Punching Through the Firewall

[macrafic]

I'm building an IO 7A and the plans call for a few holes to be punched through the firewall (nose gear access, throttle, cabin heat inlet, mixture, brake reservoir, fuel pump, etc.).

Some of these are located close together, like the throttle and cabin heat inlet. Can they be combined into one larger hole (one firesleeve or eybolt)?

What has everybody else done when they have a single smaller firewall penetration (firesleeve, eybolt, or something else)?

 

[lrfrey]

In general, multiple wires may pass through the same hole in the firewall, but cables should always be given their own hole and supported firmly. As far as the method, there are multiple good ways of doing it, each must make that assessment themselves. Several builder sites have excellent phots.

Larry

 

[vbpiper]

Firewall holes

Just a thought. I would not be in too big of a hurry to punch the holes. I did it early and now I'm sorry because I would have liked to use the eyeballs for the cable pass-thrus but the holes are too close together in some areas. If you want to use the single-hole eyeballs (available thru Van's and other sources) it might be worth buying them before punching the holes to make sure the spacing is adequate.
Good luck.
Ward

 

[Rick6a]

I'm building an IO 7A and the plans call for a few holes to be punched through the firewall (nose gear access, throttle, cabin heat inlet, mixture, brake reservoir, fuel pump, etc.).

Some of these are located close together, like the throttle and cabin heat inlet. Can they be combined into one larger hole (one firesleeve or eybolt)?

What has everybody else done when they have a single smaller firewall penetration (firesleeve, eybolt, or something else)?

If you have not yet decided on an IO engine...WAIT! There are just too many variables to consider and routing will dictate cable length. If however, you are ordering an OEM engine and FWF kit from Van's go ahead and make most of the firewall penetrations. My firewall was shipped with many of the penetrations already made and are referenced in the FWF drawings. I took advantage of the easier access and recently routed the throttle, mixture, and prop cables even though the engine will not be delivered for months. The eyeball type pass-throughs were kind of pricey at $30 per but there are less expensive alternatives out there. I did have to slightly adjust the spacing a bit to accomodate the eyeballs but was no big deal. Control cables should be separate but electrical cables can be grouped, for instance when bundling EGT or CHT wires together for one convenient pass through. Here's a link describing how to make homemade firewall grommets...the ultimate way to make pass-throughs on the cheap. http://www.ch601.org/tools/firewall/firewall_grommets.htm