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rv8iator
Joined: 11 Apr 2006
Posts: 145
Location: Newberg, OR
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 Posted: Thu Dec 21, 2023 7:25 pm Post subject: Fusible links |
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In re-reading the AeroElectric connection section on fusible links, you refer to 3" to 6" length for the fusible section. Why can they not be, say 1" in length? Mostly concern for durability as they will need to be in an accessible area in the event they would need to be replaced.
...chris
ANother RV
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C. Stone (RV8iator) |
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finn.lassen(at)verizon.ne
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| Posted: Fri Dec 22, 2023 8:30 am Post subject: Fusible links |
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I think it depends on how you terminate it. With crimp terminations even
1/2" would be long enough.
However, if you solder it to adjacent wires it'll have to be long enough
that solder has not wicked into the stretch of wire that will act as a
fuse. My opinion is that added solder to a wire would add to the current
needed to melt it. I could be wrong.
Finn
On 12/21/2023 10:24 PM, Christopher Cee Stone wrote:
| Quote: | In re-reading the AeroElectric connection section on fusible links,
you refer to 3" to 6" length for the fusible section. Why can they
not be, say 1" in length? Mostly concern for durability as they will
need to be in an accessible area in the event they would need to be
replaced.
...chris
ANother RV
|
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user9253
Joined: 28 Mar 2008
Posts: 1925
Location: Riley TWP Michigan
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ashleysc(at)broadstripe.n
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| Posted: Fri Dec 22, 2023 9:29 am Post subject: Fusible links |
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Hi All;
I know this is going to create controversy, but I think fusible links are a crutch, and an unreliable one at that. Why utilize fusible links, when fuses themselves, are so inexpensive, more predictable, and easier to diagnose and change? If you look at modern automobile production, you won't find a single fusible link, but dozens of cheap, compact, and reliable automobile-type fuses.
Cheers! Stu.
---
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Ceengland
Joined: 11 Oct 2020
Posts: 391
Location: MS
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| Posted: Fri Dec 22, 2023 9:45 am Post subject: Fusible links |
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If you dig a little deeper, you might find quite a few fusible links in automotive use. The reason (place) to use them is typically when the only likely fault is a catastrophic one, like a wire shorted to ground, Fuses do have a fatigue life, which is for all practical purposes unlimited for a link wire. And in certain situations, using link wire can actually reduce mechanical connections. Particularly true for higher current situations that would otherwise require a separate 'current limiter' type device, and its mounting socket. Properly installed, links are going to be *more* reliable than an equivalent fuse + holder + terminations. With solder/heat shrink to the primary wire, they can add zero terminations to a wire run.
Charlie
On Fri, Dec 22, 2023 at 11:32 AM <ashleysc(at)broadstripe.net (ashleysc(at)broadstripe.net)> wrote:
[quote]--> AeroElectric-List message posted by: ashleysc(at)broadstripe.net (ashleysc(at)broadstripe.net)
Hi All;
I know this is going to create controversy, but I think fusible links are a crutch, and an unreliable one at that. Why utilize fusible links, when fuses themselves, are so inexpensive, more predictable, and easier to diagnose and change? If you look at modern automobile production, you won't find a single fusible link, but dozens of cheap, compact, and reliable automobile-type fuses.
Cheers!  Stu.
---
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Voyager
Joined: 30 Jun 2020
Posts: 77
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| Posted: Fri Dec 22, 2023 11:25 am Post subject: Fusible links |
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Why would a metal fuse have a fatigue life and a wire not?Sent from my iPad
[quote]On Dec 22, 2023, at 12:47 PM, Charlie England <ceengland7(at)gmail.com> wrote:
If you dig a little deeper, you might find quite a few fusible links in automotive use. The reason (place) to use them is typically when the only likely fault is a catastrophic one, like a wire shorted to ground, Fuses do have a fatigue life, which is for all practical purposes unlimited for a link wire. And in certain situations, using link wire can actually reduce mechanical connections. Particularly true for higher current situations that would otherwise require a separate 'current limiter' type device, and its mounting socket. Properly installed, links are going to be *more* reliable than an equivalent fuse + holder + terminations. With solder/heat shrink to the primary wire, they can add zero terminations to a wire run.
Charlie
On Fri, Dec 22, 2023 at 11:32 AM <ashleysc(at)broadstripe.net (ashleysc(at)broadstripe.net)> wrote:
[quote]--> AeroElectric-List message posted by: ashleysc(at)broadstripe.net (ashleysc(at)broadstripe.net)
Hi All;
I know this is going to create controversy, but I think fusible links are a crutch, and an unreliable one at that. Why utilize fusible links, when fuses themselves, are so inexpensive, more predictable, and easier to diagnose and change? If you look at modern automobile production, you won't find a single fusible link, but dozens of cheap, compact, and reliable automobile-type fuses.
Cheers! Stu.
---
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Ceengland
Joined: 11 Oct 2020
Posts: 391
Location: MS
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| Posted: Fri Dec 22, 2023 12:43 pm Post subject: Fusible links |
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If you've ever watched the element in a glass fuse when it's hit by a significant percentage of its rated current, you can often see it flex as it heats, expands, and then cools. The element is relatively small/short, its current handling is fairly close to its 'trip point', the ends are fixed, and the element is typically straight, so when it heats and expands, the extra length has to go somewhere. A link wire typically has a *lot* more current handling ability than a fuse (catastrophic failures only) so it won't heat/flex as much, and since we make them from stranded wire, if it does flex a bit it's much less likely to fail from heat-induced fatigue. Still needs to be supported properly, of course, just like any other wire.
On Fri, Dec 22, 2023 at 1:27 PM Matthew S. Whiting <m.whiting(at)frontier.com (m.whiting(at)frontier.com)> wrote:
[quote]Why would a metal fuse have a fatigue life and a wire not?Sent from my iPad
[quote]On Dec 22, 2023, at 12:47 PM, Charlie England <ceengland7(at)gmail.com (ceengland7(at)gmail.com)> wrote:
If you dig a little deeper, you might find quite a few fusible links in automotive use. The reason (place) to use them is typically when the only likely fault is a catastrophic one, like a wire shorted to ground, Fuses do have a fatigue life, which is for all practical purposes unlimited for a link wire. And in certain situations, using link wire can actually reduce mechanical connections. Particularly true for higher current situations that would otherwise require a separate 'current limiter' type device, and its mounting socket. Properly installed, links are going to be *more* reliable than an equivalent fuse + holder + terminations. With solder/heat shrink to the primary wire, they can add zero terminations to a wire run.
Charlie
On Fri, Dec 22, 2023 at 11:32 AM <ashleysc(at)broadstripe.net (ashleysc(at)broadstripe.net)> wrote:
[quote]--> AeroElectric-List message posted by: ashleysc(at)broadstripe.net (ashleysc(at)broadstripe.net)
Hi All;
I know this is going to create controversy, but I think fusible links are a crutch, and an unreliable one at that. Why utilize fusible links, when fuses themselves, are so inexpensive, more predictable, and easier to diagnose and change? If you look at modern automobile production, you won't find a single fusible link, but dozens of cheap, compact, and reliable automobile-type fuses.
Cheers!  Stu.
---
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Charlie |
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Voyager
Joined: 30 Jun 2020
Posts: 77
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| Posted: Fri Dec 22, 2023 1:05 pm Post subject: Fusible links |
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I haven’t seen a glass fused used in an auto or aviation application in probably 40 years. I am not aware of any fatigue issues with auto style blade fuses which is what most of use use in cars and airplanes.Sent from my iPad
[quote]On Dec 22, 2023, at 3:45 PM, Charlie England <ceengland7(at)gmail.com> wrote:
If you've ever watched the element in a glass fuse when it's hit by a significant percentage of its rated current, you can often see it flex as it heats, expands, and then cools. The element is relatively small/short, its current handling is fairly close to its 'trip point', the ends are fixed, and the element is typically straight, so when it heats and expands, the extra length has to go somewhere. A link wire typically has a *lot* more current handling ability than a fuse (catastrophic failures only) so it won't heat/flex as much, and since we make them from stranded wire, if it does flex a bit it's much less likely to fail from heat-induced fatigue. Still needs to be supported properly, of course, just like any other wire.
On Fri, Dec 22, 2023 at 1:27 PM Matthew S. Whiting <m.whiting(at)frontier.com (m.whiting(at)frontier.com)> wrote:
[quote]Why would a metal fuse have a fatigue life and a wire not?Sent from my iPad
[quote]On Dec 22, 2023, at 12:47 PM, Charlie England <ceengland7(at)gmail.com (ceengland7(at)gmail.com)> wrote:
If you dig a little deeper, you might find quite a few fusible links in automotive use. The reason (place) to use them is typically when the only likely fault is a catastrophic one, like a wire shorted to ground, Fuses do have a fatigue life, which is for all practical purposes unlimited for a link wire. And in certain situations, using link wire can actually reduce mechanical connections. Particularly true for higher current situations that would otherwise require a separate 'current limiter' type device, and its mounting socket. Properly installed, links are going to be *more* reliable than an equivalent fuse + holder + terminations. With solder/heat shrink to the primary wire, they can add zero terminations to a wire run.
Charlie
On Fri, Dec 22, 2023 at 11:32 AM <ashleysc(at)broadstripe.net (ashleysc(at)broadstripe.net)> wrote:
[quote]--> AeroElectric-List message posted by: ashleysc(at)broadstripe.net (ashleysc(at)broadstripe.net)
Hi All;
I know this is going to create controversy, but I think fusible links are a crutch, and an unreliable one at that. Why utilize fusible links, when fuses themselves, are so inexpensive, more predictable, and easier to diagnose and change? If you look at modern automobile production, you won't find a single fusible link, but dozens of cheap, compact, and reliable automobile-type fuses.
Cheers! Stu.
---
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Ceengland
Joined: 11 Oct 2020
Posts: 391
Location: MS
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| Posted: Fri Dec 22, 2023 1:36 pm Post subject: Fusible links |
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Glass was mentioned because you can see it happen; not to say that they're
still used.
We can agree to disagree on the rest if you like...
<https://www.avast.com/sig-email?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_content=webmail>
Virus-free.www.avast.com
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On Fri, Dec 22, 2023 at 3:07 PM Matthew S. Whiting <m.whiting(at)frontier.com>
wrote:
[quote] I haven’t seen a glass fused used in an auto or aviation application in
probably 40 years. I am not aware of any fatigue issues with auto style
blade fuses which is what most of use use in cars and airplanes.
Sent from my iPad
On Dec 22, 2023, at 3:45 PM, Charlie England <ceengland7(at)gmail.com> wrote:

If you've ever watched the element in a glass fuse when it's hit by a
significant percentage of its rated current, you can often see it flex as
it heats, expands, and then cools. The element is relatively small/short,
its current handling is fairly close to its 'trip point', the ends are
fixed, and the element is typically straight, so when it heats and expands,
the extra length has to go somewhere. A link wire typically has a *lot*
more current handling ability than a fuse (catastrophic failures only) so
it won't heat/flex as much, and since we make them from stranded wire, if
it does flex a bit it's much less likely to fail from heat-induced fatigue.
Still needs to be supported properly, of course, just like any other wire
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Charlie |
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finn.lassen(at)verizon.ne
Guest
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| Posted: Fri Dec 22, 2023 1:54 pm Post subject: Fusible links |
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Maybe not fatigue but definitely corrosion. Spent way too much time troubleshooting my 1988 Chevy S10 only to find a blade fuse with corroded terminals-- acted as a resistor.
And I stand corrected on my take on the length of a fusible link. I did not consider the effect of adjacent thicker wires leading away heat.
Finn
On 12/22/2023 4:04 PM, Matthew S. Whiting wrote:
[quote] I haven’t seen a glass fused used in an auto or aviation application in probably 40 years. I am not aware of any fatigue issues with auto style blade fuses which is what most of use use in cars and airplanes. Sent from my iPad
[quote]On Dec 22, 2023, at 3:45 PM, Charlie England <ceengland7(at)gmail.com> (ceengland7(at)gmail.com) wrote:
 If you've ever watched the element in a glass fuse when it's hit by a significant percentage of its rated current, you can often see it flex as it heats, expands, and then cools. The element is relatively small/short, its current handling is fairly close to its 'trip point', the ends are fixed, and the element is typically straight, so when it heats and expands, the extra length has to go somewhere. A link wire typically has a *lot* more current handling ability than a fuse (catastrophic failures only) so it won't heat/flex as much, and since we make them from stranded wire, if it does flex a bit it's much less likely to fail from heat-induced fatigue. Still needs to be supported properly, of course, just like any other wire.
On Fri, Dec 22, 2023 at 1:27 PM Matthew S. Whiting <m.whiting(at)frontier.com (m.whiting(at)frontier.com)> wrote:
[quote] Why would a metal fuse have a fatigue life and a wire not? Sent from my iPad
[quote]On Dec 22, 2023, at 12:47 PM, Charlie England <ceengland7(at)gmail.com (ceengland7(at)gmail.com)> wrote:
 If you dig a little deeper, you might find quite a few fusible links in automotive use. The reason (place) to use them is typically when the only likely fault is a catastrophic one, like a wire shorted to ground, Fuses do have a fatigue life, which is for all practical purposes unlimited for a link wire. And in certain situations, using link wire can actually reduce mechanical connections. Particularly true for higher current situations that would otherwise require a separate 'current limiter' type device, and its mounting socket. Properly installed, links are going to be *more* reliable than an equivalent fuse + holder + terminations. With solder/heat shrink to the primary wire, they can add zero terminations to a wire run.
Charlie
On Fri, Dec 22, 2023 at 11:32 AM <ashleysc(at)broadstripe.net (ashleysc(at)broadstripe.net)> wrote:
[quote]--> AeroElectric-List message posted by: ashleysc(at)broadstripe.net (ashleysc(at)broadstripe.net)
Hi All;
I know this is going to create controversy, but I think fusible links are a crutch, and an unreliable one at that. Why utilize fusible links, when fuses themselves, are so inexpensive, more predictable, and easier to diagnose and change? If you look at modern automobile production, you won't find a single fusible link, but dozens of cheap, compact, and reliable automobile-type fuses.
Cheers!  Stu.
---
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nuckolls.bob(at)aeroelect
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| Posted: Fri Dec 22, 2023 3:16 pm Post subject: Fusible links |
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At 11:29 AM 12/22/2023, you wrote:
| Quote: | --> AeroElectric-List message posted by: ashleysc(at)broadstripe.net
Hi All;
I know this is going to create controversy, but I think fusible links are a crutch, and an unreliable one at that. Why utilize fusible links, when fuses themselves, are so inexpensive, more predictable, and easier to diagnose and change? If you look at modern automobile production, you won't find a single fusible link, but dozens of cheap, compact, and reliable automobile-type fuses.
Cheers! |
A fusible link is not a 'fuse'. It's not as finely
calibrated as fuses. It's in the same class of
fault protection as a ANL current limiter. See:
https://tinyurl.com/k7o3l3q
Note a 100A version of this device will carry
200A for about 12 seconds! This is typical
of all such devices in this class of protection.
Automobiles have been fitted with fusible links
as specially insulated WIRE for decades. The
auto parts stores carry replacement links . . .
not rated in amps but in AWG wire size. Modern
cars have migrated to miniature 'cartridge'
limiters such as the MIDI series from Littlefuse:
http://tinyurl.com/4av7s3ya
Note that a MIDI30 is rated to carry 200A
for 200mS; 60A for 8S and 40A for essentially
forever.
The purpose and application for such devices
is to protect extended BUS STRUCTURES from
battery excited, HARD FAULTS generally expected
to be many times the device's 'rating'.
This is why you do not see them sprinkled about
the Z-figures. I use them to extend a bus to
the crowbar circuit breaker, protect the alternator
B-lead from shorts in the diode array, protect
the feeder to an auxiliary bus which will support
fuses and or breakers to individual appliances.
Fusible link technology is widely exploited
in DC power systems of all stripes. Pre-assembled
fusible links as well as bulk wire (special
insulation) are offered by the likes of Mouser,
eBay, Amazon, virtually ALL auto parts stores,
etc.
https://tinyurl.com/yllq8uym
Don't conflate the words 'fuse' and 'fusible'.
Fuses are fusible but fusible links are not
fuses. I prefer them to ANL/MIDI solutions
for their simplicity . . . a piece of
specially insulated wire will mitigate
and contain the energies of a fusing event.
Can't beat them for cost, size, weight, labor,
etc.
But don't use them where a circuit breaker
or fuse is called for . . . that's a
different task altogether.
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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nuckolls.bob(at)aeroelect
Guest
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| Posted: Fri Dec 22, 2023 6:04 pm Post subject: Fusible links |
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At 03:04 PM 12/22/2023, you wrote:
| Quote: | | I haven’t seen a glass fused used in an auto or aviation application in probably 40 years. I am not aware of any fatigue issues with auto style blade fuses which is what most of use use in cars and airplanes. |
Yeah, those critters were equally vulnerable to
thermal 'hammering' . . .
Recall the Lancair Accident analysis I published
on the website. Critical FUSES were thermally
'stressed' numerous times at levels which deformed
the metal without melting. These repeated events
caused the fuse melt-current to be depressed.
After enough events had transpired . . . COMBINED
with elevate ambient temperatures under the cowl,
the fuse finally opened up and killed the engine.
Recall our discussions here on the list about
the temperature vs. phase of solder. As the
temperature rises, there's a fairly narrow
point at which the material changes from
solid to plastic. Meaning that ever smaller
forces are exceed tensile strength thus
changing its shape. In the case of fuses, the
force might be vibration, acceleration due
to motion or just plain gravity.
The point is that excursions into plasticity,
no matter how deep and how long can cause the
material to take on a new shape. That means
a 5A fuse might now become a 4.99A fuse . . .
or 4.9 . . . or 4.7.
It all depends on duration, amplitude
and number of temperature excursion.
It matters not how fast these excursions
occur. They are accumulative whether over
mere minutes or months.
In the case of the Lancair IVP's demise,
a series of excursions took out
one and then a second fuse. An error in
architecture negated failure tolerance
and the engine quit.
Fuses are may be operated rather closely
to their ultimate melting point but
common practice dictates that for steady
state loads with no aberrations, the
device should not be loaded to greater
than 80% or so of rating. If the load
presents any startup or momentary surges
of current, then further de-rating is
called for.
Automobile fusing philosophy is a good
case in point. I've noted numerous instances
where the fuse seemed really big compared
to load . . . but the task is to protect
wire. An 'oversized' fuse represents no
hazard.
Fusible links are the ultimate example of
OVERSIZED fusing. The wire is protected
from catastrophic faults . . . but the
link itself isn't even breathing hard.
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.
| | - The Matronics AeroElectric-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
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rv8iator
Joined: 11 Apr 2006
Posts: 145
Location: Newberg, OR
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| Posted: Sat Dec 23, 2023 7:32 am Post subject: Fusible links |
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Back to the original question of the length of a fusible link. That is the length of smaller gauge wire comprising the 'link'.
The premise being that a dead short of the fusible link protected wire would see the full system power supplied by, battery and/or alternator sources. Thus the 'link' would see in the case of the battery maybe 200 amps. In the case of alternator alone (assuming battery failure) 60 amps. Thus a 24 awg link would fail pretty quickly as the heating would be (and I'm taking a swag here) instantaneous or at most 2- 3 seconds to burn through. If the 'link' were 2" rather than 6" some head would be conducted into the connecting conductor which is 18 awg with PIDG splices. But the 'link' would still fail. As it is encased in a fibreglass sleeve, no harm other than the smell of burnt tefzel.
The specific application here are the E-mag power wires which e-magair specs call for 18 awg. One from the battery bus and one from the primary bus.
Pending the conclusions of this paper study I will go to the bench and test. I have created electrical systems for a number of aircraft using 2" fusible links. If there is a problem with this length I will recall my work and make the necessary revisions.
...chris
RV's and Kitfoxes
On Fri, Dec 22, 2023 at 3:19 PM Robert L. Nuckolls, III <nuckolls.bob(at)aeroelectric.com (nuckolls.bob(at)aeroelectric.com)> wrote:
| Quote: | At 11:29 AM 12/22/2023, you wrote:
| Quote: | --> AeroElectric-List message posted by: ashleysc(at)broadstripe.net (ashleysc(at)broadstripe.net)
Hi All;
I know this is going to create controversy, but I think fusible links are a crutch, and an unreliable one at that. Why utilize fusible links, when fuses themselves, are so inexpensive, more predictable, and easier to diagnose and change? If you look at modern automobile production, you won't find a single fusible link, but dozens of cheap, compact, and reliable automobile-type fuses.
Cheers! |
  A fusible link is not a 'fuse'. It's not as finely
  calibrated as fuses. It's in the same class of
  fault protection as a ANL current limiter. See:
https://tinyurl.com/k7o3l3q
  Note a 100A version of this device will carry
  200A for about 12 seconds! This is typical
  of all such devices in this class of protection.
  Automobiles have been fitted with fusible links
  as specially insulated WIRE for decades. The
  auto parts stores carry replacement links . . .
  not rated in amps but in AWG wire size. Modern
  cars have migrated to miniature 'cartridge'
  limiters such as the MIDI series from Littlefuse:
http://tinyurl.com/4av7s3ya
  Note that a MIDI30 is rated to carry 200A
  for 200mS; 60A for 8S and 40A for essentially
  forever.
  The purpose and application for such devices
  is to protect extended BUS STRUCTURES from
  battery excited, HARD FAULTS generally expected
  to be many times the device's 'rating'.
  This is why you do not see them sprinkled about
  the Z-figures. I use them to extend a bus to
  the crowbar circuit breaker, protect the alternator
  B-lead from shorts in the diode array, protect
  the feeder to an auxiliary bus which will support
  fuses and or breakers to individual appliances.
  Fusible link technology is widely exploited
  in DC power systems of all stripes. Pre-assembled
  fusible links as well as bulk wire (special
  insulation) are offered by the likes of Mouser,
  eBay, Amazon, virtually ALL auto parts stores,
  etc.
https://tinyurl.com/yllq8uym
  Don't conflate the words 'fuse' and 'fusible'.
  Fuses are fusible but fusible links are not
  fuses. I prefer them to ANL/MIDI solutions
  for their simplicity . . . a piece of
  specially insulated wire will mitigate
  and contain the energies of a fusing event.
  Can't beat them for cost, size, weight, labor,
  etc.
  But don't use them where a circuit breaker
  or fuse is called for . . . that's a
  different task altogether.
 Bob . . .
                  ////
                 (o o)
  ===========o00o=(_)=o00o=========
  < Go ahead, make my day . . .  >
  < show me where I'm wrong.     >
  =================================
Â
  In the interest of creative evolution
  of the-best-we-know-how-to-do based
  on physics and good practice.
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nuckolls.bob(at)aeroelect
Guest
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| Posted: Sat Dec 23, 2023 8:00 am Post subject: Fusible links |
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At 09:31 AM 12/23/2023, you wrote:
| Quote: | | Back to the original question of the length of a fusible link. That is the length of smaller gauge wire comprising the 'link'. |
Had to do some 'digging' to see if I could
find where that 3-6 inch citation came from.
No joy.
Actually, 6" is the minimum. 9" is more typical,
10" not unheard of. 3" is too short . . .
. . . and INSULATED with material resistant to
energy released by clearing the fault.
See: http://tinyurl.com/4vnzdjpc
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.
| | - The Matronics AeroElectric-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
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rv8iator
Joined: 11 Apr 2006
Posts: 145
Location: Newberg, OR
|
| Posted: Sat Dec 23, 2023 8:28 am Post subject: Fusible links |
|
|
The Delphi spec does not indicate length. Really is' material properties not performance characteristics.
I will do a couple of tests with varying "link" lengths using a fully charged 12v, group 24, new lead acid battery. (I happen to have a new one in the shop)
Unfortunately I don't have a recording scope at the moment... so this will have to be an empirical test. That is, what is the failure mode, not time to 'link' open.
Test specimens: 24 awg tefzel wire 'links', connected to 18 awg feeder using PIDG butt splices, fibreglass sleeve.
'link' lengths in inches: 2,3,6,12
Comments/suggestions are welcomed!
I will post results in the coming days.
...chris
On Sat, Dec 23, 2023 at 8:02 AM Robert L. Nuckolls, III <nuckolls.bob(at)aeroelectric.com (nuckolls.bob(at)aeroelectric.com)> wrote:
| Quote: | At 09:31 AM 12/23/2023, you wrote:
| Quote: | | Back to the original question of the length of a fusible link. That is the length of smaller gauge wire comprising the 'link'. |
 Had to do some 'digging' to see if I could
 find where that 3-6 inch citation came from.
 No joy.
 Actually, 6" is the minimum. 9" is more typical,
 10" not unheard of. 3" is too short . . .
 . . . and INSULATED with material resistant to
 energy released by clearing the fault.
 See: http://tinyurl.com/4vnzdjpc
 Bob . . .
                  ////
                 (o o)
  ===========o00o=(_)=o00o=========
  < Go ahead, make my day . . .  >
  < show me where I'm wrong.     >
  =================================
Â
  In the interest of creative evolution
  of the-best-we-know-how-to-do based
  on physics and good practice.
|
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Ceengland
Joined: 11 Oct 2020
Posts: 391
Location: MS
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| Posted: Sat Dec 23, 2023 8:46 am Post subject: Fusible links |
|
|
Only thought is that the normal 'spread' is 4; not 6. 22 for 18, 20 for 16, etc. OTOH, testing might show that if using a really short link, using a wider spread might be helpful, because the shorter length is going to reduce system heating.
 Virus-free.www.avast.com[url=#DAB4FAD8-2DD7-40BB-A1B8-4E2AA1F9FDF2][/url]
On Sat, Dec 23, 2023 at 10:30 AM Christopher Cee Stone <rv8iator(at)gmail.com (rv8iator(at)gmail.com)> wrote:
| Quote: | The Delphi spec does not indicate length. Really is' material properties not performance characteristics.
I will do a couple of tests with varying "link" lengths using a fully charged 12v, group 24, new lead acid battery. (I happen to have a new one in the shop)
Unfortunately I don't have a recording scope at the moment... so this will have to be an empirical test. That is, what is the failure mode, not time to 'link' open.
Test specimens: 24 awg tefzel wire 'links', connected to 18 awg feeder using PIDG butt splices, fibreglass sleeve.
'link' lengths in inches: 2,3,6,12
Comments/suggestions are welcomed!
I will post results in the coming days.
...chris
On Sat, Dec 23, 2023 at 8:02 AM Robert L. Nuckolls, III <nuckolls.bob(at)aeroelectric.com (nuckolls.bob(at)aeroelectric.com)> wrote:
| Quote: | At 09:31 AM 12/23/2023, you wrote:
| Quote: | | Back to the original question of the length of a fusible link. That is the length of smaller gauge wire comprising the 'link'. |
 Had to do some 'digging' to see if I could
 find where that 3-6 inch citation came from.
 No joy.
 Actually, 6" is the minimum. 9" is more typical,
 10" not unheard of. 3" is too short . . .
 . . . and INSULATED with material resistant to
 energy released by clearing the fault.
 See: http://tinyurl.com/4vnzdjpc
 Bob . . .
                  ////
                 (o o)
  ===========o00o=(_)=o00o=========
  < Go ahead, make my day . . .  >
  < show me where I'm wrong.     >
  =================================
Â
  In the interest of creative evolution
  of the-best-we-know-how-to-do based
  on physics and good practice.
|
|
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nuckolls.bob(at)aeroelect
Guest
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| Posted: Sat Dec 23, 2023 9:24 am Post subject: Fusible links |
|
|
At 10:27 AM 12/23/2023, you wrote:
| Quote: | | The Delphi spec does not indicate length. Really is' material properties not performance characteristics. |
There were TWO data points in that link . . .
One was a listing of manufactured links specific to
certain automotive applications:
https://tinyurl.com/yrgvc2er
Here we see lengths quoted from 8" to 10.5"
I've read other sources citing similar
lengths. Too short compromises the fusing
dynamic of which material properties a
part of the formula.
| Quote: | I will do a couple of tests with varying "link" lengths using a fully charged 12v, group 24, new lead acid battery. (I happen to have a new one in the shop)
Unfortunately I don't have a recording scope at the moment... so this will have to be an empirical test. That is, what is the failure mode, not time to 'link' open.
Test specimens: 24 awg tefzel wire 'links', connected to 18 awg feeder using PIDG butt splices, fibreglass sleeve.
'link' lengths in inches: 2,3,6,12 |
24AWG links are atypical of the devices in
common use. That combination of fiberglas over
24AWG was crafted in our shops about 30 years
ago as an alternative to cartridge fuses in the
leads between an b-lead shunt and a panel-ammeter.
I have no doubt that you will successfully 'fuse'
2" lengths of 24AWG . . . 100+ amps of battery
current pretty well predicts the outcome.
When I'm considering a 'bus extension' in
crafting an architecture, the decision considers
mechanical robustness and ease of reliable assembly.
For example, extending the bus out to a 5A crowbar
breaker might call for 20AWG fusible link driving
a 16AWG extension.
These are system segments NOT part of the
post crash fire safety considerations that call
for relatively small, FAST protection on always
hot circuits. 7A fuses work good in crash post
crash fire concerns.
Hence my design decision would lean toward easily
acquired, manufactured link material that behaves
well in PIDG crimps . . . there is no practical
motivation to consider 'amperage' values for
the links.
But having offered that, I'm interested in results
of your experiments. You can roughly control
the magnitude of fault current by how much 20AWG
wire is in series with your link. I'd shoot for
something on the order of 100A. 20AWG is 10mOHMs/foot.
Your battery will present a series impedance on the order
of 10 mOhm. So 5 feet of wire in the remainders of
the test loop would be about right.
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.
| | - The Matronics AeroElectric-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
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rv8iator
Joined: 11 Apr 2006
Posts: 145
Location: Newberg, OR
|
| Posted: Sat Dec 23, 2023 10:06 am Post subject: Fusible links |
|
|
...appreciate your discussion and input! Â
This discussion is the result of the addition of two E-mags to the current RV project and reviewing the Emag installation instruction. They call for a circuit breaker in series with the power feeder for the E-mag(s). I am using Z-13/8 as a reference guide for this build. I am considering a fusible link instead of a circuit breaker as I am running out of panel space. Thus my concern for both reliability and safety.
...chris
On Sat, Dec 23, 2023 at 9:26 AM Robert L. Nuckolls, III <nuckolls.bob(at)aeroelectric.com (nuckolls.bob(at)aeroelectric.com)> wrote:
| Quote: | At 10:27 AM 12/23/2023, you wrote:
| Quote: | | The Delphi spec does not indicate length. Really is' material properties not performance characteristics. |
 There were TWO data points in that link . . .
Â
 One was a listing of manufactured links specific to
 certain automotive applications:
https://tinyurl.com/yrgvc2er
 Here we see lengths quoted from 8" to 10.5"
 I've read other sources citing similar
 lengths. Too short compromises the fusing
 dynamic of which material properties a
 part of the formula.
| Quote: | I will do a couple of tests with varying "link" lengths using a fully charged 12v, group 24, new lead acid battery. (I happen to have a new one in the shop)
Unfortunately I don't have a recording scope at the moment... so this will have to be an empirical test. That is, what is the failure mode, not time to 'link' open.
Test specimens: 24 awg tefzel wire 'links', connected to 18 awg feeder using PIDG butt splices, fibreglass sleeve.
'link' lengths in inches: 2,3,6,12 |
 24AWG links are atypical of the devices in
 common use. That combination of fiberglas over
 24AWG was crafted in our shops about 30 years
 ago as an alternative to cartridge fuses in the
 leads between an b-lead shunt and a panel-ammeter.
 I have no doubt that you will successfully 'fuse'
 2" lengths of 24AWG . . . 100+ amps of battery
 current pretty well predicts the outcome.
 When I'm considering a 'bus extension' in
 crafting an architecture, the decision considers
 mechanical robustness and ease of reliable assembly.
 For example, extending the bus out to a 5A crowbar
 breaker might call for 20AWG fusible link driving
 a 16AWG extension.
 These are system segments NOT part of the
 post crash fire safety considerations that call
 for relatively small, FAST protection on always
 hot circuits. 7A fuses work good in crash post
 crash fire concerns.
 Hence my design decision would lean toward easily
 acquired, manufactured link material that behaves
 well in PIDG crimps . . . there is no practical
 motivation to consider 'amperage' values for
 the links.
 But having offered that, I'm interested in results
 of your experiments. You can roughly control
 the magnitude of fault current by how much 20AWG
 wire is in series with your link. I'd shoot for
 something on the order of 100A. 20AWG is 10mOHMs/foot.
 Your battery will present a series impedance on the order
 of 10 mOhm. So 5 feet of wire in the remainders of
 the test loop would be about right.
 Bob . . .
                  ////
                 (o o)
  ===========o00o=(_)=o00o=========
  < Go ahead, make my day . . .  >
  < show me where I'm wrong.     >
  =================================
Â
  In the interest of creative evolution
  of the-best-we-know-how-to-do based
  on physics and good practice.
|
| | - The Matronics AeroElectric-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
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nuckolls.bob(at)aeroelect
Guest
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| Posted: Wed Dec 27, 2023 10:05 am Post subject: Fusible links |
|
|
At 12:05 PM 12/23/2023, you wrote:
| Quote: | ...appreciate your discussion and input! Â
This discussion is the result of the addition of two E-mags to the current RV project and reviewing the Emag installation instruction. They call for a circuit breaker in series with the power feeder for the E-mag(s). I am using Z-13/8 as a reference guide for this build. I am considering a fusible link instead of a circuit breaker as I am running out of panel space. Thus my concern for both reliability and safety. |
Aha! That's a whole different problem. If I'm reading
ElectroAir literature correctly, that input of bus
voltage to the EMag is a CONTROL signal for the
purpose of disabling the mag during engine run-up
and/or engine shut down. Input current to that
port is TINY . . . about 0.04 Amps. That feeder
is an excellent candidate "source impedance
fault limiting".
Limiting a fault current to feeder friendly
levels: just splice a 22 ohm, 1-watt resistor
into the same spot you might use a fusible-link.
Cover with heat shrink.
A short on that feeder would be limited to
600 mA or less. Voltage drop would be 0.9 volts
or less . . . no effect on functionality.
It's been a common technique in my toolbox
in a constellation of designs for decades.
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.
| | - The Matronics AeroElectric-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
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rv8iator
Joined: 11 Apr 2006
Posts: 145
Location: Newberg, OR
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| Posted: Wed Dec 27, 2023 10:42 am Post subject: Fusible links |
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|
Bob, et al...
 Aha! That's a whole different problem. If I'm reading ElectroAir literature correctly, that input of bus (SNIP) A short on that feeder would be limited to 600 mA or less. Voltage drop would be 0.9 volts or less . . . no effect on functionality. It's been a common technique in my toolbox in a constellation of designs for decades.
I too have been going through the Emagair document.  I have very limited panel space left for ignition management as the ACS key switch is already installed, Per Emagair, there is a 5A CB for each EI.Â
 I am contemplating powering from the main bus (through a 22 ohm resistor). For simplicity, a common feeder for both EI's then to a SPDT switch (Disable power to both EI's) then two NC push button switches for independent preflight check. No 5A CB's.
As I had assigned one fuse slot to the original plan of one EI/one mag, I will use it with a 10A fuse. Running the EI's from the main buss assures they are disabled with the Master Switch.
What am I missing?Â
I did some fusible link testing that I will publish soon, that was to be the circuit protection for the EI's. I like the 22 ohm solution better.
...chris
On Wed, Dec 27, 2023 at 10:07 AM Robert L. Nuckolls, III <nuckolls.bob(at)aeroelectric.com (nuckolls.bob(at)aeroelectric.com)> wrote:
| Quote: | At 12:05 PM 12/23/2023, you wrote:
| Quote: | ...appreciate your discussion and input! Â
This discussion is the result of the addition of two E-mags to the current RV project and reviewing the Emag installation instruction. They call for a circuit breaker in series with the power feeder for the E-mag(s). I am using Z-13/8 as a reference guide for this build. I am considering a fusible link instead of a circuit breaker as I am running out of panel space. Thus my concern for both reliability and safety. |
 Aha! That's a whole different problem. If I'm reading
 ElectroAir literature correctly, that input of bus
 voltage to the EMag is a CONTROL signal for the
 purpose of disabling the mag during engine run-up
 and/or engine shut down. Input current to that
 port is TINY . . . about 0.04 Amps. That feeder
 is an excellent candidate "source impedance
 fault limiting".
 Limiting a fault current to feeder friendly
 levels: just splice a 22 ohm, 1-watt resistor
 into the same spot you might use a fusible-link.
 Cover with heat shrink.
 A short on that feeder would be limited to
 600 mA or less. Voltage drop would be 0.9 volts
 or less . . . no effect on functionality.
 It's been a common technique in my toolbox
 in a constellation of designs for decades.
 Bob . . .
                  ////
                 (o o)
  ===========o00o=(_)=o00o=========
  < Go ahead, make my day . . .  >
  < show me where I'm wrong.     >
  =================================
Â
  In the interest of creative evolution
  of the-best-we-know-how-to-do based
  on physics and good practice.
|
| | - The Matronics AeroElectric-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
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Experiments could be done with fusible links of the desired length