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Flash Locks - how did they work in practice?


Tam & Di
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This is sort of related to my thread on wooden boats cf iron/steel ones. Has anyone ever encountered a flash lock in their travels, and might know the actual process of how it is worked?

Di is commissioned to write a book, sort of about carriage of grain on the Thames. There is plenty of reference to barges up to about 130' x 16' (not dissimilar to a French Freycinet size) carrying grain in the C17 from Henley into London, and there were some 6 flash locks to negotiate. We obviously know in simplistic terms what a flash lock is, but can't see how the rymers/paddles were pulled to allow barges through - where did the people stand to pull them - what sort of loaded draft could boats have (we assume they would have to be fairly shallow). If there were only 6 locks the fall will have been quite substantial at each one which is another thing difficult to imagine.

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I doubt anyone living has used one, so much must be speculative. Those I have seen depicted in sketch show rymers slotted down into a gate much like those that were still in use at Shepperton weir.

 

So I will speculate. A beam or footway atop the gate would allow access, and each rymer pulled allowing much water to flow into the reach below simultaneously lowering the reach above, until the gate could be manhandled open by winch or whatever other means and not necessarily when levels were equal - hard and dangerous work and several lives have been lost on frosty days with a river in flood. Boats would be hastened through downstream, or winched up from the bank going upstream and the gate then closed and rymers re-inserted to satisfy a miller. The downstream boat would race on with the flush or flash, while the upstream might of necessity wait until sufficient water was available to continue passage.

 

Thank heavens for pound locks.

 

There's an old thread here:

http://www.canalworld.net/forums/index.php?showtopic=14657#entry229762

 

Wikipedia has a bit too, though I'm sure that has been accessed.

https://en.wikipedia.org/wiki/Flash_lock

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I read somwhere of the constant battle between the miller who wanted to conserve water to use to power the mill and boat transport who needed a smooth passage through the lock. The miller would urge the barggees to pass through the lock as soon as possible somtimes inviting disaster to the boat.

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fascinating to consider the grain and hay barges that travelled way up the Thames in the early days.

 

I viewed a house on the weir stream just above Culham Lock, it was a converted barn, probably 18th century, one of the first ever converted for residential use by Herbert Asquith, about the turn of the 19/20 century. Previously hay or grain barges loaded up there before going down to London.

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Flash locks, where does one start? what follows is somewhat general and simplified

 

First off, they only really worked with quite light traffic flows: there'd be a couple of days typically between flashes taking place, dependent upon flow sometimes it might be weeks. In particular navigation above them was impeded until the water made up again.

 

There were two different modus operandi - normally open and normally closed. The Thames one's were normally closed, retaining a water level: this is typical of a situation where the flash locks were related to mills. Fenland flash locks were normally open - level until you needed to make the river upstream navigable.

 

The typical model on the Thames seems to have been to have needles, rhymers or whatever they were called locally, very much like the rest of the weir these could be removed, but for the flash lock bit the beam they rested on could also be swung sideways out of the way: that's why this bit was navigable - descending barge masters didn't need to risk decapitation.

 

Elsewhere, flash locks had gates with lost of paddles in them - Pershore Water Gate on the Warwickshire Avon was this format and survived in use into the 1950's: A barge, "Pisgah" had to get through it on route to mills at Evesham, and pictures exist of it being winched up against the flow. Pisgah was about 70 feet by 13 I think.

 

I don't know the actual head retained by individual flash locks, certainly not on the Thames - they weren't really suited to anything more than a couple of feet though. Pershore Watergate was about 2 foot 6 inches, Cropthorne Appear to have been the same and the half locks on the Somerset Rivers were a foot or two. The idea of a ten foot fall through one doesn't bear thinking about, and the level would take way too long to make up. On the River Lugg there were two flash locks close together downstream of Leominster, probably because of the steep gradient two weirs were close together, and one might imagine that these two flash locks would have worked almost like a pound lock.

 

Edited to add

 

Flash Lock.jpg

 

This is a fairly well known drawing of a Thames Flash Lock: the keeper has a paddle in his hand, and the beam he is on would move out of the way for a larger vessel

 

Cropthorne_flashlock (2).JPG

 

This is Cropthorne on the Avon, which was removed in the 1950's (I think Pershore lasted until 1962) - the navigation bit is the large gate on the right of the picture.

Edited by magpie patrick
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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.

 

post-5142-0-83096500-1480191385_thumb.jpg

Edited by Stevec
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The 'barrages' on the Yonne are a bit of a flash lock affair, lots of hefty wooden beams that are slid into the water from a walkway. Not really a flash lock as such but a bit of a hybrid I suppose. The locks are more or less conventional apart from sloping sides and lever operated bottom gate paddles but if you close an eye and squint a bit you can sort of imagine a flash lock.

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Agree with Pearley - just about the whole of Chapter 1 of the Atropos was about travelling as a passenger (although he can't resist getting his coat off and getting stuck in) on a canal, and as always an excellent read overall.

 

Have you considered looking into the history of French canals, as they had an extensive network which was both in advance of ours and behind it! They definitely sued flash locks extensively. Come to that, are there parts of the third world that still use this system? Might make for an interesting picture, even if the techniques were different from 18th century Europe.

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Good description in CS Foresters "Hornblower and The Atropos"

This is the relevant text:

 

There was still plenty of daylight when they came out into the Thames valley and Hornblower, looking down to starboard, could see the infant river—not such an infant at its winter level—running below. Every turn and every lock brought the canal nearer to the stream, and at last they reached Inglesham, with Lechlade church steeple in view ahead, and the junction with the river. At Inglesham lock Jenkins left his horses and came back to speak to Hornblower. "There's three staunches on the river next that we have to run, sir," he said. Hornblower had no idea what a staunch was, and he very much wanted to know before he had to "run" them, but at the same time he did not want to admit ignorance. Jenkins may have been tactful enough to sense his difficulty; at least he gave an explanation. "They're dams across the river, sir," he told Hornblower. "At this time o' year, with plenty of water, some o' the paddles are kept out for good, at the towpath end o' the staunch. There's a fall o' five or six feet" "Five or six feet?" repeated Hornblower, startled. "Yes, sir. 'Bout that much. But it isn't a real fall, if you know what I mean, sir. Steep, but no more." "And we have to run down it?" "Yes, sir. It's easy enough, sir—at the top, leastways." "And at the bottom?" "There's an eddy there, sir, like as you'd expect. But if you hold her straight, sir, the nags'll take you through." "I'll hold her straight," said Hornblower. "O' course you will, sir." Lechlade Bridge just ahead of them—the staunch was half a mile beyond, Jenkins said. Although the air was distinctly cold now Horn-blower was conscious that his palms, as they rested on the tiller, were distinctly damp. To him now it appeared a wildly reckless thing to do, to attempt to shoot the staunch inexperienced as he was. He would prefer—infinitely prefer—not to try. But he had to steer through the arch of the bridge—the horses splashed fetlock deep there—and then it was too late to do anything about his change of mind. There was the line of the staunch across the stream, the gap in it plainly visible on the port side. Beyond the staunch the surface of the river was not visible because of the drop, but above the gap the water headed down in a steep, sleek slope, higher at the sides than in the middle; the fragments which floated on the surface were all hurrying towards it, like people in a public hall all pressing towards a single exit. Hornblower steered for the centre of the gap, choking a little with excitement; he could feel the altered trim of the boat as her bows sank and her stern rose on the slope. Now they were flying down, down. Below, the smooth slope narrowed down to a point, beyond which and on each side was the turbulent water of the eddy. He still had steerage way enough to steer down the point; as he felt die boat answer the helm he was momentarily tempted to follow up the mathematical line of thought presented by that situation, but he had neither time nor really the inclination. The bows hit the turbulent water with a jar and a splash; the boat lurched in the eddy, but next moment the towlines plucked them forward again. Two seconds' careful steering and they were through the eddy and they were gliding over a smooth surface once more, foam-streaked but smooth, and Horn-blower was laughing out loud. It had been simple, but so exhilarating that it did not occur to him to condemn himself for his earlier misgivings. Jenkins looked back, turning in his saddle, and waved his whip, and Hornblower waved back. (1937)

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Thanks everyone - there is some really useful information here. Some barrages on French rivers still use pertuis for their weir barrages as mentioned by Bee - we've even seen the one on the Seille at La Truchère being opened in time of flood to encourage the water level to drop more quickly. The removable pertuis there are only about 3” square x 6’ long so are not too difficult to handle as they are drawn, but it would take a long time to pull enough for a boat’s width and anyway they are drawn from a fixed platform. Patrick and Mick Worm's posts are particularly useful for our purposes of trying to estimate how much the old wooden vessels might load.
As mentioned we found reference to craft of up to about 130' x 16', and as this is fairly similar to the size of a French Freycinet péniche it did give something for us to relate to. At this point we are assuming with Patrick that the loaded draft could not be more than about 2'. On the other hand the Hornblower excerpt (thank you Mr Animal) suggests that it could have been more, though there is the depth in the pound itself to consider too. As we’ve seen an article saying that at the time there were only 5 flash locks from Henley, (presumably to Staines, as the tide reached there) they would have to have that sort of fall.
We do have a friend here who took his péniche over a weir on one occasion (deliberately, to avoid waiting for the lock) when the river was in flood and I’ve contacted him to ask what his draft was at the time. These old craft would be swim ended, and that would help going each way through the gap as it would reduce the amount they dived going down and give a bit of lift when towed/winched up.

 

I'm assuming too that the weight of the hull itself would be some 80 tons, which unless my calculations are grossly in error means at 2’ draught they'd only have on some 35 tons of grain (Di's trying to keep all dimensions in imperial at the moment which is giving me a bit of brain overload each time I have to convert my figures)

Any further reference and comment gratefully received.

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With the Marne and Seine in flood conditions, I've gone over them several times going downstream, but only once upstream only over the weir at Evry, it took me a good 10 minutes to pass the weir, centimeter by centimeter, with engine the on full throttle, I didn't really feel reassured, and was ever so happy when I finally passed it.

 

If there's still a bit of a difference in level, they'll let downstream traffic go over the weirs, and upstream traffic through the locks, which will be indicated with the respective signage.

 

Peter.

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You have to remember that a lot more water was coming down the rivers in those days, so there would be quite a rise on the river even without the locks. I assume the flash locks were placed downstream of shallow shoals, so would only raise a couple of foot, especially as once opened the upper level would drop, and lower level increase.

 

Mike

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Flash locks, where does one start? what follows is somewhat general and simplified

 

First off, they only really worked with quite light traffic flows: there'd be a couple of days typically between flashes taking place, dependent upon flow sometimes it might be weeks. In particular navigation above them was impeded until the water made up again.

 

There were two different modus operandi - normally open and normally closed. The Thames one's were normally closed, retaining a water level: this is typical of a situation where the flash locks were related to mills. Fenland flash locks were normally open - level until you needed to make the river upstream navigable.

 

The typical model on the Thames seems to have been to have needles, rhymers or whatever they were called locally, very much like the rest of the weir these could be removed, but for the flash lock bit the beam they rested on could also be swung sideways out of the way: that's why this bit was navigable - descending barge masters didn't need to risk decapitation.

 

Elsewhere, flash locks had gates with lost of paddles in them - Pershore Water Gate on the Warwickshire Avon was this format and survived in use into the 1950's: A barge, "Pisgah" had to get through it on route to mills at Evesham, and pictures exist of it being winched up against the flow. Pisgah was about 70 feet by 13 I think.

 

I don't know the actual head retained by individual flash locks, certainly not on the Thames - they weren't really suited to anything more than a couple of feet though. Pershore Watergate was about 2 foot 6 inches, Cropthorne Appear to have been the same and the half locks on the Somerset Rivers were a foot or two. The idea of a ten foot fall through one doesn't bear thinking about, and the level would take way too long to make up. On the River Lugg there were two flash locks close together downstream of Leominster, probably because of the steep gradient two weirs were close together, and one might imagine that these two flash locks would have worked almost like a pound lock.

 

Edited to add

 

attachicon.gifFlash Lock.jpg

 

This is a fairly well known drawing of a Thames Flash Lock: the keeper has a paddle in his hand, and the beam he is on would move out of the way for a larger vessel

 

attachicon.gifCropthorne_flashlock (2).JPG

 

This is Cropthorne on the Avon, which was removed in the 1950's (I think Pershore lasted until 1962) - the navigation bit is the large gate on the right of the picture.

This is Pershore water gate, with a barge that is likely to be "Pisgah" just entering.

You can still see a few remnants of brickwork on the site today.

I remember "Pisgah" operating when I was younger. She was in trade between Avonmouth and Partridge's Mill at Pershore until it was destroyed in a fire around 1974.

Last thing I heard was that "Pisgah" was operating as a pleasure craft somewhere in France.

post-5065-0-12845000-1480348592_thumb.jpg

Edited by PaulG
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We knew two successive owners of Pisgah here in France - the first was Tony Paris who I believe was the person who bought it out of trade. I've not seen it for several years now. It is still on the list of DBA .member's barges though.

 

Unfortunately I don't seem to be able to enlarge the photo to see any detail - I found it on wikimaps too, but couldn't enlarge that copy either.

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We knew two successive owners of Pisgah here in France - the first was Tony Paris who I believe was the person who bought it out of trade. I've not seen it for several years now. It is still on the list of DBA .member's barges though.

 

Unfortunately I don't seem to be able to enlarge the photo to see any detail - I found it on wikimaps too, but couldn't enlarge that copy either.

Hi Tam - I uploaded that photo to Wikimapia a long time ago.

Unfortunately I can't seem to find the original now.

I may have it on a backup I made of an old computer before I binned it - I'll take a look when I have a chance.

 

Edited to say that I found a Frith photo with slightly better detail. You might be able to get a bigger copy from them:

The title says it is the lock, but is actually the watergate. I think the gate itself is open and you can see the rymers to the right.

http://www.francisfrith.com/uk/pershore/pershore-the-lock-c1960_p45042

post-5065-0-02698900-1480352928_thumb.jpg

Edited by PaulG
  • Greenie 1
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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.

 

 

Thanks for blowing the image up - I suspected it wasn't Pisgah and that demonstrates it. Aside from anything else I think Pisgah was motorised and wheel steered.

 

The image does show the lock mechanism very well though - if you look there are four large sluices on the gate which would allow it to be opened against a head of water.

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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

 

I agree.

That is definitely not Pisgah.

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