[ARC5] Tuning Cable Question

[Mike Hanz]

Then obviously you handled them too gently. :-) In installation, they 
are cut 3/8" per foot longer than the inner cable, then slid back 
(compressed) until they are slightly shorter.  Wait a few years with 
rain and humidity, and they're frozen in that position.  The cure is the 
same - soak in penetrating oil and then exercise per Ken Gordon's 
instructions for getting up in the morning...heh, heh...

Your other wish, to shorten the sheath and inner cable to a different 
dimension, unfortunately requires some sort of minimal level of 
tooling.  I can't think of any way around that.

73,
Mike  KC4TOS

On 6/4/2014 9:40 AM, Mike Everette via ARC5 wrote:
> Hi Mike,
>
> I made a typo when composing the last message.  Meant to say that the sheaths were shorter than the inner cables, not longer than the inner cables.  I think the sheaths ended up more than 3 inches shorter.
>
> When I removed the cables, they had to be worked through holes in several bulkheads and not "yanked" out. The ferrules would have hung up otherwise.
>
> These cables were in terrible shape.  I ended up salvaging the splines from three ends (driving out the pins), along with the ferrules, and mating the splines with 1/4 inch shafts to make some real nice local tuning knobs.  Would have been great if I could have figured out a way to shorten the cables to something like 12-18 inch length for a display setup tuned from the control box, but that would've required special tools that I didn't have and had no access to.
>
> 73
>
> Mike
> WA4DLF
>
>    
> --------------------------------------------
> On Tue, 6/3/14, Mike Hanz <aaf-radio-1 at aafradio.org> wrote:
>
>   Subject: Re: [ARC5] Tuning Cable Question
>   To: "Mike Everette" <radiocompass at yahoo.com>
>   Cc: arc5 at mailman.qth.net
>   Date: Tuesday, June 3, 2014, 1:26 PM
>   
>   On 6/3/2014 12:46 PM,
>   Mike Everette wrote:
>   > I have several
>   tuning cables which were pulled from a scrapped Twin Beech
>   (SNB-5) wherein the metal sheaths had separated or unraveled
>   during bends.  I could tell that the actual spline cable
>   was noticeably shorter than the sheath and would have been
>   even more so had the sheaths not opened up.  Another SNB-5
>   from which I removed an ARC-5 setup had a similar problem --
>   really tight tuning cables which were almost impossible to
>   get back onto both the receivers and control heads without
>   stretching the sheaths out straight and pulling on them like
>   mad.  Even then it was not easy.
>   >
>   > Now, metal doesn't shrink... does
>   it?  Hmm.  Why would they have been so darn tight?
>   
>   I think you gave the
>   explanation in your first sentence..."pulled". The
>   
>   sheaths lengthen when they get removed from
>   an aircraft because that's
>   the easiest
>   way to do it...pull it out...hard.  Since they are spiral
>   
>   wound, they lengthen when force is applied
>   to them. Since the inner flex
>   cable
>   isn't part of that pulling force because it is floating,
>   and in
>   any case is more resistant to
>   tensional changes in length, it stays the
>   same length, so you end up with an inner cable
>   that is shorter than the
>   outer sheath.
>   That's the way it was cut in the first place - 3/8"
>   per
>   foot to begin with.  On new sheaths,
>   the spirals are lubricated and you
>   can push
>   and pull the thing to get it to shorten and lengthen quite a
>   
>   bit.  After years in an aircraft, most of
>   them rust in place and lose
>   that axial
>   flexibility, so pulling them just forcefully extends them to
>   
>   the max and they don't return like a
>   new cable will.  You can get them
>   loosened
>   up a bit with Kroil or other penetrating lubricant, but
>   it's
>   hard to get the original
>   compressional length back completely.
>   
>   Or, at least that's been my experience.
>   :-)
>   
>   73,
>   Mike
>   
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