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"Designer" for solar reflectors - Page 6

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Posted by brian white on December 2, 2009, 2:24 am
 
Anyway, for those of you that are interested in designing solar cookers,
  I put 2 videos on youtube to further explain what I am trying to do
here.  The second one shows the basic shape of the reflectors.  Just a
mock up because I have not yet figured how to hold everything in place
as I "design" the reflector.  I think the real reflectors will be more
"scallop" shaped going to tubular towards the middle.
The videos are

and

It helps to watch the first one but perhaps all you need is in the first
5 minutes of video no 2
Brian

brian white wrote:


Posted by brian white on December 2, 2009, 2:26 am
 
Anyway, for those of you that are interested in designing solar cookers,
  I put 2 videos on youtube to further explain what I am trying to do
here.  The second one shows the basic shape of the reflectors.  Just a
mock up because I have not yet figured how to hold everything in place
as I "design" the reflector.  I think the real reflectors will be more
"scallop" shaped going to tubular towards the middle.
The videos are

and

It helps to watch the first one but perhaps all you need is in the first
5 minutes of video no 2
Brian

brian white wrote:
 > The idea here is that if you line up a reflector with the path of the
 > sun across the sky, the best shape for getting maximum concentration of
 > light over one hour, 2 hours, 3, etc is NOT going to be parabolic.  In
 > fact, nobody knows what shape it will be.

Posted by brian white on February 15, 2010, 4:05 am
 Most people will not be interested because this is solar cooking related.
Anyway, I have been continuing slowly with the project.
I had some success making the shape with little square mirrors.
There are 3 links for anyone wanting to follow it.
http://solarcooking.wikia.com/wiki/Solar_design_T-Square
with basic explanation and older pics (and changable by anybody)
Please check out the animated gif for a procedure.
http://solardesign.ning.com/photo/albums/solar-design-tsquare  (more up
to date but less text to explain what is going on)
and
(video of the little models).  You can probably see the shapes best in
the video. (It was hard to see depth when I photographed the mirrors).
Anyway, it does seem to work.
If anyone tries it, be aware that with the cheap little laser pointers
the laser is not in line with the barrel!  If you make a hole for it  in
a piece of wood or metal like I did, you just have to twist it round in
the hole until it is pointing straight down before making any other
adjustments. It might be worthwhile using small laser levels instead to
avoid this hassle.









brian white wrote:


Posted by dow on February 19, 2010, 2:57 am
 
I like the idea of using a lot of small plane mirrors instead of a
large mirror with some complicated, curved shape. I think you should
plan to make this a permanent feature of your device, rather than just
a development tool. In "third world" situations, plane glass mirrors
are fairly easily obtainable. Materials for making curved reflectors
that will be easy to keep clean and will not corrode are not usually
obtainable.

I am worried that you are looking at just two directions of incoming
light, simulating the directions of sunlight at the beginning and end
of a two-hour period, and are (I think) assuming that if the reflector
works for these two directions it will also work for all directions in
between. I suggest you should check if it does work adequately well
for intermediate directions. If it doesn't, you may have to make some
modifications.

Good luck....

              dow

Posted by brian white on March 19, 2010, 1:56 am
 Thanks David.  Your plane mirror suggestion might be correct. It is very
hard to make mylar or alu foil to a curve but relatively easy to put it
on flat material. Same as plane mirrors.
I made a full size clam shaped reflector (Just by scaling up a little
model) for a good sunny day back in Februry. It did work, about 3 hours,
and just one move of the reflector to bake some potatoes in a 7 liter
pot.  If I had ribs on the back of the reflector to make it keep its
shape properly, it would have worked a lot better. (I still have not
done the rib thing).  I checked that it would also work for the
intermediate directions when I made the model
I did make one model where the curves of the primary reflector and the
secondary reflector met too soon and it didn't reflect all the
intermediate directions to the target.
The good thing about clay is that you can easily readjust the model!
I have some videos of the cooking, etc up on youtube. I was lucky to get
some sun in February, usually here it is dull till late March.
Brian
dow wrote:

it.http://solarcooking.wikia.com/wiki/Solar_design_T-Square

procedure.http://solardesign.ning.com/photo/albums/solar-design-tsquare (more up


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