Side haul railway dry docks
Ship transfer machinery
Chains, rollers and maintenance
Bridles roller system
Restoration & enlargement
Vertical lifting vs. inclined ways
For transfer to a single berth, it is generally
most economical to utilize a power take-off from the main railway
dry dock hauling machine. In the case of longitudinal transfer,
this can be accomplished by mounting a gypsy on the speed reducer
for pulling with wire rope. For side transfer, the preferred way
is by a double-drum winch driven by the hauling machine motor,
with a wire rope passing through fairleads to block and tackle
for pulling sideways.
When there is an extensive transfer system, a separate, independent
winch is far more practical. IF a cross-transfer table is to be
used, this winch can be mounted as part of it so as to be able
to pull the table sideways and to effect longitudinal transfer
onto and off the cross transfer.
Wire rope is economical for transfer operations since good mechanical
advantage can be obtained by using multiple-sheave blocks. If
the cables should break, the result is not catastrophic because
the vessel is being moved in a horizontal plane.
For transfer of a very heavy ship, possibly from land to a floating
dry dock, machinery and chains of the size used for a large railway
dry dock - say 5,000 tons - can propel horizontally a ship up
to 25,000 tons, taking advantage of the low friction that is characteristic
of the free roller system used for railway dry dock cradles. Another
means that has proved economical is use of hydraulic cylinders
connected to an electric power source by long umbilical cables.
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