Today's Message Index:
----------------------
1. 10:15 AM - Re: Potential for Overvoltage Issue (Robert L. Nuckolls, III)
2. 10:31 AM - Re: OVM14 MkIII, rev P1 (user9253)
Message 1
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| Subject: | Re: Potential for Overvoltage Issue |
At 10:01 AM 9/27/2023, you wrote:
>Hi Bob,
>
>Thanks for your response. But, remember in this case we are dealing
>with a user modified alternator, not factory.
. . .and your skill set is not equal to or greater
than 'factory'?
>The two failure events you list are linked in a chain so their
>probabilities can't be considered independently.
You can consider them in any manner that you wish.
>In this case, if the screw with it's insulating sleeve were to back
>out exposing
>it's threads the ring terminal or brush lug would only have to move 0.020"
>to make contact and cause a uncontrolled overvoltage event. The probability
>of that much movement in a high vibration environment is almost guaranteed.
We've discussed the value of high pressure, gas tight
connections to insure conductor integrity . . . how likely
is it that this terminal, having succumbed to a 'high vibration'
environment and now flailing around in the breeze
is going to experience the necessary force/area PLUS dwell time to form
a conduction pathway necessary to produce the condition
of concern?
>I do agree that making that event extremely improbable so that it
>doesn't need to be
>considered is the best approach. I believe I had put Loctite on that screw.
Locking fasteners are good too . . .
>I think the next time I'm in there I will put a blob of JB-Weld over the screw
>and terminal, potting the area, as a belt and suspenders to make
>sure that it never moves.
Seems you have answered your own question. If
you have concerns and perceive a mitigating
action, then by all means. My offering to this
thread suggests that quality of workmanship
and robust design are the first lines of defence
for failures . . . OV management systems are a
'band aid' that addresses conditions for which
we have no influence on design/craftsmanship.
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.
Message 2
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| Subject: | Re: OVM14 MkIII, rev P1 |
A wise man once said, "That popped circuit breaker just prevented a fire.
Do you want to reset it and give the fire a second chance?"
Adding a 50 cent TO-92 part and a LED could save much time troubleshooting the
cause of the tripped breaker.
More importantly, if the LED is illuminated, the pilot will know that it is safe
to reset the breaker.
If the LED is off, then it is best to wait until safely on the ground before resetting
the breaker.
The suggested LED has a narrow beam angle and should be aimed toward the pilot's
face.
I modified Bob N's circuit below by adding an SCR and external LED circuit. And
thanks Eric for your help.
--------
Joe Gores
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=511525#511525
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