National Geographic : 1940 Feb
OUR MOST VERSATILE VEGETABLE PRODUCT TO THE LAYMAN BUILDING A TIRE IS LIKE A JIG-SAW PUZZLE A workman places the plies for a 4-ply tire, cut on the bias at 45 degrees, on a building drum (upper left). Into a chamber is plunged a headless "barrel" containing all parts of the tire. An air bag has been inserted to force the tire against the mold for vulcanization (upper right). The tire is removed from a watchcase mold (lower left) where, under heat and pressure, it has been "cured" and the tread design formed. Conveyor belts deliver completed tires to inspection tables where each is examined and marked (page 176). These views of stages in tire making were taken in different factories; methods vary greatly in many plants.