Manitowoc 21000 Mast Block Fixture
This Manitowoc 21000 mast-top fixture has two
purposes.
Both utilize the multiple sheaves:
1. Raise major
crane components such as the boom. This is done
mostly in tandem with
an auxiliary crane, usually a Manitowoc 999.
2. Control the boom angle with maximum leverage:
The top of the mast is
approximately 140 Ft above the boom fulcrum.
The component behind this assembly, seen on the right, is the top end
of the boom where the main lift block is attached.
The way this mast-top fixture is finally rigged appears in the "ready picture"