I'm doing an independent study for high school, and my project is to build a wheel motor such as the one pictured here (though less complex, obviously). Essentially what I'm trying to do is to make an inverted stepper motor, with the electromagnets on the hub and the permanent magnets on the rim. As my knowledge of electromagnetism is fairly limited, I've been having some trouble making electromagnets strong enough to influence the magnets on the rim. I know the basics of electromagnets (ie. more turns = stronger field, using an iron core), but so far I haven't been able to get the field strength that I need. At the moment, I'm using the 30-gauge wire from here, but I haven't been able to find a good core material around where I live. Any advice on where to get good iron cores or general advice about making the electromagnets stronger would be greatly appreciated. In addition, I plan on controlling the electromagnets with a stepper motor controller; is this a decent idea?