Lecture by Dr. H. S. Hele-Shaw, F.R.S.
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t_Lyinpia, on Tuesday last, an interesting led en • was given by Dr. EL S. lIele-Shaw, F.R.S., on the subject of " The Connecting and Disconnectingof the Power from the Work." Dr. Hele-Shaw commenced by saying dud he felt quite safe in selecting a subject which might, in a narrower sense, have been called the " Starting and Stopping of Machines," as this would always afford an abundant field for novelty in construction, and the original object of the lectures at the Engineering Exhibition would be certain to be attained under this head. That object was to illustrate and discuss the more novel features ot the exhibits. His only difficulty, that evening, was to make a judicious selection of the material available. He had spent a good deal of time at the various stands, and had found that there was to much of interest that it was not going too far to say that there were a number of separate exhibits there, whicit might, each, have furnished the subject of an evening's
course, and that the complete course of lectures might, profitably, have been limited, as originally intended, to the subject matter of the exhibition itself.
Coming to the subject of the lecture, it was necessary, in the first place, clearly to appreciate the great variety of ways in which power might be transformed. For instance, the power supplied to the present exhibition existed originally in the fuel used in the Davies boiler. The boiler was the agent for transforming the heat of the fuel into the energy of the steam. In turn, the engine became the agent for transferring this into rotary motion. The dynamo was, then, the agent for transforming this once again into electrical energy, which was distributed to the various stands in the exhibitiomi to he used for working tools and machines. The generation of electricity might, and frequently did, take place by means of the energy of water power, instead of by means of a steam engine, in which again the cycle was the same, viz., energy of fluid pressure of motion transformed into mechanical motion of rotation, and thence back into electrical energy. These three successive steps, taken in this order, represented what was, in the majority of cases, the present-day application of power in workshops and manufacture, and what seemed to be developing into the future universal order of things. It, therefore, offered a convenient and natural method of treatment of the subject under the three following heads : (m) Fluids -(a) liquids; Hydraulic valves and sluices : (b) gases; steam and pneumatic valves. (2) Rotary motion by (a) whipping jigs, ratchets, etc.; (b) fast and loose pulleys; (e) clutches. (3) Electricity : Switches, hand and automatic starting rheostats.
It should, of course, be remembered that the application of energy in workshops and factories was only one, although probably the most important, of such applications, but, although the details for instance, in the subject of mechanical locomotion on land or water might appear to be different, the general principles of connecting and disconnecting the power from the work were really the same, and a large number of the appliances used, which he proposed to describe, were practically identical. Dealing first with the general principles, there was ii point of the greatest importance which had always to be borne in mind, and that was the question of inertia. The inertia 'night be that of the working fluid, for instance, the water in the main or pipe leading to the water motor, or what corresponded to the inertia of the electrical current, which made itself evident in the form of the spark on contact being broken. These effects, as would be shown, had to be considered, and provided against, in practice. It was the inertia, however, of the machine to be connected or body to be set in motion, which involved an even more serious consideration. Thus, yhen it fluid, and especially an elastic
fluid, sach as air or gas, was being employed to impart motion, matter was not very important. When, however, a heavy machine was being started from a revolving shaft, or a mass, such as a motor vehicle, was being put in motion, or when the electric current was being used, the type of connecting apparatus, whether it was a mechanical clutch or an electrical switch or starter, should be designed with great care, and here a very remarkable difference occurred and one which could MA ail to strike them very forcibly, if they studied the question. The difference was this, that, owing to the fact that the penalty of any neglect in the design of an electric motor was the immediate destruction of a costly machine by burning out the wires, in the case of a connection by mechanical rotation it was only very occa
sionally that such dire results occurred immediately. The evil effects were, generally, to be found in the injury to the working parts and the rapid deterioration of the whole ma chine. Now and then, of course, a shaft twisted off or sonic part of the overstrained machinery gave way, but that was put down to the carelessness of the man in starting the machine, bad material, or any cause but the right one, it being entirely overlooked that, with an electrical motor, the beautiful design of the starters, switches and various automatic appliances, on which a great amount of ingenuity had been expended, protected the motor from injury due to this cause in a way that until the last few years, engineers, apparently, had never realised. The lecturer then proceeded to deal with various heads of the lecture, commencing with the improvements introduced in connection with valves. Under the head of connecting
and disconnecting mechanical movement there were ingenious appliances, and remarkable progress had been made in
recent years in the construction of friction clutches of all kinds. Friction clutches were rapidly replacing fast and loose pulleys on ordinary shafting in workshops, and there were numbers of instances of interesting clutches in the ex hibition, the more important of which the lecturer proceeded to briefly describe and illustrate. A type of clutch, of which there was only one example in the exhibition, but of which many had been invented in the last few years, was the hydraulic clutch, in which the friction of the liquid through it reduced area was substituted for the rubbing friction of metal surfaces.
Finally, the lecturer dealt with electrical connection and disconnection. He dealt with the principal types of spark arresters and starters, and gave illustrations of several types. He pointed out what a marvellous change was rorning over the organisation of workshops in which, from the mere tentative beginnings of electrical operation, the principle of putting a separate electrical motor for each tool, involving separate connecting and disconnecting appliances, was now coming into vogue. lie drew special attention to
the electrically-driven tools shown by a number of exhibitors, and pointed out that the connecting and disconnect
ing arrangements for these tools were of such an ingenious character that they would well repay a careful study, and illustrate the recent remarkable advance in this direction.
The lecture was illustrated by a number of large working cardboard models, as well as by lantern diagrams, and the lecturer at the conclusion remarked that if there was one lesson more than another to be drawn from this particular ,albject, it was that, no matter how complicated an appliance might be, or how difficult a mechanical problem, so long as it led to an increase of efficiency in a machine, and increased power of dealing rapidly and effectively with work, such an appliance was sure, sooner or later, and, in these days. generally sooner, to come into operation, and that the proof of the necessity as well as the result of technical education was in no subject more clearly seen than in that of the lecture with which he had had the honour to deal.