Page:Popular Science Monthly Volume 92.djvu/231

 Pounding a Building to Pieces

How a huge iron ball was used to demolish a concrete structure

���The iron ball, weighing over half a ton, is suspended on a single fall line. This implement, together with a stiff-leg derrick and a boom is mounted on a convenient movable platform. At right is shown a good sample of the device's handiwork

��POUNDING a reinforced concrete building to pieces with a one- thousand-two-hundred -pound iron ball was the novel method used by a Chicago wrecking company. The build- ing in question was an eight-story struc- ture. It was designed to carry heavy printing machinery, and was unusually strong.

In order to save labor, the wrecking con- cern conceived the idea of using a cast iron ball, weighing ever half a ton. The wrecking outfit, carrying the ball or "skull crusher" on a single fall line, con- sisted of a stiff-leg derrick and forty foot boom, mounted on a sixteen by twenty- four foot platform on rollers which were built for this particular job to facilitate the steering of the platform between the columns of the building.

In wrecking a floor the ball was dropped from a height of about forty feet on the central parts of a slab, until the concrete was shattered up to the column capitals or to the edge of the beams, after which

��the reinforcing bars were cut by means of an oxy-acetylene flame.

The blows of the ball were then directed over the center of the column, where they broke the concrete away from the rods at the base of the columns at the next lower floor for a height of approximately four feet. When as much as possible of the column concrete had been broken off by this method, a wood fire was main- tained around the column base for eight hours. Then water was thrown on the column. This had the effect of cracking the concrete and weakening the column so that when the column reinforcement had been cut with the acetylene torch, a block and tackle attached to the electric hoist easily pulled the standing mass over. Portions of the brick walls not backed by concrete were knocked over by swinging the ball against them. After breaking all but one panel of a floor, the wrecking machine, moving under its own power, on an inclined runway, was lowered to the next floor.

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