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-   -   Firewall pass-thru (http://www.vansairforce.com/community/showthread.php?t=179490)

Sam_B 02-12-2020 04:54 PM

Firewall pass-thru
 
For getting cables and wire through the firewall, I like the idea of the doubletree ball pass throughs, but they’re a bit spendy. Seeing as how I own a lathe, and a milling machine, I was thinking of making something similar, since I have the stock around, and just have to take the time to cut it. I was thinking of making a tapered collet, a tapered hole for said collet to nest into, and a cap to squeeze the collet into the hole and tighten it to whatever wire/cable/plumbing needs to pass through the firewall. Slather it in the 3M fireproof adhesive before it all goes together to fill in the cracks. So my idea may be well intentioned, but not work in the real world, so I was looking for opinions here.

rocketbob 02-12-2020 05:56 PM

I turned a stainless flange on my lathe, riveted that on the left side of the firewall and passed all three cables thru one hole. Fill the flange with firebarrier. Simple and cheap.

Larry DeCamp 02-12-2020 07:23 PM

Yes machine or fab a bushing.
 
+1 for Rocket Bob suggestion. Dan H helped me years ago and the little T bushings riveted and sealed with firebarrier are flawless.

Carl Froehlich 02-12-2020 08:58 PM

Get the nice SS passthrough flange that comes in the RV-14 kit. Put a piece of fire sleeve inside the flange and a piece over the top of the flange on the firewall side. Wire runs in the middle of course.

Carl

fl-mike 02-12-2020 09:20 PM

I’m using these with the Rocketbob fill.
https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

They are welded stainless.

Sam_B 02-12-2020 09:40 PM

Little T bushings?
 
Quote:

Originally Posted by Larry DeCamp (Post 1407480)
+1 for Rocket Bob suggestion. Dan H helped me years ago and the little T bushings riveted and sealed with firebarrier are flawless.

By ‘little T bushings’ do you mean the ones that come with the Vans kit?

Northernliving 02-13-2020 05:49 AM

Quote:

Originally Posted by fl-mike (Post 1407502)
I’m using these with the Rocketbob fill.
https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

They are welded stainless.

Is this the firebarrier you are using for fill?
https://www.aircraftspruce.com/catal...l2000caulk.php

Tailwind/RVGuy 02-13-2020 06:13 AM

One thing to consider before you fill up your pass thru with fire barrier is whether or not you "might" be adding another wire or cable thru that hole in the future. If so, it will be significantly more work to pass it thru if you have it filled with fire barrier caulk. I used short pieces of 4130 steel tubing welded to a flange (similar to what fl-mike posted) I used a short piece of fire sleeve held in place with safety wire around the tubing and then another safety wire at the end of the sleeve wrapped tightly (no gaps) around the cables/wires/ I then used "rescue tape" around the wire and sleeve to prevent any gases to flow thru. In the event of a fire, the rescue tape would be worthless but the fire sleeve and safety wire should work pretty well until that particular area is not my main concern anymore.

I did use fire barrier around my heavy (#2) starter cable pass thru but knew that I would not be adding any more wires there. It is messy stuff.

Keith

Brdog42 02-13-2020 07:40 AM

Quote:

Originally Posted by fl-mike (Post 1407502)
I’m using these with the Rocketbob fill.
https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

They are welded stainless.

Those who used this method for electrical wiring...

Did you use the same method for control cables? Throttle, mixture, etc.

Thanks for sharing something simple that works!

DanH 02-13-2020 07:53 AM

Quote:

Originally Posted by Northernliving (Post 1407535)
Is this the firebarrier you are using for fill?
https://www.aircraftspruce.com/catal...l2000caulk.php

Yes Brian, that's the stuff.

Sam, I'm guessing you can weld. If so, tubular pass-throughs are easy to make in any diameter, as they are just a tube welded into a base plate.

I've run burn tests on them. When pumped full of Firebarrier 2000, they're as fireproof as anything you can do. Here's one at 2000F, still sealed tight:



The only one I've seen from Vans was on an RV-14. FWIW, I like the tube a little longer, but that's a nit. I snapped a photo of the RV-14 install because it illustrated a caution. Note the exit angle on the heavy gauge electrical wire as it leaves the fitting, rubbing against the edge of the tube. Don't want it to be like that in service. Also, I'm not real wild about Bowden cables and electrical wires in the same fitting. Bowden cables generally connect to the engine, which moves on the mounts. Hang around this game long enough and you'll see an example of a Bowden cable acting like a saw.



Quote:

Originally Posted by Brdog42 (Post 1407573)
Did you use the same method for control cables? Throttle, mixture, etc.

Works for everything Tim. Note that Keith's note regarding the difficulty of removing the silicone plug is valid. To remove the plug, just make a half-moon cutter from a length of tubing one size smaller than the pass-through tube, and force it through to cut the sealant perimeter. The firesleeve approach is also accepted in some certified applications, although perhaps not as fire-tough as the solid plug.



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