Today's Message Index:
----------------------
1. 07:19 AM - Z101 Fuseable link question (jcohen@post.com)
2. 08:02 AM - Re: Z101 Fuseable link question (Charlie England)
3. 08:42 AM - Re: Protecting the fat wires (Robert L. Nuckolls, III)
4. 09:13 AM - Re: Z101 Fuseable link question (Robert L. Nuckolls, III)
5. 09:19 AM - Re: Z101 Fuseable link question (Robert L. Nuckolls, III)
6. 10:58 AM - Re: Intermittent Charging (Robert L. Nuckolls, III)
7. 12:19 PM - Re: Z101 Fuseable link question (jcohen@post.com)
8. 02:46 PM - Re: Re: Z101 Fuseable link question (Robert L. Nuckolls, III)
Message 1
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| Subject: | Z101 Fuseable link question |
On reviewing Mudfly's Schematics, and the Z101 Rev b, I have a basic question on
the implementation of fusible links for the power feed wire from the main power
bus to the bus input (pin 6) on the LR-3 (via the Master Switch).
1. Z101 has 20AWG wire for this line, but the fusible link appears to be 20FLW(#)
using 16AWG? Shouldn't this be a 24AWG fusible link to protect a 20AWG wire?
Is this a typo or, as I am learning with Z101 and Bob's excellent work, is there
a good reason for this? Am I mistaken on what fusible link nomenclature 20FLW(#)-16AWG
means? Does the Breaker in-line on this wire affect the FLW selection?
2. Mudfly appears to be using 18AWG for the above wire, but the same fusible link
setup. Is this correct?
3. One more question: If protection of the Alternator B line is important but for
a very rare event, why bother with ANL devices that need space on a firewall,
when fusible links are clearly simpler, lighter, cheaper, and most likely more
reliable?
Thank you for your help educating me on this stuff.
--------
Jeff
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=510346#510346
Message 2
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| Subject: | Re: Z101 Fuseable link question |
On 3/6/2023 9:19 AM, jcohen@post.com wrote:
>
> On reviewing Mudfly's Schematics, and the Z101 Rev b, I have a basic question
on the implementation of fusible links for the power feed wire from the main
power bus to the bus input (pin 6) on the LR-3 (via the Master Switch).
>
> 1. Z101 has 20AWG wire for this line, but the fusible link appears to be 20FLW(#)
using 16AWG? Shouldn't this be a 24AWG fusible link to protect a 20AWG wire?
Is this a typo or, as I am learning with Z101 and Bob's excellent work, is
there a good reason for this? Am I mistaken on what fusible link nomenclature
20FLW(#)-16AWG means? Does the Breaker in-line on this wire affect the FLW selection?
>
> 2. Mudfly appears to be using 18AWG for the above wire, but the same fusible
link setup. Is this correct?
>
> 3. One more question: If protection of the Alternator B line is important but
for a very rare event, why bother with ANL devices that need space on a firewall,
when fusible links are clearly simpler, lighter, cheaper, and most likely
more reliable?
>
> Thank you for your help educating me on this stuff.
>
> --------
I'm not looking at either drawing at the moment, but I'd bet that #1 is
because 24AWG wire is pretty fragile, and relatively uncommon in small
a/c anyway. Not sure why Bob picked 20/16 in that spot instead of 22/18,
unless it was to keep some level of commonality with other wires already
spec'd in the system, or perhaps to minimize voltage drop which might
affect regulation stability in the regulator.
For #3, I used 12AWG link wire for the link and 8AWG welding cable for
the B-lead, on 55A alternators. B-lead length is pretty short on my
installation; probably around 2 feet for each alternator (alternative
engine with both alts on the accessory end of the engine). I really like
using the link wire, to save weight, number of connections, money, etc.
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Message 3
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| Subject: | Re: Protecting the fat wires |
>>Hello all! This is my first time posting on this list so I'd
>>like to introduce myself and say hello.
Welcome aboard!
>>How do you determine which fat wires need circuit protection of some sort?
>>All of the branch circuits off of a bus get a fuse or a breaker,
>>but what about
>>the wires feeding the busses from the contactors?
>>Somebody pointed out, and I do remember reading, that the fat wires will
>>ground to airframe and burn a hole rather than burning the wire itself.
>>It seems to me that the airframe is the fuse. Why not just use an ANL?
Good question. Ground faults on FAT wires (distribution
feeders at risk ONLY from energy supplied by a battery)
tend to be 'soft' faults. Insulation is compromised
by installation error, terminal falls of it's stud,
etc. Soft faults are relatively high resistance and
perhaps even intermittent. Hence they can generate
a lot of heat that is likely to melt/burn the airframe
as opposed to the wire. (Recall the elevator cable
failure on the C90 in New Mexico).
I've witnessed a boat-load of soft faults that did
not open the upstream circuit protection. Most were
INSIDE an appliance . . . much smoke came out of a
pump motor, radio, etc. without popping a breaker.
The singular purpose for ANL/FWL current limiting
is to mitigate the effects of a HARD fault where
the at-risk conductor gets firmly connected to
ground (no arcing, no heat) and suffers the abuse
possible from an energetic current source . . .
ALWAYS the battery.
Faults of this type a generally limited to
situations were the airframe is pretty badly
munched. An associate of mine at Raytheon/Beech
served many years as an accident investigator.
He used to offer the notion that many post
crash fires involved airplanes where the battery
was contained in the wreckage . . . if the
airplane did not burn, the battery was often
found 'out in the weeds'.
Anecdotal to be sure but illustrative of the
potential for large energy releases from an
airworthy battery. It's not a good idea to
mess with momma bear. It's an equally bad
idea to mess with daddy battery!
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 4
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| Subject: | Re: Z101 Fuseable link question |
At 09:19 AM 3/6/2023, you wrote:
>
>On reviewing Mudfly's Schematics, and the Z101 Rev b, I have a
>basic question on the implementation of fusible links for
>the power feed wire from the main power bus to the bus
>input (pin 6) on the LR-3 (via the Master Switch).
Yes, RevB to Z101 corrected an oversight in
depiction of the BUS EXTENSION from the main
bus feeder out to the circuit breaker dictated
by incorporation of a crowbar ov management
system.
The segment from FAT wires out to the breaker
is a distribution feature that COULD be serviced
by a 24FWL driving a 20AWG feeder. Fusible
link wire is not common available in sizes less
than 20 which dictates a feeder of 16AWG or
larger. This is a one-of-a-kind situation so
I wouldn't work too hard to get a hunk of 16AWG
for that segment. 14 or even 12 would be fine
to.
Once past the breaker, the pathway becomes
an appliance feeder with wire sizes suggested
by installation requirements for that appliance.
>1. Z101 has 20AWG wire for this line, but the fusible link appears
>to be 20FLW(#) using 16AWG?
No, that's 20FWL fusible link wire . . .
https://tinyurl.com/2p9eyv46
spliced onto a 16AWG (or larger) extension
out to the breaker. That dot with an X thru
it is a splice.
>Shouldn't this be a 24AWG fusible link to protect a 20AWG wire? Is
>this a typo or, as I am learning with Z101 and Bob's excellent work,
>is there a good reason for this? Am I mistaken on what fusible link
>nomenclature 20FLW(#)-16AWG means? Does the Breaker in-line on this
>wire affect the FLW selection?
Link selection in this case is driven by
product availability. Now, you COULD build
your own 24FWL
http://aeroelectric.com/articles/fuselink/fuselink.html
. . . acquiring he fiberglas/silicone sleeving
is probably more effort than off-the-shelf
fusible link wire.
>3. One more question: If protection of the Alternator B line is important
>but for a very rare event, why bother with ANL devices that need space
>on a firewall, when fusible links are clearly simpler, lighter, cheaper,
>and most likely more reliable?
Very perceptive. But of course. The car guys have
been doing this for decades. My KIA has a cluster
of circuit protective devices right at the battery(+)
terminal. They look like mini ANL current limiters.
The wiring diagram calls the 'fusible links'.
The fact that these could not get any closer to
the battery terminal should suggest something
about battery energy hazards in a munch-up.
Back in our EMT days, one of the FIRST things
the jaws-of-life guys did on arrival at the
scene was cut the battery wires . . . assuming
they could be reached.
>Thank you for your help educating me on this stuff.
That's what we're here for my friend.
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 5
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| Subject: | Re: Z101 Fuseable link question |
>I'm not looking at either drawing at the moment, but I'd bet that #1
>is because 24AWG wire is pretty fragile, and relatively uncommon in
>small a/c anyway. Not sure why Bob picked 20/16 in that spot instead
>of 22/18, unless it was to keep some level of commonality with other
>wires already spec'd in the system, or perhaps to minimize voltage
>drop which might affect regulation stability in the regulator.
20AWG linkwire is the the smallest off-the-shelf
product I've located thus far. If anyone spots
something smaller, please give the List a
heads-up.
But it's not a really pressing issue. The 20/16
FAT wire extension satisfies crash safety design
goals . . . the fact that it's a bit 'big' for
a 5A feeder is no big deal. If that were a 2 AMP
breaker protecting some device on the airframe,
the 20/16 extension would still be just fine.
>I really like using the link wire, to save weight, number
>of connections, money, etc.
Agreed . . . I'd rather install a fist full
of butt-splices than one ANL mounting block!
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 6
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| Subject: | Re: Intermittent Charging |
At 08:16 PM 3/5/2023, you wrote:
>Another flight this morning with another regulator led to the same
>problem as previously. It charges on the ground and for a short time
>in the flight, then failure. Then black to charging upon landing
>and taxiing back to the hangar. I checked the engine ground
>and found nothing amiss, plus never a problem with cranking,
>indicating to me a robust ground.
Good data point.
>I was about to mount the regulator on the back of the alternator
>as Bob suggested, when a friend dropped by and said he had a spare
>alternator I could try. I got in a 30 minute flight and everything
>functioned properly. The radio noise was gone and the panel
>voltmeter stayed steady at ~14.5 volts. Never even a twitch of the
>needle. Not wanting to celebrate prematurely again, I'll give it
>another go tomorrow.
Good detective work. The original rabbit-hole
was attractive because time/temperature effects
are strongest in alternators. Regulators are
all solid state and generally quite robust
and long lived. That's why I was particularly
interested in doing a post mortem on your
'bad' regulator.
The really strong signal was the transient
alternator noise which would be one of two
conditions: (1) faulty ground system or (2)
loss-of-phase integrity in the stator-diodes
assembly.
I am skeptical of the parts-store alternator
testers to catch every possible failure . . .
especially those related to time/temperature
effects. Those benchtop test fixtures cannot
put out more than 1 hp or so . . . hence unable to
spin up an 60A alternator under full load.
They WILL spot bad diodes, brushes, shorted
windings, etc. under light loads but as you've
discovered . . . not capable of producing the
stress needed to trigger a time/temperature
fault.
> If all goes well again, it would be interesting to see what's
> inside the old alternator.
Indeed. I would not discourage you from exploring
that topic yourself. However, if you like I am
willing to take a peek at it also. Given that
your problem child is 15 years old, I suspect
that it's simply fallen to the effects of 'old
age'. That's not always the case . . .here's
one example of fresh-out-of-the-box alternators
suffering the effects of manufacturing
incompetence.
https://tinyurl.com/2pbxghtw
Good work!
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 7
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| Subject: | Re: Z101 Fuseable link question |
> 20AWG linkwire is the the smallest off-the-shelf
> product I've located thus far. If anyone spots
> something smaller, please give the List a
> heads-up.
well, if you have $9, this B&C Specialty Products kit works.
https://bandc.com/product/fusible-link-kit-24-20-awg/
maybe cheaper than trying to buy 6" of Silicone covered fiberglas sleeving on your
own.
--------
Jeff
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=510352#510352
Message 8
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| Subject: | Re: Z101 Fuseable link question |
At 02:18 PM 3/6/2023, you wrote:
>
>
> > 20AWG linkwire is the the smallest off-the-shelf
> > product I've located thus far. If anyone spots
> > something smaller, please give the List a
> > heads-up.
>
>
>well, if you have $9, this B&C Specialty Products kit works.
>
>https://bandc.com/product/fusible-link-kit-24-20-awg/
Yep, that works too. I used to sell that
kit wwaaaaayyyy back when . . .
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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