Closing lock gates

[ditchcrawler]

Agree 100%.

 

Greenie awarded.

Way Hay

[bizzard]

Not much chance of leaving the pawl off on most Stort paddle gear, you have to keep em held up when lowering paddles.

[Hairy-Neil]

 

 

The reason for leaving guillotine gates open is so that the lock can at as an additional weir by water flowing over the gates. If you close a guillotine gate, water can't flow over the top. Better to leave it open so water can flow under it.

 

Hey?

 

Surely if that was the case, once the lock had filled the water flowing over the top gates it would also weir over the guillotine....

 

The way a guillotine is used as an additional weir is by chaining the mitre gates open and winding up the guillotine...

[Keeping Up]

Hey?

 

Surely if that was the case, once the lock had filled the water flowing over the top gates it would also weir over the guillotine....

 

The way a guillotine is used as an additional weir is by chaining the mitre gates open and winding up the guillotine...

 

 

AIUI under normal condirtions the top gates of Nene locks are designed to act as weirs; in some cases when the river is low they seem to be the primary weir with no water flowing over the actual weir until the river has risen by quite a few inches. In order for that to work properly the guillotine must be left up. It is only under flood conditions that the top (mitre) gates are chained back - by first closing the guillotine, then opening the gates, then opening the guillotine again - so that a massively increased flow is achieved.

[FadeToScarlet]

Hey?

 

Surely if that was the case, once the lock had filled the water flowing over the top gates it would also weir over the guillotine....

 

The way a guillotine is used as an additional weir is by chaining the mitre gates open and winding up the guillotine...

 

No, the top of the guillotine is about 4-6" higher (on the Nene where this is normal) than the top of the top gates which are usually 'pointing doors' as the EA calls them, so that the lock makes a level with the upstream reach.

 

It's the vee gates at the top that have the water pouring over and which act as a weir under normal conditions.

 

You are right. Though that they can reverse the lock and use the guillotine as a sluice gate by chaining back the top gates and opening the guillotine up, to discharge flood water.

[furnessvale]

AIUI under normal condirtions the top gates of Nene locks are designed to act as weirs; in some cases when the river is low they seem to be the primary weir with no water flowing over the actual weir until the river has risen by quite a few inches. In order for that to work properly the guillotine must be left up. It is only under flood conditions that the top (mitre) gates are chained back - by first closing the guillotine, then opening the gates, then opening the guillotine again - so that a massively increased flow is achieved.

 

I have not been down the Nene so perhaps I am missing something. Why is the TOP of the guillotine not set, say, 2" lower than the top of the mitre gates? Water spilling over the mitres will first fill the lock and then spill over the guillotine in the closed position.

 

Leaving any gate open with flowing water, except if essential in floods, is inviting obstruction of the cill with debris.

 

George ex nb Alton retired

[ditchcrawler]

They are talking about making all the none motorised ones into pointy gates at each end. I am not sure how that will effect flood conditions.

[Keeping Up]

I have not been down the Nene so perhaps I am missing something. Why is the TOP of the guillotine not set, say, 2" lower than the top of the mitre gates? Water spilling over the mitres will first fill the lock and then spill over the guillotine in the closed position.

 

Leaving any gate open with flowing water, except if essential in floods, is inviting obstruction of the cill with debris.

 

George ex nb Alton retired

 

If they did that it could become impossible to open the top gates when they wanted to "reverse" the lock because there would be a considerable flow over them, whereas with the existing setup when they close the guillotine there would be no flow past the gates once the lock had filled.

[furnessvale]

If they did that it could become impossible to open the top gates when they wanted to "reverse" the lock because there would be a considerable flow over them, whereas with the existing setup when they close the guillotine there would be no flow past the gates once the lock had filled.

Yes I see that. Incidentally, do they have much of a problem with debris on the cill?

 

George ex nb Alton retired

[Doorman]

They are talking about making all the none motorised ones into pointy gates at each end. I am not sure how that will effect flood conditions.

 

Aren't these 'pointy gates' referred to as chevrons?

[IanM]

Aren't these 'pointy gates' referred to as chevrons?

 

Mitre gates.

[fudd]

still the same on Jan 7th, along with all the wide locks further down.

 

edited to add, Nick, if I was following you at a distance along this stretch of the T&M and didn't know about the gates, I would be cursing you as a lazy git who refuses to shut any gates when leaving them....

But I'm sure you would retract that thought as you tried to shut the gates yourself?

Too late. I should have read on.

Edited February 11, 2013 by fudd

[Doorman]

Mitre gates.

 

Cheers Ian,

 

I mitre known someone would know the answer.

[Athy]

A bit late on this one but they are not, and never have been called safety catches.

.

not by you, perhaps; by thousands of other people, yes. I have rarely heard them called anything else, except on this forum. I fully realise that many members of this forum have extensive (often professional) boating experience, and that the worf "pawl" may be the one more often used in the trade.

 

Hi all

 

I totally agree with Speedwheel on this. I've always known them as pawls and flip them back when lowering a paddle so that there's no risk of a partially closed one,

Fair enough. Then, when the paddle is fully lowered, put the safety catch on to leave the mechanism in a safe condition for the next user, who may be inexperienced. It's one fewer thing to go wrong, which can only be a good thing.

[Keeping Up]

not by you, perhaps; by thousands of other people, yes. I have rarely heard them called anything else, except on this forum. I fully realise that many members of this forum have extensive (often professional) boating experience, and that the worf "pawl" may be the one more often used in the trade.

I'm amazed if this is true. I have heard thousands of people refer to them as "catches" or "ratchets" bot literally just a handful who refer to them as "safety catches". They never have been, and never will be, anything to do with safety; Gawd help us if the H&S brigade get their teeth into them.

 

 

Fair enough. Then, when the paddle is fully lowered, put the safety catch on to leave the mechanism in a safe condition for the next user, who may be inexperienced. It's one fewer thing to go wrong, which can only be a good thing.

No it is not a good thing because then people get into the habit of assuming that they don't need to check whether or not they engage properly, as they wind them up.

[matty40s]

I think it's time to name and shame.

 

This boat left the gates open on Saturday on the Avon

 

 

 

 

 

 

and look how much water they have let down into the next pound.

 

[Athy]

I have heard thousands of people refer to them as "catches" or "ratchets". They never have been, and never will be, anything to do with safety;

Yes, short for "safety catches".

As for their being nothing to do with safety, I assume you're joking. Why, then, are they there? To assist in the safe operation of the mechanism, of course. Without them, it would be unsafe to use because it would keep slipping down.

 

 

Nice one, Matty!

[furnessvale]

I think it's time to name and shame.

 

This boat left the gates open on Saturday on the Avon

 

 

 

 

 

 

and look how much water they have let down into the next pound.

 

 

If leaving the top gates open has dropped that much water they must have left the bottom paddles up as well! Maybe the pawls had been put on partially lowered bottom paddles:-)

 

Not knowing the pound in question, the top photo tells me it is very low. Were they perhaps dropping water to fill a very low pound and got carried away?

 

George ex nb Alton retired

[Nickhlx]

If leaving the top gates open has dropped that much water they must have left the bottom paddles up as well! Maybe the pawls had been put on partially lowered bottom paddles:-)

 

Not knowing the pound in question, the top photo tells me it is very low. Were they perhaps dropping water to fill a very low pound and got carried away?

 

George ex nb Alton retired

 

The upper pound still looks very full, so that must have had a good source too !

 

Nick

[FadeToScarlet]

Mitre gates.

 

Utterly anal point of order..... There are regional variations on the terminology used.

 

On the canals they're often called mitre gates, although there may be a variation oop Norf I've not heard of.

 

On the Nene and the Great Ouse they're referred to as pointing doors or vee doors. On the Thames, I think they're vee gates.

 

There's also different terminology for paddle gear. On the Nene and Ouse, they're known as Slackers, on the Middle Level they're known as Penstocks. On the Thames I think they're called sluices.

 

All good to know so you can be very pedantic on the Internet!

[Timleech]

Yes, short for "safety catches".

As for their being nothing to do with safety, I assume you're joking. Why, then, are they there? To assist in the safe operation of the mechanism, of course. Without them, it would be unsafe to use because it would keep slipping down.

 

 

Nice one, Matty!

 

No, not unsafe, impractical. Major difference.

 

Tim

[nicknorman]

Yes, short for "safety catches".

As for their being nothing to do with safety, I assume you're joking. Why, then, are they there? To assist in the safe operation of the mechanism, of course. Without them, it would be unsafe to use because it would keep slipping down.

 

 

Nice one, Matty!

Anyone who thinks they were called safety catches when they were invented in the 19th and possibly 18th century must be crackers. There was no such thing as safety in those days!

[furnessvale]

The upper pound still looks very full, so that must have had a good source too !

 

Nick

 

? I cannot see the pound that fed this one in either photo.

 

George ex nb Alton retired

[nicknorman]

? I cannot see the pound that fed this one in either photo.

 

George ex nb Alton retired

Hint: Its the same pound in both photos and its a joke!

[furnessvale]

Hint: Its the same pound in both photos and its a joke!

 

Sorry, the joke went completely over my head and still does. I know it is the same pound and I thought the OP was saying the offending boat left the next set of gates open thus flooding this one.(before and after photos)

 

Still, it does demonstrate what can happen when you put the pawls back on partially lifted paddles.

 

George ex nb Alton retired