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Canal locks, canal lifts, canal inclined planes
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Types of canal locks,
paired locks, staircase locks, narrow locks, broad locks, barge
locks, stop locks, boat lifts.
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 Narrow
and Broad Locks.
Locks are an essential feature of any canal
which needs to gain or lose height. A few canals have no locks,
such as the Gloucester and Sharpness Canal although it does have
locks at either end. Locks were built to two main sets of
dimensions, known as narrow locks and broad locks, though there
are many locks with larger dimensions, especially on the river
navigations. Narrow locks take one narrowboat which was up to 72
feet long and 7 foot beam. as you can see in the photo on the
right the fit is quite a tight one! (Photo Tony Lewery) Broad
locks may be designed to fit two narrowboats side by side as at
Hatton on the Grand Union Canal on the left, or may be designed
for barges of about 65 foot long and 14 foot beam, as on the
Leeds & Liverpool Canal. Most locks are between 6 and 10 feet
deep but Tardebigge Top Lock on the Worcester and Birmingham
falls 14 feet. |
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Staircase
locks and Flights of Locks
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| Early canals placed locks wherever there was
a contour change in the landscape, so that the canal channel
could be built as easily as possible, and the spacing between
locks varied greatly. It was cheaper to build staircase locks
which shared gates, such as the the Watford Locks on the Grand
Union Leicester Line on the left, if there was a sudden change
in contours which needed a few locks very close together.
When canal engineering developed to construct
cuttings and embankments it became possible to decide where to
put locks. It was more convenient for construction and for
operation to put a number of locks together, a flight, which
could have up to 30 locks. Audlem on the Shropshire Union Canal
on the right is a flight of 15. |
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Duplicate
Locks and Stop Locks.
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| As canals became busier many locks created
bottlenecks. More profitable canals, such as the Trent and
Mersey Canal at Church Lawton on the left, built duplicate locks
alongside the existing ones. When boats were worked in pairs
they could be worked side by side through the locks. (Photo Tony
Lewery) Stop locks were built where
canals joined to keep the water belonging to the two canal
companies separate, Water was a valuable commodity! They had a
very small fall, as right at Dutton on the Trent and Mersey
Canal near it's junction with the Bridgewater Canal. |
Canal
Lifts and Canal Inclined Planes
Many alternatives to locks were tried
out by the canal engineers, eager to reduce the loss of
water during lock operation, (about 50000 gallons for a
narrow lock) and to save the costs of lock construction.
Inclined planes usually had rails on which tanks
containing a boat could be pulled up from one canal
level to another. There was one at Foxton on the Grand
Union Canal.
Canal lifts, like the one at Anderton
on the Trent and Mersey Canal on the right, lifted boats
vertically, usually in a water filled tank. Anderton has
two tanks which can each take two narrowboats and lift
50 feet from the River Weaver to the canal. Originally
the two tanks counterbalanced each other and were
hydraulically powered. Electric motors were installed
early in the last century and weights and pulleys were
added to enable the tanks to operate independently.
It was closed in the eighties due to
corrosion but has been fully restored and reopened in
2002, reverting again to hydraulic power. |
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