The results are in!
I filled my 10 ft. high 3 inch schedule 80 pipe with concrete (3 ft. is
underground, total pipe length 13 ft.).
Before filled with concrete: I would tap on the top of the pipe with my
hand and the pipe would "wiggle". And it would continue to "wiggle" back and
forth for 10 seconds or more.
After filled with concrete: I tap on the top of the pipe with my hand and
the pipe "moves" just a little and stops moving after about a second.
So this is very good for my motorized 12 ft. wire mesh satellite dish
antenna. These things point at satellites 25,000 miles up in the sky.
Needless to say, they need to be aimed extremely accurately. 1/8 inch in
aiming can make the difference in being able to lock in a satellite or not
(with some of the weaker satellites). And prior to concrete filling, I would
guess the pipe was wiggling 1/2 inch to 3/4 inch back and forth.
So having the wind blow on the dish and making it "wiggle" constantly would
not be a good thing.
As to the size of the pipe, my dish has a mounting collar for this size
I left a 10 ft. length of 1/2" rebar in the concrete in the pole. I
basically used this along with hammering the side of the pole to get the
concrete to "settle" while pouring. I would slide the rebar up and down
inside the pole. And hammer on the sides of the pole with a hammer.
Then I just left the rebar inside the pole when I was done with this. I
don't think there is any need for the rebar in the concrete??? But I would
have had no other use for it, so might as well leave it in the pole...
Anyway "wiggle" problem solved.
And I love the internet! Ask a question and get all sorts of technical
discussion. Another interesting thing for you engineering types would be a
"tuned mass damper" for my satellite pole! Info on tuned mass dampers...