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Re: [TowerTalk] Another tt40 Wilson Tower Query

Subject: Re: [TowerTalk] Another tt40 Wilson Tower Query
From: Jim Lux <>
Date: Mon, 29 Aug 2005 09:49:39 -0700
List-post: <>
At 08:20 AM 8/29/2005, wrote:
>         Thanks to all of the Reflector readers who help identify my
>tower. It's the 2 section  Wilson TT40 with the dual section pipe-in-pipe
>mast with the optional free standing rotator base. At the risk of being a
>nuisance, here's the  second, more technical question!
>         The area for the installation of the base has what I believe to
>be unstable "soil". As a matter of fact it's not soil at all but various
>layers of rock used as fill to level an area to construct  a garage.
>Consequently, I  believe it cannot be  trusted  to be free standing and
>support the tower in the extended position.
>          The alternative plan is to tie into the garage eaves, utilizing
>a bracket, at about the 11' level for  lateral support.

So you're going to use the garage and its structure and hopefully it will 
spread the loads out over your "suspect" soil.  As opposed to a big hunk of 
concrete sitting in the ground (the usual tower base), where the soil is 
expected to keep the concrete in place.

Depending on where you live, presumably the fill would have to have been 
compacted sufficiently to resemble normal soil strengths or they wouldn't 
issue the permit to build the garage.  A call to the city or county folks 
might answer this one in a hurry.

Note also that some concrete base designs don't really depend all that much 
on the soil strength, but just on the mass.  (Imagine a giant cable reel 
buried in the dirt.  If the flanges on the reel are strong enough, the mass 
of the soil pushing down on them holds it in place.)
But, assuming you want to proceed with

>  Normally that
>wouldn't be any problem with a fixed  bracket, however, with this tower,
>the entire mast rotates around the rotator mounted at the base end. The
>question is what type of   bracket mounted thrust bearing device

You want a conventional radial load bearing here, not a thrust bearing.  A 
thrust bearing takes an axial load, and hopefully you're not supporting the 
weight of the mast on the eaves?

>   can be
>used to support the mast at the 11' level of the building  that will
>simultaneously offer  vertical support; and allow the mast to rotate
>without damage due to wear from metal to metal friction? The largest
>thrust bearing I've seen specific to this type installation is only 2"
>and too small for my application. If anyone has overcome this difficulty,
>please share your solutions. I have my own 15" lathe and welding
>equipment so fabrication is not a problem. The solution is probably
>going to be some sort of  bearing that will fit snugly around the lower
>level of mast that allows for unimpeded rotation.  Any assistance would
>be appreciated. 73's Ron W2CQM/3

What about a big hunk of high density polyethylene with the right sized 
hole bored in it?  You could machine a nice ring that fits over the tower 
if it's not "round" enough and to spread the loads over more of the tower 
tube's length.  Stack up a pile of cutting boards to get the thickness of 
bearing you want.

You're not spinning this thing very fast, nor continuously.

You'll need to decide how tight a fit you want, or more properly, how much 
gap you want between tower and ring o'plastic. It's a trade between turning 
friction and "rattling", but I suspect you could use a pretty loose fit.

A nice high density wood would also make a decent bearing.  Or, for that 
matter, a greased metal ring would work.

The real question is how much deformation of the garage you're attaching it 
to you're willing to accept.


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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