[TheForge] How to melt steel with sunlight:

[peter fels & phoebe palmer]

On 11/26/2010 4:02 PM, Bruce Freeman wrote:
> Small (like 11") plastic Fresnel lenses are cheaply available
> (http://www.scientificsonline.com/large-surplus-fresnel-lens.html $7
> ea) -- 121 sq inches each.
> 1.5 sq. meters is about 2325 square inches -- about 19 of those
> Fresnel lenses.  So, if you made an array of 19 lenses, with their
> foci all at the same focus, then you'd have the equivalent lens.
> However, since you'll be using other mirrors to direct the light to
> the lens, then you can probably do with fewer Fresnel lenses if you
> focus the mirrors on one or more of the Fresnel lenses.  Maybe as few
> as five Fresnel lenses would do the trick.
> With no liquid involved, the whole assembly of mirrors and Fresnel
> lenses could be mounted on a swivel to follow the sun.
>
> I have another idea, but it's pushing the boundaries a bit.  View this
> page:  http://gr5.org/index_of_refraction/
> Now, imagine layers of glass or clear plastic, each a circle slightly
> smaller then the next lower one, overall, forming the shape of a lens.
>   Between and around these, use a liquid of the same index of
> refraction as the glass.  The boundaries between the layers will
> disappear.  Now IF the viscosity of the liquid is correct, then the
> liquid will bead at the edges of the layers and form a continuous
> surface to the lens.  (That's pushing it, I know.)  Voila', an
> assembled lens.  Drape a sheet of thin transparent plastic over the
> top to preserve the liquid.
It'd be more practical to grind a calculated bevel on the glass edges if 
it's to endure.
> Of course, yet another means is to skip the lens entirely and use tiny
> mirrors, each with a controller to point them in a direction such that
> the focus the sun on the same point.  The trick is to get the
> controllers cheap enough!
>
> On Fri, Nov 26, 2010 at 6:23 PM, peter fels&  phoebe palmer
> <artgawk at thegrid.net>  wrote:
>> Thanks Bruce;
>> That's delightful!
>> Brings me back to my old proposed solar forge
>> If one were to use an array of cheap mirrors with tracker/step motor
>> rigs like Kurt's,
>> combined with a big lens...say a pool of water in a plastic sheet hung
>> from a frame.....
>>   or a big sheet of slumped glass in a frame filled with water or oil....
>> Would that get up to forging temps?
>> It looked like they were ready to weld there.
>>
>> On 11/26/2010 2:42 PM, Bruce Freeman wrote:
>>> How to melt steel with sunlight:
>>>
>>> http://blog.makezine.com/archive/2010/11/2_square_meters_of_sunlight_focused.html
>>>
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