275:—were without bottoms and were arranged so that their sides dropped into deep underwater channels formed by "minor walls" inside the main walls. The vertical movement of the two caissons was effected by a balance pipe ("the channel of communication") passing under the lock floor between the two caisson chambers (but with a slight upturn to reach above the water levels), so that causing an increase of water level in one caisson ("the water of compression") displaced air through the pipe, thus forcing a corresponding decrease in the water level in the other. This increased the buoyancy of the latter caisson, which accordingly rose as the first sank. A connecting underwater chain passing through rollers, while not in itself doing any work, controlled the relative positions. Boats were admitted through double gates; the inside ones on the caisson "adjusted to fit close [
320:. The main caisson was connected by ropes passing over grooved pulleys to two smaller, counterbalancing caissons. Brownill's innovation was to place wedges ("inclined planes") opposite the upper and lower fixed openings so that as the main caisson moved into place, powered by water being added or released from the counterbalancing caissons, rollers acting against the wedges forced it against a padded frame surrounding the opening. The "conductor" was to have control of a lever to release the rollers when the vertical gates were slid shut for the next ascent or descent.
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183:(b:?1754, d:1810) built a half-scale model. He claimed that his design would solve the problem of water supply in dry seasons or at greater elevations, be cheaper than building aqueducts or tunnels, and be quicker to operate than the number of surface locks his design could replace. He patented his invention as the 'Hydrostatick Caisson Lock'. The full-sized box, or "trunk", would probably have displaced about 270
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differences. Such locks, each of which would only raise and lower boats through small height differences of a few feet, would not suffice when large height differences had to be tackled nor when water was in short supply. The caisson (or caisoon) was thought to be one solution, although it transpired that the technology of the day was not capable of achieving this type of construction economically.
301:. However it was found the fastest overall time was six minutes and that the effort required rendered the operator "incapable of further exertion". Furthermore, as the operation of the device depended upon air pressure inside the caissons (whether the means of moving them was by varying this air pressure or otherwise) when contractor
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is floated into a sealed watertight box and raised or lowered between two different canal water levels. It was invented in the late 18th century as a solution to the problem posed by the excessive demand for water when conventional locks were used to raise and lower canal boats through large height
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It was designed primarily as a water-saving measure, and also was an attempt to minimise construction costs compared with other engineering solutions of the time. In use it was capable of replacing up to seven conventional locks. Other design benefits were speed of boat descent/ascent, and only a
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The May 1799 test, above, occurred when a party of investors was aboard the vessel and they nearly suffocated before they could be freed. Work on the second lock was suspended (the third lock had not been started) and early in the following year an
271:. Here the motivation was, principally, water supply problems but also to effect a quicker passage of vessels, as those going in opposite directions could pass in the lock. The caissons—always submerged, as at
191:. The box would have needed to be strong enough to withstand the pressure of 50 ft (15 m) of water i.e. about 22 psi (150 kPa) gauge pressure at the bottom of the chamber.
289:, removable weights or a small winch could overcome inertia and move the caissons. In a practical demonstration at Hampstead Road Congreve later elected to deploy an
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delivered them and they were found to leak air, the scheme failed. In 1818, after many unsuccessful repair attempts, the company substituted conventional locks.
243:, to carry boats’ cargoes in wheeled tubs, was built instead. Eventually a flight of nineteen locks on a longer alignment up the slope was constructed, with a
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and weighed about 170 tonnes, including the water in it, so about 100 tonnes of ballast would have been needed to give
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The first lock was completed in 1797 under Weldon's supervision. The device was demonstrated to the Prince Regent (later
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releasing into one caisson, estimating that one man could achieve raising and lowering in three minutes—the company's
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281:] to those of the outer". Congreve's patent then envisaged that having achieved "absolute equipoise" (
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Uhlemann, Hans-Joachim (2002): "Canal Lifts and
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built a double caisson lock (or "hydro-pneumatic lock") at the site of the present-day
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little loss of water when operating compared with a conventional boat lock.
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570:"History of the Caisson Lock On the Somersetshire Coal Canal"
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470:(1798 ed.). London: Charles Dilly. pp. 316–318.
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General view of the agriculture of the county of
Somerset
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466:(1795). "Robert Weldon's Hydrostatick or Caisson-Lock".
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The system depended on the submerged, sealed box (the "
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of water in 12 hours, used to recirculate the water.
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267:, north London. The designer was military engineer
49:. Unsourced material may be challenged and removed.
653:The Repertory of Arts Manufactures and Agriculture
680:London's canal: the history of the Regent's canal
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247:Steam Pumping Station, capable of lifting 5,000
142:Contemporary engraving of the lock at Combe Hay
599:Oxford English Dictionary, Second Edition 1989
549:Bath Royal Literary and Scientific Institution
494:Bath Royal Literary and Scientific Institution
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702:The Regent’s Canal: London’s Hidden Waterway
625:. David and Charles, Newton Abbot, England.
171:The caisson lock was first demonstrated at
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515:"History of the Somersetshire Coal Canal"
308:A patent granted to Jonathan Brownill, a
109:Learn how and when to remove this message
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574:The Somersetshire Coal Canal (Society)
519:The Somersetshire Coal Canal (Society)
440:. The Somersetshire Coal Canal Society
398:Somersetshire Coal Canal and Railways.
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400:David and Charles, Newton Abbot, UK.
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47:adding citations to reliable sources
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297:did not permit the installation of
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623:Lost Canals of England and Wales
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490:"The Combe Hay Caisson Lock"
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801:Locks of the United Kingdom
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730:"Account of new patents".
720:Spencer 1961, pp 44–45; 49
659:: 281–285. 23 March 1813.
641:Patent 3670, 23 March 1813
601:, Oxford University Press.
202:rock stratum in the area.
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678:Spencer, Herbert (1961).
545:"The Somerset Coal Canal"
461:Robert Weldon, quoted in
438:"Levels at Rowley Bottom"
380:Caisson (water transport)
134:Operation of caisson lock
796:Locks (water navigation)
621:Russell, Ronald (1971):
396:Clew, Kenneth R (1977):
299:stationary steam engines
121:Not to be confused with
704:. Waterways World Ltd.
700:Faulkner, Alan (2005):
682:. Putnam. p. 36.
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338:United Kingdom portal
261:Regents Canal Company
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365:Canal inclined plane
43:improve this article
791:History of Somerset
738:: 466. 1 May 1828.
265:Hampstead Road Lock
255:Other installations
206:Method of operation
123:Caisson (lock gate)
786:Canals in Somerset
580:on 11 October 2006
525:on 13 October 2006
391:General references
259:In April 1815 the
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444:6 September
234:Abandonment
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99:March 2022
69:newspapers
584:6 October
529:8 October
476:614002204
370:Boat lift
273:Combe Hay
196:George IV
554:8 August
499:8 August
324:See also
318:caissons
216:buoyancy
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167:History
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