Pub. 3 2013 Issue 2

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 • Railway tracks were originally made from wood, but today they are made of iron or steel.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. 