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Thread ID: 21104	2002-06-18 08:25:00	REALLY Fast HDDs - An interesting thought.	Guest (0)	Press F1

Post ID	Timestamp	Content	User
54974	2002-06-18 08:25:00	Hi, Have you ever noticed that the really fast HDDs (10Krpm and 15Krpm) have a very limited size. For example, the biggest 15Krpm drives are FAR FAR smaller than the biggest 5400 & 7200rpm varieties. I can buy/sell 160GB 5400rpm drives, and 120GB 7200rpm drives. I can also buy/sell 36GB 10Krpm drives, and 18GB 15Krpm drives... I recently discovered that the reason for this is that when a drive is spinning that fast, the outside edge of the drive becomes at risk of tearing off from the high centripetal forces imposed on it. Thus, on a 15Krpm drive the outer edge of the disks are only a few cm from the spindle. This decreases the force on it, as well as increasing the relative amount of 'stuff' holding it to the spindle. This small size acounts for the reason that these drives are smaller in capacity... Tricky eh? :) Erin	Guest (0)
54975	2002-06-18 23:07:00	Centripetal force acts towards the axis of rotation and will not tear anything off - it will tend to squash it. You obviously mean it's opposite, centrifugal force, which acts outwards from the axis of rotation.	Guest (0)
54976	2002-06-19 00:01:00	bearings and vibration would be biggest problem. at high speeds the loads on the bearings are huge. it also generates lots of HEAT. if the bearings ware out a bit the platters can move hitting the heads destroying the expensive drive. a lot of people forget that heat is a big killer of hardrives. watch those case temps (erin!....carefull on the product pimping there young man ;-)	Guest (0)
54977	2002-06-19 05:36:00	Sorry Tweak'e... Yes, centrifugal force, but also centripetal... Both are reasons to shrink the disks. Smaller disks also result in shorter seek times (for obvious reasons) :) Erin	Guest (0)
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