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@rochester.rr.com
> To: towertalk@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@telus.net>
> To: <towertalk@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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