Why is elastic suspension better than rubber mounting?

madman2003 · Post by **madman2003** » Tue Mar 15, 2005 6:09 am

Would a large enough rubber block of a certain size(and the right rubber) be able to achieve the same as elastic suspension.

If so, what kind of rubber and how big.

I have very little experience with quiet computers, but i'm considering what mounting options will be acceptable for me. (trying to think of a lot of things in advance before even having a single component

)

Elastic suspension seems a bit dangerous as far as moving the computer goes.

I'd like to know the why's too instead of the "it's just better".

A lot of thanks in advance.

EDIT: fixed title

IsaacKuo · Post by **IsaacKuo** » Tue Mar 15, 2005 7:40 am

The reason elastic suspension is better is because it transmits less vibration forces to the case, while also not restricting cooling airflow.

Compared to a rubber block, there are two big factors going on:

1. Forward/backward/sideways/yaw vibrations are more or less completely isolated by a typical suspension. To a certain extent, the drive is able to swing freely. In contrast, a rubber block can transmit these vibrations.

and

2. Up/down/pitch/roll vibrations are transmitted weakly by a suspension. To a rough approximation, the suspension material is a solid spring made of an elastic material with a certain cross sectional area. The maximum amount of force which it transmits to the case is determined by the maximum amplitude of the vibration, the modulus of the elastic material, and the cross sectional area. The maximum amplitude of the vibration is determined only by the properties of the hard drive. We can assume the rubber block and the suspension material have a similar modulus. That just leaves the cross sectional area--an elastic suspension has a very small cross sectional area, while a rubber block has a very large cross sectional area.

Think of it as the difference between a full bed of bedsprings versus just four springs in the corners. With a full bed of springs, it takes a lot of force to press them down by a centimeter. With just four springs in the corners, it doesn't take much force to press them down by a centimeter.

Post by **Rusty075** » Tue Mar 15, 2005 9:12 am

Madman, a good place to start is the sticky atop this forum: HDD vibration & noise reducing methods - ranked. Read that, and the threads linked within, and most of your questions on the how's & why's will be answered.

Zyzzyx · Post by **Zyzzyx** » Tue Mar 15, 2005 9:34 am

re: sorbothane vs elastic suspension

Ok, so sorbothane is a bit different than your standard 'rubber block. Currently I have my Cuda IV sitting on four 'cubes' of sorbothane instead of a couple strips. With just those four cubes supporting the corners of the drive, I find it equal to the elastic suspension I had rigged previously. The 'four cube' setup allows a fair bit of damped lateral motion, relative to what a hard disk wants to do inertially.

pro: easier to work with or change drives
con: need to keep the case upright when moving it around

(this post brought to you by morning office insanity)

m0002a · Post by **m0002a** » Tue Mar 15, 2005 7:05 pm

My opinion is somewhat different than many. I believe that using the right kind of rubber isolation is better than suspending a hard drive with elastic.

The best solution (IMO) is one that absorbs the vibrations, sound, and movements of the hard drive, while at the same time only allowing for very minimal movement of the drive.

But the problem with using rubber side mounts is that gravity puts too much pressure on the screw, so that the rubber grommets must be stiff enough to support the downward pressure of the screws because of the weight of the drive. Much better is a drive resting on rubber, but screwed from the bottom of the drive, which still holds the drive in place, but does not allow much sideways tension on the screws (this assumes that the drive is not mounted on edge). One example of this is using the Antec Sonata type drive trays, but resting the drive on long strips of rubber (such as Sorbothane or other high quality foam) and screwing the drive loosely from the bottom (making sure the grommets prevent the screws from touching the tray).

Suspending a drive with elastic allows the drive to move too much during operation. A disk drive engineer told me once that there are some “theoretical” problems with such a suspension related to drive efficiency and reliability, although I don't think there are any real numbers on this. So the best solution is one that provides sufficient isolation from the chassis, while at same time keeping the disk from moving as much as possible.

Not to mention the fact that an elastic suspended hard drive can be damaged if the PC is moved.

Zyzzyx · Post by **Zyzzyx** » Tue Mar 15, 2005 11:37 pm

addendum:

Here's a pic of my hard disk on the sorbothane 'cubes'.

Its really quite secure for lateral movement, I just can't lay the case on its side.

madman2003 · Post by **madman2003** » Wed Mar 16, 2005 12:49 am

Thanks for the info. But any kind of suspension i build in will have to be able to keep the drives safe when moving the computer. I have an idea or two about how it can be done, none of which are final. (or even drawn on paper)

burcakb · Post by **burcakb** » Wed Mar 16, 2005 3:51 am

One reason I chose the suspension method I did (see Thor in sig) is because if I ever need to transport my case a proper foam gasket on either end should keep the drive cage from rattling around during transportation yet still allow easy & quick install/uninstall.

m0002a · Post by **m0002a** » Wed Mar 16, 2005 7:09 am

madman2003 wrote:Thanks for the info. But any kind of suspension i build in will have to be able to keep the drives safe when moving the computer. I have an idea or two about how it can be done, none of which are final. (or even drawn on paper)

What case do you have?

madman2003 · Post by **madman2003** » Wed Mar 16, 2005 7:28 am

Nothing. I intend to built a prototype even before i have the case. I'm a bit unsure what case i will get, but these are on my list sofar:

Coolermaster Stacker (black)
Yeong Yang YY-0221B (black)

And perhaps: Coolermaster Stacker 830
(although i'm not extremely fond of it's exterior design)
(it might not even be available in a few months)

The Yeong Yang Cube seems the most likely atm, but anything can happen.

m0002a · Post by **m0002a** » Wed Mar 16, 2005 7:56 am

Here is a description of a method that I used on a Sonata case:
http://forums.silentpcreview.com/viewtopic.php?t=10450

Some people were a little confused looking at the pictures and assumed that the drives were not securely attached. The foam I used is high density and it is compressed, so that the drives are securely attached, but at the same time there is room for movement.

I just now moved the pics to a new server and changed the links. Let me know if you can't see them.

madman2003 · Post by **madman2003** » Wed Mar 16, 2005 8:23 am

Let me put it this way, any suspension i would use would still need to work with the case up-side-down. Most solutions seem a bit dangerous when it comes to transportation.

m0002a · Post by **m0002a** » Wed Mar 16, 2005 9:51 am

madman2003 wrote:Let me put it this way, any suspension i would use would still need to work with the case up-side-down. Most solutions seem a bit dangerous when it comes to transportation.

I agree. My implementation has the drives screwed from the bottom of the Sonata drive tray. It is very secure and it provides excellent damping and isolation of the drive.

If I were building a drive cage from scratch, then I would use a similar implementation as I did with the Sonata drive trays and the foam. Not necessarily using drive trays, but mounting the drive from the bottom. This allows for minimum tension on the screws, while still holding the drive in place when the case needs to be moved.

The key to building a secure mounting and one with maximum isolation is to use the foam on the screws from the bottom and foam under the drive (see my pics in thread mentioned above).

sgtpokey · Post by **sgtpokey** » Wed Mar 16, 2005 10:10 am

I have a bias against suspension. Not for any good reason though.

For instance, I do not believe suspension is a major issue during transportation. Those bungee type cords can be as secure and taut as you want them to be. If anything jarred them, you'd have bigger issues during transport.

So I think your particular worry may be not exist in practice.

For me though, I've used SmartDrive 2002-type enclosures and love them. At the time I reasoned that suspending solves a particular class of sound problem while an enclosure reduces a wider range of sound (I had a whiny WD at the time). I'm not sure if that is 100% true now.

If I really be honest about the choice though, it is because I just didn't think that suspending anything was "proper". Kind of like when I was a kid playing with Legos and I had certain ideas of what a proper Lego structure was (must use mini-figs, must use as few "custom" bricks as possible. Must conform to the rules of my imaginary universe)

I'll probably use a suspended 2.5" drive as my OS drive on my next build though.

Post by **Rusty075** » Wed Mar 16, 2005 10:23 am

Depending on how you rig the suspension, it can be completely secure for transport. For systems that I know will have to be transported I suspend the drive with three X's of Stretch Magic: one at the front, one at the rear, and a third running vertically down the longitudinal center. The front and rear segments support the drive vertically (both up and down) and horizontally side to side, and the third segment prevents excessive front to back movement. I'll try to dig up a pic later, its probably a bit confusing just describing it.

In my current main system I'm using a combination of several of the SPCR HDD Silencing techniques:

The drive is a 2.5" drive to start with, but it's a rather loud Seagate Momentus. I wanted the 100gig capacity, plus the price was right (free!)
The drive is mounted on 12 little sorbothane blocks inside an XTOR HDD enclosure. 4 blocks each on the top and bottom of the drive, with 2 blocks on each of the long sides to hold it in place. The remaining space inside the enclosure is filled with high density acoustic foam.
The enclosure itself is then suspended by Stretch Magic on its side across 3 5.25" bays in a Centurion V case.

Overkill? Probably, but the result is a drive that is inaudible from the user position. You can feel little twitches from the seeks if you put your hand on the enclosure, and hear remnants of the whine if you get your ear within 6" of the enclosure.

sgtpokey · Post by **sgtpokey** » Wed Mar 16, 2005 12:48 pm

The drive is a 2.5" drive to start with, but it's a rather loud Seagate Momentus. I wanted the 100gig capacity, plus the price was right (free!)

Quick question: is the Momentus "rather loud" relative to other 2.5" drives or is that compared to quiet 7200rpm drives?

Post by **Rusty075** » Wed Mar 16, 2005 12:54 pm

Louder than other 2.5" drives, but quieter than all but the best 3.5". Its seeks and vibration are lower than any 3.5" drive I've seen, but it has an odd motor hum/whine that doesn't want to go away.

Mike reviewed one a while back: http://www.silentpcreview.com/article145-page1.html

I think my sample is quieter than his (or my ears less sensitive to its frequency) but the noise characteristics are pretty similar.

madman2003 · Post by **madman2003** » Thu Mar 17, 2005 11:52 am

I made a drawing of the basic design i had in mind, all the dimensions are in comparison to the main shape. Feedback would be nice.

The small bars will be fitted with some kind of shock absorder in case the drive starts moving. The holes are for the elastic or whatever i'll use.

EDIT: forgot to say the idea was to screw 6 "eyes" into the harddrive and connect the elastic to that.