Plate XLI.BEAM SHEARING MACHINE.Larger image
Plate XLI.
BEAM SHEARING MACHINE.
Larger image
BEVELLING MACHINE.Larger image
BEVELLING MACHINE.
Larger image
HYDRAULIC JOGGLING MACHINE.Larger image
HYDRAULIC JOGGLING MACHINE.
Larger image
The ironworkers' department is extensive and important. When the material is delivered into the yard, it is discharged from the railway wagons by a 5-ton electric overhead travelling high-speed crane, which stacks the plates and bars in such a way that any piece can be readily removed by the same crane for conveyance to the furnaces.
There are six furnaces suitable for heating shell plates of the largest size, and angles and bars for frames, etc., up to 60 ft. in length. Adjacent to the furnaces are the screeve boards and the frame-bending blocks. The channel, bulb angle, or Z bars, used so extensively now for framing in large ships, are bevelled as they pass from the furnace to the bending blocks. This is done in a special machine made by Messrs. Davis and Primrose, Leith, and illustrated on Plate XLI., adjoining this page. The bars, as delivered from the rolling mills, have flanges at an angle of 90 deg., which is not suitable for taking the skin plating of ships. One angle has therefore to be altered, so that while the inner flange may lie at right angles to the keel-plate, that to the outside will fit closely to the shell plating throughout the entire length of the frame from keel to shear stroke, which may be 50 ft. or 60 ft.
As the bar passes through the machine, the web is carried on an ordinary flat roller, while bevelling rolls, set to the desired angle, work on each side of one of the flanges to give it the desired set. There are several of these machines in use, and they run on rails laid across the front of the furnace, so that the angles, Z sections, or channelsmay be bevelled while passing out of the furnace on to the bending blocks. The manipulation of the plates from the furnace is by means of steam and electric winches.
Formerly, the turning of the frames to the required curvature against the pins on the bending blocks was carried out by hand. To suit the heavier scantlings of the larger ships of the present day, a portable hydraulic machine is now utilised. It is fixed at its base by pins, which fit into the ordinary holes in the blocks, and hydraulic pressure is supplied through a flexible pipe to work the ram-head against the angles, forcing them to take the desired form. The machine is a great labour economiser, as it ensures work on the heaviest of bulb angles being carried out in the minimum of time, and therefore at top heat.
The bars are usually cut to length by a guillotine, but it was considered that this tended to twist the metal, and perhaps unduly fatigue it; and as a consequence the firm have fitted John's shearing and notching machine, as constructed by Messrs. Henry Pels and Co., of Berlin. This new machine is illustrated on Plate XLI., adjoining page 95. The tool is shown in the act of cutting through a channel section. The cutting tool is seen immediately in front of the operator, and is actuated by gearing accommodated within the standards of the machine. When the cutting tool is brought down on the angle or beam to be sheared, and the shaft at the rear started, the rotation of an eccentric actuated by the shaft causes the point of the tool to slide idly a short distance to-and-fro on the bar. The hand lever on the right hand side of the machine is depressed, forcing the tool downwards, and the continued rotation of the eccentric causes the tool to pierce through the bar with a downward and inward motion. Where there is a deep web with flanges, the beam is reversed on the anvil, to enable the other flange to be cut. The cutting of any bar in this machine is a matter of only a few seconds.