Thursday, 25 September 2014

Down and down we go

Looking back at the lift. The side braces and pulley gear were added later
It is one of the wonders of the English canal system, a scheduled monument and a 'must do' for any serious canal enthusiast. But until today we hadn't been on the Anderton Boat Lift. We've passed it by, visited the exhibition centre and watched boats go up and down between the Trent & Mersey canal and the River Weaver below, yet never used it.
But now we have. And a very enthralling experience it was too. Not thrilling; the descent is too smooth and gentle for that but fascinating to be using a system that dates back to 1875 when it was a prodigious feat of engineering.
Entering the caisson at the top of the lift
The boat lift came into being to solve a problem: salt excavation was – still is – a major industry in this part of Cheshire and the salt was transported by canal boats from the mines to Anderton where it had to be loaded onto barges to take it down the River Weaver to the Mersey estuary. Snag was the Weaver was fifty feet below the canal: the salt had to be shovelled out of the canal boats and onto salt chutes running down the steep hillside to the river basin below where the river barges waited.
To solve this time consuming process Edwin Clark was commissioned to design a lift to bring boats up and down between the two waterways.
His solution was elegantly simple. Two huge caissons – water filled tanks – were each supported on a single water filled ram and the rams joined by a pipe that allowed water to pass between them so they counterbalanced each other. Slightly increasing the water level in the upper caisson would increase its weight, moving it down while the other moved correspondingly upwards.
It all worked sublimely for a time, until the cast iron rams and the pistons began to suffer serious corrosion. In 1904 the whole lot was replaced by an electric motor powered system using pulleys, cables and massive counterweights to balance the caissons. These changes created the lift as it looks today – a new top deck carrying pulleys and motors was added above the original framework and large A-frame braces installed at the sides to take the load.
The descent begins inside the maze of girders and columns
The electric lift worked usccessfully for 75 years until extensive corrosion closed it in 1983. In 1997 a £7 restoration programme began, going back to the original hydraulic power (this time using oil and with ceramic coated stainless steel rams) and the restored lift was opened in 2002.
So what's it like? Each caisson takes two narrowboats and our companion boat, with an unpronouncable name, joined us to wait as the entry gate to the caisson was raised; we motored in and the gate closed behind. It looked a long way down. We were surrounded by a maze of massive diameter riveted cast iron columns and beams, built to the if-in-doubt-make-it-bigger philosophy of pre-computer age engineering.
As we go down the Anderton tripboat rises to meet us
And carries on up towards the canal
The descent started with some gentle bouncing before the caisson settled down into a slow, almost imperceptible sinking earthwards. Just before halfway the roof of the Lift's tripboat started to appear as its caisson rose from below and continued to rise as we dropped. It looked impressive, suspended on its single central ram rather like a waiter balancing a heavy tray on one hand. (To be fair, the caisson also runs in a locating guide at each corner but it's the ram and of course us in the other one that take the load.)
While we reach the river and the caisson door opens
Soon we were down, where a C&RT man gave us a little chat about the history and technology of the lift while the water levels were balanced and the exit gates opened.
And then we were off onto the River Weaver where I swung a right and headed down river. But the Weaver is for tomorrow.

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