[TowerTalk] Orion mast clamp question

[Richard (Rick) Karlquist]

The other side of the spectrum is that the "large clamping area"
clamps, such as K7NV, K7LXC, and Slipp-Nott suffer from several
serious limitations.

1.  Static friction ("stiction) according to text book theory
is given by the product of the coefficient of stiction times
the force.  It is independent of area!  At least in theory.
Therefore, the increased area is only relevant to the extent
that it somehow enables more total force to be applied.

2.  #1 is actually good news, because real "two inch" masts
are somewhat larger than that due of galvanizing etc.
The resulting imperfection reduces the effective area, which
fortunately is "irrelevant".

3.  A K7NV clamp has IIRC 5 clamping bolts.  The torque
on the bolts can be used to calculate an upper bound
on the clamping force.  Some of the torque is due to
friction, and doesn't count in producing force.

4.  If the mast is too small vs "2 inches", the clamp
ears might touch, in which case the force is limited
by the pliability of the metal, which is hard to account
for.

I have a K7NV clamp on my N7NV prop-pitch and I have
a Slipp-Nott on my Monstir.  The antenna still turns
somewhat in strong winds, because either the rotor/mast
clamp slips, or the 4 U-bolts plus Slipp-Nott
at the top of the mast slip, or the prop-pitch free wheels.

Rick N6RK