olnico

I have just finished a blog on how to protect your electrical system for the heat generated by the engine and a possible catastrophic exhaust pipe failure.

http://www.ultimate-jets.net/blogs/j...haust-and-heat

Turbotronic

Nice, I like the kevlar shield hose idea. I agree a hot gas leak plume may be quite destructive.
The silicon wire puzzles me since all types of silicon I have used have a very poor resistance to kerosene, sort of goes snotty and swells up getting very soft?
Have never tried the servo silicon, no experience there.
Just built an e32 plane with silicon wires on the ESC and it exposed wire just about right away after getting nicked on a sharp edge. This was on an e-flight ESC.
Ptfe wire seems like a good idea but rather inflexible if I remember correctly.
Some readily available high temp servo wire with kero resistance could be a good seller....
BRG
Andre

olnico

Andre, our silicon servo wire have a resistance time to kerosene of 20 minutes. After that, they start swelling up as you said. In practice they hold quite well in the plane as long as you wipe off an internal fuel leak. In any case that should always be done to avoid damaging internal components and risks of fire.
The PTFE cables are virtually un-sensitive to kerosene and quite flexible in 22 AWG, as well as much lighter than silicon HD cables. So, perfect choice for people looking for total resistance to kerosene. However they are twice the price of the silicon servo cables.

DrScoles

My Feedback: (18)

Thanks for the informative article. What is the safe temperature for a wiring loom to get to with regular servo wire? Is shielding it with heat blanket and foil adequate if you aren't worried about direct flame?

olnico

Well, there is no such thing as regular servo wire. It all depends of the wire gauge and type of insulation. You need to make a test with the servo wire you intend to use. Shielding with separate material can be adequate, but bare in mind that shielding is always as good as the weakest spot. If one zone is not properly covered, then shielding is useless. That's why I recommend using heat sleeves. The time you'll save wrapping around the cable and having a 100% heat and chemical proof shielding will largely make the price increase.
Have a look at this video:
[link=http://vimeo.com/69404938]Wrap around MIL spec sleeve demonstration.[/link]

Turbotronic

Thanx,
The Ptfe wire is interesting. Do you plan on maybe selling "starter kits" for doing the average jet? Another reason for high temp wire could also be to prevent fatal shorts in cabling where an overcurrent condition would soften/melt PVC. Seen this happen a few times.
Andre

Ozmodeller

Thanks for the informative article.

On my FB T33 I acquired some nomex sheathing that is used in full size aviation wiring looms and have used that for the servo leads from the rear, the concern I have is the visible portion of the servo leads where they connect to the extensions, what do you think would be the best way to protect that area or would it not be an issue, I had thought of using some aluminium (aluminum to you guys) adhesive tape burnished over the area, thoughts?

Regards
Peter

olnico

Thanks for the kind words oz.
It all depends if the servo connection is susceptible to get exposed to some kind of heat, and to what extend.
If this is the case, the wrap-around sleeve is pervfect since you can still access the servo plug easily...