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What are the two square holes for?


WotEver

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4 minutes ago, WotEver said:

I saw this asked in a Brum forum and I have no idea so thought I’d see who on here might know. Gas Street obviously, but what are the two small holes for?

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Within the city of Birmingham (and perhaps a little beyond?) the fire service have the right to extract water from the canal and there are many bridges which have 'doors' such as these to allow them to do this. In this case there is a filled in bridge hole beneath Gas Street so they aren't as random as they might appear at first glance.

 

JP 

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Some of the doors have wooden rollers to help feed the hose down to the water. When I first boated on the BCN I spent several hours pondering what they were while boating along. Before finding out the fire brigade answer on CWDF my best guess was a way of craning stop planks in and out. Some of the holes aligned with stop plank slots under bridges, but most did not, so not a satisfactory theory.

 

Jen

Edited by Jen-in-Wellies
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28 minutes ago, Jen-in-Wellies said:

Some of the doors have wooden rollers to help feed the hose down to the water. When I first boated on the BCN I spent several hours pondering what they were while boating along. Before finding out the fire brigade answer on CWDF my best guess was a way of craning stop planks in and out. Some of the holes aligned with stop plank slots under bridges, but most did not, so not a satisfactory theory.

 

Jen

I too wondered when first boating in the West Midlands in the 80s and can’t now remember who told me about the fire brigade and the Second World War need for vast amounts of water, but it was one of those moments when one realises that the explanation is so obviously correct that one never forgets.

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6 minutes ago, Stilllearning said:

I too wondered when first boating in the West Midlands in the 80s and can’t now remember who told me about the fire brigade and the Second World War need for vast amounts of water, but it was one of those moments when one realises that the explanation is so obviously correct that one never forgets.

Had a similar thing with the islands in the BCN main line. Before finding out they were for collecting tolls and used to have huts on them for the folks doing the gauging and toll collection I came up with several other theories. These included making stop planks easier to install for dewatering sections of canal and traffic calming to slow boats down!

 

Jen

Edited by Jen-in-Wellies
spellling and punctuation
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OK I'll stick my neck out and ask.

 

I'm obviously missing something here.... why not just lob the hose over the bridge side??

 

The pumps would still draw the water wouldn't they?

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2 hours ago, Jen-in-Wellies said:

Had a similar thing with the islands in the BCN main line. Before finding out they were for collecting tolls and used to have huts on them for the folks doing the gauging and toll collection I came up with several other theories. These included making stop planks easier to install for dewatering sections of canal and traffic calming to slow boats down!

 

Jen

There are some that were intended to prevent dewatering. The famous i at the top of Farmers Bridge for instance. That was there so you could put stop planks in in the event of bomb damage 

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Good question.  I guess that the bend in the suction hose would be more severe in that it would have to form a U shape to go up then down over the parapet. I'd be surprised if that didn't work but the fact that the gates are there suggests they are needed.

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1 minute ago, MJG said:

OK I'll stick my neck out and ask.

 

I'm obviously missing something here.... why not just lob the hose over the bridge side??

 

The pumps would still draw the water wouldn't they?

 

Almost certainly yes, but also almost certainly not as well.

The less distance it needs to be lifted the better.

Presumably the arrangements also allow the fire-fighters to stick their heads through, and see that the suction "basket" is well positioned - submerged, but only not enough that it isn't trying to suck silt off the canal bed - harder to do if they have to climb a parapet to see where the hose end has ended up.

I guess it also allows them to check nobody is boating underneath as they lob the hose in - I wouldn't want to get hit by one!

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7 minutes ago, MJG said:

OK I'll stick my neck out and ask.

 

I'm obviously missing something here.... why not just lob the hose over the bridge side??

 

The pumps would still draw the water wouldn't they?

 

A lot of these bridges have high parapets and it may not be apparent that the canal or river is there. Having the bright red door there makes the presence of water behind much more obvious.

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I guess another consideration is that most were put there when most fire tenders had a fraction of the sucking power of today's modern monsters.  Whilst a modern pump could probably drag the water ver the parapet with only a small loss of performance, if if were something even more ancient than a Green Goddess, it may well have been far more on the margins f the equipments capabilities.

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4 minutes ago, alan_fincher said:

I guess another consideration is that most were put there when most fire tenders had a fraction of the sucking power of today's modern monsters.  Whilst a modern pump could probably drag the water ver the parapet with only a small loss of performance, if if were something even more ancient than a Green Goddess, it may well have been far more on the margins f the equipments capabilities.

It doesn't matter how much 'sucking power' they have, you are never going to get more than 33.8 foot of lift

 

Richard

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2 hours ago, RLWP said:

It doesn't matter how much 'sucking power' they have, you are never going to get more than 33.8 foot of lift

 

Richard

<pedant>Slightly more if the water is warm, or the air pressure is high. Slightly less if it is cold, or the pressure is low!</pedant>

Edited by Jen-in-Wellies
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4 hours ago, MJG said:

OK I'll stick my neck out and ask.

 

I'm obviously missing something here.... why not just lob the hose over the bridge side??

 

The pumps would still draw the water wouldn't they?

Have you seen how ridged the flexible suction hose is and how long it would need to be to go from the pump suction up over the railings and then down to the water without being damaged

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2 hours ago, Jen-in-Wellies said:

<pedant>Slightly more if the water is warm, or the air pressure is high. Slightly less if it is cold, or the pressure is low!</pedant>

Go on then, extend your pedantry - what range might you get in Birmingham? The New Main Line is around 490 feet above sea level

 

Richard

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