1941 A DIY Fresnel Lens From Tube
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- čas přidán 27. 06. 2024
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Someone warn the ants !!!
Best comment right here
@@Superstardark LIKE 01
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🔴 [He] who made for you the earth a bed [spread out] and the sky a ceiling and sent down from the sky, rain and brought forth thereby fruits as provision for you. So do not attribute to Allah equals while you know [that there is nothing similar to Him]. ( 2:22 )
🔵 And if you are in doubt about what We have sent down upon Our Servant [Muhammad], then produce a surah the like thereof and call upon your witnesses other than Allah, if you should be truthful. ( 2:23 )
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old overhead projectors had decent fresnel lenses in them
I grab one every chance I get
Also projection TV's as he points to.
I particularly appreciated the newspaper headline at 5:27, @Now Your Cooking With…!” Ha! Well done!
They are in old projection TV's, not LCD TV's. Keep an eye out for them on the kerb on trash day.
Wonderful, just love all these things made from chewing gum and knicker elastic. Great hands on experiments for kids. Thankyou so much.
Years ago on "car talk," a woman called in about something that had gone wrong. She looked under the hood and reasoned that she needed something to hold the thing-a-ma-jig in place. She literally DID strip the elastic out of her underpants (jockey for her had a wide rubber band instead of elastic,and at the time it was encased in a cotton, floating free inside, NOT stitched through with needle and thread, so it was not too difficult a job to strip it out.)
So she managed to get the job done well enough to get into town and to the mechanic.
"Click and Clack" congratulated her on her ingenuity, and then the next caller declared his love for her.
It was a good morning on National Public Radio
Robert, I had a lens that was 4 foot by 4 foot years ago from an experimenter who got the lens from a military auction here in the states for real cheap price. What this thing could do was incredible. Made of glass. When I moved the movers dropped the box and it rolled over sideways and became fifty pounds of shards. SO much for the lens.
My husband has been harvesting the fresnels out of discarded televisions for me for a few years now, and I also have a dozen or so of the page size variety that I picked up at the dollar store, labeled as page magnifiers. I play around with the small ones mostly, simply because they are more managable and easily portable, unlike the larger version. I imagine the glass one was incredible to work with, simply because it is already rigid, and for some reason my mind is telling me the glass would be far more effective and efficient at concentrating the sunlight into a dense single point of focus than the plastic. Perhaps you can tell me if that is true or not?
I have not decided what to build for use of the lenses I now have in my possession, but we are soon planning to move to a remote piece of land where we can discover these new old technologies and enjoy what comforts and conveniences they can be purposed to independently provide us with...at least long enough for the world to recover from this current episode of insanity. Cheers!
@@sourceawry4035 The large lens at high noon will make a 2 ty 4 piece of wood burst into flame when moved slowly across the focal point. We are talking just a few seconds. Just incredible. THere is just no comparison between the plastic as compared to glass one. The negative part is the weight of the glass and the fragile aspect of the item. That is what did in my len, there is no flexing in glass. I wish you luck with your future project
Please keep me in the loop as how the progress of your idea progresses forward.
Peace and good luck too.
Cheers !!
@@victoryfirst2878
Man.. I'm crying for you.
What an awesome lens. Sorry it broke.
I've been collecting old t.v. picture tubes. The screen is curved glass, so if I put two of the screens together, back to back, and fill them with alcohol, it should make a decent lense.
@@melvin6840 I wish you luck Melvin. And yes I still miss my len. Shame they are not for sale as in the past. Good luck Sir with your experiment.
@@victoryfirst2878
Thank you, Victory First.
Yes, I think it will work. I read about a man in France. 1820, or something.
He built a 4ft. lense the same way.
Two, dish shaped, pieces of glass.
Joined at the rim, and filled with wine. (I assume, to keep it from freezing.) Then, put it in a frame on a carriage. With another, smaller lense, at the other end of the carriage, to focus the light even further.
What the book said, is that it would melt rocks at twenty feet.
At 3:35 the focal point is 1+ metre from the "lens". At 5:00 the focal point is a couple of centimetres from the "lens".
Very weird lens, wouldn't call it a fresnel lens though.
Tell him it is a perfect lens - keep his spirits up.
Its definitely a fresnelly
I continue to be amazing at your range and knowledge of so many different things. I could watch you all day and that's actually possible thanks to the several thousand amazing videos you've produced. I strive to be as smart and cool as you one day. I greatly look up to you. Thank you so much for everything you do friend. God bless!
I've seen people use clear plastic bags filled with water ( palm sized ) as fire starters. Concentration of the sun in the palm of your hand as an emergency lens. Seems to work a treat. Can't get cheaper or easier than that.
🤔Any videos to link to?
@@Sedgewise47 I've not tried directly. My views of this were from shows that do 10 ways to start a fire type of content. You should have no problem finding them. Survivalist content providers may have them as well. Hope it helps
@@Sedgewise47 Yes, I have. Found this exact method in a awesome survival video a few years back. Your comment made me recollect the video. The video is called "Making Drinking Water From Trees & Fire From Water - Solo Survival On Deserted An Island - Part 2" by a youtuber named rokkit kit. Around 8 minutes into the video he made fire this way, but the whole series is worth watching tbh.
I've seen it done with urine also. There was a TV show called Dual Survival awhile back.
You can make glasses that way too, for your eyes. And let out the right amount of water so the lens is right for each eye. But have more durable plastic than thin plastic bag. A guy got a design award for it as cheap glasses for the third world you can fit yourself, if you can read the instructions without your glasses.
I really wish it were this easy. If you take another look at the cross section of the Fresnel lens, you see that it's basically a collection of prisms, each one specifically designed to bend the light the right amount to get to the focal point. They progressively sharper as you go out. I'm afraid making a Fresnel takes more that having a series of rings. Each ring needs to be shaped individually. What he's made creates an approximation of the rings, but every ring is just a cylindrical lens.
As for the burning... hrm... There's a lens in the hole of the Fresnel, isn't there? Even a glass Fresnel can't focus light in such a short distance.
why not try it yourself?
@@BlizzyFox He doesn't need too. It's blatantly obvious this is faked to anyone paying attention. Why do think you never saw the lens lifted to see what was in the center? Not the first time this channel has fudged the experiment to 'prove' the result.
@@BlizzyFox It's on my todo list. It would make a nice debunking video.
There is a guy on CZcams who does it with plastic stretched out over a frame puts water on it . makes a perfect lens
yep... old vids.... he's got lot of good stuff ..... hmmm Green something is his vids. Found it. GREENPOWERSCIENCE Not sure why youtube stopped sending me notifications on his stuff. Then again looks like his last vid was year ago.
That said.. this water fresnal lens idea is lighter weight and maybe more manageable?
His name is dan rojas .. I have been following him...the problem with that set up is you cant attach is to a heliostat system... So its okay to show a focal point at a particular place for 2 mins..but realistically it should be for full day
@@abhishekrale2630 see no problem in attaching this to a Heilostat. why do you feel it could not be?
@@coachgeo
I was talking about ''that'' setup..as in with film of plastic and water..as the angle changes the bulge of water will change...I was talking abt the setup with polythene and water
@@abhishekrale2630 ahhhh.. got tya... yeah Dan's would be hard to work in a typical heliostat. Your point of water/bulge moving might could be how to do in a different way though.... as in change Roll Yaw Pitch of plastic sheet till new bulge of water puts focal point back on the surface desired. Would take lot of experimenting to get the mechanism down to control those three axis much less to automate though.
I don't get how this is like a Fresnel lens. A Fresnel lens bends light further from the centre at a higher angle such all light converge at point at some focal distance.
so does this - note the bow in the coil
@@ThinkingandTinkering I understood the bow to be an accidental side effect? I wouldn't expect that to bend the light inwards very much or very precisely. But if that is how it works, perhaps one can improve on the design.
Agreed, the profile one tries to replicate is not a tube but a section of the surface of a lens with a shape that angles more the further away from center you are.
Thanks for the mention for this repeat, and the additional exploration. My "point" of the exercise was a self cooling lens for PV combined with water heating, and perhaps the "bespoke" size from cheap materials.
Would it work with a parabolic backing? I've wondered if a convex fresnel lens over a concave, parabolic reflector might make for a very hot focal point combined with a water pre-heater. Cheers!
long ago came across one picture where a fellow had a buried water tank..... with copper? tubes or bulb of some sort up out of it above the ground. Around this he put combo of lens configured very similar to a Light house lens arrangment so it would get sun from many angles..... and created solar heated water that way. Was not much discussion and only one like it I ever saw. I thought it was genius. Anyway something to think about.
self cooling? please explain that? are you suggesting move water thru it? I dont think tube it will heat up. My understanding is the heat energy moves thru it. UV light might damage (yellow) the plastic tube over time though. Least that is what I recall from old videos from GREENPOWERSCIENCE
Doesn't seem a bad idea, cool the panel with water then use the same water on the way out as a lens before passing it's heat to a cooler body of water that you would like to heat. If the water and panels get too hot, you could always 'drain' the lenses to reduce the effect. I guess the extra power from using a lens goes to pump the water around.
@@threeMetreJim I wonder if in a closed loop if the pressure differential would circulate the water round if you added a reed valve or something similar… 🤔
COOL! Those things are called "axicons," and create a long central hotspot rather than a focus at a particular distance. They form an image, but it stays about the same blurryness as you move the screen in and out. (Conventional Fresnel lenses are made from long curved prisms. If you used long curved cylinder-lenses, or conical segments, then it's an "Axicon" element and not a lens.)
My first thought on the use of clear tubing was to cut tubes in half, keeping natural curve so it will stay flat, then glue down onto a thin sheet of clear plastic or glass. Would have one double the size for same amount of tubing. If glued well, could still fill with water if need be.
Keep it up Sir.
You are a Gem.
I am going to borrow a word from the younger generation. Totally AWESOME! The tube lens may not put any factories out of business but it was super fun to watch.
Mineral oil in glass tube would work the best. You'd get algae and all the rest growing in the pipe if you use water in the long run.
Fluid filled lenses can be actively cooled, so there is good reason to be doing stuff like this in the context of solar.
I can't help but think that Bob was well-known to the Juvenile Firestarter component of his local constabulary force while growing up.
I live videos like this, takes my mind off of things. Puts it on other things. Thanks so much!
Thanks enjoyable presentation, we need things like this, how much did i learn from the old bell systems films , shame they dont do such things today .
You are a genius Sir!!!
I feel a bit better prepared for the zombie apocalypse after watching each oh your videos!
That video was a joy to watch
great! and might also be usefull for diy filming? running a semi cheap led panel through the fresnel as aid for artistic videography
I do wonder how hot this thing gets, if you could for example use one of these to heat up a lump of metal and then use said lump of metal as a thermal battery to run a Stirling engine, you might have a pretty effective low cost generator setup.
Fantastico! 20 anni fa ho comprato 100 m di tubo di plastica trasparente di 5 mm di diametro, ora finalmente mi tornerà utile per provare a costruire una lente di Fresnel , video molto interessante, grazie!!!
Very innovative, thank you sir
I have thought of making lenses out of bubble wrap. Now you have shown that one can inject water into bubble wrap to turn a whole sheet of bubble wrap into a sheet of lenses even though it will be very tedious. Thanks Rob.
could maybe 3d print or DIY a needle array that matches your chosen bubble wrap to attach a bunch of smaller needles to one big syringe?
or hell, I guess if you really wanted to over engineering it, you could basically take half the mechanism of a double mason jar gravity bong, shrink that down so the downspout is a small needle, and make an array of them around a section of pipe such that as it rotates, it aligns with the pattern of your bubble wrap. Much as in the aforementioned bong design, run a smaller diameter fixed pipe through that one, with small holes in the bottom to align with each needle as it passes under it, and all you need from there is a water tight seal at the interface point to keep water from flowing into the rest of the outer pipe, and a jig to pull the bubble wrap sheet under it. In theory, a sensitive enough electronic pressure gauge, and an Arduino or other microcontroller kit could also be used to detect the moment the current bubbles become full in order to almost completely automate the process with a motor and spool pulling the sheet through... but those are more ideas for after proof of concept/prototyping, and here I'm just pontificating.
A bit off center from the topic... But
I remember in a U.S. Magazine article in an issue from the late 70's-early 80's maybe... -Mother Earth News -
Someone made an auto tracker for their fresnel lens hot water system that used automotive freon recharge cylinders (the 6-20+ oz. Cans) one full and one empty on either side of the lens frame! Which was setup in a rudimentary gyro... And it actually tracked the the sun's arc across the sky throughout the day with acceptable accuracy...
Wouldn't mind seeing a video on tracking methods to see how R.M.S. Would approach and maybe improve on low tech tracking...
Excellent info... As ever.
Cheers!
Another favorite of mine is the foil cutting in a coil that then is tightened to give the flat sheet a bit of an angle.
video link please
Cool portable fire starter for camping!
Try solar death ray, aqua lens, tall frame, thick elastic vinyl and few litres of water on the top to make a lens. You can cook food with a double toast pan.
Temperature is soo high that can make holes into the stone. And cam melt any metal up to 3000°C if the water lense gets large enough 1.6 or 1.8m. Try double vinyl to make a super thick clear material. You will melt even TUNGSTEN.
Slick. You could make the spot where the energy is out of metal. I would guess you could make the lens as large as you want. For more than a few hours of operation, you would have to think about keeping things setting up housekeeping in the water... that might be the more difficult problem. Thanks for the demo.
Oh very cool! I never thought tubing could be used like this, but it gives me a chance to mention something that occured to me earlier. Your earlier video on water-gravity battery had me wondering if you could use a "spiral pump" to load said battery. I've made some spiral pumps in the past, and the basic design is quite like your tube-based fresnel lense here. Perhaps the two could be combined in some way. Cheers, thanks for all these really interesting ideas here.
BTW I"m going to put a shout out to you in a game I'm developing here, if you don't mind. I need a reason to explain why some machinery in still operating in a post-apocalyptic world hundreds of years in the future, and I think what I'll do is attribute that to a device you invented that is somehow still keeping the lights on in this game despite most-of-humanity's long-distant demise. I figure I'll just attribute this device to a user with your initials, and when people dissect the game's lore someday, they'll figure it out.
Do you have a devlog going? That sounds fun!
@@evanbarnes9984 No I don't yet but I really should eh... Soon I'll start blogging about it, thanks for the suggestion, i'll post a reply here when i do.
It's a singleplayer game with RPG / base-building / crafting elements kind of like Fallout + Satisfactory + Chrono-Trigger. But with way more arcade-style action. The game is named "Zero Chill", thanks for your comment
Viktor Schauberger?
@@psylentrage I had never heard of him before but that was a fascinating google search, thanks
@@MK-lk7nc @MK-lk7nc There is a good documentary right here on CZcams. If you're interested in spiral pumps, you'll be happy for this find. He's referred to as the Tesla of water
Hmm..3D print or machine a Fresnel mould from materials/filliment with high porosity/ gas permeable properties ( ie. Graphite, PETG etc), then heat an acrylic sheet till malleable and vacuum form onto your Fresnel mould.
Or run the acrylic between two rollers with groove patterns on them. Ideally the rollers would be machined on a lathe. Or 3D printed and then reinforced with epoxy.
Man, I was just drawing this kind of stuff nearly all afternoon. Not for the same reaction, but the spiral has definitely a few uses that aren’t yet very much around. Even tho they are a round.
Cool stuff! Thanks! If you think about it, solar concentrating arrays such as the Crescent Dunes Solar Energy Project can be thought of as a kind of Fresnel lens, or Fresnel mirror might be a more accurate term.
Brilliant as usual,sir.
Not expensive, not mashined, works. What do you want more for fun and amusement.
Using this simple Fresnel lens with photovoltaic sheet to get : either more than 1x of sun and more power by same pv area m2, or same power by less pv area , practice applied are needed !, thanks.
Excelente, una idea increíble y brillante
Great video - thank you. Is it possible to find out which part of the "lens" causes the light concentration to make the heat ?
Your idea of a coil like this reminded me of something that I worked with several years ago. Is there a noticeable heat build up in your coil?
Several years ago, I worked maintenance at a music festival called Shambhala. One of the features of the music festival was that here were public showers available ad to heat the water, we tried to build an off grid system using 2 4'x8' sheets of plywood painted black with an eight foot coil of 1" black pvc pipe attached. The idea was we would aim the setup at the sun and pump water at 80 psi through the pipe to supply the showers with hot water. It worked too well if we aimed it straight at the sun.
We could not push water through the coil fast enough to prevent it boiling. If you turned on just the hot water tap all you got was steam and if more then half of the taps were shut off, it would over pressure and burst the pipes.
Since then, I have often thought of using a setup like this to either power a generator or to use a heat exchange system to use a tank of water as a heat source for a house.
A good example of a Fresnel lens is car tail light.
Back in the mid 80 I was in the Satellite TV business and I would go to various Satellite TV conventions where manufactures would display there products and one product that I remember was a Ku band antenna that was a Fresnel Lens machined into a plate of aluminum I call it a Fresnel lens but it was in realty a Fresnel reflector with the feed horn located in front of the reflector at the focal point. This type of antenna has be surpassed by the Phased Array Antenna like the ones used in StarLink Satellite Internet Systems.
OU SIR YOUR STYLE AND CLEARITY AND SIMPLICITY IN SPEECH IS I LOVE. I FEEL LIKE I WANNA KEEP HEARING YOU FOR FOREVER. ITS TRUE.
Distilled water might work a smidge better. If you had a way to vacuum the air bubbles without sucking the water out it might work a bit better. Very creative. I'll have to give it a try
Robert Murray-Smith.
I have an unrelated idea...
Would you like to try having arc welders in series for making flash graphene? To get the required amps...
And maybe make more and really warm the carbon up, OMG, maybe even invent cabin glass or something...
i learned something new today
I could have used this back in High School
Tube wants to be a cone, just put it in a clear bowl to amplify its lensing effect, maybe two bowls ontop one another with two tubes etc. Bowls/glasses of water can also be used in succession. Or just sheet of something clear with water droplets in uniform/pattern or resin/glass beads/droplets.
This is same as coil of wire, concentrating magnetic field inside coil windings, or place ferrite etc etc etc.
Or set up static/standing wave, creates the ripples, and then hit with secondary/tertiary radiation to cause amplification or use laser in same manner for magnification like optical tweezers.
Even better some fiber optic cables and some quartz prisms
Blinding video 😊
Idea:
Some of your homemade carbon black paint on some cardboard. Place a transparent sheet on top. And your laser cutter.
It might just barely warp one side of the sheet.
If that doesn't work, you can try painting one side of the sheet with something called black 3.0
It's fairly expensive but can be washed off relatively easy. Again, the laser may only etch one side of the sheet, so it might actually create an everted (not inverted) line.
Sir, I think you give meaning to the phrase 'forever young'. Bless you.
Robert, after this you definitely should show how to make magnifying glass from 2 frying pan glass covers connected together and filled with water...
An easier lens to make would be a clear shower curtain suspended in the air then add water on top of it. Makes a big burning lens.
Hello from France !
Maybe someone can build something from this step you have shown here. Thank you for sharing
So...... You've made a video about using your tubing on you tube☺️
You can use the sun twice de lens and the water in tube get heated to and can be used to heat up things if water streams in it.
You could experiment with the tubing to see if it works better as a flat plane or with a parabolic curve in it. This is a very useful tip for me since tubing might be a lot easier to come by than a large Fresnel lens where I live in Brazil.
A fresnel lens that is parabolic, would not be a fresnel lens.
@@sylver369 Well, I mean there's no rule that says it has to be a full-fledged Fresnel lens.
@@jacobopstad5483 There is no rule saying a thing doesn't have to be the thing it is, but can be something else? Where is the logic there? A stapler can't be something else, if it is then it's not a stapler, right?
@@sylver369 I mean there's no rule that you have to use a flat plane of tubing if a parabola of tubing happens to work better. All I'm saying is it's worth testing
@@jacobopstad5483 The old lenses for lighthouses, which were bulky and thick, were parabolic. Many marine museums have them on display. They were abandoned in favor of Fresnel lenses.
Curious about perhaps using a tubing spiral sandwiched between sheets of plexi for support, and filling the tube with optically clear epoxy resin ?
This is fun! I’m curious what will happen if I lay up my tubing in one of those nice formers you showed us. Will it combine or disrupt the lensing from the fresnel effect.
What do you get if you use a clear epoxy resin to cast a thin sheet from the face of your spiral cylindrical lens?
If you just place a mirror underneath will it focus above?
Then fresnel on ground. Pot above on tripod.
I wonder if that natural cone shape actually improves the focus? Simple enough to test, first with the shallow cone shape then flattened.
Another really cool option is to 3D print the optically interesting (jagged) side of the fresnel lense as a negative mold and fill it with clear epoxy resin (molding goes between the epoxy and a table or other level, flat surface). Don't forget a separator. There are special purpose solutions for this, but some forms of wax or thin sheets of some plastics work well. In the latter case, an adhesive between the plastic sheet and molding and vaccum forming them (one of those vaccum sealing kits for food or filament spools works great) first is a necessary step. A little elbow grease and a soft rag is needed to "polish" it when you're done. The optical quality of the result of creating a lense this way is astounding.
That looks like it's a really cool design however my only concern would be is all the bubbles. when it comes to reflecting all that light would that affect anything if it was clear or had the bubbles?
I have 2 salvaged projector TV Fresnel lenses in the garage... I do so want to build a concentrator some day & make hot water or something...
Some possible enhancements might be using an oil with the same index of refraction as the plastic and removing the air from the fluid inside the tube.
I try that asap!
that's quite clever!
Interesting. I wonder if u could fill it with a high proof alcohol to protect from freezing and use it in green houses in the winter.
If you were stranded in some sort of survival situation, but for some reason had clear tubing like this, then it might help make fire. Lol. I can't imagine that situation is very common though
Doesn't this lens focus light outside of the area as much as it focuses light to the center of the area?
I wonder if the fresnel lenses on top and deep parabolic dish underneath combination is a worthwhile contraption for cooking. I love solar cooking but don't want to rely on the size and shape restrictions of using evacuated tubes.
The child in the man never dies!😂
You could probably make it rigid with some resin. Not sure, but you may be able to make a lens just with resin. I think that can take a decent amount of heat as well. You basically made an Archimedes wheel.
That's brilliant, it makes perfect sense, since the tube is a full circle, the correct Fresnel section will be present in each ring, it'll just be a small section of each ring that focuses light on the center, instead of the total area.
Also, this seems like a better method than using a bowl of water to light a fire. Tubing should be added to emergency kits and camping gear.
Or just a common handheld magnifying glass, which is much more effective, easier to handle, and less bulky. This has interesting potential for other larger applications, but not a great option as survival gear.
@@AtomicElf1 sure, or just a fire-starting kit if that's all you need it to do. I was thinking that tubing could be used for many things and it could be filled with something useful. Or if camel-pak tubes were simply clear, then you wouldn't need to rub sticks together in the event that all other options somehow failed and you needed fire to live. One extra option, that's all.
hey, on the subject of water, i was wondering about using it in conjunction with your bullet proof graphene filled plastic... instead of squeezing flat panels in a hydraulic press, i was thinking about putting more complex shapes in a water filled pressure chamber with a pump to jack up the pressure... also dreaming about quickly lowering resin filled molds into the depths of the ocean where the pressure would hopefully be enough to get the job done... figure it would be a good place to knock out cheap carbon reinforced boat hulls...
Mineral oil rather than water, and curve the coil.
Fresnel lenses are found in rear projection TVs, not LCD, and they're rare these days. Can just be bought fairly cheap tho.
Hello Robert! Are you aware of a artist called Theo Jensen? I'm sure you are! But if not I think that you would adore his creations! I'm sure that these inventions will go a long long way in the future maybe this subject will tickle your fancy x
Would wrapping the plastic hose around the lense(centre) of hand held magnifying glass be of any improvement in the concentration of the suns Ray's??
Very interesting. Could we have better efficiency using coiled glass spiral using blown lab glass tube? I strongly recommend the channel Huygen's Optics and there are many others self-grinding lenses for telescopes.
The shape of the Fresnel Lense is very complex. Could we use say cling film over a polycarbonate skeleton to create such a conventional convex lense- or perhaps builder's construction plastic (like the black plastic only thicker? Perhaps we could make a wood master or even 3D printed mould of a Fresnel lens and then use it to draw via vacuum-former high clarity yet thin polycarbonate or Perspex over that and use water as the internal medium?
What if we constructed a medium polygonal Fresnel lense say decahedron or dodecahedron using double-walled polycarbonate roofing? What if we constructed a very large Fresnel lense used corrugated polycarbonate- I am sure the exposed area would more than compensate for shape and thus be cheap yet powerful?
this is how ancient people probably cut stone
So sad that I can't set You more than 1 like.. thanks for the information!
Amazing!
It's counterintuitive that a long cylindrical shape coiled like that would focus towards the centre. Any explanation of how the cross section becomes asymmetrical that way in the process of being coiled around?
Inconsistent volume by the way.
Just out of curiosity...Could it be made out of plastic hexagonal transparent sticks (rods?) used for opening and shutting Venetian blinds ?
My optometrist is still completely oblivious even after years of warnings about weight.
Your burn test with the paoer so close behind involved only a VERY tiny central part of the device. Possibly as little as only the innermost ring. Sone portion of the other inner coils was doing some additional work here, and the outer portion was largely superfluous wastage. The outer region would potentially add some useful energy if the coils were farther away. But then the more efficient action of the central region would be diminished.
In your first check on the degree of light concentration indoors, the considerable diffusion of energy reveals a weak focusing effect indeed. And this is expected because each ring of the coil presents the same cross section to incoming parallel light. Each and every coil has its own focus directly behind the coil and very close to it, of order a centimeter distant.
Past this pattern of best focus close behind and tracing out the coil itself, the light rapidly spreads out thereafter. It's only the circularity of the coil which brings together toward the center some portion of this rapidly spreading light. It's a pseudo focusing action.
This device can be thought of as a sorta-kinda Fresnel in which each and every ring surface has been given the exact same slope. A real Fresnel's ring bevels have different slopes, being sections of an actual lens.
Actually, to be more precise, this feaux Fresnel has all rings being given the same curving cross section of a small lens. That is, you have only created a very long cylindrical lens and wrapped it into a coil. Whatever efficiency it exhibits derives only from the curving of this long cylindrical lens so as to induce some concentration of the dispersing light toward the center of the pattern.
To understand the operation on an elemental level, see what a straight length of vwater-filled tubing does to sunlight. Furthermore, see what difference results from tubing that is compketely transparent versus diffusive.
You can actually buy a plastic Fresnel Lens in car accessories stores, I bought one but it was a convex lens,
i.e. see more things in smaller area.
A healthy Fresnel lens and a smoker's Fresnel lens
Preppers and survivalists say you can use a plastic water bottle, filled with water, as a lens to start a fire, but I have not been able to do it myself. :(
This is a great idea. Cheers.
I wonder if you made a metre long "sausage" about 15-20 diameter wide (deep?) and made it slightly concave, could you concentrate a "stripe" of light?
If only somebody made crystal clear plastic tube that in profile made a triangle and was pre-curved so as to lay down easily into a tight spiral...
That would be awesome.
@Azland Pilot Car 's comment about this exercise being about self cooling lens for PV combined with water heating made me realize just how awesome this idea is, regardless of whether or not it's actually a Fresnel lens or not.
As for the lens itself, since all the tube's cross sections are curved towards the center AND away from it, and since they are all roughly the same curvature, I don't see how that would approximate a Fresnel lens.
I can't argue with the fact that we get a focal point that can scorch a piece of paper, so could someone please enlighten me as to how it actually works?
Thanks
The bad surfaces do not detract from the 'good' ones. Only some of the entire surface of that lens is usefully focusing light.
1:45 Wait you can find these in the back of an LCD TV? That's worth remembering as lots of people have dead TVs they want hauled away.
More like the front screen of the old projector TVs.
I don't know if they still sell them but I bought an A4 size fresnel lens from "The Works". It was only £1 and will easily light paper.
about the small heat issue you mentioned in the end,
wouldn't it be neat to find some cheap additive or alternative liquid that absorbs some light in the infrared spectrum while still transmitting in the visible spectrum, so the lens takes the brunt of the heating? could maybe run a pump off the solar cells for built-in, pre-panel water cooling, or even extend that idea further by then transferring the heat from the fluid to a thermal mass battery etc.
an infrared dye is below the visible spectrum. Big fresnels are very expensive. He is wrong there
I think it would be cool as hell if someone could make and demonstrate a lens like this made of ice. Sure it wouldn't last forever or anything, but I'm sure with modern 3D printing technology there's gotta be a semi-reasonable way to make a proper ice mold.
Also, look up caustic lenses