Coil sizing

[Monzadude]

I've read that when making coils that the opening in the middle should be the same size as the magnets. Is this right? I'm trying to make just a small genny just for fun to see if I can do it. Then comes the bigger ones. If I'm using mirowave mags can I just make the coil round to keep size down? These magnets are all I have and my present budget is $0. Most of the coils I've seen on here have some flat sides. Is there a reason for this? How thick should a coil be?

Bill

[DBGenerator]

"Theoretically" the center of the coil should be the size of the magnet.  It looks like most of the large brake disk projects that I have seen kind of ignore that rule.  The distance between the center of the legs of the coils should be the same as the distance from the center of one magnet to the other.  That is the most effecient use of the magnet.

Trapazoid coils are the most effecient shape, but take up more space.  Maybe try round or rectangle.  They end up in kind of an oval shape.

The larger the diameter (smaller AWG) of the wire, the more current it can carry.  If you use thincker wire, then you need a stronger magnet.

If your taking apart microwaves, then there are fan motors in there that should have magnet wire on it.  The transformers also have wire on them, but they are a pain to take apart without damaging the wire insulation.