Olive Oil & Spica

["McCarty, Richard" <RMcCarty@domain.elided>]

Hello All -

Rich Hirsch wrote in reply to my posting:

1) Olive oil freezes at about 21 deg F (-6 deg C). The TA must operate
over a wide temperature range, ca. -10 deg F to 140 deg F. Why use a
fluid that would not be effective at a temp. slightly below freezing?

OK, but what's the freezing point of refined olive oil?

2) In many ways the piston half of the TA acts like a tiny hydraulic slave
cylinder, so why not just use hydraulic fluid? It meets the temp.requirement
given in 1) above and the price is certainly right. How well would olive oil
work well as hydraulic (brake) fluid?

I believe that brake fluid is designed to transmit force ( a very
non-compressible fluid ) 
while minimizing changes in volume due to temperature changes. The fluid in
the TA needs to act like the fluid in a thermometer, expanding at a known
rate with increase in temp. I can imagine the Spica engineers testing
various fluids to find one that has the correct expansion coefficient for
the requirements of the logic section of the pump...
 
3) The TA contains rubber seals that must stand up to the TA fluid. Can you
imagine asking a counter man for an O-ring resistant to olive oil?

Is olive oil bad for rubber?

I know this is kind of silly and pointless, but I was repeating what Wes I.
related to me before he rebuilt my pump & TA. He said that the TAs need to
be rebuilt very carefully because the fluid must be reused as nobody knows
for sure what it is, and that the best guess he's heard was highly refined
olive oil. Maybe he was pulling my leg ?. Again, it doesn't really matter,
but there's always time for pointless, friendly arguments...

Regards,
Rich M
72 GTV

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