Oxford river Locks

[SandyD]

Just wondering, does anyone know why the down stream locks on the Oxford canal are octagonal?

[RS2021]

To feed more water from the river sections into the canal.

[David Mack]

The two locks concerned are below sections where the canal uses part of the river course. Both are of shallow fall, but are wider in the middle so that the water taken from the river sections is sufficient for the deeper but conventionally shaped locks below.

[magnetman]

It is probably because the ground is less stable because of the river going across making a diamond shaped lock a better solution than a standard narrow lock. It is a stronger structure. 

 

Interesting to note there are windows in the paddles at the Shipton and Aynho weir locks to deal with water feed to the next pound. 

 

For obvious reasons. 

 

[emm]

I thought it was to keep the next pound down as full as possible as the next locks down are pretty deep?

[GUMPY]

They are that shape to pass the same volume of water as the deeper next lock down.

If they were normal shape then the pound between those two locks would run dry.

 

[magnetman]

This can only work if the locks are constantly in use. The next lock down has a bywash and is also bound to leak. The weir locks don't have bywashes but they do have the cutouts in the paddles which pass a fixed amount of water through regardless of the height of the river above or the status of the lock gates. 

 

A constant feed. Its a sensible solution when there is a river above as it avoids flooding which would occur with a bywash but takes advantage of the river feed to keep the next lock happy.

 

Another one with paddle windows is Stockers lock at Rickmansworth on the GU which for very obvious reasons could not have a bywash despite the fact Springwell lock is deeper.

 

I think the upper lock at Sarah's two locks near Watford had a window at one stage to keep the short pound below in water but it was taken out when paddles were replaced by people who didn't understand how a canal works. Result = pound regularly very low for obvious reasons. 

 

I still think the diamond shape is a structural consideration but may be wrong. 

 

 

Edited October 7, 2023 by magnetman