[TowerTalk] Phillystran questions

Sat Dec 22 10:21:29 EST 2012

Thanks for your thoughts.

The Hy-Tower is a design from the 50's and the engineering information from 
the current producer, by no fault of their own, is unfortunately in poor 
condition, i.e. a copy of a copy of... and is virtually unusable and 
worthless.  I didn't elect to risk a $1000 + antenna installation on a whim. 
I have good personal friends who graciously consented to sanity check my 
design/modifications as well as offer hands-on assistance. Their credentials 
are quite good. Mark and John... with Mark as a ham who has a BSEE plus 
about 35 years of antenna design experience and John with a masters in 
mechanical engineering and 35 plus years of hands-on experience.  John flew 
in from California for a week and lent his experience (ANNUAL TREK NOT JUST 
AN ANTENNA PARTY).  Mark came up from Texas for 3 nights over Thanksgiving 
plus we have email and telephone.  I tend to overbuild, especially if I'm 
not quite sure. I am confident that any of my design ideas that make it past 
Mark and John have a terrific chance of success.

One of the failure modes is failure of one or more insulators at the base. 
My 4 point guys will reduce their bending moment which tries to take them 
out of column while increasing the columnar load, a compressive load well 
within their capability.  Note: I am not tensioning the guys nearly as much 
as a "standard" tower guy job.

In addition to John's hands-on practical experience, his analytical skills 
and mathematic modeling ability is of the first order. He too opts for 
conservative designs (just not always as overkill as mine.) He "did the 
math" and we are confident the antenna installation will survive appreciably 
higher wind and gust loadings than the "stock" installation.  We need higher 
wind survivability as the base of the tower section is 22 feet above ground 
level and the wind is faster there.  We are confident that the weak point of 
the design is the telescoping 80 meter "nesting" aluminum tubes which should 
"crinkle" and fold over with no collateral damage other than possibly one or 
more of the stubs (40, 15, and or 10 meters.)

I originally intended to use a 3 point guy but John suggested a 4 point guy 
which will require sufficiently reduced tension and thereby less total down 
thrust (compressive force) on the tower.

Mine is not the first or only roof mounted Hy-Tower installation but I have 
no information whatsoever about the other such installations.  Hy-gain lists 
a roof mounting kit with applicability to multiple models, including the 
Hy-tower.  I have not seen this kit but the catalog info indicates the use 
of metallic guys which I wish to avoid for obvious reasons. That and I had 
already designed, fabricated, and installed the base mount on the roof 
before finding out about the Hy-gain kit. I recall the installation well as 
it was 112F in the shade but I was in full sun with a highly reflective roof 
under me and I was wearing welding leathers. The nuts I installed on the 
through bolts securing the mount to building structure got too hot to touch 
and had to be shaded for a while to cool (close quarters, couldn't use 
gloves.)

After the antenna was up as if on cue the winds piped up and we had gusts in 
the 50's as well as lots of 30+ and all is well.  The upper sections of the 
80 meter (pig stick) sure do flex over in an arc (I was only a little 
nervous) but everything was straight when the wind died down.

I'm willing to share details of the installation if anyone is interested but 
anyone using any of that information is on their own and accepts any 
liability.  I'm not accepting liability in any form.  Your mileage may vary. 
Extra-terrestrial influences could interfere, Mayan time keeping, coriolis 
effect, phlogiston, ether drag/drift...

I bill myself as an optimistic realist who hopes for the best and deals with 
reality.

73 Patrick AF5CK

-----Original Message----- 
From: Pete Smith N4ZR
Sent: Saturday, December 22, 2012 4:31 AM
To: towertalk at contesting.com
Subject: Re: [TowerTalk] Phillystran questions

Seems to me that something to consider  is that guying the Hy-tower will
alter the load distribution on the tower - I can't do the math, but in
principle it will replace some of the overturning force with compressive
load on the legs.  It might be a good idea to inquire whether anyone has
done this successfully in a high-wind environment - you could wind up
replacing one failure mode with another.

73, Pete N4ZR
Check out the Reverse Beacon Network at
http://reversebeacon.net,
blog at reversebeacon.blogspot.com.
For spots, please go to your favorite
ARC V6 or VE7CC DX cluster node.

On 12/21/2012 7:34 PM, K8RI wrote:
> On 12/20/2012 3:31 PM, r miles wrote:
>>
>> Today I lost my HyTower. 70+ MPH gust tore it loose & broke the 3 cone
>> shaped insulators. Antenna is in very gud shape as it fell onto very
>> soft wet soil. I have the old T base & it's a bit kinked but fixable.
>> The new solid triange base has different hole spacing  so I must go with
>> what I have. I'm thinking of guying  the HT after it's repaired. Cheaper
>> than going thru this again. Can I use the lightweight 1200 Lb
>> Phillystran guys the same  way as EHS.
>
> Sure! If you aren't putting a lot of load on it.
>
> 73
>
> Roger (K8RI)
>
>
>  Nothing fancy just looped thru
>> insulators to guy posts. Can it be cable clamped? Guys I'm not guying a
>> monster tower with yagis. I just want the HT to stay up. I'm open to
>> suggestions. Can't use poly type rope here in the South. Sun does a fast
>> number on that stuff.  I need a non conductor guy that won't self
>> destruct in a year.
>>
>> K9IL
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