10 Oct
2011
10 Oct
'11
3:10 p.m.
Has anyone attempted to do so or has disassembled the
disk enclosure?
I would like to know if the heads are parked on or off the disks.
I've taken apart HDA's from crashed Eagles, with no hope of ever putting back
together.
The heads are parked in the landing zones on the disk.
An Eagle is a little more complicated than a "typlcal" drive in that each
surface has two heads - one covers the inner half, the other covers the outer half. I
don't think this head arrangement is unique to the Eagle but it's not all that
common.
At least one of the bearings (the bottom one) is in fact out of the HDA isn't it? On
the top center of the HDA there's some sort of cover plate and I bet the top bearing
is underneath it. Some might count that as "inside the HDA" but I count it as
"on the outside and secured by a cover plate".
Not that I've ever done a bearing replacement on an HDA quite like this. On removable
pack drives, sure (RL01/02, RK05, etc) but obviously the pack was out :-).
I would think you could locate a working HDA without a lot of difficulty.
10 Oct
10 Oct
3:29 p.m.
On Mon, 10 Oct 2011, Shoppa, Tim wrote:
An Eagle is a little more complicated than a
"typlcal" drive in that
each surface has two heads - one covers the inner half, the other covers
the outer half. I don't think this head arrangement is unique to the
Eagle but it's not all that common.
ST225 !!
Since the HDA is opaque, it's much less unique than people realize.
Generally, the computer "sees" that as two surfaces.
If you compile statistics, the inner "surface" has demonstrably less
reliability that the outer "surface", but that shows up as "even/odd"
heads.
--
Grumpy Ol' Fred cisin at xenosoft.com
4:34 p.m.
Date: Mon, 10 Oct 2011 15:29:43 -0700
From: cisin at xenosoft.com
To: cctalk at classiccmp.org
Subject: Re: Fuji Eagle Bearing Replacement
On Mon, 10 Oct 2011, Shoppa, Tim wrote:
An Eagle is a little more complicated than a
"typlcal" drive in that
each surface has two heads - one covers the inner half, the other covers
the outer half. I don't think this head arrangement is unique to the
Eagle but it's not all that common.
ST225 !!
Since the HDA is opaque, it's much less unique than people realize.
Generally, the computer "sees" that as two surfaces.
If you compile statistics, the inner "surface" has demonstrably less
reliability that the outer "surface", but that shows up as
"even/odd"
heads.
--
Grumpy Ol' Fred cisin at xenosoft.com 
3:40 p.m.
The structure of the units I am referring to is that there was a bearing
structure on the bottom carrier plate of aluminum. maybe two bearings.
The top was a clear-ish plastic cover. The ones we had in the 1980 time
frame were like this anyway. They were not metal cover on metal carrier
plate, with the substance to have a bearing on the top and the bottom of
the axis. Such probably could be repaired like a differential w/o
popping the seal if it were designed right, though I'm no expert on that.
Jim
On 10/10/2011 3:10 PM, Shoppa, Tim wrote:
Has anyone
attempted to do so or has disassembled the disk enclosure?
I would like to know if the heads are parked on or off the disks.
I've taken
apart HDA's from crashed Eagles, with no hope of ever putting back together.
The heads are parked in the landing zones on the disk.
An Eagle is a little more complicated than a "typlcal" drive in that each
surface has two heads - one covers the inner half, the other covers the outer half. I
don't think this head arrangement is unique to the Eagle but it's not all that
common.
At least one of the bearings (the bottom one) is in fact out of the HDA isn't it? On
the top center of the HDA there's some sort of cover plate and I bet the top bearing
is underneath it. Some might count that as "inside the HDA" but I count it as
"on the outside and secured by a cover plate".
Not that I've ever done a bearing replacement on an HDA quite like this. On removable
pack drives, sure (RL01/02, RK05, etc) but obviously the pack was out :-).
I would think you could locate a working HDA without a lot of difficulty.
11 Oct
11 Oct
11:38 a.m.
At least one of the bearings (the bottom one) is in fact out of the
HDA isn't it? On the top center of the HDA there's some sort of cover
plate and I bet the top bearing is underneath it. Some might count that
as "inside the HDA" but I count it as "on the outside and secured by a
cover plate".
There are bearing pullers that will remove a bearing like that without
having to pull the shaft first. Typically you drill away the ball cage and
the puller ends then hook into the tracks in both the inner and outer
races. But I suspect there's no seal under the bearnin in this HDA, so
removing it will allow dust in, not to mention the swarf from drilling
the cage. And the forces involved in remove the old bearing and fitting
the new one may well case the shaft to move enough to damage heads/platters.
Not that I've ever done a bearing replacement on an HDA quite like
this. On removable pack drives, sure (RL01/02, RK05, etc) but obviously
the pack was out :-).
If oyyu mean you replaced the spidle assembly with the DEC spare parts,
then been there, done that. If you actually took the spindle apart and
replaced the bearings, I'd be interested to know how. For one thing all
the parts are pressed together (no grub screws or anything), I suspect
you need a large hydraulic press to do it. And for another there are
ferrofluid seals on these spindles IIRC, how did you cope with that?
-tony
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