BRIDGE BREAKING BY ELECTRICITY.

Otago Witness, Issue 2978, 12 April 1911, Page 85

BRIDGE BREAKING BY ELECTRICITY.

One of the most ingenious uses to which electricity was ever put w.as in the wrecking of a bridge over the Wabash in Indiana. This bridge had been purchased by the county authorities, who intended to replace it by a steel structure erected on the old pieris and abutments. The owner agreed to remove the bridge in 30 days. The task, proved much greater than had been anticipated, but it was successfully accomplished. Several wreckers, to whom the matter was submitted, declared that it would be impossible within 30 days to pull down the old bridge without injury to the piers. The structure might be blown up with dynamite, but the explosion would also destroy the piers. Were it fired, the heat would crack and injure the masonry of the bridge. The 30 days expired, and an extension of one week "was granted. The owner was at his wits’ end, when be chanced upon an electrician, who proposed, not to blow up the bridge, but to burn it apart. His proposal was gladly accented. Each .span of the bridge was composed of nine chords of three timbers each. The 27 sills were to be cut simultaneously, so that the span would drop between the piers into the river. The cutting was to he accomplished by burning through the wood with loops of iron resistance made red-hot by the passage of the electric current. The job was begun. Fifty-four resistance loops were heated to wreck each span, and the spans were_ wrecked on© at a time. Sufficient current was us©d to heat the iron wires cherry-red. The result was exactly the same with every span. Between the turning on of the current and the fall of the span an hour and 40 minutes elapsed. Then the mass of timbers fell into the water well inside the piers, so that they were uninjured. The cut made by the hot wire was sharp and clean, and the wood w.as not charred more than an inch from the place of fracture. The whole operation (says the Scientific American) took but a few hours. The current was first turned on at about 5 o’clock in the morning, and at 2 in the afternoon the last span crashed down to the riverbed.