4 Mar
2014
4 Mar
'14
10:12 a.m.
I've seen rumours that you can convert a PDP-11 RK05 disk into a PDP-8
style by swapping out the sector hub on the bottom.
Is this:
1. True, I've done it, or,
2 It oughta work, or,
3 No way.
Thanks,
Marc
4 Mar
4 Mar
11:15 a.m.
On 3/4/14 10:12 AM, Marc Howard wrote:
I've seen rumours that you can convert a PDP-11
RK05 disk into a PDP-8
style by swapping out the sector hub on the bottom.
2 It oughta work, or,
You should be able to make a 16 sector ring. Disassembling and getting a pack
rebalanced on the hub is the challenge.
I don't know of anyone other than pack rebuilding companies that have done this
in the past 15 years, and I think Farris Associates are the last guys standing.
Crisis Computer isn't doing it any more.
1:10 p.m.
Good point. Do you have a web address for Farris Associates? All the
google hits point to HR firms, etc.
Marc
On Tue, Mar 4, 2014 at 11:15 AM, Al Kossow <aek at bitsavers.org> wrote:
On 3/4/14 10:12 AM, Marc Howard wrote:
You should be able to make a 16 sector ring. Disassembling and getting a
pack
rebalanced on the hub is the challenge.
I don't know of anyone other than pack rebuilding companies that have done
this
in the past 15 years, and I think Farris Associates are the last guys
standing.
Crisis Computer isn't doing it any more.
I've seen rumours that you can convert a
PDP-11 RK05 disk into a PDP-8
style by swapping out the sector hub on the bottom.
2 It oughta work, or,
1:55 p.m.
On 3/4/14 1:10 PM, Marc Howard wrote:
Good point. Do you have a web address for Farris
Associates?
http://www.mfarris.com/
2:14 p.m.
I've seen rumours that you can convert a PDP-11 RK05 disk into a PDP-8
style by swapping out the sector hub on the bottom.
Is this:
1. True, I've done it, or,
2 It oughta work, or,
3 No way.
Apart from screws, an RK)5 pack seems to consist of :
Upper Housing
Lower Housing
Hub
Magnetic plate on bottom of hub to lock to the drive spindle
Magnetic Disk
Clamp plate to fix the disk to the hub
A bloc kfo foam i nthe middle of the hub :-)
AFAIk, and everythign I have check confirms this, the difference is the
hub only. The PDP11 hub has 12 sector notches (13 nothces total), the
PDP8 one ahs 16 sector notches (17 total). The ring wit the sector
notches in it is integral with the rest of the hub.
In theory you can swap the hubs over. But be warned the disk is only
fixed by the claming plate, there is nothing to centre it. Yoy would ahve
to do that by hand (I suspect you'll neeed a spare spindle, a diak gauge,
and a lto of patience...)
The other problem is that the only source of 16 sector bubs is the rare
PDP8 version fo the pack.
I suppose you might be able to clut the extra ntoches in the exiting hub
and somehow block up the ones in the wrong palce, but....
Some people have rported usign what is effectively a digital PLL to
plater the timign of the sector pulses and use 12 sector packs with a
PDP8. I've not tried it...
-tony
3:06 p.m.
The reason I asked is that I have a couple of RK05's with crashed tracks
and I can find PDP-11 style RK05's at more reasonable prices. Thus I have
two correct hubs. But the balancing issue is a show stopper. I was hoping
that sector ring was fastened independently to the hub and wouldn't need
aligning.
Marc
On Tue, Mar 4, 2014 at 2:14 PM, Tony Duell <ard at p850ug1.demon.co.uk> wrote:
I've seen rumours that you can convert a PDP-11 RK05 disk into a PDP-8
style by swapping out the sector hub on the bottom.
Is this:
1. True, I've done it, or,
2 It oughta work, or,
3 No way.
Apart from screws, an RK)5 pack seems to consist of :
Upper Housing
Lower Housing
Hub
Magnetic plate on bottom of hub to lock to the drive spindle
Magnetic Disk
Clamp plate to fix the disk to the hub
A bloc kfo foam i nthe middle of the hub :-)
AFAIk, and everythign I have check confirms this, the difference is the
hub only. The PDP11 hub has 12 sector notches (13 nothces total), the
PDP8 one ahs 16 sector notches (17 total). The ring wit the sector
notches in it is integral with the rest of the hub.
In theory you can swap the hubs over. But be warned the disk is only
fixed by the claming plate, there is nothing to centre it. Yoy would ahve
to do that by hand (I suspect you'll neeed a spare spindle, a diak gauge,
and a lto of patience...)
The other problem is that the only source of 16 sector bubs is the rare
PDP8 version fo the pack.
I suppose you might be able to clut the extra ntoches in the exiting hub
and somehow block up the ones in the wrong palce, but....
Some people have rported usign what is effectively a digital PLL to
plater the timign of the sector pulses and use 12 sector packs with a
PDP8. I've not tried it...
-tony
5:27 p.m.
On 3/4/2014 3:06 PM, Marc Howard wrote:
The reason I asked is that I have a couple of
RK05's with crashed tracks
and I can find PDP-11 style RK05's at more reasonable prices. Thus I have
two correct hubs. But the balancing issue is a show stopper. I was hoping
that sector ring was fastened independently to the hub and wouldn't need
aligning.
Marc
I would think that you could swap the rings if you constructed a jig to
hold the stack and reattach the transplanted rings onto the pack while
on that ring. One can disassemble and remove the disc and spindle and
mount it with the bottom up. Then use a bar across the center with a
couple of orientations and a dial gauge and mark the location of the
original ring. Then remove the original and apply the one from your
other packs..
I didnt see if you noted whether the hole patter lines up, but that
could be dealt with and still maintain balance.
I recall that the packs used on the top loading Dynex drives had rings
that could be swapped w/o disturbing the spindle to disc fastening.
Those drives had circuitry to allow it to be adjusted easily to
accommodate different sector counts as needed.
jim
5 Mar
5 Mar
12:08 p.m.
The reason I asked is that I have a couple of RK05's with crashed tracks
and I can find PDP-11 style RK05's at more reasonable prices. Thus I have
two correct hubs. But the balancing issue is a show stopper. I was hoping
that sector ring was fastened independently to the hub and wouldn't need
aligning.
Alas not. On every RK)5 and compatible pack I've looked at, the sectroign
ring is integral with the hub.
As regards centering/balancing it, this is something I am going to have a
go at over the next year or so (read : wehn I have some time to restore
classic computers again). I need a 24 sector pack. Fortunately, that just
means cutting a notch midway between each pair of existing notches
(ignorign the index notch), but of course I wil lahve to remove the disk
from teh ub to do that, and re-fit it later.
I once worked on a Plessey drive with one fixed and one remveable
platter, the removeable one being an RK05 pack. The fixed platter was the
same disk, located on a machined register on the hub assembly. Remplacign
this disk with one taken from an RK05 pack gave no problems. Which
suggests that if you get the disk centred on the hub, that is good
enough. You don't ahve to mechanically balance it as well. Of course just
centring the disk accurately is non-trivial...
-tony
1:42 p.m.
On Mar 5, 2014, at 3:08 PM, Tony Duell <ard at p850ug1.demon.co.uk> wrote:
...
You don't ahve to mechanically balance it as well. Of course just
centring the disk accurately is non-trivial?
What?s the required accuracy? With some patience and an inexpensive dial indicator,
centering to .001 inch (25 micrometers) is doable; lathe operators do it all the time with
their 4 jaw chucks.
paul
4:41 p.m.
On Wed, Mar 5, 2014 at 3:42 PM, Paul Koning <paulkoning at comcast.net> wrote:
On Mar 5, 2014, at 3:08 PM, Tony Duell <ard at p850ug1.demon.co.uk> wrote:
What about using an inspection microscope over the disk surface to visually
align it? I imagine you could get a bit more precision this way, perhaps.
Kyle
...
You don't ahve to mechanically balance it as well. Of course just
centring the disk accurately is non-trivial...
What's the required accuracy? With some patience and an inexpensive dial
indicator, centering to .001 inch (25 micrometers) is doable; lathe
operators do it all the time with their 4 jaw chucks.
6 Mar
6 Mar
11:36 a.m.
On Mar 5, 2014, at 3:08 PM, Tony Duell <ard at p850ug1.demon.co.uk> wrote:
I mentioned that Plessey drive with the naked paltter going oto a
machined regiser in the hub. It was a very easy fit, I would guess a thou
or more of clearance. SO that gives some idea. My guess is that if you
could do it to within a thou it would be fine.
And yes,I've centred many thigns in the 4-jaw with a DTI. But there is
oen crucial difference. With the 4-Jaw, you can lightly clamp the object
with 2 of the jaws, then cetre in in the other direciton using the other
2 jaws to move it -- effectively using the screws of the chuck as
pseudo-leadscrews. But with the RK05 platter, there is nothing to move
it, just a clamping ring. It would be more like (for the lathe analogy)
trying to cntre something on a faceplate and then clmping it down. A lot
harder.
I am thinking I might make a fixture with some screws/pads to ba able to
move the platter slightly wrt the hub.
-tony
...
You don't ahve to mechanically balance it as well. Of course just
centring the disk accurately is non-trivial?
What?s the required accuracy? With some patience and an inexpensive
dial indicator, centering to .001 inch (25 micrometers) is doable; lathe
operators do it all the time with their 4 jaw chucks.
12:32 p.m.
On Mar 6, 2014, at 2:36 PM, Tony Duell <ard at p850ug1.demon.co.uk> wrote:
...And yes,I've centred many thigns in the 4-jaw
with a DTI. But there is
oen crucial difference. With the 4-Jaw, you can lightly clamp the object
with 2 of the jaws, then cetre in in the other direciton using the other
2 jaws to move it -- effectively using the screws of the chuck as
pseudo-leadscrews. But with the RK05 platter, there is nothing to move
it, just a clamping ring. It would be more like (for the lathe analogy)
trying to cntre something on a faceplate and then clmping it down. A lot
harder.
I am thinking I might make a fixture with some screws/pads to ba able to
move the platter slightly wrt the hub.
You?re quite right. The question amounts to the required accuracy for such a fixture.
From what you?re saying, it should be doable for an amateur to make.
Another possible approach, if the platter diameter is consistent within the runout
tolerance, would be to make a fixture that?s simply one large block of metal. Essentially
the cone tip of the hub, and concentric with it an opening exactly the right size for the
platter. It would take a fairly large lathe to make that, but the nice thing about it is
that it could just be cut in one sitting on any ordinary lathe, so long as the spindle is
in decent shape.
paul
7 Mar
7 Mar
12:29 p.m.
I am thinking
I might make a fixture with some screws/pads to ba able to
move the platter slightly wrt the hub.
You?re quite right. The question amounts to the required accuracy for
such a fixture. From what you?re saying, it should be doable for an
amateur to make.
Another possible approach, if the platter diameter is consistent
within the runout tolerance, would be to make a fixture that?s simply
one large block of metal. Essentially the cone tip of the hub, and
That is 'large'. I think you'd need a lathe that could swing something
about 15" in diameter, which is a lot more than most enthusiasts have
over here. Quit apart from that fact that a block of metal that size
would not be exactly cheap.
My I wonder.... Suppose you had a basepalte witl a copy of the spindle
tip in the centre so as to locate the hub accurately. And 3 adjustable
mtal pds at a 7" or so radiau , spaced at 120 degress. Put the original
disk on, adjust the pads to just touch the otside edg. Then remove the
clamp ring, lift off the disk itself and remvoe the hub to wor on it.
Then put the reworked hub back on the 'spindle tip', slide the disk in
palce, the pads wil cetnre it, and fit the clampign ring.
Tasht should be quite easy to make...
-tony
10 Mar
10 Mar
4:46 a.m.
You don't
ahve to mechanically balance it as well. Of course just
centring the disk accurately is non-trivial?
What?s the required accuracy? With
some patience and an inexpensive
dial indicator, centering to .001 inch (25 micrometers) is doable; 
5 Mar
5 Mar
1:41 a.m.
On Tue, 4 Mar 2014, Marc Howard wrote:
I've seen rumours that you can convert a PDP-11
RK05 disk into a PDP-8
style by swapping out the sector hub on the bottom.
Is this:
1. True, I've done it, or,
[...]
1.
I've done this in the past to change a crashed platter with a new one.
But usually, if you have the correct sector hub you already have a correct
disk pack for a PDP-8 (if it's not crashed). Just swapping doesn't make
much sense.
Christian
8:20 a.m.
On Wed, Mar 5, 2014 at 1:41 AM, Christian Corti <
cc at informatik.uni-stuttgart.de> wrote:
On Tue, 4 Mar 2014, Marc Howard wrote:
Well, I have a crashed PDP-8 pack and I can get a PDP-11 pack for a
resonable amount. PDP-8 packs seem to be about 2x as much. So the theory
was buy a PDP-11 pack and move the sector hub.
Marc
I've seen rumours that you can convert a
PDP-11 RK05 disk into a PDP-8
style by swapping out the sector hub on the bottom.
Is this:
1. True, I've done it, or,
[...]
1.
I've done this in the past to change a crashed platter with a new one.
But usually, if you have the correct sector hub you already have a correct
disk pack for a PDP-8 (if it's not crashed). Just swapping doesn't make
much sense.
Christian
12:17 p.m.
I've been going through a lot of RK05 packs lately and found that an easy
way of telling one from the other is that two sector marks can be visible
within the approximately 1.5" gap for an -8, whereas only one can fit for
the -11. Of course, turn the hub so that you're not looking at the index
area. :) You'll see three slits for the -8 and two for the -11 there. Just
thought I would share.
Do I understand remounting the hub to be as easy as getting the disk
centered by ensuring zero runout on the edge? For those who have experience
with cars or firearms, measuring the runout with a dial indicator should
not be a problem, I imagine. I haven't opened up an RK05 yet, but can you
utilize the spindle for this procedure, or would it be better done
externally?
That leads to another perhaps relevant question: cleaning. I hear people
have successfully cleaned these in the kitchen sink. Is deionized or
distilled water preferred over tap water? Any tips on this? Non-powdered
latex gloves should be worn, I imagine? We can start a new thread on this
if one would prefer.
Kyle
12:38 p.m.
New subject: Pack cleaning (was: Re: Convert PDP-11 RK05 disk pack to PDP8)
On Mar 5, 2014, at 3:17 PM, Kyle Owen <kylevowen at gmail.com> wrote:
...
That leads to another perhaps relevant question: cleaning. I hear people
have successfully cleaned these in the kitchen sink. Is deionized or
distilled water preferred over tap water? Any tips on this? Non-powdered
latex gloves should be worn, I imagine? We can start a new thread on this
if one would prefer.
Any leftover crud would be fatal, so tap water is most definitely out because of the
dissolved salts it contains. Distilled water might possibly work.
The only time I have seen a pack cleaned by hand (as opposed to in a specialized cleaning
machine) was when our college IBM 1620 sprung a leak in the (hydraulic) head actuators of
the 1311 drive. The IBM tech replaced the faulty gasket, bled the hydraulics, and cleaned
heads and packs using Kimwipes soaked in reagent grade isopropyl alcohol I obtained for
him from the chemistry department stock room.
Isopropyl alcohol is a mild solvent and well suited for removing oily stuff. The key
point here was to use high purity stuff; drug store ?rubbing alcohol? would certainly not
be a good idea.
If the dirt you?re dealing with is soluble in water rather than in some alcohol, then
distilled water might be the right option. But I would make it distilled, preferably from
a chemical supply company, nothing less.
paul
4:39 p.m.
New subject: Pack cleaning (was: Re: Convert PDP-11 RK05 disk pack to PDP8)
On Wed, Mar 5, 2014 at 2:38 PM, Paul Koning <paulkoning at comcast.net> wrote:
Any leftover crud would be fatal, so tap water is most
definitely out
because of the dissolved salts it contains. Distilled water might possibly
work.
That's what I was thinking, but I remember hearing someone on this list (I
think) saying they cleaned a pack under the kitchen sink. I was shocked to
hear it worked.
The only time I have seen a pack cleaned by hand (as opposed to in a
specialized cleaning machine) was when our college IBM
1620 sprung a leak
in the (hydraulic) head actuators of the 1311 drive. The IBM tech replaced
the faulty gasket, bled the hydraulics, and cleaned heads and packs using
Kimwipes soaked in reagent grade isopropyl alcohol I obtained for him from
the chemistry department stock room.
Isopropyl alcohol is a mild solvent and well suited for removing oily
stuff. The key point here was to use high purity stuff; drug store
"rubbing alcohol" would certainly not be a good idea.
If the dirt you're dealing with is soluble in water rather than in some
alcohol, then distilled water might be the right option. But I would make
it distilled, preferably from a chemical supply company, nothing less.
I've got access to a full-up cleanroom, so some chem-grade isopropanol and
DI water is no problem. In fact, a while back, I fixed an MFM hard drive
from an IBM PC/AT in the cleanroom. Completely
dismantled the platters from
the spindle, put it back together, and got several more
months of service
out of it, until it wouldn't spin up on its own (had to kick-start it).
Pictures here: http://imgur.com/a/LbfZb
Thanks for the info!
Kyle
5:27 p.m.
New subject: Pack cleaning (was: Re: Convert PDP-11 RK05 disk pack to PDP8)
On Mar 5, 2014, at 7:45 PM, "Kyle Owen"
<kylevowen at gmail.com> wrote:
I've got access to a full-up cleanroom, so some chem-grade isopropanol and
DI water is no problem.
Clean room? What's a clean room? You don't want to know where I've rebuilt CDC
Hawks, and it certainly wasn't even close to being clean.
(I did keep some of the fabric gloves, they are great for handling photographs)
On Wed, Mar 5, 2014 at 2:38 PM, Paul Koning
<paulkoning at comcast.net> wrote:
Any leftover crud would be fatal, so tap water is most definitely out
because of the dissolved salts it contains. Distilled water might possibly
work.
That's what I was thinking, but I remember hearing someone on this list (I
think) saying they cleaned a pack under the kitchen sink. I was shocked to
hear it worked.
6 Mar
6 Mar
4:44 a.m.
New subject: Pack cleaning (was: Re: Convert PDP-11 RK05 disk pack to PDP8)
On Wed, Mar 05, 2014 at 03:38:13PM -0500, Paul Koning wrote:
On Mar 5, 2014, at 3:17 PM, Kyle Owen <kylevowen at gmail.com> wrote:
The RK05 maintenance manual gives a cleaning
procedure. I have done it.
See document 95.
http://www.pdp8online.com/pdp8cgi/query_docs/query.pl?Search=rk05
Looks like that scan may have been of a copy of the manual. Bitsavers may
have a better scan.
The manual says water may damage the oxide binder.
I also used a bright light, lens brush and "air" can to remove as much
leftover dust after cleaning. For unknown condition packs I then mounted
the pack with the drive cover off so I could watch the platter for warp
as I spun it up. After the heads loaded I used the readrk05 program in
my dumprest http://www.pdp8online.com/ftp/software/dumprest/ to go over
the entire disk surface quickly keeping finger un unload button. I would
normally get a ping or two on the first pass or two when it knocks of a
leftover piece of dust then it would be quiet. If the packs were stored in
the bags and have not visible dust when you shine a light in through
the door I don't know if cleaning helps. I was doing this on dirty packs.
I didn't do it but flipping the switch to disable the head motion and leaving
it spinning for a while may also help get any reamaining dust off.
...
That leads to another perhaps relevant question: cleaning. I hear people
have successfully cleaned these in the kitchen sink. Is deionized or
distilled water preferred over tap water? Any tips on this? Non-powdered
latex gloves should be worn, I imagine? We can start a new thread on this
if one would prefer.
5 Mar
5 Mar
1:02 p.m.
I've been going through a lot of RK05 packs lately and found that an easy
way of telling one from the other is that two sector marks can be visible
within the approximately 1.5" gap for an -8, whereas only one can fit for
the -11. Of course, turn the hub so that you're not looking at the index
area. :) You'll see three slits for the -8 and two for the -11 there. Just
thought I would share.
Do I understand remounting the hub to be as easy as getting the disk
centered by ensuring zero runout on the edge? For those who have experience
I think so. AS I said in another message, there was a Plessey drive that
usd the naked platter from one of these packs, and it wa centred on a
machiend register on the hub. Nothing more.
with cars or firearms, measuring the runout with a
dial indicator should
not be a problem, I imagine. I haven't opened up an RK05 yet, but can you
utilize the spindle for this procedure, or would it be better done
externally?
I think you could use the drive spindle. Obviosuly turn it by hand, not
on the motor. My biggest worry would be gettig nthe aligned hub and disk
off the magnetic rign on the spindle withotu damaging them. It might be
an idea to put the lower part of the pack housing in place, fit the
disk//hub, aligne it, then use the housign to yank it off (after all,
that's how it's remvoed when the drive is in use),
That leads to another perhaps relevant question: cleaning. I hear people
have successfully cleaned these in the kitchen sink. Is deionized or
distilled water preferred over tap water? Any tips on this? Non-powdered
latex gloves should be worn, I imagine? We can start a new thread on this
if one would prefer.
Cleanign waht? The disk surface? Do not use tape water, it will leave
deposits. The correct cleaner is a 91%/9% mixture of propan-2-oland
distileld water.
-tony
10 Mar
10 Mar
4:55 a.m.
Am 05.03.2014 21:17, schrieb Kyle Owen:
Do I understand remounting the hub to be as easy as
getting the disk
centered by ensuring zero runout on the edge?
Easier. Just centered enough that
your drive does not walk away.
That leads to another perhaps relevant question:
cleaning. I hear people
have successfully cleaned these in the kitchen sink. Is deionized or
distilled water preferred over tap water? Any tips on this? Non-powdered
latex gloves should be worn, I imagine? We can start a new thread on this
if one would prefer.
NO WATER!!! DO NOT USE WATER!!! See the RK05 manual for cleaning
instructions. They say explicitely that water will damage the oxide
layer. You can blow off dust with your mouth - but take care not to spit
onto the disk the manual says...
I use a table with a big clean sheet of paper. I grab the thing only by
the hub. And then I use paper towels and 100% IPA to rub off the dirt.
Can make you sweat...
I don't let the disk dry - I rub it dry.
I don't wear gloves and avoid touching the disk.
After cleaning I put the disk into a drive and use the heads to kick off
the lint (moving manually). Makes some noise. When the pack has become
quiet, it is ready to use. The sound of loose noise is different from
the sound when the heads are crashing...
After this procedure, I usually give the heads a quick cleaning.
:-)
2:58 p.m.
Am 05.03.2014 21:17, schrieb Kyle Owen:
i've seen photos of people at the factory inspecting disk packs
(admittedly the 5 and 10 disk ones) with a dial test indicator to check
the cnterign of the platter(s). I would assume that was necessary.
If the centering is as non-critical as you suggest, I wonder why there
wasn't a machined regiser (step) on the hub, so you could just put the
platter on and clamp it up
Do I understand remounting the hub to be as easy
as getting the disk
centered by ensuring zero runout on the edge?
Easier. Just centered enough that
your drive does not walk away. That leads to another perhaps relevant question:
cleaning. I hear people
have successfully cleaned these in the kitchen sink. Is deionized or
distilled water preferred over tap water? Any tips on this? Non-powdered
latex gloves should be worn, I imagine? We can start a new thread on this
if one would prefer.
NO WATER!!! DO NOT USE WATER!!! See the RK05 manual for cleaning
instructions. They say explicitely that water will damage the oxide layer. You can blow off dust with your mouth - but
take care not to spit
onto the disk the manual says...
THat is one of the all-time clasic instrucitons :-)
Antoher warning I rememebr from this manual (or maybe one on another
drive, but it applies) is that in a lot of cases the air from a
compresaed air line contains oil. So unless you're sure it doesn't, don't
use it for cleaning said disks. I think those 'air duster' cans (which a
friend calls 'cans of pneumatic fluid') are fine (although expensive).
-tony
5:45 p.m.
On Mar 10, 2014, at 5:58 PM, Tony Duell <ard at p850ug1.demon.co.uk> wrote:
...
Yes, ?canned air? should be ok. And air from compressors can be filtered. Also, there
are ?oil-less? compressors. Air brush setups are an example where oil must be avoided,
and this is where oil-less compressors may be found, or oil-removal filters. The sort of
cleaning we?re talking about here is probably more demanding than airbrushing is, though.
paul
layer. You can blow off dust with your mouth -
but take care not to spit
onto the disk the manual says...
THat is one of the all-time clasic instrucitons :-)
Antoher warning I rememebr from this manual (or maybe one on another
drive, but it applies) is that in a lot of cases the air from a
compresaed air line contains oil. So unless you're sure it doesn't, don't
use it for cleaning said disks. I think those 'air duster' cans (which a
friend calls 'cans of pneumatic fluid') are fine (although expensive).
11 Mar
11 Mar
12:48 p.m.
Yes, ?canned air? should be ok. And air from
compressors can be
filtered. Also, there are ?oil-less? compressors. Air brush setups are
an example where oil must be avoided, and this is where oil-less
compressors may be found, or oil-removal filters. The sort of cleaning
we?re talking about here is probably more demanding than airbrushing is,
though.
Sure... Obviously there is a way to compress air without contaminating it
with oil, those cans have ot be illed in the first place :-).
The warning, I think, was more that there are plenty of compressors which
do have oil in the output stream (in for air-operated tools, this can even
be an advantage). Such compressed air is not at all a Good Thing to use
on RK05 packs, so if in doubt, don't use it. If you ahve a truely oil-less
compressor, that will be fine,.
-tony
12:46 a.m.
Hi,
i've seen photos of people at the factory
inspecting disk packs
(admittedly the 5 and 10 disk ones) with a dial test indicator to check
the cnterign of the platter(s). I would assume that was necessary.
I claim that it
was (only) better to do that. Well centered disks
minimize noise, vibration, and wear at the spindle bearing.
The disk surface has no relationship to where the tracks will be written
onto it.
If the centering is as non-critical as you suggest, I
wonder why there
wasn't a machined regiser (step) on the hub, so you could just put the
platter on and clamp it up
Perhaps they planned to use disks with different inner
hole diameter? I
was wondering about that as well. Very impracticable.
I thoght the correct cleaner did contain water
(something like a 91%
propn-2-ol to 9% distileld water mixture)
Yes, they say 91% alcohol. I assume that
they meant "at least" 91%...
Philipp
12:54 p.m.
Hi,
Sure. The onyl reason to have it well-centred it to improve mechanical
balance and reduce vibration.
I wonder if excessive vibration could end up makign the heads more
unstable and more liable to crash.
In any case, it can't hurt to get it centred as accurately as you can.
i've seen photos of people at the factory
inspecting disk packs
(admittedly the 5 and 10 disk ones) with a dial test indicator to check
the cnterign of the platter(s). I would assume that was necessary.
I claim that it
was (only) better to do that. Well centered disks
minimize noise, vibration, and wear at the spindle bearing.
The disk surface has no relationship to where the tracks will be written
onto it. If the centering is as non-critical as you
suggest, I wonder why there
wasn't a machined regiser (step) on the hub, so you could just put the
platter on and clamp it up
Perhaps they planned to use disks with different inner
hole diameter? I
was wondering about that as well. Very impracticable. I thoght the correct cleaner did contain water
(something like a 91%
propn-2-ol to 9% distileld water mixture)
Yes, they say 91% alcohol. I assume that
they meant "at least" 91%... 
12 Mar
12 Mar
1:12 p.m.
----- Original Message -----
From: "Tony Duell" <ard at p850ug1.demon.co.uk>
To: <cctalk at classiccmp.org>
Sent: Tuesday, March 11, 2014 7:54 PM
Subject: Re: Convert PDP-11 RK05 disk pack to PDP8
Whats the track width on an RK05, I semm to recall its 100TPI so thats
10thou per trak, add a bit of guard space so maybee 8thou track width ? if
you have 1 or 2 thou exentricity ok, more and could lead to
interchangability problems ?, mind you 4 thou out may meen its vibrating so
badly that this is the least of your problems.
Dave H
Hi,
Sure. The onyl reason to have it well-centred it to improve mechanical
balance and reduce vibration. i've seen photos of people at the factory
inspecting disk packs
(admittedly the 5 and 10 disk ones) with a dial test indicator to check
the cnterign of the platter(s). I would assume that was necessary.
I claim that it
was (only) better to do that. Well centered disks
minimize noise, vibration, and wear at the spindle bearing.
The disk surface has no relationship to where the tracks will be written
onto it. I wonder if excessive vibration could end up makign
the heads more
unstable and more liable to crash.
In any case, it can't hurt to get it centred as accurately as you can.
I doubt that's the reason, surely all the disks awere made in the sme way
to pretty tiget tolerancs. In any case I mentioned a drive that used a
'naked platter' from such a pack as the fixed disk, which was located by
the centre hole. AFAIK any spare platter would fit.
I thoguth I saw somewhere that the trace of wanter had to be added, adn
that even purer proan-2-ol was nto ideal.
-tony
-----
No virus found in this message.
Checked by AVG - www.avg.com
Version: 2012.0.2247 / Virus Database: 3722/6680 - Release Date: 03/11/14
If the centering is as non-critical as you
suggest, I wonder why there
wasn't a machined regiser (step) on the hub, so you could just put the
platter on and clamp it up
Perhaps they planned to use disks with different inner
hole diameter? I
was wondering about that as well. Very impracticable. I thoght the correct cleaner did contain water
(something like a 91%
propn-2-ol to 9% distileld water mixture)
Yes, they say 91% alcohol. I assume that
they meant "at least" 91%...
13 Mar
13 Mar
1:33 p.m.
Sure. The onyl
reason to have it well-centred it to improve mechanical
balance and reduce vibration.
Whats the track width on an RK05, I semm to recall its 100TPI so thats 10thou per trak, add a bit of guard space so maybee
8thou track width ? if
you have 1 or 2 thou exentricity ok, more and could lead to
interchangability problems ?, mind you 4 thou out may meen its vibrating so
badly that this is the least of your problems.
No. Remember the hub remains fixed to the platter when youremove or
insert a cartridge. So if the platter is off-centre, the tracks will
remains cirles, i nthe right places relative to the centre of the hub.
The fact that they are not concentric with the outside edge of the
platter doesn't matter at all
-tony
12 Mar
12 Mar
1:42 p.m.
----- Original Message -----
From: "Tony Duell" <ard at p850ug1.demon.co.uk>
To: <cctalk at classiccmp.org>
Sent: Tuesday, March 11, 2014 7:54 PM
Subject: Re: Convert PDP-11 RK05 disk pack to PDP8
Doo, another dident engage brain before posting, :( as Philipp states ,
The disk surface has no relationship to where the tracks will be written
onto it.
Obviuos when you think about it for more than 5 seconds .
please ignor my other post
Dave H
Hi,
Sure. The onyl reason to have it well-centred it to improve mechanical
balance and reduce vibration. i've seen photos of people at the factory
inspecting disk packs
(admittedly the 5 and 10 disk ones) with a dial test indicator to check
the cnterign of the platter(s). I would assume that was necessary.
I claim that it
was (only) better to do that. Well centered disks
minimize noise, vibration, and wear at the spindle bearing.
The disk surface has no relationship to where the tracks will be written
onto it. I wonder if excessive vibration could end up makign
the heads more
unstable and more liable to crash.
In any case, it can't hurt to get it centred as accurately as you can.
I doubt that's the reason, surely all the disks awere made in the sme way
to pretty tiget tolerancs. In any case I mentioned a drive that used a
'naked platter' from such a pack as the fixed disk, which was located by
the centre hole. AFAIK any spare platter would fit.
I thoguth I saw somewhere that the trace of wanter had to be added, adn
that even purer proan-2-ol was nto ideal.
-tony
-----
No virus found in this message.
Checked by AVG - www.avg.com
Version: 2012.0.2247 / Virus Database: 3722/6680 - Release Date: 03/11/14
If the centering is as non-critical as you
suggest, I wonder why there
wasn't a machined regiser (step) on the hub, so you could just put the
platter on and clamp it up
Perhaps they planned to use disks with different inner
hole diameter? I
was wondering about that as well. Very impracticable. I thoght the correct cleaner did contain water
(something like a 91%
propn-2-ol to 9% distileld water mixture)
Yes, they say 91% alcohol. I assume that
they meant "at least" 91%...
4253
days inactive
4262
days old
30 comments
11 participants
participants (11)
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