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Lens Identification?

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Postby beachbum1616 » Sat Feb 18, 2006 6:01 am


I have been contacted by someone who is looking to identify what type of lens he has.

Here is a photo
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and here is the description that was passed along as well.

"It looks like a ships mast light only a lot larger the housing is about 5'5'' tall and about 4' across the bottom. Main housing is steel and hardware is bronze and has 4 fresnel panels about 30'' tall with bronze diagonal bars and general electric cabon arc system in side."

Any of you lens experts have an idea?
Stephen

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Postby boats » Sat Feb 18, 2006 7:50 am


Well its not off any ship I know, I'd say it may be a range light. Is there a name plate with a date. How big is the cabon arc system if it is, I don't see a vent on this lamp, cabon arc is very hot for a small lamp like this one."Boats"
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Postby beachbum1616 » Mon Feb 20, 2006 7:22 pm


Here is some follow-up info.

And also that the glass(fresnel lens)says B.B.T.21B. STAMPED INTO IT. The 1 could be a 7 also not real sure.
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Postby mikev » Tue Feb 21, 2006 6:38 am


Looks like an old buoy light, but are you sure it's carbon arc? Acetylene, maybe? BBT would indicate French manufacture and some age, at least for the glass.
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Postby pioneerpoint » Tue Feb 21, 2006 6:52 am


No i'm not sure but that is what is inside of it now.[/b]
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Postby Optics » Tue Feb 21, 2006 7:28 am


An interesting lens!

This is a lens that was used at airports in the 1920s and early 1930s. It is a 3rd order Fresnel lens mounted in its own lantern - really just a frame and roof. These lenses were sometimes mounted on short fixed towers near the runways and were sometimes mounted in the back of a large truck. They were made by BBT and by Chance Brothers.

http://img419.imageshack.us/img419/3201 ... htchan.jpg
Last edited by Optics on Tue Feb 21, 2006 5:10 pm, edited 1 time in total.
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Postby Hersh » Tue Feb 21, 2006 11:53 am


Good find Tom, I've never heard of such a lighting apparatus. I love the old photo!!
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Postby pioneerpoint » Tue Feb 21, 2006 12:23 pm


ok if this is what it is where would they have mounted it? There is no brackets or holes where the light would swing?Also the frame is diffrent?Where can i research more on this type of light other then what was posted?Where can i research the name tag//id tag?This is the correct number that is on the fresnel lens in the front at top area on the bronze(B.B.T. 21B.)Does anyone know where to search for more information on this company?
And can anyone tell me the value/rarity of this fresnel light.And where to get restored and prices?Thanks to all whom have helped me i can not wait to learn more.
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Postby mikev » Tue Feb 21, 2006 1:08 pm


Tom Tag's the national expert (he's Optics in this thread). You might consult one of his publications on BBT and other lensmakers.

Sure hope that truck wasn't driving along any shorelines, Tom!
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Postby beachbum1616 » Tue Feb 21, 2006 3:44 pm


Here is another photo pioneerpoint passed along to me.

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Postby beachbum1616 » Tue Feb 21, 2006 5:11 pm


A little more info from Jim Woodward to pass along I thought you guys might find interesting.

I won't bore you with all of the details but as air travel began to develop in the late 19-teens airfields were not lit so planes could only safely fly during daylight hours and so traveling time was fairly restricted. In order to help with this problem 2 of the major lighthouse lens manufacturers of the time, BBT (Barbier, Benard & Turenne) of Paris and Chance Bros. in England developed various types of directional lights that could be used at airfields to help planes identify landing spots during the night. This expanded air travel from daylight hours only to 24 hours/day. The first of these devices really looked like lighthouse lenses and one can be seen today at the Wright-Patterson Air Museum in Dayton, OH.

The optic that you have is a little later version and is much more simple and weather resistant than the first models. The big clue in all of this is the arc lamp. Lighthouses in the U. S. didn’t use arc lights due to the heavy power demands and the uncertainty of shore power at remote light stations. And the backup generators used at lighthouses would never have the capacity to operate the arc lights. These types of lights proved to be less than satisfactory and ultimately lead to the invention of the DCB type of airport beacon tat is still in use today at airports and lighthouses. The DCB was invented by the U. S. Lighthouse Service under a development contract issued by the Civil Aeronautics Board in the 1930’s.
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Postby Optics » Tue Feb 21, 2006 5:28 pm


pioneerpoint,

The style you have is probably for mounting on a short tower (10-20 feet tall). You could try looking up old aerodrome (airport) lighting. I don't know if there are any sites, but there should be.

The lens is relatively common, at least overseas. I have seen a few examples. Value is more difficult. If the lens is in very good condition with no or few chips, the lens could be worth anywhere from $3000 to $30000. The USCG does not own these lenses and it is really worth what someone would be willing to pay. Some people say lenses of this size are worth $300,000, but there would be no buyers - so that is meaningless.

BBT stands for Barbier, Benard and Turenne. They were based in Paris and went out of business in 1981. There is almost nothing written about them and nothing on the Internet. I wrote a story about BBT that will appear in the USLHS "Keeper's Log" in the summer issue this year.
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Postby beachbum1616 » Wed Feb 22, 2006 6:29 am


I wanted to send this picture on to be posted because the carbon arc i found(electric arc light museum) looks nothing like this one that is inside my light. This picture is the inside of mine. Also it says on it with tag(photo doesn't come out)GE ELECTRIC ARC LIGHT
I'm really not sure if it was made with it or someone add it later?Thanks again for the help everyone has.


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Postby Optics » Wed Feb 22, 2006 7:26 am


An Arc lamp would have been used in this lens. In the picture I referenced, the big box on the right is the electrical generator to produce the electricity. BBT made their own arc lamps, but if this was used in the US they probably bought the lens from BBT and a GE replacement Arc lamp.
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