[TowerTalk] K-factor Revisited

[Guy Olinger, K2AV]

I don't think I missed the point. 

True, I didn't use the term mass.

True, weight is felt down. My 2 year old grandson knows that. Weight
is *mass* felt down because of the acceleration necessary to oppose
gravity.

HOWEVER....

The point was whether one could derive a safety factor, 

      however APPROXIMATE, 

from a simple arithmetic calculation from antenna characteristics
which every antenna manufacturer supplied accurately, without the
temptation to exaggerate or downplay.

Therefore, since...

At distances from the center of the earth associated with breathable
atmospheric levels, one can routinely equate mass and weight with only
percentage point errors. So if one needed "mass" in an equation, the
figure gotten from "weight" approximates well. The "weight" ALSO sets
the proportion of inertia encountered when one tries to start the
antenna turning. 

One can also show an *approximate* relationship between weight and
wind loading. This occurs because almost everything is tubular
aluminum, and the more weight the longer or thicker the aluminum must
be, therefore more square feet.

If for no other reason, the square factor you quote is not an issue
because for *each* rotator they sell there is a certain length boom
that probably maxes out the rotator given what maximally could be put
on it. Then you use that length in the squaring when you pick the K
factor for that rotator. EG, each individual rotator is individually
fudged.

True, if one wanted to stress something up to 99% of rated max, ala
turbine blades in jet engines, one clearly cannot do that with a K
factor derived as specified.

I am pretty sure they picked it to make sure the user got *nowhere
close* to stresses that would eat up gears and guts in the rotator. 

My point has been all along that the K factor will set a safe maximum
if the Yaesu people picked the individual multiplier right when they
determined the max for each rotator. 

(The cynical will surmise that Yaesu did it so they wouldn't have to
pay if we put the maximum weight on the rotator that didn't actually
punch the mast through the bottom ... probably the least weak
characteristic in the rotator. They might be right.)

Manufacturer says rotator is too small if boom times weight exceeds X.
Do what the manufacturer says. Go beyond on your own money. This one
ain't that bad.


On Mon, 01 Mar 1999 18:20:41 +0000, alsopb <alsopb@gloryroad.net>
wrote:

>Guy,
>
>You missed the point.  Weight acts down.  It has nothing to do with the
>rotational moment (unless you are rotating the boom horizontal to
>vertical) or torque required to rotate the antenna.  Mass is the correct
>term.  The moment of inertia must be used. It goes as r*r.
>
>The K factor apparently is either blowing smoke or has to do with the
>amount of torque required to break the housing due to vertical ups and
>downs.
>
>73 de Brian/K3KO

73, Guy
--. .-..

Guy L. Olinger
k2av@qsl.net
Apex, NC, USA

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