Treadmill Motor PVC Blades

[packman1234]

Hi

I built a wind generator with an IMAGE variable speed dc motor from a treadmill--Part no:22345500

Motor specs: 2.5 horsepower v.arm-130   a.arm-15.3   rpm-3200  ENCL-OFC  Class Insulation-F  Model no:4640D-51A.

I basically followed the instructions for building the Chispito Generator. I used 6" pvc for 3 blades that are 29.75 long. The diameter is 54" from outer tip to outer tip. The tips are 1.25 wide and the root attached to the rotor is 6".

When I spin the shaft on the bench by hand, it gave me 6v. When I spin the blades attached to the rotor by hand I get about 2v.

My problem is this-----I cant get this to startup in the wind. I tried 2 box fans and it moved about a quarter of a turn and stops(that was aiming it in all sorts of directions) I grabbed my 150mph leaf blower and it spins with that-but not real fast! What am I doing wrong and how could I improve this. All I want out of it is 100watts for simple battery charging and maybe a shed light.

Any help getting me in the right direction would be appreciated!!

Bob

[packman1234]

I forgot to mention the hub is heavy!! It is 7 " diameter and 1 1/8 thick.

The motor and hub must weigh about 25 pounds....

[roadranger]

The 260V 5000rpm motor that 'mill is designed for has a cut-in speed of 375rpm, near as I can calculate your motor has a cut-in of 480rpm. Your rotor is bigger (aka slower) than the original 48" one. So, your mill will have to have a wind about 1.5x what the original would work in. I calculated out a faster blade for my Chispito:

Optimized 4 foot windmill rotor made from 4" Schedule 40 PVC pipe. For CCW rotation, root of blade 3/4" from the center of hub, TSR of 8 @ 5 degrees AOA, loaded RPM 375@6.7MPH(3M/S) 1232@22MPH(10M/S):

Cut a 23-1/4" length of 4" Schedule 40 PVC pipe lengthwise into 4 equal pieces.

Take one and lay the inside of the pipe down and oriented left (root) to right (tip).

On top-left hand corner drill a 1/4" hole 3/4" from the left (root) and top (trailing edge).

Drill another 1/4" hole 3/4" to the right of that hole.

Mark the right edge (tip) at 1-5/16" from the top (trailing edge).

3. " from the right (tip) mark it 1-7/16" from the top (trailing edge).
   
6. " from the right (tip) mark it 1-5/8" from the top (trailing edge).
   
9. " from the right (tip) mark it 1-13/16" from the top (trailing edge).
   
12. " from the right (tip) mark it 2-1/16" from the top (trailing edge).
    
15. " from the right (tip) mark it 2-7/16" from the top (trailing edge).
    
18. " from the right (tip) mark it 3-1/8" from the top (trailing edge).
    
    

This should be 5-1/4" from the left (root).

"Connect the dots" with a smooth curve. Use a french curve if you have one.

Cut the bottom part off and discard.

Sharpen the top (trailing) edge on the inside only! Do not sharpen the 3" on the left (root).

Round off the bottom (leading) curved edge and the tip.

[CmeBREW]

Hi Packman,

    The 54" dia sounds reasonable. Would you happen to have a picture? It could tell us a lot.  Sometimes 'beginners' can make the PVC blades backwards, with the big angle out at the tip, and a small angle in toward the root.

I've made pvc blades out of the 6" pipe and it seems to me that 6" wide at the root is too much curve (excessive drag) hanging over.  I think that would be like 3" wide.  The blades I made were 3.25" at the widest point.  

The cogging of those motors can be a real pain I know. Small mills have to be able to start on a feather and this is difficult to do with 4 and 5 footer DC motor mills.  

I would try 5 thin  pvc blades (same 54" diam) myself.  It would give it  a lot more start-up power. (but it won't mean any more power though than 3 blades)

The other thing that can cause big start-up problems is balancing. I find It is impossible to balance the blades with the DC motor itself due to the cogging. I always just use a bronze bushing in wood separately, to balance the prop more accurately, or you can take the rotor out of the treadmill motor and hold on to the two ball bearings and balance it that way very well also.

-Just some thoughts. You'll get it soon!

[packman1234]

Thanks to both of you for the replies!!

I want to do the second set of blades right..I have to comment first on Roadrangers reply. When I got to the part in the instructions for making the blades, I followed this link and made them from  six inch pvc cut at 29.75 length and divided into two 150 degree pieces and one 60 degree piece..... http://www.thekevdog.com/projects/wind_generator/

My holes on the hub are 1" apart and 1 7/8 from the shaft center.

This Generator spins CLOCKWISE because I got negative voltage readings going Counterclockwise. Are the Instructions you gave me correct for the info I just revealed?? Can you also tell me how you arrived at the cut-in speed of 480rpm for my machine- I'm learning and am confused at all the reading I've done!

How many watts can I get out of this and is this motor feasible for this project?

I did not finish this by any means...Just set it on a stand to see if it spins before proceeding to the next level.

To CmeBrew---

The blades seem balanced fine..They do not stop at the same spot when spinning it manually.

I really appreciate the help-Just need a little bit more to keep going!

Bob

[packman1234]

I did upload a picture to help you guys.. It is in my user info, I beleive...

[TomW]

Rob;

This Generator spins CLOCKWISE because I got negative voltage readings going Counterclockwise.

If it is a brushed motor just reverse the leads. Unless I missed something.

Use its negative as a positive. That way direction of rotation matters not. Just use the "most positive" lead as your positive lead. Or feed it into the AC side of a bridge rectifier and it will just be right on the DC side of that.

Tom.

[packman1234]

Tom

Dont get me all confused!!

Is it ok to have this unit spin clockwise? The new design of my blades will determine this..The voltage readings I get make no difference when reversing leads and spinning it clockwise and counterclockwise.

Bob

[roadranger]

The "original" motor has a flywheel/fan on the shaft that is screwed on with a left handed thread. If you mount a "clockwise" rotor on it it will unscrew and fall off when you "load" the motor. I don't know how your motor is?

[roadranger]

For a good guess at the cut-in of your motor I took the "original" 260V 5000rpm motor's documented 375rpm cut-in and corrected it for the different voltage and rpm of yours:

( 375rpm / ( 5000rpm / 260V ) ) * ( 3200rpm / 130V ) = 480rpm

[TomW]

Bob;

I am speaking from purely an electrical standpoint.

I do not know the motor and another poster notes their could be mechanical issues with reversing it.

Not sure what you mean by "The voltage readings I get make no difference when reversing leads and spinning it clockwise and counterclockwise."? If the polarity of the voltage does not change with reversing directions then something else is going on. It is not easy to get a handle on what a poster understands.

Sorry I even jumped in.

Sorry to confuse you. Really.

Tom

[roadranger]

You can - of course - change the mounting hole positions lengthwise along the blade to match your hub and adjust the length at the root to give you exactly 24" tip to center of hub. The positioning of the holes at 3/4" in from the trailing edge is critical to get the right angles along the blade. It is also very important to sharpen the blade only on the inside of the pipe (toward the wind) to get the proper angle of the blade.

[roadranger]

As for the suitability of this motor - if you are in a high wind area (20-30mph) it would be OK with a proper 4' rotor. In a 10-20mph area I think you'd be better off with a 3' rotor (for more rpms) and look for max 40watts at 20mph, maybe 5-10w at 10mph? To scale the blade down for a 3' rotor multiply the lengthwise measurements (distances in from the tip for each "mark") by 2/3 but leave the width measurements as-is.

[CmeBREW]

I see your pictures.  It looks like you made the blades correctly to go clockwise. As Roadranger says, make certain the heavy 'flywheel' screws ON in the clockwise direction and it will not come off.

Question---Do you have the motor hooked up to anything? When testing, it is unhooked--- right?  Because it seems to me, with those VERY wide blades, at that very big angle, it would start up VERY easy.  It confuses me.  I suspect it will be very difficult to get the high speed you will need with those wide pvc blades hanging over that far near the root side.  

I would trim off 2" off the width and add a couple more blades myself.

Have you actually tried to test the mill in the wind outside? The REAL wind outside is probably better than box fans or blowers.

Perhaps you can make sure the motor is not semi-shorted out or something by hooking it up to a 12v battery directly and letting it spin.  It should turn with some fairly good force around 400 rpm.

It is a puzzlement.

[packman1234]

Ok Guys....Have to clear up some things.....

The hub slides on the shaft with a key and locks down with an allen screw. NO threads are involved here!

I did test it in a 10mph wind and no go.. The 150mph leaf blower was the only thing that could make it spin continuously. When hooked up to 12v it spins very nice-slight wobble on hub.

I still need to know the voltage this is capable of producing in a 10-15mph wind--or even a 5-10mph wind.....I thought the cut-in is = rpm/voltage*cut-in voltage(13v for weak battery) Based on that i figured...

3200/130=24.615*13v=319rpm . Does the swept area need to be calculated in this also??

I figure with this current setup, I have 63.62 sq ft swept area.

Please help me confirm all of this and come up with the perfect blade design. Is the 4inch pvc the way to go? I'd prefer the 3 blade setup if possible.

Again...Thanks for all the suggestions and help

Bob

[packman1234]

So much info here..

I guess my question is this- Should I try making a mark 2 inches in from the root on the leading edge and draw a line on the existing blades to shorten them to 24inches? If so- How wide should the tips be?

Or...

Should I start over with 4inch pvc and make them shorter than 24inches? Would I just cut the 4inch in half and use the halfs to make quarters? If so-where would I draw the line to narrow them?

It all comes down to this...The wind speed here averages 9mph. I need something that would be useful in slower winds and still be able to charge a battery or two- Can I do this or is this a waste of time with this motor?

I also have a woodshop in my basement and have not ruled out making wooden blades out of laminated hardwood...what are your thoughts on all of this???

Thanks for all the great info!

Bob

[roadranger]

Motors have losses so as a motor the rpms will be less than some theoretical and as a generator the rpms would have to be more than the theoretical. My motor has been documented as running no-load at 2000rpm at 100V but needing 2800rpm to generate 100V.

[roadranger]

The amount of power in the wind rises at the cube of its speed. A 30mph wind has 64 times the power as a 7.5 mph wind. To get 100w at 7.5mph would need a windmill with maybe a 24 foot rotor and 6+ blades and a 32:1 gearbox. Below 10mph solar would be a better solution.

Oh, and most folks say wooden blades are way better (2x ?) than pvc - but I don't know of any comparison using a properly calculated PVC rotor. A properly carved blade will always outperform any "pipe blade" but I don't know by how much?

Cutting a PVC blade that "looks good enough" as the how-tos show and expecting optimum results seems a bit silly to me. If you are interested in seeing the most annoying presentation of the proper design of a pvc blade you are likely ever to see check this out:

http://www.youtube.com/watch?v=BawUfbDDvtA

I calculated mine in a similar fashion but i think I compensated for a couple issues he overlooked. For instance, how you sharpen the trailing edge has a large effect on the blade angle, especially out near the tip which can be going 160mph in a 20mph wind!

[packman1234]

Roadranger

That video turned me off!

In your opinion, should I scrap this idea(Thats all I really wanted to know)

I would like to try something with it and was hoping for a more doable solution with the 4inch or cutting the existing blades shorter and narrower.. Could I try that and see what happens..

if you had this---what would you try to at least get it to spin in a 10mph wind.

Thanks for your opinion

Bob

[packman1234]

I just tried cutting the existing pipe to  24" long  1  5/16 at tip and 4" at the root with the same bolt holes and it still wont move!  BUMMER!!

Is the 4" the way to go or is it cogging too much to do anything??

Help!!

Bob

[Baling Wire]

I have an "Image" treadmill motor that is very similar.  I believe that your 12.2 volt cut-in will be close to 440 rpms based on the ratings of my motor.  They have quite abit of brush drag and the HEAVY fan/hub do NOT contribute to it starting easily.  A lot of weight in that hub to get moving from stop!

You will be hard-pressed to get any charge under 10-11 mph due to the higher cut-in rpm.  300-350 rpm at cut-in would be much better.  I would get a much lighter hub and try the pvc blades at the 54" diameter you have.  If after the hub change, it starts alot better, then you might look into changing the blade design a little?  Pvc blades may not "turn-up" enough rpms to make it work for you.  A good 4.5 to 5 ft. dia. Fast wooden prop might? work out ok. Good luck!

BW

[roadranger]

It really should at least spin as-is in a 10 mph wind. I'd first try to balance it better using a piece of shafting and a couple ball bearings. Some have taken their motor apart and just used the armature with it's bearings to balance with but you'd have to convince yourself that you know how to get it apart and together without messing up the brushes. Then with this motor I'd try the 3' version of my rotor first. Then if you are up to carving wooden blades I'd search around a bit for the measurments and go for a 3' rotor designed for a TSR of 8. I don't think a 4' rotor can ever be fast enough to work well under 15mph.

Where did you get your motor? The eBay 130V "windmill" motors are all 6750rpm which is completely unuseable!

[packman1234]

Baling

Thanks for the encouragement!

Did you ever get the "Image" you have to work with a lighter hub?

Where would I find a hub like that to fit on the shaft?

How light would you go if I could get someone to make me one?

Now that I cut the blade length to 24", I'd like to start there(Made no difference in my testing whatsoever)

I am NOT giving up on this...I will have a BIGTIME smile just getting this thing to spin! I am pretty frustrated at this point though.

Should i keep the motor or try something else to get my spirits up?

Thanks

Bob

[packman1234]

I got the motor out of a Sears treadmill that my sister had.

I took it apart a few times to replace the two bracket mounting screws and see what it was all about..No biggie playing with this-Very strong magnet and sucks the case end in super hard and tight!

Bob

[roadranger]

A lot of brush drag could be a problem but a heavy hub shouldn't be. My "originally spec'd" motor has a very heavy fan/flywheel and works fine - but I am tempted to cut off the fan blades and thin it out a bit in the lathe to reduce the weight of the 'mill. I don't remember if you checked to see if the motor had less brush drag in one direction - some do. My motor turns easily with some cogging but not too bad.

[roadranger]

Just for reference this is the "originally spec'd" motor:

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&rd=1&item=220008972818

[packman1234]

when i took the motor apart, only one bearing stayed on the shaft..The other was in a housing.

Bob

[wooferhound]

packman:

What do you have the wires from the motor hooked up to. For your testing I would not connect them to anything. Tape off the ends and leave them hanging. If you are trying to power up anything it will make the motor drag.

[packman1234]

Thats not even close to the one I have,,,specs are but hub is bigger and not threaded.

Mine is 2.5hp at 130v at 3200 rpm

[packman1234]

Not hooked up to anything!! Just 2 blue and a red and black hanging down the side!!

Bob

[packman1234]

I'm sure this thing will work in the next tornado we get around here!!

Quite Frankly...I cant wait!! lol

[CmeBREW]

Sorry you are having so much problem.  I suspect the great majority of us faced that dilemma when starting out.  And it don't stop there-- there are many other dilemmas with wind mills. (I am still learning!!)

If it were me and I had no other choice, I would do 5 pvc (or, wood blades would be somewhat faster) blades (6" pipe)  4.5' diameter (you may wish to trim them down later to get more rpm).

I would make the pvc blades 3" at the widest point, and 1.25" at the tip. (tip being 4 degree angle almost straight up and down)

And You might want to try a "Magnetic de-cogging mechanism" like I did on my treadmill motor mill here:

  http://www.fieldlines.com/story/2007/3/9/2533/99152

Your motor probably has 12 poles and thus 12 big cogs per revolution.  So you would need only 12 little magnets. (guess- 1/2" diam. by 1/8" thick ///and use big pan head wood screws or similar)

The objective with the 12 magnets spaced correctly is to make 24 smaller cogs per revolution instead of 12 big ones.

It is difficult to say, but if you understand the principle well, you might reduce the cogging anywhere from 20-50 percent.

Be very careful to get your alignment exact, or it could make the cogging even worse!

Mine worked quite well for a time, but during a 'hurricane wind' (probably 70mph gust) it screwed the hub on even tighter than I thought possible, and screwed up the alignment an eighth of an inch and worse cogging came back. (I never fixed it with a 'sheet metal washer' because I knew I was going to take it down in the spring and make a bigger mill)

I took that downwind mill down earlier this year since I didn't need it any longer since I have a 6 footer now.

(If anyone ever makes one of those downwind mills, be SURE to put a wood or plexyglass 'beard' mounted below and to the motor in order to help it turn (yaw) better in the lower winds!!)

I sorta like the heavy hub though.  It seems it helps to keep it turning in lower winds better and  keep it from stopping as much from the cogging.  Inotherwords, it seems it smooths over the cogging better in low winds and 'coasts' the prop better.

Wait for a 10-20mph wind day and see what it does.  4 footers don't do anything under 10mph.  My 6 footer only gets 'bits and pieces' of low wind on a typical 5-10mph day which amounts to almost nothing anyway. (maybe 10-50Watt hours??)

-Just some ideas. Keep trying-- we all had the same headaches!  

[CmeBREW]

Sorry-- I meant to say to use FLATHEAD wood screws instead of "Panhead wood screws".  I doubt panhead (roundhead) would work good since it would cause Too much of a 'cog' at the magnets.  But it's up to you to figure out what might work the best.