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Southerly Northshore Shipyard Ltd. Used Southerly 15 Listings. Your Search Clear all filters. Filter Boats By Condition. More� YEAR BUILT Any year built Pictures Of Small Pontoon Boats China Pictures Of Small Pontoon Boats China Pontoon Small Pictures Boats China Of max Any to. Advanced Search. Sort By Back. View Results. Filter Boats By Back. These terms can also in different places or to different people mean either a two-chamber staircase e. Also, "double lock" less often, "twin lock" is often used by novices on the English canals to mean a wide 14 ft lock, presumably because it is "double" the width of a Pictures Of Small Pontoon Boats China Pictures Of Small Pontoon Boats China narrow lock, and allows two narrow boats going in the same direction to "double up".

These are properly known as broad locks. A "stop" lock is a very low-rise lock built at the junction of two rival canals to prevent water from passing between them. During the competitive years of the English waterways system , an established canal company would often refuse to allow a connection from a newer, adjacent one.

This situation created the Worcester Bar in Birmingham , where goods had to be transshipped between boats on rival canals only feet apart. Where a junction was built, either because the older canal company saw an advantage in a connection, or where the new company managed to insert a mandatory connection into its Act of Parliament, then Pictures Of Small Pontoon Boats China the old company would seek to protect and even enhance its water supply.

Normally, they would specify that, at the junction, the newer canal must be at a higher level than their existing canal. 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 Pictures Of Small Pontoon Boats China Pictures Of Small Pontoon Boats China Pictures Of Small Pontoon Boats China lock , because it was to stop water flowing continuously between the newer canal and the older, lower one. The lock would be under the control of the new company, and the gates would, of course, "point" uphill � towards the newer canal.

This would protect the water supply of the newer canal, but would nevertheless "donate" a lockful of water to the China Pontoon Pictures Small Of Boats Pictures Of Small Pontoon Boats China older company every time a boat went through. In times of excess water, of course, the lock "bywash" would continuously supply water to the lower canal. When variable conditions meant that a higher water level in the new canal could not be guaranteed, then the older company would also build a stop lock under its own control, with gates pointing towards its own Pictures Of Small Pontoon Boats China Pictures Of Small Pontoon Boats China Pictures Of Small Pontoon Boats China Pictures Of Small Pontoon Boats China canal which could be closed when the new canal was low.

This resulted in a sequential pair of locks, with gates pointing in opposite directions: one example was at Hall Green near Kidsgrove , where the southern terminus of the Macclesfield Canal joined the Hall Green Branch of the earlier Trent and Mersey Canal. The four gate stop lock near Kings Norton Junction, between Pictures Of Small Pontoon Boats China Pictures Of Small Pontoon Boats China the Stratford-upon-Avon Canal and the Worcester and Birmingham Canal was replaced in by a pair of guillotine lock gates which stopped the water flow regardless of which canal was higher.

These gates have been permanently open since nationalisation. Many stop locks were removed or converted to a single gate after nationalisation in The newer canal was not always at a higher level than Pictures Of Small Pontoon Boats China Pictures Of Small Pontoon Boats China the one it joined. For instance, there is a very shallow lock at Autherley Junction , where the Birmingham and Liverpool canal now part of the Shropshire Union Canal met the older Staffordshire and Worcestershire Canal , built in The Nicholson guide shows that a boater travelling south along the newer canal locks "up" before turning north or south onto the older Staffordshire and Worcestershire Pictures Of Small Pontoon Boats China Pictures Of Small Pontoon Boats China Pictures Of Small Pontoon Boats China Canal � so the Shropshire Union Canal gains a small lockful of water each time a boat passes.

However, the gain is tiny since the level difference is so small that it is sometimes possible to open both gates at once.

There are several examples where locks have been built to a round plan, with more than two exits from the lock chamber, Pictures Of Small Pontoon Boats China Pictures Of Small Pontoon Boats China Pictures Of Small Pontoon Boats China Pictures Of Small Pontoon Boats China Pictures Of Small Pontoon Boats China Pictures Of Small Pontoon Boats China each serving a different water level.

Thus the lock serves both as a way of changing levels and as a junction. The circular plan of the lock allows boats within it to rotate to line up with the appropriate exit gate. A drop lock allows a short length of canal to be lowered temporarily while a boat passes under an obstruction such Pictures Of Small Pontoon Boats China Small Pictures Pontoon Boats Of China as a low bridge. During canal restoration, a drop lock may be used where it is impractical or prohibitively expensive to remove or raise a structure that was built after the canal was closed and where re-routing the canal is not possible.

A drop lock can consist of two conventional lock chambers leading to a sump pound, or a single long chamber incorporating Pictures Of Small Pontoon Boats China Pictures Of Small Pontoon Boats China Pictures Of Small Pontoon Boats China the sump � although the term properly applies only to the second case. As the pounds at either end of the structure are at the same height, the lock can only be emptied either by allowing water to run to waste from the sump to a lower stream or drain, or less wastefully by pumping water back up to the canal.

Particularly in Pictures Of Small Pontoon Boats China Pictures Of Small Pontoon Boats China the two-chamber type, there would be a need for a bypass culvert, to allow water to move along the interrupted pound and so supply locks further down the canal. In the case of the single-chamber type, this can be achieved by keeping the lock full and leaving the gates open while not in use.

While the concept has been suggested in a number Pictures Of Small Pontoon Boats China Pictures Of Small Pontoon Boats China Pictures Of Small Pontoon Boats China Pictures Of Small Pontoon Boats China Pictures Of Small Pontoon Boats China 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. It can be emptied by pumping � but as this uses a lot of electricity the method used when water supplies are adequate is to drain the lock to a nearby burn. A flood lock Pictures Of Small Pontoon Boats China Pictures Of Small Pontoon Boats China is to prevent a river from flooding a connected waterway. It is typically installed where a canal leaves a river.

At normal river levels, the lock gates are left open, and the height of the canal is allowed to rise and fall with the height of the river. However, if the river floods beyond a safe limit for the canal, then the gates Pictures Of Small Pontoon Boats China Pictures Of Small Pontoon Boats China are closed and an extra lock created until the river drops again.

Since this is a true lock it is possible for boats to leave the canal for the flooded river despite the difference in water levels though this is not likely to be wise or more sensibly to allow boats caught out on the flood to gain refuge in the canal.Pictures Of Small Pontoon Boats China

Note that if the canal is simply a navigation cut connecting two stretches of the same river, the flood lock will be at the upstream end of the cut the downstream end will have a conventional lock. Flood locks which have been used only as flood gates see below are often incapable of reverting to their former purpose without refurbishment.

That is, where Pictures Of Small Pontoon Boats China Pictures Of Small Pontoon Boats China Pictures Of Small Pontoon Boats China Pictures Of Small Pontoon Boats China only outer gates are ever closed probably because a waterway is not a true commercial one, and therefore there is no financial imperative for a boat to venture out onto a flooded river inner gates soon suffer from lack of maintenance.

A good example is on the Calder and Hebble Navigation , where structures referred to in the boating guides as "Flood Locks" are Pictures Of Small Pontoon Boats China Pictures Of Small Pontoon Boats China Pictures Of Small Pontoon Boats China clearly only capable of being used for flood-prevention, not for "penning" boats to or from the river in flood.

A flood gate or stop gate is the cheaper equivalent of a flood lock. Only one set of gates exist, and so when the river is higher than the canal, the gates are closed and navigation ceases. These are quite common in the French Of Small Pictures Pontoon Boats China Pictures Of Small Pontoon Boats China Pictures Of Small Pontoon Boats China inland waterways system. Flood gates may also be used to sub-divide long canal pounds or protect, in case of bank collapse, the surrounding area if this is lower than the water level of the canal.

They are commonly found at the ends of long embankments and at aqueducts. These gates are often overlooked because they lack balance beams and are only a little higher than normal canal level.

Where a lock is tidal i. The "upstream" pointing doors will then fail to do their job, and will simply drift open. To prevent water flowing the wrong way through the lock, there will need to be at least one set of gates pointing in the "wrong" direction.

If it is desirable that boats can use the lock Pictures Of Small Pontoon Boats China Pictures Of Small Pontoon Boats China Pictures Of Small Pontoon Boats China Pictures Of Small Pontoon Boats China Pictures Of Small Pontoon Boats China Pictures Of Small Pontoon Boats China in these circumstances, then there needs to be a full set of gates pointing towards the tidal or river side. The usual method is to have gates pointing in opposite directions at both ends of the chamber alternatively, the "paired stop lock" arrangement of two separate sequential locks pointing in opposite directions would work here � but would require an extra chamber.Pictures Of Small Pontoon Boats China Pictures Of Small Pontoon Boats China

If navigation is not required or impossible at one "extreme" e. A sea lock is one that connects a canal or river directly with an estuary or ocean.

A tidal lock is generally any lock that connects tidal with non-tidal water. This includes a lock between a tidal river and the non-tidal reaches, or between a tidal river and a canal, or a sea lock. However, the term usually refers specifically to a lock whose method of operation is affected by the state of the tide. An inlet lock is to regulate water from a feeder canal or a river into the main canal.

In some cases, the inlet lock may double as a lift lock to allow boats into the river slackwater. Note that in Pictures Of Small Pontoon Boats China Pictures Of Small Pontoon Boats China Pictures Of Small Pontoon Boats China the example on the right, the feeder canal was originally George Washington's Little Falls Skirting Canal which was part of the Potomac Company 's canals, later re-purposed as a feeder canal for the Chesapeake and Ohio Canal. The world's largest lock was, until , the Berendrecht Lock , giving access to the Port of Antwerp in Belgium.

In the Kieldrecht Lock in the Pictures Of Small Pontoon Boats China Pictures Of Small Pontoon Boats China same port became the largest. The lock is m 1, ft long, and 68 m ft wide and drops The size of locks cannot be compared without considering the difference in water level that they are designed to operate under.

Lock staircases are used in an attempt to reduce the total volume of water required in relation to the amount of useful work Pictures Of Small Pontoon Boats China Pictures Of Small Pontoon Boats China done.

The useful work done relates to the weight of the vessel and the height it is lifted. When a Small Electric Powered Pontoon Boats China vessel is lowered the consumption of potential energy of the water consumed is considered. An alternative to locks is a boat lift ; facilities of this type, e. The 29 locks on the Mississippi River are typically feet m long while tug and barge Pictures Of Small Pontoon Boats China Pictures Of Small Pontoon Boats China China Boats Pictures Of Pontoon Small Pictures Of Small Pontoon Boats China combinations are as much as 1, feet m long consisting of as many as 15 barges and one tug.

In these cases, some of the barges are locked through, using partially opened lock valves to create a current to pull the un-powered barges out of the lock where they are tied up to wait for the rest of the barges and the tug Pictures Of Small Pontoon Boats China Pictures Of Small Pontoon Boats China Of Boats China Small Pictures Pontoon to pass through the lock. It can take as much as an hour and a half to pass the lock. The gates of a Guillotine lock work in a way similar to a sluice gate, but most canal lock gates are hinged to swing like doors.

Every November, the large lock of the Hiram M. Chittenden Locks better known locally as the "Pictures Of Small Pontoon Boats China Pictures Of Small Pontoon Boats China Pictures Of Small Pontoon Boats China Pictures Of Small Pontoon Boats China Ballard Locks" in reference to the Seattle neighborhood they are located in was emptied for maintenance, as seen in the November pictures below.

This provides an opportunity to visualize how a lock works without the water obscuring the bottom of the lock. For reference, the picture far left shows the lock in operation, with a tug and a barge loaded with sand and Pictures Of Small Pontoon Boats China Pictures Of Small Pontoon Boats China gravel waiting for the gates to open.

In the bottom left corner of the picture may be seen the cut-out in the side wall that contains the gate when open. The lock has three pairs of gates, one pair at each end and one pair in the middle so that half the length of the lock can be used when the whole length is not required, thus saving water. The barely visible person walking along the bottom of the lock in the second picture gives an indication of the vast size of this lock.

In both pictures of the end gates, the string of penstock openings are visible along the sides at the bottom. The water entering and leaving the lock flows by gravity through these Pictures Of Small Pontoon Boats China Small Of China Pontoon Boats Pictures Pictures Of Small Pontoon Boats China openings. It requires around 15 minutes to fill or empty the lock. Hiram M. Chittenden Locks : tug and barge in lock when full. This type of gate was a Dutch invention in the early 19th century. The Van gate has the special property that it can open in the direction of high water solely using water pressure.

This gate type was primarily used Pictures Of Small Pontoon Boats China to purposely flood certain regions, for instance in the case of the Hollandic Water Line. Nowadays this type of gate can still be found in a few places, for example in Gouda. The design of a Van gate is shown in the image on the lower right.

When the tube connecting the separate chamber with the high water level side of the sluice Pictures Of Small Pontoon Boats China is closed and the connection with the low water level side opened, the water level in the separate chamber will drop to the level on the low water level side of the sluice. The surface area of the gate separating the chamber from the high water level side of the sluice is larger than that of the gate closing the sluice.

This Pictures Of Small Pontoon Boats China results into a net force that opens up the sluice. In ancient times river transport was common, but rivers were often too shallow to carry anything but the smallest boats. Ancient people discovered that rivers could be made to carry larger boats by making dams to raise the water level.

The water behind the dam deepened until it spilled over the top creating Pictures Of Small Pontoon Boats China a weir. The water was then deep enough to carry larger boats. This dam building was repeated along the river, until there were "steps" of deep water. The development of dams and weirs created the problem of how to get the boats between these "steps" of water. An early and crude way of doing this was by a flash lock. A flash lock Pictures Of Small Pontoon Boats China consisted essentially of a small opening in the dam, which could be quickly opened and closed.

On the Thames in England, this was closed with vertical posts known as rymers against which boards were placed to block the gap. When the gap was opened, a torrent of water would spill out, carrying a "downstream" boat with it, or allowing an "upstream" boat to Pictures Of Small Pontoon Boats China be man hauled or winched through against the flow. When the boat was through, the opening would be quickly closed again. The "gate" could also be opened to release a 'flash' downstream to enable grounded boats to get off shoals, hence the name.

This system was used extensively in Ancient China and in many other parts of the world. But this method was Pictures Of Small Pontoon Boats China Pictures Of Small Pontoon Boats China Pictures Of Small Pontoon Boats China Pictures Of Small Pontoon Boats China Pictures Of Small Pontoon Boats China dangerous, and many boats were sunk by the torrent of water.

Since this system necessarily involved lowering the level in the pound, it was not popular with millers who depended on a full head of water to operate their equipment. This led to constant battles, both legal and physical, between the navigation and milling interests, with rivers being closed to navigation if there Pictures Of Small Pontoon Boats China was any shortage of water. It was mainly this conflict, which led to the adoption of the pound lock in medieval China, as this means that relatively little water is consumed by navigation.

A more sophisticated device was the staunch or water gate, consisting of a gate or pair of mitred gates which could be closed and held shut by water pressure Boats Pictures Pontoon China Of Small Pictures Of Small Pontoon Boats China Pictures Of Small Pontoon Boats China when the river was low, to float vessels over upstream shallows at times of low water. However, the whole upstream head of water had to be drained by some auxiliary method approaching modern sluices before a boat could pass. Accordingly, they were not used where the obstacle to be passed was a mill weir.

The natural extension of the staunch was to provide Pontoon Pictures Small Of China Boats an upper gate or pair of gates to form an intermediate "pound" which was all that need be emptied when a boat passed through. This type of lock, called a pound lock was known in Imperial China and Europe.

The Songshi or History of the Song Dynasty, volume , biography 66, records how Qiao Weiyue, a high-ranking tax administrator, was frustrated at the frequent losses incurred when his grain barges were wrecked on the West River near Huai'an in Jiangsu.

The soldiers at one double slipway, he discovered, had plotted with bandits to wreck heavy imperial barges so that they could steal the spilled grain.

In Qiao installed a pair of sluice-gates two hundred and fifty feet apart, the entire structure roofed over like a building. By Pontoon Of Small China Pictures BoatsPontoon Small Pictures Of Boats China Pictures Of Small Pontoon Boats China g> siting two staunch gates so close to one another, Qiao had created a short stretch of canal, effectively a pound-lock, filled from the canal above by raising individual wooden baulks in the top gate and emptied into the canal below by lowering baulks in the top gate and raising ones in the lower.

A turf-sided lock is an early form of canal Pictures Of Small Pontoon Boats China Of China Pictures Boats Small Pontoon lock design that uses earth banks to form the lock chamber, subsequently attracting grasses and other vegetation, instead of the now more familiar and widespread brick, stone, or concrete lock wall constructions.

This early lock design was most often used on river navigations in the early 18th century before the advent of canals in Britain. The sides of the turf-lock are sloping so, Pictures Of Small Pontoon Boats China Pictures Of Small Pontoon Boats China when full, the lock is quite wide. Consequently, this type of lock needs more water to operate than vertical-sided brick- or stone-walled locks. On British canals and waterways most turf-sided locks have been subsequently rebuilt in brick or stone, and so only a few good examples survive, such as at Garston Lock , and Monkey Marsh Lock , on the Kennet and Avon Canal.Pictures Of Small Pontoon Boats China Pictures Of Small Pontoon Boats China

The main problem caused by locks is that, each time a lock goes through one fill�empty cycle, a lockful of water tens of thousands up to millions of litres is released to the lower pound.

In more simplistic terms, on a canal where only one boat will fit into a lock, a boat travelling from the summit pound to the lowest pound is Pictures Of Small Pontoon Boats China Pictures Of Small Pontoon Boats China Pontoon Pictures Small Of Boats China Pictures Of Small Pontoon Boats China Pictures Of Small Pontoon Boats China Pictures Of Small Pontoon Boats China accompanied on its journey by one 'personal' lockful of water.

A boat going the other way also transfers a lockful of water from the summit pound to the lowest pound. To prevent the canal from running dry, some method must be used to ensure that the water supply at the canal summit is constantly replenished at the rate that the water is being Pictures Of Small Pontoon Boats China drained downwards.

This is, of course much more of a problem on an artificial canal crossing a watershed than on a river navigation. When planning a canal, the designer will attempt to build a summit level with a large reservoir , or one supplied by an artificial watercourse from a distant source, or one as long as possible to act as its own reservoir Pictures Of Small Pontoon Boats China Pictures Of Small Pontoon Boats China or which cuts across as many springs or rivers as possible or all of these.

Driving the summit level through a deep cutting or tunnel may cut through the water table as well as underground sources of water. Where it is clear that natural supply will not be sufficient to replenish the summit level at the rate that water will be used or Pictures Of Small Pontoon Boats China to allow for unexpected periods of drought the designer may plan for water to be back- pumped back up to the summit from lower down.

Such remedies may of course be installed later, when poor planning becomes apparent, or when there is an unforeseeable increase in traffic or dearth of rain. On a smaller scale, some local pumping may be required at particular Pictures Of Small Pontoon Boats China Pictures Of Small Pontoon Boats China points water is continually recycled through some locks on the Kennet and Avon canal. A way of reducing the water used by a lock is to give it one or multiple reservoirs, whose levels are intermediate between the upper and lower pounds.

These reservoirs can store the water drained from the lock as a boat descends, and release it to fill the next time a boat ascends. This saves half the amount of water lost downhill in each fill�empty cycle. Generally these reservoirs are called "saving basins". For example, the Hindenburg-lock in Hannover , Germany, built � has two lock chambers of m length, each of which would use 42, m 3 of water for a full locking cycle.

Due to the use of 10 water Pictures Of Small Pontoon Boats China Pictures Of Small Pontoon Boats China Pictures Of Small Pontoon Boats China saving basins, only 10, m 3 of water are used. A more recent example is the Rhine�Main�Danube Canal with 13 saving locks out of a total of 16 locks. On English canals, these reservoirs are called "side ponds". The Droitwich Canal , reopened in , has a flight of three locks at Hanbury which all have operational side ponds. They are now out of use, Pictures Of Small Pontoon Boats China Pictures Of Small Pontoon Boats China Pictures Of Small Pontoon Boats China and in some cases have been filled in, because British Waterways considered that it was too easy to misuse them and flood the surrounding area.

These extended intermediate pounds are sometimes confused with side ponds. As well as the "static" approaches mentioned earlier various types of contouring, excavating, and spanning , there were many ingenious "dynamic" solutions, mostly variations on the boat lift or Pictures Of Small Pontoon Boats China Pictures Of Small Pontoon Boats China Pictures Of Small Pontoon Boats China Pictures Of Small Pontoon Boats China the inclined plane.

These tend to be more expensive to install and operate, but offer faster transit and waste less water. An inclined plane consists of a cradle to hold a barge or caisson a box full of water in which a barge can float which moves on rails sideways up a slope from one waterway to the other.

Since the box is "Pictures Of Small Pontoon Boats China Pictures Of Small Pontoon Boats China Pictures Of Small Pontoon Boats China Pictures Of Small Pontoon Boats China wet" filled with water , Archimedes' principle ensures that the caisson always weighs the same, regardless of the size of boat being carried or even if it contains only water. This makes for easy counterbalancing by a fixed weight or by a second caisson. The motive power may be steam or hydraulic, or may come from overbalancing the top caisson with extra water from Pictures Of Small Pontoon Boats China Pictures Of Small Pontoon Boats China the upper waterway.

There are no working waterway inclined planes in the UK at the moment, but the remains of a famous one can be seen at Foxton in Leicestershire on the Leicester arm of the Grand Union Canal.

The plane enabled wide-beam boats to bypass the flight of ten narrow locks, but failure to make improvements at the other end of the Pictures Of Small Pontoon Boats China Pictures Of Small Pontoon Boats China arm and high running costs led to its early demise. A marine railway is similar to a canal inclined plane in that it moves boats up or down a slope on rails. However, the vessel is carried in a dry carrying frame, or cradle, rather than in a water-filled caisson.

The principle is based on the patent slip , used for hauling vessels Pictures Of Small Pontoon Boats China Pictures Of Small Pontoon Boats China out of the water for maintenance. In operation, a boat is navigated into the carrying frame, which has been lowered into the water. The boat is secured to the cradle, possibly by raising slings under the hull using hydraulics , and the cradle is hauled out of the water and up the hill with a cable. At the top of the slope, the cradle is lowered into the upper waterway, and the boat released.

As the boat is not floating, Archimedes' principle does not apply, so the weight lifted or lowered by the device varies � making counterbalancing by dead weights or a second boat carriage more difficult. In some locations, such as the Big Chute Marine Railway on the Trent-Severn Waterway , in Ontario , Canada, a marine Pictures Of Small Pontoon Boats China Pictures Of Small Pontoon Boats China Pictures Of Small Pontoon Boats China Pictures Of Small Pontoon Boats China Pictures Of Small Pontoon Boats China railway was installed as a temporary measure at the planned site of a flight of conventional locks.

In this and several other cases, the locks were never built, and the marine railway continued to serve on a permanent basis. The Falkirk Wheel , the world's first rotating boat lift, acts as the centrepiece of the restoration of the Forth and Clyde and Union Pictures Of Small Pontoon Boats China Pictures Of Small Pontoon Boats China Pictures Of Small Pontoon Boats China Canals.

The Wheel replaced a flight of locks which formerly connected the canals and which were filled in in It was the winning design in a competition to design a new lock. Visitors can now take a boat trip on the Wheel and be lifted over feet 30 m in a few minutes compared to the time it took when the original lock Pictures Of Small Pontoon Boats China staircase operated. Another derivative is the Peterborough lift lock which is a boat lift located on the Trent Canal in the city of Peterborough, Ontario , Canada and is Lock 21 on the Trent-Severn Waterway.

Its dual lifts are the highest hydraulic boat lifts in the world, rising This was a considerable accomplishment when conventional locks usually only had a 2 m 6. Each Pictures Of Small Pontoon Boats China Pontoon Pictures Small Of Boats China lift has a capacity of 1, tonnes. The basins are feet 43 m long, 33 feet 10 m wide and 9 feet 10 inches 3.

The vertical distance lifted is 65 feet 20 m. The Trent-Severn has another similar lift lock at Kirkfield, with basins of the same dimension, but which lifts over a smaller vertical distance. In this underwater lift, the chamber was 80 ft long and 60 ft 18 m deep and contained a completely enclosed wooden box big enough to take a barge.

This box moved up and down in the 60 ft 18 m deep pool of water. Apart from inevitable leakage, the Small Fast Pontoon Boats 30 water never left the chamber, and using the lock wasted no water. Instead, the boat entered the box and was sealed in by the door closing behind it, and the box itself was moved up or down through the water. When the box was at the bottom of the chamber, it was under almost 60 feet 18 m of water � at a pressure of three atmospheres, in total.

One of these "locks" was built and demonstrated to the Prince Regent later George IV , but it had various engineering problems and the design was not put into use on the Coal Canal. Possibly inspired by Weldon's caisson lock, William Congreve in patented a "hydro-pneumatic double balance lock" in which two adjacent locks containing pneumatic caissons could be raised and lowered in counterbalance by the movement of compressed air from one caisson to the Pictures Of Small Pontoon Boats China Pictures Of Small Pontoon Boats China other.

In about the Regents Canal Company built one of Cheap Small Pontoon Boats For Sale In Malaysia these locks at the site of the present-day Camden Lock , north London. Here the motivation was, again, water supply problems. The company insisted on various modifications to Congreve's design; the resulting installation proved to be unsatisfactory, and was soon replaced by conventional locks.

Looking superficially similar to the caisson lock is the Pictures Of Small Pontoon Boats China Pictures Of Small Pontoon Boats China shaft lock. Shaft locks consist of a deep shaft with conventional upper gates. The lower gates are reached through a short tunnel. The gates only close off this approach tunnel so do not have to reach the full height of the lock. The fall would have been 16 metres 52 ft , astonishing in However the approach tunnel proved to be unusable in times Pictures Of Small Pontoon Boats China Pictures Of Small Pontoon Boats China of flood and the shaft lock was replaced by a 2-rise staircase in This new concept in lock design has yet to be installed on any waterway.

It is basically a shaft lock with a diagonal shaft. The proposal is for a long tube of reinforced concrete, of a size to accommodate the boats being lifted, to be built on the slope Pictures Of Small Pontoon Boats China Pictures Of Small Pontoon Boats China Pictures Of Small Pontoon Boats China Pictures Of Small Pontoon Boats China between the upper and lower levels. The bottom of the tube is sealed with a strong watertight door, but there is a single pair of conventional lock gates at the top, installed a boat's length from the far wall of the tube.

The change in level is achieved by filling the tube with water from the top pound, or by draining. The Pictures Of Small Pontoon Boats China vessel floats on the surface of the water, with a guide float or pontoon , shaped to fit the tube, floating alongside to keep it clear of the walls.

Side ponds, piped from the main tube, are incorporated to save water. In replacing a traditional flight or staircase of locks, a considerable time saving is anticipated.

It differs from the similar caisson lock design in that the boat does not have to be carried in a submerged chamber. The "Diagonal Lock Advisory Group" has identified several sites in Britain where the new design could be installed, either on new waterways or canals under restoration. At the Three Gorges Dam on the Yangtze River Chang Jiang in China there are two stairsteps of five large ship locks each Pictures Of Small Pontoon Boats China Pictures Of Small Pontoon Boats China m long and 35 m wide for ten-thousand-tonne ships.

In addition to this there will be a boat lift a large elevator capable of moving a three-thousand-ton ship vertically in one motion. The locks and the boat lift provide a total lift of up to metres.

Locks restrict the maximum size of ship able to navigate a waterway, and some key canals have Pictures Of Small Pontoon Boats China Pictures Of Small Pontoon Boats China given rise to the name of standard ship sizes, such as the Panamax and the Seawaymax.

From Wikipedia, the free encyclopedia. Device for raising and lowering boats or ships. Not to be confused with Loch. It is not to be confused with Watergate architecture.

Top gate of a lock, showing the balance beams and paddle winding gear. Lock gate controls on a canal. Play media. Main article: Lock keeper. Main article: Flood gate. Main article: Flash lock. Main article: Canal inclined plane. Main article: Boat lift. Main article: Caisson lock. United Kingdom portal Transport portal. Science and Civilisation in China. Volume Cambridge: Cambridge University Press. Images of England. Archived from the original on 16 November Retrieved 4 September Bath: Millstream Book.

ISBN Google Books. Retrieved 20 May