Thursday
20th November 1997 - Calm
From
John Storey.......
It
is recommended that, when in Antarctica, you try to learn
something new. I'm sitting here learning "Pine".
Mcba says is better than "mail" and he's right.
Antony showed me how to switch it on. It doesn't use the mouse
but you can move the cursor round with the arrow keys, just
like in the good old days. If you get 4,000 copies of this
message, or if it turns out to be one long line of 1,728 characters
- sorry.
How
wonderful it is to have the wind down to 10 knots - for the
first time since we arrived. Suddenly it's quiet and peaceful,
and it's possible to potter around outside without being instantly
frozen stiff.
After
I'd dashed off my message last night, I of course rushed out
to help Ant clean the NISM. He had been so keen to get started
on it that he'd gone and got a Sprite, and in fact I met him
on the way out to the MAPO building. I guess he must have
driven via Dome C as he was only just arriving when I got
to MAPO; Ant assures me that it was by far the quickest way.
Anyway, together we cleaned the NISM - a truly disgusting
task not for the faint-hearted. By the time we'd finished
we didn't have much enthusiasm left for anything, so we went
and wrote postcards. (Actually we took the Sprite for a quick
fang first.)
Ev
has a nice little digital camera, and has taken shots of all
the damage caused to the AASTO by the propane leak. He intended
to put them on the net so that y'all could see it with your
own eyes. Unfortunately, there seems to be an incompatibility
between his Windows 95 compatible camera and his Windows 95
compatible computer, and the images won't transfer. I don't
know much about PCs, but I suspect he's just used the wrong
font when he set up the C:> system/cam/bios.$ram.config
files. Or it might be just that his PC has the wrong serial
number.
Additional
entertainment here comes from the fact that they've started
digging out the cargo arches in preparation for rebuilding
South Pole Station. This has consisted mainly of using the
bulldozers to carve great gouges in the landscape (snowscape?).
However, they've discovered that the snow is compacted into
ice on the side where the aircraft are, and is too hard for
the biulldozers to penetrate. We offered them a jar of Brown
Slime #1, but this was politely declined. Instead, they're
using *dynamite*. There's a muffled bang and then snow all
over the place. Over the next few weeks the station will come
to resemble something like it was in 1973, before 25 of years
of snow-fall buried it. Should be interesting.
This
morning we busied oursleves installing the heavy-duty stepper
motors in the NISM and MISM. We did the NISM first since,
it was indoors and in bits. This was a moderately straightforward
exercise, once we recalled the bizarre attributes of the stepper
motor code. Our first problem was to be absolutely sure of
the stepper motor rotation direction, since even the Tektronics
oscilloscope was unable to calculate it from first principles.
(The Fluke multimeter took a punt, but got it wrong.) Characteristics
of the code that made this exercise unusually difficult include:
- Calibrate
rotation direction CW or CCW? Goes CCW regardless of what
you type.
- The
limit switches only work if you hit the one the computer
thinks the motor is travelling towards. This is actually
very nasty, as if the motor is going the other way it won't
stop until it tears the cables out. Things that can make
the motor go the wrong direction include:
a).
Me, especially if taking advice from the Fluke.
b) Running the motor at a step rate close to the fundamental
resonance
c) Having one phase fall off.
I
suspect we're running an old version of the stepper motor
code, as I'm sure these things were fixed a while back
As
expected the rotator works beautifully, and the stepper motor
couldn't care less if the thing is balanced or not. Calculation
shows that if the rotator stalls (eg if it hits a limit switch
that the software ignores), it will exert a lateral force
of 2,000 N on the gearbox and on the teeth of the aluminium
ring gear. I've put my money on the ring gear stripping; the
Tektronics has backed the gearbox shattering at 3 to 1. No
one is prepared to put any money at all on a non-destructive
stall.
We're
running the motor at the minimum current that I'm confident
will overcome the detent torque (oh, how I loathe stepper
motors), namely the same current that we ran the old motors
at. (This also saves us having to change the circuit boards.)
Today
all the rest of the boxes came; ie Abu, the 386 super replacement,
the AASTO manual, and various goodies. All we await now are
the replacement Sonnenschweins, coming as hazardous cargo
(and they don't know the half of it!)
The
Good Will power supply (seriously) that powers the super and
charges the instrument batteries when the TEG is down appears
to have gone belly-up. The left-hand 30V supply won't go above
15V and the right hand supply has "bad" written
across the meter and in any case doesn't work at all. Only
the 5V section seems to still work. However, today the super
started spontaneously booting itself every few minutes for
no good reason, just like it was doing last January. There
are times when good will on its own is not enough, and the
super is now powered up from a Lambda 20V, 3.3A supply. it
will be interesting to see if the super continues to work.
I'm
not inclined to bring the 386 in at this stage, as there's
very little space in the AASTO. The existing super reliably
boots off its floppy, and we'll have a go at the hard disk
in a day or two. We'll bring the 386 in when there's a bit
more room.
On
a triumphant note, it's clear that there's *no* ice inside
the instruments, the blackbody is completely free of ice,
everything moves and rotates like it should, and there's only
a teensy bit of snow that's got inside the yellow cover of
the MISM. One side of the NISM cover split off; Ant has glued
it back together and has it sitting in the MAPO shop weighed
down with a rotary pump, a lathe chuck, and a few hundred
pounds of odds and ends (the side is badly warped - it's not
clear it's going to stick back successfully).
Andre;
thanks for talking to Nick Roberts about the chemicals. We're
bringing back samples - do you think he'd be prepared to look
at them and tell us if its fluoride, chloride or sulphate?
The possibility of sulphate from the batteries is an interesting
one - Ev says the racks look "blacker" than you
get from a standard TEG melt-down.
Thanks(?)
also for the advice that we use the Stromlo MoS2 spray-on
lubricant for the bearings. We fished the tin out and it was
*stuffed*. We've placed it under the ANU poster... Ant found
some teflon-based spray-on stuff in MAPO; seems to work a
treat.
As
a final task we installed the new stepper in the MISM. It's
always a hard decision whether to work outside in the cold
(with all those tiny screws, all different sizes), or go to
the trouble of disassembling everything and bringing it indoors.
We opted for the former - it took hours. Finally, when rotating
the MISM by hand to check the balance there's something "rattling"
inside. Quel horeur! If it's a washer, that's ok. If it's
a lens, that's not so good. Ant says that since the MISM can
see him, that's about as good as it gets. I guess it could
be a piece of CVF. I'm happy to run with the existing CVF,
at least until January.
Ant
put all his clothes on to wash, only to have the water to
the Elevated Dorm fail. He now has a whole collection of wet
clothes. He's taking it well, but seems reluctant to go out
and pull the AFOS off the tower in his pajamas.
Now,
to send this I just do ctrl-alt-delete....
 
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