diamond locks

[Murflynn]

Tim and Pru were on the Oxford the other day (on TV) and claimed there were only 2 diamond locks 'on the system'. They proceeded to pass through both of them.

 

What about the Stratford Avon where there is one (a true diamond, unlike the ones on the Oxford?).

 

How many are there altogether?

 

 

[Scholar Gypsy]

One could argue that the test is whether the lock chamber is wider than the entrances at each end.

 

There are several that would qualify on the Bedford Ouse - here is my favourite, at Hemingford

 

Edited February 20, 2016 by Scholar Gypsy

[OldGoat]

Wyre Piddle on the Warwickshire Avon is a diamond shaped lock??

[Mac of Cygnet]

I vaguely remember going through an oval lock somewhere, but can't for the life of me remember where it was. Any ideas? (it may have been in France).

[colinwilks]

I vaguely remember going through an oval lock somewhere, but can't for the life of me remember where it was. Any ideas? (it may have been in France).

You may be thinking of the locks on the Canal du Midi at Béziers.

 

We came across them by chance when driving. Worth a visit and I think they are a world heritage site.

[magpie patrick]

One could argue that the test is whether the lock chamber is wider than the entrances at each end.

 

There are several that would qualify on the Bedford Ouse - here is my favourite, at Hemingford

 

 

The EA refer to those as pregnant bays - but yes, they are wider in the middle than at the entrance

 

Tim and Pru were on the Oxford the other day (on TV) and claimed there were only 2 diamond locks 'on the system'. They proceeded to pass through both of them.

 

What about the Stratford Avon where there is one (a true diamond, unlike the ones on the Oxford?).

 

How many are there altogether?

 

 

 

Wyre piddle is the only true diamon shape left on the Avon, although some of the others are slightly irregular. Sone on the upper Avon were round in times past. the site of the old chamber at Luddington stands beside the new one

 

 

Then there is this oddity at Cefn in South Wales...

[Murflynn]

Wyre Piddle on the Warwickshire Avon is a diamond shaped lock??

Yes. A lovely spot with free mooring on the lock island but beware the dinner cruise barge that comes through at about midnight (well, it did the night I was tied up there.

If you are on a conventional yogurt pot it is almost impossible to get on and off the boat once in the lock.

Only the ends of the boat touch, but for me the only safe access is amidships.

[Scholar Gypsy]

.. and there are some on the Thames that are wider than the entrance - I think Sandford and possibly Bell Weir?

[Pluto]

I have come across numerous variations around Europe, with different chamber shapes and position of gates. This is perhaps my favourite, at Montreuil-Bellay on the Thouet, which runs south from the Loire. Originally a flash lock, a chamber and lower gate was added later. The navigation closed around the 1930s.

[sharpness]

Tim and Pru were on the Oxford the other day (on TV) and claimed there were only 2 diamond locks 'on the system'. They proceeded to pass through both of them.

 

What about the Stratford Avon where there is one (a true diamond, unlike the ones on the Oxford?).

 

How many are there altogether?

 

 

I noticed that too but I think, but not 100% sure, he said on "the canal system" all those mentioned above are river locks.

 

Steve

[Theo]

I could never understand why the diamond locks on the Oxford are so stupidly shaped. Talk about making it inconvenient for a working boat or a 60 footer for that matter. Just the same effect could have been achieved by keepin the look rectangular and working boat length but wider to give it greater volume.

 

N

[Dharl]

However last year we managed to get three boats through the diamond locks on the Oxford at the same, self on. 58 and there was two smaller boats as well. Had tried to get us and a 70ft through at same time, was close but didn't quiet work!!

[Scholar Gypsy]

I could never understand why the diamond locks on the Oxford are so stupidly shaped. Talk about making it inconvenient for a working boat or a 60 footer for that matter. Just the same effect could have been achieved by keepin the look rectangular and working boat length but wider to give it greater volume.

 

N

 

But - assuming they don't want to go to the expense of wider gates, that creates a couple of right angle corners (as on the Ouse locks) which would be harder to build I think before the days of concrete etc.

 

What I don't really understand is why they didn't just build an ordinary lock, with a small sluice to run water around it to supply the deeper locks further down the canal.

[john6767]

However last year we managed to get three boats through the diamond locks on the Oxford at the same, self on. 58 and there was two smaller boats as well. Had tried to get us and a 70ft through at same time, was close but didn't quiet work!!

I assumed that this was exactly the reason why the locks are the shape that they are, to stop more than 1 (full length) boat using the lock at the same time. By having more than 1 boat in the lock you have defeated to whole objective of letting more water down the shallow lock to match the capacity of the following deeper locks.

 

I guess an alternative shape would be rectangular with pillars to stop the sides being used for boats.

[NickF]

However last year we managed to get three boats through the diamond locks on the Oxford at the same, self on. 58 and there was two smaller boats as well. Had tried to get us and a 70ft through at same time, was close but didn't quiet work!!

 

I have shared those locks before but it actually defeats the object which is to let more water into the canal below

[Guest]

One could argue that the test is whether the lock chamber is wider than the entrances at each end.

 

There are several that would qualify on the Bedford Ouse - here is my favourite, at Hemingford

 

 

Going off topic for a second - How much of the waterways in that neck of the woods are as pretty as that? I had somehow imagined that area as pretty flat and featureless but it looks as if it could be worth considering as an area for a hire holiday.

[gazza]

 

Going off topic for a second - How much of the waterways in that neck of the woods are as pretty as that? I had somehow imagined that area as pretty flat and featureless but it looks as if it could be worth considering as an area for a hire holiday.

Martin, Phil and I have told you before, it's awful, Simon has photo shopped that to make it look pretty......

 

Find out for yourself what a backward and rough area it is here in the fens. http://www.bridgeboatyard.com

 

PS, try and keep your findings a secret....

[Guest]

[Neil Smith]

We use to hire from bridge boat yard 35 years ago, pleased to hear they are still going strong, we loved the fen rivers so bought a 32 foot dawncraft and moored it by an old closed down pub on the way to Denver sluice if I remember correctly.

 

Neil

[gazza]

We use to hire from bridge boat yard 35 years ago, pleased to hear they are still going strong, we loved the fen rivers so bought a 32 foot dawncraft and moored it by an old closed down pub on the way to Denver sluice if I remember correctly.

 

Neil

The Ferry Boat Inn, Southery?

 

http://home.freeuk.com/southerytour/ferry.htm

[Machpoint005]

I have shared those locks before but it actually defeats the object which is to let more water into the canal below

 

Doesn't make any difference in the grand scheme of things. It isn't just one isolated lock!

[magpie patrick]

 

Doesn't make any difference in the grand scheme of things. It isn't just one isolated lock!

 

Took me a while to fathom out your comment

 

Yes it does make a difference - these locks descend from the Cherwell, which breaks the hydrological continuity of the canal

 

If, for example, you have a canal with two deep locks, say ten foot drop, seperated by a shallow lock of say two feet, it doesn't matter. The highest lock will deposit a ten-foot lock volume of water into the canal below, the shallow lock will use two feet of it and eight feet of it will go round the bywash and into the canal below the shallow lock. You then empty the two foot lock, which tops up that which went round the bywash, and the next deep lock has enough water.

 

In this case though, the lock upstream empties into a river, and the water is lost to the river system, at these shallow locks the process starts again so the next lock down has only as much water as goes through the shallow lock, that's why is has been made wider. At Shipton the sums are bout right, but at Aynho the lock is stiill not big enough to carry enough water for the next lock downstream.

 

Although these locks are big, they can only take one 70 foot narrowboat. If three smaller boats share the shallow lock, all three will have to single out for the deep one, which will have to be operated three times, undoing the benefit of the extra volume of water carried by the diamond shape.

 

I think though the CRT have cut slots in the gates so there is always a flow through the locks now

[Scholar Gypsy]

 

Took me a while to fathom out your comment

 

Yes it does make a difference - these locks descend from the Cherwell, which breaks the hydrological continuity of the canal

 

If, for example, you have a canal with two deep locks, say ten foot drop, seperated by a shallow lock of say two feet, it doesn't matter. The highest lock will deposit a ten-foot lock volume of water into the canal below, the shallow lock will use two feet of it and eight feet of it will go round the bywash and into the canal below the shallow lock. You then empty the two foot lock, which tops up that which went round the bywash, and the next deep lock has enough water.

 

In this case though, the lock upstream empties into a river, and the water is lost to the river system, at these shallow locks the process starts again so the next lock down has only as much water as goes through the shallow lock, that's why is has been made wider. At Shipton the sums are bout right, but at Aynho the lock is stiill not big enough to carry enough water for the next lock downstream.

 

Although these locks are big, they can only take one 70 foot narrowboat. If three smaller boats share the shallow lock, all three will have to single out for the deep one, which will have to be operated three times, undoing the benefit of the extra volume of water carried by the diamond shape.

 

I think though the CRT have cut slots in the gates so there is always a flow through the locks now

 

I've found my photo (2013) of the fixed sluice in the upper gate at Aynho (well I assume that is what on the end of this rod!).

 

A further complication is that a decent sized tributary of the Cherwell is intercepted by the canal at Souldern, supplying water to Somerton Deep.

 

[Hawkmoth]

Just slightly off topic, for strange lock shapes try Castleford Lock on the Aire & Calder. It's bent. Watching the gravel barges go though is interesting, they have to turn in the lock.

Bob

[Machpoint005]

 

Took me a while to fathom out your comment

 

Yes it does make a difference - these locks descend from the Cherwell, which breaks the hydrological continuity of the canal<<

 

 

 

>>I think though the CRT have cut slots in the gates so there is always a flow through the locks now

 

Sorry, CBA to explain more fully. But in the grand scheme of things, it seems it doesn't make any difference?