On 5/10/2020 6:28 PM, Al N6TA wrote:
I just posted on the Steppir Group but though to try here as well:
Can anyone provide advice regarding the need for the lateral support
options for the standard tilt plate when the 4 el with 30/40 dipole is
used?
I have the support truss for the one 30/40 dipole element and the boom has
the normal truss.
First of all, the term "support" is misleading. When not mounted
on a tiltplate, your SteppIR doesn't need lateral support.
If you analyze the tiltplate assuming the antenna is a rigid body,
it all works according to Hoyle. But the antenna isn't a rigid body,
especially an antenna with a very flexible boom like the SteppIR or
even worse my legacy MonstIR. In that case, the mechanical problem
is called "unstable equilibrium". As soon as the antenna tilts
slightly, the boom flexes in the direction it takes to "amplify" the
tilt. So if the wind blows the antenna so as to force the plates
apart, it tilts and is stopped by the Karlock, and never comes back
to level until the wind blows the other way. Without the Karlock,
it would completely tilt back and the elements would go vertical.
Been there, done that :-)
The lateral support truss works in one direction only. Properly
installed, it prevent the boom from bending the direction that
causes the tipping. It completely allows the boom to flex in
the opposite (harmless) direction where it tries to squeeze the
plates together. When you install it, have some tension even in
the absence of the wind, so the that the boom is always curved
a little.
Hope that helps. Think about it...
73
Rick N6RK
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