Fresnel Lens burns hole, no fire!

F

fiddler

Joined
May 1, 2001
Messages
41
hi guys, just got a fresnel lens and it works wodnerfully to burn holes in just about anything but how do i get it to start a fire and not burn a hole? thanks.

fiddler
 
Once you begin to get good smoke, you have an ignitable ember. Softly blow on the ember to add oxygen and coax it into a flame.

Mike

PS ... B&D ... (B, I assume, is typing) I use a credit card sized one, but just bought a few 4"x6" and shipped them out to Bagheera. He'd be a good one to report on the 4"x6" versions. M
 
i got a credit card size one and have one that is 8" x 8". haven't used that one yet. thought i'd try it with leaves. i think i focused on too small a area. i see smoke and there is a hole. no time to blow on anything. i stacked several leaves together because i thought maybe it would burn through the first one.

it burned through the first one and the rest as well. lol. i think i will try a bigger focus so the temp doesn't get too high.

after that, gonna try and blow a quarter size hole in pavement with the big one. that should be interesting.

fiddler
 
Hey Mike,sometimes its me and sometimes it's the Dog. If you ever see us online ordering Italian beef sandwiches, hold everything but the beef then you know that Dog has control of the mouse.

Just kidding. After Mike recomened the fresnel lens I bought a 4x6. I followed his instruction and focused a dime sized spot and everything that I focused on burst into flame within seconds. I tried dry grass, dry leaves and plant debrie and a wadded up paper towel. I understand that the bigger the lens the more intense the focus spot and that makes sense to me.

It earned a place in my little essentials bag.
 
This works for me, using a credit card sized fresnel lens: Get a big handful if fine tinder such as dry grass. Twist, shred, and rip it to break up the stems and create more surface area. One way is to move your hands as if pedaling a bicycle while holding the grass, etc.

Then hold the clump of stuff in one hand. It should look a sort of like a bird nest. Focus the light into the center of the mass of tinder. You want the heat down in the tinder, not just on the surface. When it starts to smoke, start blowing. It should burst into flames. You have to trap the heat and provide plenty of fuel and air for it to flame.

You can practice with the burning ember or coal from a cigarette. Good luck!
 
I have heard the a fresnel lens can be used for light welding on sheet metal. I don't have one handy at the moment... anybody know if there is any truth to this?
 
don't know about welding but a friend of mine likes to burn holes in sheet metal. don't know what size he used though.

fiddler
 
Bob he is a Cairn Terrier. Bred by the dogmen of the Scottish westhighlands hundreds of years ago. They are small fearless creaures who will defend against insurmountable odds. He has the stamina to hike 10 miles in the high mountains and he tells me if something isn't right. Out in the wild they are in their element. I also have a Jack Russel and they are simply nuclear.

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I bought my fresnel lens at Barns and Noble bookstore. They had three sizes and I got the 4"x6".
 
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