DIY!!
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Wonderful, just love all these things made from chewing gum and knicker elastic. Great hands on experiments for kids. Thankyou so much.
old overhead projectors had decent fresnel lenses in them
Oh very cool! I never thought tubing could be used like this, but it gives me a chance to mention something that occured to me earlier. Your earlier video on water-gravity battery had me wondering if you could use a “spiral pump” to load said battery. I’ve made some spiral pumps in the past, and the basic design is quite like your tube-based fresnel lense here. Perhaps the two could be combined in some way. Cheers, thanks for all these really interesting ideas here.
BTW I”m going to put a shout out to you in a game I’m developing here, if you don’t mind. I need a reason to explain why some machinery in still operating in a post-apocalyptic world hundreds of years in the future, and I think what I’ll do is attribute that to a device you invented that is somehow still keeping the lights on in this game despite most-of-humanity’s long-distant demise. I figure I’ll just attribute this device to a user with your initials, and when people dissect the game’s lore someday, they’ll figure it out.
Thanks for the mention for this repeat, and the additional exploration. My “point” of the exercise was a self cooling lens for PV combined with water heating, and perhaps the “bespoke” size from cheap materials.
Would it work with a parabolic backing? I’ve wondered if a convex fresnel lens over a concave, parabolic reflector might make for a very hot focal point combined with a water pre-heater. Cheers!
I’ve seen people use clear plastic bags filled with water ( palm sized ) as fire starters. Concentration of the sun in the palm of your hand as an emergency lens. Seems to work a treat. Can’t get cheaper or easier than that.
Man, I was just drawing this kind of stuff nearly all afternoon. Not for the same reaction, but the spiral has definitely a few uses that aren’t yet very much around. Even tho they are a round.
Robert, I had a lens that was 4 foot by 4 foot years ago from an experimenter who got the lens from a military auction here in the states for real cheap price. What this thing could do was incredible. Made of glass. When I moved the movers dropped the box and it rolled over sideways and became fifty pounds of shards. SO much for the lens.
Another really cool option is to 3D print the optically interesting (jagged) side of the fresnel lense as a negative mold and fill it with clear epoxy resin (molding goes between the epoxy and a table or other level, flat surface). Don’t forget a separator. There are special purpose solutions for this, but some forms of wax or thin sheets of some plastics work well. In the latter case, an adhesive between the plastic sheet and molding and vaccum forming them (one of those vaccum sealing kits for food or filament spools works great) first is a necessary step. A little elbow grease and a soft rag is needed to “polish” it when you’re done. The optical quality of the result of creating a lense this way is astounding.
You could experiment with the tubing to see if it works better as a flat plane or with a parabolic curve in it. This is a very useful tip for me since tubing might be a lot easier to come by than a large Fresnel lens where I live in Brazil.
I am going to borrow a word from the younger generation. Totally AWESOME! The tube lens may not put any factories out of business but it was super fun to watch.