THIS SECTIONAL DIAGRAM shows how a propeller is cast. Metal is poured from the ladle B into the runner box A, equipped with a controlling gear comprising a ball D whose vertical movement is actuated by a screw and wheel E. Metal flows through the runners F to the casting.
PLANING MACHINE for machining the surface of propeller blades. This machine at Charlton, Kent, is the only machine of its type in the world. By an ingenious arrangement of gears the cutting tool is moved backwards and forwards across the blades at a predetermined rate, while the table on which the propeller rests is slowly rotated. The rate of rotation is calculated exactly to give the required curve on the blade. The speed of the cutting tool is about 80 feet a minute, and the maximum depth of cut about ¼-
THE BORING MILL for propellers at the Charlton foundry of J Stone and Company Limited, its the largest boring mill of its kind in Great Britain. The machine weighs more than 165 tons, and is built on massive concrete foundations weighing 200 tons. Before boring is done the riser of the newly cast propeller is cut off by a steel saw with a diameter of 6 feet. Arrangements are made to support the riser as the saw cuts through it, to prevent the saw from being nipped during the cutting process. A tapered bore is then accurately machined, and a groove is made in the propeller to take the key which locks it onto the propeller shaft. This boring mill is capable of accommodating propellers which have a diameter of as much as 25 feet, yet all the operations are carried out with the highest degree of precision. An ordinary type of machine lathe would be unsuitable for the work because of the unwieldy shape of the propellers. (Page 666)
Click on the small icon to see a short British Pathé newsreel clip of the Clifton Foundry operated by J Stone and Company Ltd in Kent (1948).
SECTIONAL VIEW OF AN ESCALATOR, showing the way in which the treads are arranged as a continuous chain, the formation of which is changed by the guide rails running beneath the stairway. The riving apparatus is housed in a machine room below the floor near the top of the escalator.