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Bunbury Staircase closed


Dave123

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Saw this photo on Facebook of the middle gates at Bunbury on the lower Shroppie. A mystery as to how the ground paddle has shattered like that? A road vehicle hitting it and the gate hard enough to do that surely wouldn't have been able to drive off?

FB_IMG_1627198725207.jpg

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1 hour ago, Tracy D'arth said:

Beam gone round as the gate went over centre and hit the paddle stand?

The gate in the picture does not seem to be over centre, rather the heel pin has either  failed or the gate has been lifted off it. Either way the gate is pointing uphill like it should.

 

Combined with the damage to the paddle stand my guess is that  a vehicle has bounced off the paddle stand into the end of the beam and wrecked the heel pin.  It would be useful to see whether there is something behind the photographer.

What is the betting CRT put it down to boater misuse, or  vandalism?

N

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20 minutes ago, cuthound said:

One of the vertical planks is missing from the damaged gate, so it could have been a boat strike.

 

I can see how a boat strike could lift the gate and take the collar out but I can't see any way in which the gate could take out the paddle gear and end up in that position given the other gate is still in situ

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Two more pics from Facebook, they don't show anything more which isn't very helpful. It's difficult to beileve a vehicle could do that to the paddle unless it left bits of vheicle behind and bent the balance beam, it's difficult to see how a boat could force the gate into the paddle or if it did how it hit that side of the paddle and then returned to this position. I'm guessing the top lock was not full at the time

bunbury 2.jpg

bunbury 1.jpg

Edited by magpie patrick
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1 minute ago, Dave123 said:

Someone said the paddle may have been damaged already in a separate incident....still odd though

I was wondering that.  Also the stoppage notice does not say anything about the paddle gear, just the gate.  But then they only need to fix the gate to get the lock operating.

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1 hour ago, cuthound said:

One of the vertical planks is missing from the damaged gate, so it could have been a boat strike.

Or the plank was already missing and a boat coming up got its bow hooked under one of the gate horizontals and lifted it out. Boat then scuttled away backwards out of the bottom lock.

Doesn't explain the paddle though.

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There are a couple of messages on FB tonight

 

The update shows the repair is complicated!
27/07/2021 15:44
Our local engineer has been to site and assessed the lock gates. The damage is more significant than first thought. A crane will now be needed to lift and reseat the gate and we will also need to fit a replacement steel plate, which will require installing scaffolding in to the dewatered lock
The jack head has been severed from the impact of the gate and this will need to be replaced.
A further update will be provided Friday 30th July
 
And
 
Just to clarify as a lot of people are making lots of assumptions without knowing the facts:
- I was there when this happened.
- The boat was nowhere near the gate and did not hit it.
- The lock was full when I attempted to open the gate. It jumped up and fell on the lock mechanism and broke it.
- An employee from Anglo Welsh was present when this happened and confirmed that none of us did anything wrong.
- Apparently the lock has been leaking badly recently as confirmed by the someone who lives next to it.
- I can't confirm exactly what went wrong but I would like to state that no one did anything wrong.
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1 hour ago, ditchcrawler said:

There are a couple of messages on FB tonight

 

The update shows the repair is complicated!
27/07/2021 15:44
Our local engineer has been to site and assessed the lock gates. The damage is more significant than first thought. A crane will now be needed to lift and reseat the gate and we will also need to fit a replacement steel plate, which will require installing scaffolding in to the dewatered lock
The jack head has been severed from the impact of the gate and this will need to be replaced.
A further update will be provided Friday 30th July
 
And
 
Just to clarify as a lot of people are making lots of assumptions without knowing the facts:
- I was there when this happened.
- The boat was nowhere near the gate and did not hit it.
- The lock was full when I attempted to open the gate. It jumped up and fell on the lock mechanism and broke it.
- An employee from Anglo Welsh was present when this happened and confirmed that none of us did anything wrong.
- Apparently the lock has been leaking badly recently as confirmed by the someone who lives next to it.
- I can't confirm exactly what went wrong but I would like to state that no one did anything wrong.

 

So they mean the bottom lock was full when they tried to open the gate I assume.

What on earth would cause a gate to jump up like that, shear its collar, swing the wrong way, or fall backwards, so it hits the ground paddle and then bounce back to the position it's currently in - for the balance beam to whack the ground paddle it would have to be swung pretty much the wrong way, or it would have fallen back and hit the paddle and just stopped there.

Edited by StephenA
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Is it saying that a structural failure in the gate that is to blame?  So with the lock full the bottom of the gate became unconstrained, and the water pressure forced the gate up and it came down on the paddle gear?

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3 hours ago, StephenA said:

What on earth would cause a gate to jump up like that, shear its collar,

 

I don't think the collar is sheared. It looks to be intact on the gate. To me it looks as if something has lifted the gate so that the bottom pintle has become disengaged and the collar attached to the gate has lifted off the part attached to the lockside that it bears on.

 

On further reflection this could have happened:

 

The previous boat going up got its stern fender caught under the balance beam as the upper lock neared full. This lifted the gate vertically up a few inches, disengaging the pintle and the collar, but the water pressure from the full lock held the gate against the qoin in the lock wall and the mitre post of the opposite gate. Once the fender was released, the gate slid back down, the pintle re-engaging, but the looser fitting collar is pushed up the heel post and doesn't engage over the corresponding fitting on the lockside. That boat then departed, maybe leaving a top gate open, so the lock remained full.

Next boater comes along from below the lock, empties the bottom lock and takes his boat in, then empties the upper lock into the lower lock in the ordinary way.  As the levels approach equalisation, the weight of the gate is taken entirely on the pintle at the bottom of the heel post, and so there is a higher than normal horizontal force betweeen the tops of the two mitre posts to balance the offset vertical support. As soon as the boater pushes on the balance beam to open the gate, the top of the gate at the mitre post is no longer restrained, and so the mitre end of the gate immediately drops until it hits the lock floor, and this in-plane rotation causes the pintle to jump out of engagement. The gate is now completely unrestrained and so falls into the upper chamber, with the balance beam able to strike the paddle gear. And the poor boater who did this has no idea how it has happened!

 

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

 

I don't think the collar is sheared. It looks to be intact on the gate. To me it looks as if something has lifted the gate so that the bottom pintle has become disengaged and the collar attached to the gate has lifted off the part attached to the lockside that it bears on.

 

On further reflection this could have happened:

 

The previous boat going up got its stern fender caught under the balance beam as the upper lock neared full. This lifted the gate vertically up a few inches, disengaging the pintle and the collar, but the water pressure from the full lock held the gate against the qoin in the lock wall and the mitre post of the opposite gate. Once the fender was released, the gate slid back down, the pintle re-engaging, but the looser fitting collar is pushed up the heel post and doesn't engage over the corresponding fitting on the lockside. That boat then departed, maybe leaving a top gate open, so the lock remained full.

Next boater comes along from below the lock, empties the bottom lock and takes his boat in, then empties the upper lock into the lower lock in the ordinary way.  As the levels approach equalisation, the weight of the gate is taken entirely on the pintle at the bottom of the heel post, and so there is a higher than normal horizontal force betweeen the tops of the two mitre posts to balance the offset vertical support. As soon as the boater pushes on the balance beam to open the gate, the top of the gate at the mitre post is no longer restrained, and so the mitre end of the gate immediately drops until it hits the lock floor, and this in-plane rotation causes the pintle to jump out of engagement. The gate is now completely unrestrained and so falls into the upper chamber, with the balance beam able to strike the paddle gear. And the poor boater who did this has no idea how it has happened!

 

 

I'd missed that the collar is the reverse in that its fixed to the gate and slips round a ring on the lock side.

 

But I still can't see how the outer edge of the paddle gear has been smashed - as the missing section seems to be significantly above the balance beam (even if the gate was upright) which is I assume now leaning against the ground paddle.  Or maybe its just the angles of the photos.  We did Bunbury last year but it was such a farce that I've blanked it from my memory.

 

Edited by StephenA
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On 27/07/2021 at 22:51, David Mack said:

 

I don't think the collar is sheared. It looks to be intact on the gate. To me it looks as if something has lifted the gate so that the bottom pintle has become disengaged and the collar attached to the gate has lifted off the part attached to the lockside that it bears on.

 

On further reflection this could have happened:

 

The previous boat going up got its stern fender caught under the balance beam as the upper lock neared full. This lifted the gate vertically up a few inches, disengaging the pintle and the collar, but the water pressure from the full lock held the gate against the qoin in the lock wall and the mitre post of the opposite gate. Once the fender was released, the gate slid back down, the pintle re-engaging, but the looser fitting collar is pushed up the heel post and doesn't engage over the corresponding fitting on the lockside. That boat then departed, maybe leaving a top gate open, so the lock remained full.

Next boater comes along from below the lock, empties the bottom lock and takes his boat in, then empties the upper lock into the lower lock in the ordinary way.  As the levels approach equalisation, the weight of the gate is taken entirely on the pintle at the bottom of the heel post, and so there is a higher than normal horizontal force between the tops of the two mitre posts to balance the offset vertical support. As soon as the boater pushes on the balance beam to open the gate, the top of the gate at the mitre post is no longer restrained, and so the mitre end of the gate immediately drops until it hits the lock floor, and this in-plane rotation causes the pintle to jump out of engagement. The gate is now completely unrestrained and so falls into the upper chamber, with the balance beam able to strike the paddle gear. And the poor boater who did this has no idea how it has happened!

 

 

We might never know the cause, but while this seems as logical as any other, it appears unlikely to me that the buoyancy of a boat would be able to lift the gate with very much water pressure against it and I cant quite get my head round where what would be at various levels of what, which obviously also varies depending how exactly the lock is operated.

 

There are some areas on the staircase where you can get a vehicle onto the beams/paddle gear with easy, however I would suggest in the case of this one even without the confirmation it wasn't the case, thats whats actually happened in the gate landed on the paddle gear. I expect there are reasonable low grade castings, and actually a lot less strong than there appear.

 

 

Daniel

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Good news, looks like it's open again. Thought it might take longer than that from the photos.

 

Notice Update: 30th July 21

Navigation: Open, Towpath: Open

Shropshire Union Canal
Location: Lock 14, Bunbury Lower Lock, Shropshire Union Canal
Starts At: Lock 14, Bunbury Lower Lock
Ends At: Lock 15, Bunbury Upper Lock
Up Stream Winding Hole: 350 metres South of Lock 15, Bunbury Upper Lock
Down Stream Winding Hole: 120 metres North of Lock 14 Bunbury Lower Lock


 

Update on 30/07/2021:

We are pleased to advise navigation has resumed at Lock 14, Bunbury Lower Lock on the Shropshire Union Canal following a successful repair to the lock gates.

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