Rudy,
I would consider changing the mast clamp to something like what K7NV or
K7LXC produce, assuming they will fit the Prosistel rotor.
As to question 1 below I'd use a bolt slightly softer that the mast. The
bolt is a less expensive replacement if it shears.
On 8/28/2016 11:47 AM, Rudy Bakalov via TowerTalk wrote:
I am getting really tired of my mast slipping during major wind gusts. The mast
is supporting a 4 el 40m M2 yagi and a 6 el M2 KT36XA. The clamp is the
standard clamp that comes with the ProSisTel PS61D rotator.
So the question is if I should pin the mast to the rotator clamp using a M8
bolt. The clamp has 8 bolts, but clearly the friction between the clamp and the
mast is not sufficient under extreme conditions. My one and only concern about
pinning is that the hole in the mast may weaken the mast. The PST61D is rated
for 36 sq.ft so, right or wrong, I am not concerned about the wind damaging the
rotator.
If you suggest I pin the mast, there are two follow up questions:
1) What grade bolt should I use for the pin? The mast is 120K psi. Should the
bolt be rated for less (e.g., Grade 5) or more (e.g., Grade 8 or 10.9) psi?
That is, do I want the bolt to break before the mast does under extreme
conditions?
2) Further, is it OK if the bolt is zinc plated? I could not find stainless
steel Grade 8/10.9 M8 bolts. Is the contact between zinc and the mast going to
lead to corrosion?
Rudy N2WQ
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R. Kevin Stover
AC0H
ARRL
FISTS #11993
SKCC #215
NAQCC #3441
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