Datum 2014
Ballast
Bulb
M
ore than 780 million people rely on
kerosene to light their homes. But the
fuel is pricey and is toxic when burned—
not to mention a fire hazard. In 2008,
London-based product designer Martin Riddiford and his
colleague Jim Reeves decided to create a cheap, safe
alternative.
Riddiford knew a falling weight could produce
enough energy to run a grandfather clock, so why not
a light? To find out, he attached the crank of a windup flashlight to a bicycle wheel. He hung a weight from
the wheel to cause it to spin; the wheel cranked the
flashlight, and the device lit up.
Over the next four years, Riddiford, Reeves, and
a small team spent their downtime between projects in
a basement, refining the GravityLight. To use it, a person
hangs the device and fills an attached fabric bag with up
INVENTORS
Jim Reeves, Martin Riddiford
to 28 pounds of rocks, dirt, or other material. Lifting and
releasing the bag steadily pulls a notched belt through
GravityLight’s plastic hub; the belt spins a series of gears
to drive a small motor, which continuously powers an
LED for about 30 minutes.
The team used crowdfunding to manufacture
1,000 GravityLights, which it plans to send to developing
countries for field testing—plus 6,000 more for backers.
“It’s exciting to witness so much positive reaction to what
we’re doing,” Riddiford says. Besides remote villages, the
Gravity
Light
lamp could prove handy in campsites, closets, and any
dark nook far from a socket, so Riddiford also hopes to
license a retail version for less than $10.
A household lamp powered by a bag of
rocks
HOW IT WORKS
COST TO DEVELOP
More than $300,000
R.JAYANTHI
B.Sc CT (G1) - VI
»» As a weighted bag descends, it tugs a belt to turn a series of plastic gears.
»» The gears work in unison to spin an electric motor.
»» The motor powers a small yet bright LED, providing continuous illumination for about 30 minutes—
the maximum amount of time that the bag can take to descend.
»» External connectors can power low-voltage devices, and the entire system is designed to work for
thousands of lift-and-drop cycles.
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