A PRINCIPLES OF ELECTRICAL DESIGN 



A knowledge of the theory and practice of design, the thorough- 

 ness of which must depend upon the line of work to be ultimately 

 followed, would seem to be of great importance to every engineer. 

 It may not be of great benefit to all men in the matter of forming 

 judgment and developing ingenuity or inventiveness; but it 

 will at least help to bridge the gap between the purely academic 

 and logically argued teachings of the schools, and the methods of 

 the practical engineer, who requires results of commercial value 

 quickly, with sufficient, but not necessarily great, accuracy, and 

 who usually depends more upon his intuition and his quickness 

 of perception, than upon any logical method of reasoning. 



It must not be thought that these remarks tend to belittle or 

 underrate the method of obtaining results through a sequence of 

 logically proven steps; on the contrary, this is the only safe 

 method by which the accuracy of results can be checked, and it is 

 the method which is followed, whenever possible, throughout 

 this book. It is not by the reading of any book that the art of 

 designing can be learned; but only by applying the information 

 gathered from such reading to the diligent working out of 

 numerical examples and problems. 



Although the work done in the drafting room is not necessarily 

 designing, it does not follow that the designer need know nothing 

 about engineering drawing. The art of making neat sketches 

 or clear and accurate drawings of the various parts of a machine, 

 is learnt only by practice; yet every engineer, whatever line of 

 work he may follow, should be able not only to understand and 

 read engineering drawings, but to produce them himself at need. 

 It is particularly important that he should be able to make neat 

 dimensioned sketches of machine parts, because, in addition to 

 the practical value of this accomplishment, it is an indication 

 that he has a clear conception of the actual or imagined thing, 

 and can make his ideas intelligible to others. Clear thinking is 

 absolutely essential to the designer. He must be able to visualize 

 ideas in his own mind before he can impart these ideas to others. 

 Young men seldom realize the importance of learning to think, 

 neither do they know how few of their elders ever exercise their 

 reasoning faculty. The man who can always express himself 

 clearly, either in words or by sketches and drawings, is invariably 

 one whose thoughts are limpid and who can therefore realize a 

 clear mental picture of the thing he describes. The ability to 



