Wednesday, October 20, 2010

step 11OK - Let's Burn Something!

http://www.instructables.com/id/Giant-Fresnel-Lens-Deathray-An-Experiment-in-Opti/step11/OK-Lets-Burn-Something/ 
step 11OK - Let's Burn Something!
Update: at the suggestion of foobaz utne, I flipped the Fresnel lens around so the ridges are facing the sun, and found a dramatic increase in lens performance. The secondary lens still isn't working right, but I was able to upgrade from melting zinc pennies to liquefying solid copper ones and destroying nickels!

First Test
Inspired by similar Fresnel experiments floating around the net, I decided to try melting a penny. On winter solstice, I found that a zinc penny melts within a minute when held in the focus. Solid copper pennies (from 1982 or earlier) wouldn't melt, but probably would during summer. Copper's melting point is almost 2000oF compared to Zinc's 790oF. See the first row of images for these tests.



Round 2
With the Fresnel lens oriented correctly, I had another crack at melting those coins. The following video and the second row of images shows my results. MUHAHAHAHA!!!



Note: Copper's melting point is about 2000oF, but Nickel's is 2600o. So it's highly possible that only the copper in the coin (75% copper, 25% nickel) melted, resulting in the mutilated pitted surface.
OK - Let\
loading...
i
fresnel52.jpgfresnel51.jpgfresnel54.jpgfresnel65.jpgfresnel59.jpgfresnel61.jpgfresnel67.jpgfresnel62.jpgfresnel63.jpgfresnel64.jpg

No comments: