A flash lock consisted essentially of a small opening in the dam, which could be quickly opened and closed. Even though the drop from the newer to the older canal might only be a few inches, the difference in levels still required a lock – called a stop lock, because it was to stop water flowing continuously between the newer canal and the older, lower one. The need for a flight may be determined purely by the lie of the land, but it is possible to group locks purposely into flights by using cuttings or embankments to "postpone" the height change. The development of the more sophisiticated pound lock is traditionally credited to an engineer, Chiao Wei-yo, working on the great Chinese canal system in the 10th century AD. First canal lock. The formula for Accordingly, they were not used where the obstacle to be passed was a mill weir. Invention The Legacy Bibliography "Canals 1750 to 1900." In about 1817 the Regents Canal Company built one of these locks at the site of the present-day Camden Lock, north London. Ancient people discovered that rivers could be made to carry larger boats by making dams to raise the water level. / [34], Pound locks were first used in medieval China during the Song Dynasty (960–1279 AD). For example, the Hindenburg-lock (in Hannover, Germany, built 1919–1928) has two lock chambers of 225 m length, each of which would use 42,000 m3 of water for a full locking cycle. Some locks are operated (or at least supervised) by professional or volunteer lock keepers. N.p., n.d. Installing a single side pond will save 1/3 of the water, whereas three side ponds will save 60% of the water: the first 1/5 of the water goes into the top pond, the 2nd 1/5 into the middle pond, the 3rd 1/5 into the bottom pond – and 2/5 is wasted at each passage (assuming the area of each pond equals the area of the lock). allow navigation above mid-tide, but just prevent the canal emptying at low tide) then it is only necessary to have one set of bi-directional gates. Not to mention the pioneering engineers and hard-working navvies, without whom the canals would never have existed. Powered locks are usually still filled by gravity, though some very large locks use pumps to speed things up. There can also be water savings: the locks may be of different sizes, so that a small boat does not need to empty a large lock; or each lock may be able to act as a side pond (water-saving basin) for the other. Web. Amsterdam was created with canals of concentric circles facing the IJ Bay in the seventeenth century. These terms can also (in different places or to different people) mean either a two-chamber staircase (e.g. One type of these, the Dunton Double, has only a single eye, but by clever tapering it will operate either size of spindle. The paddle itself is a sliding wooden (or nowadays plastic) panel which when "lifted" (slid up) out of the way allows water to either enter the chamber from the upper pound or flow out to the lower pound. Steel gates and/or balance beams are frequently used nowadays, although all-wooden versions are still fitted where appropriate. A set of locks is only a staircase if successive lock chambers share a gate (i.e. , is: water used with side ponds This early lock design was most often used on river navigations in the early 18th century before the advent of canals in Britain. When the oncoming water hit them it forced the two miters into each other which resulted in an even tighter seal between them. Lock emptied for maintenance – centre pair of gates. Where there is a steep rise in the land a marine railway may be more effective than multiple locks, such as on the Elbląg Canal. The chamber is said to be "full" when the water level is the same as in the upper pound; and "empty" when the level is the same as in the lower pound. Flood locks which have been used only as flood gates (see below) are often incapable of reverting to their former purpose without refurbishment. As with a flight, it is possible on a broad canal for more than one boat to be in a staircase at the same time, but managing this without waste of water requires expertise. Some low-head locks use sliding steel gates (see, Guillotine gates. The water was then allowed to rise until it reached the level of water up ahead. ; the lower gate's height equals the upper gate plus the lock's rise. Lock staircases are used in an attempt to reduce the total volume of water required in relation to the amount of useful work done. As engineers became more ambitious in the types of country they felt they could overcome, locks became essential to effect the necessary changes in water level without detours that would be completely uneconomic both in building costs and journey time. To economise, especially where good stone would be prohibitively expensive or difficult to obtain, composite locks were made, i.e. Three canals were designed with residential development in mind. The lock is 500 m (1,600 ft) long, and 68 m (223 ft) wide and drops 17.8 m (58 ft), and has four sliding lock gates. On most English narrow canals, the upper end of the chamber is closed by a single gate the full width of the lock. Here the motivation was, again, water supply problems. [12] When closed, a pair meet at an angle like a chevron pointing upstream and only a very small difference in water-level is necessary to squeeze the closed gates securely together. Where a very steep gradient has to be climbed, a lock staircase is used. The boatmen and women, the children who led the boat horse and grew up on board. 1 These waterways were interconnected by radiating canals, forming a fan shape. Examples: An inlet lock is to regulate water from a feeder canal or a river into the main canal. Hiram M. Chittenden Locks: tug and barge in lock when full. Lock emptied for maintenance – low water end of the lock. In the 1790’s so-called “canal mania” took place when people invested their money into practically every canal project. Materials: Early windlasses were individually hand forged from a single piece of wrought iron by a blacksmith. Such expertise permits miracles of boat balletics: boats travelling in opposite directions can pass each other halfway up the staircase by moving sideways around each other; or at peak times, one can have all the chambers full simultaneously with boats travelling in the same direction. To lower a paddle the pawl must be disengaged and the paddle wound down with the windlass. This gate type was primarily used to purposely flood certain regions, for instance in the case of the Hollandic Water Line. That boat was already leaking; the crew, having partially pumped the water out, entered Lock 74, moving in front of another boat. [42][43], Looking superficially similar to the caisson lock is the shaft lock. [30], While the concept has been suggested in a number of cases, the only example in the world of a drop lock that has actually been constructed is at Dalmuir on the Forth and Clyde Canal in Scotland. Consequently, this type of lock needs more water to operate than vertical-sided brick- or stone-walled locks. My dog, the crazy man, was bred to guard the barges on the canals of the Low Countries in the Middle Ages. The Low Countries and England are the most familiar. Driving the summit level through a deep cutting or tunnel may cut through the water table as well as underground sources of water. [17], On the Erie Canal, some loaded boats needed a swell to get out of the lock, particularly lumber boats, being top heavy, would list to one side and get stuck in the lock, and needed a swell to get them out. If the chamber is not full, the top gate is secure; and if the chamber is not completely empty, the bottom gate is secure (in normal operation, therefore, the chamber cannot be open at both ends). The principle of operating a lock is simple. More modern techniques include casting of iron or bronze, drop forging and ( most... 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