2V to charge NiCd/Nimh.
From years of reading other who have built VAWTs and a few of the very small ones, (Windstuff Ed's unit, etc) I can say that by decreasing the radius you will increase the RPMs. However in order the stay within the volumetric area you will I'm sure you already know, need to increase the height.
There will be a point where the height becomes a strength burden on the system and there will be a point where the diameter will be too small to catch enough wind to stay self-starting.

One thing I may have over looked was the charging circuit, have you decided on one yet? or did I really miss that part of the thread?

Cheers;
Bruce S

[taylorp035]

One thing I may have over looked was the charging circuit, have you decided on one yet

I was just going to stay with my 25 amp bridge rectifier @ 1.2v, then swap the 10 cells into a 12v pack for my 400 watt inverter.  The inverter shuts beeps at 11v, so if I go with the 9ah nimh cells, then I should be fine for running my laptop/ 32" tv / stuff.


BIG progress has been made    I Cut all of the wood for the blades and the 6 top and bottom pieces that hold the curves.  It took about 5 bdft of 1" poplar and about an hour on the table saw.
The blades will be made of 1" x 1/4" x 20" strips, roughly 40 of them.  It took about 2 hrs to chisel the slots for the curves by hand with some old school hand carving tools.

I will take photos tomorrow, most likely in the morning I hope.

The windmill is now officially 20" tall and 12" radius, down from a 20" radius.  I decided that the motor was easy enough to turn for a smaller diameter.  Plus, I can always add another set of blades on top of this one.

[Bruce S]

May I make a small suggestion?

I will qualify this with saying that I've worked with NiCds for a great many "projects".

I have found that when using inverters with these and other things that can have a surge load, you might look into have a full 12 (dozen) batteries for a full14.4Vdc.
The inverters could go into shut down or LVD if the power request or surge is large enough to pull them to momentarily drop down below the threshold.
The 14.4Vdc, the inverter will see normally has not been a problem for any of the MSW inverters I've been using. They range from 150w to 800watter for the coffee and microwave .
I'm looking forward to the pics, this is of great interest to me since I cannot put up a HAWT in the city.

Have FUN!
Bruce S

[taylorp035]

In the past, I have used between 10 and 12 AA nimh cells to run my inverter for about an hour with a 20-30 watt load.  I sometimes found the 12 cells would have too high a voltage, so the inverter wouldn't start.
Here is a youtube video of my set up:
http://www.youtube.com/watch?v=Isswvcz7Mcg

I will get the pictures in about 15 minutes.

[taylorp035]

Big picture
http://i39.tinypic.com/rwuv6x.jpg




Big picture
http://i40.tinypic.com/jutt1w.jpg












Some vintage tools

[taylorp035]

More pictures after I assembled the blades with the help of my brother.

[ghurd]

I have no idea how it will work, but it sure looks nice!
G-

[REdiculous]

That does look good, doesn't it! Nice.

[Rover]

Ever througth of making barrels for casking wine... looks like you are 1/2 way there....

[taylorp035]

I plan on making them fit together perfectly.  Then I will use a hand plane and make a perfect curve.  I am still debating whether I should glue the slats together, because that would be very messy.

[XeonPony]

I would go with gluing them, then discarding the lower support blocks and replace them with some 1/8 steel bands, that way you could weld the bands to a much lighter hub and greatly reduce air friction on the machine in total.

Looks good so far.

[electrondady1]

it looks really good taylor035.
may i make a small suggestion.
before you fuss with the fine details and finish of this prototype , see if the wind likes it.

you have combined the benesh profile in a three bladed configuration
and how the wind reacts with it is in question.

if the wind makes it spin, sweet !
lay on the linseed oil !
if it works poorly you still have the makings of one traditional benesh windmill
and 50% of the next one
good luck