Engineering Wonders of the World
Volume I
Forfatter: Archibald Williams
År: 1945
Serie: Engineering Wonders of the World
Forlag: Thomas Nelson and Sons
Sted: London, Edinburgh, Dublin and New York
Sider: 456
UDK: 600 eng - gl.
Volume I with 520 Illustrations, Maps and Diagrams
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332
ENGINEERING WONDERS OF THE WORLD.
DIAGRAM TO SHOW HOW THE CANTILEVER ARMS WERE
BUILT OUT.
performed in as many strokes with the rams,
th© ends of the platform being raised alter-
Lifting
a
Platform.
nately. After each stroke the
beams immediately support-
ing the cross girders were
pinned in position, and the
press girders released and raised by admitting
water above the pistons. Then they were
pinned in turn and the others released. This
operation had to be repeated sixteen times
during a lift.
Encircling the columns, below the platform,
to which they were attached, were the cylin-
drical riveting cages, covered in with wire
netting to prevent the fall of men, tools, or
rivets, etc. At each cage one gang worked
outside the tube, another inside. Similar
cages were used on the tower struts and the
lower booms of the cantilevers.
As the columns were free at the top during
construction, their own incli-
Correcting nation from the vertical, the
, *he . weight of the platforms, and
Inclination , . ,
of the wind pressure caused seri-
Columns. ous deflections, which had to
be corrected from time to time
by means of wire ropes for pulling inwards
and timber struts and hydraulic presses for
thrusting apart. Such correction was a
delicate operation requiring the greatest
care, and, as the columns were terribly
stiff, the use of enormous power.
Half-way up a halt was made to
build in the crossings of the diagonal
struts in the centre of the tower. A
crossing contains, in the
case of Inchgarvie, 80 The
tons of steel on each
Elevation
side of the tower. reached
When they and the
horizontal bracings were finished, the
platforms resumed their upward jour-
ney to the top—reached at a height of
360 feet above high water, practically
identical with that of St. Paul’s Cathe-
draL They there almost touched one another,
having drawn closer and closer as they rose.
The gap was covered over so as to form one
large platform of more than double width,
and the longitudinal girders were stiffened
with heavy chains to prepare for the con-
struction of the lattice-work horizontal ties
connecting the column summits. These ties
were soon put together and joined to the top
skewbacks, from which, as from their larger
brethren beneath, members run in many
BUILDING OUT A LOWER BOOM. RIVETING CAGE
STARTING ON ITS JOURNEY.