A VERY strange bridge has been erected over the Lea in London.
Cody Dock Bridge is a hand-winded, rolling bridge that spans the dock mouth, providing a crossing for pedestrians and a passage for boats, Roger Fox reports.
Rolled along steel track
The bridge is counter-weighted, and allowing the 13 tons bridge to be rolled along a steel track, yet is so balanced that it is hand-cranked.
Clearly not part of the main navigation on the lower section of the Lea but the operation of the bridge allows boats passage into the dock.
Most of the structure is steel with oak bearing strips fixed to the hoops that roll on the undulating Corten steel track, whilst teeth interlock with steel pins providing movement.
Set into existing walls
The footbridge has a monocoque steel deck, spanning 7m over the dock mouth. Two 5.5m rounded portals at each end allow it to roll along the undulating concrete abutments which are set into the existing masonry walls.
The bridge remains horizontal when in motion so that its weight is never lifted vertically. The bridge is driven by cable, with a pair of manually operated winches on one bank.
Clearly this bridge over the Lea is a really clever one. Work this out if you can? Asks Roger!