Re:Works great if you have a clean room available
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Clear Hard Drive Mods
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· Score: 1
oops, the surface roughness of the "linoleum" is about.04" not.004". Let's call it 60grit sandpaper instead of lineoleum.
Steve
Re:Works great if you have a clean room available
on
Clear Hard Drive Mods
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· Score: 1
Let's clear up this 747 flying at 1/4" over the Rockies analogy. A "slider", the part that actually "flies" over the disk, is approximately 1mm square. The back end of the slider is about.5 micro-inches above the disk surface. The middle radius of a 7200 rpm drive is about 1 inch. The surface roughness of a typical disk today is about 5-10 Angstroms (rms). So let's scale this up by a factor of a million and convert into English units. The slider will be about 3 x 4 foot sheet of plywood floating half an inch above a linoleum floor with a roughness about.004 inches. But, that floor is moving under the slider at 43 MILLION miles per hour! Steve Marshall
Re:Works great if you have a clean room available
on
Clear Hard Drive Mods
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· Score: 5, Informative
I am a test engineer for Maxtor in advanced recording technology. It's actually quite amazing how robust these things are given the dimensions we're working at, it can actually be quite difficult to get a head to crash. Now I am in no way condoning this mod but this issue of "dust" needs a little clarification. It is virtually impossible for dust to get between the head and the disk. Imagine the 747 flying 1/4" above the ground analogy. On that scale a dust particle is about the size of house. The head will simply knock any dust particles out of its way. Even smoke particles are huge compared to the sub-micro inch spacing between the head and disk. Having said that however there is a contamination issue but from materials much smaller than dust. Molecular out-gassing is a big problem in drives and every material inside the drive is tested and appropriate filters are built into the drive to trap these gasses. Putting a big slab of plexiglass in the drive enviroment simply was not accounted for when designing those scrubbers. There is also the issue of humidity and the resulting corrosion.
What REALLY scares me about this procedure is that Saran Wrap casually draped over the drive while the cover is being hacked up. What kills heads these days is static charge. That Saran Wrap is one of the most easily charged materials in the known universe, and it only takes a few volts to kill a head. And then, the window itself is plexiglas, another material that charges up just by looking at it.
So, while I might take exception to the issue of dust, I'm in total agreement that this mod is simply a BAD IDEA. If you do it, do it for show only, do not put any data on it that you can't afford to lose at any moment and without warning. Failure may not be immediate but will almost certainly be instantaneous and catastrophic when it does occur.
Steve
Here is how I heard the hack described when I was an undergrad. I heard it from an alumnus who claimed to be one of the perpetrators.
The hack took place on one of the Green Line trolleys at one of the BU stops that is consistently crowded. The hackers made up several dixie cups of thermite (a mix of several metal powders). This stop was chosen because the traffic volume would ensure that they would have enough time to place the cups in front of the wheels on the rails. When the trolley rolled over the cups, the current flow through the thermite ignited it, welding the wheels to the track.
Another hack on the trolleys involved greasing the tracks where they come up from underground past Kenmore Square...
Steve
Slashdot Mirror
oops, the surface roughness of the "linoleum" is about .04" not .004". Let's call it 60grit sandpaper instead of lineoleum.
Steve
Let's clear up this 747 flying at 1/4" over the Rockies analogy. A "slider", the part that actually "flies" over the disk, is approximately 1mm square. The back end of the slider is about .5 micro-inches above the disk surface. The middle radius of a 7200 rpm drive is about 1 inch. The surface roughness of a typical disk today is about 5-10 Angstroms (rms). So let's scale this up by a factor of a million and convert into English units. The slider will be about 3 x 4 foot sheet of plywood floating half an inch above a linoleum floor with a roughness about .004 inches. But, that floor is moving under the slider at 43 MILLION miles per hour! Steve Marshall
I am a test engineer for Maxtor in advanced recording technology. It's actually quite amazing how robust these things are given the dimensions we're working at, it can actually be quite difficult to get a head to crash. Now I am in no way condoning this mod but this issue of "dust" needs a little clarification. It is virtually impossible for dust to get between the head and the disk. Imagine the 747 flying 1/4" above the ground analogy. On that scale a dust particle is about the size of house. The head will simply knock any dust particles out of its way. Even smoke particles are huge compared to the sub-micro inch spacing between the head and disk. Having said that however there is a contamination issue but from materials much smaller than dust. Molecular out-gassing is a big problem in drives and every material inside the drive is tested and appropriate filters are built into the drive to trap these gasses. Putting a big slab of plexiglass in the drive enviroment simply was not accounted for when designing those scrubbers. There is also the issue of humidity and the resulting corrosion. What REALLY scares me about this procedure is that Saran Wrap casually draped over the drive while the cover is being hacked up. What kills heads these days is static charge. That Saran Wrap is one of the most easily charged materials in the known universe, and it only takes a few volts to kill a head. And then, the window itself is plexiglas, another material that charges up just by looking at it. So, while I might take exception to the issue of dust, I'm in total agreement that this mod is simply a BAD IDEA. If you do it, do it for show only, do not put any data on it that you can't afford to lose at any moment and without warning. Failure may not be immediate but will almost certainly be instantaneous and catastrophic when it does occur. Steve
Here is how I heard the hack described when I was an undergrad. I heard it from an alumnus who claimed to be one of the perpetrators. The hack took place on one of the Green Line trolleys at one of the BU stops that is consistently crowded. The hackers made up several dixie cups of thermite (a mix of several metal powders). This stop was chosen because the traffic volume would ensure that they would have enough time to place the cups in front of the wheels on the rails. When the trolley rolled over the cups, the current flow through the thermite ignited it, welding the wheels to the track. Another hack on the trolleys involved greasing the tracks where they come up from underground past Kenmore Square... Steve