Commissioner: Port & Docks Board
Designer: William Scherzer, Chicago
Contractor: Spencer & Co, Melksham, Wiltshire; Sir William Arrol & Co.
Completed: 1912; 1932
(Photo: Stuart Carroll)
One hundred years ago, if you mistimed yourself and arrived in your motorcar on the North Wall Quay just as the double-track drawbridge of Spencer Dock was opening, you might as well have pulled out your hip-flask and settled in for the night. The process of opening the Turner & Gibson draw-bridge involved a mesmerizing but rather protracted series of events –decks on rollers slowly creak horizontally as muscley men heaved upon the mighty winches. It took a whopping 22 minutes from start to finish and that was just to let a single vessel pass into or out of the Dock, the entrance to the Royal Canal. Sir John Purser Griffith, Chief Engineer to the Dublin Port and Docks Board, decided this wait was unacceptable. In 1912, a new system was installed – the twinned Scherzer Rolling Lift Bridges, an innovative design patented by Chicago engineer William Scherzer in 1893. The revolutionary bridge had first been successfully opened over Chicago River at Van Buren Street, Chicago, in1895.
Two steel girders are rigidly connected to large steel rollers, curved like rocking chair rockers and weighted in the rear to counterbalance the span. To open, the bridges simply roll back on their rockers until upright like a jack-knife. The floors of the Dublin bridges were composed of ‘buckled plates’, an invention of Irish engineer Robert Mallet, riveted to the floor beams and to joists fitted between the beams. Each bridge was worked by electric motors, since removed, or manually in the case of a power failure. The suspension time for traffic was dramatically cut from 22 to 4 ½ minutes for a single vessel. These bascule bridges were such a success that, in 1932, another pair were installed by Sir William Arrol & Co of Glasgow at the entrance to the Custom House Docks from the Liffey.
These elaborate Scherzer Bridges are now landmark features along at the south and north end of Spencer Dock, and at the entrance to George’s Dock. The bridge by Sheriff Street, which operates as a lock gate between Spencer Dock and the Royal Canal, is notable for its rugged and rusty industrial complexion at time of writing.