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Rideau Canal National Historic Site of Canada

Gates

Cont'd

a) Chains run down the wall and across the floor of the lock through a series of pulleys.

b) The upper beam or bar of the gate is extended over the wall of the lock. The chains are attached to the end of this swing bar and run through a series of pulleys above the lock wall.

c) A pushbar runs through the base of the 'crab' winch and is attached to the upper corner of the gate.

d) Electric pumps power hydraulicrams that pull the gates open and push them closed.

2. Gate design has evolved over the years. Look again at the pictures of gate mechanisms and try to determine which gate may have been the earliest used and which is the most modern. Give each gate mechanism a name and then compare yours with the canal names for each gate mechanism.

Answers:

a) Endless chain crab system (1832) Canal lock gates have been opened and closed using 'crab' winches and chains since the canal's opening in 1832. On the original system, the chain ran down the wall and across the floor of the lock through a series of pulleys. The chain was attached to the lock gate under the water. Unfortunately, debris in the water often caused the chains to jam. Two examples of this system remain in use, one at Kingston Mills and the other at Ottawa Locks.

b) Swing bar/crab system (1835) In 1835, a new operating system was installed at some lock gates to overcome the problem of chains jamming under water. The upper beam or bar of the gate was extended over the wall of the lock. Instead of being attached to the corner of the gate under water, the chain was attached to the end of this swing bar and ran through a series of pulleys above the lock wall. An example of this system is still in use today at the lower gates at Old Slys, Edmonds, Upper Nicholson's and Old Combined Locks.

c) Push bar/crab system (1895) Late in the nineteenth century, a new operating system was introduced that did not require as large a timber bar for the top of the lock gate. This system uses a push bar which runs through the base of the 'crab' winch and is attached to the upper corner of the gate. Chains attached to either end of the push bar are used to open and close the gate. Most canal gates are operated using this system today.

d) Hydraulic control system (1966) In an attempt to modernize the Rideau Canal, the Department of Transport rebuilt Newboro Lock in 1966. Instead of manually cranking 'crab' winches, canal staff push a button to activate electric pumps. These, in turn, power hydraulic rams that pull the gate open and push them closed. Only three locks are operated hydraulically on the Rideau Canal. These are at Newboro, Combined and Black Rapids Locks.

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