6 Sep
2016
6 Sep
'16
8:48 a.m.
So I have a fairly large group of 16-sector RK05 packs (i.e. PDP-8, -12) which
I have no use for, which I would like to trade for 12-sector RK05 packs (i.e.
PDP-11). Anyone have any of the latter, and need the former?
Alternatively, if anyone has any head-crashed 12-sector RK05 packs, I would be
interested in buying them (or trading something else) for them. (I am reliably
informed that one can replace the platter on an RK05 pack without too much
work, so I'd transplant the 12-sector hubs into the packs I already have).
(Replies to me, please, not the whole list - unless there's some point you
wish to make which would be of general interest.)
Noel
6 Sep
6 Sep
8:53 a.m.
I'd be willing to trade two or three, to have some of the 8 sort.
Sent from my iPad
On Sep 6, 2016, at 10:48, Noel Chiappa <jnc at
mercury.lcs.mit.edu> wrote:
So I have a fairly large group of 16-sector RK05 packs (i.e. PDP-8, -12) which
I have no use for, which I would like to trade for 12-sector RK05 packs (i.e.
PDP-11). Anyone have any of the latter, and need the former?
Alternatively, if anyone has any head-crashed 12-sector RK05 packs, I would be
interested in buying them (or trading something else) for them. (I am reliably
informed that one can replace the platter on an RK05 pack without too much
work, so I'd transplant the 12-sector hubs into the packs I already have).
(Replies to me, please, not the whole list - unless there's some point you
wish to make which would be of general interest.)
Noel
8:58 a.m.
I'd like to trade two media.
Am 06.09.2016 um 17:48 schrieb Noel Chiappa <jnc at
mercury.lcs.mit.edu>:
So I have a fairly large group of 16-sector RK05 packs (i.e. PDP-8, -12) which
I have no use for, which I would like to trade for 12-sector RK05 packs (i.e.
PDP-11). Anyone have any of the latter, and need the former?
Alternatively, if anyone has any head-crashed 12-sector RK05 packs, I would be
interested in buying them (or trading something else) for them. (I am reliably
informed that one can replace the platter on an RK05 pack without too much
work, so I'd transplant the 12-sector hubs into the packs I already have).
(Replies to me, please, not the whole list - unless there's some point you
wish to make which would be of general interest.)
Noel
9:11 a.m.
It seems to me that one possible solution would be to whip up a PLL in a
CPLD or FPGA to generate 12 sector timing from a 16 sector pack or vice
versa.
On Tue, Sep 6, 2016 at 8:58 AM, <aswood at t-online.de> wrote:
I'd like to trade two media.
Am 06.09.2016 um 17:48 schrieb Noel Chiappa
<jnc at mercury.lcs.mit.edu>:
So I have a fairly large group of 16-sector RK05 packs (i.e. PDP-8, -12)
which
I have no use for, which I would like to trade
for 12-sector RK05 packs
(i.e.
PDP-11). Anyone have any of the latter, and need
the former?
Alternatively, if anyone has any head-crashed 12-sector RK05 packs, I
would be
interested in buying them (or trading something
else) for them. (I am
reliably
informed that one can replace the platter on an
RK05 pack without too
much
work, so I'd transplant the 12-sector hubs
into the packs I already
have).
(Replies to me, please, not the whole list - unless there's some point
you
wish to make which would be of general
interest.)
Noel
10:58 p.m.
On Tue, Sep 6, 2016 at 12:11 PM, Marc Howard <cramcram at gmail.com> wrote:
It seems to me that one possible solution would be to
whip up a PLL in a
CPLD or FPGA to generate 12 sector timing from a 16 sector pack or vice
versa.
This is one of the recurring conversations here - 12-sector packs are
abundant compared to 16-sector packs, and the only difference is the
slits in the hub and the consequent formatting on the matching
controller...
-ethan
11:51 p.m.
On Wed, Sep 07, 2016 at 01:58:24AM -0400, Ethan Dicks wrote:
On Tue, Sep 6, 2016 at 12:11 PM, Marc Howard
<cramcram at gmail.com> wrote:
I do recall discussion of manufacturing new hubs but not the outcome. I
imagine that someone with access to a lathe and mill would be able to
make new hubs with good enough tolerances.
Is there some caveat to doing this (besides finding someone with a lathe
and mill?)
/P
It seems to me that one possible solution would
be to whip up a PLL in a
CPLD or FPGA to generate 12 sector timing from a 16 sector pack or vice
versa.
This is one of the recurring conversations here - 12-sector packs are
abundant compared to 16-sector packs, and the only difference is the
slits in the hub and the consequent formatting on the matching
controller...
-ethan 
7 Sep
7 Sep
8:54 a.m.
On Sep 7, 2016, at 2:51 AM, Pontus Pihlgren <pontus
at Update.UU.SE> wrote:
On Wed, Sep 07, 2016 at 01:58:24AM -0400, Ethan Dicks wrote:
As one who has a (quite old) lathe and some limited skills in using it, I'd offer
some.
You can't make something without having accurate specs -- engineering drawings or
equivalent. The sector mark ring isn't too terribly criticall, but the hub mating
surfaces for the spindle are. One question would be what the required tolerances are, and
what the required surface finish is. Depending on those, the job may be straightforward
for a basement machine shop like mine, or they may require more than average skill and/or
a high end CNC machine. If the finish or tolerance requirements are sufficiently tight,
the job might require grinding, which raises the difficulty to a whole new level.
The other question is the disassembly of the pack and the installation of the new hub.
How is that done? What are the concentricity requirements for the platter? Is there a
mating surface (exterior cylinder surface on the hub) or are platter and hub aligned in
some fixture and then clamped to hold the platter in position? Clearly the pack would be
reformatted, so a small amount of runout would be ok, but it would have to be small enough
that the vibration is controlled.
paul
On Tue, Sep 6, 2016 at 12:11 PM, Marc Howard
<cramcram at gmail.com> wrote:
I do recall discussion of manufacturing new hubs but not the outcome. I
imagine that someone with access to a lathe and mill would be able to
make new hubs with good enough tolerances.
Is there some caveat to doing this (besides finding someone with a lathe
and mill?) It seems to me that one possible solution would
be to whip up a PLL in a
CPLD or FPGA to generate 12 sector timing from a 16 sector pack or vice
versa.
This is one of the recurring conversations here - 12-sector packs are
abundant compared to 16-sector packs, and the only difference is the
slits in the hub and the consequent formatting on the matching
controller...
-ethan 
8:56 a.m.
The other question is the disassembly of the pack and
the installation
of the new hub. How is that done? What are the concentricity
requirements for the platter? Is there a mating surface (exterior cylinder
surface on the hub) or are platter and hub aligned in some fixture and
then clamped to hold the platter in position? Clearly the pack would be
reformatted, so a small amount of runout would be ok, but it would have
to be small enough that the vibration is controlled.
I looked into this a couple of years ago with the intention of making
a 24 sector pack for an HP7900 (actually part of an HP9880). Starting
from a 12 sector pack of course.
This project got interupted by a house move and I've not gone back
to it yet, but I did discover there is no alignment ridge or anything
between the hub and platter. The platter fits on the flat top of the
hub, there is a clamping ring that is then screwed down to anchor
it.
My intention was to put the hub on a spare spindle (I happen to
have a load of RK05 drive spares), put the platter on, turn it round
by hand and use a lever-type dial gauge to get minimum run-out.
-tony
paul
9:17 a.m.
On Sep 7, 2016, at 11:56 AM, tony duell <ard at
p850ug1.demon.co.uk> wrote:
Did you construct an engineering drawing of the hub based on your observations?
The other question is the disassembly of the pack
and the installation
of the new hub. How is that done? What are the concentricity
requirements for the platter? Is there a mating surface (exterior cylinder
surface on the hub) or are platter and hub aligned in some fixture and
then clamped to hold the platter in position? Clearly the pack would be
reformatted, so a small amount of runout would be ok, but it would have
to be small enough that the vibration is controlled.
I looked into this a couple of years ago with the intention of making
a 24 sector pack for an HP7900 (actually part of an HP9880). Starting
from a 12 sector pack of course.
This project got interupted by a house move and I've not gone back
to it yet, but I did discover there is no alignment ridge or anything
between the hub and platter. The platter fits on the flat top of the
hub, there is a clamping ring that is then screwed down to anchor
it. My intention was to put the hub on a spare spindle (I
happen to
have a load of RK05 drive spares), put the platter on, turn it round
by hand and use a lever-type dial gauge to get minimum run-out.
That's like the procedure for centering a work piece in a 4-jaw chuck. With care and
patience you can get it centered to .001 inches (25 um), give or take. Another option
would be to make a centering jig, one that holds the hub and platter. If the outer
diameter of the platter is held to tight tolerances that would work well; if that
dimension is not tightly controlled then centering with an indicator gauge will work
better.
With a spare spindle like that, you'd also be able to verify the balance afterwards,
by spinning up the finished platter and checking the vibration level.
paul
10:40 a.m.
I looked into
this a couple of years ago with the intention of making
a 24 sector pack for an HP7900 (actually part of an HP9880). Starting
from a 12 sector pack of course.
This project got interupted by a house move and I've not gone back
to it yet, but I did discover there is no alignment ridge or anything
between the hub and platter. The platter fits on the flat top of the
hub, there is a clamping ring that is then screwed down to anchor
it.
Did you construct an engineering drawing of the hub based on your observations? My intention
was to put the hub on a spare spindle (I happen to
have a load of RK05 drive spares), put the platter on, turn it round
by hand and use a lever-type dial gauge to get minimum run-out.
That's like the procedure for centering a work piece in a 4-jaw chuck. With care and patience you can get it centered to .001
inches (25 um),
And as you said the only real requirment is to get it balanced to avoid
vibration. I think a 1 thou runout would be good enough for that. Of
course the disk would have to be formatted after this modification
but that's not a problem.
In fact for my application (the HP9880) it may not be necessary. After
battling through manuals and microcode, I have realised that the
thing actually treats it as a _12_ sector pack, starting a read or
write on alternate notches only. That means an electronic modification
(easier for me) would let you use normal 12 sector packs that I
have over a hundred of....
-tony
3028
days inactive
3029
days old
9 comments
8 participants
participants (8)
-
ard＠p850ug1.demon.co.uk -
aswood＠t-online.de -
cramcram＠gmail.com -
cube1＠charter.net -
ethan.dicks＠gmail.com -
jnc＠mercury.lcs.mit.edu -
paulkoning＠comcast.net -
pontus＠Update.UU.SE