Here's a link if you're not familiar with Shawn Frayne's
Watch out VIDEO!!!! There's a better looking video available on Revver, but here's the youtube. I'll state that the frequency is much higher than it appears in the video, it must be a consequence of the frame rate.
Step 1: The Frame
I started by measuring the widest window in my house, then I cut a board 52 inches long to fit and ripped it down to six inches wide. Then measuring in 4 inches from each end I drilled a 2 1/4 inch hole at either end and cut out the middle between them.
Step 2: Mount the Voice Coil and Magnets
This is pretty easy, pick an arbitrary spot on the center line at one end and use a nail through the bearing to mount the Hard Drive voice coil, a nut was threaded up the nail to hold the coil in place, the magnets are secured around the coil with wood screws.
Step 3: We Need a Way to Attach the Belt
I reshaped the heads on the voice coil by filing down and gluing on a couple of pieces of wood and then a half of a razor blade to give an attachment point for the belt, not elegant but it works for now.
Step 4: At the Other End
we make a bridge for the belt to go over and mount it to the frame. tensioning is accomplished by means of a tuning peg. The tuning peg is a pencil crammed into a hole ;-).
Step 5: The Belt
I grabbed the first thing available, a video tape. The belt is attached to the head with scotch tape, and at the other end to the "tuning peg" by scotch tape.
Step 6: Stick It in Your...
window and open a window on the opposite side of the house, the video shows it in operation, careful tuning of the belt tension causes the the voice coil to resonate, that's a good thing. Measured power output is 1.5 Volts AC with a short circuit current of 20 ma. The leads from the coil are attached to two LEDs wired in parallel with reverse polarities as suggested by Kiteman.
Suggested areas for exploration, personal and general.
I didn't rebalance the voice coil, I'd also like to try paring one down to reduce it's mass.
Hand wind (or stack multiples of) the coil to increase voltage output.
Try various belt materials.
Acquire some schottky diodes and make a voltage multiplying rectifier.
perhaps follow that with a blocking oscillator for battery charging.
And finally a Thank You to Alan Parekh for the LED's