One last note - As a teacher, thanks so much for including your initial failure, with this project. It's great to be able to show students an example of how we shouldn't always see failures in a negative light, but rather, as learning experiences. It speaks highly of you to have included yours.
Ha! Another physics teacher here! I used discarded satellite dishes... No big deal to cover the concave side with aluminum adhesive strips and make a perfect parabolic mirror! The effect were awsome!
To their credit, the Mythbusters TV show did this all the time. Arguably, their failures were more entertaining than their successes, but each failure (sometimes several in a row) resulted in data for the next attempt.
What's pretty neat about aluminized parabolic reflectors, and "funnel" style solar ovens, is that they can also be used to cool objects as well at night , by radiating the IR energy up into space. Make a container that is very well insulated in relation to conduction and convection, but very transparent to IR, find a part of your yard with a clear shot to the sky, point the reflector straight up and especially on cloudless, dry nights, over night, the contents inside the container will significantly cool in relation to ambient air temps.
An idea that I have been wanting to try is to use a discarded DishTV antenna. Use the same "Space Blanket" foil to glue to the antenna. The antenna is an accurate section of a parabola with off-axis focusing.
Hi..bro ..please can you help me to write the materials that're used to make the blanket mirror..and the steps if you can..because my university requested from us to write a report about it.
I have done that. Found a large one (36") and covered the inside with mylar. We cut many mylar hexagons (4" in diameter) rather than a vacuum. It allowed for a wrinkle free installation with spray glue. The completed mirror put things on fire easily.
Neat idea! I like how you showed your various attempts and what you learned from the failures. When I was a teen, I made a solar stove from a plan I found in a book about solar energy. It consisted of cardboard panels with aluminum foil taped on, and a plywood frame to hold it all together. Certainly not the most elegant thing, but it worked pretty well and I astounded my family by cooking a hamburger with it!
I was playing with these long ago. After several versions I made just two flat rings around 3 feet in diameter. I placed a tire valve into a hole drilled into the rings. Then I took a clear piece and a mirrored piece placed them together and bonded them between the rings so the valve is between the films. Then pump air inside and it inflates like a balloon. The rings keep the lens stable. This can be scaled up quite easily to make giant mirrors. If you wish to replicate this feel free to do so. You may need to add a spacer ring to allow the space for the valve.
I remember seeing this scheme in a drawing of some proposed solar reflectors destined for orbit. They used an inflatable torus for the ring. The thing I like about this is that it can be safely depowered by changing the pressure inside to make a convex mirror.
Love your work too Krasnow.. Home made ruby lasers, electron microscopes and aerogel.. forgetaboutit. Favorite is the examination of supercritical co2.. keep up the good work guys.
interesting points ,if anyone else trying to find out why solar energy for home try Ewans Energy Roadmap (just google it ) ? Ive heard some super things about it and my work buddy got amazing success with it.
Nice work. Space blankets are quite transmissive, and wear very easily. I've used hydroponic mylar for parabolic troughs in the past, it's significantly more reflective, thicker, just as cheap, and a little more durable tho still not enough to just leave outside.
Bought a ten pack on Amazon. I used spray adhesive and glued several gold foil space blankets to a tarp. Tried it out a couple of times and it reduced the temperature under them by 20 degrees. Great to put over your tent when you're camping in the desert. Tried them in the winter too. Hung the tarp inside of my tent by surrounding my sleeping bag. Outside temp was 21 degrees F. Temp inside the tarp 59.
@@midgetman4206 you can put leaves on it and stuff. It’ll still act as a barrier for infrared. Didn’t some murderous hobo hide from police helicopters like that? I forget.
I did a similar thing a few years ago where I stapled down the mylar with a layer of cloth over it in a circle onto a piece of plywood with a hole in it that I attached my shopvac to. Then I inflated it and applied some resin to the cloth, which stuck it to the mylar. After the resin cured in a couple of hours I just cut off the dish with some scissors. It was pretty floppy, but if I added a ring like you did I imagine it would have been fine.
They definitely dont use mylar in grow rooms, at least not mine and it makes no sense for the fact you have to remove and replace every harvest👀 most just use lab grade white board material 👍
Sometimes I wonder if I could have done things differently. Then I remember I probably wouldn't be subscribed to this channel. What a time to be alive.
I hope you see this, I am getting into RTL-SDR. I’ve been thinking about making my own satellite dish. I honestly think I’m gonna do this process. I was watching someone and he mentioned it needed to be a parabolic surface, and then I remembered you making this. I really believe I’m going to do this as the dish to make one myself! I just wanted you to know you’ve given me inspiration!!!
This is beautiful, and a fantastic idea! As a physics teacher myself I will be sure to make one of these as demo pieces for my students. But I would also show your video so they can see the process you used and that initial failure... er... learning experience. Thanks so much!
As a student who can legally be a teacher, I have to mention that you can use different materials, as well. For example, instead of fiberglass, a bit more resin and more layers of paper might work better, or even cardboard, or a mix of both. Instead of mylar, you can use wider rolls of aluminium foil (tinfoil) than those used for cooking. Even aluminium foil for cooking works, for smaller parabolic mirrors, especially for smaller parabolic curvature. You can even make reflective telescopes that way, with paper, tinfoil, and black plastic bags to make the paper tube of the telescope opaque, and have the paper tube hardened by resin, and have enough layers of paper, so it won't easily be crushed.
Great demonstration on how to build your own parabolic mirror. I was considering buying one from Amazon, but not now. I really appreciate comments of failure or "this didn't work like I thought it would.." and then how you fixed it. Keep up the great discoveries for us folks out here in bleachers, watching you. Hartley (garden grove, CA)
To make a telescope, the parabolic curve would have to be much, much shallower to get a longer focal length. Telescopes tend to have f ratios of a minimum of about f/4, and anything up to f/12, meaning the diameter of the mirror is 1/4 or 1/12 the focal length. So for a 1 foot diameter mirror, you want a 4 foot to 12 foot focal length. The mirror shown here seems to have an f ratio of about f/1. To make a shallower curve, you could pour water into the middle of the mylar, stretched over a circular hole. Stretch the mylar out very tightly by clamping with lots of G-clamps over another material to spread the load. It is important to get the tension equal all the way around to get a symmetrical shape. You can check the focal length by shining a torch onto the mirror and trying to get the reflected image of the torch's filament or LED in focus. However, the water will probably affect the focal length, but I haven't done the calculations to work it out. I like the fibreglass idea, but you could probably bond a rigid support to the fibreglass with vertical and horizontal cross brace rib pieces similar to an aeroplane wing construction, before removing the clamps. Then bond those ribs to a solid base and cylindrical side-wall and it will be really rigid. I'm not sure how viable this mylar would be for imaging, as it looks a bit uneven and the reflections look kind of blurry when compared to a polished piece of metal or metalized glass mirror. Another method to consider is metal spinning - spin a large piece of sheet metal and bend using a tool to match a former underneath. I wonder if vacuum-forming (vac-form over a large open hole) could be used with a metal-coated plastic sheet, or maybe you could electroless-plate a normal piece of vac-formed plastic with metal? You could even ditch the vacuum and use heat to make the material sag under its own weight, or use water or sand to weigh it down.
@jimmimak, it seems to me that the curve achieved by the air pressure method in the video must be spherical, rather than parabolic, as the pressure will be exerted perdendicularly to the surface at all points. Continued inflation would lead to a spherical bubble, if the material was elastic enough. Your method of dishing the surface using the weight of water must give a different curve, as the direction of the force applied at all points will remain almost perfectly parallel over the width of the surface, I imagine. I want to think that the curve achieved would be parabolic, but I cannot determine why it should not be a catenary, which is the curve assumed by a cable or thread strung between two points and acted on only by gravity. Do you have any thoughts on this?
If elaborate on this with a thought experiment, I wondered if the focal length of the curve with the water method could be controlled by adding a greater weight of water. That is to say, I imagine the mirror at the bottom of a column of water, however, I think that this puts us back in the position of hydraulic pressure, rather than pneumatic, acting equally over the surface and forming a sherical dish. Does this contradict the idea that the elastic mirror, responding to the pressure applied by water filled only to its brim, might give the parabola we seek? What do you think?
@@leehaelters6182 Interesting ideas. I think you're correct about the hydraulic pressure, but my guess is the difference would be too subtle to notice. Perhaps with a denser material you would get a more noticeable parabola? To make the parabola, I've had a few ideas, but they might be too wacky or extreme as the shape needed is probably more subtle. 1. Very stretchy membrane material like spandex. 2. Material that progressively gets thinner towards the centre. 3. Several layered membranes with holes/apertures in the centre getting progressively smaller. 4. Membrane material with a low elastic limit, so that it plastically deforms? Like bread dough. 5. By heating a piece of plastic more in the centre than at the edge (think vacuum formed plastic). 6. Fill membrane with varying densities of material, more dense in the middle (pitch or sand?), lighter material at the rim (oil?). Oil and water can self separate due to their densities, so maybe that mechanism can be used to get the shape you want.
Very insightful. Also, to electroless coat the plastic, doesn't this involve specialized processes and chemicals , to make a bonding layer on plastic. Yes, can get it in an industry handling this process. Do you have any thoughts onto an alternative, where it can be done by ourselves. Thanks
@@suhass2621 You could try coating the back of a transparent polished material with silver paint. I'm not sure how well it would work, and you might need to try a few different paints. Another option to try might be coating the back of the transparent material with very fine foil or gold leaf, making sure to get rid of any creases. I would apply these after forming the shape so that the coating isn't damaged.
@@Nighthawkinlight Always humbling to see how much energy the sun dumps onto a square meter of the Earth every second, even far from the tropics, despite being 150,000,000km away. Just too bad it's difficult to capture and store all that energy at an industrial scale.
make a round ring to hold the mylar down instead of just epoxy, then you can really put pressure to the mylar. Make the ring just smaller than where you glue and round the edges 2mm radius "so mylar does not tear" then run your fiberglass and fiberglass the ring to the mylar as well. Now you have the stable mirror and you do it all in one process.
Good video. We all wonder if we could use something a different way. Before I found your video, I found my space blanket and thought could it work. My space blanket is a few years old and in good condition You proved the point. Would like to see you cook something with it. Solar cookers & ideas for them have come a long way, I've been following them for many years.
True, but a 2-inch magnifying glass will start a fire too. That's closer to $3. I used to use magnifying lenses to start fires all the time. I got really fast at it.
***** I actually started a fire with a 1-inch magnifying glass in about 10 seconds. Not just a smolder, a flame. I've done it plenty of times, and a 6-inch lens can start a fire within just a couple seconds.
Spinning a fluid or liquid in a round flat container will cause the liquid or fluid to form a Parabolic shape If you use resin once it hardens you have a perfect Parabolic shape or you can use large amount of mercury to make a telescope mirror as long as you keep it spinning. I have used this in making telescope mirrors in a glass furnace to cut down the grinding of mirror for telescopes.
Not bad at all! I like this design better than the one where they temporarily suck the dome in from the rear, yours has a fixed focal point, which makes it better for a lot of applications. Thanks for sharing, the compressed air + fiberglass idea was brilliant!
Pressing the mylar into a satellite dish also works, perhaps drop blanket in warm water first to remove wrinkles. The satellite dish also offers an adjustable mount-fyi. Incidentally, spray mirror is another way to go as well.
I think you'd get a smoother finish if you do a gel coat. Vacuum the resin to get air bubbles out. Pour resin like you did in the center but don't touch it. Let it spread thin and let it set up until hard but still a little tacky and then put some layers of fiberglass as you did. It should be super smooth.
Alternative: A "rotating liquid-metal mirror" automatically makes a perfect parabola, but only while it's spinning. If you instead spin resin (or molten glass or molten aluminum) until it hardens, you've made a smooth parabolic surface (which then must be "corrected" if necessary, polished, and possibly plated with reflective metal). You have to spin a "pan" that closely approximates the paraboloid you want (CNC cut or 3-D printed); the more it departs from perfect, the more liquid you need to cover it. (If the resin floats on water, maybe you could use a plain cylindrical vessel filled with water as the parabolic "pan".) Problems: Air currents could make the parabola slightly imperfect. When the rotation stops, centrifugal force stops, and the shape will change very slightly. Dust, etc can settle on the resin while it hardens.
A working liquid-mirror telescope *(mercury)* was built in 1872, when mechanical engineering became good enough to maintain the required constant rotation speed. I remember reading that the ground vibration from a horse and carriage passing nearby was enough to degrade the image because they didn't have air bearings for maximum isolation. Rotating mercury mirrors were used even in the 2010s, and some are planned.
Nice, but note obvious the resulting shape should be parabolic. Due to the equilibrium between tensions (i.e. blanket and pressures), it rather be closer to a spherical shape. This explains the aberrations we see when you blow smoke at the focal point... but it's a better point because you need a good repartition to heat, e.g. water in there !
Nice video! I was thinking it might be easier to create a high quality mirror without the fibreglass. Just create a box with a circular hole, place the film over the hole, and apply suction to the box. I know it will be more fragile, but the mirror would be near perfect. Also the focal length would be adjustable. There might be some limitations I'm not aware of, but would be interesting to compare the performance of both methods.
In addition to information, great pronunciation, speed of speech and diction! I subscribed to your channel for 2 reasons: for inventions and to practice English. Congratulations on your channel!
If you just need a quick parabolic mirror you can ge a much smoother surface by laying the mylar on a bucket of any sort that is air tight and apply a vacuum you can even use the pressure to adjust the focus
Awesome idea! I suspect matemaematically this should be a catenary, not an exact parabola, but it burns cardboard, so it is close enough! What if you sucked the air out instead of inflating it? I mean, with the circle already in place and closed from the bottom.
I use a hygene mirror in my camp kit for solar ignition. Was cheap and is durable. And will light a match without any issue. The concept of parabolic dishes is excelent and i think there is tons more potential in this we have yet to tap into. Obviously my little mirror wont melt bricks but for a few buck, and for its intended use, its hard to beat
Very cool! I think you might get an even better result by making the circle frame for the mirror first (ensure it is perfectly circular), then gluing the space blanket to that.
When you look into the mylar and see your reflection, is the image crystal clear like it is in your bathroom mirror? If there's any fuzziness at all, then it really won't be suitable as a telescope mirror. Furthermore, the tolerances required for the paraboloid shape are tight in order to get a clear image. But don't despair -- there are other good uses for an approximate paraboloid -- like the solar cooker you've shown. I know that -- in theory -- rotating a shallow dish of liquid will generate a parabolic shape, but the liquid needs to have viscosity high enough to damp out waves and turbulence, and you'd probably need to run it for a while until the final shape is stable. I wondered if a long-curing syrup-like 2-part epoxy, rotating in a shallow dish would solidify into a nice parabolic shape. This could then be used to (1) make a long-distance acoustic spying device or (2) serve as a template for making parabolic surfaces via vacuum forming hot thin plastic sheet.
I know this is a very old vid, but this is a thought experiment I run in my head, ad infinitum: How to make a big mirror for a Dobsonian telescope. There was an article in Popular Science, I believe, which had a great method -- basically a 15"-20" bowl, on an old record turntable with the central spindle removed, filled with very slow setting epoxy. And set the whole thing up on some foam in a place far from traffic or other vibrations. It creates a parabolic surface, the focal distance determined by the RPMs of the turntable. But you still have to send out for silvering. I love to think on ways to achieve such a surface myself. This is a clever solution, I wonder how I could manipulate a space blanket to work with an existing parabolic form?
A telescope mirror has a surface figure that must be accurate to a fraction of a wavelength of light. Given that, the approach of using mylar has a lot of challenges that might be insurmountable. The main one I see is that it's soft so it will deform due to uneven weight of the fiberglass. That will create zones (visible in the video). Secondly, the fabric of the fiberglass will print through. Thirdly, I don't know how smooth the surface of the mylar sheet is so even with a perfect figure there will be a lot of scattering. I think flipping it upside down (concave side up) and displacing a liquid epoxy like you mentioned would be a better approach. you would need a machined ring at the edges to prevent distortions at the edge. You can see some of those in the video. For a solar furnace this thing is brilliant! (Couldn't resist)
My thought would be to make it as a vacuum system -- build the frame, seal it up, add mylar, then pull a vacuum to get an adjustable focal length. The pressure would keep the shape.
What if you used the dish from a satellite tv antenna? It would make a nice rigid form too. Aren't satellite dishes true parabolas? I could be wrong about that though.
mute8s Yes, you should be able to use a sattelite dish. I just meant it would likely be cheaper to build them his way, if you want to have a lot of them.
Or buy reflective Mylar at any hydroponic store, with not a wrinkle on it. Use a Chinese wok to form the parabolic shape or make a mould plug from it. The Mylar sold at hydroponic stores is made to reflect the most spectrum at the highest efficiency for grow rooms. Comes in rolls about 52" by 50 feet and up.
This method might work for making parabolic sound collectors like you see on the sidelines at football games. Nighthawk, maybe you could make one and see how well it picks up distant sounds. Thanks for all your work!
Hmm ...I picked up a snow sled at the end of last season for $1.50... Have been using it to help rake up leaves but I think I'll put my mic on "interview" mode & tape my phone to the middle..!
Now that is an excellent idea as the wavelength is so large that a perfect parabola is not needed. I expect that more layers of fibreglass would help however.
See comment way above regarding the apparent focal length of F 1.0. -waay too shorth, meaning that the focus (point where you're listening) is equal to the lens diameter, or about 3 feet away for this one. Would need a much, much flatter shape, say 50 yards/1 yard lens, so F 50.
you don't need an arduino, you just need a cross made from small solar cells which is attached to the mirror. the solar cell outputs are crosswired to the DC tracking motors and the cross is mounted in a way that the sun isn't shining at the solar cell faces but at the edges. :)
you won't need copper pipes mate.. just get half a barrel, fill with water and aim the lens at near bottom, make sure your barrel can breath a bit.. wont take long and it doesn't need to follow the sun, 1 good hour is more than enough.. this thing can melt metal in not a very long time, water would be stopping your barrel from melting. whwre i am, we don't have electricity so we made 1/4 of a barrel (cut a barrel down and welded it) and connected it to my water tank, i heat water using wood or gas (mainly wood), but those can get expensive.. i need one of these lenses or anything that can focus a big area somehow, those blankets aren't available here. glass is out of the question.. i tend to use a 10m black 1/4 inch garden hose for showering, but you cant make everyone shower with that alone.. need something bigger for the house..
Very easy to make, and it packs some heat! :-) I have to say, the audio quality of your videos is outstanding. I need to look for better audio recording equipment.
Have you tried gluing the blanket to the rim of a shallow tub and then sucking the air out, this should produce a perfect mirror as the is no backing material to distort it and by altering the pressure you can change the focal length.
dude ...clap* amazing really i remember seeing these online about 10 years ago and they are pricey .i use fresnel lens but always wanted a parabolic mirror
Mirascope, concave reflections at a VERY far distance... sees a map in the sky at high contrast... let's call it moon. Present day, look at the "moon". But it's still the map reflected in the sky. Yes.
It was the leak that caused the wrinkly surface of the parabola. You should try using vacuum instead of pressure. The seal around the circumference would reinforce the bond by pulling it tight over the edge instead of pushing it outward (or upward) like lifting up tape or pealing a sticker. So cut a hole in the wood (or preferably good thick plexy) and glue the mylar over the ring of the hole and turn it upside down and coat the mylar in fiber glass and seal a chamber over the mylar and then vacuum the mylar through the hole into the chamber and let it dry under constant, non-leaky vacuum. Or just use a satellite dish coated with glue and vacuum from the back until dry. Super cool video, man ✌️🖖👌
Two things, 1) I have used a solar blanket to shield the sun from south- facing apartments that were experiencing oven- like temperatures unless the air conditioning was on continuously. When stretched tightly over the window, you could see outside perfectly like through mirrored sunglasses. The Mylar film was allowing about 30% of the light through, not the best thing for solar concentration, but I am impressed how it does work in your video. Thin aluminum foil reflects 100% of the light... Could this idea be revisited using this instead? Where can you get a wide enough roll? With the same bonding process to fiberglass, the fragile foil would become a strong structure. 2) With this process, the shape created would not be a parabola, it would be more like the a section of the edge of a balloon, spherical in shape, good enough for the purpose, but less than perfect. Try as you might, but I doubt you get an optical surface that would work for a telescope... What DID work was a spinning dish with reflective mercury placed in it, the liquid automatically forms a perfect parabola, whose curve depends on the speed at which it is spun, but it is obviously constrained to only being able to point straight up... Hmmm, any way this could be used with an epoxy type liquid that is spun until it sets?
Thats exactly how they make very large (8 meter) telescope mirrors. They melt glass and very, very slowly let it cool while spinning it. It takes a couple months.
Excellent! I'm interested in parabolics for solar heat investigations and this looks like the best construction method I've seen so far. Thanks v much. I don't know enough to understand the geometry, so do you know if your inflation shaping method could produce a parabolic trough? If the film was glued down around a long thin rectangle? Hmm, I guess you would have to shape the ends.
Have you gotten anywhere with the use of one as a telescope mirror? That will be tougher of course, but this is seriously interesting. I've made a number of mirros for telescopes and there are some very different designs, like spherical mirros that are pulled into a parabola with a bolt on the bottom. Anyhow, good luck, and I'll be checking back to see your progress. In the meantime think relatively large in diameter, and short in focal length. Both will make for a mirror that doesn't need quite as high quality.
I haven't progressed on this experiment since this video, too busy with other projects. I have plans to get back to it next spring if I can. Lots of ideas to test
The easiest way to do that would be to use something like what he used to draw his circle, stretch Mylar tight over that, and then pull a vacuum on it. That's the method used on some actual telescopes and since you are using air pressure which is completely even over the surface, it will come out perfect
This mirror is not usable as a telescope mirror because it isn't a parabola; any mirror produced by air pressure against a membrane will be spherical in shape, not parabolic. (Think of a soap bubble as an example of a membrane resisting air pressure. It forms a sphere.) This is space blanket mirror is just a segment of a sphere.
@@Nighthawkinlight Have you had a chance to progress further on your astronomical telescope convex mirror? I agree with some of the comments about the correct curvature... this may require a way of monitoring the degree of curvature to achieve the correct focus angle for the telescope you need it for? Not being a very practical guy... it would be great to see an innovator like yourself come up with the solutions before I get my hands dirty!😆 Happy New Year (2019) by the way!
Here is a great improvement idea for your manufacturing process. Use Rubber Cement on the PVC board then layout your space blanket over this, but before inflating it apply Epoxy to your backing ring, set it in place over the space blanket, clamp the ring down lightly enough to allow it to add pressure through to the rubber cement between the PVC sheet and the space blanket, Now apply pressure to the valve stem and create the dome, apply the Fiberglass shell inside the ring and allow this to dry while keeping the air pressure on the valve stem. And I would mount a pipe fitting here instead and attach it to a 5 gallon pressure tank and adjust the output pressure to about 10 lbs., If there are no leaks it will maintain the same pressure to the sheet the entire time while it dries.
The mirror inside the old projection TVs is a nicely stretched distortion free piece of mylar, it helps a lot to start out with a perfectly flat piece on a frame ! now instead of positive pressure, use a satellite dish and vacuum ! attach with a tiny bead of silicone glue, it's so close to being optically correct it will blow your mind ! .... please do this and make a video. The more of us trying, the sooner experimenters will have a great new toy !
The formula for the parabola in terms of focal point is given by: y = x^2/(4 * fp), where fp is the focal point distance you want. What I've found is that if you make a box that 4x4x1, the focal point will be at the surface of the box. If you wanted to "panelize" a solar concentrator, these are the dimensions it has to be. Then you can place your solar receiver at this focal point without too much interference. I want to create this idea with tubes of hot oil circulating into these receivers. We can encase them in the glass that covers it from the rain and dirt, but more importantly, keep the heat in.
Wouldn't a trough type of reflector be better for heating oil in pipes? I think that's what they use in industrial systems that use that method. There's a Diana the Physics Girl video on it, I'm pretty sure.
You're a fan of GreenPowerScience? Love your customization of these products. Some of which I've seen elsewhere and some I've seen here originally. The ones I've seen elsewhere are still cool because of the customization.
It’s sort of like stretching a painter’s canvas. However, I’d hit the face of the frame with the spray adhesive. Start on the centers of the edges and pull at the corners, working slowly from center to corner. Once centers are tight it’s a matter of pulling out the slack/wrinkles. HTH
Thank you for a most interesting video! However: by this method, in 3-D mathematical terms of space geometry, will the outcome be a paraboloid, or rather part of a sphere? Have you compared the longitudinal section to the contours of a parabola cut out of cardboard, to see whether the surface aligns with the mathematical ideal?
Realistically it's probably much closer to a catenary, but I think he's using the term parabolic because parabolic mirrors or lenses are used widely in the applications he talks about. Not to mention that they're so incredibly close to each other that it doesn't matter, especially since it's a space blanket mirror on some fiber glass.
Ahh, so it's used to describe a curve that is shallower than a parabola? Because it's not good if your catenary lines are really hanging down that far X'D
Cool, but how do you know it is an actual paraboloid? and not a sphere/ellipsoid/hyperboloid/catenary(3d)? if anyone's got the equations for that solution it'd be pretty awesome (It looks like a sphere to me).
Hill Top If the title says parabolic I'd expect it to be parabolic, which it might even be, I don't know, but if otherwise, "concave" mirror would be better Just curious if the process actually creates a real paraboloid
I suspect the actual shape is analogous to a catenary, rather than a paraboloid or spherical section. With a true paraboloid, rays parallel to the axis will reflect and intersect at a point, which is nice for clear images. An approximation to a paraboloid (such as a spherical section) will give a focal region, rather than a point, and fuzzier images. But a spherical section will give a wider field of view. If the object is a solar concentrator, rather than imaging, it doesn't really matter, as long as the focal region is smaller than the thing you're trying to heat and the magnification is sufficient.
+n8hfi I agree that it doesn't matter, just curious I don't believe it to be catenary since a catenary requires a constant force acting on one direction through whatever it is, in this case the magnetude of the force is the same but not constant through the surface, but radial, which may indicate spherical, but I am certain that the tension from the borders will distort the shape. I wanna guess Ellipsoid, but got no basis to confirm it.
Green Power Science , Dan, did a similar project years ago. A practical application is for a long distance laser communicator collector-receiver with the light sensor at the focus area. Thumbs up, nice construction methods.
That’s what it’s called when you apply a current to individual charged particles within a cylinder-shaped magnetic field. It’s likely a very small one.
^ same thought goes into survival or just in case scenarios. They are tiny, take up little space, and cheap. They reflect heat. So like a baked potato wrapped in aluminum foil, it keeps the heat in. Same would be done with your body heat in an emergency. Or if you just want an uncomfortable blanket.
+Kamal H They're blankets. You know, to keep you warm. They're air-tight, water-proof, and reflective, so they reflect the infrared leaving your body back in. The real reason they're great though is that they're incredibly thin, meaning they're extremely small and light, whereas a normal blanket would take up much more space and be much heavier.
@@linardsrozitis7667 surprisingly well I haven't scaled it up yet but the few small pieces I have done so far work really good considering the materials used
I've got about an 8' dish taken apart in the back yard. I've been considering going at it with spray glue and tin foil. Just gotta figure out what I'd do with a massive parabolic like that... I wonder if it could get steel up to forging temperature.
8' is a lot, but I don't think it is enough to heat up steel. The Sun is good for ~20 watts per square foot which equates to only 100 Watts of power. Not enough to really forge steel.
You're off on your calculations by quite a lot. Sunlight is closer to 100 watts of energy per square foot. An 8' diameter mirror has about 50 square feet of surface area so total collected wattage is 5,000. It would melt steel to a puddle when focused. It would however be rather unwieldy to use as a forge and would be difficult to use to heat material evenly.
You're right! my error. I was thinking about how much electricity a solar cell makes, not the total energy. 20 Watts/foot is the electrical gain from solar. Considering they are ~22% efficient, your 100/Watt is about right. And I have no idea how I moved the decimal point on the pi*R^2 calculation. Thanks for the correction. It seemed a bit low to me. I should have double checked my work ;)
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One last note - As a teacher, thanks so much for including your initial failure, with this project. It's great to be able to show students an example of how we shouldn't always see failures in a negative light, but rather, as learning experiences. It speaks highly of you to have included yours.
Your students can see their failures in a parabolic light now!
If I were to do something like that I'd have to edit out the "son of a bitch," that inevitably follows that first failure.
Ha! Another physics teacher here! I used discarded satellite dishes... No big deal to cover the concave side with aluminum adhesive strips and make a perfect parabolic mirror! The effect were awsome!
To their credit, the Mythbusters TV show did this all the time. Arguably, their failures were more entertaining than their successes, but each failure (sometimes several in a row) resulted in data for the next attempt.
Success through Failure: The Paradox of Design by Henry Petroski is a great book and his other books as well.
What's pretty neat about aluminized parabolic reflectors, and "funnel" style solar ovens, is that they can also be used to cool objects as well at night , by radiating the IR energy up into space. Make a container that is very well insulated in relation to conduction and convection, but very transparent to IR, find a part of your yard with a clear shot to the sky, point the reflector straight up and especially on cloudless, dry nights, over night, the contents inside the container will significantly cool in relation to ambient air temps.
An idea that I have been wanting to try is to use a discarded DishTV antenna. Use the same "Space Blanket" foil to glue to the antenna. The antenna is an accurate section of a parabola with off-axis focusing.
Hi..bro ..please can you help me to write the materials that're used to make the blanket mirror..and the steps if you can..because my university requested from us to write a report about it.
I have done that. Found a large one (36") and covered the inside with mylar. We cut many mylar hexagons (4" in diameter) rather than a vacuum. It allowed for a wrinkle free installation with spray glue. The completed mirror put things on fire easily.
Neat idea! I like how you showed your various attempts and what you learned from the failures. When I was a teen, I made a solar stove from a plan I found in a book about solar energy. It consisted of cardboard panels with aluminum foil taped on, and a plywood frame to hold it all together. Certainly not the most elegant thing, but it worked pretty well and I astounded my family by cooking a hamburger with it!
Joe Tairei I read that same book as a kid!!! Great stuff!
I was playing with these long ago. After several versions I made just two flat rings around 3 feet in diameter. I placed a tire valve into a hole drilled into the rings. Then I took a clear piece and a mirrored piece placed them together and bonded them between the rings so the valve is between the films. Then pump air inside and it inflates like a balloon. The rings keep the lens stable. This can be scaled up quite easily to make giant mirrors.
If you wish to replicate this feel free to do so.
You may need to add a spacer ring to allow the space for the valve.
I remember seeing this scheme in a drawing of some proposed solar reflectors destined for orbit. They used an inflatable torus for the ring. The thing I like about this is that it can be safely depowered by changing the pressure inside to make a convex mirror.
I love how you uses smoke to show the light! Great video
What is just regular smoke?
Probably a fog machine. Looks amazing when you see the light rays focus to a point.
Love how u speaks
If it was smoke it would probably light on fire its most likely fog
@@helpmeiamenslaved3116 😐
I like that you showed what didn't work and used whatever was available to keep going
Nice! It's great to see the whole project -- including things that didn't work.
Love your work too Krasnow.. Home made ruby lasers, electron microscopes and aerogel.. forgetaboutit. Favorite is the examination of supercritical co2.. keep up the good work guys.
interesting points ,if anyone else trying to find out why solar energy for home try Ewans Energy Roadmap (just google it ) ? Ive heard some super things about it and my work buddy got amazing success with it.
Yeah, I liked the whole trial and errors steps, was quite satisfying to see how perservering brings results.
@@En_theo TRNC
.
I especially love the FAILURES. A lot times I ask, "what if", and it's usually one of these failures that's my answer.
Nice work. Space blankets are quite transmissive, and wear very easily. I've used hydroponic mylar for parabolic troughs in the past, it's significantly more reflective, thicker, just as cheap, and a little more durable tho still not enough to just leave outside.
Bought a ten pack on Amazon. I used spray adhesive and glued several gold foil space blankets to a tarp. Tried it out a couple of times and it reduced the temperature under them by 20 degrees. Great to put over your tent when you're camping in the desert. Tried them in the winter too. Hung the tarp inside of my tent by surrounding my sleeping bag. Outside temp was 21 degrees F. Temp inside the tarp 59.
or when you need to hide from police helicopters and their cheeky thermal vision
@@trollmcclure1884 But the giant shiny thing is visible by our eyes
@@midgetman4206 you can put leaves on it and stuff. It’ll still act as a barrier for infrared. Didn’t some murderous hobo hide from police helicopters like that? I forget.
I did a similar thing a few years ago where I stapled down the mylar with a layer of cloth over it in a circle onto a piece of plywood with a hole in it that I attached my shopvac to. Then I inflated it and applied some resin to the cloth, which stuck it to the mylar. After the resin cured in a couple of hours I just cut off the dish with some scissors. It was pretty floppy, but if I added a ring like you did I imagine it would have been fine.
You should be able to buy a roll of mylar from a hydroponic shop, their used in grow rooms, and won't have creases!
i was always using it for growing cannabis
They definitely dont use mylar in grow rooms, at least not mine and it makes no sense for the fact you have to remove and replace every harvest👀 most just use lab grade white board material 👍
@@Mikemeds420 They definitely do in DIY grow rooms.
Sometimes I wonder if I could have done things differently. Then I remember I probably wouldn't be subscribed to this channel.
What a time to be alive.
nice profile pic
+Random Stranger you talking to yourself??,cool cool
I feel it fam, don't let them nobody's bring you down ya dig
+Random Stranger possibly never run around, and hurt you?
And also it's a bit ironic being a time to be alive when your friend Nagasaki suffered a worse fate
I hope you see this, I am getting into RTL-SDR.
I’ve been thinking about making my own satellite dish. I honestly think I’m gonna do this process. I was watching someone and he mentioned it needed to be a parabolic surface, and then I remembered you making this.
I really believe I’m going to do this as the dish to make one myself! I just wanted you to know you’ve given me inspiration!!!
it was a true pleasure to hear you speak,
and watch you work.
This is one of the coolest DIY videos that I have seen around for creative stuff.
DUDE - this is absolutely awesome. Best creative thinking I've seen in ages.
This is beautiful, and a fantastic idea! As a physics teacher myself I will be sure to make one of these as demo pieces for my students. But I would also show your video so they can see the process you used and that initial failure... er... learning experience. Thanks so much!
As a student who can legally be a teacher, I have to mention that you can use different materials, as well. For example, instead of fiberglass, a bit more resin and more layers of paper might work better, or even cardboard, or a mix of both. Instead of mylar, you can use wider rolls of aluminium foil (tinfoil) than those used for cooking. Even aluminium foil for cooking works, for smaller parabolic mirrors, especially for smaller parabolic curvature. You can even make reflective telescopes that way, with paper, tinfoil, and black plastic bags to make the paper tube of the telescope opaque, and have the paper tube hardened by resin, and have enough layers of paper, so it won't easily be crushed.
Great demonstration on how to build your own parabolic mirror. I was considering buying one from Amazon, but not now. I really appreciate comments of failure or "this didn't work like I thought it would.." and then how you fixed it. Keep up the great discoveries for us folks out here in bleachers, watching you. Hartley (garden grove, CA)
To make a telescope, the parabolic curve would have to be much, much shallower to get a longer focal length. Telescopes tend to have f ratios of a minimum of about f/4, and anything up to f/12, meaning the diameter of the mirror is 1/4 or 1/12 the focal length. So for a 1 foot diameter mirror, you want a 4 foot to 12 foot focal length. The mirror shown here seems to have an f ratio of about f/1.
To make a shallower curve, you could pour water into the middle of the mylar, stretched over a circular hole. Stretch the mylar out very tightly by clamping with lots of G-clamps over another material to spread the load. It is important to get the tension equal all the way around to get a symmetrical shape. You can check the focal length by shining a torch onto the mirror and trying to get the reflected image of the torch's filament or LED in focus. However, the water will probably affect the focal length, but I haven't done the calculations to work it out.
I like the fibreglass idea, but you could probably bond a rigid support to the fibreglass with vertical and horizontal cross brace rib pieces similar to an aeroplane wing construction, before removing the clamps. Then bond those ribs to a solid base and cylindrical side-wall and it will be really rigid.
I'm not sure how viable this mylar would be for imaging, as it looks a bit uneven and the reflections look kind of blurry when compared to a polished piece of metal or metalized glass mirror. Another method to consider is metal spinning - spin a large piece of sheet metal and bend using a tool to match a former underneath. I wonder if vacuum-forming (vac-form over a large open hole) could be used with a metal-coated plastic sheet, or maybe you could electroless-plate a normal piece of vac-formed plastic with metal? You could even ditch the vacuum and use heat to make the material sag under its own weight, or use water or sand to weigh it down.
@jimmimak, it seems to me that the curve achieved by the air pressure method in the video must be spherical, rather than parabolic, as the pressure will be exerted perdendicularly to the surface at all points. Continued inflation would lead to a spherical bubble, if the material was elastic enough. Your method of dishing the surface using the weight of water must give a different curve, as the direction of the force applied at all points will remain almost perfectly parallel
over the width of the surface, I imagine. I want to think that the curve achieved would be parabolic, but I cannot determine why it should not be a catenary, which is the curve assumed by a cable or thread strung between two points and acted on only by gravity. Do you have any thoughts on this?
If elaborate on this with a thought experiment, I wondered if the focal length of the curve with the water method could be controlled by adding a greater weight of water. That is to say, I imagine the mirror at the bottom of a column of water, however, I think that this puts us back in the position of hydraulic pressure, rather than pneumatic, acting equally over the surface and forming a sherical dish. Does this contradict the idea that the elastic mirror, responding to the pressure applied by water filled only to its brim, might give the parabola we seek? What do you think?
@@leehaelters6182 Interesting ideas. I think you're correct about the hydraulic pressure, but my guess is the difference would be too subtle to notice. Perhaps with a denser material you would get a more noticeable parabola?
To make the parabola, I've had a few ideas, but they might be too wacky or extreme as the shape needed is probably more subtle.
1. Very stretchy membrane material like spandex.
2. Material that progressively gets thinner towards the centre.
3. Several layered membranes with holes/apertures in the centre getting progressively smaller.
4. Membrane material with a low elastic limit, so that it plastically deforms? Like bread dough.
5. By heating a piece of plastic more in the centre than at the edge (think vacuum formed plastic).
6. Fill membrane with varying densities of material, more dense in the middle (pitch or sand?), lighter material at the rim (oil?). Oil and water can self separate due to their densities, so maybe that mechanism can be used to get the shape you want.
Very insightful.
Also, to electroless coat the plastic, doesn't this involve specialized processes and chemicals , to make a bonding layer on plastic. Yes, can get it in an industry handling this process.
Do you have any thoughts onto an alternative, where it can be done by ourselves.
Thanks
@@suhass2621 You could try coating the back of a transparent polished material with silver paint. I'm not sure how well it would work, and you might need to try a few different paints. Another option to try might be coating the back of the transparent material with very fine foil or gold leaf, making sure to get rid of any creases. I would apply these after forming the shape so that the coating isn't damaged.
5:40 marriage in one sentence.
Marriage *IS* a sentence!
@@favoritemustard3542 "Some calk secures the ring in place" -- calk sounds like the rooster, cock.
Wooooow
Not if she finds a bigger tube
4:05 looks more realistic :)
That's really cool! How long does it take to set cardboard on fire on a sunny day?
No more than a second or two
@@Nighthawkinlight Always humbling to see how much energy the sun dumps onto a square meter of the Earth every second, even far from the tropics, despite being 150,000,000km away. Just too bad it's difficult to capture and store all that energy at an industrial scale.
Davehax wtf
make a round ring to hold the mylar down instead of just epoxy, then you can really put pressure to the mylar. Make the ring just smaller than where you glue and round the edges 2mm radius "so mylar does not tear" then run your fiberglass and fiberglass the ring to the mylar as well. Now you have the stable mirror and you do it all in one process.
Good congratulations!!
Good video.
We all wonder if we could use something a different way.
Before I found your video, I found my space blanket and thought could it work. My space blanket is a few years old and in good condition
You proved the point.
Would like to see you cook something with it.
Solar cookers & ideas for them have come a long way, I've been following them for many years.
PRICELESS. Larger the radius at this curvature, the more distant the focus point. Can come in handy as alternative protection.
A $1 space blanket...
And $200 of other supplies. Jokes aside pretty cool.
1$ blanket 20$ of wood 10$ of backing 10$ of fencing 20$ of resin seems pretty cool for a mirror that sets stuff on fire
True, but a 2-inch magnifying glass will start a fire too. That's closer to $3.
I used to use magnifying lenses to start fires all the time. I got really fast at it.
*****
I actually started a fire with a 1-inch magnifying glass in about 10 seconds. Not just a smolder, a flame. I've done it plenty of times, and a 6-inch lens can start a fire within just a couple seconds.
*****
Never thought to or tried to, but as that is several thousand degrees my thoughts are that it would take a well-shaped 2-foot lens. :P
*****
I've seen and studied fresnel lenses on and off, actually visited a lighthouse in Oregon that used massive ones. Pretty cool lenses. :)
Spinning a fluid or liquid in a round flat container will cause the liquid or fluid to form a Parabolic shape If you use resin once it hardens you have a perfect Parabolic shape or you can use large amount of mercury to make a telescope mirror as long as you keep it spinning. I have used this in making telescope mirrors in a glass furnace to cut down the grinding of mirror for telescopes.
Was going to comment this.
Make a mold from concrete spinning in a round container
Not bad at all!
I like this design better than the one where they temporarily suck the dome in from the rear, yours has a fixed focal point, which makes it better for a lot of applications. Thanks for sharing, the compressed air + fiberglass idea was brilliant!
Green power science did this many years ago. But used a garbage lid and a vacuum. It's worth a watch too. I like your design also, great work.
Pressing the mylar into a satellite dish also works, perhaps drop blanket in warm water first to remove wrinkles. The satellite dish also offers an adjustable mount-fyi. Incidentally, spray mirror is another way to go as well.
I think you'd get a smoother finish if you do a gel coat. Vacuum the resin to get air bubbles out. Pour resin like you did in the center but don't touch it. Let it spread thin and let it set up until hard but still a little tacky and then put some layers of fiberglass as you did. It should be super smooth.
I think it would be more accurate if the resin is poured first and then inflated the parabola?
absolutely amazing, innovative craftsmanship and video!!!!
Alternative: A "rotating liquid-metal mirror" automatically makes a perfect parabola, but only while it's spinning. If you instead spin resin (or molten glass or molten aluminum) until it hardens, you've made a smooth parabolic surface (which then must be "corrected" if necessary, polished, and possibly plated with reflective metal). You have to spin a "pan" that closely approximates the paraboloid you want (CNC cut or 3-D printed); the more it departs from perfect, the more liquid you need to cover it. (If the resin floats on water, maybe you could use a plain cylindrical vessel filled with water as the parabolic "pan".) Problems: Air currents could make the parabola slightly imperfect. When the rotation stops, centrifugal force stops, and the shape will change very slightly. Dust, etc can settle on the resin while it hardens.
Mercury ought to work. :)
A working liquid-mirror telescope *(mercury)* was built in 1872, when mechanical engineering became good enough to maintain the required constant rotation speed. I remember reading that the ground vibration from a horse and carriage passing nearby was enough to degrade the image because they didn't have air bearings for maximum isolation. Rotating mercury mirrors were used even in the 2010s, and some are planned.
@@quaztron - And again, I am too late. :)
Interesting to know about the use of mercury for that purpose. Thanks for sharing.
@@my_dear_friend_
..But isn't Mercury highly poisonous ?
@@A.Netizen.Since.2010 - Very much so.
The light rays coming down onto that mirror in a cone shape is so beautiful.
The cone shape is not coming down, it is of course, the reflected light going up to the focal point and beyond.
Nice I've used this polyester to reflect sunlight off of windows for years I knew this material was good thank you thank you thank you
Nice, but note obvious the resulting shape should be parabolic. Due to the equilibrium between tensions (i.e. blanket and pressures), it rather be closer to a spherical shape. This explains the aberrations we see when you blow smoke at the focal point... but it's a better point because you need a good repartition to heat, e.g. water in there !
Nice video! I was thinking it might be easier to create a high quality mirror without the fibreglass. Just create a box with a circular hole, place the film over the hole, and apply suction to the box. I know it will be more fragile, but the mirror would be near perfect. Also the focal length would be adjustable. There might be some limitations I'm not aware of, but would be interesting to compare the performance of both methods.
Such a nice project - but hearing about the "square larger in diameter" made my day :D
In addition to information, great pronunciation, speed of speech and diction! I subscribed to your channel for 2 reasons: for inventions and to practice English. Congratulations on your channel!
If you just need a quick parabolic mirror you can ge a much smoother surface by laying the mylar on a bucket of any sort that is air tight and apply a vacuum you can even use the pressure to adjust the focus
I'd love to see more of this telescope project!
Terrific video! Can't wait to try out some of these fantastic DIY ideas. Thanks!
Awesome idea! I suspect matemaematically this should be a catenary, not an exact parabola, but it burns cardboard, so it is close enough!
What if you sucked the air out instead of inflating it? I mean, with the circle already in place and closed from the bottom.
Came here to make the same comment!
It would make it very difficult to fiberglass the inside of the mylar.
Bro thanks.
I saw someone may be you, that did something similar but put the blanket on a frame and did a vacuum
Blessings, I like the video a lot
I use a hygene mirror in my camp kit for solar ignition. Was cheap and is durable. And will light a match without any issue. The concept of parabolic dishes is excelent and i think there is tons more potential in this we have yet to tap into. Obviously my little mirror wont melt bricks but for a few buck, and for its intended use, its hard to beat
Please describe a hygiene mirror and how you start fires with it? I looked up that term and came up with nothing
Very cool! I think you might get an even better result by making the circle frame for the mirror first (ensure it is perfectly circular), then gluing the space blanket to that.
When you look into the mylar and see your reflection, is the image crystal clear like it is in your bathroom mirror? If there's any fuzziness at all, then it really won't be suitable as a telescope mirror. Furthermore, the tolerances required for the paraboloid shape are tight in order to get a clear image. But don't despair -- there are other good uses for an approximate paraboloid -- like the solar cooker you've shown. I know that -- in theory -- rotating a shallow dish of liquid will generate a parabolic shape, but the liquid needs to have viscosity high enough to damp out waves and turbulence, and you'd probably need to run it for a while until the final shape is stable. I wondered if a long-curing syrup-like 2-part epoxy, rotating in a shallow dish would solidify into a nice parabolic shape. This could then be used to (1) make a long-distance acoustic spying device or (2) serve as a template for making parabolic surfaces via vacuum forming hot thin plastic sheet.
Oh this is awesome. Thanks NHIL for posting on my birthday too!
Happy birthday!
Thank you both!
happy birth day
Happy birthday GabeS :-D
Thank you two as well!
I respect people who understand how to do this by themselves
I liked the way you tried making another attempt ......after a lot of hardwork 👍☺️☺️☺️
I know this is a very old vid, but this is a thought experiment I run in my head, ad infinitum: How to make a big mirror for a Dobsonian telescope. There was an article in Popular Science, I believe, which had a great method -- basically a 15"-20" bowl, on an old record turntable with the central spindle removed, filled with very slow setting epoxy. And set the whole thing up on some foam in a place far from traffic or other vibrations. It creates a parabolic surface, the focal distance determined by the RPMs of the turntable. But you still have to send out for silvering. I love to think on ways to achieve such a surface myself. This is a clever solution, I wonder how I could manipulate a space blanket to work with an existing parabolic form?
A telescope mirror has a surface figure that must be accurate to a fraction of a wavelength of light. Given that, the approach of using mylar has a lot of challenges that might be insurmountable. The main one I see is that it's soft so it will deform due to uneven weight of the fiberglass. That will create zones (visible in the video).
Secondly, the fabric of the fiberglass will print through. Thirdly, I don't know how smooth the surface of
the mylar sheet is so even with a perfect figure there will be a lot of scattering.
I think flipping it upside down (concave side up) and displacing a liquid epoxy like you mentioned would
be a better approach. you would need a machined ring at the edges to prevent distortions at the edge.
You can see some of those in the video.
For a solar furnace this thing is brilliant! (Couldn't resist)
chrome paint
My thought would be to make it as a vacuum system -- build the frame, seal it up, add mylar, then pull a vacuum to get an adjustable focal length. The pressure would keep the shape.
You wouldn't be able to cover the back side of the mirror . It would be inside the vacuum chamber.
imagine if you will...a vacuum is pulled inside a bucket with a mylar surface sealed over the opening...
double post: and you keep the vacuum to keep the shape. If you want to change focus you change the pressure.
I believe that is the basic process for how some telescope mirrors are made.
Very good idea!
What if you used the dish from a satellite tv antenna? It would make a nice rigid form too. Aren't satellite dishes true parabolas? I could be wrong about that though.
They are good and rigid, but expensive.
people toss those daily
zasabiibasaz my thoughts exactly. :)
mute8s Yes, you should be able to use a sattelite dish. I just meant it would likely be cheaper to build them his way, if you want to have a lot of them.
Not to mention this process stretches the creases away to make a much smoother finish.
human ingenuity is awesome, at every level, and a lot of work makes the project actually happen...
Or buy reflective Mylar at any hydroponic store, with not a wrinkle on it. Use a Chinese wok to form the parabolic shape or make a mould plug from it. The Mylar sold at hydroponic stores is made to reflect the most spectrum at the highest efficiency for grow rooms. Comes in rolls about 52" by 50 feet and up.
This method might work for making parabolic sound collectors like you see on the sidelines at football games. Nighthawk, maybe you could make one and see how well it picks up distant sounds. Thanks for all your work!
Hmm ...I picked up a
snow sled at the end of last season for
$1.50... Have been using it to help rake up
leaves but I think I'll put my mic
on "interview" mode & tape my
phone to the middle..!
Now that is an excellent idea as the wavelength is so large that a perfect parabola is not needed. I expect that more layers of fibreglass would help however.
See comment way above regarding the apparent focal length of F 1.0. -waay too shorth, meaning that the focus (point where you're listening) is equal to the lens diameter, or about 3 feet away for this one. Would need a much, much flatter shape, say 50 yards/1 yard lens, so F 50.
Next video - make it heat water in copper pipes and make it rotating, to falllow the sun with arduino.
Easier to use black hose :p
you don't need an arduino, you just need a cross made from small solar cells which is attached to the mirror. the solar cell outputs are crosswired to the DC tracking motors and the cross is mounted in a way that the sun isn't shining at the solar cell faces but at the edges. :)
it's almost stupidly simple. no electronics needed at all, not even a battery or power supply!
you won't need copper pipes mate.. just get half a barrel, fill with water and aim the lens at near bottom, make sure your barrel can breath a bit.. wont take long and it doesn't need to follow the sun, 1 good hour is more than enough.. this thing can melt metal in not a very long time, water would be stopping your barrel from melting.
whwre i am, we don't have electricity so we made 1/4 of a barrel (cut a barrel down and welded it) and connected it to my water tank, i heat water using wood or gas (mainly wood), but those can get expensive.. i need one of these lenses or anything that can focus a big area somehow, those blankets aren't available here.
glass is out of the question..
i tend to use a 10m black 1/4 inch garden hose for showering, but you cant make everyone shower with that alone.. need something bigger for the house..
+AA A if you dont have electricity, how did you comment this?
Very easy to make, and it packs some heat! :-) I have to say, the audio quality of your videos is outstanding. I need to look for better audio recording equipment.
Thanks! The Blue Yeti seems to be the youtube standard mic. I use a Shure VP83f which isn't made for vocals specifically but works well.
+NightHawkInLight Thanks!
Hahahaha caulk ring
@@Nighthawkinlight i made my own concave mirror but in a smaller diameter because im gonna use it to my telescope
Have you tried gluing the blanket to the rim of a shallow tub and then sucking the air out, this should produce a perfect mirror as the is no backing material to distort it and by altering the pressure you can change the focal length.
dude ...clap* amazing really i remember seeing these online about 10 years ago and they are pricey .i use fresnel lens but always wanted a parabolic mirror
I have been looking for exactly this spark of genius! Thank you so much!!!
The Brain: "I shall make one the size of the moon & finally conquer Earth!"
Pinky: "I'm hungry & we're out of cheese."
Mirascope, concave reflections at a VERY far distance... sees a map in the sky at high contrast... let's call it moon. Present day, look at the "moon". But it's still the map reflected in the sky. Yes.
Lol great one
Wow!
It was the leak that caused the wrinkly surface of the parabola.
You should try using vacuum instead of pressure. The seal around the circumference would reinforce the bond by pulling it tight over the edge instead of pushing it outward (or upward) like lifting up tape or pealing a sticker.
So cut a hole in the wood (or preferably good thick plexy) and glue the mylar over the ring of the hole and turn it upside down and coat the mylar in fiber glass and seal a chamber over the mylar and then vacuum the mylar through the hole into the chamber and let it dry under constant, non-leaky vacuum.
Or just use a satellite dish coated with glue and vacuum from the back until dry.
Super cool video, man ✌️🖖👌
It is interesting. Excellent method! Thanks
Two things, 1) I have used a solar blanket to shield the sun from south- facing apartments that were experiencing oven- like temperatures unless the air conditioning was on continuously. When stretched tightly over the window, you could see outside perfectly like through mirrored sunglasses. The Mylar film was allowing about 30% of the light through, not the best thing for solar concentration, but I am impressed how it does work in your video. Thin aluminum foil reflects 100% of the light... Could this idea be revisited using this instead? Where can you get a wide enough roll? With the same bonding process to fiberglass, the fragile foil would become a strong structure.
2) With this process, the shape created would not be a parabola, it would be more like the a section of the edge of a balloon, spherical in shape, good enough for the purpose, but less than perfect. Try as you might, but I doubt you get an optical surface that would work for a telescope... What DID work was a spinning dish with reflective mercury placed in it, the liquid automatically forms a perfect parabola, whose curve depends on the speed at which it is spun, but it is obviously constrained to only being able to point straight up... Hmmm, any way this could be used with an epoxy type liquid that is spun until it sets?
Thats exactly how they make very large (8 meter) telescope mirrors. They melt glass and very, very slowly let it cool while spinning it. It takes a couple months.
Excellent! I'm interested in parabolics for solar heat investigations and this looks like the best construction method I've seen so far. Thanks v much. I don't know enough to understand the geometry, so do you know if your inflation shaping method could produce a parabolic trough? If the film was glued down around a long thin rectangle? Hmm, I guess you would have to shape the ends.
Have you gotten anywhere with the use of one as a telescope mirror? That will be tougher of course, but this is seriously interesting. I've made a number of mirros for telescopes and there are some very different designs, like spherical mirros that are pulled into a parabola with a bolt on the bottom. Anyhow, good luck, and I'll be checking back to see your progress. In the meantime think relatively large in diameter, and short in focal length. Both will make for a mirror that doesn't need quite as high quality.
I haven't progressed on this experiment since this video, too busy with other projects. I have plans to get back to it next spring if I can. Lots of ideas to test
The easiest way to do that would be to use something like what he used to draw his circle, stretch Mylar tight over that, and then pull a vacuum on it. That's the method used on some actual telescopes and since you are using air pressure which is completely even over the surface, it will come out perfect
This mirror is not usable as a telescope mirror because it isn't a parabola; any mirror produced by air pressure against a membrane will be spherical in shape, not parabolic. (Think of a soap bubble as an example of a membrane resisting air pressure. It forms a sphere.) This is space blanket mirror is just a segment of a sphere.
+Berkana, yes. Exactly. Thank you for posting this reply.
@@Nighthawkinlight Have you had a chance to progress further on your astronomical telescope convex mirror? I agree with some of the comments about the correct curvature... this may require a way of monitoring the degree of curvature to achieve the correct focus angle for the telescope you need it for? Not being a very practical guy... it would be great to see an innovator like yourself come up with the solutions before I get my hands dirty!😆 Happy New Year (2019) by the way!
You and people like you can solve this world's energy problems. Good work.
Apparently I've been here before because it's already liked and subscribed. I wish I could remember when that was.
Here is a great improvement idea for your manufacturing process. Use Rubber Cement on the PVC board then layout your space blanket over this, but before inflating it apply Epoxy to your backing ring, set it in place over the space blanket, clamp the ring down lightly enough to allow it to add pressure through to the rubber cement between the PVC sheet and the space blanket, Now apply pressure to the valve stem and create the dome, apply the Fiberglass shell inside the ring and allow this to dry while keeping the air pressure on the valve stem. And I would mount a pipe fitting here instead and attach it to a 5 gallon pressure tank and adjust the output pressure to about 10 lbs., If there are no leaks it will maintain the same pressure to the sheet the entire time while it dries.
Time to get six of these, an old crt screen and do some careful math and finally build that heat/death ray I've been wanting to take over the world
you best finish before night time if you want to get anything done
why not use an old Parabolic antenna and put the Space Blankets on ?
Students like us, Who belongs from 3rd world countries,, this type of video is blessings for us.
Peace be upon you❣️
You are a genius, I enjoyed this video. Thank you.
pause at 0:50 and try to find the pink panther
found him lol
RDproductions He's WOKE.
And the neighbors say: NightHawk is signaling his mother ship again.
Interesting. I was thinking of using a space blanket for a box solar oven. Looks like it will work.
The mirror inside the old projection TVs is a nicely stretched distortion free piece of mylar, it helps a lot to start out with a perfectly flat piece on a frame ! now instead of positive pressure, use a satellite dish and vacuum ! attach with a tiny bead of silicone glue, it's so close to being optically correct it will blow your mind ! .... please do this and make a video. The more of us trying, the sooner experimenters will have a great new toy !
The formula for the parabola in terms of focal point is given by: y = x^2/(4 * fp), where fp is the focal point distance you want. What I've found is that if you make a box that 4x4x1, the focal point will be at the surface of the box. If you wanted to "panelize" a solar concentrator, these are the dimensions it has to be. Then you can place your solar receiver at this focal point without too much interference. I want to create this idea with tubes of hot oil circulating into these receivers. We can encase them in the glass that covers it from the rain and dirt, but more importantly, keep the heat in.
Wouldn't a trough type of reflector be better for heating oil in pipes? I think that's what they use in industrial systems that use that method. There's a Diana the Physics Girl video on it, I'm pretty sure.
@@HipNerd yes, the same formula applies too.
NEXT DO FRESNEL LENS PLEASE
What would you like to see with a fresnel lens?
I guess burn stuff
NightHawkInLight
How to make one cheaply and as easy as this!
Yeah that would be awesome, but quite challenging as well, I guess
That would be really difficult. You can buy them though on ebay or amazon in a 5 pack for like $12
“A weight from my work bench” *slaps a brake drum on top of it* 😂
He he he
You're a fan of GreenPowerScience?
Love your customization of these products. Some of which I've seen elsewhere and some I've seen here originally. The ones I've seen elsewhere are still cool because of the customization.
It’s sort of like stretching a painter’s canvas. However, I’d hit the face of the frame with the spray adhesive. Start on the centers of the edges and pull at the corners, working slowly from center to corner. Once centers are tight it’s a matter of pulling out the slack/wrinkles. HTH
This really showcases your genius.
Thank you for a most interesting video! However: by this method, in 3-D mathematical terms of space geometry, will the outcome be a paraboloid, or rather part of a sphere? Have you compared the longitudinal section to the contours of a parabola cut out of cardboard, to see whether the surface aligns with the mathematical ideal?
That's exactly what I said, but then I passed out, woke up with a hangover and slipped in the shower so I forgot to post it first.
is that truly a parabola, or is it a catenary or other shape?
Perhaps a spherical cap? I'm pretty sure it's not a parabola...
Realistically it's probably much closer to a catenary, but I think he's using the term parabolic because parabolic mirrors or lenses are used widely in the applications he talks about. Not to mention that they're so incredibly close to each other that it doesn't matter, especially since it's a space blanket mirror on some fiber glass.
Catenary? Whaaaa... isn't that what some electric trains use?
+Benjamin "Ozias" Esposti
In reference to electric trains, it's the round shape formed by the wires when draped between two poles.
Ahh, so it's used to describe a curve that is shallower than a parabola?
Because it's not good if your catenary lines are really hanging down that far X'D
Cool, but how do you know it is an actual paraboloid? and not a sphere/ellipsoid/hyperboloid/catenary(3d)? if anyone's got the equations for that solution it'd be pretty awesome (It looks like a sphere to me).
I think you're missing the point of the video.
Hill Top If the title says parabolic I'd expect it to be parabolic, which it might even be, I don't know, but if otherwise, "concave" mirror would be better
Just curious if the process actually creates a real paraboloid
I suspect the actual shape is analogous to a catenary, rather than a paraboloid or spherical section. With a true paraboloid, rays parallel to the axis will reflect and intersect at a point, which is nice for clear images. An approximation to a paraboloid (such as a spherical section) will give a focal region, rather than a point, and fuzzier images. But a spherical section will give a wider field of view.
If the object is a solar concentrator, rather than imaging, it doesn't really matter, as long as the focal region is smaller than the thing you're trying to heat and the magnification is sufficient.
+n8hfi I agree that it doesn't matter, just curious
I don't believe it to be catenary since a catenary requires a constant force acting on one direction through whatever it is, in this case the magnetude of the force is the same but not constant through the surface, but radial, which may indicate spherical, but I am certain that the tension from the borders will distort the shape.
I wanna guess Ellipsoid, but got no basis to confirm it.
if you were to make a telescope out of this, it would matter.
Wow,
Super!! Smart moves! Trial and error with the right state of mind
Green Power Science , Dan, did a similar project years ago. A practical application is for a long distance laser communicator collector-receiver with the light sensor at the focus area. Thumbs up, nice construction methods.
Im sorry did you say particle accelerator?
That’s what it’s called when you apply a current to individual charged particles within a cylinder-shaped magnetic field. It’s likely a very small one.
Oh, cool. Let me just go get my space blankets from my garage.
I have 3. They are often sold in survival kits/road kits.. etc.
dirt cheap actually.
they are in like every first aid kit
+TheRolemodel1337 what are their real functionality? Never seen one here in my country
^ same thought goes into survival or just in case scenarios. They are tiny, take up little space, and cheap.
They reflect heat. So like a baked potato wrapped in aluminum foil, it keeps the heat in. Same would be done with your body heat in an emergency.
Or if you just want an uncomfortable blanket.
+Kamal H They're blankets. You know, to keep you warm.
They're air-tight, water-proof, and reflective, so they reflect the infrared leaving your body back in. The real reason they're great though is that they're incredibly thin, meaning they're extremely small and light, whereas a normal blanket would take up much more space and be much heavier.
Did you ever make a telescope mirror using this technique?
I moved on to other projects and haven't circled back around to a telescope yet
@@Nighthawkinlight I think I'm going to give it a try, I'll let you know if it looks promising
@@billroache6244 Any update on how this played out? Im thinking about trying this out too, but with a bit of a different method for the backplate
@@linardsrozitis7667 surprisingly well I haven't scaled it up yet but the few small pieces I have done so far work really good considering the materials used
I liked the video and watched the counter jump from 29K to 30K. Cool!
very well made video. i agree with Applied Science. i wanted to make one, but didn't know where to start. Now I do. Thank you.
Why not use an old, junk satellite dish?
I've got about an 8' dish taken apart in the back yard. I've been considering going at it with spray glue and tin foil. Just gotta figure out what I'd do with a massive parabolic like that... I wonder if it could get steel up to forging temperature.
8' is a lot, but I don't think it is enough to heat up steel. The Sun is good for ~20 watts per square foot which equates to only 100 Watts of power. Not enough to really forge steel.
You're off on your calculations by quite a lot. Sunlight is closer to 100 watts of energy per square foot. An 8' diameter mirror has about 50 square feet of surface area so total collected wattage is 5,000. It would melt steel to a puddle when focused. It would however be rather unwieldy to use as a forge and would be difficult to use to heat material evenly.
You're right! my error. I was thinking about how much electricity a solar cell makes, not the total energy. 20 Watts/foot is the electrical gain from solar. Considering they are ~22% efficient, your 100/Watt is about right. And I have no idea how I moved the decimal point on the pi*R^2 calculation.
Thanks for the correction. It seemed a bit low to me. I should have double checked my work ;)
@ Darwinpasta re: using a parabola to heat steel.
Another problem is, the Sun keeps moving.
Well, I have only been to space during summer, so I have never needed space blankets.
Why did not you just cover a satellite dish with mirror foil?
wouldnt be reflective as the outcome, it has wrinkles and imperfections. good idea though!
Wow. You showed it so easy. This could save the forest.
Wow! Thank you for another well made, informative video. Just imagine the savings these mirrors make over burning fuels.
Awesome!