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Continued...
- Lifting jacks raise the tail and centre of the bridge. Slide
blocks are removed, with the nose bearings being left in contact.
- The tail and centre jacks lower the bridge on to the central
pintle bearing, and the tail jacks continue to lower the rear of the bridge. Due
to its tail-heavy nature, the bridge tilts on the pintle bearing, automatically
lifting the span off its nose bearings. The nose bearings are passive, so
require no actuation
- The bridge now rests on the pintle bearing
and two tail wheels.
The central section is rotated 90° by two rack-and-pinion drives
until it is in the fully open position, where it is held by slewing drive
brakes. The racks are mounted on the main pier, and the drive units and pinions
on the bridge superstructure.
Maximum rotational speed of the bridge is 1m/sec, with creep
speeds being used at the beginning and end of each movement. A complete opening
or closing sequence takes approximately three and a half minutes. When the
bridge is being opened and closed, hydraulic buffers mounted on the drive rack
bring the structure smoothly to rest and locate it firmly.
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