[TowerTalk] [Bulk] How to "lock down" wire rope clamps/clips?

[Grant Saviers]

If wire rope clip nuts loosen it is probably because they aren't 
installed properly.  Check the Crosby publication at 
http://www.thecrosbygroup.com/Portals/0/docs/manuals/9992320.pdf

Torquing to the correct level and then re-torquing is needed and Crosby 
even recommends a re-torque after the expected load has been applied. 
Like most structural bolt-nut assemblies, the proper torque is needed, 
and then they don't loosen, unless it is a high vibration or thermal 
cycling application.  Then other means are used to prevent loosening, 
but not the common split ring lockwasher (which is just about useless).  
Then there is the difference in quality between Chinese clips and forged 
Crosby or Chicago.  And Zn plated vs hot dip galvanized.

Another factor is the wire rope being used and its compressibility, but 
I don't think a problem with 1x7 EHS.  Clips on Phillystran are a bad 
idea since the plastic cover extrudes (creeps) slowly from under the 
clip and many re-torquings are needed to cut through to the Kevlar, 
which is close to steel in modulus of elasticity.

The full strength of the cable is not attainable with wire rope clips, 
only about 80% in wire rope sizes of interest to amateurs. This and the 
variability of installation of clips is one reason the vast majority 
commercial/industrial cables are terminated with Nicopress, swaged, 
Crosby sockets, grips, or taper lock fittings. Many are explained in the 
Crosby pdf.

The nylon in Nylocks does degrade from UV, unless the UV resistant 
versions are used.  It helps to install them so UV exposure in 
minimized, which is nut down.  Structural bolts are usually installed 
nut up so it is more obvious if they fall out.  For antenna assembly 
there aren't many reasonable choices other than Nylocks.

All things considered I think wire rope or Phillystran grips are the way 
to go instead of clips.

Electrical tape would be useless to prevent loosening.  Red (271) 
Locktite installed properly might work well, but is essentially a 
permanent lock.

Grant KZ1W


On 11/27/2015 7:58 AM, kr2q at optimum.net wrote:
> Over the years, it seems that most antenna manufacturers have moved to using some form
> of Nylock nuts (the nuts with the nylon insert for "high vibration" applications).
>
> I have seen this on my Cushcraft XM series monobanders, on my Optibeams, and most recently
> on my SteppIR (DB36).
>
> With respect to the latter, the cable clips just use a single nut to compress down on the wire
> cable. There is no locking nut, no lock washer, no Nylock, etc.
>
> Why is this?  I have heard from others that this can be, and has been, a point of failure.
>
> What method would you suggest to ensure that these wire rope clamps do not loosen up over time?  Just electrical tape?
>
> RSVP
>
> Thanks
> de Doug KR2Q
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