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darryl
01-02-2016, 07:57 PM
Neighbor had me remove some shelving so he could get his car in the garage. Big screen tv right in the way- must go. So what to do with it. I knew there was a front surface mirror in there and I always wanted to get one just to mess with. So there's that- then some projection lenses that I'll probably never use for anything, but what the hay. There's always a noise filter on the incoming power line and I tend to use them in projects these days, so there's that. Got it all ripped apart and now what to do with the cabinet?

Toss all the junk of course, bits and pieces of plastic. Then it hits me- I've wanted for some time now to make a bit of a spray booth so I can paint small things inside the shop. The top part of this cabinet looks like it will make a perfect hood! Chances are that in the next couple days I'll have it mounted to the rafters in the shop- mostly to get it out of the way for now, but pretty much where it will have to be. What was the front will now be facing downwards, giving a hood above and an easy way to make sides and doors. There's a perfect spot at the back for a fan assembly, and an unused vent already there.

Just what I need, another project. But it's something I will make good use of.

RichardG
01-02-2016, 08:07 PM
Isen't the screen a sort of fenaren lens ( big magnifier ) make your on sun furnace.
Rich

AD5MB
01-02-2016, 08:20 PM
Fresnel lens, pronounced Fruh-NELL

darryl
01-02-2016, 08:20 PM
I'll have to look more closely at the screen itself- it has two or three layers and one does appear to have an 'optically functional' surface molded into it. I don't think it's a fresnel lens, it's just designed to give a wider field of view with less loss of brightness off-angle.

But yes, I do have one of those magnifiers that you used to use with smaller tvs. I've had it out in the sun, and you can burn things with it :)

Evan
01-02-2016, 08:28 PM
A Fresnel lens can do many things, not just magnify. It probably is a Fresnel lens.

darryl
01-03-2016, 03:32 AM
Agreed- the only difference is that this is set up to magnify horizontally and not vertically as well.

darryl
01-06-2016, 05:26 PM
Got around to checking out the screen today. One layer is a diverger as I thought, to widen the field of view, but the other layer is indeed a fresnel lens. Just holding it by hand outside I managed to get a focal spot and burn something. Great, just what I need- another way to burn things. Ha ha.

Anyway, I also researched the lens assemblies a bit. Turns out the fluid filling the cavity in front of the picture tubes is ethylene glycol, probably mixed with glycerine. Anti-freeze basically. While it's toxic to ingest, it's not absorbed readily into the skin and can be cleaned up with soap and water. Still one would be careful handling it to not get it into your eyes or breathe vapors, etc. I thought it might be a silicon oil, so I was hesitant to open that can of worms. As it stands, I'm going to seal a piece of glass in place of the picture tube on the middle lens assembly, refill the fluid, and play around with that as a projection lens of all things :)

The lens assembly itself is interesting- it's a Delta 78 with a correction lens before and after a glass lens. I don't know what the F number would be, but it looks like a very fast lens. I might play around with one in front of my camera just to see what will happen.

flylo
01-06-2016, 07:02 PM
Some brands will melt steel. Check out on youtube.

darryl
01-06-2016, 08:06 PM
I'll probably make up a temporary frame to support it, with a few cross pieces to control sag- then I'll find out how tight the focus can be. Right now I can't get a spot to be less than about two inches square, but that was enough to make things smoke.

Just got rid of all the scrap- on the way got someone to cut granite for me, and came home with a more powerful motor for my bandsaw project. Time for a beer- then see if the motor runs-