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Hello,

Having been told in no uncertain terms "Don't be so problematic" for asking
too many questions (Deming said once that there was no substitute for
knowledge) I set about to do the job based on the confident instructions
given to me in previous correspondedence. A few days later I received the
original Frank Bartlett Instructions PDF file from Steve Grobler and could
see how it was supposed to be done as written and drawn by an expert.

Lessons learnt:

1. Cutting the top of the filling tube WAS A MISTAKE. As solder penetrated
into the tube in the original manufacturing process it took several cuts to
reveal the opening, by which time the filling tube was much shorter and as
we all learned at childhood it is easy to cut things but pretty difficult to
put them back together. I should have either unsoldered it or better still
used Bartlett's way of gently drilling through the solder with a
watchmaker's screwdriver holding the unit upside down to prevent swarf
falling into the cylinder.

2. Yes as I suspected IT WAS very important to fill exactly the correct
amount of Hexane. Too much and you cannot form a bubble, too little and you
cannot get rid of it or reduce its size.

3. As I could not find a 5ml syringe I bought a pack of 10 1ml syringes used
by diabetics. THIS WAS a very fortunate move as when you fill the syringe
with Hexane and start injecting it the Hexane reacts with the synthetic
rubber pistone inside the syringe and by the time you empty it in the
pistone seizes and you have to throw it away and use a new one. In my case
3ml were needed and the 4th was an overfill which had to be squirted out to
get to the right amount of liquid. I made sure a window was open and the
bottle was well stoppered between fillings - the staff is highly volatile
and flamable and can ruin your whole day if it goes "Poof".

The sextant now works like a dream. I am taking series of 12 individual
shots and averaging the results to determine its combind error at various
altitudes. It appears to be in the order of 4.5' - 4.7' between 15-35
degrees

Hope this info might help somene's future endevours.

Best regards

Zvi

   

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