Date: Sat, 27 Nov 1999 12:31:50 -0700
From: rwduncan 
To: 
Subject: Solar Furnace

Hello Bill,

My name is Robert Duncan and I live in the Phoenix, Arizona metropolitan
area. While searching for solar energy-related subjects, I found your
website through Infoseek. After reading your 1996 article on the
Infinitely Large Solar Furnace, I became interested in your technique and
constructed my own. The finished product is a 48 inch by 48 inch solar
furnace with 1440 mirrors. While this is hardly infinite, I was able to
transform an aluminum beverage can into smoke. 

The materials and method of construction differed only slightly from the
information posted on your website. I used drywall screws instead of
machine screws because they were cheap. I pre-adjusted all the drywall
screws for a thirty inch focal length prior to gluing the mirrors in
place. I also omitted the toothpick spacers since my final adjusments
would be very small. The programming was done by placing an unfrosted
lightbulb at the focal point, allowing each mirror to reflect the light
onto a grid pattern drawn on a piece of plywood placed along the focal
plane. Each mirror was adjusted until its reflection was aligned with it's
corresponding grid sqaure on the focal plane. 

The result was approximately 1000 watts of solar influx concentrated on an
area the size of a silver dollar. Wood ignited with an audible "pop" the
instant it entered the focal point. Toast burns instantly. Aluminum melts
after 15 seconds. Half inch copper tubing deforms under it's own weight
after 20 seconds. Steel glows red in about the same time. The temptation
for onlookers to stick thier hand in front of the furnace is strong, so I
keep a cardboard box handy to demostrate what will happen to them if they
try. 

I appreciate the information and I wanted to pass along this success
story. All this was accomplished with less than a $100 investment in
materials. My next step is to build a heliostat and attenuator to create
an apparatus similar to the ones at the National Solar Thermal Test
facility in New Mexico. 

Thanks again,
Robert Duncan
rwduncan atsign gateway period net