[K4RY] Did the antenna rotor get examined?

[Kris Kirby]

I looked at these pictures and noticed a few things I want to point out. 
Far be it for me to criticize the choices that one makes on installation 
and the age of the hardware...

Anything with rust on it now is likely to be non-galvanized steel, or 
galvanized steel that is approaching the end of it's useful life. If the 
rusted parts are loosened, it's likely they will shear and not be useful 
for replacement. Further, the assembly shows signs of a loose shackle at 
the top, so it would be wise to find a way to reinforce that part, 
perhaps with a set screw into the mast itself. However, that will just 
work as a shear pin in high winds, so it would be wise to calculate out 
appropriate values. It's possible to replace the hardware up there with 
stainless steel hardware, which can be reused, but the stainless has to 
be sized appropriately and a torque wrench should probably be used to 
prevent galling the threads of those parts. 

In the case where previous records have been lost as to the construction 
of various pieces and thier sources, it may be a better idea to 
completely replace with materials of known source and quality. This is 
quite an engineering challenge as T6160 aluminum has certain costs, 
benefits, and kips limits and 316 stainless has other limits and tends 
to develop stress cracks as metal fatigue over time. Titanium is pretty 
hard to get, unless you know of a source for good, space-rated surplus 
structural tubing. 

IANAME, however. 

Then you get into issues with grounding and dissimilar metals, where all 
the copper must interface with stainless before it interfaces with 
aluminum or any other sort of joint.

In general, "standard" steel is going to come apart at 10+ years, Home 
Depot zinc is going to come apart a little bit longer, galvanized a 
little bit longer; heavy, hot-dipped galvanized a little bit longer, and 
stainless will be reusable at X number of years provided the threads 
aren't galled or it's been overloaded. The time frames shorten when you 
have corrosive environments like Birmingham's air used to be before some 
of the steel factories shut down. 

Also, RG-393 jumpers tend to survive corrosive environments such as 
power plant smoke stacks, because the jackets are pretty resistant to 
that sort of thing. 

--
Kris Kirby, KE4AHR
Disinformation Architect