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11

MINING FOCUS

Metals in Planes and Trains

The U.S. currently has a 233,000 mile

network of railroad tracks. Trains are

mostly built out of a variety of steel

alloys, but they also use many other

metals:

• Body panels are of ten made of

aluminum.

• The wiring is made from copper.

•Bushings or bearings are sometimes

made of brass.

• Railway tracks were originally made

from wood, but today they are made of

iron or steel. In particular, high-carbon

steel is extremely durable.

Early airplanes that flew during World

War I were made from wood covered

in canvas. Planes today are usually a

mix of composites such as carbon fiber,

and aluminum alloys, titanium alloys

and steel provide the structure itself.

The airplane structure has to be strong

enough to sustain the force of its own

weight.

An airplane must also be strong enough

to deal with the force from lifting,

dragging, and twisting as the airplane

flies. The strength is in metal spars

covered by a thin metal outer skin. The

wings of an airplane are large, but they

are also light. The metal skin on an

airplane does more than make the wing

stiffer and stronger; it also forces air to

flow aerodynamically around the plane,

directing the air flow until it pushes up

on the wings with enough force to lift

the plane off the ground and into the air.

Landing gear must be extremely strong

and durable, and are built from high-

strength alloys of aluminum, titanium,

or steel.