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09-25-2017, 09:32 AM
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Join Date: Jan 2005
Location: 57AZ - NW Tucson area
Posts: 10,011
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Quote:
Originally Posted by AlexPeterson
Should be ok - have a look at the specific data sheets for that fuse, it will show the time to open vs current.
I used this brand - it shows as a minimum opening time at full rated of about 4 hours..., max opening time at rated of infinity. They are designed to be matched to the alternators. 120s opening time minimum, 30 minutes maximum, at 135% of rated.
http://www.littelfuse.com/~/media/au..._datasheet.pdf
That brand is about $7 plus a couple dollars shipping from Digikey.
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This is interesting since I was getting ready to start a thread "Is the ANL Fuse Obsolete?"
This is talking about the type of fuse/limiter, not having a fuse.
A decade ago the ANL fuses were everywhere and I remember I got mine from Home Depot. All common sizes in cards hanging on an aisle wall.
Update - apparently Buss has stopped making them and the are now considered obsolete, having been replaced by smaller devices such as the ones linked to above.
I blew one during final assembly of my -6A (my fault, not any equipment) and the only one I could get locally was expensive and 100 Amps only. Ebay still has them but even my local friendly ACE store couldn't special order them.
The usual auto use for these type of devices is for the drivers with high power (ie very loud  ) audio systems. I think we need to find out what is popular with them them and get a new standard for our firewalls.
Meantime, if you have an existing ANL fuse buy a few spares now on Ebay.
__________________
Gil Alexander
EAA Technical Counselor, Airframe Mechanic
Half completed RV-10 QB purchased
RV-6A N61GX - finally flying
Grumman Tiger N12GA - flying
La Cholla Airpark (57AZ) Tucson AZ
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09-25-2017, 11:48 AM
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Join Date: May 2007
Location: salem Oregon
Posts: 1,023
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Quote:
Originally Posted by vic syracuse
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Hello VIC, whoa that's a great response guys. Gee been flying for a year without a fuse in-o to the main buss from the Master relay. Vic I did order that holder and 60 amp ANL fuse , thanks BIC! They didn't have a 50 amp so I went with a 60 amp. I want to thank all you builders for your input, been very helpful.
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09-25-2017, 12:03 PM
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Join Date: Sep 2005
Location: Maple Grove, MN
Posts: 2,333
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For perspective, the $7 Digikey one I linked to in my earlier post in-situ:
And, since Google is crabby, here's the photo link:
__________________
Alex Peterson
RV6A N66AP 1700+ hours
KADC, Wadena, MN
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09-25-2017, 12:25 PM
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Join Date: May 2006
Location: Pocahontas MS
Posts: 3,884
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Not to pick on Alex's photo, but if you use a device like this, be sure it's mounted where vibration and/or stress won't kill it. Most of them are intended to be mounted in a stable holder of some sort; the fuse link isn't structural for itself. (The one in Alex's pic might well be intended for unsupported use; I don't know.)
Another option, especially for alternator B-leads and medium-current feeds into the cockpit, is a fabricated fusible link. Any wire can be protected by a short length of wire 4 gauge numbers smaller, ~4-6 inches long. EX: an 8 gauge wire can be protected with a 12 gauge fusible link. The upside is that the link can be soldered in. There are fewer joints to potentially fail, and it will never 'blow' unless there's a truly catastrophic fault (the only reason this sort of protection is included).
Nuckolls used to recommend them, until the high current, small, bolt-in links became common. Car makers have used them for decades in the engine compartment.
With electrically dependent engines getting more common, they are worth a look.
You can buy made-for-the-job fuselink wire in the larger sizes, or you can roll your own using tefzel wire and either woven fiberglass sheathing as a flash container, or for small gauge stuff, I've been using silicone tubing. (Destructive tested 22 gauge as a fusible link for 18 gauge.)
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09-25-2017, 12:33 PM
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Join Date: Sep 2005
Location: Maple Grove, MN
Posts: 2,333
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Quote:
Originally Posted by rv7charlie
Not to pick on Alex's photo, but if you use a device like this, be sure it's mounted where vibration and/or stress won't kill it. Most of them are intended to be mounted in a stable holder of some sort; the fuse link isn't structural for itself. (The one in Alex's pic might well be intended for unsupported use; I don't know.)
Another option, especially for alternator B-leads and medium-current feeds into the cockpit, is a fabricated fusible link. Any wire can be protected by a short length of wire 4 gauge numbers smaller, ~4-6 inches long. EX: an 8 gauge wire can be protected with a 12 gauge fusible link. The upside is that the link can be soldered in. There are fewer joints to potentially fail, and it will never 'blow' unless there's a truly catastrophic fault (the only reason this sort of protection is included).
Nuckolls used to recommend them, until the high current, small, bolt-in links became common. Car makers have used them for decades in the engine compartment.
With electrically dependent engines getting more common, they are worth a look.
You can buy made-for-the-job fuselink wire in the larger sizes, or you can roll your own using tefzel wire and either woven fiberglass sheathing as a flash container, or for small gauge stuff, I've been using silicone tubing. (Destructive tested 22 gauge as a fusible link for 18 gauge.)
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Good point regarding support. Mine is very well supported top and bottom (the top is mounted to a copper bar, which is in turn mounted to a block with the current sensing shunt). I would not mount one without support on both ends.
__________________
Alex Peterson
RV6A N66AP 1700+ hours
KADC, Wadena, MN
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09-25-2017, 01:54 PM
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Join Date: Feb 2010
Location: Gardnerville Nv.
Posts: 2,828
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Being a auto, med, heavy truck tech, it can be frustrating trying to find and identify a burnt fusible link in a harness, some will burn the insulation, and some won't, one or two in a plane you built and know where they are is a different story. They were installed in vehicles a long time ago to deal with current start up induced load, (the start up current would blow a fuse rated for the running current) old heavy HVAC fan motors ECT. 
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7A Slider, EFII Angle 360, CS, SJ.
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09-25-2017, 03:38 PM
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Join Date: Aug 2010
Location: Newport News, Va
Posts: 325
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Bob Nuckols on protecting "fat" wires
Quote:
Originally Posted by DanH
I can think of both pros and cons, but tell us why Bob doesn't like it.
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In working on my electrical system design I reference Aeroelectric Connection and Aeroelectric List. I assembled some notes on Bob Nuckols' opinion regarding circuit protection of "fat" wires, from Aeroelectric List, below.
Note there is protection in the cockpit in terms of being able to shut off the master relay and being able to remove alternator field current. And of course every connection is a potential failure.
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Bob quotes the FARs:
Sec. 23.1357 Circuit protective devices.
(a) Protective devices, such as fuses or circuit breakers, must be installed in all electrical circuits other than--
(1) Main circuits of starter motors used during starting only; and
(2) Circuits in which no hazard is presented by their omission.
(b) A protective device for a circuit essential to flight safety may not be used to protect any other circuit.
(c) Each resettable circuit protective device ("trip free" device in which the tripping mechanism cannot be overridden by the operating control) must be designed so that--
(1) A manual operation is required to restore service after tripping; and
(2) If an overload or circuit fault exists, the device will open the circuit regardless of the position of the operating control.
(d) If the ability to reset a circuit breaker or replace a fuse is essential to safety in flight, that circuit breaker or fuse must be so located and identified that it can be readily reset or replaced in flight.
(e) For fuses identified as replaceable in flight--
(1) There must be one spare of each rating or 50 percent spare fuses of each rating, whichever is greater; and
(2) The spare fuse(s) must be readily accessible to any required pilot.
=========================
Some quotes from Bob:
“I'll direct your attention to paragraph (a)(2) which speaks to battery feeders and feeders to main power distribution busses that are typically the largest wires in the airplane and are not subject to being "smoked" by downstream faults. You can comfortably leave out the fuse you've cited.
A 12AWG wire is probably too small to be a bus feeder. When wiring with truly "fat" wires (6AWG or larger) they're not at high risk for burning due to shorts or overloads. Take a look at the wiring diagrams for any single engine TC aircraft and you'll find that few if any will incorporate fuses or current limiters in these pathways. This philosophy is echoed in the FARS…
Faulted robust wires generally arc to ground and burn their faults clear. Further, they're easily installed with attention to mechanical details such that faults to ground are as probable as losing one's propeller due to bolt failure.
The Z-figures are crafted with this philosophy in mind supported by a confidence in nearly 100 years of field history. I'll suggest that none of your fat wires should be smaller than 6AWG and that protection beyond what is illustrated in the Z-figures is no-value-added weight, cost and complexity.”
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Last edited by johnbright : 09-26-2017 at 06:01 AM.
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09-26-2017, 05:54 AM
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Join Date: Feb 2010
Location: Gardnerville Nv.
Posts: 2,828
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All good points and we can wire these flying machines how we like, but one point that Dan brought up and one I agree with is the ANL to the alternator, If....the B+ lead came off in flight at the alternator, you would no know you had a flopping around stick arch wire burning everything it touches, and if it made a good contact, where would the reverse current load go? would it burn out the stud and disc in the master relay? or worse, This is not a short piece of copper bar bolted down hard, this wire goes a long way from the firewall through the engine mount to a vibrating fan twister, some of these alternator wires are 8-6 ga and will carry a lot of current to cause damage if not protected. I have one, to each their own. 
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7A Slider, EFII Angle 360, CS, SJ.
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09-26-2017, 07:04 AM
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Join Date: May 2006
Location: Pocahontas MS
Posts: 3,884
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Just to be clear, Nuckolls' writings/drawings include a protection device at the battery end of the alternator B-lead.
The 'fat wires' mentioned are the very heavy gauge lines from the battery to the main contactor, and to the starter.
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