steel sheetpilings. Figure 12-51 shows the components
of a swinging lead.
The boom point sheaves are used to accommodate
the hoist drum wire rope that supports the pile,
pile-driving hammer, and leads; therefore, its use
requires a three-drum crane. Under certain conditions
a two-drum crane can be used The leads are raised to
the vertical by a combination of booming, swinging,
and/or traveling.
ADVANTAGES.— Some advantages of using a
swinging lead over other types of leads are as follows:
1. They are the lightest, simplest, and least
expensive.
2. With stabbing points secured in the ground,
these leads are free to rotate sufficiently to align the
pile-driving hammer with the pile without precise
alignment of the crane with the pile.
3. Because these leads are generally 15 to 20 feet
shorter than the boom, the crane can reach out farther if
the crane has sufficient capacity.
4. They can be used to drive piles in a hole, ditch,
or over the edge of an excavation.
5. For long lead and boom requirements, the
weight of the leads can be supported on the ground and
Figure 12-52.-Lead adapters connected to the boom tip.
DISADVANTAGES.— Some disadvantages of
using a swinging lead are as follows:
1. It requires a three-hoist drum crane (main line
for the pile, secondary for the pile-driving hammer, and
third for the leads) or two-hoist drum crane with the lead
hung on the sling from the boom tip.
2. Because the leads are supported by the hoist wire
rope, precise positioning of the leads with the top of the
pile is difficult and slow.
3. If stabbing points are not secured to the
the pile is lifted into place without excessively
ground, it is difficult to control the
increasing the working load weight.
leads.
twisting of the
Figure 12-51.-Swinging leads.
12-38
