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----- Original Message -----
From: "Alexandre Eremenko" 
To: 
Sent: Thursday, November 11, 2004 1:36 PM
Subject: SNO sextants


> By the way, SNO-T comes with a bottle of oil and the manual
> gives the precise description of this oil (some
> Soviet standard) and also says:
> a substitute can be "Aeroshell Fluid 12"
> manufactured by Shell.
>
> Does anyone know what is this?

Google first hit says:

AeroShell Fluid 12
AeroShell Fluid 12 is a low volatility synthetic ester oil used in aircraft
instruments and also for the general lubrication of aircraft. It is
oxidation and corrosion inhibited, and possesses good high and low
temperature characteristics.
AeroShell Fluid 12 is used for general aircraft lubrication as well as for
aircraft gyro instrument gimbal bearings, separately lubricated high speed
turbines and compressors, aircraft air cycle equipment and electronic
equipment. AeroShell Fluid 12 is particularly suitable for use when an oil
with a low evaporation rate is required at high and low temperatures
Click here for AeroShell Fluid 12

Back to AeroShell Home

Many other hits, you could probably pick it up at a small aircraft
centre/airport

I have never felt the need to dismantle my SNO-T. My approach is to keep it
clean. Absolute minimum of lubrication, just enough to avoid metal to metal
contact. I have been casual in my choice of lubricant, often using WD-40
style products...just the lightest spray, if I can see lubricant running
off, I reckon its way overdone and attracts dirt. I must say that my sextant
is used in a temperate Australian environment. Possibly, use below -10C
or -20C could require greater care in choice of lubricant.

If you were to get a serious amount of dirt in the drum (salt, beach sand),
previous discussion here has suggested rinsing out with fresh water . The
drum could be taken off (3 screws) for that purpose.

Personally, I think the enclosed drum works pretty well in keeping out the
ingress of dirt.

Finally, might I note that many of the texts on sextant maintenance (Bauer,
etc) refer to the "much loved" or "tortured" sextant syndrome. They are
referring to the sextant being constantly fiddled with, adjusted, cleaned
and lubricated, to the point that screws become loose and worn  in their
holes, with the result that adjustment and alignement are grossly affected.

Lee Martin

   

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