hard drive mod

How this was done:

I did this mod on my workbench–not a clean room by any stretch of the imagination. However, the airflow was minimal. No fans or ventilation of any kind to circulate air (and dust). I swept my benchtop with a bench duster before starting, and changed into a clean t-shirt, mainly to minimize dog hair contamination.

This is a Western Digital Caviar 21600, manufactured in January of 1996. I pulled off the “warranty void if removed” seal. To get access to all the screws, I had to remove the sticker with the drive info from the top casing. Then I used a 2mm flat blade screwdriver to remove the screws, which were a very small torx-type drive. I had a sealable bag ready to receive the drive once I removed the housing. I bagged the drive assembly and set it aside.

There is a metal plate affixed to the top drive housing that needs to be removed before cutting. I pried it off with a screwdriver, which marked up the top housing (made of aluminum) somewhat. Next time, I’ll probably use a heat gun to reduce the force required to break the adhesion.

The top cover has raised ridges, so I decided on a rectangular window inside the ridges in order to have a metal lip to make fitting the window as easy as possible. I marked off the lines and cut the window with a Dremel tool. The aluminum cut very easily. The material is not very thick (I didn’t take a measurement) and I suspect the purpose of the ridges and the adhesive plate is to add some rigidity to the housing. Anyway, cutting was a snap.

I ground down the edge slightly with a grinding stone Dremel bit, then used sandpaper to smooth the cut. I also used a needle file to clean the corners of any burrs. The window sits on top of the top housing, so I wanted no possibility of metal filings inside the drive.

When everything was smooth enough to satisfy me, I unleashed my secret weapon in the battle against contaminants: an 89-cent tack cloth. I thoroughly wiped the drive cover. The tack cloth has an electrostatic effect that helps the work piece repel dust after you wipe it. The edges of my cut did not snag the tack cloth, so I figured they were clean enough.

I cut the clear window insert about the way you would expect; I scored it with a utility knife (with a new blade) and snapped it against the edge of my benchtop. I ground the corners down with a Dremel for a nice finish, then sanded the edges lightly with 600 grit sandpaper.

I used clear silicone aquarium sealer to adhere the plexi to the drive housing. I applied the silicone quite thinly to the lip using a toothpick.

Once the adhesive set, I noticed that the plexiglass was a giant dust magnet. It had enough electrostatic charge to really pull in dust. I decided to use that feature in my favor. I had cleaned the window with glass cleaner before affixing it, and the wiping that ensued helped build up the charge.

I figured that if any dust had worked its way into the drive housing, the plexiglass would pull it up given the small distances. I unbagged the drive and grounded the aluminum chassis. Then I placed the cover on, and sure enough, a few small dust particles appeared on the inside of the window. I used compressed air to remove them, and repeated the cycle until I noticed no more dust (about another two times).

After I screwed the whole thing back together, I noticed that a plastic piece that fit between the upper and lower drive housings had fallen into the case. So I took the drive apart again, replaced the plastic plug and repeated the electrostatic dust removal drill.

With the screws tightened, there is still a small gap between the upper and lower drive housings. This is covered by a seal from the factory. I replaced the seal using tape printed on a label maker. It was very close to the correct width (a little too wide, though).

I couldn’t wait to see if it worked, so I mounted it in the only convenient machine, a FreeBSD box. The coolest visual was when the drive powered up. You can see the platter spin up, then the head scans from outer to inner edge of the platters a couple times very quickly. I wrote a disklabel and ran newfs, and all was well. I fsck’ed the filesystem I had just made, and no problems. I did not actually put the drive to any further tests at that point.

The next day I took it in to work, where we mounted it in a Windows machine. This time we did write a bunch of data and read it back, but the guys lost interest pretty quickly when it didn’t instantly burst into flames or anything. It is just a hard drive after all…

The punch line: this is a doable mod. Just use some sensible precautions. Stay away from air currents, ground yourself and the chassis frequently, pay attention to electrostatic charges.

As to the shower suggestion, I’d worry about condensation more than I worry about dust. If you have a clean room, go for it. Also keep in mind that this is an older drive, with larger geometry and less strict tolerances. Newer drives will be more sensitive to contamination.



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