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Re: [TowerTalk] Rotor damage prevention: soft pins or simple shockabsorb

To: "Mark ." <>,
Subject: Re: [TowerTalk] Rotor damage prevention: soft pins or simple shockabsorbers
From: Jim Lux <>
Date: Thu, 27 Oct 2005 11:10:34 -0700
List-post: <>
At 10:22 AM 10/27/2005, Mark . wrote:
>Hello TowerTalkers,
>A couple of thoughts occurred to me after reading this latest thread on a
>perennial subject. There's quite a longstanding debate on whether to pin a
>mast or not.
>That still doesn't address the need to provide for some shock relief to
>dissipate energy and limit the forces of starting/stopping the rotation, and
>wind-oscillation torquing. To some extent, the springiness of antenna
>elements helps, especially if you have ropes through the centers.
>The shaft couplings mentioned are an elegant way to approach this,
>especially for larger arrays.
>It's much better to design a mechanical system to flex in some way and
>harmlessly disspiate shock energy rather than make it so rigid that
>destructive forces build up.
>How about an eleastomer sheet, such as, say, 1/4 or 1/2" sheet rubber, to go
>between the base of the rotator and the rotator shelf?

Or, something like standard rubber shock mounts made for mounting 
mechanical equipment?
They come in various forms with various bolt configurations, but are 
basically either a nut, a bolt, or a sleeve that's encapsulated in some 
appropriate substance (rubber, urethane, etc.).

Check the stuff starting on page 1218 in the McMaster-Carr 

you probably want the ones designed for shear loads.

>The holes in the rotor mounting shelf would have to be drilled oversize to
>allow rotational movement of the bolts and rotor together. You would use
>washers under the bolt heads, before they come up and through the rotor
>shelf, then torque them only enough to apply some friction between the rotor
>and shelf.
>You might have to replace the bolts with longer ones, and use two nuts (or
>short stubs of threaded rod) under the shelf, such that you could torque the
>assembly to a mid level, and lock it with the second nut.


Like many other things, hams' problems aren't unique, and there's a lot of 
stuff out there to help solve it.  That's why the McMaster Carr catalog is 
so handy, if you've managed to score a paper one... you can browse through 
it and find ideas.

Jim, W6RMK


See:  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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