Stiction

[Bob Bradlee]

The problems i saw were with old drives that ran 24/7 and were shut down to be moved to a new location.

The problem occured when they cooled down. Once warmed back up, they could be powered down and back up 
as long as they did not cool down again. 

These were systems that had 30k -> 50k+ hours on them in 24/7 operation.
I always figured it was bearings or bearing related lub problems. I have lost track of the number of cheep power 
supply and cpu fans that required a spin to get start again after they had cooled down.

In the late 90's the cheep cpu fans they were putting in clones would last between 15k -> 20k hours. Changing 
fans kept some small service shops in business for several years around the turn of the century.

I had never thought of the platters and heads being a cause of stiction.

In a crude attempt to put things back on topic :-)
My friend David had a stiction problem last year on a 3344 disk pack running on an IBM System 3. The head 
retracted to park and stuck to a very old and very soft rubber home stop. It did not release and come ready untill 
pushed from behind with a stick, via the inspection hole, to get it moveing again.

Stiction comes in many forms from numerious reasons .....

Just some random thoughts
Bob Bradlee



On Sat, 09 Dec 2006 07:11:25 -0800, dwight elvey wrote:




>>From: "Bob Bradlee" <caveguy at sbcglobal.net>
>>
>>Stiction is mostly caused by a breakdown in the lubricant.
>>
>>Over simplified, oil turns to varnish or tar.
>>

>Hi
>I have several friends that worked at Seagate when they had
>problems of stiction. It was not a lubricant problem. It was
>caused by the surfaces being too smooth. When to really
>smooth surfaces sit together for a long time, the air is squeezed
>out. Once the surfaces really touch, there is a thing called
>molecular adhesion.
>Anyone that has worked with guage blocks is familair with
>this.
>Seagate fixed the problem by roughing the surfaces enough
>so that they didn't quite sqeeze out enough air to adhere.
>The surfaces are lubed but not with petrolium greases
>so they don't break down to tars. As I recall, they used some
>type of synthetic oil and only in tiny amounts. It was just
>to keep the surfaces apart while it spun up. After that,
>the head was flying and no longer made contact.
>Dwight

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