Canal Locks

[ohdearme]

Hello, I love the friendly atmosphere around a lock and please help with three questions:

 

Why do locks have angled gates? Someone said that the water pressure helps to close them. Is this right?

 

Why do you see water pouring through closed gates? Is that just a leak?

 

I was at the beautiful Thames at Goring and wonder why the boats cannot just use the wider part of the River?

 

You see I need some education.

 

Best regards

 

Alan

[dimreepr]

 

 

1/ yes

 

2/yes

 

3/ From this picture it looks like the river has a weir.

Edited August 24, 2015 by dimreepr

[imatfaal]

Hello, I love the friendly atmosphere around a lock and please help with three questions:

 

Why do locks have angled gates? Someone said that the water pressure helps to close them. Is this right?

 

Why do you see water pouring through closed gates? Is that just a leak?

 

I was at the beautiful Thames at Goring and wonder why the boats cannot just use the wider part of the River?

 

You see I need some education.

 

Best regards

 

Alan

 

Angled gates - keeps them shut; stops the extra weight of water upstream from pushing them open

 

Don't need to be absolutely water-tight just good enough to hold the tens of cubic metres of water for each cycle. Water gushing through can actually be a low flow. Also you open sluices in the gates to allow them to be moved once you are ready - you cannot push a gate through the water without the sluices open.

 

Locks are to get boats up and down inclines that would not normally be navigable - they are not about using wider/narrower bits of river. Maybe the bit of thames you saw was particularly wide and shallow thus a deep narrow canalised section was created

 

You also get these if you are lucky - taken a few weekends ago at St Ives Lock on the Great Ouse

 

[swansont]

I was at the beautiful Thames at Goring and wonder why the boats cannot just use the wider part of the River?

 

From the look of it on Google maps, the wider part dead-ends at a dam. Which you might expect, because you can't really have a lock without a corresponding drop elsewhere on the river, if it reconnects. So a dam or a waterfall of sorts, neither of which is going to be navigable.

[Acme]

Hello, I love the friendly atmosphere around a lock and please help with three questions:

 

Why do locks have angled gates? Someone said that the water pressure helps to close them. Is this right?

...

Best regards

 

Alan

While water pressure does seal the gate once it is closed, the gates are primarily opened and closed mechanically. In small locks this can be done by hand, in larger locks by motors.

Locks

Balance beam

 

A balance beam is the long arm projecting from the landward side of the gate over the towpath. As well as providing leverage to open and close the heavy gate, the beam also balances the (non-floating) weight of the gate in its socket, and so allows the gate to swing more freely.

Top gate of a lock, showing the balance beams and paddle winding gear.

Edited August 24, 2015 by Acme

[ohdearme]

Thank you so much everybody, the pics are a bonus too.

Best

Alan

[Acme]

Thank you so much everybody, the pics are a bonus too.

Best

Alan

You're welcome.

I was reading about the gates on the Panama canal and they started using hydraulic arms to open and close the gates in '98.

 

Panama Canal locks

...The original gate machinery consisted of a huge drive wheel, powered by an electric motor, to which was attached a connecting rod, which in turn attached to the middle of the gate. These mechanisms were replaced with hydraulic struts beginning in January 1998, after 84 years of service. The gates are hollow and buoyant, much like the hull of a ship, and are so well balanced that two 19 kW (25 hp) motors are enough to move each gate leaf. If one motor fails, the other can still operate the gate at reduced speed. ...

[studiot]

There are no locks at this point but here is Cheshire Canal passing over a road in an iron trough.

 

 

 

[ohdearme]

sorry to trouble you, I want to get a jpeg onto this topic as I have another question. Copy and paste does not work. what to do please?

Alan

[studiot]

Go to more reply options (underneath right of the quick reply box)

 

More R O underneath left under Attach Files click on choose files.

 

Upload your jpeg from the box which opens.

 

You will see a new line appear under the text input box listing your jpeg

 

When it has uploaded click in the text posting box where you want to put the file and then click on add to post in the line under the text input box.

 

I look forward to your picture.

 

 

[Acme]

sorry to trouble you, I want to get a jpeg onto this topic as I have another question. Copy and paste does not work. what to do please?

Alan

Hit the toggle switch in upper-left corner of edit box then type the img tags at either end of the pasted url.

[/img]

Note: Studiot's method is if the image is yours and on your computer, whereas my method is for displaying an image from a web page.

[ohdearme]

Thank you Studiot and Acme for helping me get my pic on here.

 

Along the Grand Union Canal in Hanwell near where the River Brent comes into it, I saw this structure. I have no idea what it's purpose is, surely not just for getting water to a lower level as it appears. What is it for please?

Best

Alan

 

 

 

[studiot]

A weir controls the flow and flow regimes of the water particularly when the flow is low.

As water and flow levels rise, it has a decreasing effect on the water.

The hydraulic characteristics of the weir in relation to the flow, depend, amongst other things, upon its length (e width across the river).

The 'fingering' pattern of the layout increases this length considerably.

 

Your pictured weir is the subject of current improvement and naturalisation plans.

 

and

http://thamesriverstrust.org.uk/projects/river-brent-eel-pass-projects/river-brent-eel-pass-inception-report/

 

http://www.thames21.org.uk/wp-content/uploads/2014/05/brent_river_corridor_improvement_plan_final_2014.pdf

Edited November 19, 2015 by studiot

[DevilSolution]

Do you wanna buy a cabin cruiser on the staffs and worcs? 2* 100w solar panels, regulator, TV, cooker, toilet, no head room etc??

 

got solar panel Christmas tree and fairy lights aswell!!!!!!

[DevilSolution]

I retract that, they renewed my licence!

[ohdearme]

Thank you Studiot, and for the links as I live near the Silkstream in Edgware and the Rive Brent in Hendon.

 

I took this in Limehouse Basin, Mile End, London. A weir next to a canal lock. I cannot keep watch 24 hours a day but it seems to flow and then not. What is going on here please.

Best

Alan

 

[studiot]

Not sure.

 

Are they saving water in the pumping from one side to the other or is the left hand side now disused?

 

There is an arrangement in Holland that looks similar on the canal between the Isselmeer and Muiderslot castle.

[ohdearme]

Shame I didn't notice, thanks.

Alan

[DevilSolution]

Its usually based on erosion, because most canals and locks were built late 18th century onwards the upkeep was mostly disregarded (water supplies come from huge reservoirs usually and because it rains so much they don't have to cry over spilt milk). One hindrance to this trickle is that it can actually give a fair bit of thrust against a stationary boat, forcing you backwards (such as when your in a queue for the lock). In general most people don't see it as an issue as every time a person goes up or down the lock a huge amount of water is lost, so this trickle is really just a grain of sand on a beach. Breaches are a different matter, they can cause huge problems but now im yattering. One interesting feature of the canals is at some bridge holes (not all but most by me) there are pieces of round metal that are embedded into the side of that bridge, if you see these they usually have lots of indented holes/lines through them, these are from the olden days when the horses rope would rub against the metal as it passed through the bridge hole.

 

Oh and sorry i misread your post, the reason it would stop would be when the water level on one side is less than the other, even marginally. This leak is centrally based between the two shutters so when the water (on the right in that photo) got below the leak it would stop.

 

In fact relative to the pressure and location of the leak the water might slow to trickle if the water on the right decreased even 10cm (as the huge amount of pressure on that gap would rapidly decrease the closer it got to the level of the gap) It's probably some exact ratio or equation.

 

Also i just noticed that the water streaming in is streaming INTO a lock, if someone has just shut the lock (in the past 30 minutes or so) then the water level could be elevating itself and levelling out (as most boaters close the locks as soon as they can).

Alternately someone could have gone down the lock and closed the shutters or gate the other end which means slowly but surely the lock will be filling up, again eventually it will fill to the point of the leak and will no longer flow.

 

Finally (and this really is finally), if this is one side of the lock then if you have a leak the other side of the lock also (that's bigger), depending on their ratio's you could very easily find that someone has just come UP the lock and filled it completely, now because the other gate has a bigger leak than these shutters, slowly the water will leave the lock eventually reaching the point where the first set of gates shows its leak.

(I'm putting my money on this as the answer mainly because if the ratio is very small, it would take along time for the shutters to show their leak and it would also be almost impossible to actually see, the water level dropping 10cm over a 3 hour period would require a fine set of eyes).

Not sure.

 

Are they saving water in the pumping from one side to the other or is the left hand side now disused?

 

There is an arrangement in Holland that looks similar on the canal between the Isselmeer and Muiderslot castle.

 

Likely a diverge in the canals, one going this the other that. Most splits are usually at junctions but it makes sense they split this way. ( if your gona split the two canals and both are gona require a lock before x amount of miles, putting both locks together would save manpower and time ). (scrap that idea, you'd have one lock and then they would diverge, Unless the locks are different sizes)

 

Alternately one could feed into a dry dock or marina while the other continues.

 

Alternately it could be (or been) an especially busy part of the canals (when they were commercially used) and simply required the use of 2 locks. (he mentioned it being in london so that would be my guess)

Edited November 25, 2015 by DevilSolution