Carl and TT:
The dead load of the tower section for the 40' is a minor factor in this case.
The max vertical load comes from the vertical guy force vectors not the weight
of the tower in this case.
40' of 25 is 160 lbs., 40' of 45 is 280 lbs, and 40' of 55 is 380 lbs. The max
worst case vertical load is 5800 lbs w/o the tower dead load. That makes the 55
about 7% of the vertical load. The others are even less. Choice of tower
section is not a "make or break" for the vertical load applied to the roof by
the tower system in this case.
Every installation has its own set of parameters to be considered. There is no
silver bullet that can be applied to all situations. Each will be unique in its
own way.
I wish the U of M the best of luck in upcoming contest season.
Regards
Lonberg Design Group, Ltd.
H.S. Lonberg, P.E.,S.E.
President
P.S. Chris, thanks for the kind words.
-------------- Original message --------------
From: "jeremy-ca" <km1h@jeremy.mv.com>
> How come the extra weight of 55G when 45G or even 25G would suffice for that
> small load. Ive been involved in several roof top installs at
> commercial/industrial sites and roof loading weight was always the primary
> concern.
>
> Carl
> KM1H
>
>
> ----- Original Message -----
> From: "Christopher J Galbraith"
> To: "'towertalk'"
> Sent: Friday, August 17, 2007 3:14 PM
> Subject: [TowerTalk] Our club's (W8UM) new tower and antennas
>
>
> > Gang,
> >
> > For your enjoyment, here are some action shots of our new W8UM roof-top
> > tower installation from 7/30/07. It is a 40 ft Rohn 55G tower on top of
> > the
> > 60 ft tall Electrical Engineering and Computer Science (EECS) building at
> > The University of Michigan:
> >
> > http://www.umich.edu/~umarc/projects/towerConstruction.html
> >
> > And one view from the ground on Michigan's North Campus:
> >
> > http://www.umich.edu/~umarc/photos/tower/views/tower_Beal.jpg
> >
> > The new tower and antennas have evoked some positive responses from the
> > engineering types in the vicinity ("it is huge!") and we hope it will
> > serve
> > as our most valuable visual recruiting tool (enticing students into the
> > W8UM
> > shack).
> >
> > The 4-el SteppIR at 105 ft is a DX killer on 20m (and should be on 14-30
> > MHz
> > when propagation improves) and the dipole seems to be doing well on 40m,
> > too.
> >
> > We originally were going with a MonstIR for the HF Yagi but ran into a
> > series of engineering problems. It is a long story, but our problems were
> > mostly due to having structural engineers that did not have any experience
> > with roof-top antenna installations. In the end, the 6-20m Yagi with
> > 30/40m
> > dipole was a good compromise between overall performance and
> > size/weight/cost.
> >
> > I sincerely thank everyone on the list who gave us excellent advice
> > throughout the design process. We learned a great deal in the year or so
> > of
> > putting the design together, and a lot of information came from list
> > members' valuable experience. As you'll note on the web page, Hank
> > Lonberg
> > and Matt Strelow had a lot to do with our success, too!
> >
> > Support your college amateur radio clubs!
> >
> > 73, Chris KA8WFC
> >
> > The U-M Amateur Radio Club (W8UM)
> > www.umich.edu/~umarc
> >
> > P.S. If you know any U-M alumni, please spread the word. We love to hear
> > from former W8UM (and W8PGW, W8AXZ, even 8AX!) ops.
> >
> >
> > _______________________________________________
> >
> >
> >
> > _______________________________________________
> > TowerTalk mailing list
> > TowerTalk@contesting.com
> > http://lists.contesting.com/mailman/listinfo/towertalk
> >
>
> _______________________________________________
>
>
>
> _______________________________________________
> TowerTalk mailing list
> TowerTalk@contesting.com
> http://lists.contesting.com/mailman/listinfo/towertalk
_______________________________________________
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
|
