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Broken paddle...


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On 15/12/2017 at 22:24, system 4-50 said:

Before doing any trials it is necessary to define what you mean by a lock being "full".  The filling process slows down exponentially (ish) so that in fact a lock is never totally full. It is necessary to define full arbitrarily as when the fill rate has dropped to a certain level, say 1% of the total capacity of the lock when it was new. (Has this thread been sitting too close to another thread?)

 

Well at least if you don't fill a lock to 100%, it doesn't lose capacity from sulphation.

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4 hours ago, Mike the Boilerman said:

 

Unfortunately this seemed so obvious to me I expected discussion to immediately revolve around the effects of gate leakage, timing of paddle opening and a few other minor factors I've forgotten for now!

I too thought it was obvious as far as the theory goes but my initial thoughts were that leakage might simply be proportional and therefore not a factor. It turns out I was wrong.

I see folks are still trying to complicate it with spurious factors.

JP

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On 13/12/2017 at 14:15, sirweste said:

I think, because this is flow rate over an area, it will be 4 times faster.

If the area is considered to be P, the flow rate through P is a squared relationship. Thus when you have 2P the resulting flow rate will be 4 times greater.

The flow out due to leakage would exacerbate this I think, as it spends longer leaking because it spends longer filling.

There's also the pressure differential to consider - empty vs. nearly full lock

TO add: I'm ignoring the local drop in water height at the feed to the lock i.e. the drop in sluice discussion immediately preceding my post

2P or not 2p, it would help it fill quicker.

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Wouldn't the calculation including the effect of drop of water level in the pound be overly complicated by the size of the pound itself?  In a flight of locks the pound may be less than 50 metres and the fall probably visible, on a lock where the pound is miles long (e.g. Wheaton Aston on the shroppie) the drop wouldn't be visible to the nakes eye and would take some interesting formula to calculate the lessening of volume - and rate of flow through the paddle opening :detective:

Other than that, I'd suggest that the fill/ empty time might be 70% ish longer to fill with one paddle as although initial flow through a single paddle hole may be individually greater than the average between 2 open the corresponding reduction of flow as the lock approached equilibrium with the level outside the lock might be slightly less than said average.  But then, I'm neither mathemetician or engineer so it is only guesswork.

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14 hours ago, NickF said:

Oh Horace this causes further confusion in my brain. Your argument would hold true for ground paddles or gate paddles which are fully submerged on both sides but I was thinking more of gate paddles discharging into a deep empty lock and so discharging into air not water .... then we need one set of ratios for discharge into air and one for discharge into water further complicated by the fact that as the lock fill the paddles will then be discharging underwater and we revert to the situation you describe. 

My answer to the OP therefore is "I don't know ... too confusing" 

For the purpose of discussion, regarding any lock, of any size, or water leaks - in or out, and drop in water levels above the lock and in the lock, or side pounds, and water density and temperature, paddles in free air or submerged, and time to open paddles, and the engineering/physical units used, and any other condition that can be introduced as relevant, even if as an afterthought, I think it reasonable to assume, whatever they are, they will be the same for that particular lock, at that particular time, whether one or two paddles are used.  I am confident to think that whilst they could have a marked effect of the actual flow in each case, they will compliment each other and cancel out in the ratio calculation. 

This being the case, the formula (taken at face value as being correct) gives a flow rate for each condition - that as a ratio predict a filling time factor of 2 (or 1/2).

PS: the coefficients in the formula are for flow in cu.ft.per sec, and area in sq.ft.

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On 17/12/2017 at 18:41, Tanglewood said:

According to the Volockies on the Hatton Flight, it takes 8 secs longer if you only open paddles on one side, as you have to factor in the time it takes to stare at the water and then cross over, engage the windlass..... 

 

They should come and try that on the locks here on the K&A. I'd say the difference was closer to 8 minutes....

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2 hours ago, Tanglewood said:

According to the Volockies on the Hatton Flight, it takes 8 secs longer if you only open paddles on one side, as you have to factor in the time it takes to stare at the water and then cross over, engage the windlass..... 

I do not doubt the volockies saying that, but I do doubt it is true.  I'll wager the volockies also told you the paddles should be wound down.

George

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15 hours ago, Tanglewood said:

According to the Volockies on the Hatton Flight, it takes 8 secs longer if you only open paddles on one side, as you have to factor in the time it takes to stare at the water and then cross over, engage the windlass..... 

They my have said that, but unless you cross the gates very cautiously and with a zimmer frame it is patently not true!

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On 12/17/2017 at 18:41, Tanglewood said:

According to the Volockies on the Hatton Flight, it takes 8 secs longer if you only open paddles on one side, as you have to factor in the time it takes to stare at the water and then cross over, engage the windlass..... 

I don't believe it!...it takes me much more then 8 seconds to open the paddle, and there is still a long wait after the second paddle is opened. 

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4 minutes ago, Horace42 said:

I don't believe it!...it takes me much more then 8 seconds to open the paddle, and there is still a long wait after the second paddle is opened. 

 

I don't believe it either!

Its a story told by the volockies to gullible newbie boaters for a laugh amongst themselves I reckon, to see which ones are daft enough to believe it!

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Another factor is what one calls 'full'.

When Church Lock at Bredwyn had a busted top paddle for months on end, the bottom gate leakage was so great that the level in the lcok stabilised a good 4" below the top gates. The only way I could open a gate alone was using a mooring line tied to a bollard and the balance beam, and a spanish windlass. 

 

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