[TowerTalk] Putting together a tower package...

Bud Semon N7CW n7cw at cableone.net
Fri Feb 23 10:56:04 EST 2007


US Tower does have a 3" thrust bearing and will build them into the tower
for you - I just did that.

They advertise their HDX572 as the heavy duty tower, but they do make a HDX6
series, which is even heavier duty.  For example, I bought the HDX689 - it
is not on their website (at least I couldn't find it with a quick search)
but places like HRO (I recommend dealing with Tom, KM6K in San Diego) or
Texas Towers can give you the real information.  Or call Gary Smith at US
Tower - he was very helpful.  A warning - the price difference from the HDX5
to the HDX6 is painful.  But when the wind blows, I'm really happy that I
spent the money.

You can perform the tower/mast calculations using an Excel spreadsheet
written by W9JCC and described in QEX.  Here's the link to the article

http://www.arrl.org/qex/1123.pdf  and the spreadsheet is also on the ARRL
site (referenced in the article).  You can use this to figure out what size
mast you need.

73, Bud  N7CW

-----Original Message-----
From: towertalk-bounces at contesting.com
[mailto:towertalk-bounces at contesting.com] On Behalf Of Alan NV8A
Sent: Friday, February 23, 2007 8:27 AM
To: towertalk at contesting.com
Cc: Jeff Kinzli
Subject: Re: [TowerTalk] Putting together a tower package...

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.


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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