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Anyhow Weir Lock


Peter Thornton

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There in also lies a conumdrum, because the displacement of additional boats reduces the volume of water let down.

 

Obviously the original plan was that only full length 70' boats used the canal and these could not fit alongside a bot in the centre section

But what about a single wide beam?

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its a narrow entrance ;)

 

the unusual shape might just be to do with the physics of having a varying height natural watercourse immediately above it. narrow locks were an economy measure so putting in an angle just below the top gate might help stop the lock collapsing when the river is up. it would 'beef up' the whole structure a bit. maybe

 

The perminently leaking gates at Aynho weir make up the difference.

 

It's the same at Shipton weir

there are windows in the paddles at shipton weir lock too.

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there are windows in the paddles at shipton weir lock too.

 

Perhaps this is what the chap meant. The surface of the water certainly looks like a lock with water flowing into it from below the surface. Go and look and you'll see what I mean.....

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in case it came across as a joke it wasn't.

 

windows are cut in paddles where pounds below would otherwise tend to go low. this is obviously the case at Aynho where clearly a bywash would not be appropriate.

 

and shipton weir lock

 

and other locks around the system, Stockers at Ricky being one - how would the pound between there and springwell stay wet otherwise ?

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in case it came across as a joke it wasn't.

 

windows are cut in paddles where pounds below would otherwise tend to go low. this is obviously the case at Aynho where clearly a bywash would not be appropriate.

 

and shipton weir lock

 

and other locks around the system, Stockers at Ricky being one - how would the pound between there and springwell stay wet otherwise ?

There are holes deliberately cut through the paddles at Stockers?

Really?

How big?

Both ends of the lock?

Any supporting evidence for that?

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yes

 

John the resident at stockers with all the old tools told me. he has a couple of old paddles in his garden with 4 inch square holes cut out.

 

it is a way to feed water through a lock when a bywash would not work due to the level above the top gates being variable like at stockers, aynho and shipton, for example. springwell lock is a fair bit deeper than stockers so there would be a net loss in that pound which needs to be replaced in some way. there is a small overspill half way between stockers,and springwell to drain off the excess.

 

to clariify the ones in the garden are old ones which were replaced - he collects old canal tools and fixtures.

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its a narrow entrance wink.png

 

the unusual shape might just be to do with the physics of having a varying height natural watercourse immediately above it. narrow locks were an economy measure so putting in an angle just below the top gate might help stop the lock collapsing when the river is up. it would 'beef up' the whole structure a bit. maybe

 

 

there are windows in the paddles at shipton weir lock too.

 

The windows idea makes sense, the modern BW/CRT equivalent is to put a stop that prevents a paddle fully closing, one bottom paddle at lock 10 in Marple has this feature to prevent the pound above overflowing into people's gardens.

 

The structural integrity idea makes much less sense though, a single leaf gate sends the force backwards down the lock, so Aynho and Shipton are arguably weaker than a conventional chamber in this respect, and in any event, unless the level overtops the lock, the head of water against the top gate is never more than a couple of feet, compared to four or five feet on a conventional lock.

 

Next summer, I might spend a while at each of these locks as I go up the Oxford Canal, to have a closer look.

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The windows idea makes sense, the modern BW/CRT equivalent is to put a stop that prevents a paddle fully closing, one bottom paddle at lock 10 in Marple has this feature to prevent the pound above overflowing into people's gardens.

 

The structural integrity idea makes much less sense though, a single leaf gate sends the force backwards down the lock, so Aynho and Shipton are arguably weaker than a conventional chamber in this respect, and in any event, unless the level overtops the lock, the head of water against the top gate is never more than a couple of feet, compared to four or five feet on a conventional lock.

 

Next summer, I might spend a while at each of these locks as I go up the Oxford Canal, to have a closer look.

I was thinking of ground movement rather than the pressure of the water against the lock. a diamond chamber is more 'rigid' in theory.

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I remember this lock well...

Arriving from the river end, I moored on the landing, and approached on foot, windlass in hand. Upon reaching the lock, my first thought was 'W T F? '. I spend several minutes walking around the structure, scratching my head. Adopting my 'there's only one way to find out' mindset, I set about my first attempt to open the gate..

I must admit, that profane language was used.

Being stuborn, aswel as grumpy, I persevered, and with the strenght of the desparate, I finally managed to open the gate. Bringing the boat in was uneventfull, unlike trying to control my boat, whilst emptying the lock, in what was effectively a round lock chamber.

My,admittedly very limited, experience told me that after some time, the lock should be empty, and the bottom gates can be opened.. After a rather long time, the level had still not receded enough to facilitate this exit. Unable to spot an obvious leak, this was not helping my increasing questioning of the state of mind of the designer of this particular lock.

Was this John Rennie's idea of a practical joke??

I must shamefully admit, that more profane language was used.

At lenght, I managed to open the gates, and after pulling my boat back round into the right direction, continued my ongoing edjucasion about the canal, and it's rich variety of infastructure...

Knapton here we come.

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Aynho and Shipton lock gates are hard to open because you (we) try to open them to early

 

If you are patient the lock will fill/empty and the levels equalise. The gate will then open with ease.

 

The trouble is, when it's busy, you look at it and think that the waters coming in faster than it's going out etc and you force them to soon.

 

I go through Shipton a lot. If you leave it to its own devices, it's easy to open......... That said, I still force it before it's ready on most occasions

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  • 3 months later...

I had a good look at Aynho and Shipton weir when I was there a few days ago.

 

I am pretty sure Aynho used to have two "normal" paddles on each gate. Now there is only one, with the second one replaced by the gadget you can see in this photo, which lets a small flow of water through each gate . Although visible, it is really quite a small flow, as otherwise one would not be able to get a level. I reckon the lengthsman puts a square section device through the hole - something like an Ouse key - to adjust the sluice that is under the water.

 

I couldn't see anything equivalent at Shipton, which still has two normal paddles on the top gate. But then that has a rather larger fall anyway.

 

Some good news is that overnight mooring is possible again at Shipton - next to the lock on the River Cherwell.

 

 

DSCF2816.jpg

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  • 7 years later...

Went through Wynchnor lock today and found myself wondering why it wasnt also made larger/wider like Aynho, to let down extra water from the river Trent crossing the canal, as further downstream is the much deeper and wider Stenson lock. Just came across this thread and see it seems the consensus is that Aynho (and Shipton) are wider for structural stability from the proximity to the river? Wynchnor is some distance from where the main river crosses the canal so this might explain why it is just a normal shaped lock. Instead it just has a generous bypass weir.

Also have noticed Shipton lock has a bypass weir going under the lock landing, whilst Aynho definetly does have a permanent flow through the lock from a windoe in each paddle. Its visible in winter if the lock hasnt been used and the water is clear.

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25 minutes ago, Dave123 said:

Went through Wynchnor lock today and found myself wondering why it wasnt also made larger/wider like Aynho, to let down extra water from the river Trent crossing the canal, as further downstream is the much deeper and wider Stenson lock. Just came across this thread and see it seems the consensus is that Aynho (and Shipton) are wider for structural stability from the proximity to the river? Wynchnor is some distance from where the main river crosses the canal so this might explain why it is just a normal shaped lock. Instead it just has a generous bypass weir.

Also have noticed Shipton lock has a bypass weir going under the lock landing, whilst Aynho definetly does have a permanent flow through the lock from a windoe in each paddle. Its visible in winter if the lock hasnt been used and the water is clear.

 Wychnor is also quite a lot deeper and Stenson is several locks downstream

I believe Wychnor has a bypass sluice, which would work like the windows in the paddles but be able to carry a lot more water. 

The theory that Aynho and Shipton are diamond shaped for structural stability is just that, a theory - there is no reason for these locks to be more unstable than any other, indeed given their small fall, they should suffer fewer problems. 

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An alternative theory is that the engineer who built these two locks had a sense of humour, and thought "This will fox them in 200 years time, trying to work out why I did this. I bet they come up with all sorts of weird theories. A similar argument may explain why the Oxford switches from single to double bottom gates at Banbury (though construction did pause there for a few years).

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42 minutes ago, Scholar Gypsy said:

A similar argument may explain why the Oxford switches from single to double bottom gates at Banbury (though construction did pause there for a few years).

As does the Stratford at Lapworth (double gates above the junction, single gates below)

And the BCN does both on different flights, including the second lock up at Wolverhampton with a single bottom gate when the rest of the flight has twin bottom gates.

Edited by David Mack
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38 minutes ago, David Mack said:

As does the Stratford at Lapworth (double gates above the junction, single gates below)

And the BCN does both on different flights, including the second lock up at Wolverhampton with a single bottom gate when the rest of the flight has twin bottom gates.


Walsall lock no 6 is the opposite of that at Wolverhampton, it has a pair of mitred bottom gates in a flight where every other lock has a single leaf bottom gate.

 

I too don’t buy the structural stability argument for Aynho. Can’t see why it would make any fundamental difference.

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We will probably never know why this lock was designed this way but I have never bought in to the traditional theory. Similarly I don't buy in to the notion that best practice is to lock one boat at a time - we have often had three boats in the that lock which makes it is a lot more manageable when boating single handed . . .

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32 minutes ago, NB Alnwick said:

We will probably never know why this lock was designed this way but I have never bought in to the traditional theory. Similarly I don't buy in to the notion that best practice is to lock one boat at a time - we have often had three boats in the that lock which makes it is a lot more manageable when boating single handed . . .

And when you turn up in a 70 footer and there are a couple of shorter boats in the queue in front of you, you have to go in last, and come out first!

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17 minutes ago, David Mack said:

And when you turn up in a 70 footer and there are a couple of shorter boats in the queue in front of you, you have to go in last, and come out first!

We have never arrived at either of the diamond locks when there has been a boat suitable for sharing - we are 60'. I cannot recall what the max length is in the 'wings' but it is much shorter than folk imagine.

 

Just tried to measure using Google and it looks like under 12m or 35ft

Edited by Mike Todd
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1 hour ago, Mike Todd said:

We have never arrived at either of the diamond locks when there has been a boat suitable for sharing - we are 60'. I cannot recall what the max length is in the 'wings' but it is much shorter than folk imagine.

 

Just tried to measure using Google and it looks like under 12m or 35ft

I remember sharing that lock with a longer boat, which went in the middle. We're 45 feet long.

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