K-10000 tower crane
Hoisting Blocks are a common feature among European built tower
cranes. The typical conversion, between 2 and 4 lines, appeared in
the late fifties on a WEITZ tower crane. It allowed 3 tons in 2
lines and 6 tons in 4 lines. It was a revolution in the U.S. to be
able to change reeving in a couple of minutes, and without anybody having
to to touch the hoisting cable.
All Convertible Blocks work on variations of the same theme, the one Block is substantially heavier than the other Block.
the K-10000 tower crane the Block hanging in the Outer Trolley consists of
a Main Block and an Intermediate Block. The Main Block, which is
carried in 2 Parts, is heavier than the Intermediate Block, which is
carried in 4Parts. When the Main Block is suspended in its two
Parts, the Intermediate Block (weighing less and carried in 4 Parts) is
butt against the underside of the Trolley in an intended
two-blocking. The Main Block can be hoisted and lowered, empty or
under load, and the Intermediate Block will always remain two-blocked
under its Trolley.
When the Main Block is lowered into its Cradle, further lowering will cause the Intermediate Block to go down. It is flared at the bottom to easily engage the Main Block. When the Main and Intermediate Blocks are pinned together, we then have six lines, i.e. 132,000 lbs lifting capacity.
In the K-10000 tower crane, this theme is taken one step further.
Before the Hoist Cable is reeved in the Convertible Block, it is reeved in 6 Parts in the Inner Trolley Tackle.
The inner Block, always carried in 6 Parts, and well lighter than the Convertible Block, will remain in intentional 2-Blocking, whenever the Convertible Block is hanging in its lines.
When the Convertible Block is lowered onto its Cradle, further lowering will cause the Inner Trolley Block to go down.
Inner Block can be pinned and the Convertible Block hooked onto the Main
Truss, which has its own double-J Hook.
The two 6-Part Blocks give the Truss a net capacity of 264,000 lbs.
The counterweighting of the inner end of the Truss represents the difference between the weight of the Inner Block and that of the Convertible Block, resulting in the Truss staying near horizontal, even when raised or lowered w/o load.
the photo of the Inner Trolley clearly shows the multi-tier boggie
arrangement, giving equal wheel load distribution, regardless of the
straightness of the roller path.
long arms carrying small sheaves are automatic Trolley Locking
devices. The small sheaves rest on the Trolley Traction cable.
In case of a cable fracture, the arms will drop down and cause a locking
of the Trolley Travel.
Copyrightę 1999 Tower Cranes of America, Inc.
Page Last Updated On 09/13/1999