My sister gave me one of those hand crank flashlights last Xmas and I really love the thing and use it all the time, except it is too big and it takes two hands to crank. I took it apart and found out that most of the volume is taken up by plastic gearing to turn the relatively slow cranking motion into a speedy generator motion because the faster a generator turns, the smaller it can be. All those gears must cause a lot of drag.
So my idea is to use a small spring open bellows to spin a tiny plastic Tesla Turbine or standard turbine generator. The generator is made by replacing the standard center shaft of the turbine with a cylindrical bar magnet with the poles at the sides. Put a tiny coil on each side of the shaft to make AC and feed two LEDs, which will actually flash alternately with the frequency of the AC, but I expect the speed will be so high you won’t notice.
For a really cheap one, you don’t even need a battery that gets charged, just squeeze it for light.
I like the idea of using a Tesla Turbine because the parts are so simple, just a stack of flat disks. Also most of the stuff I have read said that they are efficient but only in low power situations, so I’d think this application would apply.
The design has very few parts, turbine (stack of flat disks and spacers), magnetic shaft, coils, 2 LEDS, splitable turbine housing, two bearings, and a spring opened bellows with one way reed valve for filling.
Add in a battery and maybe weight the turbine a little heavier, switch to three phase for efficiency and it could power small electronics. Replace the bellows by a foam pillow insert in a shoe and hikers/soldiers create their own power in a kind of whoopie cushion way as they walk.-- MisterQED, Jan 11 2008 Hand Crank Flashlight http://www.21st-cen...D&Product_Code=WNGO [MisterQED, Jan 11 2008] Tesla Turbine http://en.wikipedia.../wiki/Tesla_turbine [MisterQED, Jan 11 2008] Why not use the pizeo-electric effect ?-- 8th of 7, Jan 11 2008 Like having tiny hammers attached to the spinning shaft to strike the crystals? How do you create the clicking motion?-- MisterQED, Jan 11 2008 Air creates drag too. Gears and chains are surprisingly efficient. I like this for lateral thinking, but I'm guessing it remains to be seen how it pans out for efficiency. Could be cheaper to manufacture though.-- BunsenHoneydew, Mar 17 2008 Hey, wow, two people read this! Yes, gears can be efficient, but I doubt cheap gears are as efficient. The trade off is between gear drag and the inefficiency of low speed generator and air drag and the efficiency of a high speed generator.-- MisterQED, Mar 17 2008 If you could think of a way to use your entire body weight to compress the air into a small accumulator-tank that then runs the turbine, this would be awesome.
Gears cranked by hand just couldn't stand up to my Incedible Bulk, but compressed air could.
Just step on it a few times. Much better than cranking forever! [+]-- TIB, Apr 18 2008 Easy, put the bag as inserts into shoes and away you go.-- MisterQED, Apr 18 2008 random, halfbakery