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Flash Locks - how did they work in practice?


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A close up of Pershore watergate taken from a copy of the same postcard. My copy was posted on July 8th. 1908.

I don't think that the boat is Pisgah, it looks like a cabin-less narrowboat to me.

 

File2098b.jpg

 

 

That's a very small rise on the weir. So presumably there was a significant slope to the water on the pounds between such flash locks. Otherwise you would never gain the height.

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That's a very small rise on the weir. So presumably there was a significant slope to the water on the pounds between such flash locks. Otherwise you would never gain the height.

This particular flash lock was only needed to give sufficient water for craft to enter Pershore lock, about a mile upstream.

Pershore lock was made deeper so that the flash lock was no longer necessary.

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That's a very small rise on the weir. So presumably there was a significant slope to the water on the pounds between such flash locks. Otherwise you would never gain the height.

 

See Paul G's response, but to add generally flash locks didn't have a big rise, the greater the rise and fall, the less practical they were.

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The Worcestershire Archive and Archaeology Service hold photographs for the derelict navigation taken between 1952-1956.

There may be some pictures of the two water gates in this collection:

 

http://discovery.nationalarchives.gov.uk/details/rd/1d40d28d-cae9-4207-b14a-7d2c2415147e#4-2-4

 

Contact details here

http://discovery.nationalarchives.gov.uk/details/a/A13532331

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Not a flash lock, there is a proper lock by the river bank, but shows nicely the removable weir posts take in France.

 

Whilst I've heard of these needle weirs I've never seen one, or a picture of one, before - very interesting

 

I assume the idea is that the needles are small enough that they can be lifted against quite a head of water?

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I assume the idea is that the needles are small enough that they can be lifted against quite a head of water?

 

That's right. As I said a bit back we've actually seen them (pertuis in French) being drawn at the barrage where the river Seille meets the Saône. I've not seen them put back in, and that could be a bit more fiddly. I'm still not clear how the larger paddles are drawn or replaced - is that simply by hand too?

One thing I've just twigged is that a boat going down through the gap does not necessarily have to be launched willy-nilly as in the Hornblower book - it would be possible to use the winch that normally tows craft up to let them down more steadily and in a (semi)controlled manner.

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This is one of the flash locks at Accolay, used for rafting timber on the River Cure next to the Canal de Nivernais. It does show why flash locks used for navigation can only work with a very small difference in level. The water is held back by 'needles' of wood, perhaps 4 inches square, the bottom of which rest on a beam fitted across the base of the 'lock'. The upper beam is pivotted at one end so it can be moved out of the way. Weirs of this type were very common in France, and I have come across them in Germany and Poland, with a winch made by Tangye of Birmingham being used on one at Wroclaw (formerly Breslau).

gallery_6938_1_303479.jpg

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The stop lock at Dutton on the Trent & Mersey canal was at one time a type of flash lock. The level difference is only about 2~3 inches and before being converted to a pound lock had only a single top gate (so I was told). This was winched open as shown on the attached photograph from Claymoore Navigation's old photos.

 

attachicon.gifclay109.jpg

 

Often wondered about that, at the chamber is odd in shape, wider than 7ft if no where near 14, with neither gate being the same size. Makes sense. A lot of stop-locks can be pushed through with a few on the gate and the boat, if the levels are right and if going up hill.

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This is one of the flash locks at Accolay, used for rafting timber on the River Cure next to the Canal de Nivernais. It does show why flash locks used for navigation can only work with a very small difference in level. The water is held back by 'needles' of wood, perhaps 4 inches square, the bottom of which rest on a beam fitted across the base of the 'lock'. The upper beam is pivotted at one end so it can be moved out of the way. Weirs of this type were very common in France, and I have come across them in Germany and Poland, with a winch made by Tangye of Birmingham being used on one at Wroclaw (formerly Breslau).

gallery_6938_1_303479.jpg

post-261-0-36403400-1480536823_thumb.jpg

post-261-0-56026500-1480536858_thumb.jpg

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  • 1 month later...

What started this discussion was the carriage of grain and long craft being used. I understand that flash locks had a relative short fall generally. Travelling down stream had the comparative easy journey travelling with the flow of water. Travelling upstream was a different matter and required mechanical aid such as capstans to draw craft up against the flow. Length of craft may have been an issue in view of the difficulty in bringing it up against the current. Long craft did exist, I believe, on the Kennet, which would have passed onto the Thames at Reading. The Thames is noted for the long navigation that extended as far as Lechlade with flash locks above Oxford, as well as south of this place.

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  • 4 years later...
On 09/01/2017 at 12:22, Heartland said:

What started this discussion was the carriage of grain and long craft being used. I understand that flash locks had a relative short fall generally. Travelling down stream had the comparative easy journey travelling with the flow of water. Travelling upstream was a different matter and required mechanical aid such as capstans to draw craft up against the flow. Length of craft may have been an issue in view of the difficulty in bringing it up against the current. Long craft did exist, I believe, on the Kennet, which would have passed onto the Thames at Reading. The Thames is noted for the long navigation that extended as far as Lechlade with flash locks above Oxford, as well as south of this place.

On the fenland waterways flash locks were referred to as "staunches" and worked the other way round - they were left open and only closed when a boat needed deeper water for navigation. This is only one step above building a dam behind the boat on the way upstream and demolishing it on the way back! 

 

I think length would be an issue in both directions, and I guess there was an "awkward" length going downstream where there was a risk the bow would just plow underwater and sink the boat, but boats both shorter and longer would be less susceptible to this. With a longer boat there may be a risk of breaking it's back as well with the bow one side of the gradient and the stern the other. I'm guessing narrow boats must have gone through the Thames flash locks above Oxford as these didn't disappear until after the closure of the Thames and Severn and narrow boats certainly traded there, but it must have been an uncomfortable experience. 

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10 hours ago, Andy_B said:

It's still happening <snip>

 

That's a tidal barrage to prevent salt water going to far inland, rather than a flash lock to maintain a navigable depth.

 

And its utter mayhem at opening time.

 

springy

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43 minutes ago, magpie patrick said:

On the fenland waterways flash locks were referred to as "staunches" and worked the other way round - they were left open and only closed when a boat needed deeper water for navigation. This is only one step above building a dam behind the boat on the way upstream and demolishing it on the way back! 

 

I think length would be an issue in both directions, and I guess there was an "awkward" length going downstream where there was a risk the bow would just plow underwater and sink the boat, but boats both shorter and longer would be less susceptible to this. With a longer boat there may be a risk of breaking it's back as well with the bow one side of the gradient and the stern the other. I'm guessing narrow boats must have gone through the Thames flash locks above Oxford as these didn't disappear until after the closure of the Thames and Severn and narrow boats certainly traded there, but it must have been an uncomfortable experience. 


You can still see the remnants of one on the Little Ouse near Lakenheath. I think it was taken out of use in 1960 when the cutoff channel was built, with the siphon at Hockwold and a new (if rather short!) lock in Brandon. And I think at the back of the island just above Great Barford bridge - the stone "chamber" looks very short.

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10 hours ago, Andy_B said:

 

I found this series of videos some while back - they're amazing to watch and it's easy to waste hours doing so. We had a superficially similar contract carrying sea dredged aggregates around the Thames estuary but I can't even begin to imagine doing the sort of boating they have to. I do love the idea of sitting back and using your feet to turn the wheel as a lot of them do though.  😃

 

Tam

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On 26/11/2016 at 11:23, Tam &amp; Di said:

If there were only 6 locks the fall will have been quite substantial at each one which is another thing difficult to imagine.

I'm going right back to the start of the thread for another look at this.

 

Rivers have gradients and many were navigable without any improvements. In the 20th century the Trent between Nottingham and Newark, and then downstream of Newark, is an example of a river that was already navigable by quite large vessels but then improved. Four of the locks (Cromwell, Gunthorpe, Hazleford and Stock Bardolph) we know today didn't exist in any way, shape or form 100 years ago, barges just coped with shallows and rapids. There were locks at Newark, but when heading upstream one ran out of impounded river and had to deal with the currents and shallows. 

 

There being only six locks doesn't mean they had a great fall, the flash lock would have lifted a boat as high as the weir crest, and then the boatman was on his own until the next one, a bit of flat (to the naked eye) impounded water and then back to the shallows and rapids until one gets to the next weir.  

 

The Bristol Avon didn't have flash locks, once the mills impounded it in the 13th century it was unnavigable until proper locks were built in the 18th century, it had been navigable with difficulty prior to the 13th century at which point mills became economically more important than navigation. I suspect on the Thames either navigation was too important just to ignore or there were, even then, established rights. 

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But presumably an unimproved river could only be navigated at times of higher river flow, and would have required the use of significant numbers of men or animals to drag boats over shoals and rapids, particularly when travelling upstream.

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1 hour ago, David Mack said:

But presumably an unimproved river could only be navigated at times of higher river flow, and would have required the use of significant numbers of men or animals to drag boats over shoals and rapids, particularly when travelling upstream.

Navigability of unimproved rivers is not a field I've spend much time on, but there's little doubt it was a bit precarious. Looking worldwide, some rivers were navigable in a downstream direction only, which suited log rafting, some were navigable on a seasonal basis (and improvements didn't always solve this) some were not navigable without works to improve them. The Wye was never improved but was navigated to Hereford and occasionally to Hay in the 19th Century

 

The point I was really making was that the fall of the locks may not add up to the fall of the river - 100 years ago on the Trent the fall from Holme to Newark had no locks, now those locks fall 21 feet.  Newark didn't suddenly get lower nor Holme higher, the river gradient was eased

Edited by magpie patrick
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Flash locks were usually found where the navigation was flowing water. The possible fall at the lock would depend upon the slope of the river/canal below the lock. Lock falls varied, approximately, between eighteen inches to five feet. If the river was fairly level below the lock, the flash of water would raise the water level sufficiently to make passing a large lock fall possible. On the Stecknitz Canal, lock falls varied from around 0.35 metres to 1.5 metres. In 2009, the Deutsches Wasserhistorische Gesellschaft published an article on the water usage of the locks on the Stecknitz Canal by Kai Wellbrock.

 

The use of flash locks did not necessarily affect the length of boat. For example, on the route from Moscow to St Peterburg through Vishny Volochek, which used flash locks extensively on the Msta River, boats could be over 100 feet in length. The later Mariinski and Berezina Canals used chamber locks, and this certainly restricted the size of boats using the Berezina system to around L&LC size. This canal was used for high value cargoes, with the larger Msta river and Mariinski canals used by larger boats usually carrying grain or other bulk cargoes. Most traffic on these latter two canals was in one direction - grain from the Volga - the boats being broken up for wood on arrival in St Petersburg. All three systems were closed during the winter, and had a comparatively short operational season in the spring. By summer, water levels had declined, making navigation difficult. Even so, the Msta route was carrying 100,000 tons annually at the end of the 18th century, possibly making it the most heavily used inland waterway in Europe at the time.

 

The Englishman, Captain John Perry, was one of the first canal builders in Russia, and he took over construction of the Volga-Don Canal from a German engineer in the early 1700s, though this canal was not completed due to problems with the local aristocracy. Perry went on to survey the various routes between Moscow and St Petersburg circa 1712, and suggested that the route eventually used by the Mariinski Canal was the best. It is the only one of these three Russian waterways still in use.

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On 19/02/2021 at 10:16, Tam &amp; Di said:

 

I found this series of videos some while back - they're amazing to watch and it's easy to waste hours doing so. We had a superficially similar contract carrying sea dredged aggregates around the Thames estuary but I can't even begin to imagine doing the sort of boating they have to. I do love the idea of sitting back and using your feet to turn the wheel as a lot of them do though.  😃

 

Tam

One of the boaters in this video is clearly of the 'Steve Haywood' school of boating!

 

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I wonder how many of those barges will ever get converted to green energy propulsion?  Seeng these videos makes the proposal to ban diesels from uk inland waterways a bit of a pointless exercise in the grand scheme of things.

Edited by Ronaldo47
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19 hours ago, Ronaldo47 said:

I wonder how many of those barges will ever get converted to green energy propulsion?  Seeng these videos makes the proposal to ban diesels from uk inland waterways a bit of a pointless exercise in the grand scheme of things.

No poke without smoke......   as you say, aint running a DPF there are they!

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