Re: [TowerTalk] WTB Rohn 25G tower insulator

[Jim Lux <jimlux@earthlink.net>]

On 12/15/15 12:07 PM, Chris wrote:
> Did we ever come to a conclusion as to whether or not a flat sheet (like 1" 
> thick or more) of HDPE plastic would work?  Sandwich the sheet between the concrete 
> and a flat bottomed pier pin type base.  Obviously taking care to insulate the pier 
> pin bolt.
No reason why it wouldn't work that I can think of.  Basically, you get 
a large plastic cutting board.
You'd need to work out some sort of way to insulate the bolt, though.

> Chris
> KF7P
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> On Dec 15, 2015, at 1:03 PM, Jim Lux wrote:
>
> > On 12/15/15 10:06 AM, Andre VanWyk via TowerTalk wrote:
> > > I am getting parts together for a 160m vertical, using Rohn 25G sections. I am 
> > > looking for a Rohn insulating tower section. If someone has one, please drop me 
> > > an email. I managed to locate one a while back, but sold it to friend whom I 
> > > felt needed it more that I did at the time.
> > >
> > > For my 80m Four Square, I had insulators made out of G-10 fiberglass rod, but I 
> > > feel these are not suited for such a tall structure.
> > Why wouldn't you think it's strong enough.  G-10/FR-4/Garolite is pretty strong 
> > stuff.
> > The rod probably has more compressive strength than the tubing used in the 
> > tower sections. Likewise in shear: there's a lot more cross sectional area 
> > resisting the shear force).
> > Bending might be the area where it's different, but bending loads on a guyed 
> > tower base are pretty low (and zero, with a pier pin type base.
> >
> > Rohn 25G is 1.25" diameter 16ga tubing. wall thickness is 0.065"
> > So the cross sectional area is 1.25*pi*0.065 about 0.25 square inch
> > The solid rod will have cross section on the order of a square inch.
> >
> > Figure steel yield is around 36 ksi, G10 is around 10 ksi, so the compressive 
> > strength of both is pretty similar.
> >
> > (In reality, the failure mode for the vertical tubes is probably buckling, not 
> > compression)
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> >
> > > Rohn does not manufacture this item anymore either.
> > >
> > > 73’s
> > > NJ0F
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