Guys,
I'm trying to figure out how this K factor relates to anything physical.
Obviously it is a starting torque limit. However, it is a torque that
appears to be computed based upon an "arm" of the turning radius and the
entire antenna weight (boom and all!) being at that point. Actual
antennas have their elements weights at the end of 1/2 the boom lenght
and the middle elements of 3,5, odd element arrays contribute
significantly less to the required torque. There doesn't seem to be any
overt inclusion of the wind resistance one needs to overcome to start
the thing turning (except that the K factor seems really non-physical
and probably severly limits the size of the antenna you can turn). This
wind resistance would be proportional to the antenna surface area.
If I were the suspicious type I'd conjecture that this K-factor was
included as an after thought (CYA) when rotors started failing and some
way was needed to show that the buyer unknowingly exceeded some spec or
other.
Can anybody out there explain the derivation of the K factor?
IMHO, what we really need is a rotor foot-pound limit and a quickie
little program to calculate the starting torque of our antenna
(accounting for wind in some way) given the element lengths, weight
distribution, boom locations etc.
I think the starting (or stalling?) torques of many popular rotors were
published in the last couple years in CQ or QST. It would be
interesting to compare these numbers to starting torques needed for
popular antennas.
de Brian/K3KO
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