Ans. A gauze brush is made up of a sheet of copper gauze, folded several times, with the wires running in an oblique direction, so as to form a solid flat strip of from ¼ to ½ inch in thickness, increasing with the volume of the current to be collected.
Ques. What is the object of folding the gauze with the wires running in oblique directions?
Ans. It is to prevent the ends of the brush fraying or threading out, which would be the case if the gauze were folded up in any other manner.
Ques. What are the features of gauze brushes?
Ans. They make good contact, but are quite expensive. They may be set either tangentially or radially, the latter preferably, since the point of contact remains the same as the brushes wear away.
Figs. 329 to 332.—Various forms of brush. Fig. 329 gauze brush; fig. 330 laminated or strip brush; fig. 331 strip and wire brush as used on the early Edison machines; fig. 332 carbon brush. Carbon is preferred to copper for brushes on account of the reduction of sparking secured by its use.
Wire Brushes.—This class of brush, which was extensively used before the invention of the gauze brush, is made up of a bundle of brass or copper wires, laid side by side and soldered together at one end. Since wire brushes are harder than the gauze brush, they are more liable to cut or score the commutator, and are also more troublesome to trim.
Laminated or Strip Brushes.—These probably represent the simplest form of brush, but are not extensively used owing to the lack of flexibility. They consist of a number of strips of copper or brass, laid one upon the other and soldered at one end, as in [fig. 330].
