On Aug 3, 9:11, Allison J Parent wrote:
> Subject: Re: Oh heck it booted
>
> < > ;-)). But rubber is not the easiest material to turn to size - my
gues
> < > is you need to take a very light cut...
> <
> < With a very sharp cutting tool!
>
> You don't cut it you grind it! If done on a lathe you turn the rubber
> part and run a high speed grinder against it. It's insures it will be
> concentric and gives a smooth surface.
In the workshops I've seen where it's handled, it's usually done with a
very sharp tool with a very acute cutting angle (I've seen razor blades
mounted in a holder for this) and lubricated with glycerine.
For some jobs, I've seen a tubular cutter (rather like a cork borer)
mounted in the tailstock and pressed into the workpiece, similarly
lubricated with glycerine.
--
Pete Peter Turnbull
Dept. of Computer Science
University of York
William Donzelli <william(a)ans.net> wrote:
> I am not sure why classic networking stuff tends to be shunned like a
> rabid dog. Stuff from the 1970s is quite rare, but 1980s era stuff (CSUs,
> switches, etc.) tends to be around, and now quite available, now that T1s
> are becoming turtle highways.
Some thoughts:
With many of these devices, it takes (at least) two to tango, and of
course you never find both together. (What is the sound of one statmux
clapping?)
Synchronous modems often didn't just carry the data from one end to
the other, they also provided clock signals to the DTEs. Many DTEs
expect to see those clock signals and won't originate them, so getting
two nearby ones to talk over direct cabling can be an interesting
proposition.
Some of us probably worked with this stuff back in the days when it
was new (1983-1989 in my case). "Fun" is not the adjective that comes
to my mind.
> How about running a T1 line between the
> house and garage? With appropriate routing, its performance can be quite
> suprising.
Can you do this over dry copper, for short runs?
If so, would you want to? You mentioned in another post that you'd
have to run conduit for FDDI, and that makes me think there might be
some open space between hither and yon. Sure, you could run copper,
but wouldn't electrical potential differences be a problem?
I know that we used to have a fiber run under the parking lot at the
office, and Ethernet-fiber bridge things at the ends (two buildings
w/parking lot between).
> Does anyone on this list have any classic networking stuff beyond
> ethernet/token thing cards?
Not a lot, and mostly not by intent. Recently I got an HP9000/220U
with some extra boxes that I believe are a CSU and some flavor of mux.
No, it's not at all clear to me why they were piled together into one
lot; the 9000 didn't have the right sorts of I/O for this.
-Frank McConnell
Thanks to everyone that was helping solve our PDP-11 boot problems but
it seems that part of the problem was the fact that the backplane was
giving out (it actually went up in smoke on friday night while we were
playing with it, as did the front panel to my IMSAI, what a night that
was).
So again, thanks...
Tony Dellett
PS: If anyone in the Massachusetts/New Hampshire area has a spare RX01
that they wouldn't mind parting with, we have alot of Q-Bus cards that
need a backplane :)
Tony
< Hmmm. Well, I wonder about this. I know such services exist in the US
< well, but they still at least have battery on the line. I would wonder
< what good a dry point-to-point connection through the telco would be ove
< several miles, where the resistance in that length of wire would absorb
< whatever voltage you put on it.
The service exists, I used to use it 25 years ago for remote base stations
(radio service). It was called a dry copper pair and went point to point
with NOTHING else. It had to be that way as you would put audio on it and
DC on it to either key the transmitter or disable to tone squelch. the
average circuit resistance ws about 1kohm/mile. So the remote end didn't
sense voltage but instead sensed current (~8-9ma) and polarity to do
switching. Audio was put on the pair the normal way (differential via
transformer).
Allison
>> Okay, I've now given up hope that those old modems will ever be
>> at all useful or interesting to me. So they're up for grabs,
>> for the cost of postage.
just a thought, but were these modems ever designed to connect to a
public network? I've got a couple of old BT modems that seem to be
designed to only work on a private, internal network (at least that's
what the manuals imply), so maybe line voltages are different or
whatever...
cheers
Jules
I'm forwarding this message from another classic computer list I'm
on.... I figured you folks may be able to help him out a little
more. Please reply to him personally at his e-mail address given at
the far bottom....
Thanks,
CORD
--
I finally took a good look at that new PDP-11/23 I purchased some time
ago. It seems to have some normal looking DEC cards in it (LSI-11/2,
others). It does, however, have an interesting looking card set from
Associated Computer Consultants, called "MDMA" (as far as I can tell). It
appears to be from the mid-1980s. One card contains some sort of engine,
with ROMs and (4) 2901s. The other card contains a bunch of glue and
interface stuff, and has a connection to a big round military type
connector (the modern versions of the Cannon connector) on the back panel
of the chassis marked "IMP".
Being that this computer came from a certain spooky branch of the
U.S., that "IMP" looks awfully suspicious. Could this little DEC box have
been slated for the ARPAnet, but came just a little too late?
All I have is the processor - no drives or OS, so I can not tell much if I
power it up.
William Donzelli
william(a)ans.net
< I'm surprised by this. I'd thought about ways of linking any number
< of old PCs at up to 2000 foot distances, and thought about recreating a
2000ft is within the capability of RS422 at data rates that are in the
megabit range. There are other simple solutions like RS423 at low data
rates. The DEC mill used to have many central systems that often were
remote from the users by as many as 6 floors vertically and several
hundred feet horizontally. (Royalt was ML11/M1 and our group was
ML3-6/A1) we still ran 4800 or 9600 serial over the 500+ feet of wire
of the standard dual twisted pairs of phone co wire.
The biggest problem was the possibility of ground loops. With care
that's can be avoided though RS422 (balanced differential) can deal with
that as can RS485.
Allison
I have 2 of these XT bus boards, plus a PC-68K MMIO daughterboard.
They are copyright 1985/1986 by N.J. Costanzo & TLM Systems, Inc.
1-meg on-board, smartwatch, no cpu or roms
Can anyone provide additional information re:
original use, availability of roms, system software?
Any information appreciated.
Jim
< > You don't cut it you grind it! If done on a lathe you turn the rubbe
< > part and run a high speed grinder against it. It's insures it will b
< > concentric and gives a smooth surface.
<
< In the workshops I've seen where it's handled, it's usually done with a
< very sharp tool with a very acute cutting angle (I've seen razor blades
< mounted in a holder for this) and lubricated with glycerine.
You can if you have the right tools. Grinding is easier for most to do.
I make TU58 drive wheels using thickwall rubber tube or tygon and mount
the assembled result on an old tu58 motor and "grind" on a bench grinder.
I get a good round smooth surface, minimal setup. The hub used is the
one with the tire turned to goo, with the goo removed.
< For some jobs, I've seen a tubular cutter (rather like a cork borer)
< mounted in the tailstock and pressed into the workpiece, similarly
< lubricated with glycerine.
For general shapes its ok, the deformation affects accuracy. We used
that to get the general shape (tubes or plugs) and then mounted them
and did final grind. It was what the chief engineer wanted.
Generally the size of the drive roller is allowed considerable latitude
but roundness is desirable.
Allison
