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Windmill direction
By windy, Section Wind Posted on Sat Mar 31, 2007 at 04:09:04 AM MST
Windmill direction

I finally got my 3 hp 3 phase motor conversion up and running and everything seems to be working ok. Not sure if it will furl when it should.I will have to wait for some stronger winds to see if that part of it works as planned. I was surprised how fast it actually turns without a load. In a 15mph wind it quickly went to about 700 rpm.Very little blade noise and no vibration. I didn't leave it run that fast for too long. With a load it runs around 400 rpm in a 15mph wind. I'm using it to heat water for household use.The one thing I was surprised to see was that the windmill turns to a different direction when the brake is released and the blade starts to rotate. I drew a little skech insted of trying to explain it. Is this normal to rotate 90 degrees when the blade starts to turn? When the brake is on, the windmill follows the direction of the wind as shown in the skech below. Here are the dimentions of the mill.

inch offset
foot diameter blade (tsr 7)
square feet of tail (1/8 inch thick aluminum)
feet from hinge to end of tail
Would any of the experts have any comments? It has been an interesting winter project and will post some pictures when I get everything done. Thanks again to everyone for all the posts and pictures. It made it a whole lot easier building my first windmill!

Windmill direction | 18 comments (18 topical)

Re: Windmill direction (3.00 / 0) (#1)
by RP on Fri Mar 30, 2007 at 09:28:28 PM MST

Do you mean it rotates 90 degrees and stays there or is it only temporary while it starts?

Re: Windmill direction (3.00 / 0) (#2)
by coldspot on Sat Mar 31, 2007 at 12:22:46 AM MST

It turns the whole tower top sideways to the wind tail and all?
Or just the blades turn out and tail stays tracking the wind? (this would be in furl).

Re: Windmill direction (3.00 / 0) (#3)
by Flux on Sat Mar 31, 2007 at 12:49:28 AM MST

There is always this tendency but not as bad as you seem to have it.

You don't give any output figures but if you are managing significant output then it will not be running at right angles to the wind.

You have a generous offset ( which is safer) but this does require more tail to keep it into the wind. Also you show it as though your whole alternator is well forward of the yaw pivot centre. I am not sure what effect this has, Axial machines are short and the normal arrangement keeps the blades much further back than your sketch implies.

There is no steering force from the tail when pointing directly down wind, the more it is at an angle to the wind the more force it produces. When operating you need enough thrust from the tail to balance the thrust from the prop acting on the offset. This means that you can't keep it directly into the wind with the tail straight back. You need to offset the tail away from the furl direction. Typically this needs to be somewhere near 30 degrees.

See if you can modify your tail stop to give you this extra 30 deg then tie a streamer or fix a little vane to the tower below the prop to give you the true wind direction and compare that with the direction the prop is facing. As it is now you will certainly not be 90 deg but perhaps you may be up to 60deg. If you put a 30 deg offset in the tail and that keeps the prop within 30 deg then it will be good enough ( you will not see any difference). If you are still more than 30 deg out then increase tail area or boom length but either way will raise furling speed so you had better establish that before you do this mod.

Running light you may have wind seeking forces pulling against your offset and the no load direction may be the other way to the true wind giving the impression that it is turning nearly 90 deg.

Flux

[ Parent ]

Re: Windmill direction (3.00 / 0) (#4)
by zubbly on Sat Mar 31, 2007 at 06:44:21 AM MST

hi Windy,

interesting observations for sure!

i looked at Alton's blade calculator as a rough guide to the rpm you are getting. in a 15 mph wind, the calculator says approx in the low 500 rpm area. it is normal for a blade to run faster unloaded. so 700 rpm unloaded sounds approx correct to me. you did mention also that it slows to approx 400 rpm under load. that sounds in the ballpark also.

just a thought, i wonder if when the unit has the brake on that the entire mill is just sort of balancing in wind direction between the prop not turning and the tail area. your second sketch does indicate that the tail is in proper position to be tracking the wind. with the rpm you are getting unloaded and loaded, i would tend to think that it is tracking properly.

Flux mentioned to attach a little streamer to the tower, sounds like a good idea. maybe even one on the end of the tail would give good observation also. (gotta be some use for all that ribbon that comes from gift packages ;)

lastly, your gen does look "extra" forward with respect to the mast pipe. my units usually tend to end up with the back of the non drive bearing housing approx aligned with the centre of the mast. hard to say, with yours more forward, it may be detremental or possibly make it better.
just kinda makes your heart skip a beat when you see it fly doesn't it :)

looking forward to hearing some results and figures in the near future.

zubbly

Re: Windmill direction (3.00 / 0) (#5)
by tecker on Sat Mar 31, 2007 at 08:33:54 AM MST

Yep a balence between the tail and blade drag.

[ Parent ]

Re: Windmill direction (3.00 / 0) (#9)
by windy on Sat Mar 31, 2007 at 08:48:41 PM MST

zubbly

I was concerned about mounting the motor that far forward, but if I mounted it to the side of the mast the way you do it ,then the offset was greater yet.About 8 inches from center of mast to center of rotor. Maybe that is why the mill would turn and speed up then turn in the opposite direction and slow down. The tail never did stay in one spot,so I thought it could be variable wind gusts. Flux's ribbon idea would tell me that.

windy

[ Parent ]

Re: Windmill direction (3.00 / 0) (#6)
by windy on Sat Mar 31, 2007 at 05:06:25 PM MST

Thanks for the all the posts. I'll have to try the ribbon idea, but first I have to take a look at the motor. Started making noise so I lowered it and the motor was so hot I couldn't touch it. It also smells like it got hot. Also sounds like the magnets rubbing. Tried to stop it with the brake but it wouldn't stop. It was furling when I last looked at it but an hour later it was making noise. Output was 8amp at 55 volt with motor wired 1 star feeding 3-240 volt 3000watt elements.Resistance between elements wired delta was 10 ohms.I wouldn't think that I had to much of a load on it. Will keep you posted.

Re: Windmill direction (3.00 / 0) (#7)
by zubbly on Sat Mar 31, 2007 at 06:45:37 PM MST

just a question windy,

how did ya mount your magnets?

zubbly

[ Parent ]

Re: Windmill direction (3.00 / 0) (#8)
by windy on Sat Mar 31, 2007 at 08:25:15 PM MST

zubbly
I mounted the magnets in an aluminum cage with high strength locktite retaining compound (color green).I didn't think those magnets would ever come out. Could it be that I had too close of clearence between the rotor and stator and when it started to heat up it expanded and started to rub? The generator was still putting out 5 amps when I tried to brake it so I'm not sure if I ruined the magnets. When I put the brake on the amps shot up to 10 or 11 amps so I knew right away that something was wrong.Not sure what the voltage was. Another question I have is, when the generator is shorted, is it normal for the blade to slowly rotate. My generator turned about 10 rpm in a light breeze(8 to 10 mph)with the brake on. But yet, without the blade on, I could hardly turn the shaft by hand. Did I do too good of a job carving the blade?LOL. Also, my voltage and amperage reading were the same as when I tested it using the tractor PTO so I figured everything was allright.

windy

[ Parent ]

Re: Windmill direction (3.00 / 0) (#10)
by Flux on Sun Apr 01, 2007 at 12:35:21 AM MST

Mount the motor above the pivot point and you can have 6" offset without that enormous overhang.

I haven't bothered to do any calculations but I strongly suspect that connected 1 star you are badly over loaded at 8A. To use it for heating in 1 star you should be up to about 300v at full current rating.

I don't want to be pessimistic, but heating from a tiny motor and small prop is only going to be much use in high winds. 55v on that 1 star winding looks near to a short circuit to it.

It is normal for the thing to crawl slowly when shorted, except for cog there is no torque at zero speed.

Think about connecting for a lower voltage.

Flux

[ Parent ]

Re: Windmill direction (3.00 / 0) (#12)
by windy on Sun Apr 01, 2007 at 08:52:37 PM MST

Flux

Took apart the motor today and just as I thought,a few magnets let go and were rubbing.The way the motor smelled it must have got really hot.Checked all the coils for resistence. All checked the same and none shorted to ground.So I think it can be used again. Before I took the motor off I looked at how I mounted the motor and my drawing is not correct.It is mounted as zubbly suggested and from the mast to the blade is 12 inches of clearance and a 6 inch offset. When I get it going again I had planned on wiring the motor to a lower voltage, but wouldn't this make the generator run faster? I guess it's all trial and error. Haven't given up yet. Thanks for the help.

windy

[ Parent ]

Re: Windmill direction (3.00 / 0) (#11)
by zubbly on Sun Apr 01, 2007 at 04:42:27 AM MST

hi windy,

it is normal for the prop to rotate 10 rpm or so when the leads are shorted in a good wind. mine do the same.

hard to say why it is rubbing inside if that is the case. lets wait till you get it apart for inspection and see what you find.

is there a link to an old story about the construction of the unit?

zubbly

[ Parent ]

Re: Windmill direction (3.00 / 0) (#13)
by windy on Sun Apr 01, 2007 at 09:31:39 PM MST

Zubbly

A few of the magnets let go and were rubbing. I think the motor got to hot and the locktite bond left go. It ruined two of the magnet that were loose but all the other magnets seem to be ok. Tried to pull some of the other magnets out of the holes but all I do is chip the magnets. So I'm not sure if the other magnets are still secure.Being that this is an experimental unit I was thinking of drilling a small hole in each magnet and secure with a stainless steel screw. I never posted any pictures of the motor but I followed your post on your 3 hp conversion. I used 48 3/8 inch thick x 3/4 inch diameter magnets mounted in an aluminum cage. One observation I made when I pulled the rotor out was that the magnets closest to the blade shows the most wear. The first row of magnets moved the stator bars a little. The next row of magnet rubbed the varnish off the stator bars but didn't move them. The third row of magnets just nicked the stator and the forth row never touched. Could it be that I didn't have enough clearence between the magnets and the stator and when the blade would yaw from side to side that it would flex the shaft inside the motor and the magnets would start to hit closest to the blade first? It's just a thought. I still think as Flux mentioned, that I was overloading the motor and it just got to hot. Winding are not shorted or open and no resistence to ground so I'll try again with this motor.

windy

[ Parent ]

Re: Windmill direction (3.00 / 0) (#14)
by Flux on Mon Apr 02, 2007 at 08:46:02 AM MST

I think your clearance may have been on the small side to start with,

I also think the overheating will have caused the aluminium to expand and also the bond strength of loctite falls with temperature .

At least you stopped before you bent the slot teeth over enough to cut the slot liner.

With that sort of power out you can't have been at 90 deg to the wind.

yes a lower voltage connection will increase the speed, particularly in light winds where it doesn't matter as there is no useful heat. In higher winds the effect on speed will not be very great, what you do is transfer the power generated from the stator to the load, the power produced by the prop doesn't change that much. You need a compromise and I think you will need to compromise a fair bit with just a fixed load. The fact that you are not stalling now makes me think that your blades are plenty powerful for that alternator so watch that you can furl within its rating.

Flux

[ Parent ]

Re: Windmill direction (3.00 / 0) (#15)
by zubbly on Mon Apr 02, 2007 at 05:41:05 PM MST

Hi Windy,

what you described about the rubbing of the magnets being progressively worse from the fourth row to the first row sounds like a classic case of a worn bearing housing journal.

an easy way to check it: remove the bearing from the shaft. wipe it off good and also wipe out the jounal in the bearing housing with some solvent. insert the bearing into bearing housing (slight tap with block of wood if necessary). next, stick your finger in the middle of the bearing and see if it slides up and down easily, and also if there was any sign where the bearing sits in the journal, see if you can rock the bearing at all. if it does rock, your housing is simply worn and needs to be rebuilt.

remember that your rotor has very little clearance from the stator laminations (approx .020 inch originally) and under stress from the prop, will allow the rotor to rub. also be observant when you pull the bearing from the shaft-it should be tight and hard to pull.

other possible problems are mag sitting high in cage, loctite surfaces not degreased when loctite applied, or air gap between mags and stator too small.

personally, i would not worry about the current at all. your genny will take excessive current without overheating the winding. the thermal transfer from winding, to stator, to frame, and all the wind from the prop is what allows conversions to be pushed hard.

if the genny is being driven by other than prop (belt driven-pto driven) then it is a different ball game all together.

my 7.5hp conversion has recently been charging a 60 volt batt bank (connected 1 star). have often seen constant current between 30-45 amp, and the occasional 60 amp plus peaks.

my small 1.5hp conversion is also connected to the same 60 volt bank and have seen constant 10-15 amp, and 25 amp peaks.

TomW is also running a small 1/2 hp conversion (24 volt) with common 5-10 amp 30 amp peaks.

My brothers 1/2 hp conversion commonly ran constant 30-40 amp (12 volt bank) with 60 amp peaks. some time ago it threw a mag and i have yet to repair it for him (fibreglass cage).

lastly windy, i have drilled quite a few neo mags. (they are a total bitch to drill and a hell of a mess to clean up)

wish you luck with getting your gen back up,

zubbly

[ Parent ]

Re: Windmill direction (3.00 / 0) (#16)
by windy on Mon Apr 02, 2007 at 07:48:47 PM MST

Zubbly

I tried drilling one of the ruined magnets with a carbide end mill bit in a drill press and it drilled right through like a sharp drill bit through iron. Used plenty of oil and the magnet never got hot. Now if I could only find an easy way to clean up the magnets. I'm going to try to locktite the magnets in again and turn the rotor in the lathe and make sure that all magnets have the same clearance. If I lose a magnet again then I will drill and fasten them with countersunk screws. I spun the rotor at 1500 rpm and all remaining magnets stayed in place. I'm not sure if this is much of a test.Could go up to 4000rpm but don't think that would be necessary. I will check the bearing housing journal but I think it is alright. I had to tap the end bell all the way off when I took it apart and when I installed the new bearings they had to be pressed on. Will post some pictures of the blade and tower this week.

windy

[ Parent ]

Re: Windmill direction (3.00 / 0) (#17)
by alancorey on Tue Apr 03, 2007 at 01:13:09 PM MST

I had to grind some neos once to reduce cogging, and I cleaned up as a 2-stage process: (1) push the dust into a pile on a corner of the magnet with your fingers, then pinch it off and drop it whereever. When you've gotten off as much as possible that way (2) sit down with the magnets and a roll of masking tape. Use the adhesive side of the masking tape to pick the dust off, then when that piece of tape is full tear off a new one. Tedious but it worked.

Alan

[ Parent ]

Re: Windmill direction (3.00 / 0) (#18)
by windy on Tue Apr 03, 2007 at 08:12:47 PM MST

Alan

I'm planning to grind my magnets to increase clearence between stator and rotor. Using your tape idea should help with cleanup.
Thanks for the tip.

windy

[ Parent ]

Windmill direction | 18 comments (18 topical)

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