I speak from personal experience (in trying to test to destruction) in
saying that the AlfaSpid rotor wouldn't have any issues handling these kind
of side loads. The rotor design has 2 steel pipes that overlap each other,
with substantial bearings at both levels to take any side torque. I have
had, on test here for the last few years, a 6 el 20m yagi on a 48' boom
mounted entirely outside the tower on this rotor. While not perfectly
balanced (but reasonably close) it still experiences significant side forces
when the wind is blowing. This test was mainly to allow us to suggest to
owners of towers (usually crankups) that were too small to permit mounting
the rotor inside, that they could still mount significant wind loads on our
rotor mounted above the tower.
73 Don
VE6JY
----- Original Message -----
From: "Al Williams" <alwilliams@olywa.net>
To: <towertalk@contesting.com>
Sent: Saturday, October 01, 2005 14:20
Subject: Re: [TowerTalk] [SteppIR] boom balance
> How important is it to balance the load on a rotator and which rotator is
best able to withstand a completely one sided load?
>
> I have a bracket/platform under construction that will bolt to the second
section of a 70' crankup tower (which puts the platform at about 35'.
> The rotator will be mounted on the platform at about 15 inches from the
face of the tower. The mast-to-boom plate will hold the boom at the end of
the boom (making the completely one sided load). The boom will be a
modified 2 el Steppir boom that places the reflector about 12 inches
> from the rotator center making the boom into a swing-away arm? This will
allow the Steppir to rotate over 180 degrees before the reflector bumps into
the tower legs. The capability of the Steppir to reverse direction will be
used to obtain the other 180 degrees. The purpose of this design is to
avoid interference between the 2 el Steppir elements and the leads coming
down from the upper antenna as the leads will be on the opposite side of the
tower from the 2 el Steppir.
>
> This design will result in an unbalanced load on the rotator of about 15
ft-lb from the reflector and about 75 ft-lb from the director and boom.
>
> I will appreciate opinions on what the damage to the rotator may be and
which rotator(s) would be able to withstand the unbalanced load.
>
> k7puc
>
> ---- Original Message -----
> From: Mark Klocksin
>
>
>
> I just installed a Ham IV rotor to turn my 3-element SteppIR.
>
> Somewhere in the rotor information I read that the load should be
> balanced.73,
>
> Mark WA9IVH
>
>
> _______________________________________________
>
> See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless
Weather Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any
questions and ask for Sherman, W2FLA.
>
> _______________________________________________
> TowerTalk mailing list
> TowerTalk@contesting.com
> http://lists.contesting.com/mailman/listinfo/towertalk
>
_______________________________________________
See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless Weather
Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any questions
and ask for Sherman, W2FLA.
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