In keeping with the philosophy that technology is awesome, but sometimes the most practical solutions don't involve a battery, this project will utilize a falling weight to power a small dynamo that will in turn power LEDs with a sufficient intensity to illuminate a wall sconce appropriate for use as an indoor or outdoor accent light.
A small generator salvaged from a small hand cranked backpacking flashlight.
An off the shelf gearbox used to transfer the energy from a falling weight to the generator
To produce the light to illuminate the wall sconce
To drive the apparatus
Yep, that's right, a fudge-sickle. I need a popsicle stick so must sacrifice my blood sugar for science and consume this fudge-sicke in order to procure the necessary component.
Added a 4" pulley that will act as the drive wheel. I attached this to the 400:1 planetary gear system. This combination should get me pretty close to my target performance. However, after a couple of test spins the high torque involved proved to be a bit too much for the small cotter pin that holds the drive assembly to the central shaft, so need to get myself a new and perhaps sturdier pin before proceeding.
Spent a little time this morning assembling the planetary gear system. The set consists of 2 4:1 segments and 2 5:1 segments. This allows for ratios ranging from 4:1 all the way up to 400:1. Put the full stack together just to verify functionality. It's pretty apparent that 400:1 is going to be way too much. Next step will be to play with the gear ratios to find the sweet spot.
Ok, got sidetracked for a few days building an ultralight backpacking tent. Way cool project... but that's another story. Finally got by the hobby shop today and scored a nice planetary gearbox set. It sports configurable ratios ranging from 4:1 all the way up to 400:1. So... should be able to find the sweet spot in there somewhere.
So.... 350 grams falling 1 meter will power this puppy for around 6 seconds. We'll err on the side of conservatism and call it 5 seconds to make the math easy. That means that if we raise the height to 2 meters we can expect the time to double to 10 seconds. If the weight is increased to 10 kg with 2 meters of travel distance I should expect somewhere in the neighborhood of 5 minutes of illumination per "charge". Not bad.... not great, but not bad.
Looked at the guts of the hand crank backpacking flashlight and hooked up a drive shaft to do some initial measurements. I was able to use a weight of 350 g with a drop of 1 meter to drive the generator for approximately 6 seconds. This gives me the baseline numbers I need to calculate how much time I should be able to run the wall sconce for using a weight of 10 kg and a drop of around 2 meters.