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What chance do lock gates have?


haggis

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16 minutes ago, Captain Pegg said:

Am I missing something in relation to the story about the boat stuck between the top gates; why not just close the bottom gates to extricate it?

 

Not sure I believe this really was a thing.

Maybe that was where his butty was

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15 minutes ago, Jen-in-Wellies said:

I am just reporting what I vaguely remember reading. Something that would do it is if a motor got stuck in the top gates, then the bottom ones slammed shut on a towed butty, giving both gates open and miles of pound putting pressure on them till the levels equalised.

Yes, I reckoned 140 foot of boat. 

 

There is a vaguely similar issue with Grand Sluice at Boston, which means CRT do not operate the lock on very high tides. As the lock is so short. most  transits are for the few minutes when the tide makes a level (about 2 hrs before and 2 hrs after HW) and all the gates can be opened. There is a (fairly theoretical) risk that the gates could swing closed and close a trap a boat, which would then be squashed as the tide continued to do its thing. I was glad it didn't happen to me last year, as the last of 11 boats to go through that day.  You can just see the see doors (the third set) opening in this photo. 

dsc_4364.jpg 

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I struggle with the idea a motor and butty could execute such a trick. Where exactly does the 25 tonnes of laden butty go while the motor forces its way through the top gates?

 

Is it braked by the closing bottom gates? ?

 

My fiver says it never happened.

 

ETA - I guess it would be braked by the influx of water but it’s still something of a trick that I struggle to see that even if possible would save time on just operating the lock normally. Sounds like a legend that’s grown out of perhaps an idea or a one off attempt.

Edited by Captain Pegg
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2 minutes ago, Captain Pegg said:

I struggle with the idea a motor and butty could execute such a trick.

 

In fact, if the motor and/or the butty were stuck in the gates, the angle of the gates must be so shallow that the water pressure wouldn't be forcing them closed.  The gates have to be nearly completely open for the boat to fit!

 

So opening the top gates another half an inch would be enough to get the motor out, or conversely opening the tail gate(s) half an inch would be enough to drop the butty out.

 

One of those urban leg-ends I reckon.

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1 minute ago, TheBiscuits said:

 

In fact, if the motor and/or the butty were stuck in the gates, the angle of the gates must be so shallow that the water pressure wouldn't be forcing them closed.  The gates have to be nearly completely open for the boat to fit!

 

So opening the top gates another half an inch would be enough to get the motor out, or conversely opening the tail gate(s) half an inch would be enough to drop the butty out.

 

One of those urban leg-ends I reckon.

I agree it’s probably legend but I think the counter argument was that the motor was stuck in the top gates and the butty stuck in the bottom gates.
 

Not that the flow through the top gates would cause the bottom gates to close in any case.

 

 

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1 hour ago, Keeping Up said:

 

 

Of course that is only a temporary lock. It was installed when the canal was built built to temporarily raise the water level to clear a strip of very hard rock found just near there. The intention was to come back when the canal was finished, and blast it away before removing the lock, but they never got round to doing so. I don't think CRT are planning to do it this winter either!

I heard it was a surveying error, they started digging the pound from both ends and when they met, oops.

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37 minutes ago, TheBiscuits said:

 

In fact, if the motor and/or the butty were stuck in the gates, the angle of the gates must be so shallow that the water pressure wouldn't be forcing them closed.  The gates have to be nearly completely open for the boat to fit!

 

So opening the top gates another half an inch would be enough to get the motor out, or conversely opening the tail gate(s) half an inch would be enough to drop the butty out.

 

One of those urban leg-ends I reckon.

Its a 14 foot wide lock with a 7 foot narrowboat, if the butty was on cross straps it would effectively be a 140 foot long boat only 7 foot wide

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4 minutes ago, ditchcrawler said:

Its a 14 foot wide lock with a 7 foot narrowboat, if the butty was on cross straps it would effectively be a 140 foot long boat only 7 foot wide

 

Oops missed that bit!

 

That changes the physics compared to a narrow lock, and changes the angle of the gates so it would be harder to open the top gates.  The flow underneath a working boat in a lock with a rise of a foot with the head gates partially closed should still have been low enough to allow the hypothetical butty to be freed by opening the tailgates and dropping it back out of the lock though. 

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So the motor exits the lock and the gates close against the fenders, but don’t trap them or rip them off?

 

And the fenders also successfully prevent the rudder getting trapped?

 

Then the gates close against the cross straps, but don’t trap them?

 

(It would be easier to use a line which probably could be lifted above the closing gates having gone slack and in reality by far and away the majority of pairs would have been loaded going uphill here and on a line in a any case).

 

Then the butty passes through the gates that are under pressure but the gates still manage to pass over the anser pins without damaging them or ripping them off.

 

Next comes the tunnel hooks and they don’t get damaged either.

 

Then somehow the helm manages to pass through without getting trapped or damaged.

 

It’s not going to happen is it?

Edited by Captain Pegg
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9 hours ago, Phoenix_V said:

Old boaters trick if a single gate won't open because the lock is emptying faster than it fills, nudge the gate a few inches open and drop a block of wood between end of gate and lock wall to increase inflow.

On the Coventry known as an "Atherstone Wedge."

Mr. Fuller demonstrating the art going up as the Atherstone flight are notorious for being slow fillers.

 

Atherstone Wedge.JPG

Edited by Ray T
Had brain fade and got my canals mixed up, Doh!
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2 hours ago, Jen-in-Wellies said:

I am just reporting what I vaguely remember reading. Something that would do it is if a motor got stuck in the top gates, then the bottom ones slammed shut on a towed butty, giving both gates open and miles of pound putting pressure on them till the levels equalised.

How does the length of the upper pound affect the pressure?

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49 minutes ago, Mike Todd said:

How does the length of the upper pound affect the pressure?

The pressure would be there a lot longer than it would on a pound 100 yards long, with that the pressure would be gone in minutes and the gates operated, not hours

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1 hour ago, Ray T said:

On the Trent & Mersey Known as an "Atherstone Wedge."

Mr. Fuller demonstrating the art going up as the Atherstone flight are notorious for being slow fillers.

 

Atherstone Wedge.JPG

Well yes. Without admitting anything re times or dates, such equipment was at one time present and in service on our old motor.

It is no longer the case.

Made double working with the butty so much quicker.

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4 hours ago, Ray T said:

On the Trent & Mersey Known as an "Atherstone Wedge."

Mr. Fuller demonstrating the art going up as the Atherstone flight are notorious for being slow fillers.

 

Atherstone Wedge.JPG

0

A rare brain fart Ray?

 

Atherstone is on the Coventry (but I know that you knew that).

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24 minutes ago, cuthound said:

0

A rare brain fart Ray?

 

Atherstone is on the Coventry (but I know that you knew that).

Doh, yes, thank you, I must be going a bit "sealion."

 

Have corrected my post, thank you.

Edited by Ray T
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6 hours ago, roland elsdon said:

Well yes. Without admitting anything re times or dates, such equipment was at one time present and in service on our old motor.

It is no longer the case.

Made double working with the butty so much quicker.

 

I guess in the days of need for speed and getting stuff delivered it (using a wedge) would have been the done thing. 

 

Would they have just kept knocking with the motor until a gap  allowed a wedge to be put in? And then would they knock again so it can be driven further?


How would it have been done?

 

If done today it’d probably be done for that last couple of inches that won’t fill?

 

But would they have smashed it at a foot or more? 

 

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5 minutes ago, Goliath said:

 

I guess in the days of need for speed and getting stuff delivered it (using a wedge) would have been the done thing. 

 

Would they have just kept knocking with the motor until a gap  allowed a wedge to be put in? And then would they knock again so it can be driven further?


How would it have been done?

 

If done today it’d probably be done for that last couple of inches that won’t fill?

 

But would they have smashed it at a foot or more? 

 

It probably depended upon the strength of the horse.

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5 minutes ago, Goliath said:

Would they have just kept knocking with the motor until a gap  allowed a wedge to be put in? And then would they knock again so it can be driven further?


How would it have been done?

 

If done today it’d probably be done for that last couple of inches that won’t fill?

 

I am not sure the wedge was used all that much - but in principle, a run was taken at the top gate in an empty lock.  You would need to be confident that the stem would hit the gate(s) before the cill

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7 minutes ago, Captain Pegg said:

It probably depended upon the strength of the horse.

I thought it was a motor thing. 
When there’s enough water in the lock to hit your boat at the top gate. 
 

7 minutes ago, Tacet said:

I am not sure the wedge was used all that much - but in principle, a run was taken at the top gate in an empty lock.  You would need to be confident that the stem would hit the gate(s) before the cill

So hit the gate as early as possible?

 

 

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44 minutes ago, Goliath said:

I thought it was a motor thing. 
When there’s enough water in the lock to hit your boat at the top gate. 

 

I'm not sure a 71'6" boat gets too much of a run up in a 72' lock ...

 

3-4 feet?  Maybe 7-8 feet if it's a single tailgate.

 

Admittedly a laden boat can deliver a fair bit of momentum over that distance.

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54 minutes ago, Goliath said:

 

Would they have just kept knocking with the motor until a gap  allowed a wedge to be put in? And then would they knock again so it can be driven further?


How would it have been done?

 

Basically, it wasnt needed in the olden days as the top gates had paddles fitted. Once these were removed on gate replacement economies,  the boaters invented the wedge to assist upwards speed.

The boat comes in, bottom gates shut, as top ground paddles opened full throttle,  a full length boat will go back and then come forward, usually high enough to jolt the top gate(mine does), at the point of jolt a working boatman would drop his Trent and Mersey wedge (slightly different angle to the Atherstone one)? in and the lock would fill at proper speed,  not cook breakfast in a lock speed

 

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1 minute ago, matty40s said:

Basically, it wasnt needed in the olden days as the top gates had paddles fitted. Once these were removed on gate replacement economies,  the boaters invented the wedge to assist upwards speed.

The boat comes in, bottom gates shut, as top ground paddles opened full throttle,  a full length boat will go back and then come forward, usually high enough to jolt the top gate(mine does), at the point of jolt a working boatman would drop his Trent and Mersey wedge (slightly different angle to the Atherstone one)? in and the lock would fill at proper speed,  not cook breakfast in a lock speed

 

That makes a lot of sense ?


 

 

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Modern variant ( well 30 years ago plus) was put motor at back of lock) put in idle/ gear hop up lockside. As motor nudged gate drop in wedge. Only used for last 18 inches or so .

Gave time to  drop lock and assist in bow hauling butty between pounds

Used on lapworth as well, but they fill fast apart from one with hydraulics. 

Last seen in 2000 sold with the boat, when we went to converted boat. Probably thrown out.( whats that big wedge for?)

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