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L&L Staircase locks.


dmr
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1 minute ago, ditchcrawler said:

Bascote

Yes, that's the one. That Nicholson is in the back cabin and the beds made now so didn't want to climb over it.

Have been using the Coventry for our North to South transits of late (as you know ūüėÄ) so have need done that lock for 3 or 4 years now.

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19 minutes ago, dmr said:

Yes, that's the one. That Nicholson is in the back cabin and the beds made now so didn't want to climb over it.

Have been using the Coventry for our North to South transits of late (as you know ūüėÄ) so have need done that lock for 3 or 4 years now.

The staircase 2 at Bascote is a real oddity, as it replaced two separate narrow locks during the 1930s widening

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11 hours ago, magpie patrick said:

 I don't think ideas on water supply and consumption were that well developed, and even now when I'm looking at canal restoration it is often leakage and evaporation that are the biggest concern. If a flight of locks is used three times a day it's consumption may have been inconsequential, not so much once traffic exceeded all expectations. There are other instances where water supply seems to have been given less thought - compare the variance of depth on the Staffs and Worcs locks with the uniformity of the Shropshire Union locks

 

Evaporation and leakage must make a large contribution to losses - which (separate subject) makes one question the modern policy of restricting boat movements as a panacea for water shortages.

 

In times past, lockage seems to have been a major concern whether correctly or not; I have in mind stop locks and compensation locks.  But perhaps the concern was more acute when another company could be held to account!

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35 minutes ago, Richard Carter said:

The staircase 2 at Bascote is a real oddity, as it replaced two separate narrow locks during the 1930s widening

I think by the 1930s widening electric back pumping was available so presumably water wastage wasn't such a concern. 

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48 minutes ago, Tacet said:

Evaporation and leakage must make a large contribution to losses - which (separate subject) makes one question the modern policy of restricting boat movements as a panacea for water shortages.

 

In times past, lockage seems to have been a major concern whether correctly or not; I have in mind stop locks and compensation locks.  But perhaps the concern was more acute when another company could be held to account!

 

If you look at old canal pictures there are NO canalside trees. I read somewhere that transpiration is the biggest loss on some pounds.

On busy and heavily locked canals I am pretty sure that boat movement is a very big factor.

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2 minutes ago, dmr said:

 

If you look at old canal pictures there are NO canalside trees. I read somewhere that transpiration is the biggest loss on some pounds.

On busy and heavily locked canals I am pretty sure that boat movement is a very big factor.

Didn't the Basingstoke publish something about how much water is lost due to all the trees along its banks

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I'm not an engineer (let alone a canal engineer) but would trees have a significant effect unless the roots had pushed through the clay puddle? In which case you have bigger problems than transpiration?

 

In fact by providing shade they could reduce evaporation (possibly compensated for by the rainfall that doesn't actually make it to ground (water) level)

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8 hours ago, Richard Carter said:

The staircase 2 at Bascote is a real oddity, as it replaced two separate narrow locks during the 1930s widening

 Yes, I think it's the only one that went the other way - two separate locks becoming a staircase. The new locks are longer as well as wider and I think they were a bit tight on room. Also, by then, some idea of "standard design" had crept in, so whereas the engineer of yore would have put two locks close together or the upper one close to the bridge above the locks, the 1930's engineer did not

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6 minutes ago, 1st ade said:

I'm not an engineer (let alone a canal engineer) but would trees have a significant effect unless the roots had pushed through the clay puddle? In which case you have bigger problems than transpiration?

 

In fact by providing shade they could reduce evaporation (possibly compensated for by the rainfall that doesn't actually make it to ground (water) level)

 

It may not surprise you, it is rather more complicated than that. 

Clay is not perfectly waterproof,  a canal loses 5-10mm a day of it's water level in summer through the clay lining. The rate of seepage is affected by how wet the soil is behind the puddle, if the soil is saturated, no seepage, if it's dry, more seepage. A tree just behind the clay dries the soil out.

Trees absorb a lot of water, I looked at an aqueduct on the long abandoned Bude canal some years ago - a tree had been cut down some years earlier to prevent further root damage to the structure, but instead the soil around the root ball had got wet without the tree to absorb the moisture,  and the masonry was bulging as a result

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21 hours ago, dmr said:

and whilst Pluto is here?

 

Why are all the swing bridges operated from the non-towpath side?

You said that a single person could maybe handle multiple boats on a staircase, but the swing bridges tie up a person who can then take little part in boat moving.

The only thing that I can think off is it makes it marginally easier for the horse and rope to pass???.

It does make it easier for horse drawn operation, but you also need to think about how a canal is constructed. The towpath is almost always on the 'lower' side when a canal follows a contour, as it usually does. This means the towpath side is composed of made-up earth, so putting in foundations for a swing bridge would be easier and cheaper if the bridge was on the off side, on firmer ground. With horse boating, the horse can usually carry on by itself, so whoever is leading the horse can operate the swing bridge with not major loss in time. The attached drawing shows the rope guides used on L&LC swing bridges, this example being Spencer's Bridge, near Burscough.

 

At locks, the single person I mentioned was the lock keeper, who was there to ensure that boatmen operated the locks correctly and recorded their passage. He did not necessarily have to help boats passing through. On the slope of lock flights, these are discussed in the Railway & Canal Historical Society's Waterways History Research Group's Occasional Paper 72, and I seem to recall that a list of riser locks was also produced by one member of the group.

Spencers swing bridge.jpg

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3 hours ago, magpie patrick said:

It may not surprise you, it is rather more complicated than that. 

Clay is not perfectly waterproof,  a canal loses 5-10mm a day of it's water level in summer through the clay lining. The rate of seepage is affected by how wet the soil is behind the puddle, if the soil is saturated, no seepage, if it's dry, more seepage. A tree just behind the clay dries the soil out.

Trees absorb a lot of water, I looked at an aqueduct on the long abandoned Bude canal some years ago - a tree had been cut down some years earlier to prevent further root damage to the structure, but instead the soil around the root ball had got wet without the tree to absorb the moisture,  and the masonry was bulging as a result

The lining of a canal was unlikely to have been clay, except if it was available locally. The lining was made from a mixture of suitable soil mixed with water, loam and small stones, and laid down in layers, perhaps 8 inches thick, until the lining was around two to three feet thick. For trees along the towpath, there was discussion in the Gentleman's magazine in 1792/1793 about the effect of such trees. The Canal du Midi had trees planted along the towpath about 100 years after the canal was completed, partly to make conditions shadier for the boatmen, but they also thought that the evaporation reduction would be greater that the extraction of water by the trees. Evaporation was less of a problem the further north the waterway. Early canal engineers would divide water usage into approximate thirds of lockage, evaporation and leakage, basing a canal's water requirement on these figures.

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4 hours ago, magpie patrick said:

 Yes, I think it's the only one that went the other way - two separate locks becoming a staircase. The new locks are longer as well as wider and I think they were a bit tight on room. Also, by then, some idea of "standard design" had crept in, so whereas the engineer of yore would have put two locks close together or the upper one close to the bridge above the locks, the 1930's engineer did not

 

This all makes sense - it looks like there was hardly a boat's length between the narrow locks! (here OS 25", 1905)

 

1246459899_BascoteLocksOS25in_1905.jpg.4bbe839c209bc0456f9196ad2d119675.jpg

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13 hours ago, Dave123 said:

I think by the 1930s widening electric back pumping was available so presumably water wastage wasn't such a concern. 

 

Was there back pumping there in the 1930s? I only know of it being installed in the 1990s between Leamington and Napton. The staircase has side ponds, so there was some concern about water use.

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38 minutes ago, Richard Carter said:

 

Was there back pumping there in the 1930s? I only know of it being installed in the 1990s between Leamington and Napton. The staircase has side ponds, so there was some concern about water use.

There was certainly back pumping at Knowle. It was brought back into use in the dry summer of 1976, and Bob Knight, the lockkeeper at the time, showed me round the engine house. It was powered by a two cylinder Bolinder semi diesel engine, which had originally been fitted to a Regents Canal Company tug, with a flat belt drive off the flywheel down to a centrifugal pump below the floor. You could hear the engine running from the top of the flight!  The backpumping was so successful that a new electric motor was later installed, driving the original pump. I believe the Bolinder is now at Ellesmere Port.

There is another pumping station at the other end of the summit which pumps water from the bottom of Garrison Locks to the top of Camp Hill.

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33 minutes ago, David Mack said:

There was certainly back pumping at Knowle. It was brought back into use in the dry summer of 1976, and Bob Knight, the lockkeeper at the time, showed me round the engine house. It was powered by a two cylinder Bolinder semi diesel engine, which had originally been fitted to a Regents Canal Company tug, with a flat belt drive off the flywheel down to a centrifugal pump below the floor. You could hear the engine running from the top of the flight!  The backpumping was so successful that a new electric motor was later installed, driving the original pump. I believe the Bolinder is now at Ellesmere Port.

There is another pumping station at the other end of the summit which pumps water from the bottom of Garrison Locks to the top of Camp Hill.

 

Yes, and there had been back pumping at Braunston since time immemorial, of course - I suppose it is most effective where a compact flight separates two long pounds, which was not the case on the Warwick and Napton canal. How many pumps did BW have to install in a mighty panic in the 90s, was it seven? (Radford, Fosse, Woods, Welsh Road, Bascote, Itchington/Stockton and Calcutt), which all had to be working together to actually get water up to the Braunston level, whence it was further pumped at Napton and Braunston flights ...

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