1078 THE COLLIERY GUARDIAN. November 26, 1915. Fig. 5. Fig. «. o. •9' SOME DIFFICULTIES OF DESIGN OF HIGH-SPEED GENERATORS* By Prof. A. B. Field. Progress in the design and manufacture of electrical generating machinery has been recorded, year by year; new types of machinery have made their appearance; new materials, and new applications of existing materials, have been developed; a reduction of weight and size for a given output, and a reduction of manu- facturing costs have been effected; ratings have been standardised, and so on. An illustration of this process of evolution may be found in the development of steam turbo-generators, resulting in a concurrent development of both turbine and generator, with the raising of the speeds of the com- bined sets to the limits corresponding to two-pole and four-pole designs. Simultaneously, the output per machine has been greatly raised, until many sets are now running capable of giving continuously up to 6,250 k.v.a. at 3,600 revolutions per minute, 20,000 k.v.a. at 1,800 revolutions per minute, and higher ratings at 1,500 revolutions per minute (60, 50, and 25 periods). In attaining these results many difficulties have been overcome in as many different ways; and the author describes the experience of one large manufacturing concern in the United States with which he was con- nected. In order to put the matter upon a practical basis, it may be best to take a specific example; and reference will chiefly be made to a 20,000-kw. three-phase machine having the following characteristics Speed, 1,800 revolutions per minute; poles, 4; cycles, 60; kilovolt- amperes, 20,000 at power factors from 1-6 to 0-8; voltage, 13,200; rotor dimensions, 51 in. by 75 in. * From a paper read before the Institution of Electrical Engineers. chain, as shown in section in fig. 8. Provision is made, by means of a worm and worm wheel, for moving the chain jib through 180 degs.; and the haulage rope, as will be seen from fig. 10, is secured to the head of the jib. The over-all height of this machine is 18 in., width 3 ft. 6 in., and length 9 ft. Fig. 11 shows the “ Diamond ” enclosed electrically - driven longwall chain type coal cutter. This is the standard large type machine, and may, of course, be fitted with either a direct-current or alternating-current motor. An unusual type of machine is shown in fig. 12, and serves to exemplify the enterprise and inventiveness of the Diamond Coal Cutter Company. It is a two-motor longwall chain machine, with the jib in the centre, the idea being that the machine would cut in either direc- tion without necessitating turning round. It is similar to the disc machine, with the exception that the disc is replaced by a chain jib. (To be continued.) r.. . r ■ - Fig. 7. Figs. 5, 6 and 7.-—Standard Two-cylinder Compressed-air Driven Disc Coal-cutter. Organisation of British Engineering.—A special committee of the Engineers’ Club have drawn up recommendations, the result of a year’s discussion not only by the committee, but by members of the club, and by many distinguished engineers and men of commerce, in order to organise the British engineering industry. The committee state that they are convinced that the British engineering industry must organise without delay to take advantage of present oppor- tunities, and to meet the conditions which will follow the termination of the war, when our opponents, whose export trade for the moment practically disappeared, will renew with increased fervour their characteristic methods of con- ducting a trade war against our industries. In the opinion of the committee, the development of our engineering export trade, in particular, has been highly unsatisfactory for some years, while Germany’s rate of progress has been phenomenal. Germany’s success has been due to education, to co-operation, and to organisation in manufacturing and selling, backed up by adequate financial support. In Britain, on the other hand, education has been unsystematic, organisation weak, iand co-operation between competing firms almost non-existent. The spirit of conference and co-operation is needed to leaven that British independence which, despite its fine qualities, has hitherto hampered combined action in the interests of the British engineering industry as a whole. The committee feel the urgent need for some voluntary organisation of the whole industry, based upon -a recognition of the interests common to competing firms, and common also to employer and employed; ana they believe that by voluntary organisation and co-operation a great deal can be done. The committee are convinced that advantage can best be taken of the present opportunity by the formation of an association on a non-trading and non-interference-with-prices basis. This association should comprise British manufacturing concerns in all branches of engineering, and have a constitution giving it a legal status framed on broad principles, and possess an efficient and energetic management. Ample funds should be secured from members, mainly in the form of annual subscriptions. The work of the association should be directed by a council through a general manager. Standing committee should be appointed by or elected from the council, including (if thought fit) co-opted members, in order to advise the council in regard to the following departments of the work, namely : General purposes, intelligence, production, inventions and patents, publicity, finance, education and research, Parlia- mentary. Fig. 8. 7 i___________________________________________________________ Fig. 9. Fig. 10. Figs. 8, 9 and 10.—Compressed Air, Four-cylinder, “Diamond" Chain Type, Longwall Coal-cutter.