[TowerTalk] sched 80 mast

[Gene Fuller]

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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