The Rotor

[Murlin]

But I like it

.5" rotor without fasteners....44.29 lbs

.625" "                          56.15 lbs

Murlin teh hrmmmmmm......  

[Murlin]

Hvent got a clue if the screws will mess up things or not....I am sure someone will tell me before I actually get started.

They probably will.... most of my ideas have been a total wash in regards to these electrical gizmos.

But its just a concept.

Like Flux says, there is probably nothing that someone hasnt tried already.

Murlin

[zapmk]

Murlin,

Cool looking way to retain the mags, And I really like the 30 degree slots to aid in cooling and doesn't look like it would weaking the rotor to much.

44 lbs for the .5 rotors looks like it would be in the 24 inch range.

Would you really need the phenolic spacers, wouldn't a good epoxy resin accomplish the same thing as the spacers ?

 -Zapmk

[Devo]

I like that set up , if you put the spacers in first it would make magnet placment a breeze , you might not even need any epoxy to hold the mags in place. You would want to make sure the spacer material didn't cause eddy currents.

Looks good

Devo

[jimjjnn]

Phenolic Spacers. No eddy current as it is like plastic

[willib]

eddy currents are induced in  a  stationary metal , in a moving magnetic field

 

[Murlin]

Oh sorry the rotors are 22".

"Would you really need the phenolic spacers, wouldn't a good epoxy resin accomplish the same thing as the spacers" ?

Yes, in my opinion you would.  Under normal circumstances it would be just fine.

But if there ever was a runaway for any reason, I would feel better if they were tied down.

What happens when the thing is running away for what ever reason and you needed to get close to the tower to physiclly brake it?

IMO, the centrifical force of the magnet mass would exceed the sheer properties of the epoxy. Seeing how the stator could be red hot, the rotors have grown .060 and sheered off the epoxy on some point on the stator and looseened at least 3 magnets.... Ruh Row... the rotors are smoking when I get it shut down.

I do not want artilery firing at me when this happens.

Probability of it happening in it's lifetime?

I would say 85%......

The screws are a small price to pay for someones life.

Course I might have to add you would not want to use grade 8.

Use a softer grade that will stretch around....

This is totally theory though, at this point and could go quite moot when the experts reply to it....

Murlin

U

[Flux]

That method of mounting magnets looks good. Sorry I can't read the second sketch even when enlarged.

My biggest fear of approaching the thing during runaway wouldn't be flying magnets but flying lumps of tree ( blades)

What method do you have to shut it down ?  If the thing is far enough from habitation not to hurt anything it's not so bad. Otherwise a foolproof way of shutting it down is a good idea, I prefer to be able to get the tail at right angles to put the rotor at right angles to the wind. Any form of brake needs to be extremely well designed to work effectively without seizing up or burning out in the moment of crisis.

I think your concept of failure is a bit extreme but it is worth thinking about.

Normally the alternator load will hold things in check and if you did burn out a stator the most likely effect would be to develop shorted turns and this would produce enough brake torque to stall the blades. A complete short ought to stop it like a brake switch.

Heat from a burnt stator would be unlikely to heat the magnet rotors to the point of causing a worry. If the magnets did get above 120 deg they would demagnetise and remove the source of heat.

By the worst danger is open circuit and overspeed with no heat produced.

If for some reason you had a serious rub between rotors and stator then whatever precautions you have made will most likely not prevent it grinding to a halt or mincing everything up and over speeding.

Flux

[Murlin]

I resized, Are these too big?

Trying to play by the rules and help the dialup users out

Well for braking....

Make it furl. Just like you are doing now....that system looks pretty good.  

Short it out with an electric brake unit, using tose whatcha-ma-kallits in ther to make it "soft stop" .

Finally, a reduntant mechanical backup.  

One method would just brake on the back of a 4340 plate affixed to the back rotor with 4 heavy duty disc pads pushing with a metal rod setup running right up thru the center of the yaw axis.

This would not add too much length to the lever and not make the tower stresses much more than they are now.

Another method would be to machine a custom spindle hub out of 4340, and affix another 4340 rotor disk to the back of the hub.  You could use 2 heavy duty truck disc brake calipers and mechaniclly brake through the same center hole.

Another way would be to use an electric brakes and run that system off a slip ring.

I was thinking sliprings anyway since wind here in my area changes every few minutes due to the flat terrain...

The last 2 add about 4" to the "lever" and add considerable more stress to the tower and frame of the unit.

Got my Hugh Piggot Workshop book today.....

Woot!!!!!

Nope, no way, no how, am I getting up there on the tower like he did.....It's not happening.....

Murlin

[zapmk]

Murlin,

I was close on the rotor size, the pins on the ends should keep them from flying off the ends of the rotors, Iam sure you are planning to stick the mags to the rotors with something?

With 22 inch rotors your not going to spinning them at a very high RPM are you, 250/ 300 tops ?

If your worried about Heat letting lose the epoxy there is something that might be of interest, http://www.smoothon.com/PDF/Formula%2079-206%20FR%20-%20TB.pdf

Haven't tried it myself but I'am thinking about.

Not knocking you Ideas, I think they every good ones, and Yes I think everybody worries about safety with these things.

I don't know what you mag size is going to be, But I can tell you that with rotors this size that I did have a problem from the magentic pull, Just take a look at my files, Sure wish a waterjet could have cut slots like yours

 -Zapmk

[Murlin]

Should be a low RPM machine.  But Flux has some interesting figures on improving output with 6 in hand and it would be a faster machine with those coils..

There are other reasons besides safty for securing the mags in such a way.  That's just one of the scariest reasons I could think of.  Some people say that when the mags start doing their job that they will get weaker over time. Will they? Search me....never hurts to have a backup plan.

If it should run away, some of the magnets could fly off and cause considerable damage to someones property and you could get sued.  

I plan on glassing the props. So hopefully they should hold together @ mach 10

There even has to be a reason that I haven't thought of yet for the magnets to break their bond with the epoxy.  Oxidation for one.  Water getting in between the epoxy and the rotor.  It wouldn't show up for a few years, but eventually it would rear its ugly head....

 I can proly grind the angles on the mags themselves in a couple of hours and even do it ahead of time.  Replacing them would be done in a few hours.  I would much rather have the manufacturer do it.

Can anyone be 100% sure they wouldn't come off and hit something?  

I can't say for sure, but securing them with fasteners is as close as you can get to preventing that IMO.  Sure its alot more work but I have nothing but time  Hopefully I can stop the stator from ever rubbing too bad...

Oh BTW, the water jet is not cutting the cooling fins in my rotors.

I must sine my rotary table up and index them one at a time so the CNC can cut them since I dont have a 5-axis mill.  Going to be fun, fun.....I will show pics of the whole thing as long as Dan doesn't care if I dump them on his server.  I will try to keep them small.

You guys deserve a big hand for coming up with such an ingenious method of renewable energy.

I might have to get a site up and going if it causes any problems.  But I would rather keep it here and hopefully be able to make a positive contribution to the Forum.

Murlin

[zapmk]

Murlin,

I think the electric brake unit would work real well, anything with a return spring to pull the pad away from the drum or rotor. I've tried the disc brake caliper setup and they drag a little.

 -Zapmk

[Murlin]

Drag!!!  Excellent consideration, hadn't thought of that.   Yes, something with a return spring or some mechanical weighted design that would definitely keep the pads away from the disc/drum.

What ever brake set up is used, has to be foolproof and not get all rusty over time, or leak out any fluids, or crack any hoses ect....

I haven't got that far yet.  Just got the magnets, spindle/hub and the rotors should be cut out this week...

Going to be fun, fun....I love this stuff....

Murlin  teh terrible speller, but trying hard to use the spell checker...

[Murlin]

Updated photos...

[Murlin]

Well, I am considering changing the design on clamping the mags down.

I will be making a small form die to bend and punch holes in SS keepers.

Since the clamps will run across the face of the magnets, if the rotors rub the stator on violent yawing , the magnets will not even drag, the shim stock will do all the bearing....it is highly unlikely that enough rubbing would take place to cut through the SS shims.  I think the stator would short out first....

I will redesign the pictures and if any of you guys see a problem with retaining the mags in the new way, let me know.

I would not even have to grind on the magnets at all, which is a very good thing

Just need to get some 0-1 and make a form/punch die....I think I might know a guy with a press that will run the parts for me....

Murlin

[Murlin]

Well now I am having second thoughts....015 shimstock would probably be strong enough to hold down the mags but if there was any pulling and flexing around on it it could fracture over time....and it would take up about .02 per side of the air gap.

I was planning on perhaps using a tighter air gap because of the precision of the alternator, so now I am back to my origonal phenolic clamps.

I will keep this idea on the back burner though, and perhaps experiment with the prospects at a later date.

I want this first one to work....

Murlin