[TowerTalk] PST61 Rotor Reliability?
garyschafer at largeriver.net
Tue Dec 12 22:08:28 EST 2017
I searched for the two part article but could not find it. I did find a
summary of it that he (Dick Weber) wrote in one of the DX journals that John
N5CQ supplied and some references that Kurt K7NV made to his work.
>From what I read I am wondering if there is some confusion on some peoples
part with Dick's explanation of how the wind forces on the elements
themselves does not cause rotational forces on the mast but all the forces
placed on the elements result in forces that are perpendicular to the
elements transferred to the boom "in line" with the boom. It does not matter
what angle the wind hits the elements at as the force generated is always
perpendicular to the element and in line with the boom.
He explains that (with a balanced boom) the element forces transferred to
the boom length result in a small amount of the boom forces seen as
rotational forces on the mast due to the amount of offset the boom is from
the center of the mast, usually a mater of 3 to 5 inches.
In this case a second yagi mounted on the opposite side of the mast would
offset this force which is not significant.
Seems the unbalanced boom is the greatest problem.
So the only other rotational force is from the boom itself if it is not
balanced (same length on each side of the mast).
It also does not matter where the elements are placed on the boom.
* balanced boom means equal wind exposure on each side of the boom from the
mast. A boom with the same diameter its whole length and mounted to the mast
at its physical center would be balanced to the wind even though it may not
be balanced mechanically by equal weight.
I would like to find the two part article as I am probably missing something
> -----Original Message-----
> From: TowerTalk [mailto:towertalk-bounces at contesting.com] On Behalf Of
> Wes Stewart
> Sent: Tuesday, December 12, 2017 11:20 AM
> To: towertalk at contesting.com
> Subject: Re: [TowerTalk] PST61 Rotor Reliability?
> See the two part article, "Aerodynamic Balancing" by Dick Weber, K5IU in
> Summer 1994 and Winter 1995 issues of Communications Quarterly.
> On 12/11/2017 7:34 PM, Gary Schafer wrote:
> > I have from time to time seen it professed that mounting two antennas
> > opposite sides of the mast will equalize the torque supplied by wind.
> > The only thing mounting on opposite sides of the mast will do is
> > GRAVITY forces on the mast (that try to bend it over) which will be
> > small differences given only a few inches distance apart.
> > Torque is rotational. Both antennas are going to exert the same amount
> > torque no matter which side of the mast they are on.
> > What am I missing here?
> > 73
> > Gary K4FMX
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