Wrong Motor

[adaml]

I have attached a dc 130v 2 1/2hp permanent magnet generator to my blades.  They seem to spin at a good rate but I am not managing to get more than 3v produced.  Being new to all of this please could someone tell me if I have made a fundamental error and am trying to use the wrong type of motor?

Many thank,

Adam.

[Norm]

Need Much More Data ......

How big are your blades? What rpm does the motor

spin to make 130 volts?

We have no way of knowing 5000 rpm?

Seem to spin at a good rate?

M'Gosh ...I have some pinwheels out in my yard

that are spinning at a good rate..

(not being sarcastic just giving you an example)

If you have a motor that will give you about 3 or

4 volts cranking it by hand at 60 rpm then you

might have the right motor.......

( :>) Norm

[Norm]

  3 or 4 open volts, that is

[adaml]

Thanks Norm,

Apologies new to all this but should have provided better info.

Blades are 36", 3 of made of 6" pvc piping I had lying about, mounted on an 8" aluminium hub.  

I reckon that in today's wind (which is the strongest I have tested in yet) I am getting about 200 - 300 rpm max.  I do not reckon this is enough even though the blades are spinning to fast to visually keep up with sometimes.

When I initially got the motor I did rig it up, a spin with my fingers was enough to make a 12v car light bulb glow.  Spinning it up on my drill at maximum rev's turned out about 80v.

I am trying to build this as a prototype for a friend who wants to set it up on a remote piece of land.

The tower is approx 12"

My apologies again for the original scant infromation.

Many thanks for you help.

Adam.

[adaml]

That is 3volts with no load, just connected to multimeter.

[Norm]

You're new....so first of all got nothing to do

for awhile.....so.....

First off your picture is a link or something

have you followed Wooferhounds instructions on

how to post pictures....It was just posted recently

so you should have no trouble finding it.

I got your picture , but it was a roundabout

way of getting it...not convenient don't worry...

we all had trouble posting pictures when we

started.

I don't think there is anything wrong with the

motor....just your connections maybe...are you

connected to a battery when you measure this

voltage?

Had one person get varying voltage....turned out

the hub was slipping on the shaft.....not good !

 LOL

 

[CmeBREW]

What is the rpm of the motor?  If it is 6700rpm , then it is no good as a mill generator.  It would take over 600rpm to reach the 12 volt cut-in with a 4' diameter prop.  What is the diameter of your prop and type of blades?

[TomW]

adam;

Well, it looks nice but in that location it will be unlikely to get much clear wind. You cannot really judge that turbine's performance in that setting.

Surrounded by tall "stuff". Even if it is open land behind the photographer the turbulence would rob all the power the wind might have.

Be much easier for you to get useful test data by spinning it with a rope around the axle, a drill or something in bench type tests.

What feels like a nice strong breeze will not be the same as an open field breeze due to turbulence from air hitting all that stuff around the turbine.

The turbine looks nice. I suggest you haul it out in the country someplace open and set it up you might be surprised at how quick it might spin up in open air wind.

Don't get discouraged, I had the same problem with a couple turbine experiments in close to the buildings here and I am in a very rural area.

Tom

[tanner0441]

Hi

I could not understand why I seemed to have a good wind where I am.  Then I bought an anemometer from EBay, my good wind, which was blowing plants over, turned out to be about 3 to 5 mph and swirling.

just a thought

Brian

[adaml]

I very obviously have a great deal to learn, lol, thank you all for your input.  The motor is rated at 95-130 VDC, 0-6750 rpm which I got the net, hence wondering if it is not the best one for the job.  The wind here is not clean but I intend to set it up to test properly in a large open field next door away from all buildings, trees etc.  However, I had hoped to see more than max 3v when only connected to my multimeter.

[adaml]

Thank you Tom, was beginning to get a bit discouraged must admit, will persevere though!  I did test the motor by connecting to my drill and it produced plenty of voltage, up to about 80 but this was obviously spinning very fast!!  The motor itself is dc with four leads from it.  As far as I can determine there is only one positive and one negative output, I can not fathom what the other two leads are for.

Again thank you.

[TomW]

adam;

I can not fathom what the other two leads are for

It could be some form of feedback. maybe a hall sensor or ?? Slap an ohmmeter on it see if it gets a reaction when spun?

Lots of motors use feedback schemes for positioning, limits, etc.

Good luck with it.

Tom

[kurt]

you would have to spin that motor approximately 625 rpm or so to get 12v out of it that is way to fast for a windmill always look for a low rpm motor when looking at motors the crazy fast ones don't put out anything at a speed you can spin them with a prop. to get a general idea how fast you are going to have to spin a motor to get the cut in voltage you want divide the max rpm on the nameplate by the max voltage on the nameplate then multiply that number by your cut in voltage. usually 12 for small systems.  that will give you a ballpark idea if the motor will work or not.  4' props like to cut in about 300-350 rpm the larger the prop the slower the cut in needs to be

[adaml]

Thanks Kurt,

Hmmmm, should have done a bit more in-depth research before rushing to purchase a motor, just trusted the description given on the web site!  My blades are 36" length each, three of and I do not think that they will ever realistically spin to 625rpm.  This size seemed larger than others had made having done a trawl of others websites.

Is there a golden rule or some basic figures to look for when chosing a motor?  Think I might have to go back to the drawing board regarding the motor and call that lesson learnt.  I have heard of Ametek motors but again they seem to come in all shapes and sizes so am a bit ignorant of which sort is best suited.

[jlt]

 

I took a look at your picture.                                                       And i think most of your problem is in the blades.

[Norm]

An Ametek motor is perhaps your best bet for

beginning...Here is a very good link....

http://www.tlgwindpower.com/ametek.htm

and get a load of that TLG 500 watt generator !

Nice huh?

BTW...looks like you're handy enough to make

your own Alternator ...have you ever considered

making your own from an old 20" window box fan?

makes about 50 watts uses much smaller blades

half the size of your blades....most difficult

is grinding 4 flats on the armature and gluing

4 neo magnets onto it.

Ghurd posted in his diary awhile back....

[Norm]

Here's Ghurd's motor conversion.....

http://www.fieldlines.com/story/2005/7/4/34446/17324

Looks simple enough?

[adaml]

Thanks again all for all your feedback.  Jlt please could I ask what you reckon the problem is with the blades?

[ghurd]

Far too steep at the root to go very fast.

http://www.fieldlines.com/story/2003/11/11/172721/53

G-

[adaml]

Thanks ghurd, please could you put that in layman's (or idiots) terms!!!!!  I am guessing that means I need to cut some off the blades near the hub??  I should have posted in the newbie section, I now realise!!

[adaml]

Or the angle of the blade when attached to the hub is wrong??

[ghurd]

About half as wide near the hub.

Quick guess: measuring around the curve near the hub should be about 2.5" or 2- 5/8".

The far blade in the pic looks strange at the hub.

The near and highest blade looks like the tip may be twisted backwards, and that will get worse as pressure from the wind increases, slowing the blades down.  The tip should be angled the same direction as the root (hub area).

The diameter will have to be smaller too.  Maybe 42" is what I would try, for no other reason than a gut feeling.

The hub looks OK, but I'm not too picky about that.

Don't expect much until the leaves fall, and the location still won't be very good.

I don't think all hope is lost.  I am sort of surprized it made 3V like it is.

G-

[adaml]

Thanks ghurd, so I need to shave some of the blade width off near the hub and reduce blade length/overall diameter?  All I did to make these blades, as a first attempt, was to 1/4 6" pipe, use masking tape as a stencil and cut along that, hadn't done much other tampering with the design!!  I didn't know what to expect when first hooked up to multimeter but when whipping round got just over 3v unloaded.  I suppose I am looking for maximum speed for the area, as you say not the ideal location.

Supposed to be working but fascinating info on here, thanks to all, and for all the continued help.

[ghurd]

Yes, shorter, narrower blades.

And it wasn't whipping around.  It was crawling by our collective standards.

Wait until you see it with better blades!

Scared the poo out of me the first few times.

CmeBREW has a pic that will give you an idea of how it should end up.

His are tweaked for his purpose, but notice the root area where it meets the hub.

His have a curve after that, which isn't needed.

Also notice the tip of the far blade, and its angle.

Best pic I could recall.

http://www.otherpower.com/images/scimages/3274/leesonpvcblades2.jpg

G-

[adaml]

Thanks very much ghurd and LOL, obviously still snails pace then, enough to split my nose open when I walked into it trying to get the cat in!!  

I have another rough cut set of blades 24" in length each.  I will try to narrow these off and attach them and see what happens, would you reckon that is an acceptable length or do you suggest shortening to 21"?  Thanks for the continued help.

[Flux]

I didn't intend to get dragged into this one, but I did wonder if your prop was 3ft or 6ft diameter, I wish we could find some way round this ambiguity.

Your motor is very fast and you would need very fast blades to stand any sort of chance with a 6ft prop. I agree with the others that your prop looks very strange indeed with far too much pitch.

If you really want to try a high speed prop then it may just be worth looking at the freelite prop. It was 2 blade and at 6ft that is not a serious disadvantage but normally I would suggest you keep to 3 blades.

The Freelite cut in at about 450 rpm and reached full power about 1100 rpm so you would loose out on the low winds but you would certainly get well above cut in in higher winds.

At least the details would give you some idea of the sort of angles you should aim for for a fast prop. This one has no twist but it would probably start with your motor. If you reduced diameter to 4ft 6" or 5ft then you may need to think about having a coarse angle near the root, but the same small angle would be fine near the tip.

I think you should be able to follow the drawing.

Flux

[adaml]

Thanks very much Flux, diameter is 6 foot.  Personally, and the more I read and the more I learn from you people, I think my motor is too fast and am looking at another with far lower rated rpm at 30vdc.  I would, however, still like to up the speed of my attempt.  Thanks for the diag. makes more sense now.

With regard to length and pitch, I was obviously labouring mistakenly under the impression that the larger the blade and more pitch on each blade the better they would catch and "scoop" the air thus forcing them round.  Looking at the pics on this forum it seems the correct approach is to "slice" through the air?  Thank you again.

[CmeBREW]

This is in response to the PVC blades link that Ghurd showed.  I hope scoop puts it in the right place-- sometimes it goes to the very bottom of the thread.

That link to the pvc blades were my first version. I trimmed them down thinner to make them go faster here:

However, the diameter of these blades is 6ft. 10 inches.

The 12v cut-in for the big DC motor I used for this prop was only 130rpm--- which is Much, MUCH slower than his 620rpm (12v) cut-in dc motor.

Even though these blades are quite fast (not as fast as wood though) , they would be nowhere near fast enough for that motor the poster has.

I think he needs to get a better dc motor with a lower 12v cut-in.

Also , I think the cogging is significant with his motor and very difficult to start up with a 4' diameter prop even with 5 thin pvc blades.  

[ghurd]

I do know what you mean, but the perspective in the photo you posted makes them look like spaggetti!

I tried to show him the end view.  His end view of the root looks like nearly 90 degrees.  Your photo shows the end view of a decent PVC blade very well.

The motor could be better.

I am trying to get something from what is available, before he gives up.

G-

[CmeBREW]

Ghurd-

Yeah, it is difficult to see the perspectives clearly with photos.  You are right, the one you showed shows the angles better for a perpective. I just thought I would say that by making them even thinner (less wide) it did clearly get more speed which is what he needs a lot of.

I could not see his photo of his mill anywhere.  How are all of you seeing his photo??

I even went to his 'files' to try to find it, but no photo!

No one ever said if his blades are pvc or wood?? I suppose pvc.

I also hope he don't get discouraged. I remember the frustration of only reaching 10 volts (so close, yet SOO far away!) in a fairly big wind with motors similar to that one.  

Maybe Flux's high speed blade design can get over that cogging well enough and  make the extra speed needed.  Worth a try.

[adaml]

Hi Ghurd, many, many thanks again, and to you all, would be easy to get dispondent at this stage!  I have tried to post two new pics, following norms instructions.  One of the blades mounted on a test hub and another of a smaller blade I was tinkering with last night.  Your continued input would be very much appreciated.  Also have been looking at a Ametek 30vdc on Ebay but getting expensive!!

[wooferhound]

Here are his pictures . . .

http://www.otherpower.com/images/scimages/11306/

[ghurd]

The new blade looks a lot better.

The blades on the test hub are far too wide at the root.  Looking at them straight from the front, part of the back of the blade is visable.  That is simply way too wide to work much at all.

Another look at the 1st photo makes me wonder how close the blades match.

The better they match, the faster it will turn with a load.

The 80V with the drill turning it...  What is the name plate RPM of the drill?

G-