How to build a heliostat parabolic reflector

Turn a flat sheet of anything flexible into a parabolic reflector.
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Step 1: Prove it to yourself

Download this template and print it on cardstock, add something shiny cut it out and tape the edges together, don't cut all the way to the center. The template is Deltacad 6 format

Step 2: Now what?

Wel, you're done, you can print that template out any size and go to town, the plywood dish at the beginning was made that way. However if you like, in the next step i'll give you the math.

Step 3: So here's the math

Sort of, for the educated its based on the difference between the arclength integral and x, you can take it from there, for those not fond of thinking read the attached file.

Step 4: Now to build one

You could just cut one out with a jigsaw like the one at the beginning, but for better accuracy I printed out a section and made a router template

Step 5: Next I acquired the materials

I want to say I acquired all these signs LEGALLY, with permission, from the dumpster of a polling place, and I'd really like to see more instructables based on this resource, i know i'm sickened that signs are printed on a material designed to last a million years and are up an average of 2 days.

Nothing like dumpster diving in the rain

Once again these were collected legally.

Step 6: Now cut them out

quick work with a router, lots of plastic curls eveywhere, once they're cut out apply shiney aluminum tape from the hardware store.

Step 7: Now find a cool spot to work

And tape the peices together, or use cable ties, it came out a little peaked so I added a ridgid disk in the center to flatten the curve, I should have done that first.

Step 8: Finally flip it over and tada a parabolic reflector, now to turn it into a solar oven

eventually I hope to turn it into a tracking solar oven with drill head motors. a word on the coroplast plastic in these signs, to glue it u can flash it with a blow torch and use super glue, and hot glue works well to glue it together, the "rigid disk is just two pieces with the corrugations orthogonal glued with hot glue. Sorry no pix in operation, it's dark out.
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lansry1 year ago
Get a large smooth beach ball the larger the better because the outer edges of the dish we'll make have to be cut away since they'r perpendicular to (i.e. not reflective the incoming signal. Use polyester laminating resin (fiberglass resin) and 1 or 2 layers of fiberglass cloth to cover half of it (keep it this for light weight). The focal point of the deep dishes is closer to the center than the shallow satellite dishes. This makes it less cumbersome and not as top heavy. Get some tacky adhesive (try 3M or similar) and roll strips of aluminum foil inside with a small smooth ball or 4 inch paint roller covered with a plastic bag. Focal point will be:,or.r_qf.&bvm=bv.48340889,d.cGE&fp=baea18be682a6c13&biw=1024&bih=679 Use the metal rod out of a lamp or other. Make a pivot out of cardboad and polyester laminating resin. Take the rod that bolts to dish and put in the center of a square of cardboard. Place pieces of cardboard to either side of it. The cardboard pieces must not be higher than it's diameter. Remove the rod and fiberglass the pieces keeping them in same position as when rod was present. Do the same for the vertical rod which will be the floor mount. Get a piece of auto inner tube or similar rubber to go between the fiberglassed cardboard. Put the two pieces together (one hole will be vertical the other horizontal). Drill a hole put a bolt with a flat washer through it, another flat washer on opposite side, then a lock nut and a wing nut to tighten it. Cut a large circular piece of plywood for the base. Glue a piece of 2" x 4" wood (or similar) to it in the center. Drill a hole in it's center the same diameter as the vertical rod which will support dish. Place weights (perhaps liquid soap bottles filled with water until you find more aesthetic) on it to prevent tipping. Use an Alfa AWUS035H wifi adapter mounted with cardboard pieces in the shape of an "L" bracket. Punch holes in the cardboard and put 2 rubber bands through to hold the adapter in place (this makes it adjustable). Tape the cardboard mount to the dish and then glue cardboard tabs to the backside to prevent it's moving. Sorry folks this is as simply as I can put it without photos. Ask your friends if they understand. Hav fun . . . digit while U can. Kiss kiss ttfn, bye now
br0dy1 year ago
An easy way to get the diagram needed to build a paraboloid from a flat sheet with different distances from the vertex to the focus
"...for the educated its based on the difference between the arclength integral and x, you can take it from there, for those not fond of thinking read the attached file."

Would it be a violation of the "be nice" Policy to tell you to flippin' piss off!!? 

Arrogant little twit. Why do people that are good at advanced math seem to think they are better than others? I learned to read at age 4 but I happen to hate math. I passed high school Algebra with a D and never looked back.  And I have done ok so far. If I wanted to be a rocket scientist I would have study rocket science. Really this is no more than the math it would take to figure out the arc of a boat deck. I've also built a 17 sided end table and covered it with 6 inch wide 1/4 inch thick mirrors without a calculator and it came out perfect. I also know a little about GPS, Grammar, Punctuation and Spelling. (subtle hint)

Does that make me "not fond of thinking"? As if I care about your opinion. I was just looking at your channel and had almost decided to follow when I read that comment. Now you can you can take a long walk off a short pier for all I care.
tstark19702 years ago
For pete sake people someone talk english here... we are not all science buffs.. just put the math on here so we know what the heck to do. It would some much easier then giving us this sight and that sight.. just tell us what the piece measures that way we all can make on and go about life. I can't open it either and I have the program for it.. SO TELL US PLEASE :o(

I convert the file to PDF format with Any DWG to PDF Converter -

drmattyg2 years ago
I wasn't able to reproduce your math. Here's what I worked out, I'd be interested in your derivation:

Ah, I see now that you were approximating for shallow parabolas. Given the ability to use, e.g., to do complex integrals, and the fact that it has a closed form, I don't see any reason to use the approximation, but it all comes out the same in the end.
Modarius6 years ago
How come I can't open this file? I have an IMac and the parab16 wont open. also the "dxf" file shows up as a bunch of letters and numbers and lines. Please help a newbie out as I'm not good with this stuff. maybe a PDF file or something like that
Hello,I always use the dxf viewer to view dxf files. You can google it, or you can visit to download a free trial version to try.
Use Inkscape.
hi well i use Windows XP but i convert the DXF file to EPS and CorelDraw just click on donwload RAR file on this link
Here is a free online media format translator that should help:
you need adobe illustrator
vallesan3 years ago
Hi TOOL USING ANIMAL I took you design and convert it to a Corel Draw 14 and EPS anybody can download it from here : if you don't agree let me know i will erase the file .. thx in advance ........................ Aqui esta el archivo convertido a CorelDraw14 y a Vectores en formato EPS .. por favor hay que distribuir cocinas solares para que c deje de contaminar y talar arboles :
Ardnoc4 years ago
in your example calculation I think you have the petal count and focus transposed. 

nice instructable!  using this for the mirror on a solar cooker.

spinach_dip7 years ago
People call that stuff "street spam" and when it's not election season, it's no more illegal to harvest the neat corrugated plastic than it is to pick up litter on the side of the road (which it exactly what it is).

Yea, of course there's an exception for elected officials and those who seek public service to pollute, but you can go shopping with a clear conscious. after the election law deadline.

I've used this stuff to hold the insulation away from the under eves vents in my attic.

Here's another use:

Thanks for the link. I love the lounger. I don't have room for it but can use it for insiration. I think this would be a great instructables challenge to start the day after the election.
A freeware program for those that haven't found a way to view and print .dxf files:

Irfanview has a Paint plug in so it's very easy to cut, paste and print sections of that paraboloid.
cactii4 years ago
 In the rain hey... That explains why all the signs are blurry. ;)
strmrnnr5 years ago
Just wondering if you have ever used this with a photovoltaic cell. What kind of an effect do you think it may have on the output of the cell? Do they have a Max. designed for standard direct sunlight? Might be able to turn a cloudy day into a sunny day, for the cell anyway. Just wondering.
I saw a video on youtube where a fresnel lens was focused on a pv cell and the cell was under water to stop it from bursting into flames.
I've never tried, but readed about photovoltaic cells. Apparently (and obviously) you'll get more energy out of it (compared to no reflector) but it will shorten the life of the cell. I haven't tried but it sounded logic to me. Instead, I plan to use a stirling engine (coupled to a dynamo), which looks to me more efficient.
matroska5 years ago
"Nothing like dumpster diving in the rain." That's a new favorite quote for me!
radon2225 years ago
If I print out this template at some other size, how would I figure out how far out the focus is? I want to make a reflector for a wifi transceiver and I need to know where to place the transciever. When I printed it out on 8.5x11" paper as large as possible using a crapy dxf viewer, I was able to get it to print it on 2 pages at 8.75" in diameter so there must be a way to calculate the focus distance from that...
strmrnnr5 years ago
Go to Wal-mart and get a couple of those full length plexi glass mirrors for $10 and cut it into 1" strips to line the inside. You'll get some reflection then.
bazalaz5 years ago
save the dxf file to your desktop then convert it to pdf using anydwg
bazalaz5 years ago
google dxf to pdf converter or go to they have a free trial that will convert to pdf for acrobat reader
fishhead4555 years ago
FLATULATIONS--Not sure if you guys already know this but here

is how I figure the curve for my trough collectors. Carefully constructed these will turn water to steam in a pipe I use engine oil. Build a small trough and heat water quickly.
Thanks to Homohabilis for starting this thread.
I would be SERIOUSLY interested in details of how you made trough-shaped collectors. I've thought about building a heliostat (that is, a steam engine powered by solar heat) for years!
wanzewurld6 years ago
I've been thinking along these lines for a couple of weeks recently and for a few years off and on. I was wondering what I could do with an old(er) ~8 Ft. satellite dish receiver. All I could come up with as a coating was aluminum foil which would cut the efficiency down and re-mounting it on a squared "Y" mount. Then it would be a matter of clock driving the vertical main mast and rotating the dish from one side. That would give control over azimuth and altitude. I was thinking along the lines of using a cone as a pulley or belted drive which would give varying tracking to adjust for the hours of daylight and approximately the same thing to adjust for daily altitude changes on relative sun position. It seems unwieldy but should work in theory. Any feedback on this? Adding to the "heating water" and running a sterling engine I read years ago about a long parabolic reflector heating a long tube but the heat transfer liquid they used was Tung oil. I'm trying to research that but Tung trees seem to have fallen out of favor since my childhood; they grow well in this section of the country though and make beautiful shade trees. They make a sort of "Fruit" that was once the basis of almost all oil-based paints. A "nut" was a bit smaller than a tennis ball and left a bruise if you were unfortunate to be standing at the right place at the wrong time! I'll furnish an E-Mail address in the near future for anyone caring to correspond and collaborate. Wayne
paladin426 years ago
would like to apply this to my batch collector to help focus the sunlight. what angle is most effective for heating my water tank. also can i use this to possibly lengthen the amount of time in the day in which the sun will hit my collector. my thought is as the sun goes down the reflector will focus and intensify the waning sunlight. any help is greatly appreciated.
The angle is always--your latitude plus 15 degrees. (Example: if you live at 30 degrees latitude the angle will be 45 degrees).This in the correct alignment to take advantage of the planet wobble between the relative positions of the sun in summer and winter.
Sandisk1duo5 years ago
hey, that's not tape, you just blurred it out in photoshop! Great instructable though!
Tool Using Animal (author)  Sandisk1duo5 years ago
No that's tape, the blurring was because I worked for the county at the time and didn't want to get in trouble for using the political signs.
oh ok
Thank you!! I've been looking for a way to do this (easily) for three seasons now! And without figuring out the math! I'm just not built that way. There's this amazing spanish video on youtube that shows that you can cook anything in the cooker (fried, baked, boiled, canned, and even popcorn)! Enjoy:
Hopefully I'll post my replica before September :)
wanzewurld6 years ago
I see that I seem to have an E-Mail address at this site so someone please send me something - anything so I can see if it works. I don't see any way of sending anyone else E-Mail but haven't explored my "Inbox" yet. Perhaps they have an address book there. Wayne
nuke-em6 years ago
Totally agree with macrumpton. The picture could be written in an easier format.
for mine, instead of using signs i used reflective duct tape, i don't know what it is called and i put it on my dish, one problem though is that i accidantly put more tape over a lot of spots and so now the focus point is really hard to find oh well, GREAT INSTRUCTABLE!!!!!!! thanks
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