The Purchase Department.
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Where to Buy your Supplies.
Steel Castings for Industrial Vehicles.
One of the most imposing exhibits in the accessory section at Olympia was that arranged by the Sheffield Electric Steel Castings Co., Ltd., 56, Cambridge Street, Sheffield, which concern also has establishments at London and Manchester. Realizing that steel castings are entering so largely into the manufacture of industrial vehicles, we made a close inspec tion of the company's exhibits and obtained for readers some very interesting information concerning the manufacture of the productions. The steel is melted in an electric furnace, and, before pouring, each melt is specially tested with the view to always ensuring the production of exceedingly mild and pure steel-castings of a consistent quality day by day. The following results were obtained during recent tests carried out by the company ; they will give an idea of the highly satisfactory nature of the specialquality steel customers obtain : --Tensile strength :35 tons per sq. in., 25 per cent. elongation in 8 ins., and material will bend cold through an angle of 180 degrees. Besides manufacturing all kinds of steel wheels of the hollow and cruciform spoke section, the concern turns out crankcases, steering-boxes, dumb-irons, and a great variety of chassis parts. The company informs us that the excellent installation of Bullard mills enables it to turn out no fewer than 250 complete sets of finished wheels per month ; upon a careful examination of the machined exhibits we found evidence of high precision work and fine finish. The company supplies finished productions to customers' own designs, and employs for the purpose a large staff of patternmakers ; it is also prepared to offer technical advice upon application.
A Reconstruction.
We have been advised that the Electric Ignition Co. (1913), Ltd., is the new title of the Electric Ignition Co., Ltd., Sampson Road North, Birmingham. This well-known concern will continue to manufacture the E.I.C. sparking plugs and other accessories. The company has recently acquired the sole manufacturing and selling rights of the Cox stream-line carburetter. Eccentric or Concentric Piston flings—Which?
Many engineers have, from time to time, advanced the view that the eccentric piston ring, which is in such common use, has serious disadvantages. The pressure upon the walls of the cylinder is not uniform, owing to the unequal thickness, say these theorists. On account of this inequality in material, the upper part of the ring, in particular, suffers at its weakest point from the effect of the explosions, and it so happens that, in a short time, a ring of this type may become loose in its groove. It is necessary that piston rings should furnish a powerful spring action to insure complete gas-tightness in the cylinder, particularly in the near neighbourhood of the slot, which is precisely the weakest point. As the pressure of eccentric rings is not con stant in every part, the cylinder is liable to become worn to an oval shape, a feature to be avoided.
A firm which is a believer in the use of concentric rings is W. J. Bithell and Co., 46, Cannon Street, London, E.C. This company claims that the concentric ring will insure a uniform pressure and bearing surface throughout the whole of its periphery. The construction employed in the rings sold by W. J. Bithell and Co., insures its being uniformly seated in the groove, and it is further claimed that this type of ring presents the same bearing surface and the same resistance to the shock of the explosion throughout. The spring action of this concentric ring can be reduced to a minimum without impairing the gas-tightness, and this is accomplished by a system of patent hammering. In the opinion of some authorities this is an advantage over the old system of removing by slotting a portion of a ring which has been turned to a larger diameter than the cylinder bore.