# Parabola



## Chasper (Apr 28, 2009)

Its seriously fun to have kids who come home from school with algebra assignments to make things like this.  On a clear day it will ignite a newspaper in 4 seconds and boil a cup of water dry in 4 minutes.


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## ldb2000 (Apr 28, 2009)

Gerry , If you couple that dish with a sterling engine you could run a generator and power your house .


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## thewishman (Apr 28, 2009)

Gee Teacher, my homework ate my homework.


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## ngeb528 (Apr 28, 2009)

Yeah, but does it get HBO?


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## ahoiberg (Apr 29, 2009)

holy crap, that is cool. i bet your kid got the "did you dad help you with this?" treatment.


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## GouletPens (Apr 29, 2009)

Boy, just think of the ants you can fry with that thing....


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## markgum (Apr 29, 2009)

thewishman said:


> Gee Teacher, my homework ate my homework.


 

naw,,, more like burned my homework..


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## mickr (Apr 29, 2009)

which end has the nib????


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## rwyoung (Apr 29, 2009)

Never made the parabola type but I did make one heck of an ant-burner using a frensel lens once.  Rollie-pollies (sow bugs) are kinda like popcorn.


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## PenTurnerfromMaine (Apr 29, 2009)

I never had that much fun with homework


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## Mudder (Apr 29, 2009)

Yea, but can it pop popcorn?


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## IPD_Mrs (Apr 29, 2009)

Can you put Cav's avitar in it?


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## LizardSpit (Apr 29, 2009)

Will you share the plans?


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## randyrls (Apr 29, 2009)

Are Jamie and Adam hiding around the corner????

Looks like something they would cook up!   







Who Ya Gonna Call.....   Mythbusters!!!


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## CSue (Apr 29, 2009)

My algebra homework never looked like that!


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## Chasper (Apr 30, 2009)

LizardSpit said:


> Will you share the plans?



Here you go: Ax² + By² + Cx + Dy + E = 0  (if you really need to know what that means I'll have to ask my kids)  Once you determine the y you want to use you graft it life size.

We started by turning a very shallow but thick bowl (8" diameter X 4" thick with less than 1/2' bowl indention) and cutting 16 notches in it around the edges; it looks like a big gear.  Then we used the life sized graph cut out to cut 16 ribs out of thin plywood; the ribs are about 30 inches long and they curve up 12 inches, each rib plus the radius of the hub combine to the radius of the parabols, about 33" in this case.  The bowl is covered with thin sheet aluminum and it is covered with mylar. 

The algebra is in the quadratic equation to get the curve right so the heat reflection all goes to one spot in the center directly at the bottom of the cooking vessel.  http://www.mathwarehouse.com/quadratic/parabola/interactive-parabola.php go here for more info.


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## TribalRR (Apr 30, 2009)

Nice!!! A miniature Archimedes death ray!

How far out is the focal point?


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## jleiwig (Apr 30, 2009)

look up tracking solar concentrator on google.  There are plans out there.  Makes one hell of a water heater!  It was a green solution developed back when being green wasn't cool like it is today.


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## artistwood (Apr 30, 2009)

ok.......so is a jet, toolcraft, grizzley or what...........seriously, very cool........er......i mean hot!


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## btboone (Apr 30, 2009)

I had made one about 6 feet across when I was in school.  I cut a couple thousand mirror sections and glued them to a steel sheetmetal frame.  It worked well and would melt lead.


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## LizardSpit (Apr 30, 2009)

Thanks!!!  Now who will translate?  My kids have all graduated and left the house (mixed blessing  )


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