Hello- I am looking at around 200' of much older tower, from commercial
service that has orange/white paint scheme on it. It appears identical to Rohn
65G in construction -- the leg size, zig zag brace size and pattern, and flange
square dimensions. However, looking closer, these differences appear when
comparing this older tower flanges with a marked 65G specimen:
1. The flanges on older tower are 1/2" thick (Rohn 65G is 5/8" thick)
2. The flanges on older tower are oriented differently -- they appear to be
rotated 45 degrees as compared to Rohn 65G specimen. 3. I cannot find any
part number stampings on this tower -- the Rohn 65G has part number stampings.
4. The flanges on this older tower are drilled in center to allow drainage.
The hole size is around 5/8" on some sections and around 1" on other sections
5. The weld around tower leg on flange top on this older tower is not as
"heavy" as the weld on Rohn 65G specimen.
Here are my concerns - I wish to use some 65G tower as a self supporter
adjacent to my shop, in vicinity of 70 to 80 feet high with light antenna load.
I plan to install it according to Rohn's drawings for this application, per the
highest wind load specs/strongest installation. This would be a substantial
base and lots of concrete/rebar. But I want to know I have the strength of 65G.
I am trying to find out the particulars of this tower. Some knowledgeable folks
have stated that it is Rohn, just an earlier version of 65G that was redesigned
at some point and thus the flanges rotated on newer design to prevent mixing.
The one thing that concerns me is the welding of the legs to the flanges.
It is said that Rohn welds the legs to the flanges both inside and outside. I
noticed on Rohn 65G that the hole on flange is much larger. Does Rohn actually
punch out a hole in the 5/8" thick flange plate and slide it over the leg, thus
allowing this double-welding? This point here is the main thing in my mind in
comparing the strength of the two different towers -- the older tower has
thinner flanges and the flanges obviously are welded to legs only on the
topside of flange due to small drilled holes as mentioned earlier.
Can anyone fill me in on this please.Byron W5FH
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