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Shielding An HD From Excessive Vibrations? 37

Posted by Cliff from the bass-fo'-yo'-face-but-not-fo'-yo'-platters dept.
schematic asks: "I'm planning on building an mp3 player for my car, but a few of my buddies brought up a good point yesterday. They asked how I'd planned to mount the hard drive to protect it from vibrations (bass) and bumps (crazy driving). I've heard of a few good ideas, but I dont know what I can do to shield it from the bass, since that seems to shake the daylights outta everything. Anyone have a similar setup or an idea that works?"
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Shielding a HD from Excessive Vibrations? More

Shielding a HD from Excessive Vibrations?

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  • ya but, now this "player" will be bigger than most notebooks; tape drive, cdrom/zip drive, mother board (and cpu/ram ect.), lcd display of some sort.

    It might just be easier and cheaper to spend 150 or so on a mp3 playing cdplayer or even take the cdplayer already in there and just burn the music.. :)

    - eViL aSe

  • I've been thinking about this, too... One idea is the CD-Rom drive from a portable, if that'll stand up to reasonable, everyday driving. (i.e. on the roads... I don't suppose that you're intending to listen to the music while doing the Paris-Dakar rally, are you?)

    But the best way I can think of to avoid vibrations and G-shocks damaging moving parts (like drive spindles, heads) is to simply get rid of them. Go for 100% solid-state, disk-on-chip, PCM-CIA, whatever they're called now... You know, the things just made for hostile environments and embedded systems...

    Can you imagine a LART with a couple of gigabytes of solid-state silicon discs?

  • NoVibes (Score:1)

    by sfid ( 33738 )
    I use this [noisecontrol.de] in my computer to soften the noise from the hard drive. Maybe you'll need something like this?
  • IFAIK it's not just goop that helps make that model work; the insides have been modified. Of course, that's only what a flatmate told me so ignore all that.

  • Vibrational modes (Score:3)

    by adipocere ( 201135 ) on Tuesday September 12, 2000 @01:37PM (#785517)
    Your first step is to identify your vibrational modes. For example:
    • Subwoofer: Assume that you will be protecting against 10 Hz to perhaps 100 Hz
    • Random shocks: No guess as to the frequency of these.
    • Figuring out the direction of these vibrations is important. Will they be going from side to side? Up and down? Front to back?
    Examine the materials that came with your hard drive. Many of them will talk about what kinds of vibrational modes they are rated for, what they can withstand, etc. Compare to the directions of your vibrational modes to find in which to mount your hard drive. That is, if your vibrations are mostly side-to-side, mount your hard drive such that your most vulnerable direction (for example, perpendicular to the platters) is not parallel to the side-to-side vibration.

    Now, another important part is that you want to damp the vibrations in multiple modes. That is, you want to guard against as many big modes as possible. If you have a contraption made from bungee cords, it will damp best against a specific frequency (and possibly some harmonics), but the damping will be less effective at other frequencies. Where the weak patches are, damp with a different material. So, perhaps bungee cords + silicone gel + foam could guard against many of them.

    Test. Test again. If I were you, I would construct a "cradle" for the drive or case. Then, put something in it susceptible to vibration (a covered bowl of water, perhaps, or a leaf). Crank the bass. Have someone else drive around while you look at it. See any ripples or shaking? If so, back to the drawing board! More high-tech solutions exist for testing, etc., but I doubt you want to go there.

    And, when all else fails, drivespace is cheap. Buy several replacement drives.

  • I plan to build a car MP3 player as well, and I don't plan to use a hard disk at all. I'm either going to order a decently sized M-Systems Disk on Chip and use burned CDs for mp3s, or I'm going to just do a 'live CD' type boot, not needing a hard disk. even cooler would be a DVD-RAM burn of mp3s, to get all on one DVD, and an older DVD-ROM in the car. As long as enough ram is present, and the player is configured to buffer or load the song into memory before playing I don't see how this will be a problem. For a board, Amptron makes an integrated video/sound/network monstrosity, and while a horrid thing for desktop computers it would probably work fine in a single-purpose solution. But regardless, using a hard disk can be avoided entirely, and I think should.

  • possible suggestions (Score:1)

    by Anonymous Coward
    I've been thinking of building an car MP3 player myself, and here's what I've planned out so far..

    First, use a laptop drive. They're more expensive, but smaller (less mass to fly around and get scratched up) and built to withstand some shocks and bumps.

    There's a number of different ways to mount it, and I haven't actually researched to see which is best/most effective. You could just put thick soft rubber mounts between the drive itself and the chassis you'll contain it in, which should protect against severe shock fairly well.

    You could also suspend it fron springs on all sides, which (imo) would be the best solution I think. If the total area it can move around in is large, the drive will bounce (softly) after each bump, but not much more than that. This has an advantage of protecting against lesser bumps, while being pretty effective against severe shock as well. The disadvantage is that the chassis to contain the springs + drive would have to be pretty large to have any effect. If the drive compresses a spring fully and "bottoms out", the resulting shock the drive will receive will be pretty bad.

    Vibrations: There isn't much I can suggest other than put the drive _as far away_ from the subs as possible. If you've got subs in the trunk, then that's not the place for the computer. Fit it in the glove box, or under the dash, or something like that. (glove box is my choice)

    Lastly, put as much memory into the computer as you can, and buffer the MP3s there.. keep the drive spun down as much as you can. This will minimize any after effects if the drive does get bumped around. (drives are MUCH less suceptible to shock when powered down)
  • There was a piece on /. a while back on the empeg web site here [empeg.com]. They might be a bit pricy, but they have done what you want to do, and then some. It might be worth while to check it out for ideas.
  • Nah it wont get that cold around here... I live in pennsylvania and the lowest it gets to be around here is like -5dF or so and that only happens once in a long while (plus the car isn't 4wd so i wont really drive it as much in the winter)
  • I read your question about harddrives and bumps and the guy with the panasonic laptop with the harddrive encased in gel. I believe what they are using is a liquid silicone,like I have seen used in the lens assy. on a projection TV, probably an easy salvage place. But not the kind of stuff you'd want to smear all over yourself. Some old stats that I'm familiar with are, A hard drive will withstand 10g's while its running and a 100g's when the platters are stopped.So, if you're pulling 10g's in your car, I don't think I want to ride with you no matter how good the music is.
  • here's what you need to do.... since the majority of the bumps will be vertically... you'll want to have a suspension above and below the hdd... a simple piece of foam would do the trick (soft.. non-polystyrene). you won't want the heads, which are flying above the platters, to hit the platters.. therefore you'll want to mount it with the platters perpendicular to the moments of the forces. So, you mount it sideways, with padding on both top and bottom.. if you were to use padding where the top and bottom are a C shape facing the drive, you shouldn't have a problem with lateral motion. 2 long screws (with something covering the threads down to the drive, so as not to restrict vertical motion) down to the top of the drive.. this will allow vertical motion, and since you'll want to not restrict any lateral motion, you can easily leave the 2 bottom screws out.

    one other problem you'll encounter is heat. what I did for my car MP3 player was had the hdd mounted in a removable enclosure, with the enclosure shock mounted. (stored in that little compartment in between my seats) Since the compartment is quite large..1986 full size blazer, I easily have room for additional drives/enclosures)

    All this can be done for $7 and a trip to a computer show.
  • tell me that spinning up a hard drive when it's been sitting outside in -20dF temperatures overnight will be OK for it....with a straight face.

    You know what I mean, summer/winter blah blah blah, Australia southern hemisphere yadda yadda yadda....

  • I thought about making my own too but then i found the personal jukebox. its a palm-sized device that holds up to 6 gigs and lasts for over 10 hours on its rechargable battery. I love this thing cause i take take it home, car, and work.. i've had it for about a month now with no complaints.. They run about $700 and you can get them at www.thinkgeek.com
  • If you increase the mass of the drive (add weight) or decrease the mounting stiffness (floppyer mounts) you can get the resonant freq. away from the driving freq. of the bass.

    If you are worried about the bass freq exciting components inside the drive (making the heads flutter) then you would need to put the drive in a sealed (air-tight) box which is stiff enough to attenuate the base freq. you are worried about. The drive would have to be isolated with mounts inside this sealed box to avoid coupling the outside bass freq into the drive You could cool the box with a peltier device on the wall of the box, with a little fan on the inside and outside heatsinks of the peltier device.

    In either case, you might want to download the catalog, in pdf format, from Barry Controls, who make a vast range of vibration isolation mounts.

    Picking the right mount is not trivial, but the catalog should provide an engineering section giving you the equations and procedures for a first-order solution.

    In general, the more displacement (range of motion) you can allow for the mount the better off you will be. I have used the wire rope mounts shown on the barry home page (upper right corner) and they have good charactaristics. They were expensive, but you could make a copy with some wire rope from the hardware store and wooden or aluminium end plates.

    http://www.barrymounts.com/

  • Do you actually need to shield the hard disk from bumps. My Laptop seems to survive relatively rough train and car journeys without any difficulty and I suspect you'll need to access the disk a lot less with some decent buffering.
  • The toughest laptop I've ever seen is the Panasonic Toughbook. I've used it for data collection in a very high vibration area. Most other laptops would only last 12 - 18 hours in that environment. This one has been running 2 years.

    The case is machined aluminum and carbon fiber, and the HD is surrounded by a very soft jelly.

    It's the kind of stuff you find in ergonomic wrist and mouse pads, that really thick very soft stuff. A normal HD will survive a drop from about 1m on to concrete, but they claim that theirs will survive a 10m fall.

    Perhaps you could find a couple of these at a used computer store and salvage the gel out of them?

  • I agree with clare-ents. I have an Iopener that with a 2GB laptop drive. I had to literally squeeze the harddrive as I pushed and screwed the case closed. I carry the Iopener back and forth all of the time to class, to the office, and home and nothing has ever happened to the drive.

  • but, why not one of those padded CD-PLAYER carrying cases? They're pretty well padded and if secured properly they should offer some good support. Another suggestion could be packaging popcorn (foam stuff) filled up in a small insulated cooler (lunch box type). Drill holes for cables in the side and seal it. It might lessen the temperature extreme while protecting it against bumps and bruises.

  • Check out:
    http://www.linux-hacker.net/tivo/tivo.html

    I don't know what these are like, but the original TIVO bracket has 4 low-end shock absorbers on its mounting bracket.. that combined with some foam would prob. be in the area of what you are looking for. I have done a few things with car mount stuff and found a good source for foam is the stuff they pack retail hard drives in.

    Hope this helps..
  • Check out this site MP3Mobile [chaos.org.uk]. This guy built a in-dash MP3 player and has the steps and material he used. And I believe he is working on making a commercial version of it available. You should be some good ideas from this site on how to build the player.

  • I don't know whether Linux can do this, but if you're running a MS OS such as DOS or Win9X, you could set up a virtual drive in RAM, and copy over a number of MP3s before playing them, then set the hard drive spindown time to some low value (5 min?)

    If it were up to me, I'd just go for a 128MB DIMM, and do that.
  • I would also be concerned about low temperatures, like when your car sits idle for long periods in the winter. The drive may not spin up if it is too cold.
  • only 128mb?.. why bother, a cd player with anti-skip would work. :) get like 2 256mb chips or better yet, you could try and float the HD in a liquid of sorts, just make sure to have a good seal.

    - eViL aSe

  • I don't think you'd have to worry about vibrations so much as it surviving temperature extremes.

    Even if you stick it in the trunk, it's still going to get *damn* hot in the summer. Depending on where you live, winter is liable to kill it altogether!!!

    Unless you somehow put it in a pullout chassis you can take out of the car and into the ac or heat.
  • Use a tape drive and then cahce the next 10 or so songs to be played into a ramdrive. I would think that tapes would be less proned to being damaged by vibrations.

  • Re:What about temperature extremes? (Score:3)

    by djweis ( 4792 ) on Tuesday September 12, 2000 @08:57AM (#785539) Homepage
    I don't worry too much about vibration for mine. I have it in a case in my trunk. Once my dsl comes back up, you can see it here [sjdjweis.com].
  • Depending on where you live, winter is liable to kill it altogether!!!

    That is, if you live in Australia. However, here in the Northern Hemisphere, the winter is cold. And cold is good for electronics, not bad.

  • Your first step is to identify your vibrational modes. For example:
    • Subwoofer: Assume that you will be protecting against 10 Hz to perhaps 100 Hz
    • Random shocks: No guess as to the frequency of these.
    • Figuring out the direction of these vibrations is important. Will they be going from side to side? Up and down? Front to back?
    Some of that isn't necessary; you know that the major shocks will be from below (suspension bottoming out), and the heaviest low-frequency vibrations will likely be from the subwoofer (unless you have a REALLY loud exhaust or horrible engine mounts). All you really need to do is build your isolation mount, bolt it to something like a piece of heavy plywood, and test it.

    How do you test it? Give it vibrations and shocks. If it can sit on top of your subwoofer without causing any errors, and if you can handle several G's of shock load from below (like you'd get from hitting the far side of a really bad pothole, after the car has had a chance to fall down into it), it should do. The shock-load testing can probably be done with a drop test.

    The really interesting part is the suspension design. Your side loads will probably never get up to 1 G, so the mount can be very compliant in that direction. Ditto fore/aft, unless you make a habit of running into things with your car. A compliant mount will have a very low resonant frequency, and will transmit very little force from the vehicle to the drive. From below is different; you need to handle a constant 1G force and possibly spikes of 5G for short intervals (a few inches of travel) without bottoming out and shocking the drive. You probably want to use foam rubber for this. Make it in blocks separated slightly, so they can bend back and forth more easily than they crush. Use enough thickness of sufficiently stiff foam that 10 G's (ten times the drive weight) doesn't crush the foam all the way down, and make sure that turning the mount sideways (1 G side force) doesn't let the drive hit any of the sides either. Don't forget cooling requirements, and a heater to bring the drive up to a reasonable temperature before firing it up after a cold-soak is a really good idea.

    I like the idea of the auto-spec CD-ROM drive; all those details are already taken care of for you.
    --
    Build a man a fire, and he's warm for a day.

  • How would you boot off a tape drive? I've never seen this trick. Also wouldn't it take 5-10 min and a lot of noise to get it all set up? (Maybe I'm living in the past here, I don't do anything with tape drives.)

    Either way, I'm thinking a car player drive shouldn't be worth much. Maybe just get an old 4GB or something.
  • Yes booting off of a tape would be slow. I would suggest a cd or maybe zip in it's place, to boot off of, or maybe a small HD.
  • Suspending with string from above won't help you at all. There is nothing in a string that will absorb any energy. When the car hits a bump and goes up, the string will jerk the HD up, etc.

    If you want to go with springs, suspend it from above and below with springs (and perhaps side to side and front to back). Just make sure they have the proper spring constants so that every little bump doesn't keep it bouncing for ever and ever (that's why you need something to damp out the energy, which is why you use shock absorbers in a car). With all the trouble that is, you might as well just get the proper foam rubber to do the job.

  • At used computer places you can find half gig drives for under 10 bucks. At that price you can just run some long wires and just keep the drive on the passenger floormat without a case!

  • Cold isn't good for motors, lubricants and bearings.
  • Ok folks, this USED to me my field of work (and I can't remember some of the source names)

    If you can, try making a phone call to an "Environmental Test Lab" - they do shock and vibration testing. I've tested a few HDs over time

    Vibration is going to be FAIRLY easy to deal with, IF you get lucky. There are little rubber (actually synthetic) shock mounts made - in fact, you'll see small ones on a lot of drives - the problem is I can't remember the main brand name (I haven't done this in 8 years). Your BIG worry is that the mount (ANY mount) has a resonant frequency, where it will actually amplify the input vibration. What you have to worry about is that the resonant frequency you choose for your mount can't be near any of the resonant frequencies of the drive itself.

    The hard problem is SHOCK - this is usually isolated with what looks like a coil of wire (like a spring) laying on its side. This takes some space, but can work well (if you get the response frequencies right).

    From watching disk drives being tested in the past (Yes, I've played with mil spec hardened drives - 200g shock? No problems - 30 gs of vibration? Cake), the BIGGEST problem is not shock (or vibration) in the X,Y or Z directions (aka, left/right, front/back,up/down), but it's TORTIONAL shock, aka, rotating about the X,Y or Z, and in particular, rotating around the axis of the spindle - this tends to drive the ends of the head arms into/out of the track.

    I hope this helps
  • The following company's catalog features a few products designed just for shock mounting hard drives.

    PS Solutions
    411 Interchange
    McKinney, Texas 75069
    Tel: (972) 548-8080

    I see two products made specifically for 3.5" drives. Both let you mount a 3.5" drive in a 5.25" bay and are specifically made to absorb and distribute shock.

    The first product is a thick rubber rail. Two rubber rails screw into each side of the 3.5" drive. The rubber rails are then screwed into a 5.25" bay. Part #MS-NFP-XTR

    The second product is a metal chassis that fits into a 5.25" bay, but another 3.5" chassis floats inside it. The 3.5" chassis is connected to the 5.25" chassis by some sort of suspension system. There could be metal and rubber in there. I can't tell from the picture. Part #SHK-MT-K

    One problem is I don't see any prices, they may only sell to big distributors. I got their catalog at the PC Expo in NYC this summer.
  • I've had a mp3 player in my car for the last two years with the same HDD and haven't had a problem yet. Like what was said before, the temperature is something you should be more worried about.

    Gutter
    http://impee3.hypermart.net [hypermart.net]

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