[TowerTalk] Why galvanized crank up cables instead of stainless?

[K8RI]

On 10/9/2012 10:27 AM, K7LXC at aol.com wrote:
> t/>  Having just replaced my crank up cables (in case they  migh
> be rusted internally), I am wondering why stainless steel
> cables  aren't used.  It would seem that they would avoid
> the latent rust  issue.  I realize that they are not as strong,
> but they could simply be  sized appropriately.  Is it the
> case that they may still rust, just more  slowly?  Would
> they somehow wear out and break internally?  It  would be
> great to merely have to inspect the cables for obvious  broken
> strands and never have to replace them on a preventative basis.
> Can  someone explain this?  Don't airplanes use SS cables?
>
>      Sure, but they don't go thru the forces and cycles  of crank-up cables.

Agree with everything except the cycles.  Aircraft control cables 
(rudder, ailerons, and elevator) are in an almost constant state of 
motion while in flight and the bending takes place over very short spans 
on each of the cables where the pulleys are located.  OTOH they are not 
heavily loaded nor under much tension.  They must be replaced at any 
sign of strand failure which is rare.  They are "supposed" to be 
inspected during the annual (yearly) inspection.

I do not know if they are impregnated with lube.

73

Roger (K8RI)


>
>      IMO there are 2 factors. One is cost since  everything is determined by
> it. And the second is the fact that worked SS cables  under load will gall.
> That is, pieces of the material will be deposited on other  strands and
> eventually you have a hard spot in the cable. This might be  prevented by
> REGULAR cable lubrication but I don't think it's worth the  potential problem.
>
>      SS nuts and bolts will also gall. That's why you  have to use some sort
> of non-seize on the threads.
>
> Cheers,
> Steve    K7LXC
> TOWER TECH
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