Electrical Instrument Making for Amateurs; A Practical Handbook (Paperback)

This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1891 Excerpt: ...the other cord, etc., being affixed thereto. It is usual, though not essential, to place a soft iron keeper at the back of the magnet's poles, which may be partially or wholly removed at will. This enables the operator to regulate somewhat the strength of the shocks by increasing the inductive effect of the magnet on the armature, consequent on the removal of keeper from near its poles. There must also be a hole in the box, to allow of the insertion of the driving-handle, J. 65. The Uni-direction Current Machine.--At 59 we studied the construction of the magneto specially designed for physiological effects. Here we shall direct our attention to one that may be used for heating, lighting, chemical, and electro-magnetic experiments generally. The first thing to be procured or made, as described at 59, is a horse-shoe magnet, having a clear space of 1 in. between the poles, 8 in. long, in. thick, and ii in. wide. This should be capable of lifting at least 10 lb. An armature, or iron core, 3 in. long, - in. diameter, with a channel all round its length, I in. wide, in. deep at the sides, in. deep at the ends, as shown at Fig. 39, must next be made. It may be cast in good malleable iron, and carefully annealed; but it will give better results if cut out of a soft piece of circular wrought-iron rod, which, with a good file and a little patience, may be filed up to the desired shape. Should, however, a casting be preferred, the pattern for the purpose may be cut out of a common broom stick, nicely sand-papered to the desired size, the channel being cut out with a sharp chisel. Whichever plan may be adopted, the armature, previous to winding, must be fitted with two brass or gunmetal heads, wherein the spindle is affixed. For this p...