1018 THE COLLIERY GUARDIAN November 13, 1914 grate area, etc., such as the volume of smokebox, dia- meter of chimney, and distance away from same. By a little experimenting with nozzles of slightly different proportions users can in some instances considerably improve the steaming capabilities of the boiler. The chimney is generally an iron casting somewhat larger in diameter at the top than at the bottom, which is claimed to give a better passage for the gases, and more closely approximate to the escaping cone of steam from the blast pipe, thus aiding the draught. If a built up chimney is fitted a neat cast iron top is all that is required. Ashpan. The object of this is to contain the ash falling through the firebars, and to control the entry of air to the firebox. The firebars should not be too widely spaced, otherwise the fuel falls through before being thoroughly consumed. Yet as air space is necessary (|in. between bars is usual) it is obvious that the fuel should be suitable. Coal dust cannot be consumed economically unless in the form of briquettes. The ashpan should be kept clean, otherwise the damper becomes choked, and the air cannot gain access to the fire. Boiler Clothing. The boiler and firebox are generally insulated by tongued and grooved well-seasoned pine battens covered with steel sheets. Some engineers, however, prefer to have one of the many special coverings instead of wood, such as asbestos mattresses, magnesia sectional lagging, wagons—or the better practice of four spring buffers on each beam. If the curves render it necessary, the spring buffers have large heads or plates riveted to the faces of the buffers on the engine. The more common practice, however, is to have large oak buffer blocks faced with steel plates, which are then capable of deal- ing with a number of different kinds of trucks on the sharpest curves, and the danger of interlocking is. entirely eliminated. For engines which have heavy shunting in such places as steel works, the dead block buffers are somewhat dis- advantageous owing to the severe shocks sustained by the engine frames. A buffer with all the advantages of a spring buffer and block buffer combined, but without the disadvantages of the latter, has recently been fitted to a number of locomotives by Messrs. R. and W. Haw- thorn, Leslie and Company. The buffer portion com- presses spiral springs suitably designed for the work, and having an initial compression. The shock when brought into rapid contact with the wagon buffer is taken up by these springs, and the strain on the framing is in consequence considerably relieved. The draw hooks should be of ample proportions, and fitted with stout volute or spiral springs having an initial compression. Volute springs appear to be more suitable than spiral springs for this purpose, probably owing to the fact that the draw hook works in a slot to enable the draw bar to adjust itself somewhat when the engine is hauling on a curve. provided, as engineers consider that the drivers neglect and maltreat' metallic packings, and prefer the old- fashioned Tuck or asbestos packed glands. There are, however, many cheap, reliable, and efficient metallic, or partly metallic, packings now on the market suitable for such engines. As industrial locomotives are required to run equally well in either direction, the double bar cross head is undoubtedly the better type. These are generally of cast steel, and fitted with renewable gunmetal liners or cast iron shoes. With regard to the respective merits of the latter, there is at present a somewhat divided opinion, some engineers complaining that the gunmetal liners do not wear so well as the cast iron shoes, while others complain of the number of breakages of the latter. This difficulty could, however, be overcome by having east iron liners of the same design as is custo- mary^ in the case of gunmetal; but, of course, they would require to be considerably heavier. Slide bars should be made of hard steel, and not Yorkshire iron case-hardened. The connecting and coupling rods are now generally of mild steel, but they should be of the C quality (32/37 tons tensile). It is advisable to have all bearings hard gunmetal, and adjustable on account of the rapid wear, especially in the case of 4 w.c. locomotives. As, however, adjustable bearings have keys or cotters, the drivers sometimes overtighten them, resulting in heating and excessive wear; therefore some engineers prefer hushes in the coupling rods for 6 w.c. locomotives, Fig. 13.—6-JV.C. Side-tank Engine with Outside Cylinders. Fig. 14.—6-W.C. Side-tank Engine fitted with Walschaert Gear. * Fig. 15.—6-W.C. Side-tank Engine with inside Cylinders. Fig. 16.—6-W.C. Saddle-tank Engine Cut Down in Height. or magnesia cement applied in the form of plaster when the boiler is hot. The author would recommend with good clothing, as is done in the case of asbestos mat- tresses, to have the steel sheets supported on crinolines. Engine Frames. The invariable practice in this country is to have the main frames made from mild steel plates. Some builders specify very thick main frames, and omit cer- tain cross stays, but in the author’s opinion, it is pre- ferable to have somewhat thinner main frames, with an abundance of good transverse stays, thus combining strength with flexibility. In the case of outside cylinder engines, there should be two horizontal and a vertical stay between the cylinders—the horizontal stays being preferably castings, and the vertical a steel plate binding the two and forming a box structure. Of course, in the case of inside cylinder engines the cylinder cast- ing itself forms a most effective stay. In addition to the above, there should be a good stay between the slide bar supports, another just immediately in front of the firebox, and a drag stay, preferably a casting, between the firebox and the buffer beam. Buffers and Draw Gear. There are a great variety of buffer arrangements for industrial engines. When only main line stock is dealt with, and the curves to be negotiated are similar to those met with on main line sidings, etc., it is custo- mary to have ordinary spring buffers fitted. If, in addition to the above, private wagons with a different height and centres of buffers are also to be handled, it is usual to fit dead buffers to take the main line trucks, and spring buffers to engage with those of the private Cylinders and Motion. For this class of engine the cylinders are generally placed outside the frames. As, however, the width over cylinders is the determining factor as regards the extreme width of engine, it may be necessary in rare instances to adopt the inside cylinder type. The cylinders, pistons, and covers should be cast from the best hard, close grained, cylinder metal, and the cylinders after being fitted up should be tested by hydraulic pressure to 2501b. per sq. in. The slide valves should be of somewhat softer material than the cylinders to ensure the former wearing rather than the port faces. With reference to piston packing, recent practice has shown that the rings should neither be too wide nor too thick, as if stiffer than necessary to prevent the steam passing, there is a tendency to cut the barrel, and fric- tion is increased. With a view of further saving the barrel, the rings, after having been first of all turned to a slightly larger diameter, and a section depending or the diameter removed, and the ends brought together, should be re-bored, fixed in a chuck, and again turned on the outside to the same diameter as the cylinder. This method ensures steam tightness and uniformity of spring and wear. Owing to condensation and the consequent danger in allowing water to collect in the cylinders, which would probably result in broken pistons, covers, and slide valves forced from the faces, provision is made for drainage. Plug cocks give least trouble of any of the types, and these are generally arranged to be manipu- lated from the cab. If metallic packings are in proper use, very little wear takes place; but so far only a small proportion of this class of engine have such packings which are also cheaper and easier to renew than adjust- able brasses. The coupling rod knuckle joint has from time to time undergone changes; but the case-hardened pin, working in a renewable hard steel bush, is giving excellent results, and has dispensed with the necessity of case-hardening the coupling rod, and of welding on new rod ends, which at one time had frequently to be done. The question of a suitable material for crank pins has always been a debatable one. Mild steel case-hardened pins have proved most unreliable, wearing badly, and liable to breakages. Hard steel pins wear badly, becoming deeply grooved in a short time; but they are reliable as regards strength, and are worth turning up after grooving. Crank pins turned out of the solid oil- toughened steel bar are everything that can be desired —they wear evenly, last well, and breakages are very rare. Until these proved satisfactory the author had a sneaking regard for Yorkshire iron crank pins, which when properly case-hardened lasted well and gave satis- faction. (To be concluded.) Messrs. Ronald Trist and Co. Limited, the well-known engineering specialists, of Lloyds-avenue, London, E.C., inform us that owing to the splendid co-operation of their numerous clientele they are able to maintain a steady flow of business, and to employ a full working staff. The high efficiency of their three specialities, “ S. E. A. Rings and Daniel’s P. P. P. Engine Packing,” “ The Rubygage Indicator ” and “ The Thermofeed System of Boiler Feed Control,” is perhaps a more significant explanation of the increasing demand for this unique trio.