Introduction: Solar Death Ray (TV Fresnel Lens)
For all of you would-be eco-friendly mad-scientists, I present to you a way to dominate the world! But only on sunny days - THE SOLAR DEATH RAY!
This is simply a free projection lens from the front of an old television, mounted in a wood frame. It's any easy project anyone can build with only simple wood-working skills.
I got this lens from our local electronics recycling center. The public can drop off old televisions, computers, or other electronics for free recycling. I simply used my swiss-army knife to remove the few screws that hold on the bezel, and then slid the lens out. There must have been at least 5 junk projection TVs there when I did this.
The lens is roughly three feet by four feet, with a diagonal of just over 60 inches.
To make the frame, I ran 2x4's through a table saw with the blade depth set to about half an inch. The plastic lens is about 1/8 of an inch, the same thickness as the width of the saw blade.
The 2x4's are then placed around the lens, with a pair of wood screws in each corner to hold the frame together. The wood was left long to act as handles, and make the Death Ray easier to hold and aim.
At this point, I haven't built a stand for the lens, but may in the future. As it is, the Death Ray works well being held by one or two people, and not having a stand discourages leaving the lens in the sun unattended.
This past weekend, we had a children's birthday party, and it was a sunny fall day, so we broke out the Death Ray and melted pennies. Some of my friends are science teachers, and children LOVE to see things like this. (So do the Adults!) Needless to say, there was plenty of adult supervision.
Modern American pennies are mostly Zinc, which has a melting point of about 800 degrees F. They are coated with copper, which has a melting point near 2000 F. We were able to liquify the pennies. An auto-darkening welding helmet worked well to allow me to look directly at the target object and adjust the focus.
The Solar Death Ray is loads of fun! I highly encourage you to make one. Just make sure not to leave it unattended, or where children could use it unsupervised, as it focuses a serious amount of solar energy. I keep this covered with heavy dark cloth if it is outdoors. I store it in my dark garage.
Be safe, and have fun with the SOLAR DEATH RAY!
The Solar Death Ray is now on the Web, Facebook, and YouTube! Come say hello, watch the Solar Death Ray destroy things, and make sure to subscribe!
For more of my recycled backyard fun, please visit http://ecoprojecteer.net
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