new user (with an idea ?)

[dinges]

G'day everyone,

This is my first message on this board, but have been reading/following it for a while. Stumbled across it after visiting (many times) Dan & Dan's website on windgenerator building (otherpower.com).

At the moment, I'm building one myself; it will have about 1m. rotordiameter, 12 magnets (dual rotor), 9 coils (75 wdg/coil), 3phase, 12V. The coils have been made, stator is finished (apart from casting). At the moment, the rotor-plates are being 'lased' at a local company (price was good too, a cake for the employees :-) ).

Anyhow, I've been thinking (I wonder if that explains the headache): for a dual rotor generator, you need to have (in my case) 24 magnets for, say, 100W of output. But wouldn't it make much better use of the magnets to construct one with 3 rotor-plates (36 magnets) and 2 stator-coilsets? (i.e. rotor-coils-rotor-coils-rotor; with the inner rotor-magnets mounted on epoxy or something else that is permeable to the magnetic field). In this case, you would double output, with only a 50% increase in magnets.

You'd ofcourse need to increase prop-size, but you'd end up with a relatively small (qua diameter) generator, only a little deeper (and a bit harder to construct, but not much).

Anyone thought of this too? And if so, why isn't everybody building generators like this? Am I overlooking something here?

Peter Dingemans,

The Netherlands.

BTW, my hands are now a little recovering from playing with the magnets; in my 10+ years of experience as a tinkerer, I've never needed a box of band-aids at my desk, but since I've had those magnets (from supermagnete.de), the 3/4"1/2 1/4" ones, I have a box on my desk :-(  I'm actually getting afraid of them, and shiver at the thought of those real beasts (2"1" 1/2"). If something happens, I may have to take off my shoes to be able to count to 10....

[nothing to lose]

"I'm actually getting afraid of them, and shiver at the thought of those real beasts (2"1" 1/2"). If something happens, I may have to take off my shoes to be able to count to 10...."

They are a bit more than what we played with as toys when we were kids aren't they

I think many of us have thought about the idea of several stators and rotors on one gennie, don't remember off hand why it's pretty much decided to not be such a good idea though.

My thought's are for one long gennie with one large set of blades. Basically 3-6 daul rotor gennies (depending how you look at it) running off one shaft powered by that large blade set.

 It would seem the pos mag on the first rotor would send flux to the neg on the second rotor which sends it to the pos of the third and so forth untill it hits the end of the line, then flows through the steel disk and returns the same way magnet to magnet untill it reaches it's starting point then the cycle basically starts over again, though it never really ended.

 This is not thought to be a good idea as I recall though.

Now something else I am thinking about is two dual rotor gennies on the same shaft but as seperate units. Basically take a front wheel drive car rotor through axle setup and mount the first dual rotor gennie in the fron on the hub as normal. The CV joint and axle shaft runs a straight line back to the second dual rotor gennie. You now have 2 gennies power by one blade on one tower etc...

To carry that one step further, mount a set of blades on the rear gennie also. Facing forward. The wind hit's the first set of blades, then hits the second set of blades. Both set's of course need to be mounted to face the wind and rotate the same direction.

 My problem with that idea so far is how to make it furl to prevent problems in high winds. I am thinking to mount the tail ABOVE the gennie like a rudder on a plane. It could work in a couple ways. 1 to trun the gennie partly out of the wind as normal, and 2 it could swing a little to the side to slow the wind flow also slowing the blades.

 Beware of creating turbulance that could rattle the blades though.

[PCHedglin]

http://www.otherpower.com/images/scimages/973/00970283.pdf

This is where I found an Excellent engineering article someone had

posted quite some time back.  It gives quite a bit of detail on the

construction and design of a AFIR (Axial Flux Internal Rotor) machine.

Be careful with those magnets around your computer.  They can really

mess up the monitor, let alone the computer itself!

Patrick

[PCHedglin]

http://www.mipsis.com/mds/publications.html

I found the engineers' website.  Wow!  There is ALOT of information here!

Patrick

[electrondady1]

well, i built a two stator three mag disk unit  last month and it worked . i cast the center rotor in acrilic / resin .  it saved me the weight of two ten inch steel  disks ( about 11 lbs.). there are 16 poles one each disk and 12 coils per stator  i ran them three phase in a series 8 coils per phase . this is only my second geni ive built and the first since i got on line and discovered this forum . in principal the system works.my building techniques are were the weakness is  . almost a lesson on how not to build a generator. but i am in the process of rebuilding it .  

[electrondady1]

down loaded your link, thanks, in a way that is how i got started. with one central rotor and two stators to utilize both sides of the mags.

[electrondady1]

just one more thing , some of the most experienced builders like danb and hugh piggot have stated stacking rotors and stators is less powerful than the same no. of coils/mags rotating on a single larger dia. it has to do with the linear velosity  of the mags at a given rpm.

[rotornuts]

I've definitely wanted to do this. I'm not hunting for "efficiency" so to speak but I have a plan in my head for a three blade machine where the inner third of the rotor area is as "open" as possible. It's an attempt to reduce the downstream turbulence and the upstrem "cone" to allow the blade area to do most of the slowing of the wind. I guess my theory is to allow unrestricted air into the center of the rotor area to help "pull" air through the rest. So, I needed an idea for a small diameter alt and multiple disks seemed appropriate.

Nuts

[nothing to lose]

 I thought of using more than one set of blades. Each set about 90 off the front set. Sort of a turbine effect, each set catching the wind that got past the set/s in front of it. Sort of several gennies blades and all on one center axle. Maybe 3 gennies deep, more if that works.

I think I am in for problems with that idea though, but will probably try it. The way I plan to build it I could always take it apart and have 3 seperate gennies anyway, just need new axle shafts for them is all.

Not sure which I will build first, got to finish other things before I start another project or I'll just die!!

[ghurd]

NTL,

There was a story about the same thing a while back. I can't find it now.

Seems like some guy famous for twisting the truth had a single shaft, multi blade genny.

It was big. Maybe a 20' or 30' shaft? Maybe 5 or 7 sets of blades? I don't know, but big.

He claimed to get more power than was available in the blade dia., but he only counted 1 of the blades because all were the same size in a single row.

Had some interesting pic's and good comments.

I am thinking along the same line for a tiny motor conversion.  It has a shaft out both ends.  Why not add another blade way back instead of a tail? (why not is in the story I can't find)

Sort of a upwind AND downwind machine in one.

The tail blade could be lower than the front blade, chain drive to the genny, so it uses different wind.

I just can never find the right adaptor to get anything I have connected to anything else!

G-

[dinges]

Thanks for the replies, everyone.

I'm curious; someone said that DanB & Hugh P. had mentioned it (lower linear velocity-> less power) somewhere; I think I've read all their webpages, but haven't found any remarks on this issue. Maybe it's in Hugh's leaflets? I don't have these, and I wonder if I should: it seems that most of the info is on the web? Only 'difficult' thing is the furling-system, haven't figured that one out yet; maybe there Hugh's leaflets will be of help.

2 turbines on one axis, hadn't thought of that one, but can't think of a reason it shouldn't work. Note, however, that in other such 'appliances' (turbo-fan, pumps, etc.) they also have stationary 'blades' in between to guide the fluid medium.

Your first prop would of generate most of the power (i.e., slow down the wind), 2nd turbine would see slower wind, i.e. less power available, but I can't think of a reason why it wouldn't work (now, that doesn't mean much!)

However, the nagging doubt in my mind (both dual props and dual rotors (magnet assembles & coils, i.e. rotor-coil-rotor-coil-rotor) is that it isn't used in professional windgenerators, AFAIK. These guys are the pros and should know which works/doesn't work.

BTW, the same doubts I have about downwind-generators; they seem to have advantages to me (mechanically easier), but, then, why don't I see more of them out in the field?

Then again, much innovation often can be found more in enthusiastic individuals than small/large corporations....

Grtz,

Peter.

[ghurd]

Two turbines, 1 axis.

From memory. So don't put this in a book!

The first blade slows the wind, so much slower wind to the 2nd blade.

Balancing both the blades speed to run the same only works at 1 speed().

So 1 blade is alway a drag on the other.

And the first blade slows the wind, and the second blade slows the wind more.

There is too much air 'building up' behind the first blade for it to work well,

and the air behind the first blade is slowed so much the 2nd blade can't work well.

Down wind.

Just me maybe, but all the weight way out there causes more work (labor) in the yawl bearing. And I have not seen a simple way to furl one.

G-

[dinges]

Ghurd,

I'd thought of the drag issue too.

But, for downwind generators, a furling system should be very easy: gravity holding it down (vertical), but when windspeed increases (i.e. axial force on the turbine), it starts to rotate upwards (agains gravity, maybe with the help of an extra spring?). When furled, it'd look like the main rotor of a helicopter? Seems much easier to me that the usual furling system on 'upwind' generators.

BTW, another thought I've had on furling: how about winding an extra coil-set in the generator, of only 1 winding/coil (for, say 9 coils as in my 3phase generator) of heavy duty wire. Then when you'd need to slow the turbine down, you could simply short this heavy duty coil. This wouldn't stress the 'normal' coils, and it would be easier to get rid of the energy (the 'dump load' coil wouldn't be embedded in epoxy).

Of course, you'd still have to get rid of all those watts that are generated by the wind, but cooling of the coils should be less of an issue.

Only downside I can come up with: it'll probably increase the thickness of the stator, thus decreasing magnetic field & generated power.

Comments, anyone?

Peter.

[ghurd]

Creepy.

Really creepy.

That multiblade one shaft thing just turned up.

Seems someone wondered how they got the published 'numbers'.

Anyway, stole the link from the other post. Here it is. Or some like it.

http://www.speakerfactory.net/TURBINES/INNOVATIONS/4ROT-4FOOT-1GEN/PAGES/4ROT-4FOOT-1GEN.html

G-

[Matrix1000]

Yah this multi blade design is in my opinion the best design ever.

In this design the turbine is angled 10 or 15 degrees so about 1/4 to 1/2 of the wind hitting the blades havent' been touched by the blades in front of it.

[ghurd]

There was serious discusion about it a while ago by many people who know much more than me.

There a lot of problems, oversights, and misconceptions in the design.

Throw in apparently repeated accidental miscalculations by certain parties.

The searches I did came up empty, but it is here somewhere.

I only concidered it because I can get 250% of the rotor dia between the first blades and the tail blades, with almost '0' work and '0' money.

And I am using little tiny free blades.

And I really don't care much if it works, but works is always better than not.

"Nobody beats the law. Betz Law!"   Was that John Wayne?  

G-