[TheForge] How to melt steel with sunlight:

[Bruce Freeman]

A) We don't need no stinkin' cooking pot!
B) That installation can get a cooking pot up to 6300*F = 6790*R =
about 2 or 3 times any temperature a blacksmith or welder would need.

The more I think about it, the more I think that a single 11" square
Fresnel lens would do the trick.  Combine that with Peter's idea of
flexible mirrors, and you can probably assemble an array of 1.5 meters
square (that's about 5' square) at small expense.  I.e, mirrors direct
sunlight onto Fresnel lens; lens directs light to focus.  Simple.

Mount the assembly on a pivot to rotate the assembly to face the sun
without the focus moving at all.  Once the device were set according
to latitude, the tracking could be controlled by either a timer or by
a very simple device that moves the assembly as the image of the sun
through a small hole moves relative to a light sensor.  Make that a
UV-sensor, and the tracking would work on cloudy days, albeit the lens
would not produce nearly as much heat then as on sunny days.

One warning -- wear a welder's helmet, as the focused sunlight
contains quite enough UV to destroy your vision if reflected into your
eyes.



On Sat, Nov 27, 2010 at 10:47 PM, James Binnion <jbin at well.com> wrote:
> You might want to look at this. It will give you an idea what size installation you would be looking at for a hot zone the size of a "cooking pot" http://en.wikipedia.org/wiki/Solar_furnace
>
>
>
> On Nov 27, 2010, at 5:24 PM, peter fels & phoebe palmer wrote:
>
>> Sounds even better.
>> But we are talking about a pretty big fresnel lens then ...though i
>> suppose a bunch of them could be used in a grid, given a bulge to mount
>> them on.
>> Those cheap dimestore mirror strips designed to fit on a wardrobe door,
>> have the interesting property of bending into a mild arc,i
>> found....which could be used as a focusing mechanism.
>> Tempered glass will bend even further.
>>
>>
>> On 11/27/2010 6:01 AM, Andrew Vida wrote:
>>>
>>> peter fels&  phoebe palmer 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.....
>>>      Too much fuss.  Fresnel lenses can be made arbitrarily large yet remain
>>> very light in weight.
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>
> James Binnion
> jbin at well.com
>
>
>
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-- 
Bruce
NJ