What is that wierd scraping screeching sound?

[Tink]

I do have an email into Dan about this and I realize he is a real busy guy so I'm posting this to get any advice from anyone else in the meantime.

I got the 10' kit from Dan and put it on a 40' tilt up tower. It has been working great for the past 6 months. Until a few weeks ago we had a few days of 'off and on' 60mph winds. I don't think the turbine was furling properly because it didn't seam to come out of the wind correctly. I never saw it go above 32amps on the meter and at that for only a few seconds. It did run at around 25amps consistently though a few times. At my calculations that may be about 935 watts at 29.2 volts when it was running at 32amps and about 730 watts at 25maps  So did I burn up my stator? Funny thing is I hear this scrapping screeching sound but not always. The machine produces AC just like always. I see no decrease or increase in the output. I've had it down twice now to see if it is rubbing anywhere and it isn't. The first time I had it down I did tighten up the bearing since it was a tiny bit loose. So the second time I brought it down I tore it apart and noticed a small burn spot on one of the coils and a bulge on one of the wires and weird raised dots of what looks like melted electrical tape on one of the coils. The tail and yaw bearing move smoothly without any rubbing and there is no sign of any scraping or rubbing anywhere. I'm including pictures of the strange spots. So, is it possible to continue to run this without destroying the rest of the turbine? The rotors look perfect. And where is that horrible sound coming from? Is the stator repairable? I'm not putting it back up until I know what is going on with this and take the necessary steps to correct it. Should I make a smaller tail so it will furl easier and at a lower wind speed. As it is now it furls wildly and never stays furled when it seams it should. I really don't think there is anything wrong with the mechanism since it moves freely and smoothly when I have it down Any help and advice on this is greatly appriciated.
Tink   




I fixed the photos so they display in the post please go read the updated "posting photos" sticky in site news.
Kurt

[Boss]

Those look like solder joints failing

[TomW]

Do not mistake me for an expert or even very experienced.

I am not seeing the photos and looking at them takes several steps I don't feel like taking.

However.

My 10 footer exhibited similar symptoms plus being occasionally stopped when it should have been spinning.

The cause was a displaced [loose] stator rubbing the mag rotors. It was cocked at an angle between them and worked fine when it worked. 

I bet a buck that is the sound. Mine worked fine but had this intermittent stuff happening. If that is the cause I would shut it down and lower it before it damages the stator. Luckily I caught mine early. Something about watching turbines rather than TV.

Just my experience with similar symptoms.

Tom

[defed]

I am not seeing the photos and looking at them takes several steps I don't feel like taking.

i liked it so much better when the attachments showed up in the message.

[freejuice]

I'm still very new to the game, but does your stator have any circular wear marks....as if it warpped into the rotors while turning?

If you cannot find any wear marks, takew the bearing out and degrease it and inspect it for wear, if none reassemble, and check for end play by puylling up and down on the bearing/rotor hub., tighten as neecerssay

[Boss]

hehe

Those look like solder joints failing

I opened them with Explorer, one step btw. I can see the burned tape around the coil joints through the resin of the stator. Of course I am not there, and I didn't make those connections, I could be wrong, it is an educated guess on my part. I have a history of silver, lead, and bronze soldering all sorts of joints for decades.

[Tink]

I appreciate the comments, thanks. But as for the loose stator that is not the problem here since all is tight and there are no wear marks at all. The whole thing turns smoothly. The stator is well aligned. The air gap is very uniformed all the way around. There are no marks at all on the rotors, they look perfect. I looked at the front bearing and  it is fine but I did turn the big nut about a half turn to take up some slack and put the carter pin back in then repacked it with grease. It turns smoothly. I did a few times, push up and down on the hub and felt no play at all now. I haven't looked at the rear bearing since the darn thing turns so smooth I can't imagine  anything wrong with that one. The only thing I can see is the spots on the stator that don't look right. By the way when I click on the photo files my picture viewer comes up and asks if I want to view them with 'Picasa Photo Viewer' I don't know where that came from but it works. Maby my next step is to take the hub apart and degrease and inspect and reassemble and make a smaller tail so it furls sooner. I'm still confused...
Tink

[Flux]

I see no reason for your stator to cause the noise. I do think you may have a poor connection somewhere ( could be the star point) but it may not be serious. I think the black blobs on the coil are results of some pvc or other useless tape that is incapable of sustaining the temperatures these stators are asked to run at, it makes a mess but may be harmless.

The noise may be an indication of bearing trouble, I have had similar when a roller cage starts to run dry or disintegrate ( water ingress or cheap Chinese bearings may be a reason).

I think you can ignore the black blobs over the coils but I would be tempted to dig into the moulding and have a check where that burn is near the outside, if it is a poor connection it will get worse. I don't see any evidence of burnt coils but I strongly suspect you are stall limited and not furling. May help to try to reduce the maximum current especially if you don't feel inclined to investigate that likely bad connection.

Flux

[Boss]

I guess in my own convoluted way I am saying the stator is suspect. Check resistances of each phase, I imagine that burned solder joint will show up as greater resistance, on that leg. If so the stater will need to be replaced.

[Dave B]

The noise is secondary to your obvious problem. Your machine ran too long above it's rated continuous output. Your stator has suffered damage. Tear it down and replace your bearings and races and regrease and properly tighten and secure your spindle nut. Check for smooth operation then replece your stator and adjust the gap and secure your stator using locktight or a similar way to make certain your stator will not move. If your gap is set very close I would bring it back down after a few weeks and re-check and adjust your bearing run out and make certain your stator is secure. Make sure your yaw post and tower is vertical and you will need to adjust your furling to happen (fully furling) so that this happens before you reach your rated output of your machine. Ask the Dans what they suggest for a continuous safe rated output (all day long) You have experienced good continuous wind, this will burn up any machine every time if it's running at it's "peak" rating for an extended period of time. Sorry for the straight up comment, if you try to band aid your problem you will have trouble again. Your machine needs adjustment and replacement parts to run for a long time no worries.  Dave B.

[Dave B]

One more thing. I highly suggest you use the hub grease seal and a new one also when you replace your bearings and races. These bearings can easily run over 100,000 miles annually at a good site. I've been there done that, left the grease seal off after balancing the blades on the hub. Haste makes waste, those bearings didn't make 6 months. Water got in, rusted slowed right down and was a real mess, over heated and the whole game. Leave your grease seal on !  Dave B.

[defed]

I opened them with Explorer, one step btw.

firefox (on linux) only asks me to save or cancel when i click one.  then i have to delete them after i look at it.  can't seem to figure out any other way to open them.

[Boss]

Interesting about the seal, makes sense, Dan told us it created unnecessary drag, live and learn

firefox (on linux) only asks me to save or cancel when i click one

I happen at this time to be on our only Windows PC running Firefox, I got the open with option, the only thing setup on this loaner PC (our livingroom PC blew up a power supply, and we decided not to fix it again) is Explorer for viewing JPGs so I choose it. 
Bingo

[Dave B]

I should have also mentioned about the dust cap as well. I'm sure there are plenty of machines running without the grease seal and or dust cap or both. Moisture getting in will kill a bearing quickly as of course dirt can as well. I would bet that if you left the grease seal and or dust cap off a trailer bearing it wouln't make it 100,000 miles without maintenance even if you didn't dunk it in the lake now and then as maybe with a boat trailer. Sure, up in the air might be a fairly easy environment for the hub compared to out on the road but the few more watts generated over time by leaving the bearings exposed sure could cause a big headache and a lot sooner than expected needing a complete tear down and replacement before it would normally be due. I am soooo glad I learned from this a long time ago.  Dave B.   

[ruddycrazy]

I have said it before and I'll say it again as it seemed to lost in a thread.

Tapered bearings ARE designed to run with the rollers contacting the rear seat on the cone, so for a wind generator using trailer hubs the bearing SHOULD be set to a light pre-load. If tapered bearings are loose in operation the roller cages will become damaged then the bearing will fail in short order. Just about every RE guy I know loves fishing and would own a  spring based fishing scale. To set the bearings on a trailer hub for a wind generator, wind some cord around say the front magnet disk then tighten the locknut until there is a couple of pound on the scale or the scale just showing some weight. Then find the closest opening on the castellated nut  and if it closer on the tight side all the better set the bearing with some pre-load. As far as worrying about the rear seal causing drag just coat the inside of the seal and the seal journal with a liberal amount of grease and be done with it.

With the amount of gearbox's I repair most of the damage to due to in-correct bearing bearing adjustment which will cause failure EVERYTIME.

Cheers Bryan

[halfcrazy]

the stator looks fine to me I see the connection taped up and it was against the side of the mold so it shows threw but i do not suspect that has any bearing on it. If you where hearing a loud screeching noise then the stator would be wore into the coils somewhere. The 3 things to look at or do that I would suggest are:

1-replace both bearings and races and grease as well as add the seal lightly loading the bearing as stated
2-grease the yaw bearing and cap and bushings very well they will make a noise when the turbine tracks the wind
3-grease the tail bearing well

[Tink]

Kurt,
Thanks for fixing my photos! I'll read that post.

halfcrazy,
I will do as advised as that seams to be the next logical step. I actually have done all that the first time I took it down except the rear bearing I didn't check since it all moved so smoothly on the ground. Maby the rear bearing only makes noise under pressure.

ruddycraxy,
What you are saying makes sense. I did notice when I got the completed kit from Dan the bearings were a bit loose and I didn't tighten them, that may be the mistake I made and maby the bearings are worn prematurely.  The dust cap and the grease seal were on. I'm assuming the grease seal is the large washer that goes between the bearing and the large nut with the carter pin?

Boss,
Now I'm confused, what is the grease seal? I also read somewhere that Dan said not to use the grease seal cause it causes drag. Since mine is an assembled unit I may have not gotten the grease seal.

Dave B,
I do value the comments! So do you think my stator is not repairable? After some serious thought on the matter I do believe I ran the turbine to long at too high a speed. I realize I must adjust the furling, any suggestions on that? Do I make a smaller tail vain? I'm using the one that came with the kit.

Flux,
Looking at the diagram in the book am I correct in assuming the star connection is where the black bulge is in my 1st photo? Should I dig into the burn spot on the 2nd photo to try to repair that? I didn't build this unit from scratch but I am seriously thinking about building a stator if for no other reason than to have a spare and also for the experience. So are you saying I could have a bad connection at the star point and a bad connection where the burn is on the second photo?

To all,
Please forgive me for my inexperience, I'm still learning and all this feedback is very helpful.

Tink

[Dave B]

Tink,

  The grease seal is at the rear of the hub, it is not the spacer washer under the nut at the front of the hub. It has a rubber seal and usually a spring around the inside of it holding the rubber firmly against the spindle. This grease seal has a metal ring and is usually press fit into the seat for it at the rear of the hub. When you slide the hub on this rubber seal makes contact with your spindle. If thiis is not happening when you first slide your hub on the spindle then you probably do not have a rear grease seal installed. Unless you plan to replace your bearings and races (cones) often enough to beat the destruction then I would most certainly install this seal after replacing your bearings, races and new grease. As other's mention, the tapered bearing and your hub should not be loose, read up on the proper adjustment of this type wheel bearing.

  All I am going to say about your stator is that it has experienced damage and that my suggestion is to replace it. I know this is not the easiest thing to do because of possible cost and or negotiation about how and why etc. Speaking strickly from a service and repair stand point I would replace it but NOT until after you have made some adjustment to try to get you machine to COMPLETELY furl earlier and before putting it back in the air.

 These machines have many variables and the location can have a big impact on their performance and saftey also. Not to mention all the installation and application variables as well that can and do affect their performance. These are systems and not always a one size fits all. You will be happy when all is tweaked to your own set up.  Dave B.

Kurt,
Thanks for fixing my photos! I'll read that post.

halfcrazy,
I will do as advised as that seams to be the next logical step. I actually have done all that the first time I took it down except the rear bearing I didn't check since it all moved so smoothly on the ground. Maby the rear bearing only makes noise under pressure.

ruddycraxy,
What you are saying makes sense. I did notice when I got the completed kit from Dan the bearings were a bit loose and I didn't tighten them, that may be the mistake I made and maby the bearings are worn prematurely.  The dust cap and the grease seal were on. I'm assuming the grease seal is the large washer that goes between the bearing and the large nut with the carter pin?

Boss,
Now I'm confused, what is the grease seal? I also read somewhere that Dan said not to use the grease seal cause it causes drag. Since mine is an assembled unit I may have not gotten the grease seal.

Dave B,
I do value the comments! So do you think my stator is not repairable? After some serious thought on the matter I do believe I ran the turbine to long at too high a speed. I realize I must adjust the furling, any suggestions on that? Do I make a smaller tail vain? I'm using the one that came with the kit.

Flux,
Looking at the diagram in the book am I correct in assuming the star connection is where the black bulge is in my 1st photo? Should I dig into the burn spot on the 2nd photo to try to repair that? I didn't build this unit from scratch but I am seriously thinking about building a stator if for no other reason than to have a spare and also for the experience. So are you saying I could have a bad connection at the star point and a bad connection where the burn is on the second photo?

To all,
Please forgive me for my inexperience, I'm still learning and all this feedback is very helpful.

Tink

[Flux]

From what I could see from your pictures the coils show no sign of overheating but there is signs of a lot of heat at one point. It is either the connection to a coil or more likely the star point where all 3 coils join. If you didn't build the stator you may not know what is buried at this point. A bad connection usually gets worse and if possible I would try to dig away the resin at this point and investigate.

Either way I agree with DaveB, use this existing stator until you get the furling right. If you can fix the connection I would carry on using it. If you can't fix it it may still work for a long time but it may be wise to build a spare stator as back up.

In dry areas it is likely practical to use the bearings without any seal but in wet areas it is better to have a seal fitted, the surest thing to kill bearings is rusting from moisture entry.This is the only cause of failure I have found from decent quality bearings. If you have cheap imported then you may have failure without water entry.

The seal does affect start up if tight, sometimes it will bed in and not be a problem after a run in period. If very tight and you have a lathe it is usually possible to skim a little of the track where the lip runs but you may not be able to do this once you have mounted the spindle.


Unless you find red rust in the bearing and it is obviously a water problem I wouldn't be too worried about the lack of a seal, you will have a better idea when you strip the thing.

Flux

[ChrisOlson]

Unfortunately, my camera does not take good close-up pictures but I tried it anyway:





If you could see it first-hand it looks like it's burned in a couple spots.  But it's not - this stator has never been run yet.  When you use black tape to hold the coils together and insulate coil interconnects the resin melts the stuff when it cures and coil heat will bubble it and make it look like you have a burnt spot in the stator when you really don't.  It's no big deal - the tape or whatever you use to hold the coils together is only there until you get it encased in the casting.  From that point on the stuff can disappear and it don't matter.

It sounds to me like you got either the cotter pin not bent over correctly and it's scraping on the grease cap, or you got a problem with a bearing (cage came apart or similar).  I guess I've never seen a stator actually get hot enough to burn something critical black and crispy and still work.  And I've burned up my share of 'em.  I think all you're seeing is black tape that got melted in the stator, which is completely normal if black tape is used to hold stuff together during assembly.

I usually paint my stators with a red oxide epoxy primer to seal them from the ravages of weather and UV damage.  Do that, and you'll never worry about it because you can't see inside it.  You either get power from all three phases or you don't.  If you do, the stator is good - bolt it on and run it.  If it drops a phase then it's no good - so you build another one.  With a small turbine like a 10 it's not a big deal.  You can build a new stator for it in one afternoon, you're out 50 bucks, and you got it flying the next day again.
--
Chris

[dlenox]

Tink,

You did not state if the noise was synchronous with the blades rotating or not.  If not then it could be the pivot for the tail bearing lacking some grease.

At one time I had a similar issue, it was noticeable only when it was low wind, and the direction changed - thus moving the tail and causing a squeaking.  If not the spindle/hub then I'd suspect either the yaw bearing or the tail pivot bearing.

Dan Lenox

[DanB]

oh dear... ;-)
I've been 'gone' for a good bit and this is pretty interesting.
Please send me another email about this (danb *at* otherpower.com)

I've had either no time or no internet connection for about 10 days here lately so I've not read all my email, or the board, and those I have have not got much response.

In short, can't say about the noise.

I could be wrong, but I do disagree with the comments about running with a tight bearing - I think it should be a bit loose.  If the bearing has failed though that will be interesting - I've seen that happen once so far.

To me, the stator really looks fine.

You may have mentioned the voltage of the system, I've not caught it though, I'd be curious to know.  32 amps sustained is about what I'd expect for a 24V machine and it should be fine there.  If it's a 48V turbine, that's too much power and it's furling late.  That *could* be a design issue or it could have something to do with the machine running a bit too fast I think, which I think could be caused by high battery voltage or too much resistance in the line.

DaveB..  I really could be wrong here, but I hate putting seals in 10' wind turbines, the friction is too much and it really hurts startup and output in low winds.  I've had lots of machines going for years now with no back seal in them and they seem to be holding up fine.  That is my experience so far - some sites may school me though.

I'll be home tomorrow, just getting a touch of internet in a motel room in iowa at 1:00 AM in the morning on my way home from the small wind conference and the MREA fair in Wisconsin!  (fun/interesting trip)

[ghurd]

Tink,

You did not state if the noise was synchronous with the blades rotating or not.  If not then it could be the pivot for the tail bearing lacking some grease.

At one time I had a similar issue, it was noticeable only when it was low wind, and the direction changed - thus moving the tail and causing a squeaking.  If not the spindle/hub then I'd suspect either the yaw bearing or the tail pivot bearing.

Dan Lenox

"synchronous"

I believe most stuff scales fine, with appropriate exponents in the formulas.  LOL
My stuff is small.

I had some that would make a screech-screech-screech,  or  squeak-screech--squeak-screech--squeak-screech.
Mostly around cut-in RPM, which is pretty fast with something small.

These sounds were not a continuous screeeeeeeeeeech.

The problem was the blades were a bit out of balance resulting in a bit of high speed wagging. And no grease at all in the "yaw bearing"
The symptom was noise the wagging making metal grind in the yaw bearing (or my lack of one).

6 months working could need more grease.
Stator not rubbing.
"I hear this scrapping screeching sound but not always" makes me wonder if the sound is usually around cutin RPM.

I have wondered about the blade tracking causing a bit of 'wagging', because I think I have had it happen with mine.  And then the wagging could cause yaw bearing noise?
Might check the tracking.
G-

[Dave B]

Dan,

  Tight or loose bearing I guess is an opinion. I would call loose a bearing with "play" you could feel by twisting on the rotor. This to me is too loose and tight does not mean to me hard to turn but rather adjusted with no noticeable play. Just my opinion and as for the grease seal I understand that eliminating it as well as having a loose bearing will allow the machine to free wheel easier. Blades with lower torque in the lower RPM will not help this much either so there is a triple whammy for a smaller machine. Here in the Northeast I would not do without the grease seal, again just my opinion. My first machine was 12' and I did away with the grease seal, smoked it in less than 6 months, it was a rust red fried mess. Turning the rotor by hand with the grease seal on is only giving you maybe a foot of leverage, yes it can prompt you to take it out. Put the blades on and the wind does the rest. Yep, maybe balancing is an issue and I know we get anxious to get it flying after balancing but again just my own procedure is and will continue to be to balance the whole assembly without the seal and then tear it down and put it back in (indexing everything before pulling it back apart.) Just some ideas for others to consider before they might have issues. Every system and location is different.  Dave B.

oh dear... ;-)
I've been 'gone' for a good bit and this is pretty interesting.
Please send me another email about this (danb *at* otherpower.com)

I've had either no time or no internet connection for about 10 days here lately so I've not read all my email, or the board, and those I have have not got much response.

In short, can't say about the noise.

I could be wrong, but I do disagree with the comments about running with a tight bearing - I think it should be a bit loose.  If the bearing has failed though that will be interesting - I've seen that happen once so far.

To me, the stator really looks fine.

You may have mentioned the voltage of the system, I've not caught it though, I'd be curious to know.  32 amps sustained is about what I'd expect for a 24V machine and it should be fine there.  If it's a 48V turbine, that's too much power and it's furling late.  That *could* be a design issue or it could have something to do with the machine running a bit too fast I think, which I think could be caused by high battery voltage or too much resistance in the line.

DaveB..  I really could be wrong here, but I hate putting seals in 10' wind turbines, the friction is too much and it really hurts startup and output in low winds.  I've had lots of machines going for years now with no back seal in them and they seem to be holding up fine.  That is my experience so far - some sites may school me though.

I'll be home tomorrow, just getting a touch of internet in a motel room in iowa at 1:00 AM in the morning on my way home from the small wind conference and the MREA fair in Wisconsin!  (fun/interesting trip)

[luv2weld]

I'm inclined to think this screeching sound is the yaw bearing.
Let's go back to the beginning of this post.----- 40 foot tilt up tower. It's been up 6 months?
When you lay it down, all the friction points change.
So the first question to Tink is, When you brought the tower down, did you completely remove
the generator (alternator) head from the tower stub to check the surfaces of the stub?
I'm willing to bet that you do not have a brass or "puck board" insert on top of the stub inside the yaw.
I think you'll find that the noise only happens when the breeze changes direction and the head slowly turns
to follow it. Fast pivoting does not make any noise.

Needs more grease and a brass or HDPE (High-density polyethylene) washer.

Ralph

[Flux]

A few interesting points here.

I would have thought it was obvious whether the noise was related to blade rotation or to yaw movement but it is certainly worth looking at, things that are obvious to someone with experience may not be obvious to a newcomer.

I also agree with Chris that the black mark on the stator may be nothing more than tape, it's not really possible to know unless it shows a high resistance or you dig into it. I just can't see any justification for low melting point tapes and similar contaminating a class H winding, it probably does little harm but causes these confusing issues where you can't tell a burn from an innocent black mess.

Regarding seals and the lack of, I think it is ok without them in a dry climate, direct rain probably will get deflected by the magnet rotors but sustained damp weather usually contaminates the grease and starts rust corrosion and it becomes the end of the bearing.

I like to keep the seal but reduce the shaft size so the nip is about zero, at this point the drag is not an issue.

I have found on bench tests that taper roller bearings have more low speed loss than ball races but in the end they are better devices and this loss is not detectable under working conditions. On bench test this loss seems to be related to the clearance but for normal working i set them to not have detectable wobble at the outside of the magnet rotor, it may have a few mm at the end of the prop. This comes down to virtually no pre load and usually you can tighten the nut by hand if the thread is free or only need the slightest nip with a spanner. I don't think that working with a small pre load will actually cause the bearings any problem but it seems unnecessary. Running significantly loose will have the magnets hitting the stator.

Flux

[fabricator]

The first suspect for me would be the Chinese bearings, I know a couple guys who build trailers, they routinely change out the bearings before a trailer goes out the door, with real bearings with actual hardened races and rollers, before they started doing this they each had numerous returns with bearings completely gone, it seems that a significant number of these races and rollers never get hardened, or if they do see the oven it is not for long enough, the quality control over there is just a wee bit lacking sometimes.

[Beaufort]

 When you use black tape to hold the coils together and insulate coil interconnects the resin melts the stuff when it cures and coil heat will bubble it and make it look like you have a burnt spot in the stator when you really don't.  It's no big deal - the tape or whatever you use to hold the coils together is only there until you get it encased in the casting.  From that point on the stuff can disappear and it don't matter.

I just wanted to express my reservations at the application of electrical tape at this spot on the coils.  Using a non-permeable tape will likely result in voids between the tape and wires during casting (unless using vacuum, which I prefer).  These voids can't be good and even if the electrical tape turns to mush due to the heat, it's in a very very bad location with magnets passing over this spot.  It seems like this is the spot where you want a very good solid bond from the face of the stator, through the layers of cloth, and right into the turns of wire.  I've seen this sort of thing in lots of places on this board and I still can't understand why people don't at least use a permeable fabric tape.  Maybe it's no big deal, but I sure wouldn't do it this way.

End of rant...

[Ungrounded Lightning Rod]

Even if the magnets aren't rubbing the stator when you're working on the mill, they might be rubbing when it's in the wind.  There's a pretty hysterical load on those bearings and, even in the absence of bearing slop, things can get slightly displaced by it.  Be sure the stator is properly centered to allow for this.

IMHO the main issue with seal friction is if it keeps the mill from starting in winds above cutin.  (It's not going to eat an appreciable portion of your power or the darned thing would catch fire.  B-)  )   Since you have no cogging in the alternator with the coreless axial-flux design, the bearing and seal friction and any static blade imbalance are the ONLY things delaying startup from first-breeze wind levels.  So it seems unlikely that seal friction would be an issue - especially if it has the (necessary anyhow) bit of grease between it and the shaft when you install it.  Thus I'd go with the seal to protect the bearings from moisture and dust.

[ChrisOlson]

I just wanted to express my reservations at the application of electrical tape at this spot on the coils.  Using a non-permeable tape will likely result in voids between the tape and wires during casting (unless using vacuum, which I prefer)

I certainly won't defend the use of black tape on coil windings.  But I will say I've done it and had no apparent adverse effects on stator performance.  Ideally these coils should not even be potted inside of an insulating casting at all - they should be exposed to the open air.  I can't say I'm overly impressed with stators cast in resin of any type and one of my projects down the road is going to be to address this and design a different type of support for the coils that leaves the windings exposed for better cooling.
--
Chris

[defed]

...one of my projects down the road is going to be to address this and design a different type of support for the coils that leaves the windings exposed for better cooling.

i've thought a little about this too, but haven't quite stumbled upon a good way to do it.

[ChrisOlson]

i've thought a little about this too, but haven't quite stumbled upon a good way to do it.

Well, I'll throw out my theory that I'm going to try on my next stator to experiment and see if the rating of the generator really is improved by using open windings vs insulating them in resins.  If it works then I'll spend some time re-inventing the wheel.

What I'm going to try on my next one, which won't require building any different molds or tooling than I use now, is to wind the coils in normal fashion on a coil winder.  Then shellac them with motor rewinding shellac to hold them together nice.  When I cast the stator I'm going to cut pieces of aluminum foil tape and place it on both sides of the coil, covering the hole in the coil and the windings that are exposed to the mag rotors.  Then treat the AL tape with mold release agent.

I'm going to cast it with SmoothCast 310.  After casting I should be able to get thru the thin "skin" of casting material over the coils and peel the AL tape off and have coils held all around their perimeter by the casting material with the windings exposed on both sides and the hole open so air can get thru.  Doing this with fiberglass or polyester resin definitely wouldn't work because coil vibration would cause them to eventually come loose.  But SmoothCast will hold them and never let go.

I don't know if it's going to work or not, but it's something I'm going to try just to see if the exposed coils really do run cooler.
--
Chris

[Tink]

Thanks to everyone on their input on this.

DanB
It's a 24 volt with the round mags. It does produce AC as always with no decrease or increase noticed, it's the noise that has me worried. I'll be tearing it down completely in a few days to check that rear bearing. I'm in Northern AZ so it is real dry here. Do you think the tail vein should be smaller since it doesn't seam to furl the way it should? I understood that this turbine should be OK even at 1000watts but as I read about that stator in your parts section it is stated it shouldn't be run over 700 watts for very long. As it is even in high winds producing 32 amps it will furl but kind of jumpy and jerky motion and does cut down to 20 amps. Maby all is fine and I just have to get to the bottom of that noise. When I got the kit  I did notice the hub was slightly loose just a tiny bit. I ran it that way for months without a problem. Only after the few days of 60mph (off and on) winds did I notice the noise. The noise does seam to be synchronous with the turning of the blades and not the pivot motion of the tail or yaw bearing.

ghurd,
I hear the screech,squeak at higher speeds like around 15 to 20mph winds. It will turn even at 3mph easily and no noise till 15 to 20 mph. I have plenty of grease on all bearings.

DaveB,
I'll check the balance again since I have it down anywhy.

thanks again to everyone for all the input!

Tink