How do Watford Staircase locks work?

[Big Bob W]

13 minutes ago, john6767 said:

No. The paddles connect the locks direct to the side pound.  The red paddle connects to lower lock to the side pound, the white one the upper lock to the side pound.

I need to draw myself a diagram now or I'm not going to sleep tonight!

We are up and down Watford several times a year - but in my defence, I am on the back of the boat with Sue doing all the work winding paddles. I just get a glimpse of water rushing in to the side pond when she opens the white one.

But to the OP, bottom line is Red before White!

 

[___]

52 minutes ago, David Mack said:

I can remember finding the odd one still usable years ago, and using them with enthusiasm when we could. But there wasn't much point really in using half the water at just one lock in the middle of a flight!

I dare say that if we happened upon one of those in early hiring days - and it’s more than possible we did - then we may not have noticed it was functional.

 

[Ronaldo47]

When we did Watford and Foxton in 1977, there were no lock-keepers, you had to work it out for yourself using the notices as guidance, and as second-time holiday boaters, we managed OK. 

 

On the return trip, we were held up at the bottom of Foxton by a descending boat that couldn't get out of the passing pound because the water level was too low for it to cross the lock cill. To let some water down, having first ascertained that the side ponds had spillways,  starting from the top lock, I opened all the paddles of the top five locks. Once the trapped boat had got itself in the lock, I waited until  the passing pound water level got to the obvious tide line, and then went back up and closed the paddles again. From memory, with all paddles open, the locks were about half full as you might expect.  

 

When we were able to make our  ascent, I noticed that water was still flowing over some of the spillways from pond to pond an hour or so later. 

Edited October 6, 2023 by Ronaldo47
typos

[PeterScott]

2 minutes ago, Ronaldo47 said:

When we did Watford ... in 1977, there were no lock-keepers, you had to work it out for yourself using the notices as guidance, ...

 

As You Do

(Photo by @John Liley)

[Rob-M]

I remember several occasions at the Bratch where welly boots were needed as someone had got the paddle order wrong and there was a lot of water over the pathways.

[Scholar Gypsy]

9 hours ago, Big Bob W said:

Isn't it the other way round?

Red Paddle empties the upper pound directly to the lower pound.

White paddle is to the side pond.

 

No. The Red paddle connects the side pond to the lower lock, the white paddle to the upper lock. When both paddles are up then the water level equalises between both locks and the side pond, you open the gate and move from one lock to the next.

[Tacet]

In essence, the side ponds at Foxton and Watford are the same as intermediate pounds on a conventional flight, it's just that the boat goes not pass through it.

 

The red before white thing is a bit overstated, it is no different from someone drawing off the lock above you before you have drawn the paddles to fill your lock.  Drawing white first can put a lockful of water (probably only a bit of a lockful in practice) into an already full side pond.  This runs away over the weir needlessly and means that when you draw red, the sidepond drops its level.  But its not a perpetual reduction, if a dozen consecutive boats draw white first, the sidepond would still only be one lockful down. 

 

If you're so inclined, you can draw all the red paddles in a Foxton staircase before any drawing any whites, without causing any problems (assuming there is no other boat in the flight).  I think it saves a few milliseconds if you discount the time expended discussing it with officialdom.

 

Edited October 7, 2023 by Tacet
Oops

[Rob-M]

1 minute ago, Tacet said:

you can draw all the red paddles in a Foxton staircase before any drawing any whites

That is what the volocky did last year when we arrived at the top just before 5pm. Whilst we started on the top lock he walked down and opened all the reds.

[Tacet]

3 minutes ago, Rob-M said:

That is what the volocky did last year when we arrived at the top just before 5pm. Whilst we started on the top lock he walked down and opened all the reds.

I've done it once or twice and, to be fair, the volocky (a different one?) had a think about it and accepted it caused no problems.

[Alway Swilby]

Every time I go through the Bascote staircase on the GU (Ham Baker paddle gear) I try to work out how the disused side ponds would have worked. Every time I fail to work it out. This staircase has "proper" side ponds and is a "proper" staircase. I get how proper side ponds work as at Hanbury, Hanwell, Bosley etc. but Bascote always defeats me.

Actually the side ponds at Hanwell are also confusing because they have three different levels.

Edited October 6, 2023 by Alway Swilby

[Wanderer Vagabond]

11 hours ago, PeterScott said:

 

As You Do

(Photo by @John Liley)

Blimey, I thought I knew how to do it.....until I read that

[magpie patrick]

9 hours ago, Alway Swilby said:

Every time I go through the Bascote staircase on the GU (Ham Baker paddle gear) I try to work out how the disused side ponds would have worked. Every time I fail to work it out. This staircase has "proper" side ponds and is a "proper" staircase. I get how proper side ponds work as at Hanbury, Hanwell, Bosley etc. but Bascote always defeats me.

Actually the side ponds at Hanwell are also confusing because they have three different levels.

The Hanwell ones need using in sequence - going up draw on the lowest one first, going down fill the highest one first. 

 

Sideponds at Bascote two-rise seem a recipe for confusion. I guess one would start by emptying the upper lock into its side pond whilst simultaneously filling the lower on from its sidepond, once that process is complete start emptying the lower lock back into its sidepond before finally emptying the lock into the canal below and going on your way, slow and lots of scope for errors, I can imagine the working boatman not bothering....

[Scholar Gypsy]

2 hours ago, magpie patrick said:

The Hanwell ones need using in sequence - going up draw on the lowest one first, going down fill the highest one first. 

 

Sideponds at Bascote two-rise seem a recipe for confusion. I guess one would start by emptying the upper lock into its side pond whilst simultaneously filling the lower on from its sidepond, once that process is complete start emptying the lower lock back into its sidepond before finally emptying the lock into the canal below and going on your way, slow and lots of scope for errors, I can imagine the working boatman not bothering....

The maths of side ponds is quite interesting (well I think so!).  The key variable is the ratio of the area of the pond to the area of the lock. If this is 1:1 then you get one solution (for the full and empty levels of each side pond, and for the amount of water that is saved - for example with two side ponds you can save 50% of the water, with one only 33%). If the ratio is much bigger then one can assume the level stays fixed in the side pond (like Foxton), and two ponds can save 2/3 of the water.

One could re-imagine each five lock flight at Foxton as one huge lock, 70' long and with a single drop of 37'6", with four large side ponds at intermediate levels. In this case 4/5 of the water is saved (the consumption is to fill or empty the last part) compared with operating it as a single 37'6" lock.  Of course the reason the lock is not built that way is that it would require rather large bottom gates (*), though it would save on brickwork.

 

(* Footnote, unless one made the bottom end of the lock a solid wall, with a hole for the boat to go through ...)

[1st ade]

On 07/10/2023 at 07:48, magpie patrick said:

The Hanwell ones need using in sequence - going up draw on the lowest one first, going down fill the highest one first. 

 

Sideponds at Bascote two-rise seem a recipe for confusion. I guess one would start by emptying the upper lock into its side pond whilst simultaneously filling the lower on from its sidepond, once that process is complete start emptying the lower lock back into its sidepond before finally emptying the lock into the canal below and going on your way, slow and lots of scope for errors, I can imagine the working boatman not bothering....

Considered as a problem within the laws of physics, there are two requirements to solve: -

• You need to fill each chamber to a certain level (to meet the requirement of getting the craft in to (or out of) the next chamber)
• Water only goes downhill (unless back pumping is in operation)

So the trick is to fill (or empty) the next stage in the sequence with the minimum amount of water going downhill (not just volume but "head")

 

E.G.  (all going uphill with full locks in front of you, but the scenario is reversible): -

• Single lock - empty into navigation below, drive in, fill from navigation above, drive out. Job done
• Single lock with side pond - empty half the lock into the side pond (as it is higher than the lower navigation), empty the rest into navigation below. Drive in. Fill from side pond (as it's lower than navigation above), fill from upper navigation, drive out.
• Single lock with two Side Ponds - empty chamber into A and close paddles. Empty rest of chamber to B and close paddles. Empty the rest into the lower navigation. Drive in. Fill from B (as it will be lower), then from A (higher) then from upper navigation - in each case closing paddles before you start the next one. Drive out

[magpie patrick]

29 minutes ago, 1st ade said:

in each case closing paddles before you start the next one. Drive out

 

This is where any error gets interesting - how long before one notices the sidepond is overflowing?!   

 

 

[1st ade]

1 minute ago, magpie patrick said:

 

This is where any error gets interesting - how long before one notices the sidepond is overflowing?!   

 

 

... or the pound above is empty...

[Scholar Gypsy]

5 hours ago, 1st ade said:

Considered as a problem within the laws of physics, there are two requirements to solve: -

• You need to fill each chamber to a certain level (to meet the requirement of getting the craft in to (or out of) the next chamber)
• Water only goes downhill (unless back pumping is in operation)

So the trick is to fill (or empty) the next stage in the sequence with the minimum amount of water going downhill (not just volume but "head")

 

E.G.  (all going uphill with full locks in front of you, but the scenario is reversible): -

• Single lock - empty into navigation below, drive in, fill from navigation above, drive out. Job done
• Single lock with side pond - empty half the lock into the side pond (as it is higher than the lower navigation), empty the rest into navigation below. Drive in. Fill from side pond (as it's lower than navigation above), fill from upper navigation, drive out.
• Single lock with two Side Ponds - empty chamber into A and close paddles. Empty rest of chamber to B and close paddles. Empty the rest into the lower navigation. Drive in. Fill from B (as it will be lower), then from A (higher) then from upper navigation - in each case closing paddles before you start the next one. Drive out

I don't think this calculation is quite right (though the operating process is correct). 

With side ponds that have the same area as the lock, then
1) With a single side pond the water level will vary between 1/3 and 2/3 full. When going downhill you put 1/3 of a lockful into the side pond (which then goes from 1/3 to 2/3 full), and then you empty the rest into the lower pound. When going uphill you take 1/3 of a lockful out of the sidepond (which then goes from 2/3 to 1/3 full), and then fill the remaining 2/3 from the upper pound.  33% of water saved.
2) With two side ponds, the upper one will vary between 1/2 and 3/4 full, and the lower one between 1/4 and 1/2 full. Going downhill you put 1/4 lockful into the upper pound (which goes from 1/2 to 3/4 full, with the lock going down from full to 3/4 full). Then you put another 1/4 lockful into the lower pond (which goes from 1/4 to 1/2 full). Then you empty the remaining 1/2 lockful to the lower pound. Going uphill you take 1/4 lockful from the lower pond (which goes from 1/2 to 1/4 full) and then another 1/4 from the top one (which goes from 3/4 to 1/2 full), and then fill the remaining 1/2 lock from the upper pound.  50% of water saved.

With large side ponds (say 20 times the area of the lock, which I would guess is the case at Foxton and Watford), they are much more efficient as the level in the side ponds can be assumed constant. So a single side pond will be at the 1/2 full level, and can take and then discharge 1/2 a lockful of water with only a small change in level. This is logically equivalent to replacing one deep lock with two shallow ones, and so will use half the amount of water.

I really should get out more.

[davidg]

48 minutes ago, Scholar Gypsy said:

With large side ponds (say 20 times the area of the lock, which I would guess is the case at Foxton and Watford), they are much more efficient as the level in the side ponds can be assumed constant. So a single side pond will be at the 1/2 full level, and can take and then discharge 1/2 a lockful of water with only a small change in level. This is logically equivalent to replacing one deep lock with two shallow ones, and so will use half the amount of water.

I really should get out more.

Boing!

As I said earlier, the "side ponds" at Watford & Foxton do not save water at all. You empty the complete contents of the upper lock into the "side pond" and completey fill the lower lock from the "side pond" in exactly the same way as you would if it were a normal pound between the locks.
edit: I should qualify that by saying no water saving compared to having five separate locks

Edited October 9, 2023 by davidg

[Mike Tee]

I’m guessing the benefit of side ponds is back in the day when working boats were flying up and down, for example Watford or Foxton, it didn’t matter if the balance of up versus down was off, because there was always enough water available for a boat going up. Coming down, the boat brought its own water with it. Without the pounds, water would have had to be allowed down for a boat to go up which would have wasted massive amounts of time.

Only worked at a particularly steep hill which is exactly what these two places had - clever people those old engineers. 

[Scholar Gypsy]

1 hour ago, davidg said:

Boing!

As I said earlier, the "side ponds" at Watford & Foxton do not save water at all. You empty the complete contents of the upper lock into the "side pond" and completey fill the lower lock from the "side pond" in exactly the same way as you would if it were a normal pound between the locks.
edit: I should qualify that by saying no water saving compared to having five separate locks

Yes, agreed. 

 

PS Looking on Google earth, the sideponds at Watford are about 350' x 50', which is over 30 times the area of the lock.

The ones at Foxton are more variable, as to shape, size and orientation. This map makes it clear they were squashed up a bit when the inclined plane was built...   I think it also shows that the pound between the two flights used to be much bigger than it is today..

https://maps.nls.uk/geo/explore/side-by-side/#zoom=16.3&lat=52.49939&lon=-0.98171&layers=257&right=BingHyb

Edited October 9, 2023 by Scholar Gypsy

[Tacet]

2 hours ago, Scholar Gypsy said:

I don't think this calculation is quite right (though the operating process is correct). 

With side ponds that have the same area as the lock, then
1) With a single side pond the water level will vary between 1/3 and 2/3 full. When going downhill you put 1/3 of a lockful into the side pond (which then goes from 1/3 to 2/3 full), and then you empty the rest into the lower pound. When going uphill you take 1/3 of a lockful out of the sidepond (which then goes from 2/3 to 1/3 full), and then fill the remaining 2/3 from the upper pound.  33% of water saved.
2) With two side ponds, the upper one will vary between 1/2 and 3/4 full, and the lower one between 1/4 and 1/2 full. Going downhill you put 1/4 lockful into the upper pound (which goes from 1/2 to 3/4 full, with the lock going down from full to 3/4 full). Then you put another 1/4 lockful into the lower pond (which goes from 1/4 to 1/2 full). Then you empty the remaining 1/2 lockful to the lower pound. Going uphill you take 1/4 lockful from the lower pond (which goes from 1/2 to 1/4 full) and then another 1/4 from the top one (which goes from 3/4 to 1/2 full), and then fill the remaining 1/2 lock from the upper pound.  50% of water saved.

With large side ponds (say 20 times the area of the lock, which I would guess is the case at Foxton and Watford), they are much more efficient as the level in the side ponds can be assumed constant. So a single side pond will be at the 1/2 full level, and can take and then discharge 1/2 a lockful of water with only a small change in level. This is logically equivalent to replacing one deep lock with two shallow ones, and so will use half the amount of water.

I really should get out more.

That's about it.  Unless you want to make it more complicated by considering the area of the side pond may not remain constant as its depth changes.

My recollection of using them in the 1970s was that, going up for example, you drew the side pond paddle as you walked from shutting the bottom gates, as intended.

But you didn't wait for a near level and drop the paddle.  The practice was to then draw the top gate paddles before returning to the side pond.  When the tide turned, that is water was heading into the side pond rather than out, you dropped that paddle.

It must have saved a little water over neglecting the side pond entirely and maybe you worked the lock a little faster.

[adam1uk]

3 hours ago, davidg said:

Boing!

As I said earlier, the "side ponds" at Watford & Foxton do not save water at all. You empty the complete contents of the upper lock into the "side pond" and completey fill the lower lock from the "side pond" in exactly the same way as you would if it were a normal pound between the locks.
edit: I should qualify that by saying no water saving compared to having five separate locks

 

Going up a normal staircase you need the bottom one empty and the ones above full -- but at Foxton and Watford you don't; as you say you're just taking the water from the side pond.  So doesn't that give a water saving? Or is it just a time saving?

[Mike Tee]

Logic tells me it’s just time, because water won’t flow up hill, unless it’s particularly windy!

[Scholar Gypsy]

10 hours ago, adam1uk said:

 

Going up a normal staircase you need the bottom one empty and the ones above full -- but at Foxton and Watford you don't; as you say you're just taking the water from the side pond.  So doesn't that give a water saving? Or is it just a time saving?

Comparing Foxton and Bingley - both five lock staircases - the latter will use more water, unless all the boats are travelling in the same direction. (Ignore the fact that the latter are wide locks, which also permits the shuffle maneuver...)

I quite like the French approach which is to open all the gates and then fill the chambers up from the top, moving the boats forward as you go!
 

 

[dmr]

Going through a lock moves a lockfull of water, and going through a flight of locks moves a lockfull for each lock regardless of whether its a flight of locks, a staircase, or a Foxton staircase.

Going down a full flight of locks is a bit variable depending upon if you "take a lockfull with you" or let lockfulls go over the bywash, but ideally one lockful from the top pound will get you down.

When going up water must come from the next pound or next chamber up and all the water used must ultimately come from the very top pound.

With a conventional staircase all the lockfulls come from the top pound but with Foxton or a conventional flight most of the water comes from the intermediate pounds (which is quicker) but ultimately the water used must be replenished from the top pound via the bywashes and this can happen slowly or overnight.

So I think the Foxton sideponds are a store of water to keep the flight working quickly if boat traffic is taking water out quicker than the bywash flow is putting it back in ???????