nuckolls.bob(at)aeroelect
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 Posted: Wed Jan 24, 2024 10:08 am Post subject: 'Funky' fuses and other interesting adventures |
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Shortly before the holidays we had a brief
thread concerning the relative merits of utilizing
automotive fuses of unknown source and equally
unknown qualifications.
We harkened to the admonitions from representatives
of Busssman, Littlefuse, etc. etc:
"NO . . . you can't have that . . .
you'll shoot your eye out!"
Oops . . . wrong movie . . .
"Those fuses do not come with the
assurances of performance control
and reliability offered by our
products . . . you're gonna set
your wires on fire!"
Okay, as we've discussed many times on this
forum over the years, the science of good
design requires a working knowledge
in properties of materials, management of energy
and refinement of process. Doesn't matter
if you're baking cheese souffle, building
a house . . . or wiring an airplane.
There's another bit of wisdom handed down to
us from history:
"I often say that when you can measure what you are
speaking about, and express it in numbers, you
know something about it; but when you cannot
measure it, when you cannot express it in numbers,
your knowledge is of a meagre and unsatisfactory kind."
---- Lord Kelvin ----
To be sure, a great deal of what is pushed down
on us these days is considerably lacking in
numbers!
Okay, let's consider how we can 'go get the
numbers'.
I've acquired a new tool for the mess-making
shop. Toward the goal of being able to test and
quantify performance on various components,
an accurately calibrated electronic load-bank is
of considerable value.
This critter will sink up to 250 watts with
max voltage of 100; max current of 50A. It features
a pulse generator that allows the load to be
modulated with excursions in both magnitude,
frequency and duration. I've not enjoyed this
capability since the last regulator I did for
Beech about a bazillion years ago.
It also has a scaled current sample port that
will drive my oscilloscope. This instrument will
be invaluable for evaluating a box of 'funky'
fuses.
I will suggest there are two experiments to be
designed and conducted. (1) compare interruption
characteristics of the funky fuses with some
name brand devices -and- their data sheets. (2)
craft an experiment that attempts to set a
wire on fire . . . or at least cause a level of
destruction that generates expensive repairs if
not risks to comfortable completions of flight.
Things are moving ahead with the test stand.
How would we set up the experiment for demise
of an 'inadequately' protected wire? Keep
in mind that my prodigal environmental chamber
has returned from a 20-year 'sabbatical' so our
experiment can include elevated environmental
temperature effects.
Bob . . .
////
(o o)
===========o00o=(_)=o00o=========
< Go ahead, make my day . . . >
< show me where I'm wrong. >
=================================
In the interest of creative evolution
of the-best-we-know-how-to-do based
on physics and good practice.
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