Safety glasses. yep. I have worked with tools since the beginning. Am a master actually. In my whole time, have tended to snicker at safety goggles. Then I recall, one time. Only once mind you. A wire wheel loaded onto a die grinder/air powered. Had my handy dandy cumbersome vision limiting dusty goggles on over my eyes. This one time, one of the bristles shot off the wheel. Happened so fast I didn't think about it for a sec. This one bristle shot off the wire wheel into the goggles. It would have permanently blinded me in one eye. Wear the goggles... even if nothing ever happens. Cannot replace an eye.
Nice, I’ve tried this with mirror card today, same technique with mixed results. Mind you the card doesn’t have a perfect finish yet still gives a focal point and a heat increase. 👍
I enjoy your videos immensely. I said it before and I'll say it again, you put some science teachers to shame! Had I had you 30 years ago, it would be Christmas everyday coming to your class.
Excellent Dan!! I like the fact that a piece of 4'x4' that can be cut and mounted on a FLAT surface. This sure beats the socks off of using a dish and diddiling with irregular triangles to replace the wire mesh sections.
Great video. Do another video that shows your cutting technique. Also point out that the centre is flat and the angle of the rings increases as they get bigger. You want your test lamp to be as far away as possible if you want to focus to infinity (sun) at a later stage. You could make an initial light scratch from the centre point to the edge before you cut to rings to have a radial mark on each ring.
Hi sir love your work in fresnel lens but I have one doubt that why are you using imaging type fresnel lens which are not suitable for Solar Heating application and why don't you use Non imaging type with metallic rings which is the best way of solar heating and also show us in video if how can we make of Metallic conical fresnel lens which is not available all over the youtube so kindly do a video on how to DIY metallic non imaging fresnel lens for solar application please
The equation relating the radius of your flat ring 'R', the 'overlap' arc length 'L', (both measured midway between the inner and outer radii) and the focal length 'F' is: 2*arccos[2 * pi / (2*pi - L / R) ] + arctan[ 2 * pi * F / (2*pi*R - L) ] = pi / 4. This could probably be simplified, but you can copy it into a grapher application, choose a value for focal length and evaluate the results. Note angles are in radians.
Does this also take into account that the ring diameter will reduce slightly as it is pulled together and does this take into account that the rings are lying flat and not on the height of the parabola. I think it is great to have a formula but it is complex enough to need a spreadsheet to calculate the overlap one can also calculate it analytically. I am going to copy your formula and play with it at some point.
A spiral cut mirror is described in US patent number 4350412: "Fresnel spiral reflector and method for making same". Pictures of this reflector appeared in the October 1981 issue of Popular Science Magazine on page 44.
Hi Dan, Your videos are always worthy of a watch, sometime again. Why not velcro or just staple a few places? If you use every other one you can make two lens! And they will not shade the next outer one as they get steeper. allows a shallower focus vs a taller one. And... On the other side at the foci prime location 180 degrees from the reflective foci, will be another foci! Some gap between rings that lets light through This one is a Fresnel lens instead of a reflector. Same cuts four times the concentration zones! and shorter than wide possible. glass bottle with a soup can inside, measure the steady state temp at each location. I think this is one of your best DIY projects yet because this is so easy to do. It can be done in a classroom for instance.
If your planning on laying the angled rings on a flat surface, that might not work using this method. At least not using every ring without overlap. You might be able to stack them like a parobolic dish though, maybe. Or maybe it will work with overlap.Heres why. Each of those rings cut, share something particular in common. The inner circumference/diameter of one ring, forms the outer of the next adjacent within it, and vice-a-versa. Assumidly, the steepest angle is wanted on the outside, wich means cinching more ring segment. The next ring in would be cinched less. Therfore the outer diamer of the inset ring would be larger than the inner diameter of the ring it sits in. Since they are angled it might still work with overlap, maybe. I don't know for sure, I haven't figured that far yet. I'm not sure if the exposed portions could be aligned properly or not, or if there would be a forever cinching&overlap problem until a ring or few was skipped or different sizes were initialy chosen. I'm going to share what I have figured. The angle of the ring is a function of the proportional length of the circumfral segment, not the radius.The closer you get to using 0 length of the ring's circumference (assumimg you arc one end to touch the other), the closer it gets to 90 degrees. Because the ring wedge gets closer to rectangular, like a piece of paper, then one end would be arc'd (folded) over to touch the other sideThe closer you get to using 100% of the rings circumference length, the closer it gets to lying flat, 0 degrees.Realizing this, I wonder if using half the ring's circumference length would produce 45 degrees. If so, would the pattern hold consistent, 1/3 ring = 1/3 square angle?
If, before you cut rings from the big circle, you draw a wedge from the center of the circle to the outside you will have a measure which represents the amount of mirror to overlap. This could significantly reduce the amount of time spent focusing each ring.
That is a neat idea but I am not convinced that it will form the optimal shape. It might be and well worth calculating or testing if you plan to make a run of these mirrors. The outer segment has to be steeper so it will probably need a larger amount of overlap compared to the inner most ring that remains almost flat. I don't think your idea is optimal. Pre-marking the amount of overlap once you have calculated or measured it once is still a good idea.
This is great! And all the collaborative comments got me thinking... Wouldn't it be simple as pi to drill a hole in the center of your mirored acrylic, mount a dremmel with a cutting wheel on an adjustable arm (like a record baby!), and simply rotate out your rings? 2hrs?! More like 20 minutes! :-) The dowel idea for focusing is brilliant! And using a CNC machine would make this child's play. What about taking a cheap piece of plexiglas and carving rings. Could we make a poor-man's fre
I had forgotten all about fresnel mirrors, thinking only about fresnel lenses. I have access to a laser cutter. I can't cut an angle on the edge, but the laser would cut pretty cleanly.
@christo930 I find that reinforced tape (the tape with the string in it, not duct tape, but clear packing tape) is much stronger and doesn't get gummy the way electrical tape does when it gets hot. Since you would want to put this in the sun, it is going to get hot, especially with it being black, at least try and use white electrical tape so it doesn't absorb so much heat.
I was pouring some molten lead. Had a small sputter (steam?) and caught a droplet of lead with the lens of my prescription glasses (which I only wear sometimes). I was looking at a 1/2 inch "bullet hole" on the lens (no, it just looked like one, it didn't mark the glass lens at all). From that day, I wear goggles (often a face mask instead). Same for ALL shop work, no matter what it is. WEAR GOGGLES.
Perhaps an easy way to get your focal point right is to put a dowel rod on a block with a bright light overhead as you mentioned. The focal point should shine evenly on the dowel rod and make it easy to calibrate each ring to the same focal point.
The most important thing is a ultra smoothenss of the surface to maximize eficiency. Do you know that the mirror in the Hubble telescope is so smooth and even that if it is as wide as the Gulf of Mexico, the waves wont be more than one foot high . Wow! With this kind of mirror ring you got here it bounces a lot of photons off the intended target unseen to your own eyes.. about 10-20% of the photnos will be bounced off the intended target! This is why it is so important to be ultra precise
With a solar heat concentrator there is no need to focus on a pin point. With this setup it is not possible to make the spot smaller than the width of a ring in any event and the flatness of the material is much better the error due to the imperfect curve that will be close to a cone and not a parabola.
Using a light overhead to determine the correct curve will only focus light from that distance. Light from father away will focus at a different point. But if your target is not exactly a point but an object, it might not make a that much of a difference.
You give me an idea ! acrylic mirror is expensive... i think it is possible to realize a cheap mirror by gluing a Mylar survival blanket on cardboard...
if you have a continuum of spacer thickness and you use them in order as they all get pushed inward it forces more curvature, as they get moved out less curvature.
@drorbenami A very quick and simplified answer would be to look up the amount of energy that one can receive in a given area of direct sunlight. You're focusing this amount of light to a point or smaller area. Just because it's focused doesn't mean you're getting more energy. Keep that in mind.This information can be combined with the specific heat capacity of seawater and the latent heat of vaporization. Google or wiki some of that stuff and you'll be on your way! It's simpler than it may look.
it is just , well, a solar art... If you like circles , sure thing.. tiles? why not? They are still all the same.. We can etch micromirrors down to a nanometer in diameter to boost temp well above the nuclear reactor if we want to..
Can you, please leave a shortcut to where i can buy the materials or to at the least has a distribution and name of such materials. I would greatly and respectfully, be waiting on the answer
I've done this for a science project when I was a kid. I tried the tape, but it never worked for me, In the end I drilled holes and used 2 or 3 rivets to hold the pieces together. I presented it as a "Flat Lens". I didn't even know what the heck a fresnel thing was. BTW, circular saw sucks for this, try a scroll saw. Just be careful, a kid in the shop class sawed off a finger with it. Scary stuff...
do you think you could make a video using the fernel mirrors to convert sea water to distilled water? i would like to see: how much distilled water you can get from 1 liter of sea water? and: how long it would take? thanks....
@danz409 This is GreenpowerSCIENCE with emphasis on science and experimentation. Everyone always gets down on Dan for not taking projects to completion. These are springboards for your mind.
what about to find the angle as a function of the radii of the mirror ring and the length of the overlapping area instead of the trial/error to find the focal point?
How about publishing the mathematical formula for determining focal length for a concentric ring IN your video or IN the description? People should know!
cut a section of the circle out and discard it! Use the regular parabola formula to calculate how many degrees of the circle to cut out the further out from the center you go! If your rings are only one inch wide then your ideal object size would be one inch! have fun and be safe!
From Wikipedia: "Augustin-Jean Fresnel (/freɪˈnɛl/, fray-NEL; French: [ɔ.ɡy.stɛ̃ ʒɑ̃ fʁɛ.nɛl]; 10 May 1788 - 14 July 1827) was a French civil engineer and physicist ..."
The calculations are easy. But whenever you design something on paper you end up having to fine-tune the thing anyways once you start working with limited tools and materials. In this case, it pays off to simply not even calculate circle lenghts and angles because you can find out the correct length of the ring simply by shifting the focal point around and measuring where that lays. It is not going to be incredibly small anyways.
Still holding strong 12 years later! One of the few UA-cam OGs left! Hope all is well on your side of the tracks! 😊👍
Safety glasses. yep. I have worked with tools since the beginning. Am a master actually. In my whole time, have tended to snicker at safety goggles. Then I recall, one time. Only once mind you. A wire wheel loaded onto a die grinder/air powered. Had my handy dandy cumbersome vision limiting dusty goggles on over my eyes. This one time, one of the bristles shot off the wheel. Happened so fast I didn't think about it for a sec. This one bristle shot off the wire wheel into the goggles. It would have permanently blinded me in one eye. Wear the goggles... even if nothing ever happens. Cannot replace an eye.
I had my nose pierced by a wire wheel bristle about 5 years back, now I've moved to face shields
Nice, I’ve tried this with mirror card today, same technique with mixed results. Mind you the card doesn’t have a perfect finish yet still gives a focal point and a heat increase. 👍
I enjoy your videos immensely. I said it before and I'll say it again, you put some science teachers to shame! Had I had you 30 years ago, it would be Christmas everyday coming to your class.
Excellent Dan!! I like the fact that a piece of 4'x4' that can be cut and mounted on a FLAT surface. This sure beats the socks off of using a dish and diddiling with irregular triangles to replace the wire mesh sections.
Great video.
Do another video that shows your cutting technique.
Also point out that the centre is flat and the angle of the rings increases as they get bigger.
You want your test lamp to be as far away as possible if you want to focus to infinity (sun) at a later stage.
You could make an initial light scratch from the centre point to the edge before you cut to rings to have a radial mark on each ring.
Hi sir love your work in fresnel lens but I have one doubt that why are you using imaging type fresnel lens which are not suitable for Solar Heating application and why don't you use Non imaging type with metallic rings which is the best way of solar heating and also show us in video if how can we make of Metallic conical fresnel lens which is not available all over the youtube so kindly do a video on how to DIY metallic non imaging fresnel lens for solar application please
Electrical tape when heated up or exposed to sunlight will loose its grip. In long run for sure. I would ad a wire.
Very inspiring. Well done.
Excellent. Good with the comments to get new and old ideas going.
The equation relating the radius of your flat ring 'R', the 'overlap' arc length 'L', (both measured midway between the inner and outer radii) and the focal length 'F' is:
2*arccos[2 * pi / (2*pi - L / R) ] + arctan[ 2 * pi * F / (2*pi*R - L) ] = pi / 4.
This could probably be simplified, but you can copy it into a grapher application, choose a value for focal length and evaluate the results. Note angles are in radians.
Does this also take into account that the ring diameter will reduce slightly as it is pulled together and does this take into account that the rings are lying flat and not on the height of the parabola. I think it is great to have a formula but it is complex enough to need a spreadsheet to calculate the overlap one can also calculate it analytically.
I am going to copy your formula and play with it at some point.
A spiral cut mirror is described in US patent number 4350412:
"Fresnel spiral reflector and method for making same".
Pictures of this reflector appeared in the October 1981 issue of
Popular Science Magazine on page 44.
Hi Dan,
Your videos are always worthy of a watch, sometime again.
Why not velcro or just staple a few places?
If you use every other one you can make two lens!
And they will not shade the next outer one as they get steeper.
allows a shallower focus vs a taller one.
And...
On the other side at the foci prime location 180 degrees from the reflective foci, will be another foci! Some gap between rings that lets light through
This one is a Fresnel lens instead of a reflector.
Same cuts four times the concentration zones!
and shorter than wide possible.
glass bottle with a soup can inside, measure the steady state temp at each location.
I think this is one of your best DIY projects yet because this is so easy to do. It can be done in a classroom for instance.
The spiral idea is worthy of a try, just need to figure out how to mount the spirals with tension as you introduce curvature on the outside.
Would a spiral cut mirror arrange into a Fresnel lens if it were twisted?
If your planning on laying the angled rings on a flat surface, that might not work using this method. At least not using every ring without overlap. You might be able to stack them like a parobolic dish though, maybe. Or maybe it will work with overlap.Heres why. Each of those rings cut, share something particular in common. The inner circumference/diameter of one ring, forms the outer of the next adjacent within it, and vice-a-versa. Assumidly, the steepest angle is wanted on the outside, wich means cinching more ring segment. The next ring in would be cinched less. Therfore the outer diamer of the inset ring would be larger than the inner diameter of the ring it sits in. Since they are angled it might still work with overlap, maybe. I don't know for sure, I haven't figured that far yet. I'm not sure if the exposed portions could be aligned properly or not, or if there would be a forever cinching&overlap problem until a ring or few was skipped or different sizes were initialy chosen. I'm going to share what I have figured. The angle of the ring is a function of the proportional length of the circumfral segment, not the radius.The closer you get to using 0 length of the ring's circumference (assumimg you arc one end to touch the other), the closer it gets to 90 degrees. Because the ring wedge gets closer to rectangular, like a piece of paper, then one end would be arc'd (folded) over to touch the other sideThe closer you get to using 100% of the rings circumference length, the closer it gets to lying flat, 0 degrees.Realizing this, I wonder if using half the ring's circumference length would produce 45 degrees. If so, would the pattern hold consistent, 1/3 ring = 1/3 square angle?
Though if this is a through ring reflector and the steepest angle is on the inside, than it should totaly work. inside45.
If, before you cut rings from the big circle, you draw a wedge from the center of the circle to the outside you will have a measure which represents the amount of mirror to overlap. This could significantly reduce the amount of time spent focusing each ring.
That is a neat idea but I am not convinced that it will form the optimal shape. It might be and well worth calculating or testing if you plan to make a run of these mirrors. The outer segment has to be steeper so it will probably need a larger amount of overlap compared to the inner most ring that remains almost flat. I don't think your idea is optimal. Pre-marking the amount of overlap once you have calculated or measured it once is still a good idea.
This is great! And all the collaborative comments got me thinking... Wouldn't it be simple as pi to drill a hole in the center of your mirored acrylic, mount a dremmel with a cutting wheel on an adjustable arm (like a record baby!), and simply rotate out your rings? 2hrs?! More like 20 minutes! :-)
The dowel idea for focusing is brilliant! And using a CNC machine would make this child's play.
What about taking a cheap piece of plexiglas and carving rings. Could we make a poor-man's fre
I had forgotten all about fresnel mirrors, thinking only about fresnel lenses.
I have access to a laser cutter. I can't cut an angle on the edge, but the laser would cut pretty cleanly.
Another great trick Dan. Thanks
@christo930 I find that reinforced tape (the tape with the string in it, not duct tape, but clear packing tape) is much stronger and doesn't get gummy the way electrical tape does when it gets hot. Since you would want to put this in the sun, it is going to get hot, especially with it being black, at least try and use white electrical tape so it doesn't absorb so much heat.
Very interesting! Thank you
very interesting, in my prototype I used 335 plans mirrors, but for version two, I draw inspiration :-)
I think a rotozip would work really well !
I was pouring some molten lead. Had a small sputter (steam?) and caught a droplet of lead with the lens of my prescription glasses (which I only wear sometimes). I was looking at a 1/2 inch "bullet hole" on the lens (no, it just looked like one, it didn't mark the glass lens at all). From that day, I wear goggles (often a face mask instead). Same for ALL shop work, no matter what it is. WEAR GOGGLES.
Perhaps an easy way to get your focal point right is to put a dowel rod on a block with a bright light overhead as you mentioned. The focal point should shine evenly on the dowel rod and make it easy to calibrate each ring to the same focal point.
Right on! Thanks for sharing!
Just a demo as people have asked about Fresnel Mirrors. Concave shaped mirrors are a much better option.
so did it work?
1:33 that noise gives me goosebumps
Very good Trick, thanks for the idea. Could you show the table saw and the cut?
Would there be any issues if there was a series of holes on one side of the cut, and one hold on the other (might need 2) and a pin?
Good job Dan! I can see the benefits to using such a mirror. ;)
Homestead!
@5lkk I think the point is to make a large area mirror with a short focal length.
A plastic spacer and a pin or screw to hold inner to outer ring as it spirals outward.
changing thickness spacer introduces proper curvature
Great idea. I wonder if the lens of this diameter give you higher output or lower?
THANK YOU DAN NICE JOB **
The most important thing is a ultra smoothenss of the surface to maximize eficiency. Do you know that the mirror in the Hubble telescope is so smooth and even that if it is as wide as the Gulf of Mexico, the waves wont be more than one foot high . Wow! With this kind of mirror ring you got here it bounces a lot of photons off the intended target unseen to your own eyes.. about 10-20% of the photnos will be bounced off the intended target! This is why it is so important to be ultra precise
With a solar heat concentrator there is no need to focus on a pin point. With this setup it is not possible to make the spot smaller than the width of a ring in any event and the flatness of the material is much better the error due to the imperfect curve that will be close to a cone and not a parabola.
Does a old school project have a freznel lens
Really cool, btw was this shot with your EX-F1?
So clever, and a fraction of the price of casting a glass lens and then silvering it!
@darkvader47 Thank you very much for the great comment:-)
How the heck did you cut that with a table saw?
Using a light overhead to determine the correct curve will only focus light from that distance. Light from father away will focus at a different point. But if your target is not exactly a point but an object, it might not make a that much of a difference.
He!!! I want know what,s this material you use (like glass but it is flexible)????
You give me an idea !
acrylic mirror is expensive...
i think it is possible to realize a cheap mirror by gluing a Mylar survival blanket on cardboard...
eh you could try, but good luck getting it to lie down with no wrinkles
if you have a continuum of spacer thickness and you use them in order as they all get pushed inward it forces more curvature, as they get moved out less curvature.
With a Fresnel reflector the inner ring is nearly flat and the outer ring has the steepest angle.
@drorbenami A very quick and simplified answer would be to look up the amount of energy that one can receive in a given area of direct sunlight. You're focusing this amount of light to a point or smaller area. Just because it's focused doesn't mean you're getting more energy. Keep that in mind.This information can be combined with the specific heat capacity of seawater and the latent heat of vaporization. Google or wiki some of that stuff and you'll be on your way! It's simpler than it may look.
wow, that was brilliant !!
it is just , well, a solar art... If you like circles , sure thing.. tiles? why not? They are still all the same.. We can etch micromirrors down to a nanometer in diameter to boost temp well above the nuclear reactor if we want to..
Can you, please leave a shortcut to where i can buy the materials or to at the least has a distribution and name of such materials. I would greatly and respectfully, be waiting on the answer
Could you not wick some cyano glue on the overlapped sections to hold them together?
I've done this for a science project when I was a kid. I tried the tape, but it never worked for me, In the end I drilled holes and used 2 or 3 rivets to hold the pieces together. I presented it as a "Flat Lens". I didn't even know what the heck a fresnel thing was. BTW, circular saw sucks for this, try a scroll saw. Just be careful, a kid in the shop class sawed off a finger with it. Scary stuff...
do you think you could make a video using the fernel mirrors to convert sea water to distilled water? i would like to see: how much distilled water you can get from 1 liter of sea water? and: how long it would take? thanks....
Try making a cut at an angle,
that way, you get the measure of the outer circumference are shortened,
relative to the inner circumference.
that looked amasing but could you clarified how you made the mirror
Thanks a lot !
@danz409 This is GreenpowerSCIENCE with emphasis on science and experimentation. Everyone always gets down on Dan for not taking projects to completion. These are springboards for your mind.
woooo!! love the molley richardson 2k reflector over there! we, these nonsense camera crew & gaffer wacky dudes...
Use a band-saw, rather than a table saw, for easier circular cuts, especially smaller radii. :)
I wonder how else this parabolic mirror can save conserve energy?
good stuff
Where is the link for the circle cut ?
Where are some good places to buy acrylic mirrors?
what about to find the angle as a function of the radii of the mirror ring and the length of the overlapping area instead of the trial/error to find the focal point?
try to do that with a small laser beam to find the good focus point and the settings, it works fine
How about publishing the mathematical formula for determining focal length for a concentric ring IN your video or IN the description? People should know!
and results????
Put two screws in each overlapped ring
Link? I would LOVE to see this table saw attachment
cool
@Frosttty okay, thanks
Yeeahh new video !!! : P
@5lkk How would you build a parabolic mirror easily?
ahhh... ok... thanks!
cut a section of the circle out and discard it! Use the regular parabola formula to calculate how many degrees of the circle to cut out the further out from the center you go! If your rings are only one inch wide then your ideal object size would be one inch! have fun and be safe!
@cohetesdeagua3g Check the video response. I have a blue shirt on:-)
C'mon Dan, a Laser CNC would cut those circles in no time.
a table saw? for acrylic? it's like taking a minigun to hunt rabbits!!
@23027851b you are right I forgot my geomtery lessons long ago..
awesome talking hand LOL
FRENEL mirror?
From Wikipedia: "Augustin-Jean Fresnel (/freɪˈnɛl/, fray-NEL; French: [ɔ.ɡy.stɛ̃ ʒɑ̃ fʁɛ.nɛl]; 10 May 1788 - 14 July 1827) was a French civil engineer and physicist ..."
Thuffering Thucketath thath amathing
too complex. i would just use a parabolic instead
@JohnKapsis1985 Dan hunts rabbits with missiles.
second comment
cool
Because it's more fun or because you don't know the calculations!
The calculations are easy. But whenever you design something on paper you end up having to fine-tune the thing anyways once you start working with limited tools and materials. In this case, it pays off to simply not even calculate circle lenghts and angles because you can find out the correct length of the ring simply by shifting the focal point around and measuring where that lays. It is not going to be incredibly small anyways.
nice voice lol
Yeah but using mathematics is more accurate and I'm aiming for accuracy *NOT* fun.
wow this is boring this will put me to sleep lol