The final plate of this series is Plate R. This is a drawing which is entirely unnecessary from the standpoint of manufacturing the various parts of the machine, but is indispensable to the man who assembles the machine either in the factory or during installation. This drawing is laid out along the same lines as Plate A except that more detail is included and the information given bears in mind especially the assembler. It will be noted that the foundation bolts are shown in this drawing, the location for these bolts being given so that the foundation can be properly constructed and bolts set, even if the machine had not been received.
Another point which is given in detail is the coupling for attaching the machine to the prime mover. It will be noted that the dimensions of this coupling have been given in inches taken from the detail drawing, and also in millimeters. This is necessary since the machine may be for use in a country where the metric system is used, and the manufacturer of the prime mover might be familiar with the metric system only.
Notice that the relative locations of the terminals are shown and that the terminals themselves are marked definitely, "positive", "negative", and "equalizer". A table is also included which shows the proper size cables for the positive, negative, and equalizer leads. In fact, all the information on this drawing is of such a nature that the drawing can be given to the ultimate user of the machine and can be used by him for assembling and setting the machine on its foundation. It will be seen that very few of the smaller details have been shown, such as bolt heads or holding bolts for the field, etc.; that is, these details are unimportant for such a drawing and would require an immense amount of time on the part of the draftsman. Time spent in putting in these details would be a great waste of money and would add nothing to the value of the drawing.
If the student has studied the plates thoroughly, he will see that there is some information which is not given in these drawings. This information, such as the size of wires and number of turns for the shunt fields, is given in the form of specifications. In any electrical device it will be found that some such information cannot conveniently be included in a drawing. It is also true that there must be some sort of master sheet which will connect the many drawings necessary for showing such machinery; that is, the shop specification or summary sheet will be prepared, usually in the form of a table. This may include a list of all the drawings necessary for building the machine and will contain either the specification for such parts of the machine as are not covered on the drawings or a specific reference to another drawing which does contain such specification. In other words, the manufacturer, in placing such a machine in the shop to be built, will give to the shopman such a master sheet or drawing list from which the shop man may determine exactly what detailed information he must obtain in order to produce the machine. The practice in this respect varies considerably with different manufacturers, but practically all of them use some modification of this plan in order to have something which will connect the various drawings and give proper reference for these drawings to the shopman. The plates which have been shown in this work are for the most part of such a nature that they may be developed independently by the student. Some of them may require a considerable knowledge of the principles of electrical design, but it is to be hoped that the most of them will be developed by the students, since such development will give a better idea and a more thorough grasp of the principles involved than anything which can be written. It should be remembered that the drawings included in this set of plates will show only one method of procedure. This method may be modified to some extent in any drafting room and does not represent any fixed scheme. The general principles of line delineation are followed rather closely and the method represented is in use by a large manufacturer and can be considered as practical and successful.