58
DOCK ENGINEERING.
Staples are set at short intervals, so that the amount of fall can be regulated
fairly uniformly.
The services of three men are required for each machine—one to work
the winch, another to actuate the lever, and a third to watch the pile, mark
its progress, and shift the staple. Steam should be partially cut off while
the ram is falling, in order to reduce the speed of the chain for re-attachment.
The pile is pitched by an
auxiliary chain passing over
a separate pulley at the
frame head. It is kept in
position by a toggle bolt
passing right through the pile
near the top, and also through
a wood block in the groove
behind it, to the back of the
leaders, where it is secured
by an iron bearing plate,
nut, and screw. After the
necessary preliminaries the
monkey, which has been
temporarily raised out of the
way, is lowered upon the
pile and is ready for action.
The rate of working is about
six blows per minute under
steam pressure of 55 to 60
Ibs. per square inch. Piles
can be driven vertically, or
at any required inclination,
by adjusting a screw at the
foot of the ladder at the rear
of the platform.
When the pile has been
driven below the level of the
foot of the leaders, the pro-
cess is continued, either by
Fig. 23. —Pile-driving Machine titted with J
Telescopic Leaders. the interposition of a punch
or dolly (a short log of the
same scantling as the pile) between the pile and the ram, or by the use of
telescopic leaders (fig. 23). The first method involves considerable loss of
driving power, as the dolly absorba fully one-half of the kinetic energy of
the blow.
The frame of a Whitaker steam-hammer pile driver is not dissimilar from
that just described. The principal difference of the contrivance lies in the
application of the power. Driving is done by means of a piston and cylinder,