🚀 go-pugleaf

In article: <jhrPXAAIpqfxEwD+@helix.demon.co.uk>  Mike Clarke <mike@helix.demon.co.uk> writes:
> In article <MBXaIDA+hjfxEwVq@hmsl-group.co.uk>, "Max D. Wilkinson"
> <Max@hmsl-group.co.uk> writes:
> 
> >In article <830301092snz@myth.demon.co.uk>, Mike <zeus@myth.demon.co.uk>
> >writes
> >>Could it be the infamous 'stiction'? The grease on the internal drive
> >>bearings thins and causes the motor to stall. Give it a careful tap on the
> >>bearing if you can. You could always try another power lead too.
> >NO. Never tap a HD, unless you like the head bouncing on the platter. To
> >cure stiction spin/rotate, wrist action as if turning a screw top
> >quickly, to turn disk inside case.
> 
> I've generally found your suggested method of dealing with stiction to
> be more effective than tapping the drive (provided you give a really
> sharp twist) but you're being a bit over cautious with the warnings.
> 
> Kid glove treatment was needed back in the Good Old Days when disks were
> the size of washing machines, and shufled across the floor as the heads
> moved. Modern disks are much more robust than most people assume, for
> example Seagate quote a maximum operational shock of 10G and a non
> operational limit of 75G for their Medalist range. That's more than the
> human body can stand.
This is not true. The human body, can take _massive_ momentary shocks,
it is continuous 'G' loadings, at this high level, that can't be taken. It is
suprising how _small_ a knock can be, and yet give 'G' loadings well
above this sort of figure. Drop a disk, even 1", onto a solid surface, such as
a stone floor, without the small rubber shock absorbers hidden in the
mounts, and 'G' forces can be >>2-300G. Drop the same disk 10' onto
a carpeted wooden floor, and instantaneous G forces, will be very much
lower. It is suprising, to realise, that if you tow an aircraft, with a 'G' recording
system fitted behind a motor car, figures of 20-30 G, can routinely be
recorded on the public road. I _still_ occasionally see drives destroyed
by something like a vacuum cleaner hitting a tower case, and can confirm,
from fitting 'G' rupture detectors to such machines, that shocks over
100G have occured in such cases. Conversely, I have seen a drive
dropped down a staircase, and going 'bump bump bump down the stairs',
which did not trip such a rupture detector. It survived. 'G' is 'rate of change'
of velocity, and small velocities, can produce suprisingly high figures,
if hard surfaces are involved. 

> 
> Having seen a disk drive survive falling of a desk these thoughts are
> based on experience as well as the specs.
I suspect that your floor was carpeted, and probably a timber suspended
floor as well.

Best Wishes.

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