Combatting Oscillation with randomness for cooling fans and harddisks.

[Skybuck Flying]

Hello,

I just cleaned my PC today and I just noticed the fans started humming in
sync. They were all running at the same speed. Perhaps the humming is cause
by some dust which is on the fan blades, I am not sure, ultimately this
build up probably leads to them oscillating in sync. Like soldiers walking
across a bridge and causing the bridge to collapse (resonance).

But I did manage to get rid of the humming by using the following trick:

Since I have the antec 1200 case I can adjust the speed of each intake fan
individually with each fan's speed knub. So I put the fans at slightly
different speed and low and behold it got rid of the humming ! Perhaps some
of the humming is also amplified by cables pressing against the case doors.
Some cables are now loose since the sticky tape let go.

Right now 100% of the humming is gone ! Quite marvelous.

So this has given me an idea which could be applied in practice, it might be
a bit risky since it takes away control/precision from the user but it's
worth considering if not done already:

Harddisks produced by for example hitachi/ibm could spin around a slightly
random rounds per minute.

So instead of having an entire rack full of harddisks spinning at exactly
5000 RPM some might be spinning at 4999 or 4998 or 5001 ot 5010, I am not
sure what the speeds need to be to prevent osillation but probably very
little variation is already enough to stop the oscillation.

This might protect harddisk from resonance... tiny little oscilliations from
harddisk racks could make the head from the disk hit the platter. How real
this danger is I dont know...

Perhaps bumps against the table or pickup of case is main cause of bad
sectors.

At least the randomness could be introduced to cooling fans.

The randomness could be static/fixed... so each fan runs at slightly
different speeds...

Or even better it could be dynamic... if it's dynamic then buyers don't have
to be afraid that they accidently bought fans or harddisk running at exact
same randomness.

So dynamic randomness seems to be the better idea.

This entire idea is quite interesting... it's one of the first ideas I have
seen so far where "exact" is bad, and "slightly off" is good

Bye,
Skybuck.

 

[Kevin McMurtrie]

Hello,

I just cleaned my PC today and I just noticed the fans started humming in
sync. They were all running at the same speed. Perhaps the humming is cause
by some dust which is on the fan blades, I am not sure, ultimately this
build up probably leads to them oscillating in sync. Like soldiers walking
across a bridge and causing the bridge to collapse (resonance).

But I did manage to get rid of the humming by using the following trick:

Since I have the antec 1200 case I can adjust the speed of each intake fan
individually with each fan's speed knub. So I put the fans at slightly
different speed and low and behold it got rid of the humming ! Perhaps some
of the humming is also amplified by cables pressing against the case doors.
Some cables are now loose since the sticky tape let go.

Right now 100% of the humming is gone ! Quite marvelous.

So this has given me an idea which could be applied in practice, it might be
a bit risky since it takes away control/precision from the user but it's
worth considering if not done already:

Harddisks produced by for example hitachi/ibm could spin around a slightly
random rounds per minute.

So instead of having an entire rack full of harddisks spinning at exactly
5000 RPM some might be spinning at 4999 or 4998 or 5001 ot 5010, I am not
sure what the speeds need to be to prevent osillation but probably very
little variation is already enough to stop the oscillation.

This might protect harddisk from resonance... tiny little oscilliations from
harddisk racks could make the head from the disk hit the platter. How real
this danger is I dont know...

Perhaps bumps against the table or pickup of case is main cause of bad
sectors.

At least the randomness could be introduced to cooling fans.

The randomness could be static/fixed... so each fan runs at slightly
different speeds...

Or even better it could be dynamic... if it's dynamic then buyers don't have
to be afraid that they accidently bought fans or harddisk running at exact
same randomness.

So dynamic randomness seems to be the better idea.

This entire idea is quite interesting... it's one of the first ideas I have
seen so far where "exact" is bad, and "slightly off" is good

Bye,
Skybuck.

Hard disks must always be in a solid and dampening enclosure. The cheap
ones that vibrate will cause rapid failure regardless of the speed of
other drives.

Some new variable speed fans have slightly uneven blade spacing that's
supposed to reduce resonation.

There's also the perfect synchronization fix:
NTSC television had the vertical sweep phase locked to AC power so that
magnetic fields from power wires would not cause throbbing effects in
the CRT. If you had a CRT TV during the DTV transition, you probably
saw the wiggle and throbbing on some stations that got rid of the phase
lock.