January 25, 1918. THE COLLIERY GUARDIAN 177 the stress due to the weight of the rope and its inertia. The latter, of course, varies with the size and length of the rope, and in calculating the proper sizes of rope required for hoisting operations, where ropes are often long and heavy, their weight must be considered and added to the ore load, weight of cage and cars, or skip, as the case may be, in order to arrive at any true factor of safety. For short lengths of rope of small diameter, such as used on derricks, etc., this latter calculation is not necessary. Effect of Sheave and Drum Diameters. It is often impracticable to utilise the sizes of sheave and drum recommended by the manufacturer. When different diameters must be used, the bending stresses will vary inversely as the diameters. For instance, assume, in the example given, that a 2 ft. diameter sheave is to be used. The bending stress produced would be 5'58 tons, or about 18j per cent, of the breaking strain of the rope. This in addition to the working load, would be 38f per cent, of the ulti- mate strength of the rope, thus reducing the factor of safety to 2-6. Under these conditions the total work- ing stress would be greater than one-third of the ultimate breaking strength of the rope when new, and this factor of safety is not considered good engineer- ing practice. Obviously under such conditions a wire rope could not possibly give the same service as when operated over the standard or larger-sized sheaves or drums. On the other hand, if we should employ sheaves of twice the diameter of those recommended by the manufacturers, or 96 in., the bending stress would be only 1’4 tons (approximately) or about 41 per cent, of the ultimate strength of tlierope. It is evident that by reducing the bending stress to a minimum, more economical service could be obtained; and in many cases a smaller diameter of rope could be applied to do the required work, thereby increasing the efficiency of the rope and making a considerable saving in first cost. Regarding bending stresses it might be well to describe briefly the effect of these stresses on the initial structure of the metal in the wire rope. It has been shown repeatedly that reverse bends play an important part in the early deterioration of a wire rope. The under-wind rope in which there are reverse bends will invariably give a shorter service than the over-wind rope. The difference in service of the two ropes on a hoist varies a great deal, but from experience it has been observed that the over-wind rope will give 10 per cent, to 25 per cent, more service. Causes of Short Service of Under-Wind Rope. The under-wind (rope as it comes off the head- sheaves has taken somewhat of a set, the permanence of which depends altogether on the relation of rope diameter to sheave diameter. The smaller the sheave, the greater the set. The rope now travels to the take-up drum which is set some distance away and will wind on the drum in the opposite direction to the way it came off the head-sheave. A reverse bend is thus thrown into the rope and consequently into the wires themselves. The rope cannot recover itself in most cases, for the set received at the head-sheave is not entirely overcome before it strikes the take-up drum, and consequently the effect of the latter bend is more severe. Wires removed from ropes retired from service, operating under conditions of reverse bending, show under the microscope that minute cracks have been set up in the steel, sometimes running in planes beween the grains, while in other cases the grains themselves have cracked. Examination made of the steel at different points shows that the nearer the break the more developed are the cracks and fissures. Of course these minute cracks will eventually develop into larger cracks, which will in due course cause the wire to part, and later, if the rope be not removed in time, the breaking of the entire rope. Another cause of failure in wire ropes can be attributed to repeated shocks. A rope may fail because of combined stresses beyond the breaking strain, or on account of a succession of applied loads in excess of the elastic limit, and it may also fail by reason of repeated shocks—that is, loads applied that may reach the elastic limit at intervals of minutes or hours. The effect of these strains, or over-strains as they may be called, is shown best by a microscopic examination of the metal. They lead to crystal- lisation with a consequent embrittlement of the steel. A rope will wind on a drum, coil beside coil successively, until the end of the drum or drum flange is reached. At this point the rope will have to wind upon itself. After making the first coil upon itself there is a tendency for the second coil to mount or ovelap upon the first. This at once readjusts itself by the instability of the position, but the act of slip- ping into place alongside the first coil is accompanied by a sharp snap which always occurs at the same point on the rope. The effect of this is twofold : (1) It will cause jerks that will increase the load on the rope by an amount dependent upon the amount of slack between the drum and the head-sheave. In most cases this is small, but in time the wires will show the effect of these shocks not only from the increased load but also from the vibration in the rope, which usually settles at one point, causing trouble later on. (2) The inner series of wires will crush somewhat from the squeezing between the top and bottom layer and will assume a pear or bell shape. In this dis- turbed condition it is impossible for the inner wires to perform their proper function, and the outer wires will be forced to take more than their share of the stresses. Not only this, but they will also gradually assume the shape of their cushion, the inner series, causing trouble as a result of abrasion. Of course, overlapping cannot be eliminated in most cases on account of the amount of rope that must be taken up on the drum, but the point to emphasise is the fact that frequent inspection must be made of the rope in order to minimise accidents. The effect of overloading has already been referred to, but in addition it might be well to state that wire ropes are constructed to take care of certain loads, and when these loads are exceeded, the steel in the rope must suffer. The rope as made has a certain lay and the method of attachment to the load has a great deal to do with the running out of the lay and stretch of the rope. This should not be confused with the material itself. There are several methods of fasten- ing ropes to the load, by means of either sockets or clips. Fastening by either of these methods can be done in such a manner as to break the rope before the connec- tion gives out. In the case where sockets are used it was formerly thought necessary to turn or bend back the strands or wires into the basket of the socket. This method is now being replaced by a process of opening the wires in the strand of the rope which is to be socketed, thoroughly cleaning them with hydro- chloric acid (cut down with zinc), and pouring in molten zinc. Tests of this method of socketing proved that a more uniform strain on each individual wire can be depended upon. However, it necessitates taking great pains and carries with it at all times the danger of no possible means of inspection. The connection made with clips, if properly applied, is equally strong, and careful inspection can always be made of such a Fig. 1.—Glasgow and South-Western Railway. Fig. 2.—Caledonian Railway. fastening. The latter connection .should be made with the curved section of the U-bolt clip over the short end of the rope. This ensures more safety, as there is then no indentation on the main section of the rope made by the U-bolt. From a safety point of view it is preferable to socketing. All users of wire rope appreciate the value of protecting the rope from mine and other injurious waters which corrode and take into solution the steel of the rope, but it might be well to state that the most dangerous element is often neglected. In mine water the sulphur has been taken into solution, resulting in the formation of sulphuric acid, and when this acid attacks the steel there is liberated hydrogen, which causes a great deal of trouble. In order to keep corrosion at a minimum it is absolutely necessary to cover the rope, or at least fill the interstices of the rope, with some sort of protective preparation. A mineral compound of the right consistency has been found to be the propel’ material to use for this purpose. In dealing with the problems in which wire rope plays an important part, it is most essential that a man be employed who is familiar with the construc- tion of wire rope and its application. This knowledge has resulted in the employment, by most mining companies, of an inspector. The duties of the inspector are too numerous to mention, but the mere fact that there is such a position emphasises the point that wire rope is a part of the equipment that requires expert knowledge, careful handling and the most rigid inspection. In future seamen in the Shipping and Coal Company’s boats will receive a bonus equivalent to a month’s wages for every round voyage from Holland to England and back made without a British convoy, and half that sum for each single crossing without a convoy. Upon this agreement, the men have withdrawn their refusal to sail without a convoy. Lord Rhondda and Miners’ Food.—Replying to a depu- tation from the South Wales Miners’ Federation on Wednes- day, relative to food supplies, Lord Rhondda said he was urging Food Control Committees to take immediate action in rationing schemes. If local authorities wanted more power, let them come to him. He was not prepared to give preference to any class of workers, but in any scheme of rationing all industries involving heavy manual work would get special consideration. In spite of any hard- ships they would be called upon to face, he asked them to remember that they were infinitely better off than those in Germany. He hoped that here we should be able to give the consumer a 50 per cent, higher food value in his rations than was the case in Germany. Mr. Winstone thanked Lord Rhondda for his sympathetic reception of their case. POWERFUL TANK LOCOMOTIVES FOR SCOTTISH RAILWAYS. By F. C. Coleman. Two powerful types of six-wheeled coupled tank loco- motives have recently been introduced by the Glasgow and South-Western and by the Caledonian railway companies, and they are illustrated in the accompany- ing photographs. The engine shown in fig. 1 is one of three which have been specially designed for use on colliery branches, and harbour and dock sidings, with quick curves, worked by the Glasgow and South- Western Railway Company. Each of these three engines is fitted with cylinders 17 in. in diameter by 22 in. stroke. The wheels are 4 ft. 2 in. in diameter, the centre pair being flangeless. The total wheelbase is 10 ft., the total heating surface is 836 sq.ft., the grate area is 17'15 sq. ft., and the working pressure of the boiler is 160 lb. per square inch. The tank carries 1,020 gals, of water, and there is space in the bunkers for 35 cwt. of coal. The engines are all fitted with Walschaert’s valve gear, which operates balanced slide valves of the Richardson type placed on top of the cylinders. The automatic vacuum brake is used, and the boiler is fed by two Davis and Metcalfe’s combina- tion injectors, with Dewrance patent water gauges and protectors. The valve chests are lubricated by a mechanical lubricator of the Eddlewood type, which is moved and controlled from the valve gearing. The locomo- tive has a weight, in running order, of 40 tons. The locomotive shown in fig. 2 is one of 12 six-coupled engines now in service on the Caledonian Railway. The cylinders are 19) in in dia- meter by 22 in. stroke. The leading bogie and also the pair of trailing wheels are each 3 ft. 6 in. in diameter, and the six coupled wheels are 5 ft. 9 in. in diameter. The rigid wheelbase is 13 ft. 3 in., and the total engine wheelbase is 33 ft. 1 in. The total heating surface is 1,716 sq. ft., to which the superheater tubes contribute 539 sq. ft. The working pressure of the boiler is 170 lb. per square inch, the grate area 21-5 sq. ft., and the tractive force, reckoning 80 per cent, of the boilei' pres- sure, 19,486 lb. The cylinders are placed outside the frames, and drive the middle pair of coupled wheels. Superheated steam is distributed to the cylinders by means of piston valves actuated by Stephen- son’s link motion, and the cylinders are fitted with by-pass valves which con- nect both ends of each cylinder. The pistons are fitted with tail rods working through glands in the front covers, to which are attached tubular extension casings, in which the rods move. The superheater snifter valves are situated in a casing behind the chimney, and close automatically when the regulator is opened. In working order, the engine weighs 91 tons 13 cwt., of which 55 tons 1 cwt. are available for adhesion. The tank capacity is 1,800 gals, of water, and there is a fuel space for three tons of coal. Y.M.C.A. Huts.—The total amount of the London Coal Exchange subscription list for the Y.M.C.A. appeal is £4,352, and amounts are still coming in. In a printed leaflet, the president and secretaries of the Institution of Mining Engineers draw attention to the ever-increasing demand for new huts, and the excellent service which these structures fulfil. Subscriptions may be sent to the secre- tary, Institution of Mining Engineers, Albany-buildings, 39, Victoria-street, Westminster. Medals for Miners.—The following awards of the Edward and Albert Medals are announced :—The Edward Medal to Wilby Booth, signalman, and William Jeffells, plane man. Last June, at North Gawber Colliery, Yorkshire, a train of empty tubs ran off the rails, knocking down roof sup- ports and bringing a heavy fall of roof on the tubs. A train of 36 tubs, containing over 100 men, was approaching at six miles an hour. The resource and courage of both men avoided a serious accident, in which many lives must have been lost. Both risked their lives. The Edward Medal to Arthur Morris, timberman at Llanhilleth Colliery, Monmouth. Last March, at great risk, he rescued a tim- berman who was buried to the neck by a fall of roof. The Edward Medal in silver to George Henry Taylor and Thos. Stoke, and the Edward Medal to Thos. James White and Eli Purser, for their gallant rescue work while exposed to the greatest danger on the occasion of a fall of rock at Askern Main Colliery, Yorkshire, last May. Maximum Prices for Iron and Steel.—With reference to the general permit of November 1, 1916, issued by the Minister of Munitions, as subsequently modified, fixing modified prices for, among other things, bar iron and steel, the Minister of Munitions gives notice that, until further notice, the said general permit shall take effect as if under the heading maximum basis prices for bar iron the follow- ing words, namely, “ marked bars, £16 per ton net, f.o.t. makers’ works,” were substituted for the words, “ marked bars, £15 10s. per ton, less 2) per cent., f.o.t. makers’ works.” Until further notice, no extra for tensile quality contained in any list of authorised extras chargeable on steel material for the time being current and issued on behalf of the Minister of Munitions for the purposes of the said general permit as subsequently modified, shall be charged on any sale of steel in shell, discard quality, in addition to the maximum basis prices set out in the said general permit as subsequently modified.