Hard Drive Orientation in a Car [LONG POST]

["Keith Doxey" <ukha@xxxxxxx>]

Hi All,

Apologies for the long post but I have spent ages thinking about
this...

I have a question about the best orientation of a hard drive to
provide maximum protection when mounted in a car.

Having never disassembled a hard drive I am looking for answers from
someone more destructive than me :-)

Do all hard drives generally tend to have the same physical layout
with regard to the pivoting of the head arm.

To explain that better I will use a record deck as an analogy...
generally most turntables have the tone arm pivoted from the rear
right corner of the chassis with the arm extending towards front
right. ( I wont say always because someone here will have an esoteric
turntable with some wierd arrangement!) The turntable would be far
less susceptable to movement front to rear than is would from left to
right as this would cause the arm to skip across the disc. Any
vertical movement would cause the arm to bounce.

What I am trying to do is minimise the effects of external motion on
the disc drive itself. I plan to mount the drive in an extruded
aluminium case which will give it mechanical protection and an air
space around it. There will be a small fan to ensure a continuous air
flow through this case to keep the temperature down. The case will
then be packed in foam to isolate it from the main chassis of the
computer case.

There are 4 main sources of movement that could affect the drive.

1. Acceleration - not too much of a problem with my car!!!
2. Deceleration - Emergency braking can cause severe sustained forces.
3. Cornering - Sustained but not violent forces to left or right.
4. Bumps - Far more likely to cause damage due to the sudden and
violent nature.

I once had a Car Radio/Cassette player that was damaged when I hit a
pothole. The force was so severe that the flywheel pushed one of its
mounting bushes out of its housing :-(

As I see it there are 12 possible ways to mount the drive in relation
to the front of the car.

1.  Horizontally - Connectors Front
2.  Horizontally - Connectors Rear
3.  Horizontally - Connectors Left
4.  Horizontally - Connectors Right

5.  Vertically - Front to Rear - Connectors Front
6.  Vertically - Front to Rear - Connectors Rear
7.  Vertically - Front to Rear - Connectors Top
8.  Vertically - Front to Rear - Connectors Bottom

9.  Vertically - Across Vehicle - Connectors Left
10. Vertically - Across Vehicle - Connectors Right
11. Vertically - Across Vehicle - Connectors Top
12. Vertically - Across Vehicle - Connectors Bottom

The Vertical methods seem to be preferable to me as the most severe
impact would be from bumps in the road which for a horizontally
mounted drive could cause the heads to impact the surface of the disc.

I am thinking Vertical - Front to rear would be best as the second
strongest force - braking - would be directed across the disc, and
the least force, cornering, would be the one that would affect the
head/disc clearance.

Is it better for the braking forces to push the heads towards the
centre or outside of the disk ?

What happens if the heads get displaced ?
Does the PC just find the right place and resume like a walkman with
AntiSkip or does it just crash ?

Are there physical stops within the drive to prevent the heads
falling off the disk or hitting the centre ?

Thoughts on the best option gratefully received

Thanks

Keith