A diamond-tipped core drill was suspended from a special bracket fitted to the fly jib of Patterson’s Demag AC 25 city crane. Pitch could be adjusted on the bracket to keep the bore centred when extension sections were added to the drill. Remote control on the crane allowed the crane operator to stand on the roof beside the drill operator, and react immediately to any instructions.
The internal diameter of the chimney was increased from 285mm to 325mm.
