Primarily for general aviation discussion, but other aviation topics are also welcome.
By patowalker
#1519105
AIUI, Kapton has been found to degrade and crumble.that strikes me as potentially more risky than PVC or silicone.The other issue that strikes me, is how thin the wiring is! Yes, I know weight is an issue, but ,unless the currents are very small, heating will be an issue.
Perhaps a professional can enlighten us?


I am no expert, but have used Tefzel coated wire in three aircraft builds.

Wire - Aviation Grade Tefzel Insulated Cable
This is a guide to the maximum recommended current for AWG cable when used for airframe/chasis wiring.
AWG 4 - 135 Amps AWG 6 - 101 Amps AWG 10 - 55 Amps AWG 12 - 41 Amps AWG 14 - 32 Amps
AWG 16 - 22 Amps AWG 18 - 16 Amps AWG 20 - 11 Amps AWG 22 - 7 Amps AWG 24 - 3.5 Amps
Manufactured to MIL 22759. Rated to 600 volts and max temperature of 150 degrees C.


http://www.triodedick.com/pdf_files_td/AWG_toMetric_Conversion_Chart.pdf
By tomshep
#1519112
Well, sort of. The resistance increases with length and using I x R, you will get a figure that is voltage drop in the cable. The thinner the cable, the greater the drop as the cross sectional area of the wire controls the coefficient of resistivity.
If you were dropping a Volt in a cable carrying 10 Amperes, the resistance would be 1/10 Ohm. You would be dissipating ten Watts of energy as heat. Better to use a thicker cable and use the engine power to lift the weight rather than cook the wiring!
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By kanga
#1519210
I recall there used to be at RAF Sealand a workshop dedicated to producing wiring looms, both routinely and for repair/replacement after damage. This included bespoke looms for effectively orphan types in UK military service, eg (then) Pembroke. Their service was much quicker and cheaper even for types then currently in production than ordering from manufacturer. Their total running costs were outweighed by the savings. Their raison d'etre was training by civ & mil instructors of mil technicians for repairs in the field, including for battle damage. For that reason their wire-end markings and colour-codings were exemplary, much better than some current OEMs'. Oh, and they were also foreign exchange earners, as USMC found that they provided a better, cheaper service for AV8B looms than McDD's own subcontractors did.

So, of course, they were shut down and the service was outsourced, in the name of efficiency. :roll:
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By AdamFrisch
#1519662
For someone of my "slightly touched" intelligence, I learned something new the other day. I always wondered how they traced an avionics cable from, say, the panel all the way back under the floor, through the pressure bulkhead etc without isolating is and manually tracing it all the way. Turns out each cable has an individual serial number on it. Isn't that clever? :D
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By PeteSpencer
#1519693
AdamFrisch wrote:For someone of my "slightly touched" intelligence, I learned something new the other day. I always wondered how they traced an avionics cable from, say, the panel all the way back under the floor, through the pressure bulkhead etc without isolating is and manually tracing it all the way. Turns out each cable has an individual serial number on it. Isn't that clever? :D


The pre production prototype of Concorde on display at Duxford has 200 miles of such cable in looms ,each strand neatly printed every coupla feet with unique number...
By cockney steve
#1519698
British automotive system, also German....basic colour with lengthwise "tracer" stripes......unfortunately, each manufacturer had their own "code"....so, solid black may be "earth" on one make...Ignition-switched live on another.

then you have the French!....plain colour with a contrasting dob of colour each end ...great when new, a bu66er when discoloured by oil, or rubbed off altogether....then there's the Pink that goes in one end of the loom......vanishes.....but, wait, there's a white and a sky-blue that appear to connect!......they do, indeed, soldered joint, bound up and hidden at an odd random point within the loom.........without a comprehensive wiring -diagram, this costs the customer a lot of money, tracing these "funnies"

I have come across the coded cores as described by Pete Spencer Very expensive in small quantities, I suspect, which is why most small /custom jobs of any quality have numbered/ coloured sleeves on the ends....a common system has sleeves numbered 1-9 +0.....slip on the desired combination and crimp to lock in place........the fun starts down the line, if a fault occurs anywhere along the length, or it needs to be tapped -into.

Knew a bloke who made fruit-machine harnesses. the cables came pre-cut,but generously over-length...he decided to shorten them and tidy things up before crimping on the terminals....scrap offcuts paid for his annual holiday. happy man!