Organic Fresnel Lens tree stump remover.

[Gary350]

This is my fresnel lens setting on top of a tomato cage. Lens is 20" x 24". As the sun moves across the sky the 5000 degree 1" diameter spot moves across the stump burning a groove in it as it goes. Every day I have to move the lens to one side about 1" and burn another groove. A stump that has been dead a long time burns up quick. If you cut a live tree down you need to let it dry out about 2 months then it will burn good. My lens has 2 pieces broken out of it.

[img]https://i43.photobucket.com/albums/e358/gary350/Fresnel3.jpg[/img]

[img]https://i43.photobucket.com/albums/e358/gary350/Fresnel4.jpg[/img]

A few weeks later and a few rains later it looks like this. Now I can mow over it and don't have to worry about hitting it with the lawn mower blade. Put a little dirt on it and in another month it will be grown up with grass and look like the rest of the yard.

[img]https://i43.photobucket.com/albums/e358/gary350/Fresnel5.jpg[/img]

If you double click the photos they get larger.

You can buy Fresnel Lens. Several people selling them on ebay. Be sure to buy a SPOT lens not Linear lens.

[img]https://hyperphysics.phy-astr.gsu.edu/hbase/geoopt/imggo/fresnel.gif[/img]

[Kisal]

That's interesting! I looks like a sheet of plastic, but is it? Did you make it yourself? Did you use multiple layers of material? I would have loved to have had one of those to get rid of tree stumps in my yard.

[!potatoes!]

just a sheet of plastic, with, as the last pic kind of shows, concentric angled grooves in it. make it work like a lens without having to be 3d...I'm betting it was purchased. too precision to be otherwise.

[tomc]

I like burning out stumps. Still burning out stumps has its hazards (like house fires). IMO there probably is no safe way to burn out a stump un-attended.

I might read all the fine print on your homeowners insurance before leaveing a stump fire un-watched...