Inspired by the wealth of hard-drive recycling ideas on hacked-gadgets and the >springverb research posted at Electronic Peasant.
When looking at both these pages... this hack becomes pretty obvious. It helps that i had all the materials laying around already.
2 junked hard-disc-drives which are pretty similar.
top removed and platters removed thanks to the handy torx-8 screwdriver.
had to remove the voice-coil to get the bottom platter out.
The motor shaft has a little cap to hold the platters in so this is used to mount the spring by threading some wire through the holes and bolting back onto the shaft.
One drive was bolted to a metal plate and the plate bolted to a heavy vice. The vice was bolted to a piece of wood. The other drive is just held in place with a smaller vice. as can be seen in the first picture at top, the circuit board was removed from the drive and 2 connectors on the back are connected via alligator-clips to the speaker output of a normal stereo amplifier.
It took a bit of searching to find which pins were actually connected to the voice-coil. I used an amp which has electronic circuit-breaker protection on the speaker outputs just in case... this would be recommended so as not to accidentally blow a fuse, or worse, wreck the amp.
At first i was going to use the voice-coils as the spring's actuators, but then i realized that the platter motors could do the same job. This did work, however, there were numerous problems. The driver was very sensitive to overloading and tripped the amp's circuit breaker all the time, even at fairly modest power levels. further, using one of these motors as a receiver lacked a good amount of gain. Getting this set-up to work well would probably be possible with some op-amps and stuff... who knows.
The drive's voice coils work much better as drivers and as pickups and it's a much more dramatic effect than the limited back and forth rotation of the platter motors. The whole drive starts to act as an audio speaker which is kind of cool, and cranking up the volume turns the thing into a sort of a percussion instrument.
I'm still trying to think of a good way to attach the voice-coils to the spring, but for the time being, I opted for a piece of slightly stiff wire. This adds a lot of resistance to the movement of the arm but (and) it does the job of transmitting sound rather well. A better solution needs to be found though, at the very least because the wire attached to the driver coil tends to break after some wear.
The angle of the wire to the spring, the physical resistance of the wire to the VC, the placement (rotation) of the spring all have a pretty dramatic affect on the sound, so the eventual solution should take all of this into account. As noted in the EP site, the spring should be allowed to freely rotate. The shafts to which the springs are attached achieve this, however, the motor around the shaft has magnets which can affect the rotation depending on where the resting point of the spring is. This could also come in handy in the future as it also has an affect on the sound.
