Hard disk fastened with only two screws more prone to vibrations.
 

Hi:

Due to the construction of my desktop cabinet, I cannot fasten the hard disk with four screws. With only two screws, both on the same side, the drive is subject to more vibrations, the vibrations originating within the drive itself, above all each time it starts to spin. Is this really a problem, I mean, there must be many chassis built this way?

Although current hard drives are much better balanced than older drives, some vibration still occurs.

What is vibration? If there is some unbalance in the spinning mass of the hard drive, periodic forces are exerted on the entire hard disk which is not moving.

When the hard disk is totally free to move this forces cause the disk to move back and forth in space in the direction of the force cause by unbalance. When the disk is totally sturdy and unmovable, the forces do not cause movement, but they are taken up by the construction. This dissipation of the forces causes compression and extraction of the solid material between spinning platter and the unmovable part. Don't take the unmovable part to literal: the PC case is many times more flexible than a hard disk enclosure.

So I am not even sure what is better, a hard disk which is free to move and vibrates a bit, or a sturdy mounted disk which is dissipating away the forces.

Since (very) older hard disks were mounted on rubber supports, I would say movement due to vibration is harmless. If you fasten you hard disk with only two screws that is fine. I have done it for years myself. Don't worry about hanging or supporting the disk on one side only. The disk enclosure is much more rigid than needed to prevent deformation from it own weight.

jlinkels

PS Heck, I have hung disks at their power connector. Now that is really bad -- for the connector, not for the disk. It swung happily around.

Your problem sounds like you must remove part of the mount from the cabinet and attach left and right hand pieces to the harddrive, then reinsert into the cabinet.

Right. But is it not difficult to extract the front cover? The dealer told me the could be a problem with the cables.

OK. I was trying to make a reasoning here and did not reach anywhere. So, pc builders (people who put the parts together and sell directly to you), probably without knowing, do right. I use only two screws in the future but, still, I think that the manufacturer should produce himself in this matter, stating some words in the booklet.

Well I wouldn't agree that case builders make two holes inaccessible so you won't be tempted to fasten a disk with more than two screws. I'd regard it as sloppiness in the design anyway. But harmless sloppiness.

While there is nothing wrong with fastening with two screws, it is insane to make 4 holes and 4 sleeves on each side and then make one side inacessible.

The mathematically correct way to fasten a plane is with 3 screws because three points fully determine a plane. Four points can impose stress on a body.

But then again, the case is much more flexible than the disk so this is all highly academical.

If you have two holes accessible, use them and don't worry.

"Highly academic", I don't think so. Of course the hd is very rigid, much more rigid than the chassis, but that is not the point. The point is acceleration. Microvibrations can amount to several Gs, like droping the drive from, say, 1 cm? And the disk will _never_ be perfectly centered, hence, vibrations. If these vibrations find one of the resonance frequencies of the chassis, well, it will be detrimental to the disk life.

Only explaining my point. Apart from this, I accept your word. Thanks for your posts.

EDIT: of course the cabinet resonance frequencies are rather low. But the disk is also spinning at low angular velocity (say 5000rpm?, equivalent to 5000Hz).

All HDDs I have installed in my desktops are fastened by 4 screws or screw-like devices. I've never seen one that only has 2.

I think you missed a factor of 60 converting from RPM (minutes) to Hz (seconds). If my disk drives screamed at 5000Hz they would drive me out of the room immediately. A little 90Hz (5400RPM) doesn't cause a problem.

Common drives are used in construction, automation, military and other harsh environments. Those users are putting some fantastic loads on a drive. I doubt you'd loose many real hours of life in a simple home setup.

Quite often they are lazy bastards who will skimp on details beause as far as they are concerned, no-one will ever see them.

Find a piece of foam rubber weatherstripping, cut a piece slightly larger than the gap on the unscrewed side, and wedge it in there. That will absorb the vibration, quiet it down, and support it somewhat.

I was ranting at a disk drive bay where there was no way to get right side screws in it.
It seemed that they expected the drives to be installed before the motherboard.
Then I discovered the little release catch that allows the disk drive bay to rotate and release from the rest of the machine. Got much easier after that.

Check for a silver flat piece of spring metal at the edge of your disk drive bay.
On this one model, pushing the spring metal allows the back of the bay to rotate towards you, and then some tabs come out of slots in the top and the whole drive bay falls into your hands.
Disconnect the drive cables first, because it becomes difficult to do it when the bay is in your hands, and trying not to crush the memory.

Member Response
 

Hi,

I agree with cascade9. If the bay is 3 1/2 then most internal 3 1/2 HD will fit and allow all mounting screws. If this is a removable drive bay then remove the bay and install the screws. Make sure not to over torque the screws.

If this happens to be a 2 1/2 then someone kludged the install. You should get a 2.5 Inch to 3.5 Inch Internal Hard Disk Drive mounting rail kit. This type will allow you to mount the drive internal to the kit as one piece.

I have seen mounts where only one rail is installed and the other side rail is not mounted. Just poor build and sloppy work.

I had never thought about screws affecting "endogenous" vibration. I've always thought they're there not so much to deal with vibration but rather to just keep the HDD there (when there is nothing but the screws to hold them there... I never knew they made cabinets so cheap as this... until I had one, I was just unscrewing an HDD or DVD, not worried about a thing, and it fell...) or to keep them from sliding when you move the computer (turned off). And that the sort of vibration you'd need to worry would be from bumping on the table or something.

Now all this talk made me worried about having a DVD drive in the same cabinet as the hard disk(s). An external DVD should be safer....

Member Response
 

Hi,

I believe everyone is making a lot to do about nothing. If the spinning disk had excessive vibration then it would not be long before a head crash. Everything mechanical has a resonant point, you just do not want to remain within that range very long or boom.

You can provide shock insulation mounts to help limit reverberation within the case. The spinning CD/DVD balance is handled by the firmware for read/write. Continued unbalance can cause some vibration that would be transferred throughout the system. Magnitude would be dependent on the mass of the spinning disk and uneven platter causing vibrations.

If you are worried about noise & vibration(s) then move to a 'SSD' as the primary drive.

Anyone who believes that even minor vibration is not an issue for disk drives should watch this video. http://www.youtube.com/watch?v=tDacjrSCeq4

That's impressive, but I wonder whether it was just the scream or he just lightly/maybe even accidentally "bumped", just by touching, the hdds with the hands has he made them into a "horn" to shout at them.

They should do that on mythbusters and have a tenor on the datacenter to do the yelling.

The military mount their electronics on shock absorbing cabinets. The mounts on the cabinets are made in various ways. Some use springs with rubber inserts, some use looped wire cable.
The point is dampening. Like I said, to keep vibration under control, the best thing is that heavy rubberized weather-stripping with the peel off adhesive back. Been using that stuff on most every vibration problem for years.

Most cabinets do not come with proper instructions. Some expect you to buy the special drive mounting rails that screw to the drive and then slide into the bay. I make my own from metal sheet with a little springiness to them.

Better towers and desktops since 2000 have had a removable bay. The main problem being figuring out how to release it. Even on the Compaq little desktop had a hard drive bay that rotated (which I discovered only after trying for hours to get the drive in there the hard way).

Two screws instead of four causing excessive vibration? What about the one's that use ANY screws whatsoever? Then, they should be vibrating like hell.

I agree with onebuck, everyone is making a lot out of nothing.

My Jurassic-era Dell machine (over 12yrs old now, will be a teenager soon) had the original 80GB HD just slid in between two green plastic brackets with clips at the rear to hold the drive from sliding out. Oh yeah, and it's still working. It's been through hell (XP2000 :-)), Linux and now it's back to hell and still working.

Two screws, don't worry, it'll still work. It's the quality of the drive that will cause it to fail prematurely rather that the two or four screws.