Physics Photo of the Week
April
6, 2007
Antique Engine Flywheels
These are
antique internal combustion engines on "exhibit" at a mining museum in
Jerome, Arizona, southwest of Flagstaff. They had been used in
the mining industry - pumping, lifting, conveyor driving, and other
chores requiring mechanical energy.
The large flywheels and the concentration of mass near the perimeter of
the flywheels illustrates the physics of the photo. Flywheels are
important in any engine to keep
the engine moving during the non-power strokes in the cycle. The
large inertia keeps the engine running in a coasting mode until the
next power stroke adds kinetic energy. With wheels and rotating
objects, the rotational inertia depends on the location of the mass
relative to the axle. The flywheels posess much more rotational
inertia if the most of the mass is distributed on the rim of the
flywheel as opposed to near the axle. The rim of a rotating wheel
moves faster than the parts near the center. By concentrating
most of the flywheel mass near the rim, the wheel possesses much more
rotational inertia than if the mass were concentrated towards the
cneter.
All reciprocating engines
need flywheels - lawnmowers, cars, motorcycles, weed eaters, chainsaws,
etc. In practically all modern engines, the flywheel is enclosed
in a protective housing, so they are not visible as on the antique
engines.
Also notice the hopper on top of the engine. The hopper holds a
reservoir of cooling water. These engines do not generally have a
radiator. The large amount of cooling water as well as continuing
repleshment by the 
operators
precludes the need for radiators and cooling fans.
In the similar antique engine on the right one can also see the
connecting rod that connects the reciprocating piston to the crank
shaft of the flywheel. These connecting rods and crank shafts are
all enclosed in modern reciprocating engines as well. The
enclosures ensure protection to the operators of the equipment as well
as better lubrication, especially at the much higher speeds of modern
engines.
Collectors of antique engines enjoy restoring these machines to working
order. A future Physics Photo of the Week will eventually show
videos of similar engines operating.
Physics
Photo of the
Week is
published weekly during the academic year on Fridays by the Warren
Wilson College Physics
Department. These photos feature an interesting phenomena in
the world around us. Students, faculty, and others are invited to
submit digital (or film) photographs for publication and
explanation. Atmospheric phenomena are especially welcome.
Please send any photos to dcollins@warren-wilson.edu.
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here to see the Physics Photo
of
the Week Archive.
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