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SparkChaser
Premium
join:2000-06-06
Downingtown, PA
kudos:3
Reviews:
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1 recommendation

reply to silbaco

Re: GravityLight: lighting for developing countries.

said by silbaco:

I wonder how long these gravity lights are expected to last under daily usage. 20lbs of weight pulling on plastic gears just doesn't sound like a good combination.

Have you done much work with plastic mechanisms?


shdesigns
Powered By Infinite Improbabilty Drive
Premium
join:2000-12-01
Stone Mountain, GA
reply to SparkChaser

With only 18-30 minutes of use per lift, I wonder how useful they will be.



Jason
Stowage Class Traveler
Premium,Mod
join:2001-01-24
38.2967 Lat
kudos:3

I'd imagine pretty useful.. It wouldn't take more than a few seconds to lift the weight back up to its highest point.

~20 min of light from a few seconds lift.. Not the most convenient, I agree, but certainly useful.
--
When cryptography is outlawed, bayl bhgynjf jvyy unir cevinpl.


lutful
... of ideas
Premium
join:2005-06-16
Ottawa, ON
kudos:1

said by Jason:

~20 min of light from a few seconds lift.. Not the most convenient, I agree, but certainly useful.

potential energy = mass * height * g

let's round off g to 10 m/s2 and use 10 kg (20lbs) lifted to 2m (6ft)
that's only 200 joules stored per lift. If we want 15 minutes run time, max power available for the LED is only about 200mW for almost ideal loss-less scenario. That will be less than 20 lumens which is quite dim.

Since height is limited by ceiling, a lot more weight needs to be lifted to give useful lumens. The generator's permanent magnets could be embedded into a heavy duty molded plastic winch mechanism that could lift 100kg for example.


elios

join:2005-11-15
Springfield, MO
reply to silbaco

said by silbaco:

I wonder how long these gravity lights are expected to last under daily usage. 20lbs of weight pulling on plastic gears just doesn't sound like a good combination.

the gears in my RC helis are plastic and run at MANY 1000s of RPM
as are the gears in some my aircraft servos which hold up to many lbs
i have no issue with the gears being plastic