At 08:20 AM 8/29/2005, email@example.com 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: 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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