Things You Can Do With A Giant Fresnel Lens 469
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."
EEK! (Score:5, Funny)
Re:EEK! (Score:5, Funny)
Re:EEK! (Score:4, Funny)
Burnination (Score:5, Funny)
Re:Burnination (Score:2, Funny)
Re:Burnination (Score:5, Funny)
Aaahh, fun times being a juvenille. My advice to the next generation though - be as mischievious as normal, but don't do anything stupid or anything that will get you thrown in jail. Be intelligent with your "inevitable" delinquency [you call it rebellion] - we've all been there - however don't get anyone hurt or needlessly damage property.
Life is much more exciting as an experienced adult making thousands of dollars a month. Trust me on this one all you guys. Science is fun, but it can also be very dangerous... Be safe - because if you go to jail or die, the guy you hate will likely reproduce and you never will. And that would suck.
Re:Burnination (Score:5, Funny)
My father once caught me making gunpowder using a chem lab kit he'd bought me and an old mortar I'd found in the garage. His first reaction was "Idiot kid!" Then it was "Oh, wait, that's what I used that mortar for when I was a kid. Let me show you how to do it safely." Basically wet the ingredients down so it doesn't accidentally catch fire while you are grinding it. I suspect he'd learned that one the hard way. I'm big on the safety angle with my kids now, too. In my case its a result of an experiment with some gasoline and an Estes rocket engine when I was a teenager.
Re:Burnination (Score:3, Funny)
I'd love to see the attempt at explaining to the cops how you needfully damaged that property...
Re:Burnination (Score:3, Funny)
Now you can burn like......two ants!
Nice picture of a giant fresnel lens in action (Score:5, Interesting)
Re:Nice picture of a giant fresnel lens in action (Score:3, Funny)
Though seeing as how he lets people use it at the burning man festival, he doesn't quite seem like the type to do that... sounds like a very neat guy.
Re:Nice picture of a giant fresnel lens in action (Score:3, Insightful)
I've known or been around a number of geeks who worked for SCO in the old days, and they were all really cool, knowledgeable people. And, I've been sloshed at the Armory a few times. :)
Re:Nice picture of a giant fresnel lens in action (Score:3, Interesting)
Ants (Score:3, Funny)
Re:Ants (Score:5, Funny)
Re:Ants (Score:5, Funny)
That's something I always wanted to try (Score:3, Interesting)
Avoid antabuse at all costs (Score:5, Funny)
Re:Ants (Score:4, Funny)
Re:Ants (Score:3, Funny)
Re:Ants (Score:3, Insightful)
Ideas (Score:3, Interesting)
Re:Ideas (Score:3, Interesting)
I daresay this may be the long sought for absolutely sure method for permanently removing data from a hard drive in such a way that nobody, not even the NSA will be able to recover it.
Job well done, guys!
Re:Ideas (Score:3, Interesting)
Re:Ideas (Score:3, Interesting)
No biggie. Just make some big spots on the platter with a Sharpie. Once a spot gets white hot, the shininess of surrounding material won't matter much.
Re:Ideas (Score:5, Informative)
Re:Ideas (Score:5, Interesting)
In other words, a fresnel lens does not help in terms of energy gathering. On a cost or mass per area, it does.
Re:Ideas (Score:3, Insightful)
Re:Ideas (Score:5, Insightful)
So I agree with timmi. But remember that the ore optics you have in your system, the less light will reach the photovoltaic cell. Optics are not perfect. (By the way, mirrors are lighter than lenses, and are easier to build and control.)
It's being done! (Score:5, Informative)
Overall it works better than solar cells because it's so simple and you harness the heat energy rather than the light itself, but therer's only economy to it on a large scale, you need enough space to get a huge amount of water to constantly boil. Also, it's significantly harder to get this thing working on less-than-ideal days; solar cells still collect juice on slightly cloudy or overcast days, but this method doesn't work nearly as well.
Still, a good way to apply solar energy when in conditions that permit. I'd like to set up a small unit with a fresnel lens and 'boiling globe' to generate hot water (which I'll pump through a radiator) for my house in the winter. The problem I see is with safety, that beam has to be EXACTLY where I want it or I'll burn the house down.
Re:It's being done! (Score:5, Interesting)
Re:It's being done! (Score:5, Informative)
Regular solar arrays need to have panels or mirrors that track the sun - lots of stuff to break over a large area, fancy focusing algorithms and sensors and motors...
Often simple is best with stuff like this - that's how many home solar heating systems work - forget completely replacing the grid, just pipe some water through panels on the roof to heat it up...
Re:It's being done! (Score:3, Interesting)
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 photovol
A good use (Score:3, Interesting)
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.
Re:A good use (Score:2)
Terrorism... (Score:5, Funny)
A use for AOL CD's (Score:5, Funny)
Welcome! You've got fire!
Re:A use for AOL CD's (Score:3, Interesting)
Re:A use for AOL CD's (Score:3, Interesting)
Cockeyed Presents: Incredible Stuff - Mirrored Parabolic Solar Cooker [cockeyed.com]
All we need now are... (Score:5, Funny)
Giant Fresnel Lens ... (Score:5, Funny)
Snap! crackle! pop!
Why waste such a monster on mere ants. I realize there are some of you out who would think of a certain movie and popcorn (lots of popcorn), but you've got to agree this is more unique.
Re:Giant Fresnel Lens ... (Score:2)
So don't eat 'em. But burn away!
Re:Giant Fresnel Lens ... (Score:3, Funny)
Important note from the grammar police...
The phrase "more unique" has recently been replaced by the more concise term "uniquer".
Similarly, the phrase "most unique" is now "uniquest"
Check out the difference between absolute and relative terms
If only I had this as a kid (Score:3, Funny)
Mindless (Score:3, Interesting)
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.
Re:Mindless (Score:3, Interesting)
aw, at least explain for those of us who lack the chemistry knowledge and the stock of burnt chalk what will happen...
Re:Mindless (Score:5, Informative)
Re:Mindless (Score:5, Informative)
Re:Mindless (Score:4, Funny)
Re:Mindless (Score:5, Insightful)
Yeah, and I guess it shouldda been Smiley Captioned for the Humor Impared, too.
...and? (Score:5, Insightful)
It doesn't sound to me like they ever intended to do much science, it sounds like they intended to fuck around and burn shit, which they did with a high degree of success.
Re:Mindless (Score:3, Insightful)
Re:Mindless (Score:5, Informative)
But, onto the other point: many geeks like high amounts of kinetic energy. It's true. Often, this love tuns into the irrational lust for wanton destruction of random objects. Sometimes, something is learned by the results, sometimes not. But it's the journey that's important (fun).
Re:Mindless (Score:4, Funny)
Which leads to my observation that, when presented with a large electromagnet, a REAL geek immediately constructs a railgun
I mean, really. Is there anything more beautifully destructive than a railgun?
popping concrete et al (Score:4, Informative)
As would burning tar, or any other heavy petroleum derivate.
Concrete doesn't contain the slightest amount of petroleum. You're thinking of -asphalt-, which is entirely different.
What smoked was contaminants on the surface of the concrete, and possibly some stabilizers. It popped because of the moisture in the concrete expanded- concrete doesn't handle much except external compression very well.
Aluminium doesn't smell bad when it burns. I suspect whatever soda pop chemicals remaining in the can do.
No, more likely the label ink.
Re:Mindless (Score:4, Insightful)
concrete [reference.com]: "A hard, strong construction material consisting of sand, conglomerate gravel, pebbles, broken stone, or slag in a mortar or cement matrix."
I do not think that word means what you think it means. It seems as if you are confusing concrete with asphalt [reference.com] or tarmac [reference.com](adam).
Guess what, setting shit on fire is fun! If you are relatively responsible about it and don't light shit on fire accidentally and/or let things get out of hand (note: many forest fires grow from the cooking campfires of the incompetent) then really, who are you harming? Well, anyone breathing the vapors. But besides them?
ooh! ooh! (Score:2)
I have one of these. (Score:5, Interesting)
Re:I have one of these. (Score:3, Interesting)
Glass softens and flows not much hotter than the zinc melts. In the article pennies melted in seconds, so glass should be easy.
I know enough about glass to warn you it might explode while heating and cooling. It can even "explode" after it's been cool for a while depending on the annealing. Try small peices over copper.
Re:I have one of these. (Score:4, Funny)
Laser Communications (Score:5, Interesting)
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 [qsl.net] 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!
Hanging wall art (Score:4, Interesting)
Just make sure the sun never gets to the lens or it will burn an arc across the wall.
Oh great (Score:2, Funny)
If you like burning up stuff with a lens... (Score:5, Funny)
Higher standards (Score:2)
Unless you find a way to pull a MacGyver with it and foil some terrorist plot or something I can't say I'm too impressed.
Ben
$99 for the cheap fresnel... (Score:5, Interesting)
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?
Re:$99 for the cheap fresnel... (Score:5, Interesting)
Re:$99 for the cheap fresnel... (Score:5, Informative)
- In bright summer daylight, at noon the sun provides 1200W/m2
- This fresnel lens is 80x100, so captures 1200 * 0.8 = 960W at best
- A good steam engine, with a condenser and exhaust reheater provides has an efficiency of about 30%, so it would give 960 * 0.3 = 288W in mechanical power
- A good alternator, going at its preferred RPM (not necessarily that of the steam engine's prefered RPM, but let's assume) has an efficiency of about 90%, so it would give 288 * 0.9 = 260W
So you'd get 260W in the best possible conditions, in the brightest of days, in summer, at midday. Throw some clouds and, assuming the entire thing doesn't stall and stays at its nominal efficiency (not likely, but let's assume), you get about 6 times less power, so about 43W
In short, you're better off with solar panels: perhaps a little less efficiency for the same price, but more surface and a lot less aggravation.
Re:$99 for the cheap fresnel... (Score:3, Interesting)
Can't you use fresnel along with photvoltaic to improve the power of the photovoltaics? Maybe not this size of fresnel, but smaller, cheaper ones to get a boost on your cells.
I could be wrong...
Re:$99 for the cheap fresnel... (Score:3, Interesting)
If you pair a photovoltaic panel to the same size fresnel lens, no because you'll just have concentrated the same amount of light on a tiny bit of the photovoltaic panel instead of having the same power spread on the entire surface. You can however increase the power to a smaller panel, because then you concentrate on this smaller su
Re:$99 for the cheap fresnel... (Score:3, Interesting)
I came up with a general number -- 1.5 kilowatts, this is about the amount of energy you would need to propel a small car (like a volkswagon beetle, old variety). This is about the same as a small gasoline engine could provide.
While it looks like a lens like this might be able to provide the power, there are a number of issues that need to be addressed.
One is continual focus of the lens. The position o
Would this be possible? (Score:5, Funny)
Or what if you had a few massive ones in space, could you focus enough energy for use in a fusion reactor? You'd amplify all of that free energy and I don't really know what I'm talking about. Perhaps you could attach it to a shark's head.
Re:Would this be possible? (Score:4, Informative)
Possible source of free lenses (Score:5, Informative)
Cooking idea: Take a length of thin all-thread and turn it with a slow motor, with a matching nut fastened to a board so that the all-thread and motor are slowly pulled along. Spear a few hot dogs on the all-thread and set the lens to a medium concentration. Spin up the motor, and the sun will cook the hot dogs in a spiral....
Hmm, The Ant Equivalent (Score:5, Funny)
Imagine kicking over an ant hill, then frying thousands of the little fuckers with each sweep of the beam when they come pouring out. Considering you can melt nickels and cut soda cans in half with this thing, it's possible you can actually [i]glass[/i] that anthill!
Just make sure it's fire ants. Those bastards deserve it...
Re:Hmm, The Ant Equivalent (Score:3, Interesting)
And remember (Score:3, Funny)
The Voice Of Experience, '72 (Score:3, Insightful)
It made a great project, the most sophisticated object I had built up to that point. It blew as a science experiment, since I didn't have a plan of action other than to melt things, nor a thermometer that could measure it's limits. In retrospect a turkey probe might have worked. I did succeed in liquifying a number of types of solder.
I only rated a participation ribbon at the fair, but one of the science teachers took it off of my hands for $75, recouping my (dad's) material expenses and then some.
50-inch Fresnel lens...for free! (Score:3, Interesting)
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)
Possible use as power source? (Score:4, Interesting)
I need to look into this. Heat energy can be converted into electric energy, even if it isn't all that efficient.
another place you can get one.. (Score:5, Informative)
since I repair them for a living, ive actually done this.
its quite fun, but do be careful!
I like using the fresnel from a 60" projection tv the most
I have burned up phone books in no time with it, and I have tried cans, I got one to melt.
next time you see a projection tv in the trash, get the lens.
the lens will be the innermost of the 2 (or 3, if there is a protective screen)
have fun!
So I'm reading this to my wife... (Score:5, Funny)
"But a professor," I try to explain...
"You can't have one."
Obligatory "Death Star" reference (Score:4, Funny)
Glad I'm the first. I think.
Focus energy for interstellar travel (Score:3, Interesting)
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!
build your own spiral fresnel reflector (Score:3, Informative)
Maybe this was the secret (Score:3, Funny)
pfft (Score:4, Funny)
Watch Your Eyes (Score:5, Informative)
One thing that cannot be overstated is the use of eye protection. And, whatever is selected for that application must handle IR as well as visible light. (Nearly all of the UV is absorbed by the plastic the lens is made out of, so it is not much of a factor.)
Using such a lens, to focus solar radiation, can produce power densities equivalent of a Class-IV laser; where the warnings typically read "avoid exposure to direct or scattered radiation". Even if focused to a spot size of 4cm^2--at an estimated 1kW--the power density would still fit 2.5W/mm^2. This is the same level as a 10W laser, with 2mm beam focus.
Granted that the focus is only at one point, it is easy to overlook when scattered radiation--from a "point" source--can be dangerous.
As the article states, use very heavy welding goggles, and maybe have some sunglasses on under those! It is also recommended to ensure that the goggles cover the infrared parts of the spectrum effectively.
Also note: laser safety goggles would be ineffective for this application, due to the fact that they typically use dichros, which typically are not very "wide-band". They reflect very specific wavelengths--very efficiently. But, since solar radiation is very wide-band, a lot of it will still get through.
Re:Watch Your Eyes (Score:4, Informative)
http://yarchive.net/metal/welding_filter_glass.
Re:Watch Your Eyes (Score:3, Funny)
Surprised no one mentioned... (Score:5, Informative)
Cool, but if you want destruction on the cheap (Score:3, Informative)
And how would that work? (Score:3, Interesting)
Childhood Anecdote (Score:3, Interesting)
Lucky the fire on the oval was able to be contained, otherwise I would have lost more than my Fresnel lens.
ancient art of temple building (Score:3, Interesting)
Archimedes (Score:4, Interesting)
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"
Re:Archimedes (Score:3, Insightful)
I think you're right that this story is probably apocryphal. It's hard to imagine that good mirrors would have been inexpensive enough in those days to make this practical. It's also difficult to imagi
Fresnel Lens - not just for light (Score:3, Interesting)
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
solar cell concentrator? (Score:3, Informative)
Re:wtf (Score:4, Informative)