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King's Norton stop lock


magpie patrick

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A brief stop at King's Norton today,  by road, afforded ten minutes examining the now level lock. I've been through it a few times, but not really taken in the detail. It is mostly under a bridge, which itself seems to mark a change in road name from Lifford Lane to Broad Meadow Lane. 

 

I noticed the guillotine gates lean backwards slightly, by design. The bridge masks the fact the lean in opposite directions. Both lean into the lock. I would imagine a guillotine gate might make a slightly more effective seal if leaning backwards a little, as if the head of water were pushing it over. Does this feature suggest they expected the head to be in either direction?

 

I also noticed what looked like ground paddle culvert entrances. One at the Birmingham end inside the lock on the towpath side, and two at the Stratford end, one inside the lock and one outside, but on opposite sides so clearly not two ends of the same culvert - and anyway, why would a ground paddle culvert show above the water?

 

Is much known about the construction of this lock?

 

A couple of pictures below

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5 minutes ago, magpie patrick said:

 

I also noticed what looked like ground paddle culvert entrances. One at the Birmingham end inside the lock on the towpath side, and two at the Stratford end, one inside the lock and one outside, but on opposite sides so clearly not two ends of the same culvert - and anyway, why would a ground paddle culvert show above the water?

 

Why would it need ground paddles at all? You can fill or empty the lock simply by lifting the relevant guillotine at few centimetres.

 

MP.

 

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1 hour ago, MoominPapa said:

Why would it need ground paddles at all? You can fill or empty the lock simply by lifting the relevant guillotine at few centimetres.

 

MP.

 

.....and getting the cill full of rubbish, branches as the water rushes through the narrow gap so it doesnt seal again when lowered.........

 

 

 

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3 minutes ago, matty40s said:

.....and getting the cill full of rubbish, branches as the water rushes through the narrow gap so it doesnt seal again when lowered.........

 

I've never experienced that on the Nene or the Ouse which use the guillotine to empty (Nene) or fill (Ouse) the lock.

 

MP.

 

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14 minutes ago, MoominPapa said:

I've never experienced that on the Nene or the Ouse which use the guillotine to empty (Nene) or fill (Ouse) the lock.

 

MP.

 

It might well work on rivers, but not canals....or dry docks.

We have a guillotine gate but use a sliding paddle to fill the dock. Lifting the gate results in several inches of silt, debris and other matter when we drain it again, which has to be brushed and shovelled out.....if we manage to seal the gate.

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2 hours ago, matty40s said:

It might well work on rivers, but not canals....or dry docks.

We have a guillotine gate but use a sliding paddle to fill the dock. Lifting the gate results in several inches of silt, debris and other matter when we drain it again, which has to be brushed and shovelled out.....if we manage to seal the gate.

Back in the day... I passed through Thurlwood Steel Lock a few times and, like most (of the few) people who passed through that lock, I cracked the gate rather than using the (horrible, heavy, slow) paddles. Worked fine, never heard of the gates getting "stuff" jammed.

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I think frequency of use plus head of water will influence whether guillotine gates get stuff stuck on the cill, if the gate is used frequently and the head large it is quite unlikely. Also the Nene gates are pushed down by the mechanism whereas the ones at Kings Norton drop under their own weight (which is probably rather less anyway) meaning the King's Norton ones will more readily get stuck. 

 

However the holes in the photos don't really work as ground paddles unless there was once another end to them, now blocked, which is why I'm asking. If they were obviously ground paddle culverts that would be the end of the story. 

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Just to add - until the Nene/Ouse thing guillotine gates often seem to have had paddles - Shrewsbury Canal for example. I've not seen guillotine gates  lean though, like these do. 

 

Question really then is why do the gates lean? Why do they lean in opposite directions, and what are the holes for if not for paddles? 

 

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The gates lean so that the weight of the gate assists with getting a seal  along the edges. Particularly at low head differences that are likely in a stop lock.

The Ham Baker paddles on the GU new locks also lean off the vertical for, I  think, the same reason.

At KN there is also some counterbalance, but I have no idea what sort of inbalanced mass was wanted for best seal and achievable lift.  If there was much unbalanced mass and a good 

head difference ground paddles might be needed to get the head down to the point where the gate would move.

 

 

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I have wondered before about why Kings Norton has guillotine gates and had guessed that it was because there was no actual difference in water level between the two sides and there there was no obvious way round to put conventional gates.

 

i had not noticed  the lean of the gates, but if the top leans in at both ends then that also suggests no real difference in levels and the slight difference would always act against one end of the lock.

 

 

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1 hour ago, john6767 said:

I have wondered before about why Kings Norton has guillotine gates and had guessed that it was because there was no actual difference in water level between the two sides and there there was no obvious way round to put conventional gates.

 

i had not noticed  the lean of the gates, but if the top leans in at both ends then that also suggests no real difference in levels and the slight difference would always act against one end of the lock.

 

 

I think KN was intended to cope with either canal being the higher.  To ensure one gate is always optimally leaning they have to lean in opposite directions.

A good seal either way is important, not to prevent the lock emptying but to prevent a long period of slow but continuous flow from the higher canal to the lower  which would negate the purpose of the stop lock.

 

Stop locks with a one way bias like Hawkesbury are OK with a normal gate. Other near level, fall either way locks like Hall Green or at Marston Jabbets need two sets of gates.  OK if you have the spare cash and don't mind the extra upkeep costs.

 

N

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There was a suggestion that the guillotine gates were built from parts of the Tardebigge lift, though it is difficult to see what could have been reused from this illustration. One possible use for the culverts could be to keep a supply going to the Stratford on a Sunday, when the stoplock could have been closed to boats.

1.jpg

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That is a nice copy of the lift at Tardebigge, but I find it difficult to agree with that possibility especially as I have written about Lifford Stop and the Stop at Kingswood.

 

There is a common element that links the three cast iron aqueducts, the split bridges and the Lifford Lift Bridge and that is the Lionel Street Foundry of William Whitmore. For Lifford lock the lock gates were at first mitred to allow the passage of barges to Hockley Heath, although only one is credited with that journey. The land width at Lifford remains barge wide. The replacement stop was made in 1814. See page 114 of Birmingham Canals 

 

 

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