Heated steel rod expands, raises pointer,breaks pin on cooling.

Heated steel rod expands, raises pointer, breaks pin on cooling. As rod expands, pointer raises up. 1] A long steel rod is heated by multiple flames for a few minutes. The rod expands and pushes up a pointer. When the pointer has risen above the top of the scale, the gas is turned off. A steel pin is inserted through a hole at the tip of the rod, and a knob is tightened firmly so that a lever holds the steel pin in place. Place Plexiglas shield over pin section. 2] The steel rod cools and contracts, and in about 2 minutes the pin will break with a crack. The pieces can fly. When the steel rod is fully expanded, turn heat off. Insert the pin and tighten the knob firmly. Place the plexiglas shield. When the rod contracts, the pin breaks. TEMPERATURE AND EXPANSION.