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Ancient Siege Engines
The stick may now be removed and the butt-end of the arm placed between
the halves of the skein. The skein should appear as in B, fig. 199.
If the skein is formed of hemp or flax and not of horse-hair, the material
should be previously soaked in neat's-foot oil. The oil will preserve the
skein and save it from wear and tear; it will also make the skein into
one solid mass, so that when it is twisted up by the winches its strands
receive an equal strain.
When a skein is made of fine cord, it will be necessary to wrap this
(in forty yard lengths) on a number of large netting needles, such as herring-net
makers use. It would be out of the question to pass and repass fine cord
in one length through the winches.
My largest catapult, for instance, required 1,400 yards of cord to make
its skein.
When short lengths of fine cord are used, they will have to be knotted
together as occasion requires during the process of making the skein.
After the skein is finished and the arm of the catapult has been placed
in position therein, the former may be twisted (C, fig. 199).
For this purpose a heavy spanner, 6 ft. long, is necessary.
The eye of the spanner is fitted over the squared spindle (D, fig. 193,
p. 280) of one of the winches. By means of the spanner, three or four men
turn one winch slightly. They then remove the spanner and go round to the
opposite side of the catapult and give the other winch a turn.1
Numerals may be painted on the large wheels of the winches, so that
it may be readily seen if the same number of revolutions are given to each
wheel. This is important, as if one winch is turned more than the other
the skein will be more tightly twisted on one side of the arm than it is
on the other, and a Joss of power will ensue.
The winches should be employed to twist up the skein gradually, till
it is impossible for three strong men (without the aid of the windlass)
to pull the arm back, even a quarter of an inch, from the top cross-bar
against which it presses.
Three complete revolutions of the large wheel of each winch should be
sufficient to create this amount of pressure.
1 The winches are, of course, always turned
in the same direction.
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