Conversion To Electrical Operation
By 1904 the Trustees faced the imminent prospect of a having to close the boat lift for a very considerable period in order to replace the hydraulic rams. They asked their chief Engineer at the time, Colonel J.A. Saner, to investigate alternative solutions. Saner proposed an innovative solution in which the hydraulic rams would be replaced by electric motors and a system of counterweights and overhead pulleys, allowing the two caissons to operate independently of each other. Although this system involved many more moving parts than the hydraulic system, these would all be above ground and easily accessible, so it offered easier and cheaper maintenance and a longer working life.
As the entire weight of the caissons and counterweights would now be borne by the superstructure of the lift, this would have to be greatly strengthened, and put on much stronger foundations. However, by building a separate stronger superstructure around the original lift frame, Saner promised to achieve the conversion with only three short periods of closure to traffic.
The new superstructure consisted of ten steel A-frames, five on each side of the lift, which supported a machinery deck 60 ft (18 m) above the river level. The electric motors, drive shafts and cast-iron headgear pulleys were mounted on the machinery deck. Wire ropes attached to each side of each caisson passed over the pulleys to 36 cast iron counterweights, 18 on each side. Each counterweight weighed 14 tons, so that 18 counterweights would exactly balance the 252 ton weight of a loaded caisson. The electric motor was required to overcome friction between the pulleys and their bearings. A 30 horsepower (22 kW) motor was installed, but normal operation only required about half of this power.
In addition to new foundations and superstructure, the conversion also involved converting the wet dock at river level into a dry dock and strengthening the aqueduct between the lift and the canal. The original caissons were retained, but modified to take the wire ropes that now supported them on each side.
The conversion work was carried out between 1906 and 1908. As Saner had promised, the lift was only closed for three periods during these two years, for a total of 49 days. The converted lift was formally opened on 29 July 1908 (although one caisson had in fact been carrying traffic on electrical power since May 1908 while the second caisson was being converted).
Read more about this topic: Anderton Boat Lift
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