It centres around two massive 38 tonne, 17m long cylinders or rams, securely bolted and welded to the base of the boat-carrying caissons, which remarkably were forged by the same Rexroth plant that made the original steel frame at the beginning of the last century.

The sophisticated hydraulics system was developed on an international project basis, involving Rexroth technicians from Britain, The Netherlands and Germany. The company was given complete design and build responsibility by British Waterways. Computer modelling techniques were employed at the group's headquarters to evaluate the effects of different weather and load conditions on the lifting mechanism and the potential bending forces acting on the caisson-supporting cylinders.

As a result, the system is equipped with duplicate pumpsets to ensure the lift operates normally in the event of unit failure and provide the additional pressure when only one caisson is raised.

The ceramic coated cylinders are each sized to withstand the forces imposed and incorporate the latest integrated measuring system for monitoring the ram stroke throughout its travel.

Finally, a programmable controller affords menu driven control of the balanced and single mode lifting operations, smoothly accelerating the rams to maximum speed in ten seconds and decelerating down to creep mode when approaching the stop position, all within the required five minute lift/lower cycle. The final result is a 21st century drive and control technology married discreetly with Victorian iron and Edwardian steel.

MJ Information No: 17016