I am building a Magneto, need help with the coils...

[twilightinsanity]

   I have built a contraption that turns at about 50 Rpm's and can lift 35 or so Lbs (lift measurement was done with a cord tied to a weight and then tied to the rotating 1 inch shaft that sticks out of the side of my contraption)
   I know I'm gonna get flak for calling it a contraption, but I like the word a lot!
   Basically, my contraption is a waterwheel (for the sake of discussion...)

   I want to use it to generate eletricity. I think my best option is to buy some magnets and wire and make my own magneto generator. I know this is a very tedious job, but I have the time and patience (frankly I can't stop thinking about it and if I dont build it I will go crazy!) and magnetos are pretty simple.

   (Tangent - I just joined and my computer is making sounds like a kookoo clock... is this normal? It's entertaining, but not every hour... end tangent...)

   I am having trouble determining what kind of coils to make. Should they be cored? If I use the new idea of river magnetite instead of iron core will it help at all? (that is supposed to remove almost all back EMF)  How much resistance will a staggered magneto make once it has reached speed? How much current can I get if I set the whole thing up to make 60Hz AC 110 ? I can do this with the right number of magnets and the right Rpm's, but it's useless if I can't make any real amps...

   That's where I'm at... any advice would be great, I need a little direction here...

  Oh yeah, and It's nice to meet you all! Open minds are a rare thing apparently, it's good to see a place where they can meet, and grow ideas...

[fleebell]

http://tech.groups.yahoo.com/group/awea-wind-home/

check out those guys, There is a complete set of plans on how to build an axial alternator.  You are going to have to gear up as 50 rpm is about 1/10 of the speed you will need for the average one. It's also a simple design , a 10 year old kid could build one following the directions given.

An alternative to that would be one of these types. These are also very simple to build.  You would have to build a big one to get  more than just a couple of amps  but your wheel could turn a really big one easily.  This type doesn't have anywhere drag as a standard alt does.  Lenz forces don't really have much effect due to the way it works

http://www.leebell.net/workshop/bobble.htm

The problem with big water wheels is they really don't put out much force as most people think so don't expect a whole lot of power from the one you have. From your description you only have about 250 watts worth of power or about .3 hp to work with. Don't expect to get more than about 100 watts max after friction losses.(gearing, efficiency of alt etc.....)  They work much better doing physical work than turning a generator.

[twilightinsanity]

Yes, youre right, I calculated .46 Hp and a lifting force on a 1' axel of about 45+ Lbs using a thin cord. Thats probably not truly accurate in either case, but it's close enough, I'd say +/- 10% at most.

   OK, since voltage can be controlled with transformers, and phase can be controlled in at least one or two ways, (any ideas on making high freq. AC into lower freq.?) and more magnets and coils on a larger diameter wheel (I can do like a 14 foot wheel if I need to) means more current...

   I really need to know what kind of resistance to turning I'm gonna get from a Magneto! If I have a larger wheel, and more magnets and coils, they would pass each other faster due to the whole radial thing, then I would get more out right? But only to the point my wheel stops turning, which is at about 50 Lbs. at 35 or 40 Lbs however, it spins just right, at 45+ rpm's.

   I can make up to about 300 Lbs of torque, but I will never get above about 60-70 Rpm's even without a load. I can build a UFO sized magneto in my backyard if I need to. (The neighbors will think I'm completely nuts, but They probably do already, so why not, I say! Heh...

   Is there a formula somewhere that describes how to calculate amps and volts with the number of windings in a coil and the speed of a magnet passing them or something like that?

I heard this saying once "Horsepower ruins tires, and Torque wins races" I dunno if it's true, but if it is maybe there is a way to convert torque into electricity - which is my real goal I guess. Any suggestions?

[fleebell]

   Is there a formula somewhere that describes how to calculate amps and volts with the number of windings in a coil and the speed of a magnet passing them or something like that?

I've been looking for one for a while for something like that, If you find please let me know!

  It would be a lot simpler and much more convenient to run the output from the alternator to a charge controller to charge a battery and then use a inverter to get your  power back out of it. That way you don't have to worry about trying to control the speed of the wheel exactly and batteries are perfectly happy with the power once the wild ac from the alt is converted to dc..  The pulsing waveforms work just fine for charging.  I personally think they work better but thats just my opinion.  You can also use the power when you want that way and not just when the wheel is running.

  There is really not a lot of point in making a really big diameter axial type alt unless you just happen to like winding coils.  Unless you use many small coils and magnets your output wave forms are going to be just single pulses anyway.   It would cost much more to build than just using a "standard" windcharger type axial alt. One 4/1 and one 3/1 pully sets  to speed it up with your 50 rpm input that would give you  600 rpm and that would be plenty! 

This link below has a bunch of different examples and most tell you enough info to build them and what they put out.  It's not too hard to guestimate what you are looking for in coil size magnets etc.. just by comparing the different ones. Pick one that puts out about 30-40 amps into a 12v battery at 600 rpm speed and you should be right in the ballpark as a match.

http://www.otherpower.com/otherpower_experiments.html

[twilightinsanity]

   Thanks for the links. They were really helpfull.

   With info from the various places ive gone while researching this, ive learned some useful stuff. Mainly, in respect to my problem Ive learned that RPM's are only half of the equation, the other half is wheel size (size matters after all). If the wheel is bigger around, the edges of it are moving faster, and so the magnets pass the coils faster and make more electron movement. Yay! Of course that has some drawbacks too, like increased weight, bearing drag, magnet cost, and plus most people dont want a giant metal disk in thier yard that spins around. Might as well wear a foil hat.

   Man Im full of jokes today... Heh - maybe later one will be funny.

   
   Anyway, I have a .5 Hp drill, and I lost the chuck so I have to put it in reverse to get the bit out and in (you know the deal...)  Well, it isnt too hard to stop that drill from turning with my bare hands (I'm no popeye, my hands are used to typing, not stopping things from turning) All I'm saying is if that .5Hp drill is so easy to stop from turning, then why is my .5 Hp wheel so hard to stop (It's impossible to stop it by holding on to the shaft, you have to really grab the edge and make faces and stuff.)

   So I have more torque than a windmill (20 ft) (I think) and the 20 inch dual rotor magneto on the windmill I saw made 3Kw (3000 watts right?) at 65 Rpm and cogged badly above 200. If I doubled the 20 inch diameter magneto to 40 inches around, and even keeping the origonal 20 magnets I'd get 3kw from 37 Rpm's of my wheel. Right? Then adding 20 more magnets and a proportionate number of coils would give 6Kw right? Double it all again (with a second row of magnets and coils) and it would be 12Kw Maybe 10, maybe more, but nonetheless a fair use of high torque and low Rpm's.

   I'm still wondering how the load resistance thing works, there must be a formula someplace. If the resistance to turning goes up with the amount of force being used by the load, or if the resistance to turning goes up in relation to speed or what...