Effects of cantilever stresses on hard drives

  • Thread starter Thread starter Analabha Roy
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A

Analabha Roy

Hi,

I've been making some upgrades to my
home Box (initially, a Gateway 310X running
Fedora 3). Among them was getting a scsi hdd
(Seagate Cheetah ST336607LW:
http://www.seagate.com/cda/products/discsales/marketing/detail/0,1081,541,00.html)
..

The hdd was too noisy (though really fast, 10000 rpm, woo!) & the hddtemp
daemon that monitored the smart disk temperature sensor on the HDD was like
47 Centigrade (the specs put upper bounds at 54). So I decided to get a
cooler/noise reducer, specifically the Zalman ZM-2HC2 Silent Hard Disk
Cooler:
(http://www.zalmanusa.com/usa/product/view.asp?idx=74&code=019)

Now, if you see the movie on their site, the instructions for installation
seem pretty clear. I am to first mount the cooler on the hdd, then screw in
the bolts through the blue Aluminum brackets into the hdd screw-grooves
(once they're lined up with the bracket grooves). After that, I am to screw
in the 4 rubber dampeners. Then, I am to slide the whole thing alonf the
dampeners into the 5.25 inch bay and use the smaller bolts to screw it in.

Here's the problem. The width of the hdd is slightly less (like 1/2 mm)
than the distance between the brackets (see
http://www.ph.utexas.edu/~daneel/hddstress/pic1.jpg)

The bolts that they supplied go into the Aluminium brackets no problem, but
they stick out by like 1 thread, so they only go into the grooves on the
hard drive on one side (see
http://www.ph.utexas.edu/~daneel/hddstress/pic2.jpg)


Thus, there is a slight (less than 1/2mm) misalignment on the other side.
This did not affect the ability of the hdd to mount, because I put it on
the lowest shalf of the 5.25 bay and there is a base below the mount
supporting the
brackets (but not the hdd, which is suspended over air, see

http://www.ph.utexas.edu/~daneel/hddstress/pic3.jpg)


This makes one end of the hdd "hang down" (not noticeably) and a cantilever
stress acts on it due to the weight of the disk. The mount really works. I
can barely hear my hdd and the average temp has gone down by a few degrees.

I would be very grateful if somebody could inform me (or offer anecdotal
experience) about the effects of the abovementioned stress on the
reliability and shelf life of these kinds of scsi hard drives (I googled a
bit but found nothing much). Also, what are the risks of any damage
occurring here? Can any components break? How robust ARE these Seagate SCSI
disks really?

Also, the entire mount is basically hanging by the rubber dampers. Since
they are rubber, there is a spring action (probably why it damps out the
sound) that causes to hdd to oscillate if slightly disturbed. Thus, it's
not mounted flush exactly.

I wish I could articulate my configuration better, but I'm rather new to
this sort of thing so I apologize if I haven't been able to get my
particulars across clearly and unambiguously.

Please let me know if there is anything I can do (or if it is necessary) to
improve my mounting of this system.


Regards,
AR
 
Analabha Roy wrote:

[snip]
Please let me know if there is anything I can do (or if it is necessary) to
improve my mounting of this system.
Click to expand...

I think you've thoroughly explained yourself.

I suspect that the stress you note is not of great importance, as the
drive is rigid enough to withstand it. You considerations in mounting
it should be to:

1) Mount it horizontally or vertically. You have apparently
accomplished that to within a fractional degree, so no problem there.

2) Insulate it from shock. I can't say if your drive is more or less
suceptible to shock given the dampening effect of the rubber
grommet-thingeys, but a tower should be removed enough from impact to
make it a non-issue.
 
,SNIP,
Thus, there is a slight (less than 1/2mm) misalignment on the other side.
This did not affect the ability of the hdd to mount, because I put it on
the lowest shalf of the 5.25 bay and there is a base below the mount
supporting the
brackets (but not the hdd, which is suspended over air, see

http://www.ph.utexas.edu/~daneel/hddstress/pic3.jpg)


This makes one end of the hdd "hang down" (not noticeably) and a cantilever
stress acts on it due to the weight of the disk. The mount really works. I
can barely hear my hdd and the average temp has gone down by a few degrees.

I would be very grateful if somebody could inform me (or offer anecdotal
experience) about the effects of the abovementioned stress on the
reliability and shelf life of these kinds of scsi hard drives (I googled a
bit but found nothing much). Also, what are the risks of any damage
occurring here? Can any components break? How robust ARE these Seagate SCSI
disks really?

Also, the entire mount is basically hanging by the rubber dampers. Since
they are rubber, there is a spring action (probably why it damps out the
sound) that causes to hdd to oscillate if slightly disturbed. Thus, it's
not mounted flush exactly.

I wish I could articulate my configuration better, but I'm rather new to
this sort of thing so I apologize if I haven't been able to get my
particulars across clearly and unambiguously.

Please let me know if there is anything I can do (or if it is necessary) to
improve my mounting of this system.
Click to expand...
although what you've done will not hurt the HD at all...
it's still going to bother you for years to come...
so why not just get a few screws that are a bit longer...and be done with it
 
Hi,

I've been making some upgrades to my
home Box (initially, a Gateway 310X running
Fedora 3). Among them was getting a scsi hdd
(Seagate Cheetah ST336607LW:
http://www.seagate.com/cda/products/discsales/marketing/detail/0,1081,541,00.html)
.

The hdd was too noisy (though really fast, 10000 rpm, woo!) & the hddtemp
daemon that monitored the smart disk temperature sensor on the HDD was like
47 Centigrade (the specs put upper bounds at 54). So I decided to get a
cooler/noise reducer, specifically the Zalman ZM-2HC2 Silent Hard Disk
Cooler:
(http://www.zalmanusa.com/usa/product/view.asp?idx=74&code=019)
Click to expand...

Unfortunately, it's more of a marketing gimmick than a good
cooling solution, because the part needing cooling the least
is the outer edges of the frame. It doesn't address the
circuit board component cooling at all, even worse- it
restricts airflow so those parts may end up hotter.

The correct cooling solution is that used professionally,
adequate space around the drive and plain-old-airflow,
whether it be a large opening for passive intake, a pusher
fan, or a puller fan array in the middle of the case (more
common on large/proprietary servers).


Now, if you see the movie on their site, the instructions for installation
seem pretty clear. I am to first mount the cooler on the hdd, then screw in
the bolts through the blue Aluminum brackets into the hdd screw-grooves
(once they're lined up with the bracket grooves). After that, I am to screw
in the 4 rubber dampeners. Then, I am to slide the whole thing alonf the
dampeners into the 5.25 inch bay and use the smaller bolts to screw it in.

Here's the problem. The width of the hdd is slightly less (like 1/2 mm)
than the distance between the brackets (see
http://www.ph.utexas.edu/~daneel/hddstress/pic1.jpg)
Click to expand...

That will cause poor contact with the drive. If it weren't
for the heatpipes, I'd suggest cutting a block of wood to
the width of the HDD, then using a vice to *force* the
cooler's plates to narrower, still-parallel dimensions.
Unfortunately the heat pipes are a concern as breaking a
seal on one will cause loss. It might work fine or might
damage it- I wouldn't guess.


The bolts that they supplied go into the Aluminium brackets no problem, but
they stick out by like 1 thread, so they only go into the grooves on the
hard drive on one side (see
http://www.ph.utexas.edu/~daneel/hddstress/pic2.jpg)
Click to expand...

Bending the frame would help, but getting longer screws
would too. They're 6/32, available at most hardware stores.
The recessed head could make it harder to find some, most at
hardware stores are pan-head but you may have a good
hardware store nearby.

Thus, there is a slight (less than 1/2mm) misalignment on the other side.
This did not affect the ability of the hdd to mount, because I put it on
the lowest shalf of the 5.25 bay and there is a base below the mount
supporting the
brackets (but not the hdd, which is suspended over air, see

http://www.ph.utexas.edu/~daneel/hddstress/pic3.jpg)
Click to expand...

The cooling is dependent on maximizing contact area between
the cooler and the drive frame. The issue is then not
whether it's hanging on one side (which should not be much
of a problem except it's not rigidly fixed, might move a
little), rather that the already poor performance of the
cooler is far worse due to lack of contact. Frankly I
suspect the drive's important parts will remain cooler if
you just remove the cooler, use normal 5 1/4" mounting rails
and use a front bay cover with a lot of open intake area.
This assumes adequate exhaust rate from system case so it
doesn't alter flow patterns in other areas too much.

This makes one end of the hdd "hang down" (not noticeably) and a cantilever
stress acts on it due to the weight of the disk. The mount really works. I
can barely hear my hdd and the average temp has gone down by a few degrees.
Click to expand...

This temp might indicate it's working a little, but on
multi-component piece of equipment it's usually just the
state of a single chip, or even no chips, just the thermal
sensor. The more unusual the cooling, the less likely the
temp report will be an accurate reflection of the entire
drive's state, because the temp report is calibrated for a
normal use/cooling environment. In other words your cooler
might be doing better or worse than the reported temps
suggest, and since the margin of error has gone up it's a
less reliable report than previously.

I would be very grateful if somebody could inform me (or offer anecdotal
experience) about the effects of the abovementioned stress on the
reliability and shelf life of these kinds of scsi hard drives (I googled a
bit but found nothing much). Also, what are the risks of any damage
occurring here? Can any components break? How robust ARE these Seagate SCSI
disks really?
Click to expand...

The frame is plenty strong enough, you'd more likely bend
the screws if there were that much (excessive) stress.

Also, the entire mount is basically hanging by the rubber dampers. Since
they are rubber, there is a spring action (probably why it damps out the
sound) that causes to hdd to oscillate if slightly disturbed. Thus, it's
not mounted flush exactly.
Click to expand...

Not good, you might very-lightly put your finger on it to
determine how much it's vibrating when doing something
seek-intensive, like defragging the drive.
I wish I could articulate my configuration better, but I'm rather new to
this sort of thing so I apologize if I haven't been able to get my
particulars across clearly and unambiguously.

Please let me know if there is anything I can do (or if it is necessary) to
improve my mounting of this system.
Click to expand...

You could find a 0.5mm piece of copper sheeting to use as a
shim. It won't be as good as direct contact, but a whole
lot better than air. Get longer screws. I'd still think
about removing the cooler completely and just using airflow,
but if you use the cooler it still helps a lot to have more
airflow- passive coolers still depend on temp of air around
them.
 
Bending the frame would help, but getting longer screws
would too.
Click to expand...

Note that I meant bending the cooler's frame to the right
width, not bending the hard drive frame.
 
Thanks for the input. I used the frame primarily to reduce noise (and boy
does it, I could actually sleep while leaving the compu on). I think best
to just buy longer screws. #6, right? Just ordered them from bolt depot.


Thanks again,
AR
 
Thanks for the input. I used the frame primarily to reduce noise (and boy
does it, I could actually sleep while leaving the compu on). I think best
to just buy longer screws. #6, right? Just ordered them from bolt depot.
Click to expand...

They are "6-32", whatever length you need. I may have
written 6/32 previously which could be interpreted wrong as
that was not meant to be in fractions of an inch.
 
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