Wire rope Maintenance and lubrication.

[Tomo]

Having a few people interested in maintenance and what to do to help check wires for safe use - I've gone through my text books and what not, and also came across these two PDF files I think may help you a bit.

 

This one talks about lubricating and the pro's and cons of it -

 

http://www.cwrmglobal.co.za/downloads/OIPEEC.pdf

 

And this one is talking about lifting wire ropes and slings, but it may give you an idea of what not and what to do.

 

http://www.certex.com/products/saftey/Use_and_Care.pdf

 

Will find some more relevant stuff when I get the chance - some more experienced users may want to jump in here and help out also - I'm only going from my text books as I said, and sieving what is out there on the net.

 

Hope it's helpful

 

 

[Guest Crezzi]

A few years back we published (with permission) a BHPA article on flying wires in the Caboolture Microlight newsletter - http://members.dodo.com.au/~pilotcrezzi/docs/HangerTalk_2005_09.pdf (on page 7)

 

Cheers

 

John

 

 

[KB59]

Hi

 

I fly a WB 582 Drifter

 

On returning from a 2 hour flight on Sunday morning I received a call form Maj ( Ross ) telling me about the unfortunate accident regarding the Drifter. Ross suggested that I should check my wires.

 

Ross (thanks for the heads up.)

 

This is the sort of cross checking we should all be doing with our follow flyers.

 

Anyway more on that in a later post.

 

Checking some of my text books and on the net I found reference to Aircraft grade wirer.

 

5/32" breaking strain of 1088kg divided by a standard safety factor of 5 = 217kg

 

3/16" breaking strain of 1678kg divided by a standard safety factor of 5 = 335kg

 

1/4" breaking strain of 2902kg divided by a standard safety factor of 5 = 580kg

 

Now if you look at my Drifter 450kg MTOW x 6G = 2700kg divided by 12 wing attachment points 4 king posts and 8 wires I get 225kg per attachment so if you wanted to static check the wires you should test to no less than 225kg.

 

Now the wires on my Drifter measure 4.2mm which is in between 5/32" and 3/16" so when they certified the Drifters to 6g+ they got it right but cut it fine in my view.

 

As anythings age that safety factor gets eaten up so the condition of flying wires is very important.

 

Now looking at Rudder cables

 

An average 80kg person should be able to easily squat press 50kg so that adds up to 130kg divided by 2 = 65kg each leg so I would think you could apply 65kg on a rudder cable when the poo is hitting the fan and you brace with both legs against the seat. You might not mean to but who has not done it at some stage.

 

Am I looking at this the right way or have I got it ass up.

 

Ken

 

 

[Vorticity]

Why a factor of safety of 5? Was that used or is it a standard thing for cables?

 

 

[KB59]

Hi Vorticity

 

The factor of 5x is a general safety factor used with wire cable where human life is at risk.

 

Cable is rated ( Breaking Strain ) and then ( Safe Working Load ) with the safety factor being the difference,

 

In my research I found reference to 8x and 10x but generally 10x would be used where a single cable on a drum is used and human life is at risk ( say rescue winch operations ) cable for this use would also have a use-by or life of some type applied to it.

 

Ken

 

 

[Yenn]

In my days as a rigger, the safety factor was always 6. So there doesn't seem to be any concensus there. For the lightweight Stainless Steel wires used in some aircraft I reckon 10 would be just enough. Just one broken strand is enough to condemn a S.S. wire rope and they are not always easy to spot. One strand will drop the load bearing capacity by over 5% and if one is broken, others will not be far from breaking.

 

 

[Tracktop]

http://members.dodo.com.au/~pilotcrezzi/docs/HangerTalk_2005_09.pdf[/url] (on page 7)Cheers

 

John

:thumb_up:

 

 

[Tomo]

One strand will drop the load bearing capacity by over 5% and if one is broken, others will not be far from breaking.

Yes that's right, wire rope is a lot like a family - if someone is broken the strength isn't there.

 

 

[Tracktop]

http://members.dodo.com.au/~pilotcrezzi/docs/HangerTalk_2005_09.pdf[/url] Cheers

 

John

Nice read, got any more?

 

 

[Guest Crezzi]

Nice read, got any more?

Glad you liked it. I'm afraid some have been lost to history but you can read the ones I still have at Caboolture Microlights Home Page - follow the link to newsletters

 

Cheers

 

John