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Firewall Passthrough
Where did you put your firewall pass through for wires, sensors wires etc and how big?
I plan on going with the SS kits from Spruce. After a search on line I found a few examples but looking to see where others put them and what size. Thanks in advance E |
Timely Question
You're question is very timely, I was about to ask the same thing. I did buy two of the 1" SS pass threws, I was wondering if you just enlarge the two holes in the image below to be 1" or are these earmarked for something else, I looked through the plans and can't really see that these are for anything else:
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I can't see your image but if that is the roughly thumb-sized holes left and right on the firewall, that is indeed what they are intended for. However, I am using sealed CPCs for my passthrough and the extended sleeve (about 3 inches) would have interfered with the motor mount, so I covered the existing holes with riveted stainless steel covers and relocated my openings. My point is that you can relocate things as needed and appropriate for your installations.
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Thanks, can other's not see my image? I have been having a hard time moving from picassa to goggle photos.
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cant see it either...
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Make sure you share the photo first and then change your link.
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Ok, how about now:
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Yup, I can see both now :)
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Not many people have chimed in. I'm also interested in what people have done. I've been stalling drilling mine, but I'm about finished with the avionics and will be riveting my panel substructure in soon and would rather install the passthrough prior.
I'm thinking I will use the existing LH hole for my battery cable, install a 1" firesleeve passthrough near the center, and use the RH passthrough hole only if I were to run out of room in the 1" hole. :confused: |
Remember that the alternator wire carries a pretty large current and does have some ac ripple on it. In principle good avionics boxes will filter out any pickup, but I chose to use separate firewall holes for the alternator output, and for low level signals (EGT probes, etc). ymmv
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4 on a 7
This is on an RV-7 - but for what its worth I used 4 for electrical. Top "corners" carry EGT/CHT and other engine sensor wires; one near the center top carries Electronic Ignition leads/ mag P-lead; large angled one on the right side carries all power wires.
I also used 3 additional passthroughs like these for the throttle, mixture and prop cables. |
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I'm using the SS fire-sleeve pass throughs from ACS you've mentioned. I ended up with one of each size. The interior firesleeve eats up a lot of space. The #2 battery I bring through the existing hole which I enlarged for a bulkhead fitting. The smallest SS pass-through I've got on the top-left of the firewall and will be using for ignition related wires. The 3/4" pass-through I've got in the little slot designed for the heat boxes and alternate air door. The 1" pass-through I've got on the upper right for all the thermo-couple wires and various other engine monitor wires. Van's has you drill another hole for a bulkhead fitting if you position the manifold pressure sensor on the inside. The existing hole on the far right I probably could have used for the 1" SS pass-through but didn't, thinking I would use it for something else. I'm going to plug that one.
Also, if you happened to drill the holes in the stainless recess according to the plans (as I did), you'll find that most of the nice pass-throughs for prop/mixture/throttle cables won't fit because the holes are too close together. I found these on ACS which do fit. I installed them just the other day. https://www.aircraftspruce.com/catal...algrommets.php |
I like those SPHERICAL FIREWALL FITTINGs, what size did you order for the three control cables?
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Should work now.
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They were showing for me yesterday afternoon, but now they are just dashes again.
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Thx Steve |
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Understand that they are not flame-proof. But they are way better than Circular Plastic Connectors and probably as good as many of the other pass-throughs in common use, where the weak link is burn through of the wire insulation being passed. The idea of such devices (shields and such) is to minimize the exposure and grant a little extra time (seconds?) to deal with a fire incident. So why not just use one of the simpler and much less expensive solutions available? When I had my landing incident in my RV-6A, I had to replace the fire-wall and a couple of the stringers behind it. This meant that I had to undo connections to thermocouples and sensors, etc. and thread them all back through the firewall. The worst were the connectors for the Lightspeed ignitions, 25-pin soldered connectors on the cold side to the crank sensor circuit board (potted connections) on the hot side. It took some large penetrations and creative shielding but I managed it. I also decided that the automotive approach of a connector at pass through was the way to go. In the -10, if I need to remove the engine, I won't have to decouple each individual CHT, EGT, etc. Instead, I will just have to undo the starter cable, grounding strap, and two bundle connectors (not mentioning fuel and oil lines). If (gods forbid) I have an incident similar to the one I had before, replacing the firewall won't involve a lot of wiring work. And I carried the idea through the plane. Replace a rudder? Just wire the rear strobe and trim servo to a CPC in the bottom fairing and attach to the connector already routed from the fuselage. The downside of connectors is connector reliability and maintenance (plus initial expense). But you can select good quality connectors with some research and maintenance is not difficult during inspection. Consider the reliability of the connectors already in use in lighting systems, for example. But, as with everything else in experimental aviation, it is individual choice and preference. |
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FYI: After drilling this and working on this new hole for the P27 battery cable in the firewall I'd recommend doing something different than the wiring plans. If you do drill the hole, cut the end off the cable and crimp a new end. With the crimp size on the cable, it will not fit a 1/2 hole. I had to upsize to 5/8 and now I'm looking for a bushing. Had I give more thought I'd have just cut the end off the cable. My .02.
Lynn Quote:
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If your looking for some of the best and safest, look at:
http://www.doubleteeproducts.com They made the exact sizes I needed for all my pass-through needs. Highly recommended! |
Putting together a BOM for my Firewall and Tunnel.
Fore the firewall the jist is I'm going to use Stainless Steel passthroughs and grommets, with sandwiched Fiberfrax and 0.002" stainless foil. I'll then use 3M Fire Barrier 2000 as both an adhesive for the Fiberfrax to the Firewall and the Foil to the Fiberfrax as well as any gaps. I'll do something similar to the tunnel as well, but will be Fiberfrax, insulation and then the foil... Anyone see any issues with this? Also where can I source 0.002" stainless foil? |
Foil
McMaster Carr has it...
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Side question... Is it a bad idea to use the self adhesive foil? I don't want the glue/adhesive catching fire.
Update - The self adhesive doesn't come in 24 inch wide so never mind. |
About to start on the Firewall and Tunnel with the materials I received today. Before I start punching holes in the firewall I wanted to check if I'm leaving anything off.
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You probably want a separate pass-through for the battery cable. Keep power wires away from sensor wires. I didn't want to take a chance on the cable chafing and possibly arcing on the firewall, so I used a marine insulated firewall pass-through terminal.
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I assumed the battery/power line came through the 1" Pass through on the right. And the left one was for all other wires...
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Good deal, I actually made some solid progress on everything last night. Going to order another 3/4 inch pass-though for alt air/ and heater cables. Also need to order some Stainless Steel pull rivets to attach these passthroughs. Tried to use screws but the backside is really close to some brackets so pull rivets will work best.
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