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Passing Place in a Lock


Heartland

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I know from experience that boats can pass in Leeds & Liverpool Locks, but on narrow locks, it is  usually not possible. However it seems the Monmouthshire Canal had this arrangement at Lock 5 on the Fourteen Locks- the question is how was it done: The Source of this image is RCHS Hugh Compton (Welsh) Photo Collection

 

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Edited by Heartland
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These have been debated for years: any detailed analysis suggests they were intended as passing places:

Each bay is big enough to hold a boat, the towpath side one is rather deeper but traffic was generally one way loaded and empty back

The bays flood when the locks are full and this was a busy canal: they weren't dry docks

They are in the middle chamber of three Bratch style locks all of which are the same depth, no balancing was needed

Above and below are pairs of Bratch style locks, traffic was likely to come at a "two locks" frequency (one up one down) and a triple might have caused a logjam.

There is no evidence whether or not boats ever passed in them though, and as far as im aware no photos of these locks in use exist, although there are some of them looking useable 

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I have just translated the section of a 200 year old Austrian book on canal building which describes riser locks, both with and without side ponds. In general, the author suggests that the fall of the locks depends upon how they were operated, in that he recommended that the centre locks had less fall than those at either end by the amount of water needed for floating a boat. However, the method of operation was as used on the Canal du Midi, where the upper chambers are emptied completely. In Britain, their use has developed such that all the chambers retain enough water for floating at all times, and this would affect the fall for each lock to obtain the most water-efficient way of operation. The author also condemns having locks close together, as there is then not sufficient water in the pound to supply the next lock down without making the pound unnavigable because of too little water. The configuration here could be the result of water problems during early operation, with the chamber being widened to produce sufficient water for the locks lower down the flight, particularly as some of these locks are close together..

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1 hour ago, Pluto said:

I have just translated the section of a 200 year old Austrian book on canal building which describes riser locks, both with and without side ponds. In general, the author suggests that the fall of the locks depends upon how they were operated, in that he recommended that the centre locks had less fall than those at either end by the amount of water needed for floating a boat. However, the method of operation was as used on the Canal du Midi, where the upper chambers are emptied completely. In Britain, their use has developed such that all the chambers retain enough water for floating at all times, and this would affect the fall for each lock to obtain the most water-efficient way of operation. The author also condemns having locks close together, as there is then not sufficient water in the pound to supply the next lock down without making the pound unnavigable because of too little water. The configuration here could be the result of water problems during early operation, with the chamber being widened to produce sufficient water for the locks lower down the flight, particularly as some of these locks are close together..

I've long suspected that riser locks would work better with the locks getting shallower as one descends, but it's not an experiment one has the opportunity to try out easily!

For clarity, these have side ponds "bratch style", perhaps more accurately  "side pounds", and on paper at least the arrangement in the photo would make the middle lock use a lot more water - the locks are of even depth. By a lot more I mean of the order of another half lock full, the near side ledge would have had over 4 feet of water on it and the far side one something like 2 foot 6. As each is big enough for a boat (I have measured them, I used to live nearby) that's an extra 6 foot 6 of lock on an already 12 foot fall. 

This treble is well down the flight of fourteen, which start with a single at the top, then four pairs, then this treble, then one last pair. 

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2 hours ago, magpie patrick said:

I've long suspected that riser locks would work better with the locks getting shallower as one descends, but it's not an experiment one has the opportunity to try out easily!

 

I may not have properly understood you suspicion, but in a simple situation of a flight or staircase, over usage the rise of each one will tend towards the mean.  

By a simple situation, I mean upper and lower pounds are maintained at fixed levels, each lock has the same surface area, vertical sides and water is not introduced or drawn-off anywhere in the middle. Therefore, and broadly speaking, a low pound will tend to correct itself as boats pass through; they bring extra water from above and send down less than usual.

 

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You may not think of Austria as a place for canals, but the author of the book I am translating did build what was, in effect, an English narrow canal between Vienna and Wiener Neustadt at the start of the 19th century. The book he wrote about canal engineering - it is the only detailed contemporary book on canal construction in general written by an engineer that I have found (far better than the account in Rees Cyclopedia) - includes details of water usage on riser locks. If they are operated as on the Canal du Midi, where ALL the water in the upper chambers is used to fill those further down, leaving the chambers completely empty after a descent, then the middle locks need to have a smaller fall than the two outer ones by the depth of water in the upper and lower pounds. If you don't completely empty the upper chambers, as happens in England, the locks should have an equal fall. With the former situation, you can save much water when changing the direction of travel of boats passing through the locks by having side ponds, something which causes excessive water usage on riser locks without side ponds.

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Enough material there to start a few new threads! Instead I'll drift off-topic...

I have never understood the method of working on the Canal du Midi. Or rather I understand HOW but not WHY, it seems to demand a lot more water from the upper pound as, on descent, the whole flight is drained. Why do that? What's the advantage?

There is a third way of working staircases, when I saw them being operated on the Caledonian Canal, the water is constantly flowing through them and only the lock the boat is in needs to be worked. This, IIRC, is done by closing paddles behind the boat and opening them fully in front of it which ever way one is going. 

On 8/4/2017 at 14:29, Tacet said:

I may not have properly understood you suspicion, but in a simple situation of a flight or staircase, over usage the rise of each one will tend towards the mean.  

By a simple situation, I mean upper and lower pounds are maintained at fixed levels, each lock has the same surface area, vertical sides and water is not introduced or drawn-off anywhere in the middle. Therefore, and broadly speaking, a low pound will tend to correct itself as boats pass through; they bring extra water from above and send down less than usual.

 

In a perfect world that is correct, but I do recall a period where the locky at Bingley five rise used to keep a bit in reserve in the middle lock, and when I saw them being operated for the flotilla last October the lockies were making constant adjustments. On a single lock or a two rise leakage probably doesn't matter, but on a five rise I guess it can have an amplified effect in the further down one gets. 

My though was that Bingley five rise, instead of having a fall of 12 feet for each lock, might have (in descending order) 14,13,12,11,10 so that each lock had slightly more than the lock below needed - but I'm not going to build a model five rise with model leaks to test it! 

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The water usage for the Canal du Midi will not really be much different to that for other riser locks. Von Maillard shows in his book that if you drain the chambers completely, you need to give the middle locks a lesser fall than the two outer ones by the depth of water needed for floating a boat in the lowest and uppermost chambers. I would see one benefit in draining the chamber completely as it being easier to keep rubbish from accumulating and hence damaging the seal at mitre and sill.

Where water is left in the chamber after locking, as happens here now - though has this always happened? - the fall for each chamber would have to be equal. At the moment, I don't have the figures for Bingley, despite having copied much of the surviving historical material relative to locks. Bingley is usually just described as having a 60 foot fall, though one list suggests 59 feet 2 inches. Measurement was not that accurate when canals were built, so there could easily be a few inches difference in the falls, something I will have to chase up as the dimensions for recent lock gates should be around.

Von Maillard also suggested using side ponds fed not just from the chambers, but also kept full by feeding them via the bywash. In this case, excessive water usage by riser locks could be kept down, though canals were not generally used as intensively around 1800 as they were later in the century, and this would have an effect on the efficiency of such a system.

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6 hours ago, Pluto said:
6 hours ago, Pluto said:

Von Maillard also suggested using side ponds fed not just from the chambers, but also kept full by feeding them via the bywash. In this case, excessive water usage by riser locks could be kept down, though canals were not generally used as intensively around 1800 as they were later in the century, and this would have an effect on the efficiency of such a system.

That is, in effect, what Foxton (and Bratch) are - and indeed what Fourteen Locks are. The "side ponds" are filled by the lock above and drained by the lock below, but the bywashes are also routed through them. They act like a conventional pound between two locks, but are off line. Fourteen locks are built close together because of the severity of the climb, Foxton was, I believe, to save money without wasting water.

Whilst Von Maillards musings are of great interest, he reminds me somewhat of Sutcliffe, strong on theory but didn't get round to building much. Are there any staircases on the Weiner Neustadt Canal? 

6 hours ago, Pluto said:

Where water is left in the chamber after locking, as happens here now - though has this always happened? - the fall for each chamber would have to be equal. At the moment, I don't have the figures for Bingley, despite having copied much of the surviving historical material relative to locks. Bingley is usually just described as having a 60 foot fall, though one list suggests 59 feet 2 inches. Measurement was not that accurate when canals were built, so there could easily be a few inches difference in the falls, something I will have to chase up as the dimensions for recent lock gates should be around.

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On 8/3/2017 at 18:47, BuckbyLocks said:

There are dry docks built like this in mainland Europe, which actually operate above the working lock by raising the area temporarily, but I think this is really just a means of creating a reservoir for the next locks.  Don't believe it is a passing place at all.

There is such a lock at, I think, Salèlles-d'Aude on the canal that links Narbonne to the canal du midi. We went through the lock while a péniche was being pressure washed in the dry dock side bay.

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1 hour ago, magpie patrick said:

That is, in effect, what Foxton (and Bratch) are - and indeed what Fourteen Locks are. The "side ponds" are filled by the lock above and drained by the lock below, but the bywashes are also routed through them. They act like a conventional pound between two locks, but are off line. Fourteen locks are built close together because of the severity of the climb, Foxton was, I believe, to save money without wasting water.

Whilst Von Maillards musings are of great interest, he reminds me somewhat of Sutcliffe, strong on theory but didn't get round to building much. Are there any staircases on the Weiner Neustadt Canal? 

Yes, there was at least one three-rise on the Wiener Neustadt Canal. Von Maillard is quite an interesting person, in that he became a member of the Russian Academy of Sciences at the instigation of the French scientist and engineer, Coulomb. He then wrote a book on steam engines which was published in 1784. His other books, apart from the canal engineering one, are about the construction of the arch and about cement mortars, both cutting edge research for the time. His canal book also has a section on soil mechanics, again cutting edge technology, suggesting he knew about Chezy's research, as well as Coulomb's. Interestingly, both Frenchmen were involved with late 18th century French canals.

Although Austria is not the first place you would think of regarding canals, there was at least one late 18th century one in what is now Serbia, and plans for linking Vienna and the Danube to the other main rivers in the Austro-Hungarian Empire and the Adriatic were being develop from around 1700, with a major scheme being proposed in 1786. The Austrians also moved firewood using Trift technology, which required a good knowledge of hydraulic engineering. In engineering terms, von Maillard's book is much more important than Sutcliffe's, but you need to read Sutcliffe to get a good understanding of what was happening in this country, both for engineering and economics.

I am currently three-quarters of the way through an initial translation of von Maillard (almost 400 octo pages), and may have it ready before Christmas, but more likely in the new year.

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Did Von Maillard build the three rise with a shallow middle chamber I wonder?  The difference in depth of the middle lock would be quite prounounced, easily apparent to the naked eye when looking at the formation. 

I've also never seen any of the staircases on the Canal Du Midi, do they have sjhallower chambers in the middle, or did Von Maillard see the modus operandi and realise they would work better if they did? 

I'm slightly at a loss as to how this works anyway. The only times I've worked a staircase in this manner I've run water down from the top gates rather than from a full top chamber. In any event, if we take a three rise, and the bottom chamber is at the low water level and the middle chamber is completely empty, the top lock will only fill the bottom chamber, when you have filled that, and sailed into the middle lock, the top chamber is empty, and you'd have to use the top paddles anyway? Or am I missing something. I'm not denying that's how the french often work staircase locks, I've seen the pictures, I just don't get the logic of shallower chambers.

Edited to add - I have now realised it makes a difference going down. With the shallower dry chamber one lockful of water will suffice all the way down.

Finally all this business of dry docks in locks and filling 8 rise staircases from the top paddles would lend to support to Pluto's conclusion that traffic wasn't expected to be incessant... 

Edited by magpie patrick
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13 hours ago, magpie patrick said:

Finally all this business of dry docks in locks and filling 8 rise staircases from the top paddles would lend to support to Pluto's conclusion that traffic wasn't expected to be incessant... 

I think this is crucial in understanding canal construction. In this country, the early canals were far more successful than their promoters anticipated, leading to the inevitable water supply problems, despite water supply being central to a good engineer's design. They just didn't expect so much traffic. On the continent, early canals were very much more seasonal, and so there may have been less pressure on completing a journey quickly. I have just translated von Maillard's comments on the eight-rise locks at Fonserannes, on the Canal du Midi, where to save water boats were only allowed to pass every other day, suggesting that traffic was not so heavy. He thought they should have deviated around the hill, instead of building the tunnel at Malpas, as the deviation would have allowed the Fonserannes locks to be spread out, and thus require less water compared to the riser locks.

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On 06/08/2017 at 11:04, 1st ade said:

And leaks don't scale well if "model" means "smaller scale version of"!

Reynold's number?

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Passing place. Can't see it myself. It would only be required if the cut was too narrow to allow passing for some distance from the lock in which case two boats going one way  passing two going the other way would stop the whole thing, plus, wouldn't it make more sense to put passing places in the pounds themselves close too the lock as "laybys". Since locks were a convenient point for the collection of tolls, I wonder if it has something to do with gauging.

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It is hard to interpret the bays as dry docks, and the passing place argument appears to prevail. This was a Dadford canal and Thomas junior followed father Thomas, with the desigh of locks close together with a short space separating each lock chamber and with side pounds originally built on the Stourbridge (9 and 10), again used at the original Delph locks on the Dudley and later at the Bratch when Thomas Dadford senior rebuilt the original true Brindley staircase.

The fourteen locks can be seen on the Glamorgan O/S 6 inch  XXVIII survey, and true to the Dadford style each lock chamber has a side pond or pound. It is different to Foxton and Watford where the use of ground paddles coloured red or white manage the water passing to and from each lock chamber of the staircase.

598b2ed202cbd_FourteenLocks.png.31e7ba23fc551a8902805349b62358ac.pnged 1872-1878:

  

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On 8/8/2017 at 15:29, Theo said:

Reynold's number?

Possibly - but mainly that a model four inch head of water just won't make a six inch wide wooden gate seal properly. Magpie spent much of his childhood building model locks in our garden and I don't think any water ever went down the bywash - the lock gates leaked so much! It needed a garden hose to keep the top pound full enough for navigation and the locks, whilst great fun, were more "flash" in operation than would have been desirable in real life.

Doubtless now that both of us have grown up (chronologically if not otherwise!) we could use modern materials, neoprene seals and O Rings together with some decent workmanship to get the thing vaguely watertight.

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You need a volume of water to provide sufficient head, or weight to seal the gates unless they are built to very fine tolerances indeed. Somewhat akin to making model cars in a proportionately thin metal to the full size. They would be so weak as to almost collapse at the touch.

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On 8/8/2017 at 18:49, Sir Nibble said:

Passing place. Can't see it myself. It would only be required if the cut was too narrow to allow passing for some distance from the lock in which case two boats going one way  passing two going the other way would stop the whole thing, plus, wouldn't it make more sense to put passing places in the pounds themselves close too the lock as "laybys". Since locks were a convenient point for the collection of tolls, I wonder if it has something to do with gauging.

It may not be apparent but the lock in the photo is sandwiched between two locks with no passing place.

On 8/7/2017 at 10:26, Pluto said:

I think this is crucial in understanding canal construction. In this country, the early canals were far more successful than their promoters anticipated, leading to the inevitable water supply problems, despite water supply being central to a good engineer's design. They just didn't expect so much traffic. On the continent, early canals were very much more seasonal, and so there may have been less pressure on completing a journey quickly. I have just translated von Maillard's comments on the eight-rise locks at Fonserannes, on the Canal du Midi, where to save water boats were only allowed to pass every other day, suggesting that traffic was not so heavy. He thought they should have deviated around the hill, instead of building the tunnel at Malpas, as the deviation would have allowed the Fonserannes locks to be spread out, and thus require less water compared to the riser locks.

Regarding the bit in bold, was the Canal du Midi a commercial entity? I appreciate our promoters under-estimated demand but I find it difficult to believe that there would be a return on capital with boats only moving every other day!

A river navigation might be different of course, as creating the navigation potential has a much lower spend per kilometre

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