Wilts & Berks Canal lock gate configuration

[magpie patrick]

I bought this book (cover below)

yesterday at our local second hand book shop yesterday, and flicking through saw a picture of Forest Lock, the first lock from the K&A (other than the stop lock). I'd not seen a picture of this before and it quite clearly has a single bottom gate. 

I also recall that the lock at the head of the Calne Branch has a single bottom gate. However the picture of Dauntsey lock below 

 

Clearly shows a pair of gates. Dauntsey is upstream of the junction with the Calne branch so it's possible the configuration changed geographically as one went from west to east. The book has no other pictures of locks west of Dauntsey and all locks east seem to have two bottom gates.

 

Anyone any idea why the variation? Was the west end built later/earlier? Just thinking that on three other canals I can think that have both types the locks with single gates were built significantly later. Any thoughts? 

[Tony Brooks]

Pretty much like the South Oxford with varying gate designs.

 

I am sure you have heard the theory that as bottom gates have to withstand a greater water pressure they were often pairs, but it seems the first phot has a single bottom gate so that blows that theory away.

[magpie patrick]

On 30/09/2022 at 16:13, Tony Brooks said:

Pretty much like the South Oxford with varying gate designs.

 

I am sure you have heard the theory that as bottom gates have to withstand a greater water pressure they were often pairs, but it seems the first phot has a single bottom gate so that blows that theory away.

 Yes, I've heard various theories! I think which was chosen was a matter of local preference - from my recollection on the Birmingham and Fazeley started with single leaf bottom gates, the others (Stratford, Oxford, HNC) changed their preference after building a number of locks with double bottom gates. The BCN made the change twice, to single gates for Titford, Ryders Green, the new locks when the new main line was built and then back to double for the Tame Valley and Rushall. 

I don't know what order things happened in on the Wilts and Berks, were these locks, the first, the last, orn just exceptions?

[Pluto]

It is interesting that contemporary publications do not make much mention of whether to use a single or mitre gates on a narrow lock. The ease of operation by having a single gate is mentioned, though no specific advantage is suggested. I wonder if geography played a part, with engineers making the decision based upon what materials were available, or what the ground water conditions were like. Mitre gates create more lateral stress on the lock walls, while single gates create longitudinal. Depending on the type of gate, the specification for stonework could vary slightly, and local availability of materials could affect the decision. Soil stability is another variable which could affect a decision, given the different directions the load operates in, particulalry when soil movement could adversely affect the ground paddle culverts.

[Rose Narrowboats]

The ground pressure theory is interesting...but I'm not entirely convinced as Hillmorton Locks built are built on terrible ground - part running sand and part bog. The house at the bottom lock is built on an oak raft, and I've half an idea the locks may be braced similarly.

 

The paired locks at Hillmorton were built nearly 70 apart, and the new locks are arguably the best desighned anywhere on the system (especially in respect of the culverts) yet both designs use bottom gates.

 

I don't buy the ease of use theory either - even one person can open a pair of mitre gates at least as quickly as heavy single gate.

 

So I'd like to put forward another theory - cost. Certainly two of the canals that use single bottom gates that I can think of were built on the cheap - the Oxford below Banbury, and the last bit of the Stratford. I'm not sure how that ties in with BCN finances at the time they built single bottom gates though?

[Derek R.]

3 hours ago, Rose Narrowboats said:

(Snipped)

I don't buy the ease of use theory either - even one person can open a pair of mitre gates at least as quickly as heavy single gate.

(Snipped)

 

 Agreed. You can stand on the mitre and kick one gate open with ease, then step off and open the other.

[Tam & Di]

9 hours ago, Derek R. said:

 Agreed. You can stand on the mitre and kick one gate open with ease, then step off and open the other.

..... a practice that works equally well on a wide canal like the Grand Union.

 

Tam

[Pluto]

12 hours ago, Derek R. said:

 Agreed. You can stand on the mitre and kick one gate open with ease, then step off and open the other.

In terms of understanding history, what we think now is irrelevant. We need to understand how they were thinking in the past, and published accounts suggest that they thought single gates quicker to use than mitre gates. That is what would have influenced design. It was also normal to leave paddles open, so having them on one gate would have been easier for the boatman/woman. Speed was still of minor importance in the second half of the 18th century. For the carriage of heavy goods, there were no inland competitors until the arrival of railways. The whole ethos of work was still based on the seasonal agricultural trade, which is why canal building slowed down during the sowing and harvesting seasons. We are not talking about an 'industrialised' society, where time is money. Of course, once built, those involved would use canals to the best of their ability, but there was a difference between those using their craft skills to the best, compared to how investors thought about building structures.

 

On foundations, wooden piling and 'gratings' were the standard when canals were first built, with more modern foundation techniques, such as stone/brick inverts, just beginning to be used. the French were far and away the most advanced in this respect, with concrete being used for lock foundations towards the end of the 18th century.

[Tam & Di]

2 hours ago, Pluto said:

In terms of understanding history, what we think now is irrelevant. We need to understand how they were thinking in the past, and published accounts suggest that they thought single gates quicker to use than mitre gates.

 

I would guess too that the majority of locks had lock keepers, and for him to prepare a lock for an approaching craft a single gate would obviously be quicker.

 

Tam

[Pluto]

25 minutes ago, Tam & Di said:

 

I would guess too that the majority of locks had lock keepers, and for him to prepare a lock for an approaching craft a single gate would obviously be quicker.

 

Tam

From checking a few photos, the single gates seem to be hung on the towpath side, which could make it easier in not having to run around to close a ground paddle when working uphill, though I suppose the tow line could catch on the gate when working down.

[Derek R.]

6 hours ago, Pluto said:

In terms of understanding history, what we think now is irrelevant. We need to understand how they were thinking in the past, and published accounts suggest that they thought single gates quicker to use than mitre gates. That is what would have influenced design. It was also normal to leave paddles open, so having them on one gate would have been easier for the boatman/woman. Speed was still of minor importance in the second half of the 18th century. For the carriage of heavy goods, there were no inland competitors until the arrival of railways. The whole ethos of work was still based on the seasonal agricultural trade, which is why canal building slowed down during the sowing and harvesting seasons. We are not talking about an 'industrialised' society, where time is money. Of course, once built, those involved would use canals to the best of their ability, but there was a difference between those using their craft skills to the best, compared to how investors thought about building structures.

 

On foundations, wooden piling and 'gratings' were the standard when canals were first built, with more modern foundation techniques, such as stone/brick inverts, just beginning to be used. the French were far and away the most advanced in this respect, with concrete being used for lock foundations towards the end of the 18th century.

 

I think most of your comment was in response to Rose Narrowboats. My extraction was in the element applying to the trick of kicking a gate open from the centre of the mitre. 😉

[magpie patrick]

In considering "why" also look at "where". As far as I'm aware only the B&F started with single bottom gates, and my guess is the configuration at Farmers Bridge dictated this - no room for balance beams on the offside. Once a configuration was adopted companies stuck with it - they didn't revisit the issue at every lock.

 

The Stratford and Oxford companies ran out of money, and when they resumed construction they went for single gates. Cost?

 

The Huddersfield Narrow didn't build Diggle locks until Standedge Tunnel was nearly complete, so they were built around ten years after all the others on that canal. Keeping the tow rope clear seems to have been the motive in this case as all the equipment is on the offside.

 

When the BCN was created they had 32 locks with double bottom gates and 38 with single, reflecting the different policies of the B&F and the Birmingham Canal. For whatever reason they settled on single gates for new locks, until the mid 19th century when they changed to double. Walsall locks were the last of the single and first of the double as seven locks have single bottom gates and one has double - the BCN was the only instance of switching from single gates to double (and also the only one midway through building a flight!)

 

I know no more about the Wilts & Berks with regards to lock gates than is at the top of this page. Any one else have any clues?

 

Finally for operation as Pluto suggests it is the prevailing view at the time that matters not our view now. I'm not sure lock keepers would come into it though, there wouldn't be one at every lock on a flight like Farmers Bridge 

[Heartland]

There is something missing from Patrick's explanation and that is cause and effect regarding the Birmingham & Fazeley. The early locks on the BCN as the original BCN need to be considered. Smethwick Locks, original locks, had a bottom mitre pair. 

 

The much more recent Walsall Locks had one lock with a bottom mitre pair because of a basin below it and access needed for the Flour Mill. There is also the choice of the engineer to be considered. For the Birmingham & Fazeley the engineers were James Bough and Samuel Bull who had worked previously on other canals. With the early BCN was it the choice of James Brindley or did Samuel Simcox have an input as to gate design and with Samuel Simcox it is also important to look at the north Oxford

[magpie patrick]

On 08/10/2022 at 08:40, Heartland said:

There is something missing from Patrick's explanation and that is cause and effect regarding the Birmingham & Fazeley. The early locks on the BCN as the original BCN need to be considered. Smethwick Locks, original locks, had a bottom mitre pair. 

 

The much more recent Walsall Locks had one lock with a bottom mitre pair because of a basin below it and access needed for the Flour Mill. There is also the choice of the engineer to be considered. For the Birmingham & Fazeley the engineers were James Bough and Samuel Bull who had worked previously on other canals. With the early BCN was it the choice of James Brindley or did Samuel Simcox have an input as to gate design and with Samuel Simcox it is also important to look at the north Oxford

 

Thanks Ray - I'm aware that Smethwick locks as they are today are the new ones - trying to keep a topic relatively simple can involve glossing over the details in certain locations. I assume the original 29 locks on the Birmingham Canal Main Line (20 at Wolverhampton, 3 up at Spon Lane and 6 down at Smethwick) all had mitre bottom gates, along with the three at Spon Lane on the Wednesbury Old Canal that now connect the old and new main lines (and what was that originally called?) 

 

I'm very curious as to how the presence of a basin below a lock necessitated mitre gates ? The only thing I can think of is that a chamber with mitre gates can be a couple of feet shorter and in this instance that was critical?

[magpie patrick]

On 30/09/2022 at 15:47, magpie patrick said:

I bought this book ... yesterday at our local second hand book shop yesterday, and flicking through saw a picture of Forest Lock, the first lock from the K&A (other than the stop lock). I'd not seen a picture of this before and it quite clearly has a single bottom gate. 

 

I also recall that the lock at the head of the Calne Branch has a single bottom gate. However the picture of Dauntsey lock... Clearly shows a pair of gates. Dauntsey is upstream of the junction with the Calne branch so it's possible the configuration changed geographically as one went from west to east. The book has no other pictures of locks west of Dauntsey and all locks east seem to have two bottom gates.

 

Anyone any idea why the variation? Was the west end built later/earlier? Just thinking that on three other canals I can think that have both types the locks with single gates were built significantly later. Any thoughts? 

 I now have at least a partial answer - Hadfield "The Canals of South and South East England" states that work started at Semmington so as to be able to serve the market for coal carriage to Chippenham and Calne at the earliest opportunity - Thus the length with the two locks I know to have had single bottom gates were part of this initial phase of construction and the locks I know to have mitre tail gates were in later phases