1. It requires only a two-hoist drum crane.
2. It provides accuracy in locating leads in all batter
positions.
3. It provides rigid control of the leads during
positioning operation.
4. It allows batter angles to be set and accurately
maintained.
5. It allows for the use of short boom angles that
increases the crane capacity.
6. The boom can be lowered and leads folded under
for short hauls over the road when a crane with adequate
capacity is used This operation depends on the length
of the lead and boom and the configuration of the crane.
DISADVANTAGES.— Some disadvantages of
using an extended four-way lead are as follows:
1. It is the heaviest and most expensive of the three
basic lead types.
2. It is more troublesome to assemble.
Spud Leads
A spud lead is a steel wide flange or H-beam used
in place of pile-driving hammer leads. The pile-driving
hammer rides on the flange of the beam through spud
clips bolted to one side of the pile-driving hammer (fig.
12-58).
Depending on the design of the spud lead, the spud
can be used as a swinging and underhung lead or
equipped with a sheave head assembly as an extended
four-way lead An advantage of this type of lead is that
it bears the whole bottom of the pile cap to the piling
especially when sheetpiling is being driven (fig. 12-59).
PILE-DRIVING HAMMERS
The three principal types of pile-driving hammers
are the drop hammer, the steam, or pneumatic,
hammer, and the diesel hammer.
A drop hammer is a block of metal hoisted to a
specific height and then dropped on a cap paced on the
butt or head of the pile. Drop hammers weigh from
1,200 to 3,000 pounds.
WARNING
The noise generated by a pile driving
operation can cause hearing loss. Hearing
protection must be worn by personnel in the
vicinity of pile driving operations.
Figure 12-58.-Spud clips mounted to one side of the pile-
driving hammer.
Figure 12-59.-Sheet pile driving with spud leads.
12-41
