US Tower offers only 2" masts and a thrust bearing for a 2" mast, but
since each tower is built as the orders come in, they could no doubt
build one with holes large enough for a 3" mast -- but you might be on
your own when it comes to finding a suitable bearing.
Note that US Tower's wind-loading figures assume that the antenna is
only 1 foot above the top of the tower (at least that is the case for my
HDX-555 according to their docs.) and that their calculations use an
older version of the Universal Building Code than some municipalities
are now demanding.
73
Alan NV8A
On 02/22/07 04:24 pm Jeff Kinzli wrote:
> I'm working on getting some aluminum up here. The antennas I plan to
> use are a 4L Steppir and a 3L M2 40 (40M3L). One requirement is that
> this stack goes on a crank up, as I'd like it cranked down most of the
> time (weather, neighbors, etc.). I'm also not one for climbing, so I'd
> like to do any maintenance at the cranked-down level (or tilted).
> 70-75 or so feet is really my goal tower height, and I'm in a 70MPH
> wind rated area. I'd plan to have the tower nested or at 50' or so
> unless the winds are calm or 0mph.
>
> So, from what I can tell, there's really only two choices - US Tower
> HDX-472, and Tashjian LM470 or DX70. There doesn't seem to be any
> beefier crank ups on the market that I can see.
>
> I want positive pulldown, and I like the fact that US Tower has a
> levelable base, it doesn't appear that Tash has that. There also seems
> to be a lot more HDX's in the field. So I'm leaning towards the HDX.
>
> I'd like to do a 3" OD mast (stacking the 40 around 10 or so feet
> above the Steppir), but this represents a concern about rotational
> torques on both the tower and mast. Then again, the Steppir and 40 are
> pretty close to each other in weight and wind load, but the 40
> obviously has longer elements, which I would think would contribute to
> those rotational torques. I'd like to get the 40 as high as possible,
> hence I'd like it at the top of the mast (and why I'd like to use a 3"
> mast).
>
> I also noticed that it seems that Tash has a 2" max mast size. I'm not
> sure if the top mast hole is "borable", to make it 3" and fit a 3"
> thrust bearing there. I don't see any specs on the HDX for maximum
> mast diameter.
>
> I'm wondering if anyone has a similar set up, and/or has
> recommendations. This would be my 3rd tower but the first crank up so
> I'm a little green there. I'm also thinking I could use a suggestion
> on a rotor, the M2 rotor seems like the one.
>
> For the final work, I have an architect and engineer involved to do
> the final calculations, get the permit, etc. but I'd like to at least
> have a place for them to start with reasonable guesses about what will
> work, what won't, etc. and what I want to achieve with their help.
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