Here's one I made from a plastic barrell. It holds 300# of corn.
I'm going to try using a pipe next year instead of a spinner.
http://www.racksnspurs.com/images/Feeder.jpg
Here's some close-ups...
http://www.racksnspurs.com/images/Feederbot.jpg
http://www.racksnspurs.com/images/FeederPipe.jpg