Today's Message Index:
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1. 04:56 AM - Re: Re: faston failures et. als. (Steve Kelly)
2. 08:04 AM - Re: Melted battery contractor ground wire (morsegarrett)
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| Subject: | Re: re: faston failures et. als. |
Bob,
Thanks for you're thoughts on this. The picture of the darkened terminal
was exactly what mine looked like. My strobes are on every flight. About
300 hours now. Something I will be watching. One question though. What
might total failure look like? Blown fuse? Smoke?
Steve
On Thu, Jul 29, 2021 at 8:06 PM Robert L. Nuckolls, III <
nuckolls.bob@aeroelectric.com> wrote:
> At 10:02 AM 7/27/2021, you wrote:
>
> The issue of female "fast on" connectors losing their grip and creating a
> high resistance point is generally related to the quality of the connectors
> used. The connectors sold at the local auto parts stores are of inferior
> quality and often cause this sort of issue. Best to use the PIDG connectors
> that Bob N. recommends.
>
>
> We've had several incidents of strobe switch failures
> over the years. Had a builder report serial
> failures on his airplane that took some time and
> head scratching to figure out. This was probably
> 20 years ago.
>
> http://aeroelectric.com/Pictures/Switches/Carling_Cutaway.jpg
>
>
> http://aeroelectric.com/Pictures/Switches/Toggle_Switch_with_Fast-On_Tabs.jpg
>
> If you study the images above you can plot the
> pathway for current flow through the switch. Note
> that there are 10 'ohmic' joints in (metal-to-metal)
> the wire-to-wire pathway. There are 11 conductive
> components that carry current to, through and
> away from the switch.
>
> Two of those joints are moving . . . saddle pivot
> and contact interface. All the rest are non-moving
> wherein various fabrication processes strive for
> gas-tight, low resistance joining.
>
> Loss of function for this assembly can have beginnings
> at any one or combination of failures in the ohmic
> joints. Degradation of a joint manifests in an
> increase of resistance between the two components.
>
> Increased resistance is followed by HEATING . . . just
> a few degrees at first . . . but it's regenerative.
> Heating exacerbates loss of conduction causing
> increased heating which accelerates lost of conduction.
>
> It's never a rapid process . . . it may take many
> hours of operation to bring the whole thing down
> to failure. Impending failures are often caught
> visually . . . note the discoloration of the terminal
> insulator here:
>
> http://aeroelectric.com/Pictures/Switches/VL_Switch_Failure_2.jpg
>
> This image suggests loss of integrity in the terminal-
> to-wire crimp. Overt failure may still be months
> off after hours of operation.
>
> Modern flash tube strobe systems are particularly
> prone to failures of this kind. Several compounding
> reasons. (1) strobes are often operated for duration
> of flight from engine start up to shut down. (2) The
> flash tube strobe system is probably the most demanding
> on the panel switch due to current draw . . . a draw
> that is HIGHEST at low bus voltages when the modern,
> constant power high voltage circuits INCREASE drain
> to maintain performance.
>
> We've studied several switch failure cases here on
> the List over the years. EVERY failure began with localized
> heating as a consequence of degraded conduction in ONE
> joint. It was not uncommon for heating to degrade surrounding
> materials to the point where multiple joints began to
> participate in total failure of the switch.
>
> Failure science is an interesting study in material
> characteristics and physics. Without a well considered
> study of evidence, it's easy to blame the quality of
> a component but one needs to be mindful of the
> general nature of failures. They generally have
> a single point of origin that can cascade into
> multiple events ending in total failure.
>
>
> Bob . . .
>
> Un impeachable logic: George Carlin asked, "If black boxes
> survive crashes, why don't they make the whole airplane
> out of that stuff?"
>
Message 2
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| Subject: | Re: Melted battery contractor ground wire |
I think this is not unusual. You don't have to worry too much to it
fireboy and watergirl (https://fireboyandwatergirl.onl)
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=502841#502841
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