Single point safety wire anchor

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12notes

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I have a few places on the Hummelbird I'm building, like the elevator hinge pins and the fuel drain, where I need to safety wire a single point, but have nothing nearby to safety wire the bolt/pin to.

I've thought of a half dozen different ways to do it, but don't know what's strong enough and what's overkill. What is the standard or minimum anchor to make/install for safety wiring a single bolt?
 

Dana

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If there's someplace nearby that you can drill a hole, put a small (#8 or so) drilled head screw into the hole with a lock nut on the back, then use the screw as the anchor.
 

Pops

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If there's someplace nearby that you can drill a hole, put a small (#8 or so) drilled head screw into the hole with a lock nut on the back, then use the screw as the anchor.
Two places in the wings of the JMR were I did exactly that.
 

Pops

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I've seen this used on numerous hinge pins as well as your example.
For piano hinges, I cut the pin about 1/8-- 3/16" short on each end and drill a small hole and loop safety wire through the hole and twist. This way the wire can be removed and you can remove the pin if needed.
 

12notes

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No room for castle nut and cotter pin?
The bolts that could have that done, have had that done. This question was for the cases that isn't possible, either because it's not a bolt or there's no access to the back side.

This has been an eye opener, everything I thought of before asking seems like overkill in comparison to what's been suggested in this thread.

For fuel tank drains, Cessna just pops a ~.040" hole in the skin next to the drain. You'll get it.
The Cessnas (172N) I trained on had a bolt head near the fuel drain the safety wire went to. I'm guessing this means two holes so the safety wire can loop. If not, I'd need a picture to figure out what you mean here.
 

12notes

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For piano hinges, I cut the pin about 1/8-- 3/16" short on each end and drill a small hole and loop safety wire through the hole and twist. This way the wire can be removed and you can remove the pin if needed.
I like this method, simple and quick to implement. Thanks.
 

Victor Bravo

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I own a 1956 C-172,and that little hole in the lower wing skin next to the Curtis valve is there on mine too.

At the local aircraft surplus store I found special washers that were made for just this purpose. An internal star lockwasher with a small "tail" on it, and the tail had a hole in it for safety wire. So you can use this washer under a nearby screw or bolt, and have a built-in anchor. You could make this out of thin sheet metal pretty easy as well.
 

Pops

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On my straight tails C-172's there is a hole in the skin close to the Curtis drain valve like VB describes and you can bend the safety wire like an upside down "J". Go up between the drain valve and alum skin, then twist the wire so the small end of the "J" goes down the hole from the top side of the skin. Grab the wire with pliers when it comes down below the skin and pull extra length to go to the safety hole in the drain valve.
 
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