Re: OHVM HV Breakdown Test, Plastic Use Warning

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Bert Hickman by way of Terry Fritz <teslalist-at-qwest-dot-net>" <bert.hickman-at-aquila-dot-net>

Hi David,

Congratulations on a successful HV Stress Test on the divider!

Re: the cracking problem - this sounds like stress-solvent crazing from the 
solvents in the flux remover. A few years back I remember hearing about a 
coiler who tried to degrease his brandy new polycarbonate form by wiping it 
with methyl alcohol. To his horror, he could see a growing network of 
cracks appear, the cracks then grew together, and the entire form 
disintegrated into small shards in less than a minute!  =:^[

Solvents and plastics, particularly polycarbonate (PC) AND acrylic (PMMA)), 
often don't play well together. The problem is especially apparent when the 
plastic is under tension, curved, or has other surface stress 
concentrations (i.e., drilled holes and mounting points).

Best regards,

-- Bert --
-- 
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Tesla list wrote:
>Original poster: "David Sharpe by way of Terry Fritz 
><teslalist-at-qwest-dot-net>" <sccr4us-at-erols-dot-com>
<SNIP>
>Although slightly off this topic, a piece of advice for those of
>you out there using Polycarbonate (Lexan) for components or
>assemblies.  DO NOT allow fast evaporation liquids (canned
>air, defluxing compounds, fast evaporation aromatics) to
>contact the Lexan.  My first cover plate cracked between
>3 holes when I used flux remover on OHVM divider board!
>It appears to be a thermal shock phenomenon, that will cause
>cracks to propagate through the Lexan; IDK if this problem
>is possible with other plastics commonly used (ABS, Plexiglas
>[Acrylic/Perspex]).  Surprised the hel.. out of me, and set
>my completion date back a week...  :^C
>Up loaded two new files showing test setup for 2.4kV and
>the oil divider final subassembly. Files are at:
>http://hot-streamer-dot-com/dave
>    OHVM 2_4kV HV divider test setup.jpg
>2.4kV powered setup to determine Rdivide ratio
>    OHVM Oil Jacket Rdivider.jpg
>Divider nework assembly completed (including oil), ready for use.
>Corrected error seen at 60Hz <<1%.
>Regards
>Dave Sharpe, TCBOR/HEAS
>Chesterfield, VA. USA
>
>.