Canal Locks and Canal Lifts; canals climbing hills
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.
Staircase locks and Flights of Locks
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.
Duplicate Locks and Stop Locks.
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 1980's due to corrosion but has been fully restored and reopened in 2002, reverting again to hydraulic power.