Sunday October 13, 2024
Firewall Passthroughs (Firewall Forward)
2.0 Hours

So last weekend I had been trying to decide how to do my firewall penetrations for wires and control cables. I wanted to do something made of steel with some resistance to fire. One of the nicer ways of doing this is to install a short section of steel tube welded to a steel plate and fasten that to the firewall. You can buy some really expensive versions of this from Spruce.

Instead, I ordered some steel curtain rod end holders off of Amazon and it turns out they're really solid and a lot cheaper. I have some smaller ones that are about 0.5" ID and I'm going to use these for control cables and one wire penetration near the contactors. Then a couple of larger ones (about 0.75" ID) will serve for the rest of the wire penetrations up high.

Here's the first spot I did today...it will carry the main power cable from the battery contactor to the fuses inside the cockpit. It will also likely carry wires from panel switches to the two contactors as well as the main alternator field wire. It was kind of a pain to get into this spot. I used some scrap aluminum sheet to make a drilling template and drilled the mounting holes from inside the cockpit. The pass-through is attached with 3 AN3-3 bolts. It is sealed against the firewall with fire barrier sealant. I will wrap the wires with inner and outer layers of fire sleeve and then clamp it all down.

Closer shot.

Here's the throttle cable pass through lower down on the firewall. Same thing here.

And here with the cable passing through it and some -8 firesleeve. I will add another section of larger firesleeve that passes over the outside of the steel tubing.

I'll have one contiguous piece of fire sleeve all the way from along the throttle cable to its mounting bracket under the sump to try to protect from exhaust heat.

I'm really pleased with how sturdy and inexpensive this system turned out. I'll do three more of these small ones (for mixture, prop, and oil cooler/alt air cables) and then the two bigger ones.

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