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[TowerTalk] Effective Moment/K Force & Yaesu rotators

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Subject: [TowerTalk] Effective Moment/K Force & Yaesu rotators
From: (Kurt Andress)
Date: Wed, 11 Jul 2001 13:05:46 -0700
FWIW, I agree with what Tom and Steve said.

I haven't seen the wording of the new Yaesu method of calculating the K value
including the mast. The mast is not currently in the description on their 
However it says it should be done is how it should be done to correlate with 
empirically derived rating method. The thing I read says to check "K" and the 
area rating, and if both are within limits, it should be good to go. But, they 
many others don't indicate what antenna area they mean, so ???? Since it is
empirically based, I expect they mean whatever antenna area the antenna mfgr's 
using when they collected the historical data to come up with the latest rating

The adding the mast, and lowering of the acceptable "K" value means they found 
that the old numbers were resulting to too many failures(whatever that means),
regardless of any other more meaningful or relevant physics.

This is just a method to base a decision on with available (more or less) 
nothing more. 

Does a small difference either way a big deal? Nope.
Will going up one capability level in the rotator series be better? Depends on 
definition of better.
Will overkilling the rotator make it last forever? Maybe, but probably not.
This is educated guessing, to get a ballpark estimate on how large a chunk of 
"forever spectrum", the rotator gets to occupy.

73, Kurt

> >
> >  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
> wrote:
>     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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