Friday, 26 February 2016

A gentle slide down

This morning we moored on the boat lift moorings at 11.30 where we were joined by nb Kookaburra for our descent down the Anderton Boat Lift to the River Weaver.

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When we first passed this way the boat lift was closed due to corrosion.  It was subsequently restored after a major fund raising effort.  The lift takes boats between the Trent & Mersey Canal and the River Weaver in two large caissons.  The descent is approximately 50 feet.

This part of England has a long history of salt extraction and associated industries.  The product was moved by vessel down the River Weaver and from there onto the River Mersey.  The subsequent construction of the Trent & Mersey Canal above the River Weaver offered another transport option and the opportunity to send product to Stoke on Trent and beyond.  A large interchange basin was constructed which included an inclined plane and salt chutes.  Eventually these were identified as a ‘choke point’ and the Weaver Navigation Trustees started looking for alternatives.  They attempted to get the North Staffordshire Railway Company, owners of the Trent and Mersey Canal, to ask for a contribution towards the cost of building the proposed boat lift, but this was refused.   The Trustees then decided to fund the boat lift on their own.

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The original lift consisted of two cast iron water filled caissons which were joined to the canal by a cast iron aqueduct.  The lifting method was a water hydraulic system which consisted of a 50ft ram under each caisson that was 3ft in diameter.  The caissons worked in opposing directions (one up and one down) which meant only a small steam engine was required to move the caissons.  This system worked until the beginning of the 20th century at which time it was discovered the water powered system had caused serious corrosion.  The system was then modified to work using electricity.  The structure was strengthened by the addition of ‘A’ frames on either side and a system of gears and cogs were fitted on top.  Heavy counter balance weights were also added.  The electrical system was a success and the cost of maintenance was subsequently reduced.  By the 1970’s commercial traffic had ceased and the boat lift was almost exclusively used by recreational craft.  In 1983 extensive corrosion was found and the lift was closed.  It reopened in 2002 after a £4m restoration that took 2 years.

The operating method has reverted back to hydraulic rams.  Except these are now oil powered instead of water thus minimizing the potential for corrosion.

More information here

Whilst we waited the two CRT operators arranged for two boats at the bottom of the lift to come up. The first step was to raise the two guillotine gates at the base.  The first gate seals the dry dock and the second is the entrance to the caisson. 

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Once these are raised the two boats could enter the caisson and both gates were then lowered.  Hydraulically operated chocks are withdrawn which seals both gates.  The exterior gate is sealed by the water pressure from the river and the caisson gate by the water pressure inside the caisson.

IMG_6362IMG_6368The second boat was a fibreglass CRT patrol boat. 

Once both the boats had been raised and had exited the lift NB Kookaburra led the way onto the aqueduct.  But first the lift operator had to raise the guillotine gate at the canal end.

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We followed and both boats were then on the aqueduct stopped in front of the caisson.  At this point the aqueduct and caisson guillotine gates were closed.

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Waiting on the aqueduct

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The aqueduct guillotine gate was then lowered behind us sealing the aqueduct off from the canal.  The operator then opened the interconnected aqueduct and caisson guillotine gates allowing both boats to enter the caisson.

The two gates were then lowered behind us.  There is a small gap between these two gates which is full of water.  This is drained off which allows the water pressure from the aqueduct and caisson to seal each gate.

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Looking up it is possible to see the now redundant gears and cogs of the electrical system.  The cables and counterweights have been removed.

The trip down took approximately 10 minutes and exiting the lift was the reverse of the entry.

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Oh….. the title of today’s post has nothing to do with our trip down the boat lift!  This evening I was sitting in my captains chair when the rear weld on the central swivel under the base slowly fractured tipping the seat forward slowly depositing me onto the floor.  I’ve considered having the swivel re-welded however in the interest of safety I think a new chair is required.

3 comments :

KevinTOO said...

The only reason that the weld gave way is that
Jan has been force-feeding you too many cakes... LOL

Tom and Jan said...

TOO true KevinTOO! 😁

Mike Todd said...

One of our chairs had what sounds the same failure. We managed to get it repaired by the suppliers at less cost than replacement.