plates, frame stays, horn blocks, driving axleboxes, dome seatings, bogie centres and various brackets and smaller parts.
Iron castings are used for cylinders, the drag-box under the footplate, the chimney, blast-pipe, and regulator-head in the dome, also for certain hornblocks, smaller axleboxes and brackets. Brake cylinders, brake blocks, firebars, sandboxes and on some railways the wheel coverings or “splashers” for goods engines are also of cast iron. This list includes castings of very varying types and qualities of cast iron. For instance, the cylinders are made of the very best close-grained iron of special quality and mixtures, and the greatest care is taken to produce a strong hard material free from any “honeycomb” or other defects, but at the same time the hardness must not be so excessive that they cannot be suitably machined and fitted.
At the other end of the list are the firebars, which are usually made of common scrap, much of which has had to be rejected as unsuitable for other foundry purposes.
It must not, however, be understood that scrap iron castings are inferior as a material. All the best castings such as cylinders contain a percentage of scrap iron varying from 15 to 50 per cent., but this scrap is best selected material, derived from old cylinders and best machine parts. The pig irons used are also selected with a view to the quality of the castings desired, and for cylinders it is usual to mix two different
