In a message dated 7/10/01 10:16:59 PM Pacific Daylight Time,
franknorton@home.com writes:
> I messed up that post about my confusion about calculating "K" tremendously
> by not putting in the source of my confusion--> The Yaesu web site, and
the
> Texas Tower web site both leave out the mast in the calculation of the "K"
> factor , made sense to me. So I purchased my G1000DXA and waited for the
> UPS truck to bring my shiny new rotator, which I purchased with this new
> "scientific system" to assure my "safety freak" side all factors are
> covered. But when I open the box and read the manual there it is--> A half
> page explanation (with diagrams) that suddenly includes the weight of the
> mast in calculating the "K" factor. I didn't understand why--so I started
> making phone calls. I called Texas Towers and they didn't know for sure
> which was correct, next I tried Vertex and had no luck getting anyone but
> marketing who him-hawed around really not knowing what to do.
>
> My brother is a C.P.E. but not a ham, he felt that in engineering a
> structure he would not consider the mast, but since he did not have access
> to the engineering information on the rotor he could not say whether the
> vertical loading should be included in the "K" factor or not. Yaesu's own
> literature contradicted itself. I still have not received a reply to my
> letter from Vertex/Yaesu.
>
> I would like to feel completely comfortable with my decision to leave the
> mast out of the calculation, but if something happens and the rotator
> clamshell fails, and the antennas fall damaging part of my home......what
> will the insurance company determine? God forbid what if someone were
hurt,
> or killed! The safety freak inside me has not been sleeping well waiting
> for an answer from Vertex/Yaesu (now 6 weeks overdue).
>
> Thanks for your email at least I know there is someone else who feels that
> the concentric force of the mast is insignificant compared to the
eccentric
> torque of the antennae when calculating "K".
>
> At 10:31 AM 7/10/2001 -0600, N4KGwrote:
> Hi Frank,
>
> I have never understood why weight of the mast is a factor since
> it has such a small radius. Also, the K factor is not a "real"
> moment but a ficticous number that "sort of" indicates rotor
> capability. The actual moments depend on WHERE the weight
> is distributed. Empirical evidence is still the best criteria for
> rotor selection, unfortunately.
>
> Tom N4KG
Frank - chill out and get some sleep. You're overreacting and I'll bet
you a nickel that you never get a response from Yaesu/Vertex so don't worry
about it.
Tom is correct. Effective Moment and K Force is an ESTIMATE from the
factory based on their knowledge of the antenna loads and rotator capability.
Since EM/KF is weight times turning radius, the mast is insignificant.
For example, a 70 pound 2" mast would have an EM/KF of 6.36 ft-lbs. The
margin of error for an EM/KF is *much* higher than that.
The use of a foot-pounds of torque spec for rotators is more useful than
the old "square footage" estimate since two antennas of identical square
footage can have drastically different wind-induced torque forces and EM/KF's.
BTW I picked up Yaesu's latest rotator brochure and there have been some
changes to the specs. Some of the models now need 6-conductor control cables
where they used 5-conductor previously. I heard they changed to DC motors or
something like that. Also, the K Force for the G-1000 has been down-graded
from 2020 ft-lbs to 1664 ft-lbs.
Cheers, Steve K7LXC
Tower Tech
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