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/diy/ - Do It Yourself

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138480 No.138480 [Reply] [Original]

Building a solar death ray. Something like this.

http://www.youtube.com/watch?v=TtzRAjW6KO0

I am trying it for the first time, any tips from the experienced?

>> No.138484

>>138480
Don't point it in your eyes to see how bright it is.

>> No.138486

that's pretty neat. I wonder what the effective range is, seemed to be rather close.

>> No.138499

>>138486

>Didn't watch the video

>> No.138501

>>138499
yes I did, the range was extremely close stop wasting time

>> No.138509

>>138480
Is not possible, the Mythbustesr already disproved that myth.

>> No.138512

>>138509
fuck those hacks, gtfo the proof is right before your eyes

>> No.138536

>>138484
Thanks, I'm sure this tip will come in handy.

>> No.138575

http://en.wikipedia.org/wiki/Fresnel_lens

you don't really need to make a dish out of tiny mirrors.

A Fresnel lens usually takes a single point of light and projects it straight out. But it can be used in reverse with a light source being focused on a particular point. You can buy them for a couple hundred dollars, but you would still need to build an armature to align your lens with the sun.

>> No.138685

Check out Rob Cockerhams work http://www.cockeyed.com/incredible/solardish/dish01.shtml

>> No.138708

get a Fresnel lens from an old projection TV. people give them away all the time. Mount said lens on a rotating frame and watch as things burst into flame.

I built one a couple years back at a friends' house... 2x4s and such would leap into flame with no effort whatsoever. WEAR WELDING GOGGLES if you value your eyesight.

>> No.138782

>>138708
>>138575

this

https://www.youtube.com/watch?v=aBgTmEKRP44

>> No.138786

>>138575
Looks like you know about that stuff. Are Fresnel lens more effective?

>> No.138789

>>138480
I made one some time ago. you can make one from the Fresnel lens from a discarded Read Projection TV. Those lenses can be 4' wide! I've done the mirror chip method; flat surface with mirrors aligned to make a focal point. Google, "Fresnel lens melting pennies" or something similar. There are youtube video of that.

The best thing I can recommend is making sure that whatever parabola/reflector method you use that you make the focal point further down and out of the sun's rays, from the sun to the reflector(s), this way you can play with the focal point without putting a shadow over the reflector(s). There's a guy who took a large 1980s satellite dish and covered it all in aluminum foil to make an SDR. It was pretty cool and there should still be links for it somewhere online.

Remember, that focal point can be excessively hot and ignite things on fire instantly. Even a bird flying through it can die if you have a big enough reflector array. There was some art thing in a European (I think European) country that happened to include a parabola and it was killing flying birds at certain times of the day when the sun was bright on it. Don't even pass your hand through the focal point because it can instantly burn you.

If you do get burned, use yellow mustard on the burn ASAP. Leave it on for 15 minutes. This will cool the burn and more importantly will help prevent tissue damage and pain (I've been using it for years).

A SDR is a great way to heat a Stirling Engine, fyi.

Now I basically make solar box ovens. I've been wanting to tray an SDR with a fiber optic array at the focal point to see if you can make a wood burner out of the fiber optic cable. It's probably a pipe dream though.

>>138509
lol Those guys are idiots when it comes to science.

>> No.138791

>>138786
It's far easier to use. Making any other kind requires more work, but is fun to do. If you make another kind I recommend doing it with a single light in a room. This way you can use that single light's reflected rays to angle the focal point of each mirror without blinding yourself of causing fires.

>>138708
> WEAR WELDING GOGGLES if you value your eyesight.

A 1000 times this. Even my small 15"x15" Fresnel lens is enough to cause temporary blindness if you look at the objects you are burning with it.

Also, if you want to burn things faster, paint them black where the sun hits them . Things of light color reflect too much sun off in order to heat of quickly..

>> No.138867

>>138509
They weren't testing this setup in general, only the idea that the technology to make it was available to some ancient philosopher inventor in ancient Rome or Greece.

>> No.138894

>>138867
Archimedes was Greek (287BC to 212BC). At that time he would probably had metal polished mirrors instead of the glass-metal backed mirrors we are accustomed to now. On Mythbusters they did succeed in charring and small flames. Each "test" I've seen people doing this, used incorrect mirrors.

The mirrors used by Archimedes were most likely slightly parabolic metal-polished mirrors. the amount of parabola those type of mirrors would need would be extremely slight, just enough to counter the edge glow of the focal point. This means each mirror's reflected light would have a tighter focal point than the ones used by Mythbusters, that group of school children, or anyone else. Not only that, but polished metal mirrors have less light loss than glass-backed mirrors because the light does not pass through glass twice where it can be lessened in power by as much as 10%. Because of these things, the focal point of all the mirrors will be smaller and far hotter. The ships back then had pitch and tar on them. This is ideal for an SDR to ignite the ships almost instantly, because of its dark color and ignition properties, if the mirrors were large enough of course. It would be like a laser passing right over the ships as they sailed through the focal point and anyone on board caught in the focal point would most likely die of 4th degree burns.

The technology to do this was available at that time, though I highly doubt they simply used shields and instead use purpose-built mirrors because you'd need very large mirrors in order to help reduce the size of the reflection blur at that far distance of focal point.

>> No.138895

>>138894
>Each "test" I've seen people doing this, used incorrect mirrors.

Oh, except for the one in the 1960-1970s that used metal polished mirror to completely destroy a mock up ship in seconds. I don't' recall the correct year.

>> No.138931

>>138894
>>138895
>>138789
>>138791

Thank you very much for the information. I'm the kind of guy who would do anything just to get better effect.

>> No.138956

>>138931
Well, the larger your reflectors (mirrors) the further away you can get from the focal point. As distance extends the spot of light they cast as the reflection get fuzzier. This unfocused area scatters the amount of solar power. You want a focal point as tight as possible.

Keep that in mind for focal point distance and even the shape of the reflectors if you are using the multi-mirror array. Round mirrors will reflect a better focal point than square ones (the sun isn't square for instance) and allow you to better align all the mirrors to a single spot.