FALL OF CRANE JIB

Evening Post, Volume CXX, Issue 87, 9 October 1935, Page 12

FALL OF CRANE JIB

INVESTIGATION HELD

CAUSE OF MISHAP

The sudden crash of sf 90-foot crane jib across the busiest part of Lambton Quay on October 3 was the subject of an investigation by the Inspection ot Machinery branch of the Marine Department. The result of the investigation was announced today as follows:—

The accident was due primarily to the breaking of a seven-eighth-inch diameter bolt. The point of fracture was immediately under the head of the bolt where a very fine circumferential crack had evidently existed for some time prior to the complete failure. Tt is r.ot possible to say definitely from a. visual examination of the fracture why the crack should have developed here. It was probably due to some hidden weakness in the material of the bolt caused by improper heating in the forge, or by other improper treatment in manufacture, or the crack may have been started by excessive tightening up of the bolt. .

The bolt was one of a group securing a cast-iron bearing block on which the jib depended for its support. When it broke it permitted one end of the bearing block to come away from its foundation with the result that the unequal load which was then on the bearing caused the bearing to break through the bolt-holes at its opposite end, allowing the jib to fall. The dimensions of the bolt were ample for a. bolt of sound material, but the precaution has now been, taken to fit two bolts where one existed before. Further, the new bearings have .been made of wrought material. There is now a very remote possibility of a repetition of the accident. ■