The piston is a free piston that provides the impact energy delivered to the pile. The impact block is
located at the bottom of the lower cylinder and relays the energy from the piston to the pile via the
direct drive assembly. Piston compression rings and impact block compression rings are installed to
assist in compression and to prevent exhaust gases from entering the upper cylinder and escaping
from the bottom of the lower cylinder.
The upper and lower cylinders are porous-chrome-lined and bolted together to form one cylinder that
enclose the piston and impact block. An o-ring, installed between the upper and lower cylinders,
provides an air-tight seal.
The upper cylinder contains the catch ring cap, fuel tank, and hammer trip system. Lifting lugs are
located on the front of the upper cylinder. A red-colored piston transportation pin, normally housed in
the tool box, can be installed in the top part of the upper cylinder to secure the piston for
shipping/transportation purposes. A red-colored weather cap with securing strap, normally housed in
the tool box, can be installed on the catch ring cap of the upper cylinder to keep out moisture and
The lower cylinder contains the four upper and lower gibs, intake/exhaust port, cooling fins, fuel
injection system, fuel system guard, oil lubrication system, and lubricating oil tank. The lower cylinder
also contains the internal combustion chamber that is created by the ring-shaped area on the nose of
the piston and the cylinder walls. A cushion housing guide ring and cushion housing guide ring support
are located in the bottom of the lower cylinder. A red-colored weather cap, normally housed in the tool
box, can be installed on the intake/exhaust port to keep out moisture and foreign objects.
The hammer trip system consists of the hammer trip assembly, hammer trip track rails, trip disengage
lug, trip safety lever and trip engage lug, trip safety lever cord, and trip transport bolt. The hammer trip
assembly, sliding along the hammer trip track rails and hoisted up and down by the hammer line (main
hoist) of the crane, contains a trip mechanism that is used to start the impact hammer by raising and
automatically releasing the piston at a predetermined height. The trip mechanism of the hammer trip
assembly consists of a lifting pawl, lever and shaft, connecting links, stop pin, and cam mounted in a
housing and backplate. The trip engage lug, located on the trip safety lever in the lower portion of the
upper cylinder, engages the trip mechanism in the hammer trip assembly when it is lowered to allow
lifting of the piston. The trip disengage lug, located at the top of a slot in the upper cylinder and part of
the upper cylinder, activates the trip mechanism and causes the piston to be released when the
hammer trip assembly is raised to the predetermined height. The red-colored trip transport bolt,
normally housed in the tool box, can be installed in the hammer trip assembly to secure the hammer
trip assembly to the hammer trip track rails for shipping/transportation purposes.
The trip safety lever is used by ground personnel to engage the trip engage lug to allow the hammer
line (main hoist) to raise the hammer trip assembly (and piston) in order to start the impact hammer.
The trip safety lever cord, attached to the trip safety lever, is used to control the position of the trip
safety lever. When in the normal position (trip safety lever cord not pulled), the trip safety lever locks
out the hammer trip assembly allowing the hammer line (main hoist) to raise and lower the entire
The direct drive system transfers the driving energy developed by the piston and impact block in the
lower cylinder to the pile being driven. This is provided by the direct drive assembly connected to the
bottom of the lower cylinder that houses a recoil dampening system and striker plate (driving head).
The direct drive assembly consists of the upper and lower drive housings and is capable of driving up to
18-inch (45.7 cm) piles. Lifting lugs and adapter holes (used to secure the square (concrete) and sheet
pile adapters) are provided at the top of the direct drive assembly. A blow count recorder and waste
fuel drip tank are also installed at the top of the direct drive assembly.