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lrsecaldwell(at)earthlink
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 Posted: Sun Oct 05, 2008 5:17 am Post subject: Split loom melting |
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I have experanced melting of some of the black split loom I used an
conduit to prevent wire chaffing in my engine compartment. One piese
that melted was 6 or 7 inches from the exhaust tube.
Note that this is a recent problem that has occured after I add some
additional heat shield due to heat discoloration on the inside of the
lower cowl,
Has anyone else had this problem?
Does anyone have any data on what temperatue exists in the engine
compartment?
As an aside I did some informal tests of the black split loom and it
burns and is not self extinguishing.
Are thre any good fire resistant alternatives?
Roger
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nuckolls.bob(at)cox.net
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| Posted: Sun Oct 05, 2008 6:53 am Post subject: Split loom melting |
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At 09:07 AM 10/5/2008 -0400, you wrote:
| Quote: |
Caldwell" <lrsecaldwell(at)earthlink.net>
I have experanced melting of some of the black split loom I used an
conduit to prevent wire chaffing in my engine compartment. One piese
that melted was 6 or 7 inches from the exhaust tube.
Note that this is a recent problem that has occured after I add some
additional heat shield due to heat discoloration on the inside of the
lower cowl,
Has anyone else had this problem?
Does anyone have any data on what temperatue exists in the engine compartment?
|
Temperatures under the cowl can range from ambient
(OAT at xx-thousands of feet in the winter) to
hundreds of degrees (radiant heating from exhaust
components). In the "big airplane factories" we've
had suppliers of spiral wrap, split loom and zippered
sleeve wire bundling products come and go. The
added cost, labor, maintenance and addition to weight
have never passed muster with the guys who tracked
cost-of-ownership for airplanes.
You can bet that should this technology be considered
worthy of flight in a TC aircraft, it would be made
from materials similar to the wire it protects . . . i.e.
Tefzel or one of the more exotic synthetics. Given
that Tefzel tie wraps are around $1.50 each in low
quantities, you can bet that the cost of Tefzel spiral
wrap is similarly breathtaking.
| Quote: | As an aside I did some informal tests of the black split loom and it burns
and is not self extinguishing.
Are thre any good fire resistant alternatives?
|
Not aware of any. The popular nylons are probably
incapable of tolerating the localized heating situation
you've identified. You might consider re-routing the
bundle, running it through fire-sleeve, or some other
process that puts a barrier between your wire bundle
and the IR heat source that's pushing it over the
cliff. I'd vote for re-routing the wire bundle.
Bob . . .
----------------------------------------)
( . . . a long habit of not thinking )
( a thing wrong, gives it a superficial )
( appearance of being right . . . )
( )
( -Thomas Paine 1776- )
----------------------------------------
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Allen Fulmer
Joined: 10 Jan 2006
Posts: 79
Location: Alexander City, AL
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| Posted: Sun Oct 05, 2008 12:18 pm Post subject: Split loom melting |
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Bob,
Am I drawing the correct conclusion from your comments that using split loom
or most any "conduit" is NOT a preferred method of "protecting" a wire
bundle in the engine compartment?
I must admit that in my planning and building I have "assumed" conduit was
desirable from an appearance standpoint while not considering the
temperature the wires would be exposed to.
Allen Fulmer
RV7 Eggenfellner Subaru E6Ti
[quote]>>--
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_________________
RV7 QB Fuselage
Eggenfellner H6 on orde
N808AF reserved
Alexander City, AL |
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nuckolls.bob(at)cox.net
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| Posted: Sun Oct 05, 2008 2:56 pm Post subject: Split loom melting |
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At 03:16 PM 10/5/2008 -0500, you wrote:
| Quote: |
Bob,
Am I drawing the correct conclusion from your comments that using split loom
or most any "conduit" is NOT a preferred method of "protecting" a wire
bundle in the engine compartment?
|
Don't know how to define "preferred". If you look under
the cowl of a TC aircraft,
http://aeroelectric.com/Pictures/Wiring_Technique/A36_Firewall_B.jpg
http://aeroelectric.com/Pictures/Wiring_Technique/A36_Firewall_A.jpg
You can see that the designers use the UV/ozone resistant Tie-Straps
and MS21919 clamps. No other protection is considered necessary.
| Quote: | I must admit that in my planning and building I have "assumed" conduit was
desirable from an appearance standpoint while not considering the
temperature the wires would be exposed to.
|
Tefzel wire is good to 150C . . . I'd take the low
temperature plastic stuff clear out of the engine
compartment. Then keep and eye on the bundle adjacent
to the observed damage . . . just to be sure you're
not bumping the Tefzel limits.
Bob . . .
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Speedy11(at)aol.com
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| Posted: Mon Oct 06, 2008 12:02 pm Post subject: Split loom melting |
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Roger,
I'm using Thermo-Tec Thermo Sleeve tape to protect wiring exposed to heat. It withstands 2000F so it should do well in all situations up to and including a fire.
Here is a link to one source - although if you search the net a bit you can find better prices.
http://www.autobarn.net/thhowiprta.html
On my hoses I used the thermo sleeve and on things that are difficult/impossible to pull a sleeve on, I used the tape. It presents a much nicer appearance on the engine than standard red fire sleeve.
You could even use the sleeve and split it along the seam, cover the wires, and then tape it with the thermo tape to hold it in place. I've also used safety wire on the ends to hold it.
Another good option is sleeving that is designed for wires and can be slit to fit on the wires. It's good to 750F and comes in several colors. You can see it at https://www.shopatron.com/product/part_number=17078/681.0
Regards,
Stan Sutterfield
| Quote: | I have experanced melting of some of the black split loom I used an
conduit to prevent wire chaffing in my engine compartment. One piese
that melted was 6 or 7 inches from the exhaust tube.
Note that this is a recent problem that has occured after I add some
additional heat shield due to heat discoloration on the inside of the
lower cowl,
Has anyone else had this problem?
Does anyone have any data on what temperatue exists in the engine
compartment?
As an aside I did some informal tests of the black split loom and it
burns and is not self extinguishing.
Are thre any good fire resistant alternatives? |
New MapQuest Local shows what's happening at your destination. Dining, Movies, Events, News & more. Try it out! [quote][b]
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klehman(at)albedo.net
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| Posted: Mon Oct 06, 2008 6:44 pm Post subject: Split loom melting |
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It is more likely radiant energy than actual air temperature that is the
problem. Perhaps your new heat shield is reflecting some heat back
toward your wiring?? Some low dollar solutions that I've used include:
For mild exposure, wrapping the exposed section of wire etc. with
silicone tape will reflect some heat and that nicely protects a rubber
engine mount for me. Silicone is good for up to at least 500F surface
temp. This is essentially what the outer layer of fire sleeve is
composed of I believe.
Wrapping with aluminum foil reflects even more heat.
A metal heat shield between the exhaust and the wires or hoses that are
exposed is probably preferred if you can't relocate the wires. I have
not had any problem with 0.020 aluminum shields even when quite close to
exhaust pipes.
Ken
| Quote: |
I have experanced melting of some of the black split loom I used an
conduit to prevent wire chaffing in my engine compartment. One piese
that melted was 6 or 7 inches from the exhaust tube.
Note that this is a recent problem that has occured after I add some
additional heat shield due to heat discoloration on the inside of the
lower cowl,
Has anyone else had this problem?
Does anyone have any data on what temperatue exists in the engine
compartment?
As an aside I did some informal tests of the black split loom and it
burns and is not self extinguishing.
Are thre any good fire resistant alternatives?
|
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http://www.matronics.com/Navigator?AeroElectric-List |
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