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Staircase locks and best use of water


Col_T

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6 minutes ago, TheBiscuits said:

Up first is one less fill of the top chamber, but whether it saves any water depends on the direction of the third boat when it turns up.

 

Why?

 

Whichever end a boat next arrives at, correct operation of a staircase the lock needs to be put back into the state of top lock full, and bottom lock empty, before they start their transit.

So I think the direction of arrival of boat number 3 is irrelevant.

 

In fact it goes further than that.  For even the two boats being discussed, the locks must be put back in the state they were before the first boat goes through, before the second one does.

Therefore I believe "sharpness" is spot on that it makes no difference. 

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Two lock staircase wouldn't be set like that, surely, unless the bottom lock leaks like hell. If a boat's gone up, both are full and vice versa. You always have to set one lock, whichever way you're going. So, it would be the boat that got there first and set the locks! 

Different with wide locks as boats can pass in different directions. 

Edited by Arthur Marshall
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13 minutes ago, Arthur Marshall said:

Two lock staircase wouldn't be set like that, surely, unless the bottom lock leaks like hell.

Yes, this as well!

As Arthur said you would only find a 2 lock staircase seat as described if someone had set it that way, or something was leaking badly.  If the last boat through has just driven away, whichever way it was heading, the locks would not be in the state described.

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Irrespective of if you are going up or down with a two lock staircase, top full bottom empty is how you start, so it is set for both of them, so it does not matter who goes first.  For the next boat you need to waste a lock of water to set back to the starting state irrespective of the direction.

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The staircase at Bunbury has chambers of different sizes, and once the bottom lock fills the excess water from the top lock goes through a whacking great slot into the basin. So I've always wondered if there was any point in draining the bottom lock - why not just empty the top lock as you go down through the slot? Would that not save a lockful? 

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7 minutes ago, Arthur Marshall said:

The staircase at Bunbury has chambers of different sizes, and once the bottom lock fills the excess water from the top lock goes through a whacking great slot into the basin. So I've always wondered if there was any point in draining the bottom lock - why not just empty the top lock as you go down through the slot? Would that not save a lockful? 

He said a norrow staircase, with a wide like Bunbury or Bascote you can shuffle.  The only narrow staircase of two I can think of is Brades, which also has the drain so you could if you wanted, in theory at least, drain the top into a full lower lock.

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10 minutes ago, Arthur Marshall said:

The staircase at Bunbury has chambers of different sizes, and once the bottom lock fills the excess water from the top lock goes through a whacking great slot into the basin. So I've always wondered if there was any point in draining the bottom lock - why not just empty the top lock as you go down through the slot? Would that not save a lockful? 

Great minds think alike, a bit like Bedford Street on the Caldon

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There is a huge difference between how staircases are supposed to work and how they do work, because leakage and small fluctuations in the upper and lower pounds make a difference. Leaky upper gates make it look like the upper chamber has more water in it for example. 

 

Bedford Street are distinctly uneven, with others even six inches too much water in the lower chamber looks impressive. The wise engineer always put an overflow in the lower chambers of staircases.

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9 hours ago, David Mack said:

 

 

Also Botterham and the new pair on the Droitwich.

 

9 hours ago, john6767 said:

Thanks, I don’t know the Caldon, but I should have thought of the one on Droitwich.

Botterham is on the Staffs and Worcs.

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2 hours ago, magpie patrick said:

There is a huge difference between how staircases are supposed to work and how they do work, because leakage and small fluctuations in the upper and lower pounds make a difference. Leaky upper gates make it look like the upper chamber has more water in it for example. 

 

Very true. So, "best use of water" is to be able to manage this water leak smoothly without needing to add excess water, or risking grounding (eg if the intermediate level becomes too low). The best way to do this is to not-quite-empty the lower lock, if descending. Then if/when it achieves the intermediate level it either overflows a small amount of excess water (this is water that was saved by not fully emptying it...) or its at the right level, or it might be slightly down but the boat is shallow drafted enough to make it over the upper lock's cill.

 

The worst thing you can do is delay, or do the lock really slowly, water will just leak and leak and you'll end up chasing your tail adding more and more, as you do so it gets further and further away from the ideal water consumption. If you need to add extra water due to leaks (and there is no option but to, going up) it needs to be done quickly and accurately.

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