Safety wiring

[mikeavison]

A lockwire has very limited ability to resist a nut turning, in my view.  If you were in a hurry you'd snap them easily by just undoing the nut or bolt by driving a ring or socket over the wire and undoing the particular fitting. Yes they are supposed to be fitted in  regard to the direction they unwind being immediately noticed as the wire would have to break, before the Bolt moved any real distance. It is NOT any guarantee the bolt has been torqued to the right setting. that's often done with a dob of (usually) yellow paint but that's not foolproof either. I think lockwiring provides a  visual check nothing has moved since it was lockwired and not a lot else. Nev

 

 

 

It's actually a force of a very small order compared with the torqueing force and any force required to undo most nuts that are not loose, already.  You only have to break one of the two wires through the bolthead. On a filter it's got a much bigger radius, To be fair many locking devices don't have a lot of strength in their own right. A split pin and castellated nut often permit adjustment, and the nut is not tight at all. Some others have a preload and may be pinned or staked into a groove to lock them. Nev

 

This is to misunderstand how a bolt works. When a bolt comes undone during use, the force retaining it is not the torque applied when fitting it, it is zero. When you tighten a nut onto a bolt it stretches the shank of the bolt (it is elastic). This puts a constant force holding the items together. When there is vibration it causes an oscillating force on the bolt shank, the combined effect is that the net force in the bolt shank increases and decreases around the mean (torqued in force). If the vibration is strong enough the peaks and troughs of the oscillation are greater than the torqued in force, at which point there is no force on the face of the nut during each trough. Of course the vibration does not affect lock wire or loctite in the same way so they tend to keep the nut from turning (notwhithstanding any fatigue and shear effect). 

 

Incidentally I believe the  reason loctite and wire etc are used so much more on aeroplanes than (for instance) tractors, is that the components are made very much lighter, thinner and so less strong, and unable to withstand the compressive force of a highly torqued bolt. Look at the torque setting on bolts for a wooden prop, barely finger tight let alone hand tight!  Another example is where a bolt is put through a hole drilled in an aluminium tube.

 

 

[facthunter]

The applications you describe need positive nut locking. Not  Lockwire. A normal "tensioned" bolt NEVER has NO force . If it did the join (Faces in contact) would fret, leak and fail quickly. Wooden props and hollow Al tube can't be tensioned to any high extent or the part would just deform.(crush).  A tensioned bolt involves a concept of"preload" where the clamping force is always well above any that would allow relative movement of the parts  regardless of whether it's on an aeroplane or a tractor. Nev

 

 

[spacesailor]

But Locktite type glue

 

Will let the nut & bolt rotate  without loosing one end, or the other end getting into places that will cause nasty damage.

 

And can be undone easily.

 

spacesailor

 

 

[facthunter]

Yes it will do that but in Industry, servicing and manufacturing a consistent result has to be had. With loctite used "in the field" variables come into it that are hard to quantify.  Like what you use, how you prepare and use it and how old the product is. In single use suspension  bolts the thread is coated with small coated bubbles of loctite (or similar) in a paint which dispense the locking medium when the bolt is  tightened thereby ensuring a consistent controlled result. Nev

 

 

[Yenn]

Mention of a bolt though a tube is irellevant. The tube should normally have something inside it to take the compression. Often a tubular sleeve around the bolt, holding the walls from being moved.

 

 

[spacesailor]

If the nut is lock wired,  in a reinforced tube, the bolt can vibrate looose, if not fastend in some way.

 

spacesailor

 

 

[Downunder]

If the nut is lock wired,  in a reinforced tube, the bolt can vibrate looose, if not fastend in some way.

 

spacesailor

 

No, because the lockwire goes through the nut AND bolt.....

 

 

[spacesailor]

Mine only went through the corner of the nuts hex., with a clock-wise turn (wrap) to the next nut.

 

If it went through the nut & bolt I could have used a split pin !.

 

spacesailor

 

 

[Blueadventures]

Whenever I need to drill a safety wire hole in the head of a cap screw; I first nip up the bolt and decide which of the Allen head recess sides I'll drill to allow the best route to where the other end is secured. Allows for effective neat practical safety wire work. Cheers.

 

 

[spacesailor]

What do you do to the other end.

 

or

 

ARE YOU DOING studs?.

 

I have found it's easier to undo the bolt head, No lock-washer, under the bolt, than to undo the nut, scrapping the lock washer over the surface metal, scaring it.

 

spacesailor

 

 

[Dick Gower]

Can anybody provide an example where safety wiring has prevented an accident?

 

I am not really doubting that safety wiring is good etc. It is just that I don't know if it has ever worked as intended.

 

The origin of safety wire was to prevent the loosening of turnbuckles on control cables in earlier aircraft. 

With a left hand thread at on end and a RH thread at the other, combined with the direction of wrapping the cable strands during manufacture and the varying and reversing cable loads in flight, there are constant torque loads applied to the turnbuckle and lock-nuts at each end.  Many lives were lost as a result  of the turnbuckle unscrewing. 

Soft iron wire was used at first then brass became the convention before the Americans introduced stainless steel.

 

The lives saved would probably be in the 100,000's not including the Australian example where the

 

cable end fittings failed and the only elevator control was via the safety wire alone.