Firewall Eyeballs

Noah · #1 04-19-2009, 11:48 AM

Getting ready to order firewall eyeballs for control cables. There are 3 varieties offered by Vans / Spruce:
http://www.aircraftspruce.com/catalo...pplication.pdf

My preference is to use steel as it's lighter than the aluminum version (!) and probably going to survive fire better than aluminum at the firewall. However, in looking at these photos, I don't think it will work. Vans control cables measure about .345" dia, and the penetrations measure either .260 or .375. If you look at the photo of the steel version, it has a thinwall ID which would probably be completely removed if drilled up from .260 to .345 in. Thus it seems that only the aluminum versions will work with Vans cables. Can anybody confirm this? Is there any advantage / disadvantage to the single hole version vs. the multi-hole version?

Also, in looking at old posts on this subject, EPM-Avcorp is mentioned as having alternatives to the eyeballs. However, the web addresses for this company are no longer valid. Is there a current URL for these products?

chaskuss · #2 04-19-2009, 12:30 PM

Noah,
Two thoughts come to mind. If you drill out the steel eye balls, you could seal the hollow area in them with an intumescent sealer, like those sold by Vans or 3M. See

http://www.vansaircraft.com/cgi-bin/...product=cs1900

Second, use the aluminum eye balls and cover the forward side with a stainless steel shield or intumescent sealant. I'm sure other listers will offer other ideas.

Charlie Kuss

szicree · #3 04-19-2009, 01:40 PM

The single hole type suck. There is no practical way to tighten the big aluminum nut in the narrow confines of the firewall. I speak from first hand experience on this one.

Greg Arehart · #4 04-19-2009, 02:17 PM

Noah,

I used the aluminum ones that can be drilled for my wiring pass-throughs. For the control cables I used the cable-safe, also available at ACS. I cut some wedges to place under the cable-safe (like wedged washers) to get the appropriate angle. this necessitated only a single hole. If I were to do it over, I would probably just use the eyeball for my cables as well.

greg

Noah · #5 04-21-2009, 05:01 PM

Quote:

Originally Posted by chaskuss

Noah,
Two thoughts come to mind. If you drill out the steel eye balls, you could seal the hollow area in them with an intumescent sealer, like those sold by Vans or 3M. See

http://www.vansaircraft.com/cgi-bin/...product=cs1900

Second, use the aluminum eye balls and cover the forward side with a stainless steel shield or intumescent sealant. I'm sure other listers will offer other ideas.

Charlie Kuss

Good ideas Charlie. I think I'll order up one of the steel eyeballs and see how sharp it would be and how much area would remain in contact with the cable after drilling. If it doesn't look too bad I'll get 2 more of them and use the intumescent sealer.

Thanks for the comments guys.

Noah · #6 04-21-2009, 05:22 PM

Hmmm, one other thought. What's the downside to buying the .375" ID eyeball and filling the .015" radial gap with the intumescent sealer? The cables are anchored at both ends and I wouldn't think that they would need to be really anchored at the firewall. You don't want it sliding in and out of there so much that abrasion could be a concern, but I wouldn't think that you need it to be totally clamped either.

Anybody used the .375 ID eyeballs?

chaskuss · #7 04-22-2009, 11:15 AM

Quote:

Originally Posted by Noah

Hmmm, one other thought. What's the downside to buying the .375" ID eyeball and filling the .015" radial gap with the intumescent sealer? The cables are anchored at both ends and I wouldn't think that they would need to be really anchored at the firewall. You don't want it sliding in and out of there so much that abrasion could be a concern, but I wouldn't think that you need it to be totally clamped either.

Anybody used the .375 ID eyeballs?

Noah,
The sealant would fill the gap. However, I would be concerned that over time, movement of the cable would extrude the sealant out of the gap. I have no idea if that would actually happen. ???
If you use the .375" steel eye balls, you could use steel shim stock wrapped around the cable to take up the excess space. 3 wraps of .005" shim stock should work. Shim stock of other thickness should also work. MSC and McMaster-Carr both sell shim stock. If you have a friend who is a machinist, you can probably steal some from him!

I figure that .005" shim stock will conform to the shape of the cable easier than .015" stock.
Charlie Kuss

ronschreck · #8 04-23-2009, 04:10 AM

Quote:

Originally Posted by szicree

The single hole type suck. There is no practical way to tighten the big aluminum nut in the narrow confines of the firewall. I speak from first hand experience on this one.

You are too kind! I have replaced all of these lousy blue single hole types as they are nearly impossible to remove and re-install if you ever (and you will) have to replace a cable. A very poor design.
I replaced all of mine with the multi-hole type with the aluminum insert. Looks great and cables can be replaced without having to access the back side of the firewall.