Big lamps

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. 

Working on lighthouses in your spare time now

That won't fit a GU10 base.

ProDave said:

That won't fit a GU10 base.

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The pins on these are 11mm diameter each so with a bit of drilling out of the GU10 holder   :innocent

roys said:

Working on lighthouses in your spare time now

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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 have the baby brother of that with a 1000W lamp.  I haven't used it for donkeys years.

ProDave said:

That won't fit a GU10 base.

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I'll have a google for an adaptor to fit it into a GU10!

e-bay's bound to have something!

:coat

boltonsparky said:

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. 

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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.

SPECIAL LOCATION said:

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.

Click to expand...

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.

Geoff1946 said:

I've been wondering since just how you filter mercury.

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With a mercury filtery thing!

Just googled it

filter paper with a couple of pinholes at the apex

squeeze through a chamois leather

seriously!

kerching said:

Just googled it       filter paper with a couple of pinholes at the apex     squeeze through a chamois leather

seriously!

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I'm usually quick to google, but I thought cleaning mercury too far out to bother.   Perhaps nothing is beyond google!

Geoff1946 said:

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.

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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.

Thank you. I'll bear that in mind if we wander your way sometime.