Bill's Recycled, Fanless, Silent Woodbox Computer

Do-It-Yourself Systems
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SILENCING THE HARD DISK

I used an old 3.5" IBM 20GB hard disk that had a reasonably low 6.5W power consumption, but an unreasonable sound level.

To silence the rather noisy hard-disk, I suspended it with foam rubber mounts inside a die-cast box (170mm x 115mm x 55mm) and sealed the lid with a 1mm diameter drive belt from an old VCR. The result was quite astonishing. The high frequency whine that the disk made became inaudible. The HDD case is itself rubber mounted to the chassis to remove most of the lower frequency vibration. Each of the four mounts for the HDD case consists of two 8mm M3 threaded spacers super-glued into a short length of 8mm diameter rubber tube.


HDD enclosed, gel-packed and suspended.


A 1mm diameter drive belt from an old VCR used as the gasket seal for the HDD box.

Unfortunately the IBM HDD did not have the on-board temperature monitoring of some newer drives, so I could not monitor the temperature while from the desktop but, measurements with a thermocouple on the drive in its case showed it running at 35°C above ambient (52°C) too hot for comfort and too close to the manufacturers 55°C maximum.

I decided to try to reduce the HDD temperature by improving the thermal coupling between the HDD and its case. In order to avoid any mechanical coupling I decided to use a gel pack. Initially I looked at medical gel packs which are well made and sealed, unfortunately one I had was too large and I couldn't find one advertised that was small enough to fit in the box with the drive, so I thought I'd try to make my own.

With a quick search on the web I found that water based gels are usually made with methyl cellulose and that this is found in many applications that need to absorb water, like disposable nappies (diapers) and, most usefully, wallpaper adhesive. I used a small zip-top bag, part filled with wallpaper paste mixed to the consistency of runny porridge, to fill the gap between the drive electronics and the lid of the die-cast box. The result was a 10ºC drop in temperature without any additional noise.


Original gel pack to help transfer HDD heat to the casing.

After a couple of months of use, I found that the foam rubber (actually polyurethane) had squashed down under the weight of the drive and, consequently, the drive had started to produce an audible hum. So, I took the opportunity to experiment further with the gel pack idea. I replaced the foam blocks, spacing the top of the drive away from the box, with a larger home made gel pack. After testing it for a couple of hours with some hard disk thrashing, the temperature of the drive reached 37ºC (about 15ºC above ambient). The drive was still pretty quiet (only the faint head seek clicks were audible in the workshop), but the large gel pack had coupled some of the drive noise to the HDD case.


V2: Larger gel pack.

Nine months later, I acquired a replacement for the original IBM drive, a much quieter 40GB Seagate ST-340810, and replaced the foam suspension with a rubber-based foam, used for sealing doubled-windows. The machine was then incredibly quiet; even the drive seek clicks were inaudible in normal use.


Version 3: A new quieter drive.



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