Making a reflector out of sheet?

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Not a welding question, but one of you guys will know what to do...I watched the winter sun yesterday and lamented that the angles of a couple of buildings mean that it doesn't quite reach into my courtyard/kitchen area.I walked out to where it was hitting a wall, held up a piece of mirror and the sun bounced into the shaded area.The sun is in the northern sky for us in winter. That wall mentioned above faces west. So if you imagine a compass, the light will come from the north point, hit the east point (the wall), and bounce to the south point i.e. where the kitchen is. So now I want to make something big enough to flood the area with light. That means putting some kind of reflector on that wall so the sun coming in from the north will bounce of it.1. I'm presuming it needs to be convex.2. I know there will be lots of experimenting.3. It will have a steel frame and be mounted on the world's sturdiest carpart.What's a good material (cheap and easy to work with) that I can use for the reflector? Something I can bend over a frame and polish - but not to mirror sheen - that won't weather too badly?Scott
Reply:aluminum is the first thing that comes to mind.  maybe 18 to 24 ga.keith
Reply:Okay. So I could make a frame out of square tube and rivet the sheet to it.Would sheet gal works as well?Which would be easier to polish?
Reply:I assume by "sheet gal" you are talking about galvanized sheet metal. yeah your could polish it.. but you would be taking off the galvanized surface and it would rust.  which would render the "reflector" pretty much useless.  the aluminum would polish to what ever sheen you wanted and wouldn't rust though overtime it will oxidize "turn milky" but some car polish would slow that process down a good bit.the aluminum can be bought in diferent grade polishes as wellkeithyou might also do a search on http://www.motherearthnews.com/  they have all types of old articles on solar reflectors, etc.Last edited by metalworks; 07-09-2006 at 09:11 PM.
Reply:spray the entire reflector with a high gloss clearcoat before you mount it on the wall, and polish it when it starts losing its reflection.i imagine this would work nicely, and last much longer than bare metal exposed to the elements. when/if it does start to oxidize polish it again and repaint.
Reply:I hadn't thought of the clear coat.I might make a template out of board and stick aluminium kitchen foil to it just to work out the reflector size and amount of convexness or convexivity or whatever it's called.I wonder whether one of those mirrors they have near blind corners would work? They're the convex ones that enable you to see what's coming before you drive out. I'm sure they polished steel.I can see another unfinished project coming up.
Reply:I can see another unfinished project coming up.yeah me too ...zap!I am not completely insane..Some parts are missing Professional Driver on a closed course....Do not attempt.Just because I'm a  dumbass don't mean that you can be too.So DON'T try any of this **** l do at home.
Reply:Here in the US there are tons of the old 8' to 12' satellite dishes rotting out in backyards or thrown into heaps. Perfect shape, actuator included. You would have to figure out the finish. Plexiglass or cheaper with silver paint. Painted on the backside like they do most mirrors ?????
Reply:That's a great idea.I'd have to use the back of the dish. If I used the front i.e. the concave side, it would concentrate the light into a point, sort of like a magnifying glass. Maybe I'm wrong about that.An old dish would be good. People here use them, too, to pick up some foreign TV stations. though they're not as common. I'll see if I can work out how to find one.What's an actuator?I did mange to advance some of my unfinished projects on the weekend as the weather was so great.Scott
Reply:If it were me I would go with polished stainless steel.  No rust or oxidation.DennisThermal Arc 185-TSWMillermatic Challenger 172VictorO/AAtlas Craftsman 12 by 24 LatheEsab PCM-875Wholesalem Tool Mill-Drill
Reply:What's an actuator?
Reply:Last time I bought some stainless, I was amazed at the cost. Maybe stainless sheet isn't too expensive? Not having to maintain it as much would be good, though.
Reply:You could try out your concept with aluminized Mylar stretched over a PVC pipe frame.  Very lightweight.  Easy to fabricate.  Easy to handle and orient.  Highly reflective in the visible range.  Not sure about cost, but probably cheaper than reflective sheet metals per square foot.Downside?  I don't know about longevity under intense sun exposure.  Don't know if the aluminizing reflects UV, protecting the Mylar.  UV resistant materials may be available.  More exotic (and expensive) materials are available in aluminized form, including Kapton (polyamide) and Teflon.  Don't know about wind resistance or noise generation in wind due to flapping.An actuator is the motorized ballscrew that allows you to rotate/tilt the object controlled from a remote controller location, a capability that could greatly increase the utility of your light reflector as the angle of the sun changes through the day and through the seasons.  Such a sun-tracking reflector is called a Heliostat (meaning stationary sun).Have fun.awright
Reply:I'd at least look at stainless steel (and your budget) because it would be the clear winner in reflectivity v. durability.It does NOT need to be convex, and I seriously doubt you'd want it to be parabolic, like a satellite dish, but do some experimenting.Will there be other times of the year/day when it will be a nuisance to you or someone else?
Reply:A parabolic reflector would focus the light to a single point, which would provide a nice hot spot, but wouldn't be great for providing light.  I'd recommend aluminized mylar as well.  The stuff is cheap and optically very efficient.-Heath
Reply:The focal point of any salvaged parabolic dish would be that of the original antenna length/distance (ruff descrition).  Any distance any further away than that and it's an inverse scattering of the light reflected. An experiment of flat versus concave might prove intersting.
Reply:http://www.int.iol.co.za/index.php?s...3229954082B223I had read about this in one of my wife's magazines.  Here is a town that is doing essentially what you are trying to do in your back yard.http://ezinearticles.com/?How-to-Ach...sign&id=118771This second article makes an interesting points about other elements of lighting in an area (inside, mainly, but can be applied to outside).http://www.ucsusa.org/clean_energy/r...rgy-works.htmlMight be some ideas here.  However, it looks like a parabolic surface may increase heat as well as light...I don't know if that's desirable for you.http://www.lrc.rpi.edu/programs/Futu...ting/index.aspa bit more.I don't know a whole lot about this stuff, but it was fun finding and reading these links...now, I have some ideas for my shop.  Lighting has always been a problem there for me also.Smithboy...if it ain't broke, you ain't tryin'.
Reply:I knew this one would pique your collective interest.Thanks for all the replies.The reflector will be used to bounce the winter sun into the dark recess of my courtyard/kitchen. In summer, the sun won't really hit it, but I'll probably take it down anyway just so it lasts longer.If I could bounce the heat, too, that would be a great and unexpected bonus.Mylar was mentioned by a few of you and in one of the articles to which Smithboy posted a link. I've never heard of it, so I'll have to find out where I can get some.For durability, I'd still like to go stainless or polished aluminium. We'll see.Mylar would enable me to experiment with different shapes till I find what works and then I could fabricate it in something more weather tolerant.It's now on my project list. I'm going to resist starting it till I've finished a couple of things.
Reply:im curious to see how this comes out, this seems like one of those projects that alot of people could benefit from and not realize it.
Reply:One of Smithboy's links was a story about a town that gets no direct sunlight in the winter - a mountain blocks it. They plan to put reflectors on a hillside to bounce light into the town. People, like plants, respond to sunlight - it can have a huge impact on general well being.
Reply:Just did a google search - 'reflecting sunlight'Came up with a question in a physics forum posted by a guy who wants to do exactly what I want to do.They weren't nearly as helpful as you guys about 'the how', though.http://www.physicsforums.com/showthread.php?t=118606
Reply:Originally Posted by scott brunsdonLast time I bought some stainless, I was amazed at the cost. Maybe stainless sheet isn't too expensive? Not having to maintain it as much would be good, though.
Reply:Here are a couple of links for you scott for stainless prices make sure your sitting down when they give you a price http://metals.lincdigital.com.au/sales_enquiry.asphttp://www.aaametalsuppliers.com/Creative metal Creative metal Facebook
Reply:Thanks for those contacts guys. That stainless sheet price isn't too bad. I'll check out the aluminium option, too. Of course, I'd hate a big wind to come up and send it sailing down the street. Pity the wall that I want to bounce the sun off is the side of my neighbour's house. If it wasn't, I would just fix the sheet to the wall instead of having to build a frame.
Reply:Flat vs Concave vs Convex is determined by how much light and heat you want.  If the sun shone directly on the window would it be too much, too little, or just right?  If just right use a flat reflector, too much use convex, too little use concave.  Amount of concave or convex will alter amount of light/heat hitting window.  A large reflector is wasted material if most of the reflected light hits the outside wall instead of the window.If the sheet were formed into a true parabolic form (in one dimension, only, of course), and were pointed directly at the sun, the rays would focus into a line at the focal distance, then diverge.  Unless you were standing at the focal point and got a line burned in you, the effect at a distance beyond the focal point will be about the same for a concave or convex curvature, the main difference being that the virtual focus of the convex reflector is further away than that of the concave reflector.  But you will probably not get a perfect parabola, would not be pointing it directly at the sun, and wouldn't want the heat/light reflected back toward the sun, anyway.Now, if you were smart and skilled enough to create an off-axis parabolic form, you could direct the focus (or even the gently converging rays) out of the incoming beam, but to benefit from all that effort of creating an off-axis parabola, you would have to have a tracking device to keep it's axis accurately pointed at the sun as the earth rotates.  In fact, now that I think of it, you could not keep the axis pointed at the sun by tracking and simultaneously keep the converging rays directed at your window because the focal point would be moving with the rotation of the reflector.If you are trying to converge the rays at a distance of 30 or 40 feet, the curvature will be extremely slight.  The focal point of a 1 meter parabolic reflector about 8 or 10 inches deep is barely outside of the dish.All of which is to say, parabola schmirabola; hang a reflector up and don't try to concentrate the reflected rays unless you want to get into a really big effort.  Tracking with a flat reflector would be a lot easier.How about just offering to paint the side of your neighbor's house brilliant white?awrightLast edited by awright; 07-13-2006 at 05:45 PM.
Reply:I'll have to read all that a few times, awright.The neighbours house is already white.Might take some photos this weekend of the area.