Hard Drive Sandwich - Revisited

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Temperature Analysis

A Veriteq 1000 data logger with an accuracy of ¬Ī0.1°C was used for temperature measurements. I used an external "raw" 100K thermal sensor about the size of a flea, insulated the leads and stuck it in the top front corner of the HD, in a tiny cavity just beneath the top metal cover:

It was the only place on the top, closest to the platters, where I could place the thermistor with the metal sandwich on.

The data logger was set to read once a minute - every 60 seconds, it turns on, records the temperature, then turns off. The HD was placed on top of the PC case (for convenience). Measurements were taken as follows:

1) I ran Sisoft Sandra's HD burn-in utility for an hour with the bare drive, and then downloaded the data into the Spectrum program that comes with the data logger. Spectrum allows the data from loggers to be output as graphs or in numeric form.

2) This was repeated with the drive sandwich on. The starting temperature of the drive with the sandwich was 10°C higher, as I was too impatient to wait for the drive to cool down. But the temp still stayed 7°C lower after an hour!

The results can be seen in the accompanying chart. You can see how much slower the temp rises with the sandwich - the temperature gain for the whole hour is just 5°C (9°F), from 33°C to 38°C. This compares favorably to a whopping 22°C (39.6°F) rise in one hour without the sandwich. If the second test started with the sandwiched HD at 23°C like the bare HD, at the 5°C/hr rate, it would have taken 3 hours to reach 38°C! Would this really happen?

Intrigued, I ran Sisoft Sandra burn-in again with the sandwiched HD, this time with the starting temperature at 22°C. This chart is also shown: it took exactly 2 hours to reach 38°C. However, during the next hour, the temperature only rose 1.5°C! You can see how the slope of the curve becomes flatter and flatter over time, which suggests the reaching of equilibrium. In other words, the Sandra HD burn-in can't heat the drive much more.

At 3.5 hours, when I decided my hard drive had taken enough of a beating and stopped the burn-in, the temperature was still just 39.7C. At this rate, it might have taken another hour or two to hit 40°C. Practically speaking, it had reached thermal equilibrium.

Although this data is not included because of its unwieldy size, I also logged temps over a 24 hr period with the drive mounted normally in the computer, then again for 24 hrs with the sandwich on and the drive placed in the case (as described earlier). With the sandwich on, the temp rarely exceed 30-32°C, and reached a peak of 38°C during the 24 hours. With the drive mounted normally, the average temp was 39-42°C, and hit peaks of 46°C at times. (Generally, MBM5 shows my case temp to be 30°C or lower.)

Many hardware websites praise fan-equipped hard drive coolers for achieving just a couple of degrees of cooling. In this context, the HD sandwich's cooling is pretty amazing especially as cooling is not even its main function.

Further Clarifications on Use

  • In later versions of the HD Sandwich, I switched from bolts and nuts to self-tapping screws. With the correct screw length (usually 1.5", but depends on exact thickness of aluminum plates), this allows one outside (of the metal plates) to be completely smooth, which is more convenient to work with when trying to mount or place the assembly inside the PC case.

  • CAUTION: If the drive is clamped so that the side for connector is inset as shown in the sandwiched drive on the left in the photo above, the ridge on the IDE power connector can extert undue pressure on the HD connector by being jammed up against the aluminum plate. This may sound complicated, but it is actually very simple. Repeated plugging & unplugging made one of my drives unusable by creating an intermittent break in the power connector socket. The photo below shows the ridge on the IDE connector.
  • There are 2 simple solutions to avoid this problem:

    1. Cut away the ridge on the IDE power connector (just the one used to provide power to the drive) with a sharp utility or exacto knife.
    2. Mount the drive in the sandwich so that the connections are flush with the edge of the aluminum plates as shown in the sanwiched drive on the right in the top photo above.

The potential problem exists only with drives that have the IDE connector positioned flush against the bottom of the drive. The photo below shows an older Maxtor drive which has quite a larg gap between the IDE jack and its bottom. The modern Seagate Barracuda IV on the right has no gap. Most modern drive IDE jacks appear to be positioned like the Barracuda's.

Latest Enhancements

Several aspects of the way the HD Sandwich works became clearer to me as I continued experimenting:

  • Most of the cooling occurs via the top plate; heat rises.
  • Without the foam inserts around the sides, the sound reduction is minimal.
  • If the assembly is attached firmly or placed directly on the floor of the case, noise reduction suffers. The foam "bed" beneath the HD Sandwich is critical.
  • Many drives get hotter on the side with the exposed PCB. This is certainly true of the IBM 75GXP. Slightly better cooling is often achieved with the drive mounted upside down. I believe this is drive-specific.

Recent experience with suspending the HD in elastic showed very clearly the noise-reduction power of decoupling. That and discussions about cork on the Yahoo! Silent-PC Group made me seek out these idle cork coasters in a junk drawer in the kitchen. Two of their number were lost to the cause of drive silence: they were put to work as a damping layer between the bottom aluminum plate and the upside down drive. A bit of glue keeps them in place.

It does decrease the noise somewhat, compared to a sandwich with no cork. I have not measured the difference. If a sandwiched drive is already inaudible in your PC, there's no point. If you're builidng one from scratch or still need more drive noise reduction, the cork addition is probably worthwhile.


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