Mounting HDD's in an in-car mp3 player

Hi All,

I'm trying to build an in-car mp3 player, based around a module bought from the internet, so far so good however I'm a little stuck on mounting the hard disc. I'm looking to use a laptop drive (better shock characteristics & lower power consumption, etc.) but can't quite figure out which angle to mount it at. Originally I thought vertically (bumps in the road cause the heads to skip, but shouldn't result in a head crash), secured to the case using a frame and 4 rubber dampers. However looking at the RIO unit, the drives seem to be mounted how I would do it, but horizontally. Is this a wise way to mount my drives (bearing in mind space is at a premium and I do a fair bit of driving on country roads!). How will the drive react to be being bounced up & down? Also what sort of shock ratings (in G) should I be looking for? I appreciate this isn't related to a specific player, but as there seems to be a wealth of knowledge here thought I'd give it a go :-) . Many thanks

Only a handful of people here have ever reported disk failure, and I don't recall any of those ever being definitely attributed to shock trauma. Statistically speaking, the empeg orientation works well. When you also consider that laptop drives are usually mounted horizontally in laptops, you also have to wonder whether the drive manufacturers take that into consideration when designing them to withstand g-forces.

I think that with rubber mounts and a laptop drive, you have probably cracked the problem though. If I were in your position I would probably mount the drive in whichever orientation worked the best in the space.

What module are you using out of curiousity? Even though I have an empeg, I've always liked the DIY approach for some reason..

However looking at the RIO unit, the drives seem to be mounted how I would do it, but horizontally. Is this a wise way to mount my drives

The proper way to mount laptop drives is so that they lie flat, label side up, when operating. If you put them up on edge, or on end, or upside down, the spindle bearing of the drive is operating in a position that it wasn't designed to operate in. It will work, but the drive won't last as long as if you'd mounted it flat.

There are even more important things to consider than just the mounting angle. The empeg takes all of these into account. These are:

- Drives get spun-down when not in use.
- Agressive RAM caching of the data from the drives reduces the time they're in operation.
- Drives are mounted read-only.

All of the things above mean that the heads spend most of their time "parked", so that the disk drives are not suceptible to damage from vibration. The empeg does all of these quite agressively, meaning that they've done the best possible job at car-proofing the drives.

One other thing the empeg does to protect the drives is:

- Pull the unit out of the car and take it inside with you.

This keeps the drives from getting exposed to extreme temperatures.

So... Can your homemade module do all of these things? You know, there's empegs for sale on ebay...

By the way, answers to some of your other questions can be found in the FAQ entries here, here, and here.

- Pull the unit out of the car and take it inside with you.

This keeps the drives from getting exposed to extreme temperatures.

...and it also keeps them from being exposed to thieves. Even a fully operational drive isn't of much use when it's been stolen, along with the empeg it's installed in.

The unit is available from http://www.dontronics.com/kitstream.html

Ya i've run across that unit before, interested to know how well it works. It's a good alternative for folks who can't afford a $500 empeg. These are just $81 + hard drive+ a little leg work.

Yeah I've been there with the homebrew one inspired by Hugo's original one about 4 years ago. I had a 3.5" drive mounted horizontally (label up) without any major troubles. I had some minor shock absorption.

First drive was a 6.4Gb Quantum Fireball and I used it for about 1 year with absolutely no trouble. It's still running today in my firewall.

Second drive was a 30Gb Samsung. It developed a few bad sectors after a while and finally died after about 1 year of use in the car and 1 year in a home PC.

Edit: And I never bothered with any code to spin the drives down either. That was my biggest problem - the PSU could only just supply enough +12V current to spin up the drives so I kept them spinning all the time.

YMMV