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Things You Can Do With A Giant Fresnel Lens
Ant writes "Here is a link where this guy always wanted Edmund Scientific's Giant Fresnel Lens. 'Melts asphalt in seconds!' the ad said. When he went to graduate school he met several other people with the same enthusiasm for aimless destruction through bizarre means, and just enough combined cash to make it happen. Thus the reign of terror began."
Right here: Cooking with Light.
A message from the system administrator: 'I've upped my priority. Now up yours.'
Mount it in front of your monitor for a really big image Write your name in the side of someone's car Wipe your harddrive permanently There has to be a way to increase solar cell output with these (not at direct focus of course mabey larger area at 25% focus)
"It's so convenient to have a system where everyone is a criminal" - A. Hitler
Maybe not very practical, but it might make a good paint remover. I have seen work crews remove paint from wood surfaces with a heat gun that looked like a big hairdryer, so I would think this type of lens would be helpful for stripping paint off metal surfaces such as water towers and so forth.
A love beyond compare...
Chalk actually burns under this thing.
Chalk burns eh? Creative chemistry, more like it. Here's another fun thing you can do: drop your "burnt" chalk in a glass half-full of water, let it bubble, and put your finger in it. Let me know how it feels.
So do aluminum cans. They smell really bad.
Aluminium doesn't smell bad when it burns. I suspect whatever soda pop chemicals remaining in the can do.
It seems that normal concrete will start emitting plumes of smoke just before it pops
As would burning tar, or any other heavy petroleum derivate.
* Mike's car.
Well, not yet. But it's plastic, so it would go up in no time at all. Or maybe we could just shrink-wrap the body around the frame.
Try focusing the lens on the round plastic thing that smells funny, on the rear side of the car...
Seriously, this article is all about playing with a new destructive toy and not much about using the toy in question to do interesting science-related experiments.
I found one of these at my school last year. The first thing I did was take it to the parking lot to set paper on fire. The asphalt under the paper burned. I also melted pennies with it, and it can make holes in soda cans. Is there anything else anyone thinks I should burn with it? it's in my garage.
A perfect example is a laser communication system. A laser beam can be modulated and used to transmit audio. The receiver needs to collect as many photons as possible from the laser transmitter - hence the use of the fresnel lense. Signals can be bounced off clouds - I've heard of transmissions going over 60 miles!
The Amatuer Radio Laser Communications Page has a good primer that has a link to a lot of the basics. And no, you don't need a ham license - although it helps!
This sig seemed like a good idea at the time....
Hanging a Fresnel Lens in front of a white wall projects a nicely focused image of the room onto the wall. Depending on the arrangement of the room and windowage, its poosible to watch the world pass by on projected image. The optimum distance from wall to lens is approximately the focal length (or a little farther if the subject is close to the lens.
Just make sure the sun never gets to the lens or it will burn an arc across the wall.
Two wrongs don't make a right, but three lefts do.
Could you do something serious with this? Put the damn thing in a rig that follows the sun, and a small steam turbine under it, just how much juice could it provide?
I wish I knew the math to this, but damn, if it could provide even a small fraction of the power I use during the daytime... (by this, I mean 5-10%)
Anyone want to impress me with their math/physics skills?
I used to quite enjoy absing ants with a little 5x7 fresnel lens (as well as fireworks, water, a shovel, and, well anything else pretty much). I saw these giant ones in ES and figured they would be the ultimate ant-abuse. You could probably create a fairly wide circle in which the temperature would be sufficient to roast an ant. So rather than zapping them one by one, blanket a colony and watch the burnination.
http://www.noah.org/acidwarp/warper.html
/sarcasm
A frenzel lense + acidwarp = good times in a college dorm room. A 10 foot wide light show on your wall is pretty cool. People seemed to like it but covering your computer with a lense and a cardboard box was a little nerdy.
Or...you cal sell these on eBay!
175" DIRECT BIGSCREEN BIG SCREEN HOME THEATER TV KIT
Sell kits to create 175" large TVs on eBay! The 175" 6.5x Lens Home Theater Kit is amazing! Simply put, it is a Projection unit that when attached to your ordinary TV will project the image up to sizes of 175".
You can get a free Fresnel lens by doing a bit of dumpster diving. If anyone has thrown out a 50" projection TV, the lens is yours!
NOTE: This HAS happened; I am NOT being sarcastic. I took the Fresnel lens out from the trash and stuck it under my bed, wondering what I could do with it. Now I know! (perhaps I should just eBay it for $100)
If this thing is capable of creating such intense heat (with, as far as I can tell, very little environmental impact such as that created when making solar panels) then perhaps it could be used as an alternative (and portable) power source?
I need to look into this. Heat energy can be converted into electric energy, even if it isn't all that efficient.
Useless opinions, worthless observations, and more!
paper-mache' concave surface should do the trick.
Lasers Controlled Games!
I read a paper once that advocated the following strategy for getting to Proxima Centauri in a span of ~50 years. The plan is this:
1) Construct array of solar panels near Mercury (or whatever)
2) Beam resulting gigawatts of power to the Moon using small lasers/masers
3) Collect the power and use it to feed a very large laser
4) Point laser at a huge fresnel lens orbiting Jupiter (say)
5) Point fresnel lens at a solar sail, accelerating it to ~0.1c quite quickly
The lens allows your laser beam to stay focused at long range (like 4 light years). Of course it would take centuries to build the kit needed, but once it's running you can send lots of payloads for little cost (solar sails are 'cheap' to make). There are also solar sail strategies for interstellar return journeys!
I like solar sails, generally. Sustainable space travel!
It sounds cartoonish, but what if someone discovered how to concentrate the suns rays to a specific point on the earth using a similar, but bigger lens.
All that would be needed is a big enough lens and a geostationary satellite, it wont even need to be manned.
Just a thought.
-Xeon
Real programmers can write assembly code in any language. -- Larry Wall
They're building a huge pane of glass on the Australian desert. This pane of glass is supended a few feet off the ground, which is painted black. The air between the glass and the ground is heated, and since hot air rises, it travels toward a chimney at the center of this contraption. As it moves through the chimney, a large turbine generates the necessary power. This odd design works extremely well, but requires very bright, sunny locations that don't mind a glass pane a square mile wide!
This guy did it:
Cockeyed Presents: Incredible Stuff - Mirrored Parabolic Solar Cooker
if the answer isn't violence, neither is your silence / freedom of expression doesn't make it alright
Lucky the fire on the oval was able to be contained, otherwise I would have lost more than my Fresnel lens.
When Argumentum ad Hominem falls short, try Argumentum ad Matrem
this article is interesting because it reminds me of something i read in an old history book on mayan temples. apparently, some of them have rock cut so exactly and perfectly, a knife blade will not fit between the seams. i remember reading (or watching on tv once) about how some scientists/archeologists theorized that the maya used focused sunlight to cut the rock (specifically, big gold encrusted sun discs), and how preposterous others thought of the idea. i even remember that some scientists tried it out once with gold polished mirrors, and it failed utterly. now that we know a giant fresnel lens can burn ashphalt and make concrete crack and pop, i wonder if the maya came up with a similar technique based on a more primitive (or more advanced) fresnel-like lens. anybody want to carve up some rock to test the theory? it would make for some fun mad science to prove an old theory.
While it's very hard to verify this legend, one thing we know for sure is that Syracuse was conquered via land, and Archimedes ingenuity had an important part to play in defending Syracuse from the sea.
So yeah, this is stuff that matters, but hardly "news"
The Raven
this guy always wanted Edmund Scientific's Giant Fresnel Lens.
I grew up about a 45 minute drive from Edmunds Scientific in NJ. I used to get my father to drive me there a couple times per year. I built a telescope, ground the 8" mirror myself, with parts and books I got at Edmunds. I remember the back room full of surplus electronics and optics for cheap, too.
Now I have a 5-year old boy. Damn I miss Edmunds.
Solar furnaces like this one: http://www.imp.cnrs.fr/foursol/1000_en.shtml look like fun too :)
The setup can produce 1000kW of heat in a very small area, and temperatures of up to 4000 Celsius.
I recall reading an article in a Canadian electronics magazine back in the mid 80s where the author created a satellite "dish" based on Fresnel theory. It wasn't a dish at all, but a large plywood Fresnel lens that focused the (C-band) satellite signal onto a feed horn behind the plywood (as opposed to a dish where the feed horn is located in front at the focal point). I don't remember if the plywood was painted with a metallic paint.
I think the mag was Electronics Today and the author may have been Steve Rimmer or David Stringer. Those guys used to do all kinds of crazy things, like mounting a dozen larger speakers (covered with sheet metal) to the front of a VW van and hooking them up to a frequency generator and amplifier. They used this rig to distort the bounced signal from a police radar gun tricking it into displaying a speed of their choice
You could always use the and neutron bomb-boiling water. My mother used to do this to get rid of ants nests and it was a little frightening. Basically a kettle of boiling water kills all the ants instantly.
Sig removed because it was obnoxious
Antabuse was widely perscribed via court order to keep people from drinking. Heck, even listerine would set it off and you'd get violently sick. I've worked in law enforcement for 20 years and I think they quit using it because it was considered "cruel"......well, if it kept them from drinking and getting behind the wheel of a car and killing someone, I think it was a good thing, but the ACLU always thinks otherwise ;)
A 5x mirror is CONVEX. You need a CONCAVE mirror to focus.
Deadly camel spiders? All they can do is scare you or give you a good pinch if you corner one.
Anything that eats scorpions is welcome in my book! My younger brother (who was over in iraq the last time we were there ) used to regale us with tales of how many scorpions were to be found in the desert there, and of the soldier who didn't kick the side of the latrine hard enough before sitting down. When he dangled something below the rim, the scorpion stung it. *empathetic cringe of horror*
My brother was part of a medical chopper unit, the sort of people called for just such an emergency. He said the swelling had to be seen to be believed - and that seeing it caused him to spend a good deal of time beating on the latrine every time he used it through the remainder of his stay in the Gulf!
Thanks, I'll take the Camel Spiders anyday.
*orders up one of the used 11" lenses mentioned in the posting* Thanks for the well-linked post, I've been looking for one this size for years! I've even bookmarked the places where I can get even larger ones in case I get some spare cash anytime soon.
"solar cells still collect juice on slightly cloudy or overcast days, but this method doesn't work nearly as well."
In fact the reverse is true. Infra red penetrates clouds better than visible light so even on cloudy days you can still generate. You simply size the field of mirrors to account for lowered sunlight.
Solar II uses large tanks of hot salt and stores the heat for generation during the evening or very overcast days. It's a far cheaper and more efficient way of generating electricity than photovoltaic cells.
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