tower base weighs over 100 pounds and is large enough to be awkward to
handle, so it seemed best to assemble it in the hole. That turned
out to be pretty easy, as did adjusting it for 48 inches (+/- 1/16 inch
per the drawings) span across each face at the top.
made these "shoes" for the tower base ahead of time out of 8 inch CMU
blocks. The steel angle stock pieces are embedded about 5 inches
into the fast-setting pre-mix concrete.
I used C-clamps to
temporarily hold the tower base in place while I adjusted it for plumb,
and then later drilled a hole and inserted a bolt.
After everything was where I wanted it to be, I cut a fence stake into
pieces and drove each one into the vacant cavity of the CMU block.
Then I filled them with more concrete to hold the base firmly in
position. They don't move at all.