The Benefits of Using Safety Wire for Secured Fasteners

[AME2]

I have a question about safety wire. Safety wire is used to secure fastners to prevent them from loosening. What are the benefits of the twist in the wire between points?
Here is a explanation of safety wire."[URL
http://en.wikipedia.org/wiki/safety_wire
I read but don't see a clear picture. perhaps a better view point?

 

[Danger]

Welcome to PF, AME2.
The twist is primarily to retain tension in the wire. If a long single loop was used between bolts, it could stretch enough to allow loosening.
As a side benefit, in non-official applications, the act of twisting can weed out a substandard wire because it will break during application.

 

[AME2]

I understand the side benefit.

Would the wire with no twist be just as efficient? I do not understand the loop and why left over right when you safety wire.

 

[Danger]

I understand the side benefit.

Would the wire with no twist be just as efficient? I do not understand the loop and why left over right when you safety wire.

To the first question, no. To the second, I was totally unaware of any such requirement. It's probably just because a right-hander made the rules. (I can't see that it has any correlation with the bound bolts being right-hand threaded, since the wire merely suppresses rotation.)

 

[nucleus]

The following link gives a better picture. Twisting the wire makes it stronger, although a single wire is allowed in some circumstances.

http://www.ultralightnews.com/pilotslounge/safetywire.htm

 

[Danger]

That is an excellent link, Nucleus. I've bookmarked it for future reference.
I still didn't see anything about having to twist clockwise, though, other than the illustrations showing that. That leads me to think that the automatic twisting pliers do it, but that it might not be necessary for hand-twisting.

 

[nucleus]

Danger
If you look at the examples with three bolts lock wired together. The direction of twist from the second to the third unit is counterclockwise on some of them. It comes down to where the bolts ended up after torque. It is wired counterclockwise in order to keep the loop in position against the head of the bolt and on others it is wired clockwise for the same reason. Also on the final pigtail is the same rules apply.

So the twist is really both ways – it just makes it look better. There are also lock wire pliers that are reversible or you can do it by hand.
This is covered in AC 43.13-1B Top of Page 7-23.

 

[Danger]

I see that now. Thanks again for clarifying things.

 

[FredGarvin]

When I was taught how to safety wire I remember being told that it was indeed left over right. It has to do with the fact that 99% of the fasteners will loosen going in the counter clockwise direction which could cause a right over left twist to unravel and allow the single loop to pass over the top of the nut/bolt.

 

[AME2]

This is covered in AC 43.13-1B Top of Page 7-23

Indeed, that does explain it. Thanks nucleus

So the double-twist method is used to secure the wire around the bolt head. I also see the clockwise and counterclockwise reasons. Depending on which side of the bolt your on, you want the loop on the bolt head to remain in place by using the other wire as a block (to prevent the loop from rising up over the bolthead)


I guess the left over right rule is kinda out? I would'nt think the wire would come undone unless the wire broke.

No, as far as I know, the twist in the safety wire does not make it stronger. And it can only be as strong as it's weakest point, which would be the single wire through the bolt head. Twisting the wire weakens it.

I was thinking there might be some physics involved here that I was missing. Seems simple enough now.

sometimes you do want to sweat the small stuff.