nuckolls.bob(at)aeroelect
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 Posted: Mon Jul 26, 2010 9:37 pm Post subject: Stan's concerns for starter contactor locations (revisited) |
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Quote:
Bob,
For a starter contactor mounted on the engine firewall, can I
anticipate any problems if the hot air from the oil cooler (180-200
deg F) is directed onto the contactor?
Thanks,
Stan Sutterfield
Stan,
Ferg looked at my previous posting on your query and
thought that I might do a better job . . . got my
tongue tangled around my eyeteeth and couldn't see
what I was typing . . . or some such excuse. Let's
try again
------------------------
No, the starter contactor is not generally used during flight
and it's internal temperatures will be no hotter than the
ambient.
Actual in-flight temperatures may not be as hot as you think.
Just for grins, it would be cool to measure and document the
highest observed temperatures on selected components like the
starter contactor, gascolator, magneto housings, any
electro-whizzies, etc. under the cowl during a fly-off. You
need to record OAT and local ambient under the cowl so that
any single measurement can be correct for other weather
conditions.
I think the results will surprise you.
On the other hand, battery contators are continuous duty devices and
exhibit significant temperature rise above ambient. Since service life
is influenced by temperature, it's always good to minimize exposure
to high ambients. But at the same time, the el-cheapo contactors we've
been using for decades seem to perform well under the cowl.
Once our 9024 series contactor power manager is in stock,
one could use it to greatly reduce the temperature rise
(and energy demands) for keeping the el-cheepo contactor
closed. This functionality emulates the much more expensive
"low power" contactors. Further, when and if contactor replacement
is necessary, you just replace a contactor . . . not the
contactor + smart control electronics.
Bob . . .
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