Well...........so my generator exploded

[solarengineer]

Dear list, <sigh>.... how can such a simple thing be such a beast?

my 9ft machine... the one using 1" by 1/4" neos 12 on each rotor using 2 rotors

and 70 turns 2 in hand of #20 and 9 coils is toast.

now i guess the low output is a mute point. these neodynium mags had about 68lbs of pull n40's why my output sucked so bad is strange but here is something stranger..

The beginning of the end: for starters and I remember flux mentioning this about fiberglass resin on magnet rotors....IT SUCKS and is dangerous! I now many people on this list have had no trouble and some have but the 4 times i have used it on steel it HAS seperated despite cleaning and scouring all to hell before the pour..

My mill started ejecting magnets like bullits in todays very turbulant winds..23km/hr

then the stator grenaded from the bullit neos then a hunk of the stator jamed and pow...end of story.

BUT when i picked up the neos off the grass i said gee jamie dont carry all these in your hands cause they are so strong...well i was already irritated that my baby just shook itself to death so i threw them all in one hand.......and low and behold they basically had ZERO magnetic attraction!!!!!!!!!!!!!!!!!

How now have i managed to make a device for demagnatizing n40 neodynium magnets? all i wanted was a genny!! but how is this possibly? GEEZ!

Now what should i do... what could have possibly demagnetised these magnets while up on my mill?

not even the satisfaction of a fried stator so i could say...well at least there was some real power here... but instead my magnets demagnatise.... THATS CRAZY

OR IS IT?

perhaps something caused the neos to demagnatize, they loosened their grip on the rotor and the centifical force turned them into bullits.

please help me on this to understand what happened.... should i stay away from 2 in hand and go single windings with a few more turns for our crappy wind? what happened to the neos and their strength.. no one has ever reported that problem before.

Thanks everyone!!

Persistent Jamie

)

[zubbly]

hi solarengineer,

sorry to here of the loss of the genny and the magnets giving up their life.

i had one motor conversion throw a mag once (that damn fibre glass resin). thats why i turned to making aluminum cages with locktited in mags. or using a thin wall cage and pouring in actual epoxy. i came to the conclusion a long time agao that fibre glass resin is not worth a s--t. period.

i am not taking any chances on the current 7.5hp project. will soon be ordering 2x1x1/2 mags with 2 holes pre-drilled and countersunk that i will be screwing down with stainless screws. i don't really care if there is a small loss in strength because of the holes. in my opinion, they would also be good for the dual rotor design. you could also have a 1/4 inch thick cage cut out of aluminum to hold the mags in place. even 1/4 inch plywood be be better tha just resin holding the mags on.  seal up the plywood good with sealer and use some stainless screws to hold it onto the rotor plates

as far as the loss of magnetizm in your mags, it is puzzling.  i have not followed your progress on the unit to get an idea of what had happened.

good luck with the repair!

zubbly

[harrie]

Hi Jamie. sure sorry you had the trouble, It sounds like it must have got very hot to demagnitise the N40s, If you rebuild, you may consider following my posts on the 18 foot 16 inch duel rotor, it puts out amps almost all the time, even in very low winds. The best thing is that it only turns 40 RPM and is always in stall so it will never tear things up. Yes, it is low amps, from 2 to 7, but it is continuous. I have found that my 12 volt bank, is always full, and the dump load is almost always steady. You also would not need a furl system, but would recommend a short out switch to shut it down in very high wind. I have saw 30 mile gusts, and it still stays in stall putting out a max of 7 amps. I also have now tryed it in 48 volts, and have saw 70 amps,3360 watts in a 20 mile wind. at around 140 RPM. I perfer to leave it at 12 volts, and be satisfied with few but steady amps, and not have to worry about tearing things up.

Great fun, Harrie

[willib]

sigh , sorry to hear of your wind turbine's untimely demise.

i agree with harrie it musta got awefully hot.

[hiker]

i belive i read some where --if your mags are under a big load -and suddenly stopped while still under load..you could lose some of your magnatizem..sounds like you had some of your coils miss wired[shorted or what ever]...

[hiker]

if you scracth the glue side of those nickle plated mags they will hold better..

plus i wrap about 5 winds of nylon tape around the ouside of the rotors..[wrap real tight]

i just use super glue and some epoxy around the outer edeges[plus nylon tape]

and i use some heavy ceramic mags--only lost all the mags once due to some bad vibs..[at a high rpm]

well good luck on your next one--check your wireing.........

[Don Cackleberrycreations]

Some thing I havent seen meationed concerning fiberglassing the mags on the disc.

Doesnt anyone drill between where the magnets are mounted and counter sink the back side of the hole. Steel and fiberglass expand and contract at different rates  Which means the fiberglass will loosen . By drilling and countersinking the back side you are basicly creating a fiberglass rivet. Also the addition of glass mat will greatly improve the strength . Resin with no glass is quite fragile and has very little strength. Lets be honest here the more glass the stronger .

   Though this could bring up a possiblity of even layering steel screen or steel laminets onto the disc.

[terry5732]

Simple shock can demagnetise. I would imagine they had several good knocks before they ejected. I've ruined several magnets simply by dropping them on concrete from chest height.

They are still of a good composition to remagnetise. To get a really good charge is a little complex but you should be able to easily get them to about an N30 grade with a solenoid and car battery.

[richhagen]

sorry to hear about the mill.  My vote would be for some form of heat as the major cause of the demagnitization.  The only thing that bugs me with that is that none of your #20 magnet wire coils showed scorching, and you state you never got many amps? It would strike me that the material could be re-magnetized, although I'm not certain of the mechanics involved.  A quarter crusher comes to mind, but I bet you would need a weaker, more sustained magnetic field in reality.  Rich  

[Shadow]

This is just a theory, so dont jump all over me. I often hear people say how hot thier resin can get when curing ,if to much hardner is used. Could it have been possible the magnets were subjected to too much heat during the resin stage? Thus the poor output from the beginning? Just wondering out loud here...

[Flux]

Sorry to hear of your troubles.

Polyester resin is not an effective glue. Alone it is not very strong as a casting material but is usually strong enough, but some glass strands incorporated in it will make it much stronger.

Others have mentioned keying the complete casting to the discs and that is a good idea even if the magnets are glued on with something strong. I prefer to drill a few holes between the magnets and tap them and fit screws long enough to stick up, then they embed in the resin and prevent the mass moving and there is less chance of water penetrating between the steel and casting.

Why did it fail, my suspicion is that you have a very large prop on a shaft too small to take the serious gyroscopic load during yaw and the magnets hit the stator.

Three things can demagnetise magnets, excess reverse magnetising field (which you would not have had), heat and vibration.

You may have had significant heat from rubbing during the disaster and there would inevitably have been serious vibration especially on impact after flying. My guess would be heat above 100deg C.

Flux

[tecker]

210  turns per phase  is too much resistance the heat got you . The other possibility is a bad connection internal . With output down you'd have to suspect a short . I don't think any of these plastics will adhere to the steel you have to encapsulate the magnets with the resin going over the edge of the plate and a layer of gauze there to bond to. Still heat played a major role in the overall failure . If you look at the glue display in a store there's a unique category of adhesives that work with metal

and that's iffy at best . Balance and true running rotors are important if you take a hammer to a rotor or a stator it won't take long to have them in pieces . You also have some demanding conditions to worry about. You went out side of the book in

 construction in you coils and this gave you some problems . Scale the unit to 12 or 24 volts and try agin. Not what you wanted to here i'M SHURE BUT  that's what you want from your friends a boot to get back in there.

[TomW]

Flux;

Here in the Midwest of the U.S. we can see a lot of intense lightning with enough energy to explode large oak trees.

I wonder if a "just right" lightning strike could demagnetize a rotor full of NEOs? Never saw or heard it proposed so thought I would toss it out there. I have seen the aftermath of lightning strikes on communications gear, melted conductors, exploded objects, retinal afterimage for days from viewing a hit in person just to name a few observed effects. So what do you think, is it possible even if unlikely? A similar dissipation of energy could play hell with any mechanical bonds, also from either steam from water vapor, mechanical shock or fast heating of one part and not another.

Just had to ask because it came into my head.

Thanks;

TomW

[Flux]

Yes Tom I am sure it could happen. If the discharge is oscillatory it will demagnetise. If not it could magnetise and you may have poles all over the place and not where they should be.

I have not heard of a case but wouldn't consider it unlikely, it destroys just about anything under the worst conditions.

Flux

[Nando]

FLUX:

I think that this is a case of high temperature that started the whole destruction -- allowing the "glue" to soften at the critical moment of the demagnetizing point and the post high RPM forcing the magnets to fly away.

An analysis of the charging current, the battery voltage, the generator internal resistance and the cabling between gen and load to define how much power was delivered versus generated at the moment of "fly by" effects.

Nando

[Nando]

Jamie:

Sorry for your loss.

Can you detail the charging currents at the time of your bad experience ?.

Bank voltage, charge current, charge controller, generator winding resistance, cabling (gen to load) resistance, cut-in RPM and Voltage .

And most important wind velocity around your time.

I do think that your problem is a temperature problem that caused demagnetization and fly apart of the wind mill.

Nando

[rottingspinalcord]

when magnets hit something hard they get demagnitized. mabye tjhey hit the ground hard i mean uu said they cxame out like bullets

[Flux]

Nando

I had been discussing issues with him regarding low output. There is no way that this could have been caused by heat from the windings, his magnets are half the thickness originally intended and he will not have seen 100W at the disintegrating speed.

I suspect you may be right in that the heat was caused by a rub between magnets and stator, this is a tiny alternator for such blades and I have no idea of the shaft or bearings. Heat would quickly reduce the strength of the resin if only used as a glue.

I think the magnets may just have been stuck on with polyester and not cast into a block of resin.

Flux

[Nando]

Jamie:

Do not throw the weakened magnets, you could try a re-magnetization not ncessarily to maximum ut somewhat close.

If interested let me know

Nando

[DanB]

The magnets rubbing the stator in Scotty's little diesel overheated the magnets, same thing happened.  I agree - I expect that's the cause.

[solarengineer]

hey flux, the magnets were immersed in resin. the shaft was 3/4"

somehow or another the threaded rod broke and the stator inside has carbon scoring. so heat was the demagnetizing and the pin in the grenade.

i have it all apart and one of the stator mounts broke at the weld.

so ok, learned lots and everyone offered so much in the way of suggestions...

so away i go and will now finish my 2"x1"x.5" magnet rotors. its a copy of tims turbine.

but i used a few more turns than his 34 2 in hand #14... hopefully that will help cut in a bit

Thanks

[solarengineer]

thanks everyone... it was heat... stator mount broke and carbon scoring everywhere.

i will rebuild!!!

thanks again!!

[Flux]

At least it is good to know why it failed. Gyroscopics on those large blades would flex a 3/4 shaft considerably during a yaw at high speed. Once the rotor contacted the stator the stator mounts would have suffered and then it would be a chain reaction of destruction with things jamming in the air gap like a disc brake until the resin disintegrated and let the magnets out.

Good luck with the new machine, that should be fine with a decent hub and bearings to take the 10 ft prop. A few turns extra on the coils will do no harm and will let you run with a wider gap and a bit more safety.

Flux

[DanB]

Yes, I forgot we wound his w/34 windings.  I usually use 37 in 12V machines now.

[solarengineer]

again thanks everyone.. awesome learning experience! i have now just found another way not to do something lol

ruggedness is the key

jamie

[dinges]

What is 'fiber glass resin' that's not worth a dime?

Epoxy or Polyester? In another thread I understood that epoxy was excellent for glueing magnets to the steel rotor.

Peter.

[solarengineer]

polyester is what i used. it does not adhere well to metal. it does long enough to make you think its solid till your machine is under load then lets go.. doesnt take much force. im using epoxy next

[wdyasq]

Peter

Many here do not realize there is a difference. Few here realize "Fiberglass Resin" normally sold in the US is only a ployester compound with little integrity. Many here will spend $300 for magnets and wire and comprimise on a few dollars more on proper resin, glass fiber and the time on research to understand which resin to use.

Basically Peter, they go from being ignorant to just plain stupid. I doubt there is a cure for this attitude. I have been watching this board for years and the fools just rotate through spreading misinformation and misguidance. The funny thing is they aren't smart enough to realize they are ignorant. And, stupid enough to fail to realize they could get someone killed or seriously injured with the bad advice. When that is added to the arrogance of political correctness ....... well, folks like me change their signature line because they are tired of seeing the manure squeeze from what they call thought...

Ron

[zubbly]

ron!

i do my best thinking whike sitting on the throne every morning. is that what you were refering to ?  

zubbly

[Reno]

I could be off but I think this stuff should be given some consideration.

It is specifically designed for metal to metal adhesion. As some have said if you are going to spend hundreds don't try and save a buck on the glue.

I also question the nickel coating as it seems it does not take much to get it to delaminate from the magnet which in turn would mean your glue is only holding the coatings and it it tears goodbye magnet.

Here it is

http://www.fieldlines.com/comments/2006/6/5/124310/3740/13#13

[iFred]

Personally, I use PL200 construction adhesive. Never had a problem even though the eniter genny blew apart peice by peice the magnets never came off the rotors. I don't beleive in fiber glassing the entire rotor , in my oppinion it does noting unless you have something like fiber or stainless steel wire going around the outside edges. The construction adhesive is the best, and I leave a bit around the outsie edges of the magnet for more support. as for why the magnets would de-magnitize. If they hit something on the way out then they might become demagnatized, best guess.

[Experimental]

   Hi Jamie, and sorry to hear about your misfortune !!

   One thing I noted in the comments here -- no one mentioned that there are many different types of resin and some varieties, don,t adhere to metal..

Most automotive resins, contain Isothalic resin and are formulated to stick to metal while "boat types" are not -- they are usually bonding type resins -- there is a big difference !!!

   As to the demagnitization -- haven,t got a clue !!!??

   When you rebuild, I would suggest you use one thin layer of cloth over the mags, as Hugh Piggott has in the past -- I also sand blast the steel backing plates, but rough sanding will help -- most of all, be sure it is metal bonding resin !!

   Wishing you, better luck in the future,  Bill H.......