[TowerTalk] sched 80 mast

[RICHARD SOLOMON]

I think that was W1FZJ and he said ..."if your antenna lasts through
the winter, it wasn't big enough"... .

73, Dick, W1KSZ

> From: w2lu at rochester.rr.com
> To: towertalk at contesting.com
> Date: Wed, 27 Jan 2010 10:44:46 -0500
> Subject: Re: [TowerTalk] sched 80 mast
> 
> How about repetitive gusts and possible resonance?  But remember the Sam 
> Harris / W1FZ philosophy - "If it stays up more than two winters it was over 
> designed".
> ----- Original Message ----- 
> From: "Jim Thomson" <Jim.thom at telus.net>
> To: <towertalk at contesting.com>
> Sent: Wednesday, January 27, 2010 10:09 AM
> Subject: [TowerTalk] sched 80 mast
> 
> 
> > VE9HF  indicates his  sched  80 mast is  .25" thick.     It's not.
> >
> > IF his mast is  typ 1.9" OD  sched 80  stuff... it's only  .200" thick. 
> > His section modulus is only .412
> >
> > If the yield strength is  35 ksi.... his max  bending moment is  only 
> > .412 x 35 ksi = 14,420  in lbs...[ 1200 ft lbs]
> >
> > Lets say  7  sq feet @ 70 mph [20 lbs  per sq ft]   x  14'   .... =  1960 
> > ft lbs  of  bending moment.
> >
> > 1960> 1200  !     The mast will snap like a tooth pick.   The mast is 
> > maxed out  with 1200/140 =  8.57'
> >
> > This doesn't even factor in the  other TWO  proposed yagi's... nor the 
> > wind load of the mast itself !
> >
> > It's NOT....." a serious  tower" .          It's made for TV ants'... and 
> > can be used with ham ant's,
> >
> > provided you don't overload it...esp with tall masts.   Even if you guyed 
> > the tower,  the proposed  mast you
> >
> > are contemplating will fold over at a right angle.      That  Delhi  isn't 
> > CSA  approved, nor does it meet
> >
> > the Canadian  S-37 tower specs.   Load it up with heavy wet snow + a tiny 
> > bit of ice  .....+  a 55 mph gust
> >
> > .. and it's  bye-bye tower... plus 3 x ants'  trashed.  Removing a bent 
> > mast is a gong show in itself.. and
> >
> > extremely dangerous.   If you want a   stronger, self support tower,  get 
> > a Trylon Titan..[with the 48" wide bottom section]...
> >
> > ... or better yet ..a  Trylon  Super Titan. The Trylon super Titan IS  a 
> > S-37  rated tower, and will handle  25 mm of radial ice  + high wind.
> >
> > It's the real deal.   The stock Delhi top bearing plate + mating thrust 
> > bearing is pure junk.   The rotor plate is worse.   You will end up
> >
> > tearing up all the plates within months.
> >
> > Later.......... Jim  VE7RF
> >
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> >
> >
> >
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