[TowerTalk] Question on mast height above tower

Chuck Hartley chuck.hartley at gmail.com
Wed Aug 21 11:31:07 EDT 2013


I have the same tower and I would definitely not trust the top of it to
withstand that much loading.  The mast is probably ok, but I don't believe
the rivets in the top section would last long with that much of a lever arm
sticking out of the top.


On Wed, Aug 21, 2013 at 10:51 AM, <RShirbroun at newportlabs.com> wrote:

> I didn't get any comments or suggestions to my previous post, so I'll try
> again.
> If this is a dumb question, feel free to tell me!
>
> I have just erected a new HDBX 40 in place of my 30 year old HBX 48,
> sacrificing 8' of height to gain some strength and load capacity (and
> peace of
> mind!).  The stock rotator plate allows 2' of mast below the top plate and
> I
> will be using the heavy duty Yaesu thrust bearing (along with the Yaesu
> heavy
> duty 2800 rotator plus the absorber plate).   I have added steel angle
> braces
> to reinforce the rotator plate.
>
> I'm looking at using a 15' chrome/steel 2" mast (in place of my previous 9'
> mast), so 13' of the mast would extend above the tower.  The mast would
> support
> a TX38 tribander just above the top plate, a 6 m beam half-way up, and a
> 40m
> rotatable dipole near the top, 12' above the top tower plate and the thrust
> bearing.  The mast, of course, is very heavy, weighing around 75lbs.  The
> tribander weighs 40lbs and with 5 ft2 surface area; the 6 m. beam weighs
> 10lbs
> with 1.5 ft2; the dipole weighs 10lbs and is 0.5 ft2.
>
> Is this too much mast for this tower?   (BTW - I'm aware the boom length
> exceeds the 10' maximum for this tower, but the HBX 48 handled a similar
> tribander for 30 years, with occasional severe ice-loading, without any
> problems.)
>
> Thanks and 73,
> Randy, ND0C
>
>
>
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