How do Watford Staircase locks work?

[Scholar Gypsy]

10 minutes ago, dmr said:

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 ???????

With Bingley, if you are going uphill and all the lock chambers are empty, then you will need to take four lockfulls of water from the top pound, to fill up each of the top four locks. Conversely if you are going downhill and the locks are full then you will empty four locks of water into the lower pound. Not as efficient as a Foxton type arrangement. (To make Bingley more efficient, you need something like boats only going uphill in the morning, and only doing downhill in the afternoon. This is a bit counter-intuitive, I know, and ignores the possibility of shuffling.)

[Ken X]

This was how the Five Rise was being run when we last came up it.  All down boats for a set time then the flight was reversed and all up boats.

 

Mind you it can go wrong.  We were the first up boat and the lockie said to get into the bottom lock and ready whilst they preped and filled the other locks.

We were sitting ready and dozing when there is much shouting for us to reverse out the lock a bit quick.  Next minute the gates are weiring spectacularly, somebody got the filling procedure out of whack. 😄

 

They did apologize though and whizzed us up very efficiently.

[dmr]

16 minutes ago, Scholar Gypsy said:

With Bingley, if you are going uphill and all the lock chambers are empty, then you will need to take four lockfulls of water from the top pound, to fill up each of the top four locks. Conversely if you are going downhill and the locks are full then you will empty four locks of water into the lower pound. Not as efficient as a Foxton type arrangement. (To make Bingley more efficient, you need something like boats only going uphill in the morning, and only doing downhill in the afternoon. This is a bit counter-intuitive, I know, and ignores the possibility of shuffling.)

 

Thats sort of what I was saying to say, with Foxton the water comes from the sideponds, not the top pound, but this leaves the sideponds a bit lower and the water to replenish them must ultimately come from the top pound, but maybe not till uch later.

 

The Soar has wide locks, as does the GU, so when the inclined plane was replaced with narrow locks I reckon the engineer knew it would be a bottleneck so the sideponds were included to speed things up.

[Scholar Gypsy]

7 minutes ago, dmr said:

 

Thats sort of what I was saying to say, with Foxton the water comes from the sideponds, not the top pound, but this leaves the sideponds a bit lower and the water to replenish them must ultimately come from the top pound, but maybe not till uch later.

 

The Soar has wide locks, as does the GU, so when the inclined plane was replaced with narrow locks I reckon the engineer knew it would be a bottleneck so the sideponds were included to speed things up.

Foxton and Watford locks were built as narrow locks.  The left hand map here shows there were sideponds in the mid 1800s (and probably earlier). Some of them got a bit squished when the inclined plane was built ca 1900 (see right hand map). The one by the crossing pound in the middle was completely obliterated, I think.

https://maps.nls.uk/geo/explore/side-by-side/#zoom=16.3&lat=52.49936&lon=-0.98177&layers=257&right=168

[David Mack]

19 minutes ago, dmr said:

Thats sort of what I was saying to say, with Foxton the water comes from the sideponds, not the top pound, but this leaves the sideponds a bit lower and the water to replenish them must ultimately come from the top pound, but maybe not till uch later.

No. Each sidepond is replenished when the lock above is emptied into it. 

[robtheplod]

All this makes you think doesn't it - they were really bright back then...  what an age for inovation!

[dmr]

5 hours ago, Scholar Gypsy said:

Foxton and Watford locks were built as narrow locks.  The left hand map here shows there were sideponds in the mid 1800s (and probably earlier). Some of them got a bit squished when the inclined plane was built ca 1900 (see right hand map). The one by the crossing pound in the middle was completely obliterated, I think.

https://maps.nls.uk/geo/explore/side-by-side/#zoom=16.3&lat=52.49936&lon=-0.98177&layers=257&right=168

Another goot theory bites the dust 😀

5 hours ago, David Mack said:

No. Each sidepond is replenished when the lock above is emptied into it. 

But in normal operation the sideponds do nothing, the water from the upper pound goes into the sidepond then goes right back out into the lower pound.

The exact role played by the sideponds during the flight turn-arround is still making my brain hurt. Myself and Goliath worked it out last night but then had a couple more pints and forgot everything 😀.

The sideponds are only an intermediate local store of water and so ultimately any water must come down from the top/summit pound????

Do the sideponds actually save any water like a conventional sidepond does (on the Droitwich etc). I dont think they do but I need to think a bit more.

.......................

I have just realised that on our travels this summer we have done 5 standard staircases (one wide, four narrow), a flight that looks like a staircase but isn't (the Bratch), two sidepond staircases (Foxton and Watford) and used proper sideponds (Droitwich).

[Tacet]

54 minutes ago, dmr said:

Another goot theory bites the dust 😀

But in normal operation the sideponds do nothing, the water from the upper pound goes into the sidepond then goes right back out into the lower pound.

The exact role played by the sideponds during the flight turn-arround is still making my brain hurt. Myself and Goliath worked it out last night but then had a couple more pints and forgot everything 😀.

The sideponds are only an intermediate local store of water and so ultimately any water must come down from the top/summit pound????

Do the sideponds actually save any water like a conventional sidepond does (on the Droitwich etc). I dont think they do but I need to think a bit more.

.......................

I have just realised that on our travels this summer we have done 5 standard staircases (one wide, four narrow), a flight that looks like a staircase but isn't (the Bratch), two sidepond staircases (Foxton and Watford) and used proper sideponds (Droitwich).

The side ponds at Watford and Foxton operate as single locks in a conventional flight.  The side pond is, in effect, the intermediate pound.

 

Therefore, they neither save nor lose water compared to individual locks (without side ponds).   But compared to other (all other in the connected system?) staircase locks they are more economical. Staircases such as Bingley are very wasteful when turned to allow a boat from the opposite direction to pass.

 

On a single lock with a side pond, it effectively becomes two locks again with the pond operating as the intermediate pound.  As Scholar Gypsy has said, it does not half the use of water as the side pond itself rides and falls when operated.  This also occurs with locks in a flights, but is less marked as the pounds are larger than side ponds.

[dmr]

19 minutes ago, Tacet said:

The side ponds at Watford and Foxton operate as single locks in a conventional flight.  The side pond is, in effect, the intermediate pound.

 

Therefore, they neither save nor lose water compared to individual locks (without side ponds).   But compared to other (all other in the connected system?) staircase locks they are more economical. Staircases such as Bingley are very wasteful when turned to allow a boat from the opposite direction to pass.

 

On a single lock with a side pond, it effectively becomes two locks again with the pond operating as the intermediate pound.  As Scholar Gypsy has said, it does not half the use of water as the side pond itself rides and falls when operated.  This also occurs with locks in a flights, but is less marked as the pounds are larger than side ponds.

Yes, thats exactly how they work, they are just a pound but out to the side, but they have the advantage that the paddles (locks) are right next to each other so "taking the water with you" is easy and the normal thing to do. The "overflows" from one sidepond to the next are directly equivalent to a lock bywash.

[David Mack]

1 hour ago, dmr said:

Do the sideponds actually save any water like a conventional sidepond does (on the Droitwich etc). I dont think they do but I need to think a bit more.

The Foxton and Watford staircases use exactly the same amount of water as if they were separate conventional single locks, and you went through end to end without passing a boat coming the other way within the flight. So no, you don't save water in the way that the top 3 at Hanbury do (although because those are deeper locks there is more benefit from the water saving).

But compared with locks like Bingley Five Rise, which have no intermediate ponds, you save a lot of water. For example if you start with Bingley all empty then work one boat up and one boat down, you will take 5 lockfuls of water from the upper pound on the way up (and leave all 5 locks full), then on the way down you will empty 5 lockfuls of water into the bottom pound, and leave the locks empty. Doing the same on the 5-lock staircases at Foxton only needs one lockful of water from the top pound.

[dmr]

37 minutes ago, David Mack said:

The Foxton and Watford staircases use exactly the same amount of water as if they were separate conventional single locks, and you went through end to end without passing a boat coming the other way within the flight. So no, you don't save water in the way that the top 3 at Hanbury do (although because those are deeper locks there is more benefit from the water saving).

But compared with locks like Bingley Five Rise, which have no intermediate ponds, you save a lot of water. For example if you start with Bingley all empty then work one boat up and one boat down, you will take 5 lockfuls of water from the upper pound on the way up (and leave all 5 locks full), then on the way down you will empty 5 lockfuls of water into the bottom pound, and leave the locks empty. Doing the same on the 5-lock staircases at Foxton only needs one lockful of water from the top pound.

 

Yes, I agree (I think 😀)

This has been a good thread and made me think very hard about locks.

So.....

The sideponds turn a staircase into a conventional flight of locks.

A conventional flight of locks uses only a single lock of water for the entire flight, either up or down, as long as its done correctly.

???

[beerbeerbeerbeerbeer]

22 hours ago, dmr said:

The exact role played by the sideponds during the flight turn-arround is still making my brain hurt. Myself and Goliath worked it out last night but then had a couple more pints and forgot everything 😀.

Yes, I’ve forgotten too 😃.

 

But what a good evening we had in the Shroppie Fly, a complete transformation,

And the Anchor was on very good form for us too.

[davidg]

21 hours ago, dmr said:

 

 

This has been a good thread and made me think very hard about locks.

So.....

The sideponds turn a staircase into a conventional flight of locks.

A conventional flight of locks uses only a single lock of water for the entire flight, either up or down, as long as its done correctly.

???

 

If you think about the way the water moves around the thing which separates a conventional sidepond, as found on the Grand Junction/Atherstone etc. from what happens at Foxton/Watford/Bratch is that  where there is a conventional sidepond the sidepond is filled from, and empties into the same lock, you only need 1 paddle to operate it. The sidepond can save up to half a lockfull of water. The limiting case of saving half a lockfull would require a sidepond with infinite surface area. Filling such a sidepond would present a challenge but once you've got past the initial fill then happy days😀

 

This isn't the way the the "side ponds" at Foxton etc. work. We could call them something different to avoid confusion, how about "pounds over at the side" until someone comes up with a snappier name.

 

For a conventional staircase a matrix can be constructed representing water usage for the four possible states of operating sequence: boat up followed by boat down, boat up followed by boat up, boat down followed by boat up and boat down followed by boat down.

 

                                 Following boat:       up             down

 

                     Previous boat:        up        1/1            0/5                    Where the numbers represent the number of lockfulls drawn off

                                                                                                           the top pound/number of lockfulls tipped into bottom pound by

                                               down        5/0            1/1                    the following boat. Let's assume a five lock staircase.

 

What the "pounds over at the side" allow you to do is to be borrow the water from the sideponds temporarily in the down folowed by up case because you don't have to fill the top four locks and then fill the top lock again from the top pound. This water can then be replenished in the up followed by down case by only tipping the bottom lock into the bottom pound, the rest can go into the "pounds over at the side" (someone please come up with that snappier name🙂), replenishing the water stored there. What you then end up with is:

 

                               Following boat:         up            down

 

                   Previous boat:         up         1/1           0/1

 

                                              down         1/0           1/1

 

Which is the way a conventional flight of five separate locks works. This requires the level intermdiate pounds to be allowed to fluctuate, if any of the water goes over the weirs then all bets are off.

 

Too much spare time at the moment🙂 Feel free to correct my numbers if you think they are wrong.

 

Edited October 11, 2023 by davidg
The formatting went wrong

[dmr]

I think your figures are good but I will try to have a bigger look/think.

 

I propose that the sideponds as at Atherstone etc etc should be called sideponds, but the things at Foxton etc etc should be called sidepounds because they are just a standard pound but at the side.

There is a sort of progression here.

Many lock flights just have standard "linear" pounds to act as a store of water.

Some flights have short pounds, maybe just space for two boats to pass, so the pound is extended to the side to hold more water. Devizes is the most spectacular example but this arrangement is very common.

Next is the Bratch (and one or two others) where the linear pound is very small, much too short for a boat, and all the water is stored to the side (and maybe a little distance away).

The extreme case is Foxton where the linear pound does not exist at all and all the water is in the sidepond, and a gate is missing.

 

I wonder why the Bratch was not made like Foxton, it would have saved the cost and trouble of the extra gates????

 

and another thought, on a lock flight on a theoretical and perfect canal with no leakage, no water should ever flow over the bywash, each pound just goes up and down by one lockfull to provide the water for filling the lock below it. An ideal locking should not send any water over a bywash as long as a boat going down fills the lower lock first, and you don't have two boats in the same pound going the same way.

[Ronaldo47]

Indeed, in the dry summer if 1976, when locking hours were severely limited, I don't recall seeing any water flowing via the bywashes on the Southern Oxford.