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Sqaure Parabolic Dish Calculations? - Page 2

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Posted by Jim richards on June 27, 2008, 6:03 pm
On Fri, 27 Jun 2008 07:04:31 -0500, "Duane C. Johnson"


I will be using software to position the dish (4.3 Tracking
conclusions "C Christopher Newton") but I was wondering if the
circuitry on one of your trackers could be modified to feedback the
relative cloud cover (brightness) to the software for performance
monitoring purposes?


Posted by Jim richards on July 2, 2008, 8:38 am
On Fri, 27 Jun 2008 14:03:01 -0400, Jim richards

Thanks to all who helped with this thread, after a lot of head
scratching I finally got the CAD program to play nice. There are no
short cuts or the horizontal and vertical frame members won't align
properly. But when the calculations are correct, the CAD is visual

See attachment. (if this group allows attachments?)

Now that the parabolic calculations are confirmed it's time to
concentrate on the over-all design.


Posted by Duane C. Johnson on June 27, 2008, 3:52 am
 Hi Jim;

 > Is there a difference between the calculations for
 > round and square shaped parabolic dishes?

The basic and exact answer is no.

We usually think that a round dish is a paraboloid caused
by rotating a parabola around the central radix.
Technically the square dish is the same thing.

Now the cool part:
If you take that same parabola and test it at all other
locations it "Exactly" matches the paraboloid there also.
Of course this requires that the radix of the test
parabola is parallel to the paraboloid radix.

Here is an example of a square dish:

The ribs used in this dish are exactly the same
curve except they are moved in translation
instead of rotation.

Another example:
This is Doug Wood's design.
This picture shows the ribs, which all have exactly
the same shape, and assembled in 2 directions.
Here is his patent:
And a couple of pictures lifted from the patent:

 > I have calculations for round shaped dishes and all
 > models from these calculations work fine, but using
 > the same calculations for a square shaped dish and
 > no go. Does someone know what I'm missing?

Is it possible that you are not aligning the radix's
of the all the parabolas parallel?

 > TIA

 > Jim

Hope this helps!


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Posted by Jim richards on June 27, 2008, 6:55 am
 On Thu, 26 Jun 2008 22:52:38 -0500, "Duane C. Johnson"

Thanks for your reply Duane too,

I've run into your site many times although I don't know how I missed
the MIT link Thanks.


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