Today's Message Index:
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1. 05:36 AM - Re: Primary Power Diagram RV-14 (Mudfly)
2. 12:48 PM - Re: Master Relay Typical Resistance (long Story) (Robert L. Nuckolls, III)
3. 12:55 PM - Re: Replacing copper bar with tefzel wire (Robert L. Nuckolls, III)
Message 1
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| Subject: | Re: Primary Power Diagram RV-14 |
Small changes to the Primary Power System diagram.
Also added interconnect drawing for STBY Batteries.
Upated drawings attached.
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=510122#510122
Attachments:
http://forums.matronics.com//files/stby_batts_interconnect_drawing_824.pdf
http://forums.matronics.com//files/primary_power_system_948.pdf
Message 2
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| Subject: | Re: Master Relay Typical Resistance (long Story) |
At 09:48 AM 2/2/2023, you wrote:
>Is the master contactor physically hot after extended use? Might hold a clue?
A typical battery master contactor (Metal, 'whisky' barrel')
will start out cold with a current draw on the order
of 0.8A and drop to somewhere around 0.6A after it warms
up . . . and warm up it will.
0.6A at 14.5V is right at 9 Watts. In time, this
will raise the device temperature to something
on the order of 170F in still, room-temperature
air. It will probably not be nearly that warm in
your airplane. Hence, continuous operation current
will be a bit HIGHER than 0.6A.
Nonetheless, a NORMALLY operating contactor will
be too hot to touch. This is a GOOD thing. Your
contactor IS mounted cap-down and has an itty-
bitty drain hole in the cap? Warm ops go to drying
out the contactor's innards thus extending its
service life.
If voltage drop across the contactor's power path
is over 100 mV or so . . . and especially if it
VARIES with vibrational stimulus (rap it with the
handle of a screwdriver), the contacts are AGED
and the device should be replaced. This basket
carries a LOT of the systems 'eggs' but they're cheap.
You'll spend more $time$ fussing over its diagnosis
than the thing costs.
When in doubt, replace it.
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 3
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| Subject: | Re: Replacing copper bar with tefzel wire |
At 09:47 PM 2/3/2023, you wrote:
<jcohen@post.com>
>
>I am building a Vans RV7 , IO360, Z101, using
>B&C master and starter contactors, and an EarthX
>ETX 900 battery. I can=99t easily use the Vans
>design solution of 0.125=9D thick copper bar,
>about 3=9D long x 0.5=9D wide, to connect the
>master solenoid to the starter solenoid, due to
>physical placement on my firewall and the stud
>orientation on the B&C starter contactor. So I
>want to use an insulated wire instead of the bar, maybe only 4=9D or
so.
>
> >From old posts on vansAirforce.net forum, the
> current here is estimated to be up to 320 amps
> for short periods while cranking the starter.
> Is that correct? What gauge tefzel wire should
> I use to maintain the functionality and safety of the copper bar?
I'm skeptical of that current number . . . nonetheless,
a 4AWG piece of wire would be just fine. If you don't yet
have the wire, get a chunk of welding cable from a local
welding supplies shop. MUCH more flexible and installer
friendly. Be gentle on yourself too . . . don't make the
jumper run a tight, straight line between studs. Make
it a leisurely hop between mounting locations so that
you can exploit that flexibility; i.e. a 6" piece
of wire is about right for connecting studs 4" apart.
Bob . . .
Un impeachable logic: George Carlin asked, "If black boxes
survive crashes, why don't they make the whole airplane
out of that stuff?"
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