| It's
done! Now outside and fire up the sandblaster. Here the gnomon
is basically completed. A lot of work has taken
place.
After
the sail was secured to the 6 inch square hollow
steel sections the continuous welds described
above were completed. The two pieces of the sail
were welded together from both sides and 0.5 inch
mild steel end plates were also welded where
required.
The 1
inch by 3 inch bar stock was bent to shape and
attached along the back of the sail. The long
curved piece was done in two sections. The first
was a piece from the semi-circle to the second
tab from the top. This little job was undertaken
one evening by Clive
Schultz, Glenn
Graham, Steve
Berry and myself. We
had every big clamp available from the tool crib
and two acetylene torches. Two on the torches and
two working with about 4 to 6 clamps. For almost
5 hours the torches were heating the bar stock
and very slowly we were able to pull the bar into
the tabs along its length. That steel was red hot
and there is evidence of this in a couple of
places where it started to puddle. Fortunately
for those of us who were working the clamps, we
had high temperature insulated gauntlets which
came up to our elbows. I know I saw mine smoking
more than once. At the end there were well over a
dozen clamps holding the bar against the tabs so
that it wouldn't move away while it cooled.
Another
evening Clive Schultz, Glenn
Graham and I finished
the remainder of the bar stock. The semi-circle
was bent using heat but because the top piece was
so short and there was rather a sharp bend in it,
Clive shaped it using the hydraulic press.
To
finish the transition between the 6 inch square
hollow steel sections and the 1/2 inch sail
plate, 1/8 inch mild steel plate was used. This
plate was cut to 3.5 inch widths and 4 ft. long.
It was then rolled to a radius by making
successive passes through rollers. It took 5
passes to get each piece of steel to its final
curvature. With each pass the rollers were
tightened a bit more to increase the curve of the
steel. Ervin Hemminger and I
performed this task. What was really nice was
that Ervin came in one evening while he was on
vacation to help with this part of the job.
How
were the four 1/4 inch plates attached to each
side of the sail? Initially they were to be tack
welded along the edges in a few spots. The welder
suggested that we use plug welds and this was a
great idea. I drilled a number of 1/2 inch holes
in each of the 1/4 inch plates. The plates were
then positioned and the welds were made in the
holes. The weld material was brought up above the
surface of the 1/4 inch plate. This excess weld
material was then sanded until flush with the
plate. At that point the weld disappears as it
becomes part of the main plate. It's impossible
to tell where the welds are.
This
describes some of the major tasks performed
during the constructing the gnomon. There were
many others.
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