3.1.2 Crane-supported leaders
Although the hydraulic piling rig with its base frame and leaders supported by a stayed mast
provides a reliable means of ensuring stability and control of the alignment of the pile, there
are many conditions which favour the use of leaders suspended from a standard crawler
crane. Rigs of this type have largely supplanted the frame-mounted leaders for driving long
piles on land in the UK and the USA.
Fixed leadersare rigidly attached to the top of the crane jib by a swivel and to the lower
part of the crane carriage by a ‘spotter’or stay. Hydraulic spotters can extend and retract to
control verticality and provide fore and aft raking; they can also move the leader from side
to side. The ICE heavy-duty spotter provides 6 m of hydraulic movement fore and aft and74 Piling equipment and methods
Figure 3.1ABI Mobilram with telescopic leader fully extended driving tubular pile (courtesy
ABI GmbH).