Details and terminology Lock (water navigation)

1 details , terminology

1.1 rise
1.2 pound
1.3 chamber
1.4 cill
1.5 gates
1.6 balance beam
1.7 paddle
1.8 winding gear or paddle gear
1.9 hydraulic paddle gear
1.10 windlass ( lock key )
1.11 turning lock
1.12 swell or swelling
1.13 lock mooring
1.14 snubbing posts

details , terminology

an empty lock chamber

for simplicity, section describes basic type of lock, pair of gates @ each end of chamber , simple rack , pinion paddles raised manually means of detachable windlass operated lock-keepers or boat s shore crew. type can found on world, terminology here used on british canals. subsequent section explains common variations.

rise

the rise change in water-level in lock. 2 deepest locks on english canal system bath deep lock on kennet , avon canal , tuel lane lock on rochdale canal, both have rise of 20 feet (6.1 m). both locks amalgamations of 2 separate locks, combined when canals restored accommodate changes in road crossings. deepest as-built locks in england considered etruria top lock on trent , mersey canal , somerton deep lock on oxford canal: both have rise of 14 ft (4.3 m). again, sources vary deepest, , in case etruria has been deepened on years accommodate subsidence. more typical rise (in england) 7–12 feet (2.1–3.7 metres) (though shallower ones can encountered). comparison, carrapatelo , valeira locks on douro river in portugal, 279 feet (85 m) long , 39 feet (12 m) wide, have maximum lifts of 115 feet (35 m) , 108 feet (33 m) respectively. 2 ardnacrusha locks near limerick on shannon navigation in ireland have rise of 100 feet (30 m). upper chamber rises 60 feet (18 m) , connected lower chamber tunnel, when descending not become visible until chamber empty.

pound

a pound level stretch of water between 2 locks (also known reach). on american canals, pound called level.

chamber

the chamber main feature of lock. watertight (masonry, brick, steel or concrete) enclosure can sealed off pounds @ both ends means of gates. chamber may same size (plus little manoeuvring room) largest vessel waterway designed; larger, allow more 1 such vessel @ time use lock. chamber said full when water level same in upper pound; , empty when level same in lower pound. (if lock has no water in @ all, perhaps maintenance work, might said empty, more described drained or de-watered .)

cill

the cill exposed in deep pont de flandre lock on canal saint-denis, paris



top gate of lock, showing balance beams , paddle winding gear



200-year-old paddle gear on wiener neustädter kanal, austria



water conservation gear on birmingham canal navigations

the cill, spelled sill, narrow horizontal ledge protruding short way chamber below upper gates. allowing rear of boat hang on cill main danger 1 warned guard against when descending lock, , position of forward edge of cill marked on lock side white line. edge of cill curved, protruding less in center @ edges. in locks, there piece of oak 9 in (23 cm) thick protects solid part of lock cill. on oxford canal called babbie; on grand union canal referred cill bumper. canal operation authorities, in united states , canada, call ledge miter sill (mitre sill in canada).

gates

gates watertight doors seal off chamber upper , lower pounds. each end of chamber equipped gate, or pair of half-gates, made of oak or elm (or steel). common arrangement, called miter gates, invented leonardo da vinci, sometime around late 15th century. when closed, pair meet @ angle chevron pointing upstream , small difference in water-level necessary squeeze closed gates securely together. reduces leaks between them , prevents being opened until water levels have equalised. if chamber not full, top gate secure; , if chamber not empty, bottom gate secure (in normal operation, therefore, chamber cannot open @ both ends). lower gate taller upper gate, because upper gate has tall enough close off upper pound, while lower gate has able seal off full chamber. upper gate tall canal deep, plus little more balance beam, winding mechanism, etc.; lower gate s height equals upper gate plus lock s rise.

balance beam

a balance beam long arm projecting landward side of gate on towpath. providing leverage open , close heavy gate, beam balances (non-floating) weight of gate in socket, , allows gate swing more freely.

paddle

a paddle – known slacker, clough, or (in american english) wicket – simple valve lock chamber filled or emptied. paddle sliding wooden (or nowadays plastic) panel when lifted (slid up) out of way allows water either enter chamber upper pound or flow out lower pound. gate paddle covers hole in lower part of gate; more sophisticated ground paddle blocks underground culvert. there can 8 paddles (two gate paddles , 2 ground paddles @ both upper , lower ends of chamber) there fewer. long period since 1970s british waterways policy not provide gate paddles in replacement top gates if 2 ground paddles existed. reason given safety, since possible ascending boat swamped water carelessly lifted gate paddle. however, without gate paddles locks slower operate , has been blamed in places causing congestion. since late 1990s preferred method has been retain or re-install gate paddles , fit baffles across them minimise risk of inundation.

on old erie canal, there danger of injury when operating paddles: water, on reaching position, push paddles force tear windlass (or handle) out of 1 s hands, or if 1 standing in wrong place, knock 1 canal, leading injuries , drownings.

winding gear or paddle gear

winding gear mechanism allows paddles lifted (opened) or lowered (closed). typically, square-section stub emerges housing of winding gear. axle of sprocket ( pinion ) engages toothed bar ( rack ) attached rodding top of paddle. lock-keeper or member of boat s shore crew engages square socket of windlass (see below) onto end of axle , turns windlass perhaps dozen times. rotates pinion , lifts paddle. pawl engages rack prevent paddle dropping inadvertently while being raised, , keep raised when windlass removed, operator can attend other paddles. nowadays considered discourteous , wasteful of water leave paddle open after boat has left lock, in commercial days normal practice. lower paddle pawl must disengaged , paddle wound down windlass. dropping paddles knocking pawl off can cause damage mechanism; paddle gear typically made of cast iron , can shatter or crack when dropped height. in areas water-wastage due vandalism problem, (for example birmingham canal navigations), paddle mechanisms commonly fitted vandal-proof locks (nowadays rebranded water conservation devices ) require boater employ key before paddle can lifted. keys officially known water conservation keys , boaters refer them t-keys, shape; handcuff keys because original locks, fitted on leeds , liverpool canal, resembled handcuffs; leeds , liverpool keys after canal; or anti-vandal keys.

hydraulic paddle gear

during 1980s, british waterways began introduce hydraulic system operating paddles, on bottom gates, heaviest operate. metal cylinder foot in diameter mounted on balance beam , contained small oil-operated hydraulic pump. spindle protruded front face , operated windlass in usual way, energy being transferred actual paddle small bore pipes. system installed , on canals became common. there turned out 2 serious drawbacks. more expensive install , maintain traditional gear , went wrong more frequently, once vandals learned cut pipes. worse, had safety defect, in paddle once in raised position not dropped in emergency, had wound down, taking deal longer. these factors led abandonment of policy in late 1990s, examples of survive on system, not removed until gates need replacing, happens every twenty years.

windlass ( lock key )

collection of lock windlasses. note: rakes clearing trash out of lock.

a windlass (also variously lock handle , iron or key ) detachable crank used opening lock paddles (the word not refer winding mechanism itself).

the simplest windlass made iron rod of circular section, half inch in diameter , 2 feet long, bent make l-shape legs of different length. shorter leg called handle, , longer leg called arm. welded end of arm square, tapered, socket of correct size fit onto spindle protruding lock winding gear.

socket: traditionally, windlasses had single socket, designed particular canal. when undertaking journey through several canals different lock-gear spindle sizes necessary carry several different windlasses. modern windlass has 2 sockets use on different canals: smaller british waterways standard spindle, fitted in 1990s everywhere, larger gear on grand union canal north of napton junction, unable/unwilling convert.
handle: handle long enough two-handed grip , far enough socket give enough leverage wind paddle or down. there may freely rotating sleeve around handle protect hands friction of rough iron against skin.
arm: long throw windlass has longer arm handle further socket give greater leverage on stiffer paddles. if throw long user, winding gate paddle, risks barking knuckles against balance beam when handle @ lowest point of arc. sophisticated modern windlass may have adjustable-length arm.
materials : windlasses individually hand forged single piece of wrought iron blacksmith. more modern techniques include casting of iron or bronze, drop forging , (the common technique) welding. boatmen had windlasses silvered (or chrome plated) increased comfort , prevent rusting. windlasses plated, popular modern choice of metal aluminium, smooth , rustproof surface has same advantages of longevity , blister-reduction, , light. 1 type of these, dunton double, has single eye, clever tapering operate either size of spindle.

on chesapeake , ohio canal, lockkeepers required remove windlasses lock paddles @ night, prevent unauthorized use.

turning lock

turning lock can mean emptying full lock, or filling empty 1 ( entered lock, , took 5 minutes turn ). used more refer lock being filled or emptied benefit of else ( lock turned boat coming other way ) , opposite ( lock set us, crew of boat coming other way turned before got there ).

swell or swelling

a swell caused opening paddle valves in lock gates, or when emptying lock. boats leave (downstream) lock, locksman open paddles create swell, flush boat out of lock. in 1 case, boatsman asked swell, is, open , shut paddles few times create waves, him off bank stuck. if boats ran aground (from being overloaded) asked passing crews tell upstream lock give them heavy swell, consisted of opening paddles on lock gate, creating surge affected whole pound below.

on erie canal, loaded boats needed swell out of lock, particularly lumber boats, being top heavy, list 1 side , stuck in lock, , needed swell them out. lockkeepers give swell them on way, ask money swell.

the erie canal management did not swelling 2 reasons. first, used water lowering water on pound above causing boats run aground. in addition, raised water level on pound below causing boats strike bridges or stuck.

lock mooring

lock mooring commonly used method of navigating lock barge travelling upstream. barge directed slack water 1 side of lock gates , volume of water decreased lock emptied barge or boat sucked out of slack water path of lock gates. effort required navigate barge or boat mouth of lock therefore substantially reduced.

snubbing posts

snubbing boat keep hitting downstream gates. note rope wrapped around snubbing post.

on horse-drawn , mule-drawn canals, snubbing posts used slow or stop boat in lock. 200-ton boat moving @ few miles hour destroy lock gate. prevent this, rope wound around snubbing post boat entered lock. pulling on rope slowed boat, due friction of rope against post. rope 2½ inches (6.3 cm) in diameter , 60 feet (18 meters) long typically used on erie canal snub boat in lock.

one incident, took place in june 1873 on chesapeake , ohio canal, involved boat henry c. flagg , drunk captain. boat leaking; crew, having partially pumped water out, entered lock 74, moving in front of boat. because failed snub boat, crashed , knocked out downstream gates. outrush of water lock caused upstream gates slam shut, breaking them also, , sending cascade of water on boat, sinking it. suspended navigation on canal 48 hours until lock gates replaced , boat removed lock.