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boltonsparky

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The "small" one is 12kw. The large 20kw. Out of some Fresnel lamps. 

The 20kw boasts 5.7M lumens, a life span of 350hours and a price tag of around a grand. 

Both of these are busted. 



 
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Working on lighthouses in your spare time now😀
The below (not my picture) is different to the one that would take the above 20kw lamp but gives you an idea of the kind of size. 

They are behind a glass fresnel lens but incase that breaks there's a wire mesh to catch any exploding glass. The finer meshes you can see on the lamp below are called scrims, used to reduce the output of the light by half a stop, a full stop or two stops. They're made from stainless steel and get incredibly hot in use. 





I paid a visit to the Southstack lighthouse in Wales some years ago, interesting to learn they use a 150w bulb and the lens allows it to be visible some 24 miles out to sea. 

 
I paid a visit to the Southstack lighthouse in Wales some years ago, interesting to learn they use a 150w bulb and the lens allows it to be visible some 24 miles out to sea. 


The high magnification of the Lighthouse lens is one reason why they rotate...  

(and keep rotating in daylight even when the light is off)..

As if direct sunlight hit the lens at a specific angle you have a very high intensity magnifying glass in reverse..

So instead of burning ants, like you did as kid in the garden..

you would overheating and damage the light source.

 
The high magnification of the Lighthouse lens is one reason why they rotate...  

(and keep rotating in daylight even when the light is off)..

As if direct sunlight hit the lens at a specific angle you have a very high intensity magnifying glass in reverse..

So instead of burning ants, like you did as kid in the garden..

you would overheating and damage the light source.
Every day is a school day!

 
Lighthouses are fascinating. I visited one on the north east coast a couple of years ago and learned that the lens structure is floating on mercury as a bearing. It was massive , seen close up, and you could move it with one finger. They also said that the mercury has to be drained and filtered occasionally to remove any dust etc.  I've been wondering since just how you filter mercury.

 
Lighthouses are fascinating. I visited one on the north east coast a couple of years ago and learned that the lens structure is floating on mercury as a bearing. It was massive , seen close up, and you could move it with one finger. They also said that the mercury has to be drained and filtered occasionally to remove any dust etc.  I've been wondering since just how you filter mercury.
They're incredible buildings. Some pictures below of the one we visited. I too was surprised about the size of the lens structure, huge, a lot of chunky glass. There's a huge amount of kit in the building below it to power and run the thing too. 












 
If you are up this way the Lighthouse museum at Fraserborough is worth a visit.  you can go up the old (now disused) lighthouse to see how it worked.  The mechanism to rotate the lens was clockwork driven and part of the lighthouse keepers duty was to wind it up every 20 minutes.  Interspersed with carrying oil up the stairs to the lamp etc.  Sounds like a very physical job.

I don't think many are open to visitors now that they are all automated.

 
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