A mechanically powered flashlight is a flashlight
that is powered by electricity generated by
the muscle power of the user, so it does not
need replacement of batteries, or recharging
from an electrical source.
There are several types which use different
operating mechanisms.
They use different motions to generate the
required power; such as squeezing a handle,
winding a crank, or shaking the flashlight
itself.
These flashlights can also be distinguished
by the technique used to store the energy:
a spring, a flywheel, a battery or a capacitor.
Since they are always ready for use, mechanically
powered flashlights are often kept as emergency
lights in case of power outages or other emergencies.
They are also kept at vacation homes, cabins,
and other remote locations because they are
not limited by battery shelf life like ordinary
flashlights.
They are considered a green technology, because
the disposable batteries used by ordinary
flashlights are wasteful in terms of resources
used for the amount of energy produced, and
also contain heavy metals and toxic chemicals
which end up in the environment.
== Dyno torch ==
A 
dyno torch, dynamo torch, or squeeze flashlight
is a flashlight or pocket torch which stores
energy in a flywheel.
The user repeatedly squeezes a handle to spin
a flywheel inside the flashlight, attached
to a small dynamo, supplying electric current
to an incandescent bulb or light-emitting
diode.
The flashlight must be pumped continuously
during use, with the flywheel turning the
generator between squeezes to keep the light
going continuously.
Because electrical power is produced only
when the handle is squeezed, a switch is not
needed.
Dyno torches were issued to soldiers during
World War II, and were popular in Europe during
the war because the electrical power supply
to homes was not very reliable.
A version using a pull-cord was used in World
War I.The photo shows the internal mechanism.
The L-shaped handle has a gear rack, which
spins the white step-up gear, which in turn
spins the flywheel on which is mounted the
dark grey magnet, seen on the lower left.
The magnet induces an electric current in
the red copper winding, seen on the lower
right.
The current from the copper winding flows
through the filament of an incandescent light
bulb (not shown), giving off light.
A spring and ratchet returns the handle to
its original position after each engagement.
== Shake type design ==
The linear induction, Faraday flashlight,
or "shake flashlight" is another type of mechanically
powered flashlight.
It has been sold in the US beginning with
direct marketing campaigns in 2002.
This design contains a linear electrical generator
which charges a supercapacitor emulating the
function of a rechargeable battery when the
flashlight is shaken lengthwise.
The battery or capacitor powers a white LED
lamp.
The linear generator consists of a sliding
rare earth magnet which moves back and forth
through the center of a solenoid (a coil of
copper wire) when it is shaken.
A current is induced in the loops of wire
by Faraday's law of induction each time the
magnet slides through, which charges the capacitor
through a rectifier and other circuitry.
The best designs use a supercapacitor instead
of a rechargeable battery, since these have
a longer working life than a battery.
This, along with the long-life light emitting
diode which does not burn out like an incandescent
bulb, give the flashlight a long lifetime,
making it a useful emergency light.
A disadvantage of many current models is that
the supercapacitor cannot store much energy
in comparison to a lithium-ion cell, limiting
the operating time per charge.
In most designs, vigorously shaking the light
for about 30 seconds may provide up to 5 minutes
of light, though the advertised time omits
the reduced output of the LED after 2 or 3
minutes.
Shaking the unit for 10 to 15 seconds every
2 or 3 minutes as necessary permits the device
to be used continuously.
It is often viewed as a toy, or an emergency
backup for other flashlights.Fraudulent counterfeit
versions of these flashlights have been sold,
most of which incorporate coin-sized non-rechargeable
lithium cells "hidden in plain sight".
The expensive supercapacitor is omitted from
the internal components.
In some of these fake designs, the "magnet"
is not a magnet or the coil is not connected,
and no electricity is generated when the device
is shaken.
These fraudulent flashlights eventually become
useless, since their internal batteries cannot
be recharged or replaced, and the case is
often permanently glued shut.
== Crank-powered design ==
Another common type is the windup or crank-powered
flashlight, with the light powered by a battery
which is recharged by a generator turned by
a hand crank on the flashlight.
One minute of cranking typically provides
about 30 to 60 minutes of light.
It has the advantage that it doesn't have
to be pumped continually during use like the
dyno torch or some shake flashlights.
However it may be less reliable as an emergency
light, because the rechargeable battery it
contains eventually wears out.
The lithium-ion cells used are typically rated
for around 500 charges.
In an alternative "Clockwork Torch" design,
produced by Freeplay Energy, the energy is
mechanically stored in a flat spiral wound
mainspring, rather than a battery.
The owner winds the spring up by turning the
crank.
Then when the light is turned on, the spring
unwinds, turning a generator to provide power
to run the light.
The purpose of this design, originally invented
for use in the developing world, was to improve
its reliability and useful lifetime, by avoiding
or reducing reliance on a battery.
As of 2012, the original design is no longer
made, but updated smaller hand-cranked models
using LEDs are available.
== Other functions ==
Some mechanically powered flashlights include
additional functions and features beyond just
a source of light.
Models sold as emergency lights have additional
functions useful in emergencies, such as flashing
red or yellow lights for roadside emergencies,
sirens, and AM/FM, weather or shortwave radios.
They may also include alternative means of
charging the battery, such as an AC adaptor,
solar cells, or cords that plug into a car
cigarette lighter socket.
Crank powered flashlights often have radios
and other features.
One popular feature is a 5-volt USB charging
port for recharging cell phones when an outlet
is not available.
The quality and long-term reliability of these
devices vary over a wide range, from high-reliability
mil-spec emergency equipment down to one-time-use
non-repairable disposables
== "Steel mills" ==
The first mechanically powered portable illumination
was the "steel mill", used in coal mining
during the 1800s.
These lamps consisted of a steel disk, rotated
at high speed by a crank mechanism.
Pressing a flint against the disk produced
a shower of sparks and dim illumination.
These mills were only used in coal mines,
where a risk of explosive firedamp gas made
candle lighting unsafe.
Caution was required to observe the sparks,
so as not to generate very hot sparks that
could ignite firedamp.
These mills were troublesome to use and were
often worked by a boy, whose only task was
to provide light for a group of miners.
One of the first of these mills was the 18th
century Spedding mill, the Spedding family
having a long association as the agents for
the Lowther family of Westmorland and the
Whitehaven collieries.Steel mills went out
of favor after the introduction of the much
brighter and simpler Davy and Geordie lamps
from 1815.
The mill idea was revived in 1946, based on
the developed technology of cigarette lighters
and ferrocerium flints.
A spring-wound lamp with eight flints was
suggested for emergency signalling at sea.
== See also ==
Human-powered equipment
GravityLight, a mechanically powered and gravity-powered
lamp
