The shaft is situated at the head of the ways, and sets in
motion four double-gear windlasses of the type shown in Fig. 2. The
ratio of the wheels is as 9 to 1. The speed at which the ships move
forward is from 10 to 13 feet per minute. Traction is effected
continuously and without shock. After the cables have been passed around
the hull, and fastened, they are attached to four pairs of blocks each
comprising three pulleys. The lower one of these is carried by rollers
that run over a special track laid for this purpose on the inclined
plane.
[Illustration: FIG. 1.--WAYS OF LAUNCHING VESSELS SIDEWISE.]
The three successive positions that a boat takes are shown in Fig. 1.
In the first it has just passed on to the frame, and is waiting to be
hauled up on the ways; in the second it is being hauled up; and in the
third the frame has been removed and the boat is shoved up on framework,
so that it can be examined and receive whatever repairs may be
necessary. This arrangement, which is from plans by Mr. Murray Jackson,
suffices to launch 16 or 18 new boats annually, and for the repair
of sixty steamers and lighters. These latter are usually 180 feet in
length, 24 feet in width, and 8 feet in depth, and their displacement,
when empty, is 120 tons.
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